CER SEMINAR

The absolute laser energy absorption measurements on nano-wire targets in the relativistic regime and optimization of targets for future experiment

Jaebum Park
April 5, 2018, 11:00am - 12:00pm, SERF Room 232

ABSTRACT:

Purvis et al. [1] demonstrated that nano-wire targets are capable of generating more extreme plasma conditions, high temperature and high pressure, than regular foil targets. For instance, a 0.5 J, 60 fs, frequency doubled table top laser illuminating Ni nano-wire targets generated not only higher continuum x-rays but also abundant He-like line emissions (thermal x-rays) which were absent with Ni foil targets. Extreme plasma conditions from these structured targets is believed to be due to higher laser absorption than that of normal foil targets. However, there exists no experimental measurements of laser energy absorption on nano-wire targets, especially in the relativistic laser intensity regime. We have performed an experiment on COMET laser to measure the absolute laser energy absorption on Au nano-wire targets and observed ~50% increased absorption with respect to Au foils. Most interesting and important finding is that the increased absorption is contributed to a combination of nano-wire target parameters, not a single parameter such as a wire diameter nor the wire number density. Findings from this work provide a basis to optimize target parameters for future experiments and deepen our understanding on how nano-wire targets lead to ultrahigh energy density plasmas. 

This work was performed under the auspices of U.S. DOE by LLNL under Contract No. DE-AC52-07NA27344, and LDRD-15-ERD-054.

[1] M. A. Purvis, V. N. Shlyaptsev, R. Hollinger, C. Bargsten, A. Pukhov, A. Prieto, Y. Wang, B. M. Luther, L. Yin, S. Wang, and J. J. Rocca, “Relativistic plasma nanophotonics for ultrahigh energy density physics,” Nature Photonics 7, 796 (2013) 

BIO:

Jaebum Park is interested in high energy density plasma physics, particularly relativistic laser matter interactions, laser energy coupling to targets and its applications, such as laser particle acceleration and x-ray generation. This includes experiments, simulation, and diagnostic development. He completed his Ph. D. in applied science at the University of California, Davis. His thesis was the effects of performed plasmas on the directionality of the relativistic electron beam.