This work was supported by the Fundamental Research Program (No. JCKY2017601C). We appreciate the helping of Thomas M. York, Emeritus Professor at Ohio State University.

1.&#160;Preparation for experiment
<ol>
	<li>Install the thruster.
	<ol>
		<li>Wipe the components of the thruster withnon-dust cloth,soaked with anhydrous alcohol, in a clean room.</li>
		<li>Assemble the anode with the insulator.</li>
		<li>Bring together the cathode, cathode holder and cathode connector.</li>
		<li>Add the cathode part to the anode part.</li>
		<li>Install the middle connector into the assemblage and fix them with screws (hexagon socket head screw, M5&#215;16).</li>
		<li>Establish the coil seat on experiment platform with forklift.</li>
		<li>Place the experiment platform on guide rail of the vacuum chamber.</li>
		<li>Install the thruster on the coil.</li>
		<li>Link the anode and cathode with corresponding electric cables.</li>
		<li>Link the magnetic coil with the coil power source.</li>
		<li>Join up the water-cooling pipes and propellant supply pipe with the thruster.</li>
		<li>Join up the water-cooling pipes with the coil.</li>
		<li>Install the moveable platform inside the chamber and fix the main body of thrust stand on it.</li>
		<li>Adjust the position of the radial moveable platform to make the control lines of the thruster and the target coincide with each other.</li>
	</ol>
	</li>
	<li>Calibrate the thrust stand.
	<ol>
		<li>Load different weights (10 g, 50 g, 100 g, 200 g), one by one, on the calibration device and record the corresponding output of the thrust stand.</li>
		<li>Unload the weights one by one.</li>
		<li>Repeat the process for three times at least.</li>
		<li>Calculate the elastic coefficient of the thrust stand according to the calibration data.</li>
	</ol>
	</li>
	<li>Evacuate the vacuum chamber.
	<ol>
		<li>Close the door of the chamber.</li>
		<li>Start the mechanical pumps.</li>
		<li>Start the molecular pumps when the background pressure in the chamber is lower than 5 Pa.</li>
		<li>Start the cryogenic pumps when the background pressure in the chamber is lower than 0.05 Pa.</li>
		<li>Wait for the pressure to reach 1 x 10-4 Pa.</li>
	</ol>
	</li>
</ol>
2. Ignition and Thrust Measurement Experiment
<ol>
	<li>Preheat the thruster if it has been exposed to the air.
	<ol>
		<li>Start recording the signal.</li>
		<li>Set the propellant mass flow rate at 40 mg/s and keep supplying for at least 20 minutes</li>
		<li>Turn on the cooling water supply.</li>
		<li>Set the working frequency of cooling water pumps at 10 Hz.</li>
		<li>Move the thrust stand to the position far from the thruster.</li>
		<li>Switch on the coil power source with the coil current of 90 A.</li>
		<li>Switch on the thruster power source with the discharge current of 240 A.</li>
		<li>Switch on the ignition power source.</li>
		<li>Keep the thruster working for at least 5 minutes.</li>
		<li>Switch off the thruster power source and propellant supply.</li>
		<li>Stop the recording.</li>
	</ol>
	</li>
	<li>Thrust measurement
	<ol>
		<li>Move the thrust stand to the position 550 mm from the thruster.</li>
		<li>Start recording the signal.</li>
		<li>Start the propellant supply.</li>
		<li>Ignite the thruster with 90 A coil current and 240 A discharge current.</li>
		<li>Increase the coil current to 150 A.</li>
		<li>Increase the discharge current to 800 A.</li>
		<li>Increase the coil current to 230 A.</li>
		<li>Switch off the thruster when the output of thrust stand becomes stable.</li>
		<li>Stop the propellant supply.</li>
		<li>Stop the recording.</li>
	</ol>
	</li>
</ol>

