Name: how to ignite an atmospheric pressure microwave plasma torch without any additional igniters
Uploaded: 2015-04-16T15:00:00
Description: Watch this Scientific Journal Video about How to Ignite an Atmospheric Pressure Microwave Plasma Torch without Any Additional Igniters at JoVE.com

The authors would like to thank the Arbeitsgemeinschaft industrieller Forschungsvereinigungen &#8222;Otto von Guericke&#8220; e.V., AiF (German Federation of Industrial Research Associations) and the Deutsche Forschungsgemeinschaft, DFG (German Research Foundation) for partly funding the presented work under contract number 14248 and STR 662/4-1, respectively.

1. Measurement of the Magnetron
Note: The schematic of the experimental setup for measuring the magnetron is depicted in Figure 1A.
<ol>
	<li>Connect the magnetron to an insulator consisting of a circulator and a water load with 10 screws.</li>
	<li>Connect the insulator to a directional coupler with 10 screws.</li>
	<li>Connect the directional coupler to a second water load with 10 screws.</li>
	<li>Supply all water loads with water.</li>
	<li>Calibrate the spectrum analyze...

<ol>
	<li>Hong, Y. C., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Microwave+plasma+torch+abatement+of+NF3+and+SF6.">Microwave plasma torch abatement of NF3 and SF6.</a> Phys. Plasma. 13, 033508 (2006).</li><li>Kabouzi, Y., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Abatement+of+perfluorinated+compounds+using+microwave+plasmas+at+atmospheric+pressure.">Abatement of perfluorinated compounds using microwave plasmas at atmospheric pressure.</a> J. Appl. 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Technol. 11, 135-141 (2002).</li><li>Korzec, D., Werner, F., Winter, R., Engemann, J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Scaling+of+microwave+slot+antenna+(SLAN):+a+concept+for+efficient+plasma+generation.">Scaling of microwave slot antenna (SLAN): a concept for efficient plasma generation.</a> Plasma Sources Sci. 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D. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Observation+of+microwave+volume+plasma+ignition+in+ambient+air.">Observation of microwave volume plasma ignition in ambient air.</a> Plasma Sources Sci. Technol. 21 (3), 035009 (2012).</li><li>Baeva, M., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Puls+microwave+discharge+at+atmospheric+pressure+for+NOx+decomposition.">Puls microwave discharge at atmospheric pressure for NOx decomposition.</a> Plasma Sources Sci. 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The presented movie explains how an ignition of an atmospheric pressure microwave plasma without any additional igniters can be realized, the basic principles of this microwave plasma torch, its adjustment, the ignition process of the plasma and its stable and continuous operation. As described in the introduction, there are already different kinds of microwave plasma torches but none of those provide an ignition of the plasma without any additional igniters as well as stable and continuous plasma operation.
<p class...

