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Hall GN, Krauland CM, Schollmeier MS, et al. The Crystal Backlighter Imager: A spherically bent crystal imager for radiography on the National Ignition Facility. Rev Sci Instrum. 2019;90(1):013702doi: 10.1063/1.5058700.
Hall, G. N., Krauland, C. M., Schollmeier, M. S., Kemp, G. E., Buscho, J. G., Hibbard, R., Thompson, N., Casco, E. R., Ayers, M. J., Ayers, S. L., Meezan, N. B., Hopkins, L. F. B., Nora, R., Hammel, B. A., Masse, L., Field, J. E., Bradley, D. K., Bell, P., Landen, O. L., Kilkenny, J. D., Mariscal, D., Park, J., McCarville, T. J., Lowe-Webb, R., Kalantar, D., Kohut, T., & Piston, K. (2019). The Crystal Backlighter Imager: A spherically bent crystal imager for radiography on the National Ignition Facility. The Review of scientific instruments, 90(1), 013702. https://doi.org/10.1063/1.5058700
Hall, G N, et al. "The Crystal Backlighter Imager: A spherically bent crystal imager for radiography on the National Ignition Facility." The Review of scientific instruments vol. 90,1 (2019): 013702. doi: https://doi.org/10.1063/1.5058700
Hall GN, Krauland CM, Schollmeier MS, Kemp GE, Buscho JG, Hibbard R, Thompson N, Casco ER, Ayers MJ, Ayers SL, Meezan NB, Hopkins LFB, Nora R, Hammel BA, Masse L, Field JE, Bradley DK, Bell P, Landen OL, Kilkenny JD, Mariscal D, Park J, McCarville TJ, Lowe-Webb R, Kalantar D, Kohut T, Piston K. The Crystal Backlighter Imager: A spherically bent crystal imager for radiography on the National Ignition Facility. Rev Sci Instrum. 2019 Jan;90(1):013702. doi: 10.1063/1.5058700. PMID: 30709218.
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Rev Sci Instrum. 2019 Jan;90(1):013702. doi: 10.1063/1.5058700.

The Crystal Backlighter Imager: A spherically bent crystal imager for radiography on the National Ignition Facility.

The Review of scientific instruments

G N Hall, C M Krauland, M S Schollmeier, G E Kemp, J G Buscho, R Hibbard, N Thompson, E R Casco, M J Ayers, S L Ayers, N B Meezan, L F Berzak Hopkins, R Nora, B A Hammel, L Masse, J E Field, D K Bradley, P Bell, O L Landen, J D Kilkenny, D Mariscal, J Park, T J McCarville, R Lowe-Webb, D Kalantar, T Kohut, K Piston

Affiliations

  1. Lawrence Livermore National Laboratory, 7000 East Avenue, Livermore, California 94550, USA.
  2. General Atomics, P.O. Box 85608, San Diego, California 92186-5608, USA.
  3. Sandia National Laboratories, Albuquerque, New Mexico 87185, USA.

PMID: 30709218 DOI: 10.1063/1.5058700

Abstract

The Crystal Backlighter Imager (CBI) is a quasi-monochromatic, near-normal incidence, spherically bent crystal imager developed for the National Ignition Facility (NIF), which will allow inertial confinement fusion capsule implosions to be radiographed close to stagnation. This is not possible using the standard pinhole-based area-backlighter configuration, as the self-emission from the capsule hotspot overwhelms the backlighter signal in the final stages of the implosion. The CBI mitigates the broadband self-emission from the capsule hot spot by using the extremely narrow bandwidth inherent to near-normal-incidence Bragg diffraction. Implementing a backlighter system based on near-normal reflection in the NIF chamber presents unique challenges, requiring the CBI to adopt novel engineering and operational strategies. The CBI currently operates with an 11.6 keV backlighter, making it the highest energy radiography diagnostic based on spherically bent crystals to date. For a given velocity, Doppler shift is proportional to the emitted photon energy. At 11.6 keV, the ablation velocity of the backlighter plasma results in a Doppler shift that is significant compared to the bandwidth of the instrument and the width of the atomic line, requiring that the shift be measured to high accuracy and the optics aligned accordingly to compensate. Experiments will be presented that used the CBI itself to measure the backlighter Doppler shift to an accuracy of better than 1 eV. These experiments also measured the spatial resolution of CBI radiographs at 7.0 μm, close to theoretical predictions. Finally, results will be presented from an experiment in which the CBI radiographed a capsule implosion driven by a 1 MJ NIF laser pulse, demonstrating a significant (>100) improvement in the backlighter to self-emission ratio compared to the pinhole-based area-backlighter configuration.

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