<ol><li>Kodys, A., Choueiri, E. A Critical Review of the State-of-the-Art in the Performance of Applied-field Magnetoplasmadynamic Thrusters. AIAA/ASME/SAE /ASEE Joint Propulsion Conference & Exhibit, , AIAA paper 2005-4247 (2005).</li>
<li>Arakawa, Y., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Electromagnetic+Effects+in+an+Applied-field+Magnetoplasmadynamic+Thruster%5BTitle%5D)+AND+%22Journal+of+Propulsion+%26+Power%22%5BJournal%5D)">Electromagnetic Effects in an Applied-field Magnetoplasmadynamic Thruster.</a> Journal of Propulsion & Power. 8 (1), 98-102 (1992).</li>
<li>Myers, R., Lapointe, M., Mantenieks, M. MPD thruster Technology. Conference on Advanced SEI Technologies, , AIAA paper 91-3568 (1991).</li>
<li>Myers, R. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Applied-field+MPD+thruster+performance+with+hydrogen+and+argon+propellants%5BTitle%5D)+AND+%22Journal+of+Propulsion+%26+Power%22%5BJournal%5D)">Applied-field MPD thruster performance with hydrogen and argon propellants.</a> Journal of Propulsion & Power. 9 (5), 781-784 (1993).</li>
<li>Albertoni, R., Rossetti, P., Paganucci, F., Andrenucci, M. Experimental Study of a 100-kW class Applied-Field MPD Thruster. 32nd International Electric Propulsion Conference, , IEPC-2011-110 (2011).</li>
<li>Lapointe, M., Strzempkowski, E., Pencil, E. High Power MPD Thruster Performance Measurements. AIAA paper 2004-3467, , (2004).</li>
<li>Tahara, H., Kagaya, Y., Yoshikawa, T. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Performance+and+Acceleration+Process+of+Quasisteady+Magnetoplasmadynamic+Arcjets+with+Applied+Magnetic+Fields%5BTitle%5D)+AND+%22Journal+of+Propulsion+and+Power%22%5BJournal%5D)">Performance and Acceleration Process of Quasisteady Magnetoplasmadynamic Arcjets with Applied Magnetic Fields.</a> Journal of Propulsion and Power. 13 (5), 651-658 (1997).</li>
<li>Tahara, H., Kagaya, K., Yoshikawai, T. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Effects+of+Applied+Magnetic+Fields+on+Performance+of+a+Quasisteady+Magnetoplasmadynamic+Arc%5BTitle%5D)+AND+%22Journal+of+Propulsion+and+Power%22%5BJournal%5D)">Effects of Applied Magnetic Fields on Performance of a Quasisteady Magnetoplasmadynamic Arc.</a> Journal of Propulsion and Power. 11 (2), 337-342 (1995).</li>
<li>Li, Z., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Increasing+the+Effective+Voltage+in+Applied-Field+MPD+Thrusters%5BTitle%5D)+AND+%22Journal+of+Physics+D+Applied+Physics%22%5BJournal%5D)">Increasing the Effective Voltage in Applied-Field MPD Thrusters.</a> Journal of Physics D Applied Physics. 51, 085201(2018).</li>
<li>Myers, R., Mantenieks, M., Sovey, J. Geometric Effects in Applied-field MPD Thrusters. 21st International Electric Propulsion Conference, , AIAA paper 1990-2669 (1990).</li>
<li>Myers, R. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Geometric+Scaling+of+Applied-Field+Magnetoplasmadynamic+Thrusters%5BTitle%5D)+AND+%22Journal+of+Propulsion+and+Power%22%5BJournal%5D)">Geometric Scaling of Applied-Field Magnetoplasmadynamic Thrusters.</a> Journal of Propulsion and Power. 11 (2), 343-350 (1995).</li>
<li>Mikelides, P. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Applied-Field+Magnetoplasmadynamic+Thrusters%2C+Part+2%3A+Analytic+Expressions+for+Thrust+and+Voltage%5BTitle%5D)+AND+%22Journal+of+Propulsion+and+Power%22%5BJournal%5D)">Applied-Field Magnetoplasmadynamic Thrusters, Part 2: Analytic Expressions for Thrust and Voltage.</a> Journal of Propulsion and Power. 16 (5), 894-901 (2000).</li>
<li>Nakata, D., et al. Experimental Study for the Optimal Electrode Geometry in an MPD Thruster. 45th AIAA Aerospace Sciences Meeting and Exhibit, Aerospace Sciences Meetings. Nevada), , AIAA 2007-2589 (2007).</li>
<li>Kurtz, H., Auweter-Kurtz, M., Merke, W., Schrade, H. Experimental MPD thruster investigations. 19th International Electric Propulsion Conference. AIAA paper 87-1019, , AIAA paper 87-1019 (1987).</li>
<li>Blackstock, A. W., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Experiments+Using+a+25-kW+Hollow+Cathode+Lithium+Vapor+MPD+Arcjet%5BTitle%5D)+AND+%22AIAA+Journal%22%5BJournal%5D)">Experiments Using a 25-kW Hollow Cathode Lithium Vapor MPD Arcjet.</a> AIAA Journal. 8 (5), 886-894 (1970).</li>
<li>Krulle, G. Characteristics and local analysis of MPD thruster operation. AIAA Electric Propulsion and Plasmadynamics Conference. AIAA paper, , AIAA paper 1967-672 (1967).</li>
<li>Malliaris, A. C., Libby, D. R. Velocities of Neutral and Ionic Species in a MPD Flow. In AIAA 7th Aerospace Sciences Meeting, , AIAA paper 1969-1109 (1969).</li>
<li>Wang, B., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Target+thrust+measurement+for+applied-field+magnetoplasmadynamic+thruster%5BTitle%5D)+AND+%22Measurement+Science+%26+Technology%22%5BJournal%5D)">Target thrust measurement for applied-field magnetoplasmadynamic thruster.</a> Measurement Science & Technology. 29, 075302(2018).</li>
<li>Tikhonov, V. B., Semenikhin, S. A., Brophy, J. R., Polk, J. E. <a target="_blank" href="http://scholar.google.com/scholar?hl=en&safe=off&q=author%3aTikhonov%2C+VB+%22The+Experimental+Performance+of+the+100-kW+Li+MPDT+with+External+Magnetic%22">The Experimental Performance of the 100-kW Li MPDT with External Magnetic</a>. , IEPC-95-105 (1995).</li>
<li>Burkhart, J. A., et al. <a target="_blank" href="http://scholar.google.com/scholar?hl=en&safe=off&q=author%3aBurkhart%2C+JA+%22Low+environmental+pressure+MPD+arc+tests%22">Low environmental pressure MPD arc tests</a>. , AIAA paper 67-685 (1967).</li>
<li>Boxberger, A., Jüstel, P., Herdrich, G. Performance of 100 kW Steady State Applied-Field MPD Thruster. Int. Symp. on Space Technology and Science, Matsuyama, Japan, , (2017).</li>
<li>Malliaris, A. C., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Performance+of+Quasi-Steady+MPD+Thrusters+at+High+Powers%5BTitle%5D)+AND+%22AIAA+Journal%22%5BJournal%5D)">Performance of Quasi-Steady MPD Thrusters at High Powers.</a> AIAA Journal. 10 (2), 121-122 (1972).</li>
<li>Knudsen, B. M. The Kinetic Theory of Gases (London:Methuen). , 26-27 (1950).</li>
<li>Auweter-Kurtz, M., Krulle, G., Kurtz, H. The Investigation of Applied-Field MPD Thrusters on the International Space Station. 25th Electric Propulsion Conference, , IEPC-97-116 (1997).</li>
<li>Connolly, D., Sovie, R. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Effect+of+background+pressure+on+magnetoplasmadynamic+thruster+operation%5BTitle%5D)+AND+%22Journal+of+Spacecraft+and+Rockets%22%5BJournal%5D)">Effect of background pressure on magnetoplasmadynamic thruster operation.</a> Journal of Spacecraft and Rockets. 7 (3), 255-258 (1970).</li>
<li>Esker, D., Kroutil, J., Sedrick, A. <a target="_blank" href="http://scholar.google.com/scholar?hl=en&safe=off&q=author%3aEsker%2C+D+%22Cathode+Studies+of+a+Radiation+Cooled+MPD+Arc+Thruster%22">Cathode Studies of a Radiation Cooled MPD Arc Thruster</a>. , AIAA paper 1970-1083 (1970).</li>
<li>Myers, R. Plume characteristics of MPD thrusters - A preliminary examination. 25th Joint Propulsion Conference, , AIAA paper 89-2832 (1989).</li>
</ol>

