Reflected Laser Light as a Diagnostic Insight for Femtosecond Laser-Plasma Coupling

Date of Award

3-2025

Document Type

Thesis

Degree Name

Master of Science in Applied Physics

Department

Department of Engineering Physics

First Advisor

Michael L. Dexter, PhD

Abstract

High-energy laser technology is critical for military, scientific, and industrial applications, but traditional mixed-radiation facilities are hindered by cost, scheduling constraints, and lack of portability. A high-repetition-rate, cost-effective alternative is needed to meet evolving application needs and timelines. This study investigates changes in reflected laser intensity to diagnose coupling efficiency and optimize energetic particle generation in ultraintense laser-target interactions. Using an ultraintense 35 femtosecond, 9 - 12 mJ laser and a deuterated water target, reflected laser light was captured via high-resolution imaging, while energetic electron and X-ray data were collected using a custom spectrometer and ion chamber, respectively. Statistical analysis identified 56.68% prepulse as the most stable coupling condition, while higher prepulse levels resulted in plasma instability and erratic fluctuations, and lower prepulse levels did not generate sufficient preplasma for effective coupling. Hotelling’s T2 test identified anomalies, while centroid and maximum intensity shifts provided a real-time diagnostic for plasma behavior. Pearson and Spearman correlation analyses confirmed trends in coupling efficiency, identifying optimal prepulse conditions. These findings establish practical diagnostic tools, including running mean fluctuation analysis and real-time feedback integration, to enhance experimental repeatability and system control. Future work will refine these tools through baseline testing and expand analysis of the 0.00% prepulse condition to investigate observed anomalies. Implementing these diagnostics in active feedback systems could significantly improve stability and efficiency in high-intensity laser experiments.

AFIT Designator

AFIT-ENP-MS-25-M-225

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