This work was supported by the European Union&#39;s Horizon 2020 research and innovation program under Grant Agreement No. 664732 &#34;nuClock&#34;, by DFG grant Th956/3-1, and by the LMU department of Medical Physics via the Maier-Leibnitz-Laboratory.

Note: Numbers given in the Protocol will reference to Figure 2.
1. Direct Detection of Th-229 Isomeric Decay
<ol>
	<li>Mounting of the 233-uranium source
	<ol>
		<li>Mount the 233-uranium &#945; source (1) through an access flange opening in the gas cell vacuum chamber to the upstream end of the funnel ring electrode system (2) inside the gas cell (3). 
		NOTE: The 290 kBq, 90 mm diameter 233U source was produced via molecular plating onto a titanium-sputtered Si wafer36. In order to achieve optimum &#945; recoil-efficiency of the source, its thickness should not exceed 16 nm, being the stopping range of 84 keV 229Th in uranium.</li>
		<li>Connect the cable to the source mount in order to allow for a DC offset of the source. Close and seal the access flange and connect the external wiring to the 233U source.</li>
	</ol>
	</li>
	<li>Evacuation of the vacuum chamber and bake out
	<ol>
		<li>Start evacuation of the complete vacuum system by starting the roughing vacuum pump (4) if shut down (controlled via a computer-based user interface (5)) and open the three (hand-operated) valves (6) that connect the individual parts of the differential pumping stages to the roughing pump. 
		NOTE: Start opening the valves from chambers downstream of the gas cell with open gate valve (7) towards the turbo molecular pump of the gas cell to create a pressure gradient that prevents potential contaminations from downstream chambers to be sucked into the gas-cell chamber where highest cleanliness is demanded.</li>
		<li>Once the pressures have reached a level in the sub-mbar range (read out via user interface (5)) start the turbo pumps of the gas cell (8), the extraction radio-frequency quadrupole (RFQ) (9) and the quadrupole mass separator (QMS) (10).</li>
		<li>(optional) Open the bypass valve (11) to also allow for efficient evacuation of the gas-supply tubing.</li>
		<li>Continue pumping for a few (4-5) hours until reaching saturation pressure, typically in the range of low 10-7 mbar.</li>
		<li>Start the baking system (12) via the user interface (5) with an upramping (typically 20 &#176;C - 40 &#176;C per hour) heating curve to a maximum of 130 &#176;C.</li>
		<li>Keep baking the vacuum system at 130 &#176;C for 1-2 days until the pressure readings start to decrease.</li>
		<li>Start the cooling sequence of the baking system via the user interface (5) with a downramping sequence, typically 20 &#176;C - 40 &#176;C per hour. 
		NOTE: Cooldown of the system typically requires 8 hours and is performed overnight. Successful preparation of the vacuum system is achieved when the final cell-pressure after cool down ranges below 5x10-10 mbar. The pressures in the RFQ and QMS chamber will be in the 10-9 mbar and 10-8 mbar range, respectively.</li>
		<li>Connect the external wiring to the RFQ vacuum chamber.</li>
	</ol>
	</li>
	<li>Preparation of the gas system and supply of ultra-pure He
	<ol>
		<li>Start the MonoTorr gas-purifier (13) and wait 20 minutes until it has reached its operating temperature.</li>
		<li>Close the bypass valve (11) if open.</li>
		<li>Open the He-gas cylinder (14) (He of 99.9999 % purity is used for operation).</li>
		<li>Open the pressure reducer valve (15) until a pressure of about 0.5 bar is shown.</li>
		<li>Open the valve that connects the pressure reducer to the gas tubing (16).</li>
		<li>Open the gas-flow control (17) until a gas flow of about 1.1 (corresponding to about 5 mbar l/s) is shown.</li>
		<li>Flush the gas tubing for about 10 minutes to remove residual gases from the tubing.</li>
		<li>Close the valve that connects the pressure reducer to the gas tubing (16).</li>
		<li>Wait a few minutes until the He is removed from the gas tubing.</li>
		<li>(optional) For highest purity of the buffer gas, fill the cryo-trap (18) with liquid nitrogen.</li>
		<li>Set the gate valve (7) between the buffer gas cell and its turbo molecular pump to automatic operation and close the valve via the user interface (5).</li>
		<li>Open the valve that connects the pressure reducer to the gas tubing (16). 
		NOTE: The buffer-gas stopping cell is now filled with ca. 30 mbar of He gas. In this way the RFQ and QMS pressures are raised to 10-4 mbar and 10-5 mbar, respectively.</li>
		<li>Adjust the rotary speed of the turbo-molecular pump of the extraction-RFQ vacuum chamber (9) to 50% in order to set an ambient pressure of about 10-2 mbar.</li>
	</ol>
	</li>
	<li>Apply the electric guiding fields for continuous ion extraction
	<ol>
		<li>Apply a DC potential to the 233-uranium &#945; source (1) of 39 V in continuous mode via a customized DC voltage supply (19).</li>
		<li>Apply a DC potential gradient of 4 V/cm (ranging from 35 V to 3 V) via a DC power supply (20) and a voltage offset of 3 V via a 24 channel DC offset supply (21) to the 50-fold segmented funnel ring-electrode system. All voltages are controlled with the computer-based user interface (5).</li>
		<li>Apply a DC potential of typically 2 V to the extraction nozzle electrode (22) with the help of the same computer-based user interface (5).</li>
		<li>Apply a DC potential gradient to the 12-fold segmented extraction-RFQ (27). 
		NOTE: The voltage of each segment can be applied individually with the help of the computer-based user interface (5) via the 24 channel DC offset supply (21). A voltage of 1.8 V is applied to the segment closest to the extraction nozzle. The voltages of the subsequent segments are then stepwise decreased by 0.2 V, resulting in a voltage of 0 V applied to the 10th RFQ segment. This corresponds to a DC gradient of 0.1 V/cm. In case of intended continuous transport of the extracted ions a voltage of 0 V is applied to the 11th and 12th RFQ segments. For this purpose the DC voltage supply of the 12th RFQ segment (23) is left at 0 V and the customized trigger module (24) is set to continuous operational mode.</li>
		<li>Apply RF frequency and amplitude to the funnel ring electrode system via a function generator (25) and linear RF amplifier (26). 
		NOTE: Typical values for frequency and amplitude are 850 kHz and 220 Vpp, respectively. The voltages can be controlled with a computer-based user interface (5). During funnel-RF voltage application, monitor the current of the funnel DC offset supply (21). In case of sparks, which can occur if buffer-gas purity is insufficient, this current will start to increase.</li>
		<li>Apply RF frequency (typically 880 kHz) and amplitude (typically 120-250 Vpp) to the extraction radiofrequency quadrupole (27) (extraction-RFQ) via a frequency generator (28) and two RF amplifiers (29, 30), one for the RFQ and one for the individual bunching electrode. The voltage can be controlled with the computer-based user interface (5).</li>
		<li>Apply a DC potential of -1 V to the exit electrode (31) of the extraction-RFQ via a Mesytec MHV-4 DC voltage supply (32).</li>
		<li>Apply DC offset voltages to the quadrupole mass separator (33) (QMS). The offset voltage of the QMS (center electrode and Brubaker lenses) is chosen to be -2 V via customized DC offset modules (34,35).</li>
		<li>Start the quadrupole mass separator (33) QMS by switching on the QMS function generator (36), the RF amplifier (37) and starting the QMS user-interface (38). In the QMS user interface the mass-over-charge ratio of the selected ion species is inserted (typically 76 u/e or 114.5 u/e, for the extraction of Th3+ or Th2+, respectively). Also the QMS acceptance (typically 1 to 2 u/e) and the RF frequency (typically 825 kHz) is inserted. 
		NOTE: The Labview program will automatically apply and control the RF amplitude and the DC potentials required for ion selection. The required RF amplitudes range from 600 to 1500 Vpp and the DC potentials range from 50 V to 120 V. The DC potentials for mass separation are generated by a customized DC module (39). A feedback-loop is implemented for RF and DC voltage stabilization.</li>
		<li>Apply DC potential to the focusing triodic electrode structure (40) behind the QMS (-2 V/- 62 V/-22 V) via the Mesytec 4 channel (MHV-4) voltage supply module (32).</li>
	</ol>
	</li>
	<li>Probe the ion extraction and tune the QMS
	<ol>
		<li>Apply an attractive surface potential of -1000 V to the front plate of the double-plate (chevron geometry) microchannel-plate detector (41) (MCP) via a high voltage (HV)-module (42).</li>
		<li>Apply a potential of +900 V to the back side of the second MCP plate via a HV-module (43).</li>
		<li>Apply a potential of +5,000 V to the phosphor screen (44) placed behind the MCP detector via a HV-module (45).</li>
		<li>Switch on the CCD camera (46) behind the phosphor screen and configure the exposure parameters of the CCD camera in the corresponding graphical user interface on the data acquisition PC (47). 
		NOTE: The CCD camera is placed in a light-tight housing (48) to cover the detection from ambient light. In case that the extraction is running properly and ions are passing through the QMS a strong signal should be visible on the phosphor screen caused by the ionic impact of the extracted ions. This signal is now monitored by the CCD camera.</li>
		<li>Perform a mass scan to probe the signal shape and accordingly tune the QMS to extract the desired ion species. 