The authors have nothing to disclose.

This protocol describes the processes of ignition, operation, and thrust measurement of a 100 kW class applied field MPD thruster. The key point in designing an MPD thruster for optimum performance is choosing the proper configuration according to the specific objective. MPD thrusters with convergent-divergent anode can function steady-state in a large operation range. However, the performance may be lower than the thruster with divergent anode. The hollow cathode, especially the multichannel hollow cathode, is superior to a traditional rod cathode in most aspects. Application of the hollow cathode is beneficial for improving thruster performance, and it provides choices for propellant supply modes. Manufacturing cost of a hollow cathode is relatively high compared with a solid cathode.
A fluid circuit cooling structure is necessary for operation of the thruster if it is designed to work for more than 10 minutes. Alternatively, radiation cooling is another choice26, which can avoid complex coolant piping. However, this may cause a large radial size of the thruster. Furthermore, a heat pipe can be another choice when employed in actual space mission.
An external magnetic field is indispensable for the AF-MPD thruster. The field can be provided by a traditional solenoid coil, as described in the protocol, or a permanent magnet. In addition, superconductivity is a potential candidate, which can provide much stronger magnetic field than traditional coil and the mass of which is also less than the traditional solenoid coil.
To hold the thrust measurement experiment, the background pressure should be lower than 0.013-0.13 Pa1. Otherwise, the operation of the thruster may be influenced. In addition, according to research27, there are outflow currents in the plumes of MPD thrusters and the furthest current can reach the position 90 cm from the thruster in axial direction. Thus, increasing the size of the chamber is beneficial for decreasing the influence of the facility on the thruster.

