How do microwave plasmas work?

In summary, a plasma can be created in a waveguide by heating it up with microwave energy. The spark or ignition source is not necessary to keep the plasma going.
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I'm new to PF, I have an engineering background, but am trying to understand how microwave plasmas are generated. I'm trying to work out if a tuned microwave waveguide can create a plasma in a specific point in the waveguide say over 30 seconds as the microwave energy heats up the waveguide thus causing the plasma to occur? Or does the plasma need a spark or ignition source to start the air ionizing and then the microwave keeps it going/enhances it?

Once the plasma is going, is the spark/ignition source required to keep operating to keep the plasma going, or is the plasma self sustaining?

Just trying to understand.
 
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  • #2
sw2244 said:
I'm new to PF, I have an engineering background, but am trying to understand how microwave plasmas are generated. I'm trying to work out if a tuned microwave waveguide can create a plasma in a specific point in the waveguide say over 30 seconds as the microwave energy heats up the waveguide thus causing the plasma to occur? Or does the plasma need a spark or ignition source to start the air ionizing and then the microwave keeps it going/enhances it?

Once the plasma is going, is the spark/ignition source required to keep operating to keep the plasma going, or is the plasma self sustaining?

Just trying to understand.
Welcome to the PF.

Could you say more about what type of plasma application you have in mind? Here is a general Google search with various types of plasmas and generation techniques discussed:

https://www.google.com/search?q=how...enerated&ie=utf-8&oe=utf-8&client=firefox-b-1

And this hit may be closer to what you are asking about?

https://inis.iaea.org/collection/NCLCollectionStore/_Public/20/058/20058332.pdf

:smile:
 
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berkeman said:
Welcome to the PF.

Could you say more about what type of plasma application you have in mind? Here is a general Google search with various types of plasmas and generation techniques discussed:

https://www.google.com/search?q=how...enerated&ie=utf-8&oe=utf-8&client=firefox-b-1

And this hit may be closer to what you are asking about?

https://inis.iaea.org/collection/NCLCollectionStore/_Public/20/058/20058332.pdf

:smile:
Hi

Thanks for your response. The main use would be ( eventually... ) alcohol reforming into hydrogen.

I have done a fair bit of reading, but what escaped me was the understanding of the basic mechanism behind how it all worked. Most of what I could find was university/reserach papers but they all seemed start from a high level and assumed the reader had a certain knowledge of microwave plasmas and how they worked, which I lack at this time, but want to build up.

I also wanted to build a basic un-tuned / "rough" plasma generator using a 2.45 Ghz plasmatron and my metal fabriaction skills to build a simple waveguide-based plasma system without need for circulators and isolators etc. It seems many people use software like HFSS to design their plasma systems, but what I'm looking for is basic "boot up" knowledge to get a plamsa-newbie like me going, and then to happily read more as I learn, but its a bit fo a case as I'm not really sure what I don't know...if you know what I mean...buty I guess you have to start somewhere... :-)

I will read the links youve sent ..thank you.

Maybe this fills in the gaps a bit?
 
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OK, I've had a chance to read up on plasmas some more, and now understand a lot better. I also have a much healthier respect for them in terms of safety.

I want to build a very rough plasma generator using a 2.45 Ghz plasmatron with a WR284 ( or WR430 ) simple tapered waveguide , hopefully without the need for circulators and isolators etc. I realize I may destroy a couple of cheap microwave oven magnetrons in the process. What I'm lacking now is the best method for calculating how I'd set up the waveguide in terms of how many wavelengths long it needs to be, where you would place the magnetron, where you would place the plasma opening, how big would the opening be etc.

Woud reading university course notes if I could find them help, or is design of this type of gear all done by off the shelf software now?

Any help appreciated.
 
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Thread closed temporarily for Moderation...
 
  • #6
You say you're aware of the safety problems. We can't judge that. However, this is a public forum, and we have no knowledge of the qualifications of anyone who might read this. Playing with microwave magnetrons is inherently dangerous. Therefore, we can't allow public discussion on PF.

Thread closed.

However, according to this reference https://searchworks.stanford.edu/view/11993843 there is a book that tells everything about plasma reforming of alcohol, including how to build miniature plasma generators.
 
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1. How do microwave plasmas work?

Microwave plasmas are created by using microwaves to ionize gas molecules, creating a plasma state. The microwaves pass through the gas and cause the electrons to become excited and move rapidly. This creates a high-energy environment where the gas molecules break apart and form a plasma.

2. What is the purpose of using microwaves in plasma formation?

Microwaves are used because they have a short wavelength and high frequency, which allows them to penetrate the gas more easily and efficiently ionize the gas molecules. This results in a more stable and controllable plasma compared to other methods.

3. How does the power of the microwaves affect the plasma?

The power of the microwaves has a direct impact on the properties of the plasma, such as its temperature and density. Higher power levels can create a more intense and hotter plasma, while lower power levels can create a cooler and less dense plasma.

4. What types of gases can be used in microwave plasma generation?

Various gases can be used, such as argon, helium, nitrogen, and oxygen. Different gases can result in different properties of the plasma, such as color and temperature. The choice of gas is dependent on the desired outcome and application of the plasma.

5. Can microwave plasmas be used for industrial purposes?

Yes, microwave plasmas have a wide range of industrial applications, such as surface modification, thin film deposition, and material synthesis. They are also used in plasma etching and cleaning processes in the semiconductor industry. The ability to control and tailor the properties of the plasma makes it a valuable tool in various industries.

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