		Note: This is an iterative procedure carried out with the help of the QMS user interface (38). Select a desired mass-over-charge ratio (typically 114.5 u/e for 229Th2+) and the QMS resolving power (typically 1 u/e), then probe the ionic impact signal via the CCD camera. Shift the selected mass in 0.5 u/e steps until a signal is observed. As soon as a signal is observed, probe if also the 233U2+ signal is observable by shifting the mass-over-charge-ratio by 2 u/e to higher masses. If also this signal is observed, probe if the signals can be separated. If this is not the case, adapt the QMS resolving power until the 229Th2+ and 233U2+ signals can clearly be distinguished. Then set the QMS to extract only the 229Th2+ ion species.</li>
	</ol>
	</li>
	<li>Detection of the isomeric decay
	<ol>
		<li>Switch off the QMS pressure sensor (49) via the pressure sensor control unit (50) in order to reduce background from ionized helium and light produced by the sensor.</li>
		<li>Adjust the QMS parameters to extract the Th2+ or Th3+ ion species for isomeric decay detection.</li>
		<li>Reduce the surface potential of the front plate of the MCP detector (41) to -25 V via (42) in order to avoid detecting the signal from electrons originating directly from the ionic impact of impinging ions. In this way a &#39;soft landing&#39; of the 229(m)Th ions on the MCP surface is achieved prior to the isomeric decay.</li>
		<li>Apply an accelerating potential of typically +1,900 V to the second MCP plate for optimum electron amplification via (43).</li>
		<li>Apply an accelerating potential of typically +6,000 V to the phosphor screen placed behind the MCP detector via (45). 
		NOTE: The actually applied voltages will depend on the MCP performance.</li>
		<li>Start the acquisition sequence of CCD images and store the data on disk via the camera user-interface (47).</li>
		<li>Use Matlab programs for image evaluation and post-processing. 
		NOTE: A description of the programs and how they are used can be found in Ref.35 Appendix B.3. Raw data of image frames as well as the programs used for evaluation have been made available online at DOI 10.5281/zenodo.1037981.</li>
	</ol>
	</li>
</ol>
2. Measurement of the 229m Th Half-Life (Re-arrangement of the Setup)
<ol>
	<li>Shut down and venting of the system.
	<ol>
		<li>Power off the high voltages of the MCP detection system (42,43,45), the QMS (37,38), the Funnel system (25,26) and extraction RFQ (28,29,30).</li>
		<li>(Optional) Power off all remaining DC voltages.</li>
		<li>Manually close the He supply system (valves 14 and 16) and wait until the pressure of the buffer-gas stopping cell is reduced to below 2 mbar.</li>
		<li>Open the gate valve that connects the turbo pump to the buffer-gas stopping cell (7) via the user interface (5) and wait until the He is fully removed from the system.</li>
		<li>Close valve (17) of the gas supply line and switch off the gas purifier (13).</li>
		<li>Set the gate valve (7) to manual operation in order to hinder it from closing when the system is vented with dry nitrogen.</li>
		<li>Close the three valves that connect the turbo pumps with the roughing pump (6) and power down the three turbo pumps (8,9,10).</li>
		<li>Switch on the QMS pressure sensor (49).</li>
		<li>Wait until the rotation speed of the turbo pumps is reduced to significantly below 100 Hz as monitored on the user interface (5).</li>
		<li>Fill the dewar (51) with liquid nitrogen and open the venting valve (52) slowly. Wait several minutes until the system is completely vented with dry nitrogen. 
		NOTE: Alternatively, dry nitrogen from a gas cylinder could be used. But in this case, care has to be taken that no overpressure would occur (e.g., by inserting an overpressure valve or rupture disk). The use of air is also an alternative but will lead to slightly longer evacuation times due to the humidity.</li>
		<li>Close the venting valve (52).</li>
	</ol>
	</li>
	<li>Replace the MCP with phosphor screen (41,44) by a small single-anode MCP detector (53)
	<ol>
		<li>Disconnect and remove the CCD camera (46) together with the light-tight housing (48).</li>
		<li>Disconnect the MCP detector with phosphor screen (41,44).</li>
		<li>Open the vacuum flange that connects the MCP and phosphor screen with the vacuum chamber.</li>
		<li>Place the single-anode MCP (53) with a few mm distance behind the exit of the triode extraction system (40) and connect the three wires that connect the front plate (42), back plate (43) and the anode of the MCP (54) with the electric feedthroughs.</li>
		<li>Close the vacuum chamber, the system is now ready for evacuation and bake out.</li>
		<li>Provide the external wiring of the single anode MCP to the HV modules and the read-out system.</li>
	</ol>
	</li>
	<li>Evacuation of the system and bake out
	<ol>
		<li>Evacuate the vacuum system by following the steps 1.2.1 to 1.2.3.</li>
		<li>Follow the bake-out procedure of steps 1.2.4 to 1.2.8.</li>
	</ol>
	</li>
	<li>Preparation of the gas-tubing and supply of ultra-pure He
	<ol>
		<li>Follow the steps 1.3.1 to 1.3.12. 
		NOTE: For bunched mode operation we typically operate the RFQ turbo-pump at 100 % rotation speed, resulting in a pressure in the 10-4 mbar range.</li>
	</ol>
	</li>
	<li>Apply the electric guidance fields for ion bunching
	<ol>
		<li>Apply a DC potential of 69 V to the 233-uranium &#945; source (1) via the customized DC voltage supply (19).</li>
		<li>Apply a DC potential gradient of 4 V/cm (ranging from 65 V to 33 V) via the DC power supply (20) and a voltage offset of 33 V via the 24 channel DC offset supply (21) to the 50-fold segmented funnel ring-electrode system. All voltages are controlled with the computer-based user interface (5).</li>
		<li>Apply a DC potential of 32 V to the extraction nozzle electrode (22) with the help of the same computer-based user interface (5).</li>
		<li>Apply a DC potential gradient to the 12-fold segmented extraction-RFQ. 
		NOTE: The voltage of each segment can be applied individually with the help of the computer-based user interface (5) via the 24 channel DC offset supply (21). A voltage of 31.8 V is applied to the segment closest to the extraction nozzle. The voltages of the subsequent segments are then stepwise decreased by 0.2 V, resulting in a voltage of 30 V applied to the 10th RFQ segment. This corresponds to a DC gradient of 0.1 V/cm. In case of creation of a bunched beam the ions are stored and cooled in the 11th electrode. Therefore, the 11th electrode is set to 25 V and the last RFQ segment is raised to 44 V via the DC voltage supply (23) to accumulate ions in the local potential bucket before releasing the ion bunch by lowering the last electrode segment to 0 V within a microsecond, triggered by a customized trigger module (24).</li>
		<li>Set the trigger module (24) to bunch mode. The trigger module allows an adjustment of the trigger rate and timing. Typically, 10 Hz is chosen as the trigger rate.</li>
		<li>Apply the remaining voltages to the system, following steps 1.4.5 to 1.4.10.</li>
	</ol>
	</li>
	<li>Probe the ion extraction and tune the QMS
	<ol>
		<li>Switch off the QMS pressure sensor (49) via the pressure sensor control unit (50) in order to reduce background from ionized helium and light produced by the sensor.</li>
		<li>Apply an attractive surface potential of -2,000 V to the front plate of the single anode MCP (52) via a HV-module (42).</li>
		<li>Apply a potential of -100 V to the back side of the MCP. The MCP anode is set to ground.</li>
		<li>Switch on the 12 V power supply module (55) for the MCP preamplifier (56). 
		NOTE: Single ions impinging on the MCP detector are now counted with the help of the combination of the preamplifier (56), an amplifier (57) and a constant fraction discriminator (CFD) (58). The CFD signal is send to a data acquisition (DAQ) card of the PC used for QMS control and can be monitored via the QMS user interface (38).</li>
		<li>Perform a mass scan to probe the signal shape and accordingly tune the QMS to extract the desired ion species. 
		NOTE: This is done with the help of the QMS user Interface (38). For this purpose, an initial and a final mass-over-charge ratio is set (e.g., 110 u/e to 120 u/e for the 229Th2+ mass-range), as well as the resolving power (e.g., 1 u/e) and the integration time (5 s) per scan step and the mass scan is started by pressing the scan button. In case that the extraction is running properly and ions are passing the QMS, strong signals of thorium and uranium will be visible caused by the ionic impact of the extracted ions.</li>
	</ol>
	</li>
	<li>Lifetime measurement
	<ol>
		<li>Adjust the QMS parameters to extract the Th2+ or Th3+ ion species for isomeric decay detection.</li>
		<li>Reduce the surface potential of the front plate of the MCP detector (52) to -25 V via (42) in order to reduce the ionic impact signal.</li>
		<li>Apply an accelerating potential of typically +1,900 V to the second MCP plate for optimum electron amplification via (43).</li>
		<li>Apply an accelerating potential of typically +2,100 V to the MCP anode via (53).</li>
		<li>Start the data acquisition via a microchannel scaler (59). 
		NOTE: The preamplifier (56) and the microchannel scaler (59) allow for time resolved read-out of the MCP detector. The ion bunches and the microchannel scaler are both triggered by the trigger module (24). The scaler signal is obtained via a Labview user interface (60). An exponential decay tail of about 10 microseconds lifetime becomes visible after the ion bunches, corresponding to the thorium isomeric decay.</li>
	</ol>
	</li>
</ol>

