skip to main content
OSTI.GOV title logo U.S. Department of Energy
Office of Scientific and Technical Information

Title: Short Pulse Laser Absorption and Energy Partition at Relativistic Laser Intensities

Abstract

We have performed experiments at the COMET and Calisto short pulse laser facilities to make the first comprehensive measurements of the laser absorption and energy partition in solid targets heated with an ultrashort laser pulse focused to relativistic laser intensities (>10 10{sup 17} W/cm{sup 2}). The measurements show an exceedingly high absorption for P polarized laser-target interactions above 10{sup 19} W/cm{sup 2}. Additionally, the hot electron population is observed to markedly increase at the same intensity range. An investigation of the relaxation process was initiated u using time sing time-resolved K{sub {alpha}} spectroscopy. Measurements of the time time-resolved K{sub {alpha}} radiation suggest a 10-20 ps relativistic electron relaxation time. However modeling difficulties of these data are apparent and a more detailed investigation on this subject matter is warranted.

Authors:
; ; ; ; ; ; ; ; ; ; ; ; ;
Publication Date:
Research Org.:
Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States)
Sponsoring Org.:
USDOE
OSTI Identifier:
908084
Report Number(s):
UCRL-TR-229579
TRN: US0703609
DOE Contract Number:
W-7405-ENG-48
Resource Type:
Technical Report
Country of Publication:
United States
Language:
English
Subject:
70 PLASMA PHYSICS AND FUSION; 42 ENGINEERING; ABSORPTION; COMETS; ELECTRONS; LASERS; RADIATIONS; RELAXATION TIME; SIMULATION; SPECTROSCOPY; TARGETS

Citation Formats

Shepherd, R, Chen, H, Ping, Y, Dyer, G, Wilks, S, Chung, H, Kemp, A, Hanson, S, Widmann, K, Fournier, K, Faenov, A, Pikuz, T, Niles, A, and Beiersdorfer, P. Short Pulse Laser Absorption and Energy Partition at Relativistic Laser Intensities. United States: N. p., 2007. Web. doi:10.2172/908084.
Shepherd, R, Chen, H, Ping, Y, Dyer, G, Wilks, S, Chung, H, Kemp, A, Hanson, S, Widmann, K, Fournier, K, Faenov, A, Pikuz, T, Niles, A, & Beiersdorfer, P. Short Pulse Laser Absorption and Energy Partition at Relativistic Laser Intensities. United States. doi:10.2172/908084.
Shepherd, R, Chen, H, Ping, Y, Dyer, G, Wilks, S, Chung, H, Kemp, A, Hanson, S, Widmann, K, Fournier, K, Faenov, A, Pikuz, T, Niles, A, and Beiersdorfer, P. Tue . "Short Pulse Laser Absorption and Energy Partition at Relativistic Laser Intensities". United States. doi:10.2172/908084. https://www.osti.gov/servlets/purl/908084.
@article{osti_908084,
title = {Short Pulse Laser Absorption and Energy Partition at Relativistic Laser Intensities},
author = {Shepherd, R and Chen, H and Ping, Y and Dyer, G and Wilks, S and Chung, H and Kemp, A and Hanson, S and Widmann, K and Fournier, K and Faenov, A and Pikuz, T and Niles, A and Beiersdorfer, P},
abstractNote = {We have performed experiments at the COMET and Calisto short pulse laser facilities to make the first comprehensive measurements of the laser absorption and energy partition in solid targets heated with an ultrashort laser pulse focused to relativistic laser intensities (>10 10{sup 17} W/cm{sup 2}). The measurements show an exceedingly high absorption for P polarized laser-target interactions above 10{sup 19} W/cm{sup 2}. Additionally, the hot electron population is observed to markedly increase at the same intensity range. An investigation of the relaxation process was initiated u using time sing time-resolved K{sub {alpha}} spectroscopy. Measurements of the time time-resolved K{sub {alpha}} radiation suggest a 10-20 ps relativistic electron relaxation time. However modeling difficulties of these data are apparent and a more detailed investigation on this subject matter is warranted.},
doi = {10.2172/908084},
journal = {},
number = ,
volume = ,
place = {United States},
year = {Tue Feb 27 00:00:00 EST 2007},
month = {Tue Feb 27 00:00:00 EST 2007}
}

Technical Report:

Save / Share:
  • Absorption of short-pulse electromagnetic energy by a resistively loaded straight wire is examined. Energy collected by the wire, load energy, peak load currents, and peak load voltages are found for a wide range of parameters, with particular emphasis on nuclear electromagnetic pulse (EMP) phenomena. A series of time-sequenced plots is used to illustrate pulse propagation on wires when loads and wire ends are encountered. (auth)
  • Recently continuous wave fiber laser systems with output powers in excess of 500W with good beam quality have been demonstrated [1]. High energy, ultrafast, chirped pulsed fiber laser systems have achieved record output energies of 1mJ [2]. However, these high-energy systems have not been scaled beyond a few watts of average output power. Fiber laser systems are attractive for many applications because they offer the promise of high efficiency, compact, robust systems that are turn key. Applications such as cutting, drilling and materials processing, front end systems for high energy pulsed lasers (such as petawatts) and laser based sources ofmore » high spatial coherence, high flux x-rays all require high energy short pulses and two of the three of these applications also require high average power. The challenge in creating a high energy chirped pulse fiber laser system is to find a way to scale the output energy while avoiding nonlinear effects and maintaining good beam quality in the amplifier fiber. To this end, our 3-year LDRD program sought to demonstrate a high energy, high average power fiber laser system. This work included exploring designs of large mode area optical fiber amplifiers for high energy systems as well as understanding the issues associated chirped pulse amplification in optical fiber amplifier systems.« less
  • Ultra-high-energy-density (UHED) matter, characterized by energy densities > 1 x 10 8 J cm -3 and pressures greater than a gigabar, is encountered in the center of stars and in inertial confinement fusion capsules driven by the world’s largest lasers. Similar conditions can be obtained with compact, ultra-high contrast, femtosecond lasers focused to relativistic intensities onto targets composed of aligned nanowire arrays. Here we report the measurement of the key physical process in determining the energy density deposited in high aspect ratio nanowire array plasmas: the energy penetration. By monitoring the x-ray emission from buried Co tracer segments in Nimore » nanowire arrays irradiated at an intensity of 4 x 10 19 W cm -2, we demonstrate energy penetration depths of several μm, leading to UHED plasmas of that size. Relativistic 3D particle-in-cell-simulations, validated by these measurements, predict that irradiation of nanostructures at intensities of > 1 x 10 22 W cm -2 will lead to a virtually unexplored extreme UHED plasma regime characterized by energy densities in excess of 8 x 10 10 J cm -3, equivalent to a pressure of 0.35 Tbar.« less
  • This report is a detailed proposal for a short pulse, short wavelength, optical probe which can be synchronized with either GDL or OMEGA. Typical probe laser parameters are lambda approx. 2000 A, t approx. = 2 ps, with an energy of several hundred ..mu..J and synchronization of 20 to 50 ps. The present design is based on detailed experimental work done over the past two years in the Picosecond Group at LLE.