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A 16-image Kirkpatrick–Baez (KB)–type x-ray microscope consisting of compact KB mirrors [F. J. Marshall, Rev. Sci. Instrum. 83, 10E518 (2012)] has been assembled for the first time with mirrors aligned to allow it to be coupled to a high-speed framing camera. The high-speed framing camera has four independently gated strips whose emission sampling interval is ~30 ps. Images are arranged four to a strip with ~60-ps temporal spacing between frames on a strip. By spacing the timing of the strips, a frame spacing of ~15 ps is achieved. A framed resolution of ~6-μm is achieved with this combination in a 400-μm region of laser-plasma x-ray emission in the 2- to 8-keV energy range. A principal use of the microscope is to measure the evolution of the implosion stagnation region of cryogenic DT target implosions on the University of Rochester’s OMEGA Laser System [T. R. Boehly et al., Opt. Commun. 133, 495 (1997)]. The unprecedented time and spatial resolutions achieved with this framed, multi-image KB microscope have made it possible to accurately determine the cryogenic implosion core emission size and shape at the peak of stagnation. These core size measurements, taken in combination with those of ion temperature, neutron-production temporal width, and neutron yield allow for inference of core pressures, currently exceeding 50 Gbar in OMEGA cryogenic target implosions [Regan et al., Phys. Rev. Lett. 117, 025001 (2016)]. [ABSTRACT FROM AUTHOR]

Inertial confinement fusion (ICF) requires a high resolution (∼10 μm) neutron imaging system to observe deuterium and tritium (DT) core implosion asymmetries. A new large (150 mm entrance diameter: scaled for Laser MégaJoule [P. A. Holstein, F. Chaland, C. Charpin, J. M. Dufour, H. Dumont, J. Giorla, L. Hallo, S. Laffite, G. Malinie, Y. Saillard, G. Schurtz, M. Vandenboomgaerde, and F. Wagon, Laser and Particle Beams 17, 403 (1999)]) neutron imaging detector has been developed for such ICF experiments. The detector has been fully characterized using a linear accelerator and a 60Co γ-ray source. A penumbral aperture was used to observe DT-gas-filled target implosions performed on the OMEGA laser facility. [T. R. Boehly, D. L. Brown, R. S. Craxton, R. L. Keck, J. P. Knauer, J. H. Kelly, T. J. Kessler, S. A. Kumpan, S. J. Loucks, S. A. Letzring, F. J. Marshall, R. L. McCrory, S. F. B. Morse, W. Seka, J. M. Soures, and C. P. Verdon, Opt. Commun. 133, 495 (1997)] Neutron core images of 14 MeV with a resolution of 15 μm were obtained and are compared to x-ray images of comparable resolution. [ABSTRACT FROM AUTHOR]

X-ray-sensitive film is used for a variety of imaging and spectroscopic diagnostics for high-temperature plasmas. Replacement film must be found as older films are phased out of production. Biomax-MS is a “T-grain” class of film that is proposed as a replacement for Kodak DEF and a model of its response to x rays is presented. Data from dimensional measurements of the film, x-ray transmission measurements, scanning electron microscopy micrograph images, and x-ray calibration are used to develop this sensitivity model of Biomax-MS film as a function of x-ray energy and angle of incidence. Relative response data provide a check of the applicability of this model to determine the x-ray flux from spectrum data. This detailed film characterization starts with simple mathematical models and extends them to T-grain–type film. [ABSTRACT FROM AUTHOR]

A proton emission imaging system has been developed and used extensively to measure the nuclear burn regions in the cores of inertial confinement fusion implosions. Three imaging cameras, mounted to the 60-beam OMEGA laser facility [T. R. Boehly et al., Opt. Commun. 133, 495 (1997)], use the penetrating 14.7 MeV protons produced from D 3He fusion reactions to produce emission images of the nuclear burn spatial distribution. The technique relies on penumbral imaging, with different reconstruction algorithms for extracting the burn distributions of symmetric and asymmetric implosions. The hardware and design considerations required for the imaging cameras are described. Experimental data, analysis, and error analysis are presented for a representative symmetric implosion of a fuel capsule with a 17-μm-thick plastic shell and 18 atm D 3He gas fill. The radial burn profile was found to have characteristic radius Rburn, which we define as the radius containing half the D 3He reactions, of 32±2 μm (burn radii measured for other capsule types range from 20 to 80 μm). Potential sources of error due to proton trajectory changes from interactions with electric fields and scattering in capsule and camera hardware are estimated with simple analytic and Monte Carlo calculations; they are predicted to be small compared with statistical errors. Experimental tests were performed to look for any inconsistencies between results from different cameras and different imaging geometries, or evidence of error due to ambient electric or magnetic fields, and none were found. [ABSTRACT FROM AUTHOR]

