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: Diodes?
Date: Sep 22, 10:56 am
Poster: Richard Hull

On Sep 22, 10:56 am, Richard Hull wrote:


This 100kv diode really doesn't exist! Most all single diodes over 1KV are really series strings of diodes in a single molded body. There is just no way you will find a silicon unit much over 30kv and even those are extremely expensive. (>$50.00 each)

Going straight for the throat in a single pass rectification step, you would have to purchase and series string several microwave oven diodes. This is the way to go. These oven diodes can be found in a number of specialized electronic vendor catalogs at a very afordable price under $5.00 each and at some hamfests for even less. Most all of these diodes are rated at 12kv piv, 300ma. I would think 10 in a string would do it.

There is a real problem here though. You should parallel each diode with about a 50-100 meg ohm special high voltage resistor and then the entire string should be under oil!

Complicated, yes, but anything else will most likely not last. Corona becomes a major problem and area of loss and failure in air operated systems over 30kv.

Your effort is laudable, but I would try a lower voltage first........say....30kv max and see how that does. You could use fewer diodes and work in air provided you used some HV silicone putty (electronics jobbers carry this stuff) over each air joint or connection. Naturally, a variac on the transformer primary side would let you bing up the high voltage slowly and safely from zero.

Richard Hull