The authors have nothing to disclose.

The range of recoiling &#945; decay daughter nuclei in uranium amounts to only about 16 nm. In order to achieve a high efficiency of the source for &#945;-recoil ions for a given source activity, it is mandatory to limit the source material thickness to this range. The &#945; recoil extraction efficiency is strongly affected by the cleanliness of the buffer-gas cell. Contaminations of the stopping gas will lead to charge exchange or molecule formation. Therefore, the gas cell itself has to be built according to ultra-high vacuum standards, in particular to allow for a baking of the cell and avoiding any organic materials inside. The stopping gas has to be purified according to technical state-of-the-art, starting from highest-grade gas purity assisted by catalytic purification and delivery to the gas cell via an ultra-clean gas-supply line, partially surrounded by a cryogenic trap to freeze out impurities. In general, careful alignment of the central axis of the complete setup to the position of the gas cell extraction nozzle is essential for achieving a high transport and detection efficiency29.
Step 1.4.5 is the most critical of the protocol. For efficient ion extraction a high RF amplitude has to be applied to the funnel ring electrode. However, if the amplitude is chosen too high, sparks in the gas cell will occur. The maximum achievable RF voltage amplitude depends critically on the purity of the buffer gas. A successful application of voltage is monitored via the current of the funnel offset voltage. This current will increase in the case of sparks. If sparks have occurred, the bake-out procedure has to be repeated in order to guarantee highest ion extraction efficiency.
A further critical point is the application of the high voltages to the MCP detector (steps 1.6.2-1.6.4). Field emissions can occur on the MCP, leading to the emission of electrons which can lead to artefactual signals.
Optimum ion extraction and (cooled and mass purified) transport towards the detection unit requires careful alignment of the central optical axis. The availability of an optical alignment system (alignment laser or theodolite) is essential. The efficient ion transport through the extraction RFQ and the QMS requires a continuous stabilization of the radio-frequency amplitudes for the two opposite phases applied to each opposite pair of rods29. Identification of extraction or transport problems can be facilitated by an ion diagnostic realized e.g., via a multichannel-plate detector placed either consecutively at different positions along the ion path during the commissioning phase of the setup, or alternatively, e.g., under 90o behind the extraction RFQ with a high negative surface voltage (1-2 kV) to attract all extracted ions towards the detector.
During operation typically two problems can arise. Not all voltages are correctly applied. In this case usually no ions are extracted, and one has to find the place of not correctly applied voltage. Also, impurities are present in the helium buffer-gas. In this case the extraction efficiency for triply charged thorium ions will be drastically reduced and molecule formation occurs. In the worst case, even sparks will show up when the funnel voltage is applied. The reason for insufficient gas purity is typically a leakage in the gas supply line or a not properly closed flange of the buffer-gas stopping cell.
The described method to generate a clean beam of ions containing the energetically low-lying 229mTh isomer can be applied to all comparable cases where the ion of interest can be extracted from the buffer-gas atmosphere in sizeable amounts. Cleanliness of the gas-cell and buffer gas is mandatory, thus the amount of remaining gas impurities is a limitation to the sensitivity of the method. While the employed microchannel-plate detector (MCP) is based on the detection of electrons, as exploited here for the registration of low-energy conversion electrons, this case already lies at the low-energy border of the efficiency curve for MCPs38, while for higher energies the method would significantly gain in detection efficiency.
So far, the described method has provided the only reported direct and unambiguous identification of the de-excitation of the thorium isomer. Alternatively, vacuum ultra-violet (VUV)-transparent crystals (with large bandgaps, exceeding the assumed excitation energy of the isomer) are doped with 229Th. The goal is to place 229Th ions in high (4+) charge state of crystal lattice positions, inhibit de-excitation by the large band gap and aim at an excitation of the isomer using X- rays from synchrotron light sources. Despite the elegant concept of this approach, so far no VUV fluorescence could be observed in a series of experiments reported by several groups worldwide39,40,41,42,43. The same holds for a class of experiments that aims to realize the nuclear excitation of the isomer via the electron shell of 229Th, using a so-called electron-bridge transition. Here a resonant coupling between an electron shell transition and the nuclear isomer should allow for a more efficient isomer population44,45. Other experiments that aim for the investigation of the isomeric properties are based on microcalorimetry46 or the observation of the hyperfine-shift in the atomic shell47. Very recently another method to excite the isomer in a laser-induced plasma was reported48 and is subject to scientific discussion within the community.
The discovery of the internal conversion decay channel of the thorium isomer11 and the determination of the corresponding half-life of neutral 229mTh (7(1) &#956;s)12 can be exploited in the future to realize a first all-optical excitation with a pulsed, tunable VUV laser based on already existing technology. Thus the present paradigm that this would require much better knowledge of the excitation energy and a corresponding customized laser development can be circumvented. In contrast, exploiting the knowledge of internal conversion electron emission, gating the detection of conversion electrons with the laser pulse will provide a high signal-to-background ratio, while allowing for a scan of 1 eV of excitation energy in less than 3 days49.Moreover, a determination of the excitation energy of the isomer, still being work in progress, can be based on the described method of generating the 229mTh beam by sending IC decay electrons into a magnetic-bottle electron spectrometer with retarding field electrode grids50. The same technique will also allow to determine the isomeric lifetime for different chemical environments (e.g., on large band-gap materials like CaF2 or frozen argon) or in 229Th+ as well as in the free, neutral atom.
The described method of generating an isotopically pure thorium ion beam of 3+ charge state can be used as a tool to provide thorium ions for future laser-spectroscopy experiments. In this case the ion beam can be used to load a Paul trap in a stable and efficient way. So far, the only alternative method is to produce 229Th3+ by laser ablation from a solid target. This, however, requires high laser intensities and a large quantity of 229Th, which is an expensive radioactive material and leads to the contamination of used vacuum components. For this reason, the described method can be of significant advantage when it comes to nuclear laser spectroscopy experiments. A first application of this type has already been published51.

The first excited metastable state in the thorium-229 nucleus, denoted as 229mTh, exhibits a special position in the nuclear landscape, as it possesses the lowest nuclear excitation energy of all presently known ca. 176,000 nuclear excited states. While typical nuclear energies range from keV up to the MeV region, 229mTh possesses an energy of below 10 eV above the nuclear ground state1,2,3. The currently most accepted energy value for this state is 7.8(5) eV4,5. This low energy value has triggered interest from different physical communities and led to the proposal of several interesting applications. Among them are a nuclear laser6, a highly stable qubit for quantum computing7 and a nuclear clock8,9.
The reason that 229mTh is expected to offer a broad variety of applications is based on the fact that, due to its extraordinary low energy, it is the only nuclear state that could allow for direct nuclear laser excitation using currently available laser technology. So far, however, direct nuclear laser excitation of 229mTh was prevented by insufficient knowledge of the metastable state&#39;s parameters like its precise energy and lifetime. Although the existence of a nuclear excited state of low energy in 229Th was already conjectured in 197610, all knowledge about this state could only be inferred from indirect measurements, not allowing for a precise determination of its decay parameters. This situation has changed since 2016, when the first direct detection of the 229mTh decay opened the door for a multitude of measurements aiming to pin down the excited state&#39;s parameters11,12. Here, a detailed protocol is provided, which describes the individual steps required for a direct detection of 229mTh as achieved in the experiment of 2016. This direct detection provides the basis for a precise determination of the 229mTh energy and lifetime and therefore for the development of a nuclear clock. In the following the concept of a nuclear clock as the most important application for 229mTh will be discussed.
With a relative linewidth of &#916;E/E~10-20 the ground-state transition of the thorium isomer potentially qualifies as a nuclear frequency standard (&#39;nuclear clock&#39;)8,9. Due to an atomic nucleus about 5 orders of magnitude smaller compared to the atomic shell, the nuclear moments (magnetic dipole and electric quadrupole) are accordingly smaller than the ones in atoms, rendering a nuclear clock largely immune against external perturbations (compared to the present state-of-the-art atomic clocks). Therefore, a nuclear frequency standard promises a highly stable and accurate clock operation. Although the accuracy achieved in the best present atomic clocks reaches about 2.1x10-18 13, corresponding to a deviation of 1 second in a time period considerably longer than the age of the universe, nuclear clocks hold the potential of a further improvement which could become essential for a vast field of applications. Satellite-based navigational systems like the Global Positioning System (GPS), Global Navigation Satellite System (GLONASS) or Galileo presently operate with a positioning precision of a few meters. If this could be improved to the centimeter or even millimeter scale, a plethora of applications could be envisaged, from autonomous driving to freight or component tracking. Besides highly accurate clocks, such systems would require reliable uninterrupted operation, with long-term drift stability that secures long-resynchronization intervals. The use of nuclear clocks could turn out beneficial from this practical point of view. Further practical applications of (synchronized networks of) nuclear clocks could lie in the field of relativistic geodesy14, where the clock acts as a 3D gravity sensor, relating local gravitational potential differences &#916;U to measured (relative) clock frequency differences &#916;f/f via the relation &#916;f/f=-&#916;U/c2 (c denoting the speed of light). The best present clocks are capable of sensing gravitational shifts from height differences of about &#177;2 cm. Thus, ultra-precise measurements using a nuclear clock network could be used to monitor the dynamics of volcanic magma chambers or tectonic plate movements15. Moreover, the use of such clock networks was proposed as a tool to search for the theoretically described class of topological dark matter16. Extensive discussion can be found in the literature on the application of a 229mTh-based nuclear clock in the quest for the detection of potential temporal variations of fundamental constants like the fine structure constant &#945; or the strong interaction parameter (mq/&#916;QCD, with mq representing the quark mass and &#916;QCD the scale parameter of the strong interaction), suggested in some theories unifying gravity with other interactions17. The detection of a temporal variation in the ground-state transition energy of 229mTh may provide an enhanced sensitivity by about 2-5 orders of magnitude for temporal variations of the fine structure constant or the strong interaction parameter18,19,20,21,22,23,24,25,26. The current experimental limit for such a variation of &#945;&#160;amounts to (d&#945;/dt)/&#945;=-0.7(2.1)10-17/yr27. In the following the experimental approach for the direct detection of the 229mTh ground-state decay will be described.
Evidence for the existence of the 229-thorium isomer until recently could only be inferred from indirect measurements, suggesting an excitation energy of 7.8(5) eV (equivalent to a wavelength in the vacuum ultra-violet spectral range of 160(11) nm)4,5. Our experimental approach, aiming at a direct identification of the isomeric ground-state deexcitation of the 229mTh isomer, builds on a spatial separation of the isomer population in a buffer-gas stopping cell, followed by an extraction, and mass-separated transport towards a suitable detection unit to register the deexcitation products28,29. Thus population and deexcitation of the isomer can be disentangled, resulting in a clean measurement environment, unaffected by prompt background contributions. Population of the isomer is achieved via the &#945; decay from a radioactive 233U source, where a 2% decay branch proceeds not directly to the ground state of 229Th, but populates the isomeric first excited state instead. &#945;-decay recoil nuclei are thermalized in an ultra-pure helium atmosphere of a buffer-gas stopping cell, before being guided by electric radiofrequency (RF) and direct current (DC) fields towards an extraction nozzle, where the emerging supersonic gas jet drags them into an adjacent vacuum chamber, housing a (segmented) radiofrequency quadrupole (RFQ) structure acting as ion guide, phase-space cooler and potentially also as linear Paul trap for bunching the extracted ions. For a detailed description of the buffer-gas stopping cell and extraction RFQ see Refs.30,31,32. Since up to that moment the extracted ion beam contains in addition to 229(m)Th also the chain of &#945; decay daughter products, mass separation is performed using a quadrupole mass separator (QMS) in a subsequent vacuum chamber to finally generate an isotopically pure 229(m)Th beam in selectable charge states (q=1-3). A detailed description of the QMS can be found in Refs.33,34. Detection of the isomeric decay was achieved by impinging the Th ions directly on the surface of a microchannel-plate detector (MCP), where electrons are liberated, accelerated towards a phosphor screen and viewed by a charge-coupled device (CCD) camera. An overview of the experimental setup is shown in Figure 1. A detailed description is given in Ref.35.
<img alt="Figure 1" class="xfigimg" src="/files/ftp_upload/58516/58516fig1.jpg" /> 
Figure 1: Overview of the experimental setup. The thorium-229 isomer is populated via the 2% decay branch in the &#945; decay of uranium-233. 229mTh ions, leaving the 233U source due to their kinetic recoil energy, are thermalized in a buffer-gas stopping cell filled with 30 mbar helium gas. The ions are extracted from the stopping volume with the help for RF and DC fields and a low-energy ion beam is formed with the help of a radio-frequency quadrupole (RFQ). The ion beam is mass-purified with the help of a quadrupole-mass-separator (QMS) and the ions are softly implanted into the surface of a micro-channel-plate (MCP) detector combined with a phosphor screen which allows for spatially resolved detection of any occurring signals. With kind permission of Springer Research, this figure has been modified from11. <a href="https://www-jove-com.remotexs.ntu.edu.sg/files/ftp_upload/58516/58516fig1large.jpg" target="_blank">Please click here to view a larger version of this figure.</a>
The following protocol describes the underlying procedure to generate the 229(m)Th ion beam that enabled the first direct detection of the ground-state decay of the thorium isomer, thus laying the foundation for studying its decay properties as a prerequisite of the ultimately envisaged all-optical control of this exotic nuclear state towards its application as an ultra-precise nuclear frequency standard. For better orientation a schematic overview of the setup used for direct detection of the isomeric decay11 is provided in Figure 2, containing a numerical labelling of the components addressed in the following protocol. Also the components used for lifetime determination12 are contained as an inset.
<img alt="Figure 2" class="xfigimg" src="/files/ftp_upload/58516/58516fig2.jpg" /> 
Figure 2: Schematic sketch of the experimental setup used for isomeric decay detection. The components used for lifetime measurement are shown as an inset. Individual components that will be referenced in the protocol section are numerically labelled. <a href="https://www-jove-com.remotexs.ntu.edu.sg/files/ftp_upload/58516/58516fig2large.jpg" target="_blank">Please click here to view a larger version of this figure.</a>

