Experimental measurement of Au M-band flux in indirectly driven double-shell implosions

Abstract

Indirectly-driven double-shell implosions are being investigated as a possible noncryogenic path to ignition on the National Ignition Facility (NIF). In recent double-shell experiments, the inner shell trajectory was shown to exhibit a strong sensitivity to the temporal history of the M-band (2-5 keV) radiation emitted from the Au hohlraum wall. A large time-dependent discrepancy was observed between measurement and simulation of the x-ray flux in this range. In order to better characterize the radiation environment seen in these implosions, an experimental campaign was conducted on the Omega Laser. A number of diagnostics were used to measure both the temporal and spectral nature of the M-band flux. Results were obtained from an absolutely calibrated 12 channel filtered x-ray diode array (Dante) as well as two streaked crystal spectrometers and an absolutely calibrated time-integrated spectrometer (Henway). X-ray backlighting was also used to directly measure the effect of M-band radiation on the trajectory of the inner shell. The data from all diagnostics are shown to be in excellent agreement and provide a consistent picture of the M-band flux. These results are being used to constrain and improve the simulation of hohlraum-generated M-band radiation that will be necessary for the design of future double-shell implosions employing higher-Z inner shells.

A novel method for determining the M-band fraction in laser-driven gold hohlraums

“…This is also beneficial for comparisons with the simulations, especially when there are discrepancies between the SXS observations and numerical simulations. 8,11 In this paper, we propose a novel method for determining f m , the M-band fraction in total x-ray flux, by using the shock wave measurement technique. As well known, the shock wave technique is widely used to determine the peak radiation temperature T r inside a hohlraum.…”

“…3 Accurate measurement and theoretical prediction of M-band radiation flux are of great importance for ICF ignition capsule design. There have been many works [3][4][5][6][7][8] engaged in the study of the M-band radiation. In these works, a broadband x-ray spectrometer ͑SXS 9 or Dante 10 ͒ is used to measure the x-ray flux steaming out of the hohlraums along a line through a laser entrance hole ͑LEH͒.…”

Simulations investigating the effect of a deuterium-tritium-ice coating on the motion of the gold cone surface in a re-entrant cone-guided fast ignition inertial confinement fusion capsule

“…The thickness of the tamping layer was varied from 5 to 50 m. Both Au and uranium M-band drive descriptions were employed based upon data presented in Ref. 12. The M-band is the principal spectral component of the radiation from the hohlraum wall in indirect drive ICF that is able to penetrate the shell of an ICF capsule and so drive motion of the gold cone.…”

Developing one-dimensional implosions for inertial confinement fusion science

“…Double shell targets provide a very different approach to ICF than single shells [24][25][26][27][28][29][30] . Double shell targets consist of a low Z outer shell which separates the driver from the inner shell Developing one-dimensional implosions for inertial confinement fusion science filled with the fusion fuel.…”