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: 100 kV technique
Date: Feb 25, 4:26 pm

On Feb 25, 4:26 pm, wrote:

>>However, why not generate your HV in the vacuum. Send in moderate HV AC through a conventional feedthrough, then either transformer it up or use a voltage multiplier, running inside the vacuum chamber.
>I've actually considered this technique myself but I think the cost of vacuum-rated electronic components and plus the additional chamber size and so on would be more expensive than the larger feedthrough.

Component issues might not be as bad as you think. Many electronic components are hermetically sealed. The real difference between space parts (which have to be vacuum compatible) and consumer is the testing, reliability (and documentation!), not the manufacturing process.

Send in the HV at say, 25 kV at a fairly high frequency (several 10's of kHz). You'd need 4 or 5 stages of diode multiplier with fairly small capacitors for filtering.
>>Most medical X-ray tubes >In fact, as I write this, I think that the Xray supply might be the ideal source, since they regulate the 100 mA current in the xray tube by varying the filament current, and hence the number of electrons. The same would apply in a dispenser cathode approach to a fusor.
>I agree with you on this -- it sounds like it would be a dandy way to do it, and much safer than mucking with it myself.

And probably cheaper... Xray supplies are regularly available (tubeless) on the surplus market
>>The only problem would be duty cycle.
>The fusor should come to steady state in that time frame, so you can do your science and get out. I don't think the duty cycle is necessarily a big deal.

However, if you are doing particle counting you might want longer run times to get more counts above the noise floor.