Title: Experimental study of hot electron generation in shock ignition relevant high-intensity regime with large scale hot plasmas

Abstract

In the shock ignition (SI) laser fusion scheme, hot electrons generated by the laser spike pulse can either preheat the fuel or strengthen the ignition shock, depending on the hot electron characteristics. We conducted a planar target experiment on the OMEGA-EP laser facility and characterized the temperature and total energy of hot electrons generated from a kilojoule-class 100-ps infrared (IR) or a 1-ns ultraviolet (UV) laser interacting with a large (L_n~330-450 μm) and hot (T_e~1-2 keV) coronal plasma at the SI-relevant intensities (~10¹⁶ W/cm²). The IR laser converts ~2.5% energy into hot electrons with T_hot~ 60–90 keV, while the UV laser couples 0.8% ± 0.7% energy into T_hot=27 ± 9 keV hot electrons. The IR-produced hot electrons yield five times higher Cu Kα emission than the UV case, confirming the higher electron conversion efficiency with the IR laser. The low energy conversion from the UV laser to hot electrons may be due to the refraction of the off-normal incident laser in the large coronal plasma. These findings are the first comparisons of hot electron generation between the IR and UV pulses at kilojoule scales in SI-relevant large-scale plasmas. The findings may expand the SI design space to include IR lasersmore » as the possible spike lasers.« less

Authors:

Zhang, S.  ^[1];

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• Search DOE PAGES for ORCID "0000-0002-6009-3443"

Krauland, C. M. ^[2]; Peebles, J.  ^[3];

• Search DOE PAGES for author "Peebles, J."
• Search DOE PAGES for ORCID "0000-0001-6488-3277"

Li, J. ^[1]; Beg, F. N.  ^[1];

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• Search DOE PAGES for ORCID "0000-0003-0391-8944"

Alexander, N.  ^[4];

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• Search DOE PAGES for ORCID "0000-0002-8933-9662"

Theobald, W. ^[5]; Betti, R. ^[5]; Haberberger, D. ^[5]; Campbell, E. M.  ^[5];

• Search DOE PAGES for author "Campbell, E. M."
• Search DOE PAGES for ORCID "0000-0002-1220-6538"

Yan, R.  ^[5];

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• Search DOE PAGES for ORCID "0000-0002-2479-1260"

Borwick, E. ^[5]; Ren, C. ^[5]; Wei, M. S.  ^[4]

• Search DOE PAGES for author "Wei, M. S."
• Search DOE PAGES for ORCID "0000-0002-4257-6409"

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+ Show Author Affiliations

1. Univ. of California, San Diego, CA (United States). Center for Energy Research
2. Univ. of California, San Diego, CA (United States). Center for Energy Research; General Atomics, San Diego, CA (United States)
3. Univ. of California, San Diego, CA (United States). Center for Energy Research; Univ. of Rochester, NY (United States)
4. General Atomics, San Diego, CA (United States)
5. Univ. of Rochester, NY (United States)

Publication Date:

Sat Feb 01 00:00:00 EST 2020

Research Org.:

General Atomics, San Diego, CA (United States)

Sponsoring Org.:

USDOE National Nuclear Security Administration (NNSA)

OSTI Identifier:

1801133

Alternate Identifier(s):

OSTI ID: 1600582

Grant/Contract Number:  

NA0002730; NA0003600; SC0014666

Resource Type:

Accepted Manuscript

Journal Name:

Physics of Plasmas

Additional Journal Information:

Journal Volume: 27; Journal Issue: 2; Journal ID: ISSN 1070-664X

Publisher:

American Institute of Physics (AIP)

Country of Publication:

United States

Language:

English

Subject:

70 PLASMA PHYSICS AND FUSION TECHNOLOGY; Physics; Laser plasma interactions; Electron beams; Hard X-rays; Laser fusion