<table border="0" cellpadding="0" cellspacing="0" style="width:859px;" width="858">
	<tbody>
		<tr height="62">
			<td height="62" style="height:62px;width:223px;">Uranium-233 Source</td>
			<td style="width:153px;">Institut f&#252;r Radiochemie Universit&#228;t Mainz</td>
			<td style="width:125px;">customized</td>
			<td style="width:357px;">290 kBq U-233 deposited onto 90 mm diameter</td>
		</tr>
		<tr height="62">
			<td height="62" style="height:62px;width:223px;">RF funnel</td>
			<td style="width:153px;">Secamus Laserschneidtechnik GmbH</td>
			<td style="width:125px;">customized</td>
			<td>50 ring electrodes, laser cut and electropolished</td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:223px;">Buffer-gas stopping cell</td>
			<td style="width:153px;">Workshop of LMU Munich</td>
			<td style="width:125px;">customized</td>
			<td>Vacuuchamber DN200 CF for buffer-gas stopping cell</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:223px;">Roughing pump</td>
			<td style="width:153px;">Leybold</td>
			<td style="width:125px;">Screwline SP 250</td>
			<td>Roughing pump for entire system</td>
		</tr>
		<tr height="18">
			<td height="18" style="height:19px;width:223px;">Roughing pump control</td>
			<td style="width:153px;">Siemens</td>
			<td style="width:125px;">Micromaster 420</td>
			<td>Control unit for Screwline SP 250</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:223px;">Vacuum gauge Prepressure</td>
			<td style="width:153px;">Pfeiffer</td>
			<td style="width:125px;">TPR 265</td>
			<td>Pressure control for roughing pump</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:223px;">Vacuum gauge cell 1</td>
			<td style="width:153px;">Pfeiffer</td>
			<td style="width:125px;">CMR 261</td>
			<td>Pressure control for cell (high-pressure range)</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:223px;">Vacuum gauge cell 2</td>
			<td style="width:153px;">Pfeiffer</td>
			<td style="width:125px;">PBR 260</td>
			<td>Pressure control for cell (low-pressure range)</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:223px;">Vacuum gauge RFQ</td>
			<td style="width:153px;">Pfeiffer</td>
			<td style="width:125px;">PKR 261</td>
			<td>Pressure control for RFQ pressure read-out</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:223px;">Pressure gauge QMS</td>
			<td style="width:153px;">Pfeiffer</td>
			<td style="width:125px;">PKR 261</td>
			<td>Pressure control for QMS pressure read-out</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:223px;">Pressure control unit</td>
			<td style="width:153px;">Pfeiffer</td>
			<td style="width:125px;">TPG 256 A</td>
			<td>Control unit for all pressure gauges</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:223px;">Control PC 1</td>
			<td style="width:153px;">Fujitsu</td>
			<td style="width:125px;">unknown</td>
			<td>Control computer for buffer-gas stopping cell</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:223px;">Simatic with CPU</td>
			<td style="width:153px;">Siemens</td>
			<td style="width:125px;">S7-300</td>
			<td>Simatic for automation and control</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:223px;">Simatic without CPU</td>
			<td style="width:153px;">Siemens</td>
			<td style="width:125px;">ET 200M</td>
			<td>Simatic for automation and control</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:223px;">Vacuum valves</td>
			<td style="width:153px;">SMC</td>
			<td style="width:125px;">XLH-40</td>
			<td>Vacuum valves for evacuation control</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:223px;">UHV gate valve</td>
			<td style="width:153px;">VAT</td>
			<td style="width:125px;">48240-CE74</td>
			<td>Gate valve for cell closing during operation</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:223px;">Turbo-Molecular pump 1</td>
			<td style="width:153px;">Pfeiffer</td>
			<td style="width:125px;">TMU 400M</td>
			<td>Turbo pump for cell</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:223px;">Control unit for TMP 1</td>
			<td style="width:153px;">Pfeiffer</td>
			<td style="width:125px;">TCM 1601</td>
			<td>Control unit for TMP TMU 400M</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:223px;">Turbo-Molecular pump 2</td>
			<td style="width:153px;">Pfeiffer</td>
			<td style="width:125px;">HiMag 2400</td>
			<td>Trubo pump for RFQ</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:223px;">Turbo-Molecular pump 3</td>
			<td style="width:153px;">Edwards</td>
			<td style="width:125px;">STP 603</td>
			<td>Trubo pump for QMS</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:223px;">Control unit for TMP 3</td>
			<td style="width:153px;">Edwards</td>
			<td style="width:125px;">SCU-800</td>
			<td>Control unit for TMP Edwards STP 603</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:223px;">Bypass valve of gas tubing</td>
			<td style="width:153px;">Swagelok</td>
			<td style="width:125px;">SS-6BG-MM</td>
			<td>Valve to bypass the mass-flow controller</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:223px;">Heating sleeves</td>
			<td style="width:153px;">Isopad</td>
			<td style="width:125px;">customized</td>
			<td>Heating sleeves for bake out of cell and RFQ</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:223px;">Temperature sensors</td>
			<td style="width:153px;">Isopad</td>
			<td style="width:125px;">TAI/NM NiCrNi</td>
			<td>Temperature sensors for bake-out system</td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:223px;">Heating control unit</td>
			<td style="width:153px;">Electronic workshop of LMU Munich</td>
			<td style="width:125px;">customized</td>
			<td>Control unit for Isopad heating sleeves</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:223px;">Catalytic gas purifier</td>
			<td style="width:153px;">SAES MonoTorr</td>
			<td style="width:125px;">PS4-MT3-R-2</td>
			<td>Gas purifier for ultra-pure helium supply</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:223px;">He gas cylinder</td>
			<td style="width:153px;">Air Liquide</td>
			<td style="width:125px;">He 6.0, 50 liters</td>
			<td>Helium of 99.9999 % purity</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:223px;">Pressure reducer</td>
			<td style="width:153px;">Druva</td>
			<td style="width:125px;">FMD 502-16</td>
			<td>Pressure reducer for He gas cylinder</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:223px;">Valve of gas supply</td>
			<td style="width:153px;">Swagelok</td>
			<td style="width:125px;">SS-6BG-MM</td>
			<td>Valve to open or close the gas supply</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:223px;">Mass flow control</td>
			<td style="width:153px;">AERA</td>
			<td style="width:125px;">FC-780CHT</td>
			<td>Mass flow control valve for He supply</td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:223px;">control unit for mass flow valve</td>
			<td style="width:153px;">Electronic workshop of LMU Munich</td>
			<td style="width:125px;">customized</td>
			<td>Control unit for AERA mass flow control</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:223px;">Gas tubing</td>
			<td style="width:153px;">Dockweiler</td>
			<td style="width:125px;">Ultron</td>
			<td>electropolished gas tubing for He supply</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:223px;">Cryogenic trap</td>
			<td style="width:153px;">Isotherm</td>
			<td style="width:125px;">unknown</td>
			<td>cryogenic trap for He purification (optional)</td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:223px;">DC voltage supply for source</td>
			<td style="width:153px;">Electronic workshop of LMU Munich</td>
			<td style="width:125px;">customized</td>
			<td>DC offset voltage supply for U-233 source</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:223px;">DC voltage supply for funnel</td>
			<td style="width:153px;">Heinzinger</td>
			<td style="width:125px;">LNG 350-6</td>
			<td>Power supply for DC gradient of funnel</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:223px;">DC voltage supply for RFQ</td>
			<td style="width:153px;">Iseg</td>
			<td style="width:125px;">unknown</td>
			<td>DC voltage supply for funnel offset, nozzle and RFQ</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:223px;">Laval nozzle</td>
			<td style="width:153px;">Friatec AG</td>
			<td style="width:125px;">customized</td>
			<td>Laval nozzle for He and ion extraction</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:223px;">DC voltage supply for buncher</td>
			<td style="width:153px;">Heinzinger</td>
			<td style="width:125px;">LNG 350-6</td>
			<td>DC supply for bunching electrode</td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:223px;">Trigger module</td>
			<td style="width:153px;">Electronic workshop of LMU Munich</td>
			<td style="width:125px;">customized</td>
			<td>Trigger module for bunched operation</td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:223px;">RF generator for funnel</td>
			<td style="width:153px;">Stanford Research Systems</td>
			<td style="width:125px;">SRS DS 345</td>
