How do microwave plasmas work?

[sw2244]

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.

 

[berkeman]

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

 

[sw2244]

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

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?

 

[sw2244]

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.

 

[berkeman]

Thread closed temporarily for Moderation...

 

[anorlunda]

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.