MPD thrusters are well known for a relatively high thrust density and a high specific impulse1,2,3. However, the typical thrust efficiency1 of MPD thrusters is relatively low, especially with propellants of noble gases4,5,6. For most MPD thrusters, a part of the propellant flow is injected into the discharge chamber from a slit between anode and cathode7,8 , with the result that a radial component is a significant proportion of the total discharge. However, in order to generate thrust, radial kinetic effects need to be converted into axial kinetic motion with a physical nozzle or a magnetic nozzle. Accordingly, a key feature of the new design MPD thruster is that all propellant is supplied through the cathode, which can act to inhibit radial discharge; in this way, the proportion of axial energy can be increased. There is an added effect in that the Hall parameter in the plasma around the anode can be increased by the decrease of the number density around the anode, which can strengthen the Hall acceleration component9. Since the propellant is close to the inner surface of the cathode where large quantities of initial electrons are emitted in this mode of injection, the propellant ionization rate can be increased greatly. Furthermore, the anode length has been minimized to decrease the wall-plasma connecting area and reduce anode power deposition10,11. As a divergent anode is applied, this will decrease the angle between the anode and magnetic field lines and decrease anode power deposition further12,13.
Despite the advantages noted above to improve performance, complete propellant supply by cathode injection can increase the risk of anode starvation which can result in &#34;onset&#34; phenomena14. To inhibit this behavior, we have retracted the cathode back to the base of anode. The electrons can then diffuse sufficiently in the radial direction before leaving the anode exit, which will act to relieve anode starvation. Further, a multichannel hollow cathode is adopted; compared to the single channel hollow cathode, a multichannel hollow cathode can increase the electron emission area and make the distribution of the propellant more uniform. With this modification, both the lifetime and stability of the thruster can be increased15,16,17.
The designed power of the thruster is 100 kW and a cooling structure is necessary with steady state operation. In the present laboratory experiments, an efficient water-cooling structure is employed. However, to evaluate the performance of the MPD thruster design, it is critical to obtain the thrust. With the application of a high-pressure water system to transfer heat, there will be strong vibration during the operation of such cooling, which can create significant interference if we used traditional thrust measurements. Accordingly, a target thrust stand is employed to measure the thrust.
MPD Thruster
As shown in Figure 1, the MPD thruster consists of anode, cathode and insulator.&#160;The anode is made of copper with a cylindrical divergent nozzle, the minimum inner diameter of which is 60 mm. There is an S-shaped cooling channel around the inner wall of the anode. The inlet and outlet of the channel are on the top of the anode, which are separated by a baffle. A slender copper block is employed to connect the anode and electric cable. The junction is on the outer surface of the anode.
The cathode material is tantalum tungsten, with nine propellant channels. The outer diameter of the cathode is 16 mm. The cooling of the cathode is achieved with a water-cooling holder around the cathode base. There is a ring-shaped channel inside the holder. The cold water is injected into the holder from the bottom and flows out from the top. There is a hollow cathode connector on the left side of the cathode. The propellant flows through the center of the connector and into the hollow cathode chamber; there is a large cavity inside the cathode base connecting with nine narrow cylindrical channels. The cavity acts as a buffer to increase the uniformity of the propellant distribution in nine channels. The cathode is connected to the electric cable with an annular copper block, which is installed around the cathode connector.
In addition to the main body of the thruster, an external magnetic coil is also necessary to generate fields for the mechanisms in the AF-MPD thruster; magnetic fields provide a convergent-divergent magnetic field to accelerate the plasma together with the electric field. The field coil consists of 288 turns of circular copper pipes, which act as the passage for both electric current and cooling water. The inner diameter of the coil is 150 mm, while the outer diameter is 500 mm. The highest field strength in the center is 0.25 T with current of 230 A.
Experiment System
The experiment system includes six subsystems. The schematic diagram of the overall layout of the experimental system is shown in Figure 2; the layout of the thruster inside the vacuum chamber is shown in Figure 3.
First, the vacuum system, which provides the necessary vacuum environment for the thruster operation, consists of one vacuum chamber, two mechanical pumps, one molecular pump and four cryogenic pumps. The diameter of the chamber is 3 m, and the length is 5 m. The environment pressure can be maintained under 0.01 Pa when the flow rate of (argon) propellant is no more than 40 mg/s.
Second, this source system provides a high voltage pulse to ignite the thruster, provides power for the thruster to accelerate the plasma, and provides power for the magnetic field coil to sustain the external magnetic field. The power source system consists of an ignition power source, a thruster power source, a coil power source and cables. The ignition power source can provide 8 kV or 15 kV discharge voltage. The thruster power source provides a direct current up to 1000 A. The coil power source provides a direct current up to 240 A.
Third, the propellant supply system feeds gas propellant for thrusters. The system mainly includes the gas source, the mass flow rate controller and gas supply pipelines.
The fourth sub-system is the water-cooling system, which provides cool high-pressure water to exchange the heat of the thruster, magnetic coil and power sources. As shown in Figure 4, the system consists of pumps group, water tank, refrigerator, water supply pipelines and pumps controllers. The non-conducting pipes inside the vacuum chamber provide a cooling water terminal for the thruster and magnetic coil, and ensures that electrical insulation among the anode, the cathode, and the ground.
The acquisition and control system can record the signals measuring thruster operation conditions and control operation of other systems. It is composed of three computers and corresponding software, data acquisition card and cables.
As shown in Figure 5, the target thrust stand consists of plate target, slender beam, displacement sensor, support frame, axial moveable platform and radial moveable platform. The target can intercept the plasma which pushes the target. The displacement of the target can be measured by a sensor placed behind the target, in this way enabling evaluation of the thrust18.

