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: New Vacuum Chamber
Date: Aug 31, 3:04 am
Poster: Dave Cooper

On Aug 31, 3:04 am, Dave Cooper wrote:

> also I am interested in fitting a magnetron from a microwave oven into the fusor and would like to hear any practical advice on the subject like suitable aiming angles, rf protection for the grid supplies (rf blocking inductors?)
The grid supplies can probably be protected with some ferrite bead type inductors - be sure to use those designed for a few GHz.

However, I would expect the grids will be a massive load on the Magnetron, much the same as metallic items in the Microwave oven are.

> and whether it will have any effect as it is tuned for water frequencies not Hydrogen frequencies.
Good question. The magnetron operates at 2.45 GHz which gives a wavelength of about 12 cm. Assuming a standing wave within the fusor, there could be some significant E fields transverse to the magnetron's output axis. Assuming a reasonable SWR value....possibly as high as a few kV/cm. But.... neither electrons nor hydrogen ions would be able to absorb all this energy since their mass would restrict them to oscillating in a much smaller potential "well". The polar aspect of the neutral H20 molecule would have it oscillating (more accurately - swinging) at the magnetron frequency, but since Hydrogen is not polar, I doubt whether it would do much at all, unless it was an ion, in which case it would oscillate around a moving point while in the RF field of the magnetron.

> Also a simple way of measuring approximate SWR into the chamber would be nice too

> Regards
> Mark Harriss
A microwave diode on a stalk in the coupling waveguide would measure the voltage at that point. As Jim Lux observes, you would need the slotted line to find the voltage profile, to get the SWR.

Dave Cooper