THE HAYLETT FUSION REACTOR PROJECT
How can we prove that Nuclear Fusion is occurring?
There are several ways of determining whether or not Deuterium-Deuterium fusion is occurring:
1. Detecting the products of fusion – principally Tritium and He3.
2. Detecting the 2.45MeV neutrons produced by the fusion.
3. Using the neutrons produced to activate a material such as silver, and then
identifying the new element created by measuring the energy level of the
gamma radiation it gives off and/or its half-life. (It could be argued that this is
just another way of detecting fusion by proving that neutrons are produced.)
The first way, detecting the Tritium and Helium 3 produced by the fusion, is unfortunately not practical for the amateur because of the infinitesimal quantities produced in a fusor. Even very sophisticated gas analyzers would not likely detect their presence because the concentrations are so low..
The second way, detecting the high energy neutrons produced by the fusion, is certainly not easy, but it is do-able. We are able to measure the neutrons produced by fusion using two different types of Neutron Detector.
Our He3 neutron detector measures only thermal (low energy) neutrons, so we use several inches of paraffin to slow down (moderate) the 2.45 MeV neutrons from the fusion reaction until their energy level is low enough for them to be detected by the He3 tube.This is the method that we first employed, and it is still our only way of measuring the rate of fusion on a second-by second basis.
However, it could be argued that our He3 detector could potentially be fooled by EMI (electrical interference) or by high energy gamma radiation causing false counts. A combination of the operating voltage selected, and the threshold level adjustment, together with extensive electrical shielding, have essentially eliminated both potential sources of interference. This has been experimentally verified by operating our fusor at the highest voltages and currents practicable, but without Deuterium. When we did this,only background neutrons (mostly from cosmic rays) were detected – typically around 17 per minute. We are therefore confident that our He3 Neutron detector readings are as accurate as possible. (Background readings are always subtracted from our neutron readings when doing fusion, even though they are not really significant.)
Nevertheless, we did not stop there.
There is another type of neutron detector which cannot be fooled by electromagnetic interference or x-ray or gamma radiation, and that is the bubble neutron detector.We have supplemented our He3 neutron detector with a bubble neutron detector from BTI in Chalk River, Canada. BTI’s bubble neutron detectors are unique in that they have been proven to react only to high energy neutrons. They are used extensively as neutron dosimeters in nuclear reactor facilities.
Our BTI bubble neutron detector confirmed our He3 neutron detector readings, and was actually used to verify the calibration of the He3 detector.
Both types of neutron detector described above will register background neutrons (principally from cosmic rays) but these are not statistically significant except perhaps when measuring very low rates of fusion at very high altitudes. Nevertheless, background neutron readings were measured and recorded before and after each fusion run, and the background readings have always been included in our results.
The third way of proving that high energy neutrons are being created is by the activation of materials such as silver. This has been accomplished by many fusioneers, notably Jon Rosenstiel and Carl Willis. Both have written extensively about their activation experiments in the forums of the Fusor.net website.
Our present fusor is not ideal for activation experiments. The presence of the bell jar means that material to be activated is quite far from the poissor. In addition, our low neutron output (so far not exceeding 50,000 neutrons per second) means that the rate of activation will be quite low.
Nevertheless, we intend to attempt the activation of silver soon!.