			<td>RF generator for funnel</td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:223px;">RF amplifier for funnel</td>
			<td style="width:153px;">Electronic Navigation Industries</td>
			<td style="width:125px;">ENI 240L-1301</td>
			<td>Rf amplifier for funnel</td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:223px;">RF phase divider for funnel</td>
			<td style="width:153px;">Electronic workshop of LMU Munich</td>
			<td style="width:125px;">customized</td>
			<td>RF phase divider for funnel</td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:223px;">RF+DC&#160; mixer for funnel</td>
			<td style="width:153px;">Electronic workshop of LMU Munich</td>
			<td style="width:125px;">customized</td>
			<td>Voltage divider and RF+DC mixer for funnel voltage</td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:223px;">Extraction RFQ</td>
			<td style="width:153px;">Workshop of LMU Munich</td>
			<td style="width:125px;">customized</td>
			<td>Extraction RFQ for ion-beam formation or storage</td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:223px;">RF generator for RFQ</td>
			<td style="width:153px;">Stanford Research Systems</td>
			<td style="width:125px;">SRS DS 345</td>
			<td>RF generator for RFQ</td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:223px;">RF amplifier for RFQ</td>
			<td style="width:153px;">Electronic workshop of LMU Munich</td>
			<td style="width:125px;">customized</td>
			<td>RF amplifier for RFQ</td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:223px;">RF amplifier for bunch electrode</td>
			<td style="width:153px;">Electronic workshop of LMU Munich</td>
			<td style="width:125px;">customized</td>
			<td>RF amplifier for bunch electrode</td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:223px;">RF+DC mixer for RFQ</td>
			<td style="width:153px;">Electronic workshop of LMU Munich</td>
			<td style="width:125px;">customized</td>
			<td>Mixes the RF and DC potentials for RFQ voltage</td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:223px;">RFQ exit electrode</td>
			<td style="width:153px;">Workshop of LMU Munich</td>
			<td style="width:125px;">customized</td>
			<td>2-mm diameter exit aperture for differential pumping</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:223px;">4 Channel DC supply</td>
			<td style="width:153px;">Mesytec</td>
			<td style="width:125px;">MHV 4</td>
			<td>DC offset for aperture and triode</td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:223px;">QMS</td>
			<td style="width:153px;">Workshop of LMU Munich</td>
			<td style="width:125px;">customized</td>
			<td>Quadrupole mass separator for m/q selection</td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:223px;">Brubaker DC offset module</td>
			<td style="width:153px;">Electronic workshop of LMU Munich</td>
			<td style="width:125px;">customized</td>
			<td>DC offset supply for Brubaker lenses of QMS</td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:223px;">QMS DC offset module</td>
			<td style="width:153px;">Electronic workshop of LMU Munich</td>
			<td style="width:125px;">customized</td>
			<td>DC offset supply for QMS</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:223px;">USB-to-Analog converter</td>
			<td style="width:153px;">EA Elektro-Automatik</td>
			<td style="width:125px;">UTA12</td>
			<td>to generate signal for QMS HV shifter</td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:223px;">QMS HV shifter</td>
			<td style="width:153px;">Electronic workshop of LMU Munich</td>
			<td style="width:125px;">customized</td>
			<td>to shift the voltage of the QMS DC module</td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:223px;">QMS DC module</td>
			<td style="width:153px;">Electronic workshop of LMU Munich</td>
			<td style="width:125px;">customized</td>
			<td>Module to provide DC voltages for QMS</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:223px;">RF generator for QMS</td>
			<td style="width:153px;">Tektronix</td>
			<td style="width:125px;">AFG 3022B</td>
			<td>RF generator for QMS</td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:223px;">RF amplifier for QMS</td>
			<td style="width:153px;">Electronic workshop of LMU Munich</td>
			<td style="width:125px;">customized</td>
			<td>RF amplifier for QMS</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:223px;">Picoscope</td>
			<td style="width:153px;">Pico Technology</td>
			<td style="width:125px;">Picoscope 4227</td>
			<td>Oscilloscope for QMS RF control</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:223px;">Control PC 2</td>
			<td style="width:153px;">Fujitsu</td>
			<td style="width:125px;">Esprimo P900</td>
			<td>Control computer for QMS</td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:223px;">Triode extraction system</td>
			<td style="width:153px;">Workshop of LMU Munich</td>
			<td style="width:125px;">customized</td>
			<td>Set of three ring electrodes to guide ions</td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:223px;">MCP detector</td>
			<td style="width:153px;">Beam-Imaging-Solutions</td>
			<td style="width:125px;">BOS-75-FO</td>
			<td>MCP detector with phosphor sreen</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:223px;">DC voltage supply for MCP</td>
			<td style="width:153px;">Keithley Instruments</td>
			<td style="width:125px;">HV Supply 246</td>
			<td>Voltage supply for MCP front side</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:223px;">DC voltage supply for MCP</td>
			<td style="width:153px;">CMTE (NIM module)</td>
			<td style="width:125px;">HV 3160</td>
			<td>Voltage supply for MCP back side</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:223px;">DC voltage supply for MCP</td>
			<td style="width:153px;">Fluke</td>
			<td style="width:125px;">HV Supply 410B</td>
			<td>Voltage supply for phosphor sreen</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:223px;">CCD camera</td>
			<td style="width:153px;">PointGrey</td>
			<td style="width:125px;">FL2-14S3M-C</td>
			<td>CCD camera for image recording</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:223px;">Control PC 3</td>
			<td style="width:153px;">Fujitsu</td>
			<td style="width:125px;">Esprimo P910</td>
			<td>Control computer for CCD camera</td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:223px;">Light-tight housing</td>
			<td style="width:153px;">Workshop of LMU Munich</td>
			<td style="width:125px;">customized</td>
			<td>Light tight wooden box for CCD camera</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:223px;">Dewar for LN2 supply</td>
			<td style="width:153px;">Isotherm</td>
			<td style="width:125px;">unknown</td>
			<td>Dewar to provide dry nitrogen for venting</td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:223px;">Evaporator for LN2</td>
			<td style="width:153px;">Workshop of LMU Munich</td>
			<td style="width:125px;">customized</td>
			<td>Evaporator to provide dry nitrogen</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:223px;">Single anode MCP detector</td>
			<td style="width:153px;">Hamamatsu</td>
			<td style="width:125px;">F2223</td>
			<td>Single anode MCP for lilfetime measurement</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:223px;">DC voltage supply for MCP</td>
			<td style="width:153px;">Fluke</td>
			<td style="width:125px;">HV supply 410B</td>
			<td>Voltage supply for MCP anode</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:223px;">Power supply for preamplifier</td>
			<td style="width:153px;">Delta Elektronika</td>
			<td style="width:125px;">E 030-1</td>
			<td>Power supply for preamplifier</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:223px;">Preamplifier for MCP signals</td>
			<td style="width:153px;">Ortec&#160;</td>
			<td style="width:125px;">VT120A</td>
			<td>Preamplifier for MCP signals</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:223px;">Amplifier for MCP signals</td>
			<td style="width:153px;">Ortec (NIM module)</td>
			<td style="width:125px;">Ortec 571</td>
			<td>Amplifier for MCP signals</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:223px;">CFD</td>
			<td style="width:153px;">Canberra</td>
			<td style="width:125px;">1428A</td>
			<td>Constant-fraction-discriminator for MCP signals</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:223px;">Multichannel Scaler</td>
			<td style="width:153px;">Stanford Research</td>
			<td style="width:125px;">SR 430</td>
			<td>Multichannel scaler for signal read-out</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:223px;">Control PC 4</td>
			<td style="width:153px;">Fujitsu</td>
			<td style="width:125px;">Esprimo P920</td>
			<td>Control computer for scaler read-out</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:223px;">Labview</td>
			<td style="width:153px;">National Instruments</td>
			<td style="width:125px;">various versions</td>
			<td>Program used for measurement control</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:223px;">Matlab</td>
			<td style="width:153px;">Mathworks Inc.</td>
			<td style="width:125px;">version 7.0</td>
			<td>Program used for data analysis</td>
		</tr>
	</tbody>
</table>

