The Farnsworth Fusor (Or: How to build a deuterium fusing nuclear reactor in your garage)

The Farnsworth Fusor (or Farnsworth-Hirsch Fusor) is the simplest way of achieving a sustained hydrogen fusing nuclear reaction. It can be achieved on a bench-top and uses electrical containment as opposed to the large scale magnetic containment of Tokamak. Patented in 1953 by Philo T Farnsworth (who also invented the cathode ray tube, the fundamental component of traditional televisions), the fusor is staggeringly simple in principle and can produce a continuous sustained nuclear reaction. Unfortunately it cannot produce more energy than is required to generate the containment and is therefore purely of interest as a scientific oddity.


A Farnsworth Fusor is based around the idea of containing and fusing deuterium in an electrical field. This is performed by using a spherical cathode (It can work with a diameter about 30 cm) and anode (diameter about 7.5 cm) pair. Both of these should be assembled as grid spheres of interlocking steel rings. The anode must be placed at the centre of the cathode within an evacuated chamber. If these are then connected to an electrical generator then a spherical particle accelerator is formed.

If a voltage is applied across these electrodes then any positively charged ions released into the chamber are going to be accelerated towards the anode. The acceleration will be proportional to the voltage applied across them. However, these particles miss the cathode and pass through the grid; their momentum then carries them towards the central point of the system, where everything collides.

Thus if ionised hydrogen is released (typically via two ion guns located at the edge of the chamber) into the system then the particles will accelerate towards the central point. Increasing the voltage applied increases the force, leading to an increase in temperature at the centre. This makes a relatively straightforward method for producing a Plasma - a point of extremely high temperature ionised gas

There is the problem of geometry here, unless the positioning of the spheres is perfect and the shape of the spheres ideal then the collision will not occur purely at the central point. However, increasing the voltage applied is a quick and effective way of compensating for any problems of manufacture.

To convert this system to a fusion reactor the force these particles apply must be increased. Swapping the hydrogen for deuterium increases the momentum of each particle, thereby increasing the force upon collision. After this all that is necessary is to kick the voltage up a little higher and the system can produce a star in a bottle.


This machine is incredible to observe since it produces sustained, controlled fusion reaction and was developed as the first stage in the great hot fusion dream of the 1950's. It has proved an ideal way to observe fusing plasmas in-situ but unfortunately the voltage applied will always take more energy than the fusion yield it produces. There are a few dangers in construction because it is a significant neutron radiation source (the most dangerous form of radiation). As such this can potentially make other things radioactive and requires significant safety equipment to run without endangering its users. But as such you can generate neutron radiation, and potentially neutron activation (alchemy!) at the flick of a switch.

The only difficult to acquire components are the power generator and the deuterium. If you can get your hands on these then all it takes is a practical mind and a workshop!

This should be your fourth investment after your Igor, Tesla coil and Jacob's ladder if you are truly serious in your plans to take over the world, obligatory in all modern castle/dungeon laboratories. Be the coolest mad scientist on the block - get a Farnsworth Fusor!

Note should also be taken that Hubert T Farnsworth of Futurama must have been based on this guy, theres just no question about it!

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