Measurement of preheat due to fast electrons in laser implosions

Barukh Yaakobi; Christian Stoeckl; Thomas R. Boehly; Robert Stephen Craxton; David D. Meyerhofer; Wolf D. Seka

doi:10.1117/12.425642

23 April 2001 Measurement of preheat due to fast electrons in laser implosions

Barukh Yaakobi, Christian Stoeckl, Thomas R. Boehly, Robert Stephen Craxton, David D. Meyerhofer, Wolf D. Seka

Proceedings Volume 4424, ECLIM 2000: 26th European Conference on Laser Interaction with Matter; (2001) https://doi.org/10.1117/12.425642
Event: 26th European Conference on Laser Interaction with Matter (ECLIM 2000), 2000, Prague, Czech Republic

Abstract

The emission of hard x-rays, coincident with 3(omega) _L/2 emission, has been measured in laser-interaction experiments on the OMEGA laser system, indicating fast electrons due to the two-plasmon-decay instability. The purpose of the present experiment was to determine the preheat level due to these electrons. In a calibration experiment a flat target containing titanium and vanadium layers was irradiated and the preheat was determined using two signatures: the intensity of K(alpha) lines from the high-Z target layers and the spectrum of hard x-rays measured by an array of BaF₂ scintillation detectors. The intensity of both signals can be directly related to the preheat energy; therefore, the two preheat measurements can be cross calibrated. This comparison lends support to the determination of preheat in spherical target experiments, where only the hard x-ray diagnostic is available. For CH shell implosions and square laser pulses the preheat energy deposited in the target amounts to approximately 0.1 percent of the laser energy. The maximum rise in temperature due to the preheat is approximately 10 eV. Finally, the temperature of fast electrons is deduced from the measured spectrum of MeV protons accelerated from the surface of the target; the result agree with the temperature deduced from hard x-rays, namely, T approximately 100 to 200 keV.

Citation Download Citation

Barukh Yaakobi, Christian Stoeckl, Thomas R. Boehly, Robert Stephen Craxton, David D. Meyerhofer, and Wolf D. Seka "Measurement of preheat due to fast electrons in laser implosions", Proc. SPIE 4424, ECLIM 2000: 26th European Conference on Laser Interaction with Matter, (23 April 2001); https://doi.org/10.1117/12.425642

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