Fusion Message Board

In this space, visitors are invited to post any comments, questions, or skeptical observations about Philo T. Farnsworth's contributions to the field of Nuclear Fusion research.

Subject: Re: Another 2 cents on microwaves
Date: Aug 17, 5:01 pm
Poster: Jim Lux

On Aug 17, 5:01 pm, Jim Lux wrote:

>Wow, these two cents worth are adding up...
>Jim Lux wrote:
>>It would be the rare Gunn diode that is cheap and puts out more than a 100 mW

>You are missing the main point entirely, Jim. At $10/ pop, the low output Gunn diode might be the cheapest item in your experiment...by far. Phase synchonization is NOT an issue with widely seperated diodes focused on a plasma whose radius is signiicant in excess of the wave length, so long as the radiation is well absorbed, and all indications are positve for that.

Got it... Good point. However, is the plasma that much of an absorber, or is it conductive enough to reflect?

If you find that a 300 mW diode array gives you an order of magnitude more neutrons..well, then you have stumbled onto something really important.

Good point....

There are no simulation programs out there that are going to help you get anywhere near what a few extra hous of effort and a little luck might produce.

The simulation program was for trying to couple the microwave power into the plasma, not trying to predict what might happen once you've done it.

>>If you want to use microwave power, use cheap, readily available microwave oven magnetrons (>1kW for <$100). Just know what you are doing before you cook yourself.
>Again, its not the magnetron but the power supply and waveguide that is the problem.

Waveguide is just a tube of proper dimensions. The probe from the magnetron sticks into it, just like in an oven. Power supply is from the oven from which you snagged the magnetron. Magnetrons are easy to use, IFF, you don't care about waveform, frequency stability, etc... For radar you care, for heating, you don't...

>Not to mention the fact that an extra kW from a magnetron will fry your grid in less time than it took to answer that suggestion.

There is that, of course...


>Yes, the coupling part is tricky, but he plasma will relect incident power back roughly in proportion (ignoring resonance) to wavelength, so the Gunn diode gives you a factor of roughly 8 better chance of achieving good coupling

Do you have a basic reference work on that... I'm not up on coupling microwave power into a plasma (generally, I try to avoid plasmas with microwaves, except as in a TR switch).

>Forget simulation programs. If fusors could be simulated this forum would not exist and none of this would be of interest anyway.

Not for simulating the behavior of the plasma, but for simulating the EM field in your cavity. Even a rough sim would save a lot of tuning time trying to get your power distribution right.