Development of UV Spontaneous Raman Thermometry

Accurate temperature measurements in dynamically compressed materials pose significant challenges, yet they are crucial for advancing our understanding of material behavior under extreme conditions. Raman scattering has emerged as a promising diagnostic tool, offering a combination of simplicity and precision that surpasses techniques such as neutron resonance spectroscopy and pyrometry. This study aims to characterize and validate the application of UV spontaneous Raman spectroscopy in a benchtop setting prior to its deployment in laser-driven experiments, culminating in tests conducted with the Two-Stage Light Gas Gun at Lawrence Livermore National Laboratory. In this investigation, we focus on crystalline SiO₂ quartz as it undergoes heating through the α–β phase transition in a tube furnace. Utilizing UV spontaneous Raman Thermometry, we observe significant changes in the quartz spectrum throughout this transition, alongside variations in temperature, which are determined through the Stokes/anti-Stokes intensity ratio. Measurements are performed with the 4th harmonic of a nanosecond pulsed Nd:YAG laser, taking advantage of increased Raman scattering cross sections at UV wavelengths. To ensure the accuracy of our spectral temperature measurements, we compare them with readings obtained from a thermocouple affixed to the quartz sample holder.