Investigation of Neutron-fluence Measurement Methods for Estimating Neutron-induced Activity from an Electrostatic Accelerator Source

Three methods to detect neutrons emitted from an electrostatic accelerator were examined. These were gold foil activation, thermoluminescent dosimeters (TLDs), and CR-39. The gold-foil activation method has previously been proven effective in the measurement of neutrons emitted from cyclotron sources. In the case of electrostatic accelerators, a greater amount of fast neutrons and a smaller amount of thermal neutrons are observed compared to a cyclotron accelerator. Therefore, the error in calculating the thermal neutron flux became unacceptably large. By comparison the CR-39 detectors were apparently unable to measure thermal neutrons well, because some tracks were also generated by fast neutrons causing a signal interference. In the case of TLDs, as the material was not sensitive to fast neutrons, it was not affected by them, and hence could adequately measure the thermal neutron flux. However, it was found that in some cases its measurements could be offset by the influence of high dose rate of gamma rays.