LASER-DRIVEN PLATE IMPACT EXPERIMENTS FOR SHOCK WAVE COMPRESSION IN SOLIDS

In the last decade, tabletop shock wave compression using laser-driven impactors has gained considerable attention due to its simplicity, versatility, applicability, and high throughput. This research study will compare the effects of two different Nd:YAG laser beam profiles- one with a Gaussian and another with a tophat beam. The objective is to analyze the inconsistencies and precision when using a Gaussian beam versus the commonly used tophat beam profile for laser launching flyer plates. A Gaussian beam is the “natural” output of an Nd:YAG laser, while a tophat beam profile requires additional shaping optics to achieve homogenization, increasing costs. Therefore, a comparative study is necessary to determine the effectiveness of each laser beam profile, when they are used for post-mortem spectroscopies in shock compression studies.

In this work, 3”x3”x0.25” glass plates were shocked to create craters using each beam type. A Gaussian beam was used to shock the glass plates at Miami University Middletown with 850 mJ energy per pulse, and a tophat beam was used at the University of Illinois Urbana Champaign using 100mJ-1500mJ laser energies for comparison. The craters are analyzed using several microscopy techniques to determine differences in morphologies and to probe the roles of optomechanical imperfections in the sample mount. Preliminary results show that the Gaussian beam produces a consistent oval-shaped crater, while the tophat beam produces a more circular crater shape with a diameter depending on the laser energy used to impact the glass plate. Future work will focus on 1) an in-depth analysis of the beam homogeneity at the focal point of the laser, 2) morphologies of the launched impactors, and 3) the impact of a Gaussian beam on spectroscopic evidence collected from the craters formed in shock compressed crystalline and amorphous materials.