Graduate Exam Abstract

Liang Yin

Ph.D. Preliminary
December 11, 2015, 12:15 pm - 3:15 pm
A210 ERC
Comprehensive characterization of laser-created Gd and Tb plasma emission near λ = 6.7nm

Abstract: We have conducted a comprehensive characterization of Gd and Tb laser- created plasmas radiating beyond extreme ultraviolet (BEUV) emission at wavelengths from 6.5 to 6.7 nm over a broad range of laser irradiation parameters using a single laser with tunable pulse duration. Measurements were conducted by focusing λ = 1030 nm laser pulses with durations ranging from 120 ps to 4ns onto planar targets. The angular distribution of the in-band BEUV emission yield was measured using an array of calibrated energy-monitors to obtain an accurate measurement of conversion efficiency. The peak of the BEUV emission spectra was observed to shift with pulse duration of the driver laser pulses resulting with the Gd plasma emission driven by nanosecond laser pulses best matching the reflectivity bandwidth of available La/B4C multilayer mirrors near λ = 6.7 nm. The variation of the spectral distribution was also measured as a function of laser pulse duration and angle respectively to better understand the plasma conditions. In order to study fine spectral structure of Gd plasma a spatially resolved spectral profile of Gd plasma was obtained. Images of the plasma as a function of three major driver laser parameters including intensity, pulse duration, and focal spot size were also obtained. A maximum conversion efficiency of 0.47% for Gd plasma and 0.45% for Tb plasma respectively within a 0.6% bandwidth was obtained. The measured spectra and the plasma images were used to elucidate the plasma physics behind the observed trends.

Adviser: Jorge J. Rocca
Co-Adviser: NA
Non-ECE Member: Azer P. Yalin, Mechanical Engineering
Member 3: Mario C. Marconi, Electrical and Computer Engineering
Addional Members: Carmen S. Menoni, Electrical and Computer Engineering

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Program of Study:
ECE 506
ECE 604
ECE 641
ECE 650
ECE 799
MATH 531