X-ray conversion efficiency of high-Z hohlraum wall materials for indirect drive ignition

Dewald, E. L.; Rosen, M.; Glenzer, S. H.; Suter, L. J.; Girard, F.; Jadaud, J. P.; Schein, J.; Constantin, C.; Wagon, F.; Huser, G.; Neumayer, P.; Landen, O. L.
July 2008
Physics of Plasmas;Jul2008, Vol. 15 Issue 7, p072706
Academic Journal
The conversion efficiency of 351 nm laser light to soft x rays (0.1–5 keV) was measured for Au, U, and high Z mixture “cocktails” used as hohlraum wall materials in indirect drive fusion experiments. For the spherical targets in a direct drive geometry, flattop laser pulses and laser smoothing with phase plates are employed to achieve constant and uniform laser intensities of 1014 and 1015 W/cm2 over the target surface that are relevant for the future ignition experiments at the National Ignition Facility [G. H. Miller, E. I. Moses, and C. R. Wuest, Nucl. Fusion 44, 228 (2004)]. The absolute time and spectrally resolved radiation flux is measured with a multichannel soft x-ray power diagnostic. The conversion efficiency is then calculated by dividing the measured x-ray power by the incident laser power from which the measured laser backscattering losses are subtracted. After ∼0.5 ns, the time resolved x-ray conversion efficiency reaches a slowly increasing plateau of 95% at 1014 W/cm2 laser intensity and of 80% at 1015 W/cm2. The M-band flux (2–5 keV) is negligible at 1014 W/cm2 reaching ∼1% of the total x-ray flux for all target materials. In contrast, the M-band flux is significant and depends on the target material at 1015 W/cm2 laser intensity, reaching values between 10% of the total flux for U and 27% for Au. LASNEX simulations [G. B. Zimmerman and W. L. Kruer, Comm. Plasma Phys. Contr. Fusion 2, 51 (1975)] show good agreement in conversion efficiency and radiated spectra with data when using XSN atomic physics model and a flux limiter of 0.15, but they underestimate the generated M-band flux.


Related Articles

  • Spatial distribution of soft x-ray line emissions from aluminum plasma excited by a pair of femtosecond-laser pulses. Okano, Yasuaki; Oguri, Katsuya; Nishikawa, Tadashi; Nakano, Hidetoshi // Journal of Applied Physics;3/15/2006, Vol. 99 Issue 6, p063302 

    We measured the time-integrated, spatially resolved spectra of soft x rays emitted from laser-induced aluminum plasma to characterize its spatial features. The plasma was excited by an intense femtosecond-laser pulse with a controlled artificial prepulse at intensities of 9.9×1015 and...

  • Statistical investigations of the beam stability of the double-pass amplified zinc soft X-ray laser at 21.2 nm. Präg, A. R.; Mocek, T.; Kozlová, M.; Rus, B.; Rohlena, K. // European Physical Journal D -- Atoms, Molecules, Clusters & Opti;Sep2003, Vol. 26 Issue 1, p59 

    At the Prague asterix laser system (PALS) of the Academy of Sciences of the Czech Republic the 1-TW asterix iodine laser is used as a pump source for soft X-ray laser experiments. The prepulse technique was applied which is known to enhance the X-ray laser output at the J=0-1 transition...

  • Output and Optical Performances of Ne-like Ar Capillary Discharge Soft X-ray Laser. Watanabe, Masato; Xiao, Yifan; Sakai, Yusuke; Okino, Akitoshi; Hotta, Eiki // AIP Conference Proceedings;2006, Vol. 808 Issue 1, p271 

    Compact soft X-ray laser has been developed. In past experiments, spike output has been observed, when operating the device with a predischarge current of 5 to 15 A, a current of 9 to 35 kA with a rise time of 55 ns in an argon gas pressure range from 100 to 800 mTorr. Spectroscopic measurement...