<table><tbody><tr><td>Cryogenic Pumps</td><td>Brooks Automation</td><td></td><td>Pumping speed: 10000L/s</td></tr><tr><td>Displacement Sensor</td><td>Panasonic</td><td>HG-C1030</td><td>Repetition precision: 10&amp;mu;m&lt;br/&gt; Linearity: &amp;plusmn;0.1% F.S.</td></tr><tr><td>Mass Flow Rate Controller</td><td>Brooks Automation</td><td></td><td>Range: 0-120mg/s</td></tr><tr><td>Molecular Pump</td><td>Oerlikon</td><td></td><td>Pumping speed: 2100L/s</td></tr><tr><td>Moveable Plantform</td><td>Beijing Weina Guangke Automation equipment Co., Ltd.</td><td></td><td>Range:0-2000mm</td></tr><tr><td>Plsatic Water Pipes</td><td>Xingye Xingye fluoroplastics (Jiaxing) Co., Ltd.</td><td></td><td>Ultimate pressure: 4.5MPa</td></tr><tr><td>Propellant Argon</td><td>Beijing Huanyu Hinghui Gas Technology Co., Ltd.</td><td></td><td>Purity:99.999%</td></tr><tr><td>Refrigerator</td><td>Beijing Jiuzhou Tongcheng Technology Co., Ltd.</td><td></td><td>Refrigeration power:45kW</td></tr><tr><td>Water Pumps</td><td>Liaocheng vanguard Motor Co., Ltd.;&lt;br/&gt; Shanghai people pump industry group Manufacturing Co., Ltd.;&lt;br/&gt; Nanfang Pump Limited company</td><td></td><td>Maximum Output pressure:&lt;br/&gt; Centrifugal pump:1MPa&lt;br/&gt; Plunger pump:10MPa</td></tr></tbody></table>

a 100 kw class applied-field magnetoplasmadynamic thruster

Applied-field magnetoplasmadynamic thrusters (AF-MPD thrusters) are hybrid accelerators in which electromagnetic and gas dynamic processes accelerate plasma to high speed; they have considerable potential for future space applications with the significant advantages of high specific impulse and thrust density. In this paper, we present a series of protocols for designing and manufacturing a 100 kW class of AF-MPD thruster with water-cooling structures, a 130 V maximum discharge voltage, a 800 A maximum discharge current, and a 0.25 T maximum strength of magnetic field. A hollow tantalum tungsten cathode acts as the only propellant inlet to inhibit the radial discharge, and it is positioned axially at the rear of the anode in order to relieve anode starvation. A cylindrical divergent copper anode is employed to decrease anode power deposition, where the length has been reduced to decrease the wall-plasma connecting area. Experiments utilized a vacuum system that can achieve a working vacuum of 0.01 Pa for a total propellant mass flow rate lower than 40 mg/s and a target thrust stand. The thruster tests were carried out to measure the effects of the working parameters such as propellant flow rates, the discharge current, and the strength of applied magnetic field on the performance and to allow appropriate analysis. The thruster could be operated continuously for significant periods of time with little erosion on the hollow cathode surface. The maximum power of the thruster is 100 kW, and the performance of this water-cooled configuration is comparable with that of thrusters reported in the literature.

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A 100 KW Class Applied-field Magnetoplasmadynamic Thruster

The goal of this protocol is to introduce the design of a 100 kW class applied-field magnetoplasmadynamic thruster and relevant experimental methods.

Applied-field magnetoplasmadynamic thrusters (AF-MPD thrusters) are hybrid accelerators in which electromagnetic and gas dynamic processes accelerate ...

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9.0K Views.  Beihang University. The goal of this protocol is to introduce the design of a 100 kW class applied-field magnetoplasmadynamic thruster and relevant experimental methods.

Video: A 100 KW Class Applied-field Magnetoplasmadynamic Thruster

How to Ignite an Atmospheric Pressure Microwave Plasma Torch without Any Additional Igniters

This movie shows how an atmospheric pressure plasma torch can be ignited by microwave power with no additional igniters. After ignition of the plasma, a stable and continuous operation of the plasma is possible and the plasma torch can be used for many different applications. On one hand, the hot (3,600 K gas temperature) plasma can be used for chemical processes and on the other hand the cold afterglow (temperatures down to almost RT) can be applied for surface processes. For example chemical syntheses are interesting volume processes. Here the microwave plasma torch can be used for the decomposition of waste gases which are harmful and contribute to the global warming but are needed as etching gases in growing industry sectors like the semiconductor branch. Another application is the dissociation of CO2. Surplus electrical energy from renewable energy sources can be used to dissociate CO2 to CO and O2. The CO can be further processed to gaseous or liquid higher hydrocarbons thereby providing chemical storage of the energy, synthetic fuels or platform chemicals for the chemical industry. Applications of the afterglow of the plasma torch are the treatment of surfaces to increase the adhesion of lacquer, glue or paint, and the sterilization or decontamination of different kind of surfaces. The movie will explain how to ignite the plasma solely by microwave power without any additional igniters, e.g., electric sparks. The microwave plasma torch is based on a combination of two resonators &#8212; a coaxial one which provides the ignition of the plasma and a cylindrical one which guarantees a continuous and stable operation of the plasma after ignition. The plasma can be operated in a long microwave transparent tube for volume processes or shaped by orifices for surface treatment purposes.