preparing an isotopically pure 229th ion beam for studies of 229mth

A methodology is described to generate an isotopically pure 229Th ion beam in the 2+ and 3+ charge states. This ion beam enables one to investigate the low-lying isomeric first excited state of 229Th at an excitation energy of about 7.8(5) eV and a radiative lifetime of up to 104 seconds. The presented method allowed for a first direct identification of the decay of the thorium isomer, laying the foundations to study its decay properties as prerequisite for an optical control of this nuclear transition. High energy 229Th ions are produced in the &#945;&#160;decay of a radioactive 233U source. The ions are thermalized in a buffer-gas stopping cell, extracted and subsequently an ion beam is formed. This ion beam is mass purified by a quadrupole-mass separator to generate a pure ion beam. In order to detect the isomeric decay, the ions are collected on the surface of a micro-channel plate detector, where electrons, as emitted in the internal conversion decay of the isomeric state, are observed.

The method described before allowed for the extraction of &#945; decay products from a 233U source placed inside a buffer-gas stopping cell, operated at ca. 30 mbar ultra-pure helium gas at room temperature. For the first time up to triply charged ions could be extracted from such a device with high efficiency29. Figure 3a displays the mass spectrum of ions extracted from the buffer-gas cell, showing three groups of 233U &#945;-decay products (plus accompanying contaminant adducts) in singly, doubly and triply charged ionic states. Noteworthy is the dominance of 229Th3+ extraction compared to 233U3+, while both species are extracted with about equal intensity when being doubly charged. This fact was used for comparative measurements with 233U ions, which allowed the exclusion of any ionic impact as signal origin.
<img alt="Figure 3" class="xfigimg" src="/files/ftp_upload/58516/58516fig3.jpg" /> 
Figure 3: Identification of the direct decay of the 229-thorium isomer. a)&#160;Complete mass scan performed with the 233U source 129. Units are given as atomic mass (u) over electric charge (e). b) Comparison of MCP signals obtained during accumulation of thorium and uranium in the 2+ and 3+ charge states (as indicated by the arrows linking to the mass scan). 233U and 234U sources were used (the source number is given on the right-hand side of each row). Each image corresponds to an individual measurement of 2,000 s integration time (20 mm diameter aperture indicated by the dashed circle). Measurements were performed at -25 V MCP surface voltage in order to guarantee soft landing of the ions. c) Signal of the 229Th isomeric decay obtained during 229Th3+ extraction with source 1. A signal area diameter of about 2 mm (FWHM) is achieved. The obtained maximum signal intensity is 0.08 counts/(s mm2) at a background rate of about 0.01 counts /(s mm2). With kind permission of Springer Research 11. <a href="https://www-jove-com.remotexs.ntu.edu.sg/files/ftp_upload/58516/58516fig3large.jpg" target="_blank">Please click here to view a larger version of this figure.</a>
After transport, cooling and mass separation, the ion beam impinges onto the surface of a microchannel-plate detector, where a low attractive surface potential ensures the suppression of ionic impact signals and leaves only electrons arising from the Internal Conversion (IC) decay channel of the 229mTh isomer to be multiplied in the strong electric field of the detector plate channels. The resulting MCP signals as obtained for three different uranium sources are displayed in Figure 3b. The ion species of doubly or triply charged ions which was selected with the help of the quadrupole mass separator in each individual measurement is indicated by the arrows from the upper panel. Shown are pictures acquired with the CCD camera behind the phosphor screen, onto which the electrons from the MCP were accelerated. The field of view of the CCD camera is indicated by the dashed circles for triply (first two columns) and doubly charged (last two columns) 229Th and 233U ions, respectively. The upper row represents the result obtained for a small-area 233U source (ca. 1000 extracted 229Th3+ ions per second, source 1), while the bottom row shows the same for a stronger source with ca. 10,000 extracted 229Th3+ ions per second (source 3). It is obvious that in both cases a clear signal is obtained for 229Th, while no indication of an electron signal is observed for 233U 11. In order to prove that this signal indeed originates from a nuclear deexcitation and not from an atomic shell process, the middle row shows the resulting camera image when using a 234U source, where the &#945; decay populates the neighboring isotope 230Th, with a comparable electronic, yet different nuclear structure. As expected for 230Th, no indication of a conversion electron signal is found in any of the cases studied. So the strong signal, displayed in Figure 3c with excellent signal-to-background ratio, is clearly correlated with the decay of 229mTh.
Additional verification measurements to support this interpretation are shown in Figure 4. They show two measurements to give further evidence that the registered electron signals indeed originate from the decay of the nuclear isomer: in Figure 4a it is shown that the attractive surface potential of the MCP detector was varied from -100 V (favoring the occurrence of electrons from ionic impact) down to 0 V, comparing the count rates registered with the MCP for extracted 229Th2+ (red) and 233U2+ ions (blue). Clearly the count rate drops down to zero for 233U2+ when realizing a &#39;soft landing&#39; of the incoming ions with a surface voltage below ca. -40 V, while a considerable count rate remains for 229Th2+ until the threshold of 0 V. In Figure 4b, the blue curve shows the electron count rate registered for extracted ions after strong acceleration towards the MCP detector surface with -2000 V. Ionic impact of 233U2+ and 229Th2+ ions is observed with about equal intensity, as already shown for doubly charged ions in the extracted mass spectrum of Figure 3a. The red curve shows the same scenario, however now for a &#39;soft landing&#39; of incoming ions with -25 V MCP surface potential. No indication of the ionic impact signal of 233U2+ is visible any more, while for 229Th2+ a signal remains, originating from the isomeric internal conversion decay11.
<img alt="Figure 4" class="xfigimg" src="/files/ftp_upload/58516/58516fig4.jpg" /> 
Figure 4: Isomer decay verification measurements. a) 229Th2+ signal (red) compared to 233U2+ (blue) as a function of the MCP surface voltage. Errors are indicated by shaded bands. b) Signal of extracted ions as a function of the mass-to-charge ratio behind the QMS for MCP surface voltages of -25 V (isomer decay, red) and -2,000 V (ion impact, blue). Note the different integration times and axis scales. In addition to the signal at 114.5 u/e (corresponding to 229Th2+), a further signal at 117.5 u/e occurs, which originates from the isomeric decay of 235U. With kind permission of Springer Research11. <a href="https://www-jove-com.remotexs.ntu.edu.sg/files/ftp_upload/58516/58516fig4large.jpg" target="_blank">Please click here to view a larger version of this figure.</a>
Thus, it can be unambiguously proven (together with additional arguments given in Ref. 11) that the signal observed in Figure 4 originates from the isomeric decay of 229mTh and represents the first direct identification of the deexcitation of this elusive isomer.
Subsequently the segmented extraction-RFQ was operated as a linear Paul trap to create a bunched ion beam, thus allowing for lifetime measurements of the thorium isomer. Since our room-temperature high vacuum does not allow for sufficiently long storage times to investigate the expected radiative lifetime of up to 104 seconds, only a lower limit of t1/2 &#62; 1 minute could be derived for charged 229mTh ions, limited by the maximum achievable ion storage time in the linear Paul trap11. However, using the same detection strategy as applied before for the identification of the isomer decay after neutralization of the thorium ions on the surface of an MCP detector, the expected much shorter lifetime for neutral 229mTh atoms undergoing internal conversion decay provides access to lifetime information12. Figure 5a shows the expected shape of the decay time spectrum as simulated for an ion bunch with a pulse width of 10 &#956;s. While the red curve indicates the ionic impact signal and the signal from an exponential decay with 7 &#956;s half-life is represented by the gray curve with a long decay tail, the expected signal from the decay of the thorium isomer, comprised of both the ionic impact and the exponential isomeric decay, is illustrated by the blue curve. Figure 5b displays the outcome of the corresponding measurement for 233U3+ (red) and 229Th3+ (blue), respectively. While uranium ions only exhibit their ionic impact signal, for 229-thorium clearly the expected decay tail of the isomer decay can be observed12.
<img alt="Figure 5" class="xfigimg" src="/files/ftp_upload/58516/58516fig5.jpg" /> 
Figure 5: Simulated and measured temporal ion impact and decay characteristics. a)&#160;Simulation of the isomer decay time characteristics of 229Th bunches. The simulation is based on a measured bunch shape and the assumption that 2 % of the 229Th ions are in the isomeric state with a half-life of 7 &#956;s after neutralization. The electron detection efficiency is assumed to be 25 times larger than the ion detection efficiency. b) Measurement of the isomeric decay with a bunched 229(m)Th3+ ion beam (blue). A comparative measurement with 233U3+ is shown in red. With kind permission of the American Physical Society12. <a href="https://www-jove-com.remotexs.ntu.edu.sg/files/ftp_upload/58516/58516fig5large.jpg" target="_blank">Please click here to view a larger version of this figure.</a>
Fitting the decay tail with an exponential (corresponding to a linear fit to the logarithmic representation in Figure 6) finally results in a half-life of the neutral 229mTh isomer of 7(1) &#956;s12. This value nicely agrees with the theoretically expected lifetime reduction by nine orders of magnitude from the ca. 104 seconds in case of the charged isomer due to the large conversion coefficient of &#945;IC ~ 109&#160;37.
<img alt="Figure 6" class="xfigimg" src="/files/ftp_upload/58516/58516fig6.jpg" /> 
Figure 6: Fit to 229mTh decay curve. Logarithmic plot of the temporal decay characteristics for 229(m)Th2+ ions (a) and 229(m)Th3+ ions (b) together with a fit curve applied to extract the isomeric half-life of 229mTh after charge recombination on the MCP detector surface. With kind permission of the American Physical Society12. <a href="https://www-jove-com.remotexs.ntu.edu.sg/files/ftp_upload/58516/58516fig6large.jpg" target="_blank">Please click here to view a larger version of this figure.</a>

Watch this Scientific Journal Video about Preparing an Isotopically Pure 229Th Ion Beam for Studies of 229mTh at JoVE.com

Preparing an Isotopically Pure 229Th Ion Beam for Studies of 229mTh

We present a protocol for the generation of an isotopically purified low-energy 229Th ion beam from a 233U source. This ion beam is used for the direct detection of the 229mTh ground-state decay via the internal-conversion decay channel. We also measure the internal conversion lifetime of 229mTh as well.

