Characterization of a continuous wave laser for resonance ionization mass spectroscopy analysis in nuclear forensics

Abstract

The application of resonance ionization mass spectroscopy (RIMS) to nuclear forensics involves the use of lasers to selectively ionize elements of concern. While current systems incorporate pulsed lasers for analysis of debris from nuclear detonation, the possibility exists to consider using continuous wave, or CW lasers RIMS has the potential to provide rapid quantification of isotope ratios of important elements in debris from nuclear detonation. The current approach to ionize uranium and plutonium uses three Ti-Sapphire pulsed lasers capable of a fundamental wavelength range of 700–1000 nm to perform ionization in three steps. This thesis evaluates the use of COTS CW laser to replace one of the pulsed lasers exciting the second resonance step of plutonium near 847.282 nm. The thesis research consists of three elements: (1) completion of an initial feasibility study to determine the viability of the COTS CW alternative, (2) identification and acquisition of a candidate COTS laser, and (3) testing to evaluate the critical laser parameters necessary to achieve high precision isotope ratio measurements including the stability over time of the mean wavelength, bandwidth and spectral mode purity. This narrower bandwidth COTS CW laser may enable simpler operations, greater robustness and better utilization of the available laser irradiance.