This movie shows how an atmospheric plasma torch can be ignited by microwaves with no additional igniters and provides a stable and continuous plasma operation suitable for plenty of applications.

This movie shows how an atmospheric pressure plasma torch can be ignited by microwave power with no additional igniters. After ignition of the plasma, a ...

Experimental Methods of Dust Charging and Mobilization on Surfaces with Exposure to Ultraviolet Radiation or Plasmas

Electrostatic dust transport has been hypothesized to explain a number of observations of unusual planetary phenomena. Here, it is demonstrated using three recently developed experiments in which dust particles are exposed to thermal plasma with beam electrons, beam electrons only, or ultraviolet (UV) radiation only. The UV light source has a narrow bandwidth in wavelength centered at 172 nm. The beam electrons with the energy of 120 eV are created with a negatively biased hot filament. When the vacuum chamber is filled with the argon gas, a thermal plasma is created in addition to the electron beam. Insulating dust particles of a few tens of microns in diameter are used in the experiments. Dust particles are recorded to be lofted to a height up to a few centimeters with a launch speed up to 1 m/s. These experiments demonstrate that photo and/or secondary electron emission from a dusty surface changes the charging mechanism of dust particles. According to the recently developed &#34;patched charge model&#34;, the emitted electrons can be re-absorbed inside microcavities between neighboring dust particles below the surface, causing the accumulation of enhanced negative charges on the surrounding dust particles. The repulsive forces between these negatively charged particles may be large enough to mobilize and lift them off the surface. These experiments present the advanced understanding of dust charging and transport on dusty surfaces, and laid a foundation for future investigations of its role in the surface evolution of airless planetary bodies.

Dust charging and mobilization is demonstrated in three experiments with exposure to thermal plasma with beam electrons, beam electrons only, or ultraviolet (UV) radiation only. These experiments present the advanced understanding of electrostatic dust transport and its role in shaping the surfaces of airless planetary bodies.

Electrostatic dust transport has been hypothesized to explain a number of observations of unusual planetary phenomena. Here, it is demonstrated using ...

Environment

Emission Spectroscopic Boundary Layer Investigation during Ablative Material Testing in Plasmatron

Ablative Thermal Protection Systems (TPS) allowed the first humans to safely return to Earth from the moon and are still considered as the only solution for future high-speed reentry missions. But despite the advancements made since Apollo, heat flux prediction remains an imperfect science and engineers resort to safety factors to determine the TPS thickness. This goes at the expense of embarked payload, hampering, for example, sample return missions. 
Ground testing in plasma wind-tunnels is currently the only affordable possibility for both material qualification and validation of material response codes. The subsonic 1.2MW Inductively Coupled Plasmatron facility at the von Karman Institute for Fluid Dynamics is able to reproduce a wide range of reentry environments. This protocol describes a procedure for the study of the gas/surface interaction on ablative materials in high enthalpy flows and presents sample results of a non-pyrolyzing, ablating carbon fiber precursor. With this publication, the authors envisage the definition of a standard procedure, facilitating comparison with other laboratories and contributing to ongoing efforts to improve heat shield reliability and reduce design uncertainties.
The described core techniques are non-intrusive methods to track the material recession with a high-speed camera along with the chemistry in the reactive boundary layer, probed by emission spectroscopy. Although optical emission spectroscopy is limited to line-of-sight measurements and is further constrained to electronically excited atoms and molecules, its simplicity and broad applicability still make it the technique of choice for analysis of the reactive boundary layer. Recession of the ablating sample further requires that the distance of the measurement location with respect to the surface is known at all times during the experiment. Calibration of the optical system of the applied three spectrometers allowed quantitative comparison. At the fiber scale, results from a post-test microscopy analysis are presented.

Development of new ablative materials and their numerical modeling requires extensive experimental investigation. This protocol describes procedures for material response characterization in plasma flows with the core techniques being non-intrusive methods to track the material recession along with the chemistry in the reactive boundary layer by emission spectroscopy.

Ablative Thermal Protection Systems (TPS) allowed the first humans to safely return to Earth from the moon and are still considered as the only solution ...

