Calibration Constant of a Silver Activated Geiger Counter Used for Neutron Efficiency Measurements in Plasma Focus Devices: Theoretical vs. Experimental Studies

Design and Fabrication of a Data Acquisition System for Pulsed Neutron Flux Measurement of Plasma Focus Devices

“…According to Gentilini et al [18], there are at least four calibration constant measurement methods among which it has been decided to incorporate the count rate measurement at saturation, following Etaati et al [19], whose more general approach is comparable to Gentillini et al's. In this method, the purpose is the measurement of thermal neutron flux per unit neutron source (i.e., c value) in the detectors, for which at t = t 0 a neutron source with intensity I 0 (in neutron/s unit) is placed at the position where the plasma is formed in the PF device.…”

“…In this method, the purpose is the measurement of thermal neutron flux per unit neutron source (i.e., c value) in the detectors, for which at t = t 0 a neutron source with intensity I 0 (in neutron/s unit) is placed at the position where the plasma is formed in the PF device. After five half-lives (about 1,000 s), an irradiated silver foil is saturated and its induced activity can be measured that is further used in the count rate at saturation relations to obtain the c value [19].…”

“…In this paper, following the work of Etaati et al [19], the calibration constant is calculated in 5 steps: (1) The detection of Am-Be gamma rays to evaluate the neutron contributions to the total counts (see section ''Angular Distribution Measurement'' a)). …”

“…The appropriate dimension of moderating material has been obtained using the Monte Carlo simulation with the MCNP4C code in which the number of (n, c) reactions within silver layer (i.e., FM4-Tally in MCNP) to the incident neutron flux (i.e., F2 tally in MCNP) at the side wall/one end of the detector has been calculated. Based on the Monte Carlo data, the optimum polyethylene thicknesses for the side wall and end regions are 6 and 3 cm, respectively [19]. In this simulation, the Am-Be source (a 35 mm diameter by 70 mm length cylinder) has been assumed to be located at (r, h) = (0.0,0.0) which is 90 cm far from the activation counters as shown in Fig.…”

“…However, the calibration factor (K) for each activation counter has to be determined prior to any measurement. In this study, the calibration constant, K, has been calculated using the technique of count rate measurement at saturation, following both Etaati et al [19] and the timing pattern algorithm of Fig. 7.…”