Power Supply

September 8, 2013 at 8:18 pm

 In the Fusor, a DC high voltage, low current supply is essential.  The voltage is used to create a massive potential difference between an inner grid placed inside the Fusor chamber and the chamber wall. The negative lead of a power supply is channelled through a feedthrough in one of the vacuum chamber’s ports and is welded inside to the inner grid.  The positive lead of the supply/transformer is then linked to the chamber and grounded.  The voltage between the chamber and the inner grid causes deuterium atoms (proton+neutron+electron) to lose their electron, becoming positively ionised.  This causes the nuclei to fly toward the inner grid (negative) and fuse.


For the high voltage part of the Fusor, the following are needed:

– A DC high voltage power supply/transformer

– A vacuum tight feedthrough

– An inner grid or wire to form an inner grid

Diagram of my proposed High Voltage setup

Diagram of my proposed High Voltage setup

Power supply Equipment – Technical specs

High voltage supply (approximate cost €500-1000): The high voltage supply for a Fusor must be capable of reaching at least 25kv and 10ma, but an optimum supply would be one that can reach 60kv and 50ma to provide a power reserve capacity as the best voltage and current for operating a Fusor is usually around 40kv@30ma.  The supply must be fully variable, not 1/2/5kv step-ups. A Fusor can work at a minimum power of around 250 watts(25kv@10ma) to a maximum of around 3000 watts(60kv@50ma), but can go higher again. The supply itself needs to output a DC current and must be configured for positive ground, negative voltage output with a 220v AC input or adapter to adapt from the wall mains supply.  Tesla coil and spark coil based supplies cannot be used.  X-ray transformers can be used and any other type of transformers.  However, neon sign transformers usually do not provide a high enough voltage so they cannot be used.


Feed-through (approximate cost €80-200): A feed-through is required to connect the supply/transformer’s negative lead to the inner grid.  It is placed in a flange on one of the vacuum chambers’ ports. As the power supply could be outputting up to 60kv and 50ma, any feed-through used must be able to take that. Conflat fitting feed-throughs are the best, as they are specially fitted for a specified conflat flange or fitting size.


Inner grid (approximate cost €50-100): A spherical, hollow grid is placed in the center of the vacuum chamber. The negative lead of the power supply is conducted through a feedthrough into the chamber and welded to the grid.  These grids are nearly always constructed by acquiring a length of wire and then making multiple circles of the same shape and welding them together, or  finding a spherical piece of light wood or a balloon and shaping a grid around that and then burning the wood or popping the balloon, leaving a spherical, open grid.  The best material for the inner grid is tungsten, followed by tantalum, hafnium and molybdenum as these have the highest melting temperatures out of all the elements.  The grid can only be made of metal and the only thing required is a high melting point. The wire should also be around 0.5mm thick.