Non-equilibrium Microwave Plasma for Efficient High Temperature Chemistry

A flowing microwave plasma based methodology for converting electric energy into internal and/or translational modes of stable molecules with the purpose of efficiently driving non-equilibrium chemistry is discussed. The advantage of a flowing plasma reactor is that continuous chemical processes can be driven with the flexibility of startup times in the seconds timescale. The plasma approach is generically suitable for conversion/activation of stable molecules such as CO2, N2 and CH4. Here the reduction of CO2 to CO is used as a model system: the complementary diagnostics illustrate how a baseline thermodynamic equilibrium conversion can be exceeded by the intrinsic non-equilibrium from high vibrational excitation. Laser (Rayleigh) scattering is used to measure the reactor temperature and Fourier Transform Infrared Spectroscopy (FTIR) to characterize in situ internal (vibrational) excitation as well as the effluent composition to monitor conversion and selectivity.

This article describes a flowing microwave reactor that is used to drive efficient non-equilibrium chemistry for the application of conversion/activation of stable molecules such as CO2, N2 and CH4. The goal of the procedure described here is to measure the in situ gas temperature and gas conversion.

A flowing microwave plasma based methodology for converting electric energy into internal and/or translational modes of stable molecules with the purpose ...

Chemistry

Optimization, Test and Diagnostics of Miniaturized Hall Thrusters

Miniaturized spacecraft and satellites require smart, highly efficient and durable low-thrust thrusters, capable of extended, reliable operation without attendance and adjustment. Thermochemical thrusters which utilize thermodynamic properties of gases as a means of acceleration have physical limitations on their exhaust gas velocity, resulting in low efficiency. Moreover, these engines demonstrate extremely low efficiency at small thrusts and may be unsuitable for continuously operating systems which provide real-time adaptive control of the spacecraft orientation, velocity and position. In contrast, electric propulsion systems which use electromagnetic fields to accelerate ionized gases (i.e., plasmas) do not have any physical limitation in terms of exhaust velocity, allowing virtually any mass efficiency and specific impulse. Low-thrust Hall thrusters have a lifetime of several thousand hours. Their discharge voltage ranges between 100 and 300 V, operating at a nominal power of &lt;1 kW. They vary from 20 to 100 mm in size. Large Hall thrusters can provide fractions of millinewton of thrust. Over the past few decades, there has been an increasing interest in small mass, low power, and high efficiency propulsion systems to drive satellites of 50-200 kg. In this work, we will demonstrate how to build, test, and optimize a small (30 mm) Hall thruster capable of propelling a small satellite weighing about 50 kg. We will show the thruster operating in a large space environment simulator, and describe how thrust is measured and electric parameters, including plasma characteristics, are collected and processed to assess key thruster parameters. We will also demonstrate how the thruster is optimized to make it one of the most efficient small thrusters ever built. We will also address challenges and opportunities presented by new thruster materials.

Here, we present a protocol to test and optimize space propulsion systems based on miniaturized Hall-type thrusters.

Miniaturized spacecraft and satellites require smart, highly efficient and durable low-thrust thrusters, capable of extended, reliable operation without ...

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.

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.

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 ...

Magnetic Resonance-Guided High Intensity Focused Ultrasound Generated Hyperthermia: A Feasible Treatment Method in a Murine Rhabdomyosarcoma Model

Magnetic resonance-guided high intensity focused ultrasound (MRgHIFU) is an established method for producing localized hyperthermia. Given the real-time imaging and acoustic energy modulation, this modality enables precise temperature control within a defined area. Many thermal applications are being explored with this noninvasive, nonionizing technology, such as hyperthermia generation, to release drugs from thermosensitive liposomal carriers. These drugs can include chemotherapies such as doxorubicin, for which targeted release is desired due to the dose-limiting systemic side effects, namely cardiotoxicity. Doxorubicin is a mainstay for treating a variety of malignant tumors and is commonly used in relapsed or recurrent rhabdomyosarcoma (RMS). RMS is the most common solid soft tissue extracranial tumor in children and young adults. Despite aggressive, multimodal therapy, RMS survival rates have remained the same for the past 30 years. To explore a solution for addressing this unmet need, an experimental protocol was developed to evaluate the release of thermosensitive liposomal doxorubicin (TLD) in an immunocompetent, syngeneic RMS mouse model using MRgHIFU as the source of hyperthermia for drug release.

Presented here is a protocol to use controlled hyperthermia, generated by magnetic resonance-guided high intensity focused ultrasound, to trigger drug release from temperature-sensitive liposomes in a rhabdomyosarcoma mouse model.

Magnetic resonance-guided high intensity focused ultrasound (MRgHIFU) is an established method for producing localized hyperthermia. Given the real-time ...

