microwave heating

[ohiovr]

How do microwaves heat plasma?

[hanelyp]

If the microwave is close to the cyclotron frequency of a charged particle in a magnetic field it couples in resonance and can heat it easily. Off resonance the push is likely to alternate increasing and decreasing particle energy, and depends on thermalizing collisions for net heating.

[ohiovr]

If the microwave is close to the cyclotron frequency of a charged particle in a magnetic field it couples in resonance and can heat it easily. Off resonance the push is likely to alternate increasing and decreasing particle energy, and depends on thermalizing collisions for net heating.

Hi Hanelyp,

I calculated the gyrofrequency to be in the megahertz range for ions. I wasn't sure so I also tried this calculator and got the same numbers:

http://www.vk2zay.net/calculators/cyclotron.php

I used a deuteron in a single tesla field.

[ohiovr]

the gyrotrons in ITER are supposed to operate at around 170 ghz, which is a 1000 times higher than their gyrofrequency at 17 teslas...maybe it can work as a harmonic frequency?

[D Tibbets]

Hear say is that microwave oven frequencies of ~ 4-8 Mhtz works. EMC2 did use a microwave magnatron to help heat the plasma in the past. If the charged particle needs to be in a magnetic field for resonance heating, it begs the question of how microwaves heat in the B field free internaql Wiffleball space. I suppose that the electrons at their turnaround point are susceptible to microwave heating. Essentially the potential well is maintained by heating the electrons and the potential well "heats" the ions.

Another question is if magnetic fields are needed, how does a microwave oven produce plasmas with cut grapes, smoking matches, etc. ?

Dan Tibbets

[ohiovr]

Microwaves and mhz don't go together. 10 mhz is not a microwave signal.

[hanelyp]

As I understand it you need resonance or collisions (aka electrical resistance) for RF/microwave heating.

[D Tibbets]

Microwaves and mhz don't go together. 10 mhz is not a microwave signal.

OK, so I was only off by a factor of ~ 1000.

http://hypertextbook.com/facts/1998/HowardCheung.shtml

Lets see, at light speed of 300,000,000 M/S and a frequency of 3 Ghtz, light would travel ~ 0.1 M/ cycle or ~ 100,000 micro meter wave length. Still not exactly microwaves (wavelengths of a few micrometers), but they did not consult me when they dreamed up the name for radar ovens.
Actually the infrared spectrum is mostly in the ~0.65 to many micro meter wavelengths.

Dan Tibbets

[ohiovr]

As I understand it you need resonance or collisions (aka electrical resistance) for RF/microwave heating.

Hi hanelyp,

Do you suppose it would be possible to heat a plasma with dielectric heating if that makes any sense. Like a plasma between two plates that alternate in charge?