Feasibility of laser pumping with neutron fluxes from present-day large tokamaks

The minimum fusion-neutron flux needed to observe nuclear-pumped lasing with tokamaks can be reduced substantially by optimizing neutron scattering into the laser cell, located between adjacent toroidal-field coils. The laser lines most readily pumped are probably the 3He-Ne lines at 0.633 μ and in the infrared, where the 3He-Ne gas is excited by energetic ions produced in the 3He(n,p)T reaction. These lines are expected to lase at the levels of D-T neutron flux foreseen for the TFTR in 1989 (>>1012 n/cm2/s), while amplification should be observable at the existing levels of D-D neutron flux (≥ 5 x 109 n/cm2/s). Lasing on the 1.73 μ and 2.63 μ transitions of Xe may be observable at the maximum expected levels of D-T neutron flux in TFTR enhanced by scattering