The difference in the pulse rise time of the preamplifier is more obvious in the 3He detector used in this study probably because of the Kr content, in which the electron drift velocity is low. Other factors that enhance such selfinduced space charge effect are those that result in higher primary electron density along the anode; such as the geometry of the tube and the magnitude of the gas multiplication.
The energy resolution of 4 He recoil peaks as a function of HV for neutron energies of 5.6 and 6.7 MeV are presented in Fig. 7b.The relatively large values of resolution for 4He counter should be partially attributed to the origin of the recoil peak, as this is not mono-energetic due to ds(En)/dO distribution. There is, however, no statistically significant variation of the resolution of the counter with the applied high voltage. For both detectors the measurements were carried out in the proportionality region.