Development of Position Sen.sitive 3He Proportional Counter for a Single Moderator Type Neutron Spect:rometer

A position sensitive 3He proportional counter with 1 m length was developed to use for a single moderator type neutron spectrometer, which measures neutron spectrum from the depth distribution of thermal neutrOns in the moderator. The counter is of charge division type using an anode wire with resistance. The detection positions can be determined from the ratio of the pulse heights read out from both ends of the counter. The inner diameter and compo- sition of the counting gas were optimized with a sirmple Monte Carlo calculation code. From the optimization the inner diameterof 25 mm and the mixed gas of 130 kPa 3He and 70 kPa CF4 were adopted. A relationship between the detection position and the ratio of both pulse heights and a spatial resolution were measured using thermal neutrons The relationship has a one-to-one correspondence.The spatial resolution was evaluated to be less than 10 mm all over the sensitivearea, an d the value is small enough for the spectrometer.