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: pulse mode operation
Date: Oct 26, 6:14 pm
Poster: Jim Lux

On Oct 26, 6:14 pm, Jim Lux wrote:

>First: transit time in not a real issue -- the transit time from fusor edge to fusor center for a deuteron in a 500 kV, 150mm radius fusor is on the order of less than 40 ns. It takes heroic efforts to get pulses anything like that short.

>Second: What kind of pulse voltage and current is Miley working on? I have not seen his paper on the subject, and would like a pointer to it.

He has written several papers on it which all appear to be similar to one another. He's talking voltages in the 100 kV range, and pulsed currents of a few Amps. Really high voltages don't buy you as much as increased current.
>Third: does anyone here have experience with rapid fire Marx generators? I want to build a setup with a Marx generator firing on order of 100 Hz, at about 300-400 J per pulse, with a peak voltage of approximately 600 kV. Could you also suggest a supplier of high voltage caps?

So you're talking a 40 kW output Marx, and a likely 100 kW power supply to run it. At high rep rates, hydrogen is preferred as the gas, because it quenches quickly, although at a low rate like 100 Hz, other gases (i.e. nitrogen, SF6, argon, air) would probably work as well, particularly if the gaps are purged.
For a discharge energy of 400 J at 600 kV (although I don't think you want this sort of voltage), you'll need an erected capacitance of 2.2 nF. If the stages are 30 kV, each stage will need 44 nF, storing about 20 J in each cap. Maxwell Labs has high rep rate caps in this sort of range. If you want to work at a bit lower energy per pulse, ceramic doorknob caps might work. Ceramite has 15 kV doorknobs at 10 nF (use 3 in series), and 40 kV doorknobs at 1.3 nF.

Another possibility would be to use an impulse transformer. A 10:1 or 15:1 step up might be effective, and makes the primary charging supply reasonable.