Preparing an Isotopically Pure 229Th Ion Beam for Studies of 229mTh

A methodology is described to generate an isotopically pure 229Th ion beam in the 2+ and 3+ charge states. This ion beam enables one to investigate the ...

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6.6K 조회수.  Ludwig-Maximilians-Universität München. We present a protocol for the generation of an isotopically purified low-energy 229Th ion beam from a 233U source. This ion beam is used for the direct detection of the 229mTh ground-state decay via the internal-conversion decay channel. We also measure the internal conversion lifetime of 229mTh as well.

비디오: Preparing an Isotopically Pure 229Th Ion Beam for Studies of 229mTh

Construction and Testing of Coin Cells of Lithium Ion Batteries

Rechargeable lithium ion batteries have wide applications in electronics, where customers always demand more capacity and longer lifetime. Lithium ion batteries have also been considered to be used in electric and hybrid vehicles1 or even electrical grid stabilization systems2. All these applications simulate a dramatic increase in the research and development of battery materials3-7, including new materials3,8, doping9, nanostructuring10-13, coatings or surface modifications14-17 and novel binders18. Consequently, an increasing number of physicists, chemists and materials scientists have recently ventured into this area. Coin cells are widely used in research laboratories to test new battery materials; even for the research and development that target large-scale and high-power applications, small coin cells are often used to test the capacities and rate capabilities of new materials in the initial stage. 
 In 2010, we started a National Science Foundation (NSF) sponsored research project to investigate the surface adsorption and disordering in battery materials (grant no. DMR-1006515). In the initial stage of this project, we have struggled to learn the techniques of assembling and testing coin cells, which cannot be achieved without numerous help of other researchers in other universities (through frequent calls, email exchanges and two site visits). Thus, we feel that it is beneficial to document, by both text and video, a protocol of assembling and testing a coin cell, which will help other new researchers in this field. This effort represents the "Broader Impact" activities of our NSF project, and it will also help to educate and inspire students.
In this video article, we document a protocol to assemble a CR2032 coin cell with a LiCoO2 working electrode, a Li counter electrode, and (the mostly commonly used) polyvinylidene fluoride (PVDF) binder. To ensure new learners to readily repeat the protocol, we keep the protocol as specific and explicit as we can. However, it is important to note that in specific research and development work, many parameters adopted here can be varied. First, one can make coin cells of different sizes and test the working electrode against a counter electrode other than Li. Second, the amounts of C black and binder added into the working electrodes are often varied to suit the particular purpose of research; for example, large amounts of C black or even inert powder were added to the working electrode to test the "intrinsic" performance of cathode materials14. Third, better binders (other than PVDF) have also developed and used18. Finally, other types of electrolytes (instead of LiPF6) can also be used; in fact, certain high-voltage electrode materials will require the uses of special electrolytes7.

A protocol to construct and test coin cells of lithium ion batteries is described. The specific procedures of making a working electrode, preparing a counter electrode, assembling a cell inside a glovebox and testing the cell are presented.

건설과 리튬 이온 배터리의 동전 전지의 테스트

Rechargeable lithium ion batteries have wide applications in electronics, where customers always demand more capacity and longer lifetime.  Lithium ion ...

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공학

Characterization of Electrode Materials for Lithium Ion and Sodium Ion Batteries Using Synchrotron Radiation Techniques

Intercalation compounds such as transition metal oxides or phosphates are the most commonly used electrode materials in Li-ion and Na-ion batteries. During insertion or removal of alkali metal ions, the redox states of transition metals in the compounds change and structural transformations such as phase transitions and/or lattice parameter increases or decreases occur. These behaviors in turn determine important characteristics of the batteries such as the potential profiles, rate capabilities, and cycle lives. The extremely bright and tunable x-rays produced by synchrotron radiation allow rapid acquisition of high-resolution data that provide information about these processes. Transformations in the bulk materials, such as phase transitions, can be directly observed using X-ray diffraction (XRD), while X-ray absorption spectroscopy (XAS) gives information about the local electronic and geometric structures (e.g.&#160;changes in redox states and bond lengths). In situ experiments carried out on operating cells are particularly useful because they allow direct correlation between the electrochemical and structural properties of the materials. These experiments are time-consuming and can be challenging to design due to the reactivity and air-sensitivity of the alkali metal anodes used in the half-cell configurations, and/or the possibility of signal interference from other cell components and hardware. For these reasons, it is appropriate to carry out ex situ experiments (e.g.&#160;on electrodes harvested from partially charged or cycled cells) in some cases. Here, we present detailed protocols for the preparation of both ex situ and in situ samples for experiments involving synchrotron radiation and demonstrate how these experiments are done.

We describe the use of synchrotron X-ray absorption spectroscopy (XAS) and X-ray diffraction (XRD) techniques to probe details of intercalation/deintercalation processes in electrode materials for Li-ion and Na-ion batteries. Both in situ and ex situ experiments are used to understand structural behavior relevant to the operation of devices

방사광 기술을 사용하여 리튬 이온과 나트륨 이온 배터리 용 전극 재료의 특성

Intercalation compounds such as transition metal oxides or phosphates are the most commonly used electrode materials in Li-ion and Na-ion batteries. ...

Speciation and Bioavailability Measurements of Environmental Plutonium Using Diffusion in Thin Films

The biological uptake of plutonium (Pu) in aquatic ecosystems is of particular concern since it is an alpha-particle emitter with long half-life which can potentially contribute to the exposure of biota and humans. The diffusive gradients in thin films technique is introduced here for in-situ measurements of Pu bioavailability and speciation. A diffusion cell constructed for laboratory experiments with Pu and the newly developed protocol make it possible to simulate the environmental behavior of Pu in model solutions of various chemical compositions. Adjustment of the oxidation states to Pu(IV) and Pu(V) described in this protocol is essential in order to investigate the complex redox chemistry of plutonium in the environment. The calibration of this technique and the results obtained in the laboratory experiments enable to develop a specific DGT device for in-situ Pu measurements in freshwaters. Accelerator-based mass-spectrometry measurements of Pu accumulated by DGTs in a karst spring allowed determining the bioavailability of Pu in a mineral freshwater environment. Application of this protocol for Pu measurements using DGT devices has a large potential to improve our understanding of the speciation and the biological transfer of Pu in aquatic ecosystems.

The technique of diffusive gradients in thin films (DGT) is proposed for speciation studies of plutonium. This protocol describes diffusion experiments probing the behavior of Pu(IV) and Pu(V) in presence of organic matter. DGTs deployed in a karstic spring allow assessment of the bioavailability of Pu.

박막의 확산을 사용하여 환경 플루토늄의 분화 및 생체 이용률 측정

The biological uptake of plutonium (Pu) in aquatic ecosystems is of particular concern since it is an alpha-particle emitter with long half-life which can ...

Ohmic Contact Fabrication Using a Focused-ion Beam Technique and Electrical Characterization for Layer Semiconductor Nanostructures

Layer semiconductors with easily processed two-dimensional (2D) structures exhibit indirect-to-direct bandgap transitions and superior transistor performance, which suggest a new direction for the development of next-generation ultrathin and flexible photonic and electronic devices. Enhanced luminescence quantum efficiency has been widely observed in these atomically thin 2D crystals. However, dimension effects beyond quantum confinement thicknesses or even at the micrometer scale are not expected and have rarely been observed. In this study, molybdenum diselenide (MoSe2) layer crystals with a thickness range of 6-2,700 nm were fabricated as two- or four-terminal devices. Ohmic contact formation was successfully achieved by the focused-ion beam (FIB) deposition method using platinum (Pt) as a contact metal. Layer crystals with various thicknesses were prepared through simple mechanical exfoliation by using dicing tape. Current-voltage curve measurements were performed to determine the conductivity value of the layer nanocrystals. In addition, high-resolution transmission electron microscopy, selected-area electron diffractometry, and energy-dispersive X-ray spectroscopy were used to characterize the interface of the metal&#8211;semiconductor contact of the FIB-fabricated MoSe2 devices. After applying the approaches, the substantial thickness-dependent electrical conductivity in a wide thickness range for the MoSe2-layer semiconductor was observed. The conductivity increased by over two orders of magnitude from 4.6 to 1,500 &#937;&#8722;1 cm&#8722;1, with a decrease in the thickness from 2,700 to 6 nm. In addition, the temperature-dependent conductivity indicated that the thin MoSe2 multilayers exhibited considerably weak semiconducting behavior with activation energies of 3.5-8.5 meV, which are considerably smaller than those (36-38 meV) of the bulk. Probable surface-dominant transport properties and the presence of a high surface electron concentration in MoSe2 are proposed. Similar results can be obtained for other layer semiconductor materials such as MoS2 and WS2.

