Lawrence Livermore National Laboratory



David Weisz

Overview

Frequently, the most time-consuming step in preparing geologic samples for certain analytical techniques is dissolving the sample in a hazardous acid mixture. This process generally occurs on the order of days, and the volume of acid used is commensurate with the mass of the of the sample dissolved. A laser-assisted dissolution process termed Laser-Driven Hydrothermal Processing (LDHP) appears to rapidly break down and dissolve samples of interest via adduced hydrothermal process. However, characterization of laser and scanning parameters and how they affect the fundamental aspects of LDHP is needed.

Our study probed the basic physicochemical processes of LDHP and explored various conditions for optimizing LDHP's efficiency to process geologic samples. Our results demonstrate the effect of various parameters on the efficiency of LDHP and present additional evidence that the laser-assisted dissolution process occurs by a hydrothermal mechanism. We found that LDHP shows promise as a new capability to rapidly process geological samples for analysis by various mass spectrometric techniques.

LDHP has the ability to selectively process a small volume. Traditional acid digestions must dissolve the entire sample, possibly diluting the sample, or use tools to physically separate the desired portion from the rest of the sample, potentially introducing contamination. Selectively processing a small volume of the material with LDHP can improve the precision of sensitive measurements because only a desired portion has been processed. LDHP's advantages have implications for programs and missions that analyze both Earth-based geologic samples and non-terrestrial samples, e.g., lunar, meteoric.

Impact on Mission

Our findings indicate that LDHP can process highly stressed, glassy matrix materials (tektite) that are similar to nuclear fallout materials. Thus, with continued study and optimization, LDHP may be applied to processing nuclear forensic samples supporting Lawrence Livermore National Laboratory's mission focus in nonproliferation. Novel aspects of the work applicable to broader application may be added to the Laboratory's intellectual property portfolio.