System for measurement of low yield neutron pulses from D–D fusion reactions based upon a 3He proportional counter

A conventional neutron detection technique was adapted to measure low neutron yields from D–D fusion pulses. This method uses a 3He proportional counter surrounded by a paraffin moderator. Electric signals generated in the 3He tube are fed into a preamplifier. The output of the preamplifier is directly connected to a digital oscilloscope. The time-integrated signals represent the charge generated in the 3He tube which is proportional to the total neutron yield. The integration time is determined by the preamplifier and moderator characteristics within some hundreds of microseconds. No meaningful neutron background was detected during this time window. The system, previously calibrated, was used to measure the neutron yield (<106 neutron/pulse) generated in a fast and very small plasma focus device designed to operate with energies of tens of Joules. Neutron yields as low as 103 neutrons per pulse were measured. (technical design note)