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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. THE REVIEW OF SCIENTIFIC INSTRUMENTS 2019; 90:013702. [PMID: 30709218 DOI: 10.1063/1.5058700] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/18/2018] [Accepted: 12/17/2018] [Indexed: 06/09/2023]
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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Affiliation(s)
- G N Hall
- Lawrence Livermore National Laboratory, 7000 East Avenue, Livermore, California 94550, USA
| | - C M Krauland
- General Atomics, P.O. Box 85608, San Diego, California 92186-5608, USA
| | - M S Schollmeier
- Sandia National Laboratories, Albuquerque, New Mexico 87185, USA
| | - G E Kemp
- Lawrence Livermore National Laboratory, 7000 East Avenue, Livermore, California 94550, USA
| | - J G Buscho
- Lawrence Livermore National Laboratory, 7000 East Avenue, Livermore, California 94550, USA
| | - R Hibbard
- Lawrence Livermore National Laboratory, 7000 East Avenue, Livermore, California 94550, USA
| | - N Thompson
- Lawrence Livermore National Laboratory, 7000 East Avenue, Livermore, California 94550, USA
| | - E R Casco
- Lawrence Livermore National Laboratory, 7000 East Avenue, Livermore, California 94550, USA
| | - M J Ayers
- Lawrence Livermore National Laboratory, 7000 East Avenue, Livermore, California 94550, USA
| | - S L Ayers
- Lawrence Livermore National Laboratory, 7000 East Avenue, Livermore, California 94550, USA
| | - N B Meezan
- Lawrence Livermore National Laboratory, 7000 East Avenue, Livermore, California 94550, USA
| | - L F Berzak Hopkins
- Lawrence Livermore National Laboratory, 7000 East Avenue, Livermore, California 94550, USA
| | - R Nora
- Lawrence Livermore National Laboratory, 7000 East Avenue, Livermore, California 94550, USA
| | - B A Hammel
- Lawrence Livermore National Laboratory, 7000 East Avenue, Livermore, California 94550, USA
| | - L Masse
- Lawrence Livermore National Laboratory, 7000 East Avenue, Livermore, California 94550, USA
| | - J E Field
- Lawrence Livermore National Laboratory, 7000 East Avenue, Livermore, California 94550, USA
| | - D K Bradley
- Lawrence Livermore National Laboratory, 7000 East Avenue, Livermore, California 94550, USA
| | - P Bell
- Lawrence Livermore National Laboratory, 7000 East Avenue, Livermore, California 94550, USA
| | - O L Landen
- Lawrence Livermore National Laboratory, 7000 East Avenue, Livermore, California 94550, USA
| | - J D Kilkenny
- General Atomics, P.O. Box 85608, San Diego, California 92186-5608, USA
| | - D Mariscal
- Lawrence Livermore National Laboratory, 7000 East Avenue, Livermore, California 94550, USA
| | - J Park
- Lawrence Livermore National Laboratory, 7000 East Avenue, Livermore, California 94550, USA
| | - T J McCarville
- Lawrence Livermore National Laboratory, 7000 East Avenue, Livermore, California 94550, USA
| | - R Lowe-Webb
- Lawrence Livermore National Laboratory, 7000 East Avenue, Livermore, California 94550, USA
| | - D Kalantar
- Lawrence Livermore National Laboratory, 7000 East Avenue, Livermore, California 94550, USA
| | - T Kohut
- Lawrence Livermore National Laboratory, 7000 East Avenue, Livermore, California 94550, USA
| | - K Piston
- Lawrence Livermore National Laboratory, 7000 East Avenue, Livermore, California 94550, USA
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Schollmeier MS, Loisel GP. Systematic search for spherical crystal X-ray microscopes matching 1-25 keV spectral line sources. THE REVIEW OF SCIENTIFIC INSTRUMENTS 2016; 87:123511. [PMID: 28040953 DOI: 10.1063/1.4972248] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/06/2023]
Abstract
Spherical-crystal microscopes are used as high-resolution imaging devices for monochromatic x-ray radiography or for imaging the source itself. Crystals and Miller indices (hkl) have to be matched such that the resulting lattice spacing d is close to half the spectral wavelength used for imaging, to fulfill the Bragg equation with a Bragg angle near 90∘ which reduces astigmatism. Only a few suitable crystal and spectral-line combinations have been identified for applications in the literature, suggesting that x-ray imaging using spherical crystals is constrained to a few chance matches. In this article, after performing a systematic, automated search over more than 9 × 106 possible combinations for x-ray energies between 1 and 25 keV, for six crystals with arbitrary Miller-index combinations hkl between 0 and 20, we show that a matching, efficient crystal and spectral-line pair can be found for almost every Heα or Kα x-ray source for the elements Ne to Sn. Using the data presented here it should be possible to find a suitable imaging combination using an x-ray source that is specifically selected for a particular purpose, instead of relying on the limited number of existing crystal imaging systems that have been identified to date.
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