The Farnsworth fusor is one of the earliest practical designs to generate fusion. It was first proposed by Philio T. Farnsworth in the 1930's to create nuclear fusion with the ultimate goal to develop it for fusion power. The design has however several inherent constraints to the efficiency which makes it unusable for designs with a high net power production. The relatively simple Farnsworth fusor design has however proven to be very usable as a source for fast neutrons (when using D-D or D-T).
As an initial step to nuclear fusion Radiant Matter Research decided first constructed a Farnsworth fusor to build, design and test all the necessary equipment later required for the Polywell project. Also the Farnsworth fusor has been build by several people and a good information resource on these fusion reactors is available at fusor.net.
So far the RMR Farnsworth fusor has undergone several iterations. The main properties of each version are listed in the table below:
| RMR-FF1 reactor | RMR-FF2 reactor | RMR-FF3 reactor | RMR-FF4 reactor | RMR-FF5 reactor | |
|---|---|---|---|---|---|
| Lowest pressure | $6\cdot10^{-2}$ mbar | $6\cdot10^{-2}$ mbar | $<1\cdot10^{-3}$ mbar | $<1\cdot10^{-3}$ mbar | $3\cdot10^{-7}$ mbar |
|
Vacuum chamber smallest diameter |
76mm | 130mm | 130mm | 130mm | 300mm |
| Radiation monitoring | $\beta+\gamma$ | $\beta+\gamma$ |
$\alpha + \beta + \gamma$ |
$\beta+\gamma$ fast neutrons |
$\alpha + \beta+\gamma$ fast, thermal neutrons extensive dosimetry |
| Maximum voltage | ~1000V | 8kV (4kV usable) | 8kV (4kV usable) | 70kV (35kV usable) | 50kV |
| Maximum power | unknown | 400W | 400W | 350W | 300W |