Transient Grating Spectroscopy: Compact System Geometry Developments and Improved Software

Abstract

Transient grating spectroscopy (TGS) is a rapid, non-destructive technique for measuring the thermal, elastic, and acoustic properties of the top several microns of a reflective surface. It has uses across many areas of materials research. Current TGS systems require complex optics tables taking up cumbersome amounts of space, restricting TGS to a predominantly lab-based method. This thesis first outlines a new design for TGS systems: an asymmetric probe, planar (APP) geometry, which enables TGS to be shrunk and simplified, lowering the barrier to entry and allowing for wider adoption in labs and industry. This Mini-TGS system was benchmarked against an existing system on a single-crystal tungsten sample, showing it produces the same SAW frequency as the benchmark system. The design enables TGS to be more widely adopted for use in more varied and compact environments because of its smaller size and simplicity. This thesis then outlines a study of reactor pressure vessel (RPV) coupons aimed at further understanding how properties evolve as a function of time in a reactor, as a step towards demonstrating that TGS can reliably detect if an RPV is fit for service. Ultimately, this work unveiled problems in the TGS fitting code. Lastly, this thesis details the software changes to the general TGS fitting code made to improve the fitting code in response to the RPV study.