Atmospheric pressure microwave plasma torches offer a variety of different applications. On one hand they can be used for chemical volume processes and on the other hand their afterglow plasma can be applied for the treatment of surfaces. As surface treatment processes the treatment to increase the adhesion of glue, paint or lacquer or the decontamination or sterilization of surfaces can be named. The hot and reactive plasma itself can be used for volume processes like the decomposition of waste gases 1&#8211;7. These waste gases are harmful, contribute to the global warming and can hardly be degraded conventionally. However, they are needed in growing industrial sectors such as the semiconductor branch. Other applications are chemical synthesis like the dissociation of CO2 to CO and O2 or CH4 to carbon and hydrogen 8,9. Surplus electrical energy from renewable energy sources can be used to dissociate CO2 into CO and O2. The CO can be processed further to higher hydrocarbons which can be used as synthetic fuels for transportation, as platform chemicals for the chemical industry or as chemical storage.
There are some microwave plasma torches but most of them have disadvantages: They only have very small plasma volumes, need additional igniters, need cooling of the plasma reactor or can only be operated in pulsed mode 10&#8211;18. The microwave plasma torch presented in this movie offers an ignition of the plasma solely with the provided microwave power with no additional igniters as well as a stable and continuous operation without any cooling of the plasma reactor for a broad range of operation parameters and can be used for all of the above mentioned applications. The microwave plasma torch is based on a combination of two resonators: a coaxial one and a cylindrical one. The cylindrical resonator has a low quality and is operated in the well-known E010-mode with the highest electrical field in its center. The coaxial resonator is located below the cylindrical resonator and consists of a movable metallic nozzle in combination with a tangential gas supply. The high quality of the coaxial resonator exhibits a very narrow but deep resonance curve. Due to the high quality of the coaxial resonator a high electrical field can be reached which is required for the ignition of the plasma. However, the high quality of the coaxial resonator is associated with a very narrow resonance curve and therefore the resonance frequency has to perfectly match the frequency of the supplied microwave. Since the resonance frequency shifts after ignition of the plasma due to the permittivity of the plasma, the microwave can no longer penetrate into the coaxial resonator. For the continuous operation of the plasma the cylindrical resonator with a low quality and a broad resonance curve is needed.
An additional axial gas supply via the metallic nozzle of the coaxial resonator is possible. The plasma is ignited and confined in a microwave-transparent tube, for example a quartz tube. The permittivity of the quartz tube also affects the resonance frequency. Since the quartz has a permittivity of &#62; 1, the volume of the cylindrical resonator is virtually enlarged which leads to a lower resonance frequency. This phenomenon has to be considered when the dimensions of the cylindrical resonator are designed. A detailed discussion about how the resonance frequency is affected by the inserted quartz tube can be found in Reference 23. If a long and extended quartz tube is used, this can also act as the reaction chamber for the volume processes. However, for surface treatments the plasma can also be shaped differently by different kind of orifices. The microwave is supplied via a rectangular waveguide from the magnetron. To avoid noise nuisance the use of a low ripple magnetron is recommended. The magnetron which is used in the movie is a low ripple one.
For the ignition of the plasma the high quality coaxial resonator is used while a stable and continuous operation is provided by the cylindrical resonator. To achieve the ignition of the plasma by the high quality coaxial resonator the resonance frequency of this resonator has to perfectly match the frequency of the microwave provided by the used magnetron. Since all magnetrons do not emit their microwave frequency at exactly the nominal frequency and since the frequency is dependent on the output power, the magnetron has to be measured with a spectrum analyzer. The resonance frequency of the coaxial resonator can be adjusted by moving the metallic nozzle up and down. This resonance frequency can be measured and thereby also adjusted to the sending frequency of the used magnetron with a network analyzer. To reach the high electrical field at the tip of the nozzle, required for the ignition of the plasma, a three stub tuner is needed in addition. This three stub tuner is a commonly used microwave component. The three stub tuner is mounted between the microwave plasma torch and the magnetron. After the resonance frequency of the coaxial resonator is adjusted, the forward power is maximized and the reflected power minimized by iteratively adjusting the stubs of the three stub tuner.
After having adjusted the resonance frequency of the coaxial resonator as well as having maximized the forward powers by means of the three stub tuner, the plasma of the microwave plasma torch can be ignited when the microwave plasma torch is connected to a magnetron. For the ignition of the plasma a minimum microwave power of about 0.3 to 1 kW is sufficient. The plasma ignites in the coaxial resonator. After the ignition of the plasma the resonance frequency of the coaxial resonator is shifted due to the dielectric permittivity of the plasma and the microwave can no longer penetrate into the coaxial resonator. Thus, the plasma switches from the coaxial mode into its much more extended cylindrical mode burning freely-standing above the metallic nozzle in the center of the cylindrical resonator. Since the quality of the cylindrical mode is very low and therefore exhibits a broad resonance curve, the microwave can still penetrate into the cylindrical resonator despite of the shift of the resonance frequency due to the dielectric permittivity of the plasma. Thus, a continuous and stable operation of the plasma in the cylindrical mode is provided by the microwave plasma torch. However, to reach a complete absorption of the supplied microwave power, the stubs of the three stub tuner have to be readjusted. Otherwise the supplied microwave power is not completely absorbed by the plasma but some percentage of the provided microwave is reflected and absorbed by the water load.
To examine the ignition of the plasma in the coaxial mode and then its transition into the extended cylindrical mode, the plasma ignition is observed by a high speed camera.
The presented movie will show how the frequency dependence of the magnetron is measured, the resonance frequency of the coaxial resonator is adjusted, how the forward power is maximized and how the plasma is ignited by the supplied microwave power. The high speed camera recording is shown as well.

