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: x-ray supply
Poster: Richard Hull

On , Richard Hull wrote:

I have used an x-ray transformer and or supply starting with fusor IIIa over a year ago. I have used two different supplies and modified them as needed.

Most are only good for 20ma continuous at 60kv. The tube or kenetron types of yesteryear are the best, however a lot of fancy dancing will have to be done as most are "ground/case negative" supplies. Naturally, you will want a ground positive system.

My current supply is a dental x-ray unit and I have supplied my own silicon diodes in reverse to yield the positive ground supply. The center tap to ground lead of the H.T. transformer is open and brought to external terminals for a milliammeter. I have a 10ohm precision resistor across it and measure with a digital panel meter calibrated accordingly.

The X-ray supply is ideal from an insulation standpoint, but you better be ready to go in and out of it several times if you blow the solid state diodes. On mine, that means farting with 60 #10 machine screws and nuts and realigning a cork gasket while oil sloshes around as you shoehorn the HV deck into the liquid.

If you can get an old used xray supply, it is a great starting point, but you will almost certainly have to re-invent the wheel by a massive internal changeover and play with a lot of oil mess.

They are classic linear supplies,therefore, you can variac the H.T. transformer to span a smooth as silk 0-60,000 volts output.

Some nervous nellies will undoubtedly freak out over the PCBs so often found in these older tanked units.

PCBs are a non-issue with me as I realize you can wash in th' stuff. Just don't get it hot! This is important if you are soldering on the lifted out HV deck (making your modifications). The oil will be every where, make sure to clean the area to be soldered with a solvent extremely well and were an osha approved respirator while soldering and you are good to go.

Richard Hull