Neutron production from thick targets bombarded by alpha particles: Experiment and theoretical analysis of neutron energy spectra

Pre-equilibrium emission effects in the measured isomeric yield ratios in alpha-induced reactions onAu197

“…Although the stack used in this experiment was thin to minimize the beam energy spread, a separate experiment was performed to estimate the contribution of the (n, y ) reaction to the activity of ' Au. The contribution of the (n, 2n) reaction to the activity of ' Au can be taken to be negligible since the Q value of the (n, 2n) reaction in ' Au is -8.072 MeV and the major portion of the neutron yield in (a,xn} reactions is below 8 MeV for the present energy range of incident alphas [24]. Gold foils of thickness 48.2 mg/cm were wrapped in Al foils of thickness 6.85 mg/cm and fixed to the exterior wall of the irradiation chamber.…”

“…As the count rate for the 411.8-keV peak was low, the average counting time was of the order of 10 sec. Assuming the neutron-yield spectrum to vary only slightly with the beam energy at this energy range [24], the percentage activities for '9sAu produced from background neutrons compared to the alpha activation at energies 35.2, 42.S, 43.9, and 48.6 MeV after correcting for different decay factors and target thicknesses are 0.026'Fo, 0.084%%uo, 0.064%, and 0.03%, respectively. The interference from the secondary neutrons, therefore, can be considered negligible.…”

“…Gamma emission P(J~) +g J =J N m 1g P(J~) (24) This sharp division assumption of relative gamma transitions has been used by Grant and Rathle [6] for analysis of IR's from (a, xn) and (a,pn) reactions on In and Sn isotopes. Other authors [7,8, 10] have also used this assumption to study the effect of entrance channel spin distribution on IR s of multiple-neutron-emission reactions with protons, deuterons, triton, He, and alpha projectiles.…”

Neutron dosimetry in the particle accelerator environment

“…In this paper we review neutron dosimetry around positive ion accelerators using active techniques of measurement involving direct reading neutron (ambient) dose equivalent meters (Sunil et al, , 2008a as well as time of flight and pulse height unfolding techniques of measuring energy distributions of neutron fluence (Sarkar et al, 1991;Nandy et al, 2001Nandy et al, , 2007Dhar et al, 2003a;Sunil et al, 2004Sunil et al, , 2008b and then converting those distributions to ambient dose equivalent using fluence to dose conversion coefficients. Theoretical analysis and developments (Sarkar and Nandy, 2000;Nandy et al, 1999;Dhar et al, 2003b;Maity et al, 2005;Tripathy et al, 2007Tripathy et al, , 2009 in this field of research are also reviewed.…”

“…Since, the proton recoil scintillation detector BC501 that we have used for our measurements is sensitive to g photons, a standard pulse-shape discrimination technique (Sarkar et al, 1991;Sunil et al, 2004) was used to distinguish neutrons from photons. The neutron energy was determined either by measuring the flight time of neutrons travelling a fixed distance (TOF technique) or by estimating the recoil proton energy distributions in the detector.…”