K. Sakasai et al., EXPERIMENTS FOR OPTICAL NEUTRON DETECTION USING NUCLEAR PUMPED LASER, IEEE transactions on nuclear science, 43(3), 1996, pp. 1549-1553
Since the Nuclear Pumped Laser technique can be applied to optical det
ection of neutrons, numerical simulation and demonstration experiments
have been carried out for He-Ne-Ar mixtures. Test cells filled with H
e-3 gas (1140 torr), Ne gas (540 torr) and Ar gas (208 torr) were irra
diated with thermal neutron fluxes up to about 10(12) n/cm(2)/s at the
JRR-4 reactor, JAERI. In these experiments, optical output of 585.3 n
m from Ne 3p-3s transitions was clearly observed. Its intensity was al
most proportional to the thermal neutron flux, and these results agree
with those of numerical simulation. This system can be applied to opt
ical neutron detection. The simulation results show that the populatio
n inversion between the 3p'[1/2](0) and 3s'[1/2](1)(0) levels of neon
atoms for the cell can be achieved at the thermal neutron flux of much
higher than 10(12) n/cm(2)/s. It is also estimated that the threshold
thermal neutron flux for the population inversion is about 3 x 10(12)
n/cm(2)/s for the gas cell filled with optimized gas mixtures.