Cancer Research

Electric and Magnetic Field Devices for Stimulation of Biological Tissues

Electric fields (EFs) and magnetic fields (MFs) have been widely used by tissue engineering to improve cell dynamics such as proliferation, migration, differentiation, morphology, and molecular synthesis. However, variables such stimuli strength and stimulation times need to be considered when stimulating either cells, tissues or scaffolds. Given that EFs and MFs vary according to cellular response, it remains unclear how to build devices that generate adequate biophysical stimuli to stimulate biological samples. In fact, there is a lack of evidence regarding the calculation and distribution when biophysical stimuli are applied. This protocol is focused on the design and manufacture of devices to generate EFs and MFs and implementation of a computational methodology to predict biophysical stimuli distribution inside and outside of biological samples. The EF device was composed of two parallel stainless-steel electrodes located at the top and bottom of biological cultures. Electrodes were connected to an oscillator to generate voltages (50, 100, 150 and 200 Vp-p) at 60 kHz. The MF device was composed of a coil, which was energized with a transformer to generate a current (1 A) and voltage (6 V) at 60 Hz. A polymethyl methacrylate support was built to locate the biological cultures in the middle of the coil. The computational simulation elucidated the homogeneous distribution of EFs and MFs inside and outside of biological tissues. This computational model is a promising tool that can modify parameters such as voltages, frequencies, tissue morphologies, well plate types, electrodes and coil size to estimate the EFs and MFs to achieve a cellular response.

This protocol describes the step-by-step process to build both electrical and magnetic stimulators used to stimulate biological tissues. The protocol includes a guideline to simulate computationally electric and magnetic fields and manufacture of stimulator devices.

Electric fields (EFs) and magnetic fields (MFs) have been widely used by tissue engineering to improve cell dynamics such as proliferation, migration, ...

Bioengineering

In Vitro and In Vivo Delivery of Magnetic Nanoparticle Hyperthermia Using a Custom-Built Delivery System

Hyperthermia has long been used in the treatment of cancer. Techniques have varied from the intra-tumoral insertion of hot iron rods, to systemically delivered tumor antibody-targeted magnetic nanoparticles, at temperatures from 39 &#730;C (fever-level) to 1,000 &#730;C (electrocautery) and treatment times from seconds to hours. The temperature-time relationship (thermal dose) dictates the effect with high thermal doses resulting in the tissue ablation and lower thermal doses resulting in sublethal effects such as increased blood flow, accumulation of drugs and immune stimulation. One of the most promising current medical therapies is magnetic nanoparticle hyperthermia&#160; (mNPH). This technique involves activating magnetic nanoparticles, that can be delivered systemically or intratumorally, with a non-invasive, non-toxic alternating magnetic field. The size, construct and association of the magnetic nanoparticles and the frequency and field strength of the magnetic field are major heating determinants. We have developed sophisticated instrumentation and techniques for delivering reproducible magnetic nanoparticle hyperthermia in large and small animal models and cultured cells. This approach, using continuous, real time temperature monitoring in multiple locations, allows for the delivery of well-defined thermal doses to the target tissue (tumor) or cells while limiting non-target tissue heating. Precise control and monitoring of temperature, in multiple sites, and use of the industry standard algorithm (cumulative equivalent minutes at 43 &#730;C /CEM43), allows for an accurate determination and quantification of thermal dose. Our system, which allows for a wide variety of temperatures, thermal doses, and biological effects, was developed through a combination of commercial acquisitions and inhouse engineering and biology developments. This system has been optimized in a manner that allows for the rapid conversion between ex vivo, in vitro, and in vivo techniques. The goal of this protocol is to demonstrate how to design, develop and implement an effective technique and system for delivering reproducible and accurate magnetic nanoparticle therapy (mNP) hyperthermia.

This protocol presents techniques and methodology necessary for the accurate delivery of magnetic nanoparticle hyperthermia using a sophisticated delivery and monitoring system.

Hyperthermia has long been used in the treatment of cancer. Techniques have varied from the intra-tumoral insertion of hot iron rods, to systemically ...

Medicine

Propulsion and Thrust

Source: Alexander S Rattner; Department of Mechanical and Nuclear Engineering, The Pennsylvania State University, University Park, PA
Aircraft, rockets, and ships produce propulsion by accelerating surrounding fluid or high temperature combustion products to high velocity. Because of the principle of conservation of momentum, the increased fluid velocity results in an effective thrust force on the vehicle. The thrust capabilities of propulsion systems are often measured with static thrust tests. In these tests, propulsion systems are mounted and operated on fixed, instrumented platforms, and the holding force on the mounts is measured as the thrust
In this experiment, a small-scale static thrust measurement facility will be constructed and modeled. The thrust curves for two model aircraft motors and propeller systems and a computer cooling fan will be measured. Thrust efficiencies will also be evaluated (thrust force / electrical power input). Measured thrust values will be compared with theoretical predictions based on measured air velocities.

Aircraft/Rocket/Ship Propulsion; Static Thrust Measurement

Source: Alexander S Rattner; Department of Mechanical and Nuclear Engineering, The Pennsylvania State University, University Park, PA
Aircraft, rockets, ...