Absolute keV X-ray yield and conversion efficiency in over dense Si petawatt laser plasma
Authors:
Sergey N. Ryazantsev,
Artem S. Martynenko,
Maksim V. Sedov,
Igor Yu. Skobelev,
Mikhail D. Mishchenko,
Yaroslav S. Lavrinenko,
Christopher D. Baird,
Nicola Booth,
Phil Durey,
Leonard N. K. DÖhl,
Damon Farley,
Kathryn L. Lancaster,
Paul Mckenna,
Christopher D. Murphy,
Tatiana A. Pikuz,
Christopher Spindloe,
Nigel Woolsey,
Sergey A. Pikuz
Abstract:
Laser-produced plasmas are bright, short sources of X-rays often used for time-resolved imaging and spectroscopy. Absolute measurement requires accurate knowledge of laser-to-x-ray conversion efficiencies, spectrum, photon yield and angular distribution. Here we report on soft X-ray emission from a thin Si foil irradiated by a sub-PW picosecond laser pulse. These absolute measurements cover a cont…
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Laser-produced plasmas are bright, short sources of X-rays often used for time-resolved imaging and spectroscopy. Absolute measurement requires accurate knowledge of laser-to-x-ray conversion efficiencies, spectrum, photon yield and angular distribution. Here we report on soft X-ray emission from a thin Si foil irradiated by a sub-PW picosecond laser pulse. These absolute measurements cover a continuous and broad spectral range that extends from 4.75 to 7.5 Angstroms (1.7-2.6 keV). The X-ray spectrum consists of spectral line transitions from highly charged ions and broadband emission with contributions from recombination, and free-free processes that occur as electrons decelerate in plasma electromagnetic fields. These quantitative measurements are compared to particle-in-cell simulations allowing us to distinguish bremsstrahlung and synchrotron contributions to the free-free emission. We found that experiment and simulation estimations of laser-to-bremsstrahlung conversion efficiency are in a good agreement. This agreement illustrates the accuracy of experiment and physical interpretation of the measurements.
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Submitted 20 December, 2021;
originally announced December 2021.
Observations of Pressure Anisotropy Effects within Semi-Collisional Magnetized-Plasma Bubbles
Authors:
E. R. Tubman,
A. S. Joglekar,
A. F. A. Bott,
M. Borghesi,
B. Coleman,
G. Cooper,
C. N. Danson,
P. Durey,
J. M. Foster,
P. Graham,
G. Gregori,
E. T. Gumbrell,
M. P. Hill. T. Hodge,
S. Kar,
R. J. Kingham,
M. Read,
C. P. Ridgers,
J. Skidmore,
C. Spindloe,
A. G. R. Thomas,
P. Treadwell,
S. Wilson,
L. Willingale,
N. C. Woolsey
Abstract:
Magnetized plasma interactions are ubiquitous in astrophysical and laboratory plasmas. Various physical effects have been shown to be important within colliding plasma flows influenced by opposing magnetic fields, however, experimental verification of the mechanisms within the interaction region has remained elusive. Here we discuss a laser-plasma experiment whereby experimental results verify tha…
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Magnetized plasma interactions are ubiquitous in astrophysical and laboratory plasmas. Various physical effects have been shown to be important within colliding plasma flows influenced by opposing magnetic fields, however, experimental verification of the mechanisms within the interaction region has remained elusive. Here we discuss a laser-plasma experiment whereby experimental results verify that Biermann battery generated magnetic fields are advected by Nernst flows and anisotropic pressure effects dominate these flows in a reconnection region. These fields are mapped using time-resolved proton probing in multiple directions. Various experimental, modelling and analytical techniques demonstrate the importance of anisotropic pressure in semi-collisional, high-$β$ plasmas, causing a reduction in the magnitude of the reconnecting fields when compared to resistive processes. Anisotropic pressure dynamics are crucial in collisionless plasmas, but are often neglected in collisional plasmas. We show pressure anisotropy to be essential in maintaining the interaction layer, redistributing magnetic fields even for semi-collisional, high energy density physics (HEDP) regimes
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Submitted 19 October, 2020;
originally announced October 2020.