  • Compact High Repetition Rate Soft X-Ray Lasers: A Doorway To High Intensity Coherent Soft X-Ray Science On A Table-Top. Rocca, J. J.; Wang, Y.; Luther, B.; Berrill, M.; Larotonda, M.; Alessi, D.; Shlyaptsev, V. N.; Granados, E.; Menoni, C. S. // AIP Conference Proceedings;2007, Vol. 926 Issue 1, p135 

    We discuss recent advances in high repetition rate table-top soft x-ray lasers that allow the generation of laser beams in the 25–100 eV photon energy region with peak spectral brightness that surpasses by several orders of magnitude that of undulators in third generation synchrotrons,...

  • Compact soft x-ray source using Thomson scattering. Kashiwagi, Shigeru; Kuroda, Ryunosuke; Oshima, Takashi; Nagasawa, Fumio; Kobuki, Tomoaki; Ueyama, Daisuke; Hama, Yoshimasa; Washio, Masakazu; Ushida, Kiminori; Hayano, Hitoshi; Urakawa, Junji // Journal of Applied Physics;12/15/2005, Vol. 98 Issue 12, p123302 

    A compact soft x-ray source using Thomson scattering, enabled by the combination of a picosecond laser and an electron rf gun, was developed aiming at biological studies such as those using an x-ray microscope. The x-ray source included both a photoinjector system and a picosecond laser system...

  • A beam intensity monitor for the evaluation beamline for soft x-ray optical elements. Imazono, Takashi; Moriya, Naoji; Harada, Yoshihisa; Sano, Kazuo; Koike, Masato // AIP Conference Proceedings;7/12/2012, Vol. 1465 Issue 1, p38 

    Evaluation Beamline for Soft X-Ray Optical Elements (BL-11) at the SR Center of Ritsumeikan University has been operated to measure the wavelength and angular characteristics of soft x-ray optical components in a wavelength range of 0.65-25 nm using a reflecto-diffractometer (RD). The beam...

  • High resolution soft x-ray spectroscopy of low Z K-shell emission from laser-produced plasmas. Dunn, J.; Magee, E. W.; Shepherd, R.; Chen, H.; Hansen, S. B.; Moon, S. J.; Brown, G. V.; Gu, M.-F.; Beiersdorfer, P.; Purvis, M. A. // Review of Scientific Instruments;Oct2008, Vol. 79 Issue 10, p10E314 

    A large radius, R=44.3 m, high resolution grating spectrometer (HRGS) with 2400 lines/mm variable line spacing has been designed for laser-produced plasma experiments conducted at the Lawrence Livermore National Laboratory Jupiter Laser Facility. The instrument has been run with a low-noise,...

  • Gated x-ray intensifier for large format simultaneous imaging. McCarville, T.; Fulkerson, S.; Booth, R.; Emig, J.; Young, B.; Anderson, S.; Heeter, B. // Review of Scientific Instruments;Oct2005, Vol. 76 Issue 10, p103501 

    Some applications of gated x-ray imagers, pulsed x-ray spectroscopy, for example, benefit if image capture is simultaneous and gain is uniform over the frame. Simultaneity and uniformity are both improved when the voltage gate pulse propagation distance is as short as practical across the...

  • The RFR-4 X-ray Streak Camera. Lazarchuk, V. P.; Litvin, D. N.; Murugov, V. M.; Petrov, S. I.; Pryanishnikov, I. G.; Senik, A. V. // Instruments & Experimental Techniques;Mar/Apr2004, Vol. 47 Issue 2, p251 

    The RFR-4 X-ray streak camera with a slit scan designed on the basis of an X-ray sensitive evacuated image tube is described. The obtained images are recorded using a charge-coupled device (CCD) camera. The basic parameters of the X-ray streak camera are as follows: (1) the recorded spectral...


Read the Article


Sorry, but this item is not currently available from your library.

Try another library?
Sign out of this library

Other Topics