We describe the approaches for the device fabrication and electrical characterization of molybdenum diselenide (MoSe2) layer semiconductor nanostructures with different thicknesses. In addition, the fabrication of ohmic contacts for MoSe2-layer nanocrystals by the focused-ion beam deposition method using platinum (Pt) as a contact metal is described.

오믹 접촉 제조 집중 이온 빔 기술 및 전기 특성 계층 반도체 나노 구조를 위해 사용

Layer semiconductors with easily processed two-dimensional (2D) structures exhibit indirect-to-direct bandgap transitions and superior transistor ...

Fabrication of Polymer Microspheres for Optical Resonator and Laser Applications

This paper describes three methods of preparing fluorescent microspheres comprising &#960;-conjugated or non-conjugated polymers: vapor diffusion, interface precipitation, and mini-emulsion. In all methods, well-defined, micrometer-sized spheres are obtained from a self-assembling process in solution. The vapor diffusion method can result in spheres with the highest sphericity and surface smoothness, yet the types of the polymers able to form these spheres are limited. On the other hand, in the mini-emulsion method, microspheres can be made from various types of polymers, even from highly crystalline polymers with coplanar, &#960;-conjugated backbones. The photoluminescent (PL) properties from single isolated microspheres are unusual: the PL is confined inside the spheres, propagates at the circumference of the spheres via the total internal reflection at the polymer/air interface, and self-interferes to show sharp and periodic resonant PL lines. These resonating modes are so-called "whispering gallery modes" (WGMs). This work demonstrates how to measure WGM PL from single isolated spheres using the micro-photoluminescence (&#181;-PL) technique. In this technique, a focused laser beam irradiates a single microsphere, and the luminescence is detected by a spectrometer. A micromanipulation technique is then used to connect the microspheres one by one and to demonstrate the intersphere PL propagation and color conversion from coupled microspheres upon excitation at the perimeter of one sphere and detection of PL from the other microsphere. These techniques, &#181;-PL and micromanipulation, are useful for experiments on micro-optic application using polymer materials.

Protocols for the synthesis of microspheres from polymers, the manipulation of microspheres, and micro-photoluminescence measurements are presented.

광 공진기 및 레이저 응용을위한 고분자 미소 구의 제조

This paper describes three methods of preparing fluorescent microspheres comprising &#960;-conjugated or non-conjugated polymers: vapor diffusion, ...

Experimental Methods for Trapping Ions Using Microfabricated Surface Ion Traps

Ions trapped in a quadrupole Paul trap have been considered one of the strong physical candidates to implement quantum information processing. This is due to their long coherence time and their capability to manipulate and detect individual quantum bits (qubits). In more recent years, microfabricated surface ion traps have received more attention for large-scale integrated qubit platforms. This paper presents a microfabrication methodology for ion traps using micro-electro-mechanical system (MEMS) technology, including the fabrication method for a 14 &#181;m-thick dielectric layer and metal overhang structures atop the dielectric layer. In addition, an experimental procedure for trapping ytterbium (Yb) ions of isotope 174 (174Yb+) using 369.5 nm, 399 nm, and 935 nm diode lasers is described. These methodologies and procedures involve many scientific and engineering disciplines, and this paper first presents the detailed experimental procedures. The methods discussed in this paper can easily be extended to the trapping of Yb ions of isotope 171 (171Yb+) and to the manipulation of qubits.

This paper presents a microfabrication methodology for surface ion traps, as well as a detailed experimental procedure for trapping ytterbium ions in a room-temperature environment.

﹙을 사용 하 여 이온을 트래핑에 대 한 실험 방법 표면 이온 트랩

Ions trapped in a quadrupole Paul trap have been considered one of the strong physical candidates to implement quantum information processing. This is due ...

Focused Ion Beam Fabrication of LiPON-based Solid-state Lithium-ion Nanobatteries for In Situ Testing

Solid-state electrolytes are a promising replacement for current organic liquid electrolytes, enabling higher energy densities and improved safety of lithium-ion (Li-ion) batteries. However, a number of setbacks prevent their integration into commercial devices. The main limiting factor is due to nanoscale phenomena occurring at the electrode/electrolyte interfaces, ultimately leading to degradation of battery operation. These key problems are highly challenging to observe and characterize as these batteries contain multiple buried interfaces. One approach for direct observation of interfacial phenomena in thin film batteries is through the fabrication of electrochemically active nanobatteries by a focused ion beam (FIB). As such, a reliable technique to fabricate nanobatteries was developed and demonstrated in recent work. Herein, a detailed protocol with a step-by-step process is presented to enable the reproduction of this nanobattery fabrication process. In particular, this technique was applied to a thin film battery consisting of LiCoO2/LiPON/a-Si, and has further been previously demonstrated by in situ cycling within a transmission electron microscope.

Focused Ion Beam Fabrication of LiPON-based Solid-state Lithium-ion Nanobatteries for In Situ Testing

A protocol for the fabrication of electrochemically active LiPON-based solid-state lithium-ion nanobatteries using a focused ion beam is presented.

집중 된 이온 빔 제작 현장에서 테스트 LiPON 기반 고체 리튬-이온 Nanobatteries

Solid-state electrolytes are a promising replacement for current organic liquid electrolytes, enabling higher energy densities and improved safety of ...

Three-electrode Coin Cell Preparation and Electrodeposition Analytics for Lithium-ion Batteries

As lithium-ion batteries find use in high energy and power applications, such as in electric and hybrid-electric vehicles, monitoring the degradation and subsequent safety issues becomes increasingly important. In a Li-ion cell setup, the voltage measurement across the positive and negative terminals inherently includes the effect of the cathode and anode which are coupled and sum to the total cell performance. Accordingly, the ability to monitor the degradation aspects associated with a specific electrode is extremely difficult because the electrodes are fundamentally coupled. A three-electrode setup can overcome this problem. By introducing a third (reference) electrode, the influence of each electrode can be decoupled, and the electrochemical properties can be measured independently. The reference electrode (RE) must have a stable potential that can then be calibrated against a known reference, for example, lithium metal. The three-electrode cell can be used to run electrochemical tests such as cycling, cyclic voltammetry, and electrochemical impedance spectroscopy (EIS). Three-electrode cell EIS measurements can elucidate the contribution of individual electrode impedance to the full cell. In addition, monitoring the anode potential allows the detection of electrodeposition due to lithium plating, which can cause safety concerns. This is especially important for the fast charging of Li-ion batteries in electric vehicles. In order to monitor and characterize the safety and degradation aspects of an electrochemical cell, a three-electrode setup can prove invaluable. This paper aims to provide a guide to constructing a three-electrode coin cell setup using the 2032-coin cell architecture, which is easy to produce, reliable, and cost-effective.

Three-electrode cells are useful in studying the electrochemistry of lithium-ion batteries. Such an electrochemical setup allows the phenomena associated with the cathode and anode to be decoupled and examined independently. Here, we present a guide for construction and use of a three-electrode coin cell with emphasis on lithium plating analytics.

3 전극 동전 전지 준비 및 Electrodeposition 리튬-이온 배터리에 대 한 분석

As lithium-ion batteries find use in high energy and power applications, such as in electric and hybrid-electric vehicles, monitoring the degradation and ...

Single-Digit Nanometer Electron-Beam Lithography with an Aberration-Corrected Scanning Transmission Electron Microscope

We demonstrate extension of electron-beam lithography using conventional resists and pattern transfer processes to single-digit nanometer dimensions by employing an aberration-corrected scanning transmission electron microscope as the exposure tool. Here, we present results of single-digit nanometer patterning of two widely used electron-beam resists: poly (methyl methacrylate) and hydrogen silsesquioxane. The method achieves sub-5 nanometer features in poly (methyl methacrylate) and sub-10 nanometer resolution in hydrogen silsesquioxane. High-fidelity transfer of these patterns into target materials of choice can be performed using metal lift-off, plasma etch, and resist infiltration with organometallics.

We use an aberration-corrected scanning transmission electron microscope to define single-digit nanometer patterns in two widely-used electron-beam resists: poly (methyl methacrylate) and hydrogen silsesquioxane. Resist patterns can be replicated in target materials of choice with single-digit nanometer fidelity using liftoff, plasma etching, and resist infiltration by organometallics.

자리 나노미터 전자 빔 리소 그래피는 수 차 수정 스캐닝 전송 전자 현미경으로

We demonstrate extension of electron-beam lithography using conventional resists and pattern transfer processes to single-digit nanometer dimensions by ...

Preparation of Graphene Liquid Cells for the Observation of Lithium-ion Battery Material

In this work, we introduce the preparation of graphene liquid cells (GLCs), encapsulating both electrode materials and organic liquid electrolytes between two graphene sheets, and the facile synthesis of one-dimensional nanostructures using electrospinning. The GLC enables in situ transmission electron microscopy (TEM) for the lithiation dynamics of electrode materials. The in situ GLC-TEM using an electron beam for both imaging and lithiation can utilize not only realistic battery electrolytes, but also the high-resolution imaging of various morphological, phase, and interfacial transitions.

Here, we present a protocol for the fabrication and preparation of a graphene liquid cell for in situ transmission electron microscopy observation, along with a synthesis of electrode materials and electrochemical battery cell tests.

그래 액체 셀 리튬-이온 배터리 재료의 관찰에 대 한 준비

In this work, we introduce the preparation of graphene liquid cells (GLCs), encapsulating both electrode materials and organic liquid electrolytes between ...