<table border="0" cellpadding="0" cellspacing="0">
	<tbody>
		<tr>
			<td>2 kW magnetron</td>
			<td>Muegge&#160;</td>
			<td>MH2000S 211BA</td>
			<td></td>
		</tr>
		<tr>
			<td>2 kW power supply</td>
			<td>Muegge&#160;</td>
			<td>ML2000D-111TC</td>
			<td></td>
		</tr>
		<tr>
			<td>insulator - circulator with water load</td>
			<td>Muegge&#160;</td>
			<td>MW1003A-210EC</td>
			<td></td>
		</tr>
		<tr>
			<td>water load</td>
			<td>Muegge&#160;</td>
			<td>MW1002E-260EC</td>
			<td></td>
		</tr>
		<tr>
			<td>three stub tuner</td>
			<td>Muegge&#160;</td>
			<td>MW2009A-260ED</td>
			<td></td>
		</tr>
		<tr>
			<td>orifices</td>
			<td>homemade</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>microwave plasma torch</td>
			<td>homemade</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>spectrum analyzer</td>
			<td>Agilent</td>
			<td>E4402B</td>
			<td></td>
		</tr>
		<tr>
			<td>network analyzer</td>
			<td>Anritsu</td>
			<td>MS4662A</td>
			<td></td>
		</tr>
		<tr>
			<td>calibration kit</td>
			<td>Anritsu</td>
			<td>model 3753</td>
			<td></td>
		</tr>
		<tr>
			<td>directional coupler</td>
			<td>homemade</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>20 dB attenuator</td>
			<td>Weinschee engineering</td>
			<td>20 dB AA57u8</td>
			<td></td>
		</tr>
		<tr>
			<td>coaxial to rectangular wave guide transition</td>
			<td>Muegge&#160;</td>
			<td>MW5002A-260YD</td>
			<td></td>
		</tr>
		<tr>
			<td>adaptor 7-16 to N connector</td>
			<td>Teleg&#228;rtner</td>
			<td>7-16/N Adaptor</td>
			<td></td>
		</tr>
		<tr>
			<td>coaxial cable</td>
			<td>Rosenberger Hochfrequenztechnik</td>
			<td>LU7_070_800</td>
			<td></td>
		</tr>
		<tr>
			<td>high speed camera</td>
			<td>Photron</td>
			<td>fastcam SA5</td>
			<td></td>
		</tr>
		<tr>
			<td>lens</td>
			<td>Revueflex</td>
			<td>makro revuenon 1:3.5/28mm</td>
			<td></td>
		</tr>
		<tr>
			<td>local gas ventilation</td>
			<td>Industrievertrieb Henning</td>
			<td>ACD220</td>
			<td></td>
		</tr>
		<tr>
			<td>UV protection glasses</td>
			<td>uvex</td>
			<td>HC-F9178265</td>
			<td></td>
		</tr>
		<tr>
			<td>microwave leakage tester</td>
			<td>conrad electronic</td>
			<td>not available</td>
			<td></td>
		</tr>
		<tr>
			<td>microwave survey meter</td>
			<td>Holaday industries inc.</td>
			<td>81273</td>
			<td></td>
		</tr>
	</tbody>
</table>

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.

To provide a plasma ignition without any additional igniters as well as a stable and continuous plasma operation a high quality coaxial resonator with an adjustable resonance frequency was combined with a low quality cylindrical resonator to a microwave plasma torch. The schematic of this plasma torch is presented in Figure 3. The plasma is confined into a microwave-transparent tube, here a quartz tube. This tube can act as a reaction chamber for volume plasma processes or a plasma brush for surface trea...

Watch this Scientific Journal Video about How to Ignite an Atmospheric Pressure Microwave Plasma Torch without Any Additional Igniters at JoVE.com

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

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 ...

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