Nuclear-Driven Fluorescence Pumped Solid-State Lasers

Nuclear-Driven Fluorescence lamps (NDFs) coupled via hollow lightpipes to Nd/Cr codoped solid-state lasers have been evaluated; absolutely calibrated Ar, Kr, and Xe NDF spectra measured; and transient radiation-induced absorption (TRIA) effects characterized. Efficient NDFs require a high quantum efficiency (eta_ {q}), low W* fluorescer combined with a distributed mum-dimension nuclear source (aerosol or fibers). Alkali metals, 4.6 eV < W^* ~ 1.2 I_1 < 6.4 eV, are potentially efficient low W^* fluorescers. With radiation trapping, effective lifetimes of alkali-metal D-lines increase to ms range, effectively becoming metastable and allowing time for significant excimer formation and radiation. At nuclear pumping's low power densities, electron quenching of excimers formation and radiation. At nuclear pumping's low power densities, electron quenching of excimers should not be significant. Large (>0.25) diameter-to-length Ag reflector hollow lightpipes should have T > 70%, 90% with tapered fluorescer cells, while active mirror laser geometry is necessary for combining a lightpipe with an incoherent source. A conceptual rotating-disk coupled reactor/laser system produces 12 MW, 1 ms pulses with 3% total efficiency. ^3He(n,p)T excited NDF spectra (400-950 nm) were measured for deposited power densities of 7 mW/cm^3 (steady-state) and 20 W/cm^3 (pulsed), +/-30-40%. Maximum fluorescence efficiencies (eta_{fl}) were only 1% for Kr, 0.6% for Ar, and 0.2% for Xe, due to low eta_{q} (19% max for Kr) and He's high W^* value. Spectra consist of a few dominant lines plus several weaker lines. At 20 W/cm^3 weaker lines are much stronger relative to dominant lines than at 0.7 mW/cm ^3 and eta_{fl } slightly higher. For Ar and Kr, peak intensity of the dominant lines occurs at ~45 torr while for Xe it occurs between 9 and 22 torr. Comparing Kr NDF spectrum to an arc lamp, the 760-nm line is relatively much weaker and the 811-nm line much stronger. Strength of the 811-nm Kr NDF line was 0.9 W/cm^2 vs. ~2 W/cm^2 for the arc lamp. Kr NDF line strengths and branching ratios are compared to NBS table values for discharge excitation. Significant N_sp{2}{+} 1 ^{rm st} negative radiation occurred with only ^3He added to the fluorescer cell, mostly 1N(0,0) at 391 nm, with eta_{q} being 0.65 vs. a max. of 0.19 for Kr. A computer model developed for ^3He-N_2 predicts the same eta_{q} and variation with N_2 pressure as was measured. Minimum TRIA in fused silica optics occurs in a 650 nm < lambda < 850 nm window between UV and IR peaks. Under continuous probing with a broadband tungsten-halogen lamp, following a radiation pulse, the recovery curve for TRIA vs. time due to photobleaching was determined over a 0.01 -1000 s range, with the best fit provided by the sum of five exponentials with time constants of 0.53, 4.5, 17, 140, and 710 s.