We describe a multiple monochromatic x-ray imager designed for implosion experiments. This instrument uses an array of pinholes in front of a flat multilayered Bragg mirror to provide many individual quasimonochromatic x-ray pinhole images spread over a wide spectral range. We discuss design constraints and optimizations, and we discuss the specific details of the instrument we have used to obtain temperature and density maps of implosion plasmas. [ABSTRACT FROM AUTHOR]

Using a penumbral technique with a biconical aperture we have obtained neutron images with a spatial resolution of 20 µm. Implosions of DT filled CH microballons of ∼932 µm diameter at the Omega laser produced asymmetric images with full width at half maximum of 40 and 80 µm for 18.9 µm thick CH shells. Image sizes and shapes are in good agreement with the 4-7 keV x-ray images of the same capsule. The improved resolution compared to our previous measurements arises from a longer line-of-sight (13 vs 8 m) and a new neutron detector obtained by filling an array of glass capillaries with a high optical index scintillator. [ABSTRACT FROM AUTHOR]

A Kirkpatrick-Baez (KB) x-ray microscope with a streak camera at the image plane is being developed for OMEGA to increase the sensitivity and spatial resolution in planar direct-drive hydrodynamic stability experiments. A four-mirror, iridium-coated, KB optic has been designed to couple to the high-current PJX streak tube. This design, using a bilayer Ir/Cr coating and a relatively high grazing angle of 2.1°, provides up to three-orders-of-magnitude-higher throughput than a pinhole array coupled to an x-ray framing camera. The angle of reflection has been calculated to maximize the solid angle and the coating reflectivity. The spectral window, peaked at 1.56 keV with a FWHM of about 400 eV, eliminates the contrast impairment caused by the high-energy x-ray emission of the backlighter. Calculations show that the device is capable of registering 2-µm spatial features over a field of view of 120 µm. A series of sputtering and e-beam evaporation deposition tests have been performed on superpolished (<0.1 nm rms) test plates to determine the density and smoothness of the film. Detailed ray tracing has been used to fully characterize and optimize the optical parameters of the system, including diffraction response. Its resolving capabilities and throughput have been confirmed by several test experiments. [ABSTRACT FROM AUTHOR]

The spectroscopic analysis of x-ray narrow-band images and space-integrated x-ray line spectra from argon-doped deuterium-filled inertial confinement fusion implosion experiments yields information about the spatial profiles in the compressed core. We discuss the analysis of direct-drive implosion experiments at OMEGA, in which images were obtained with a multimonochromatic imaging instrument. The analysis method considers data based on the argon Heβ and Lyβ spectral features and their associated Li- and He-like satellites. The temperature gradient structure is investigated by using the sensitivity of the Lyβ/Heβ emissivity ratio to the temperature. [ABSTRACT FROM AUTHOR]

Compact Kirkpatrick-Baez microscope mirror components for use in imaging laser-plasma x-ray emission have been manufactured, coated, and tested. A single mirror pair has dimensions of 14 × 7 × 9 mm and a best resolution of ∼5 μm. The mirrors are coated with Ir providing a useful energy range of 2-8 keV when operated at a grazing angle of 0.7°. The mirrors can be circularly arranged to provide 16 images of the target emission a configuration best suited for use in combination with a custom framing camera [F. J. Marshall, J. A. Oertel, and P. J. Walsh, Rev. Sci. Instrum. 75, 4045 (2004)]. An alternative arrangement of the mirrors would allow alignment of the images with a four-strip framing camera such as described in D. K. Bradley et al. [Rev. Sci. Instrum. 66, 716 (1995)]. [ABSTRACT FROM AUTHOR]

A new method for studying the modulations in the ρΔR of imploded shells is introduced: using a recently developed pinhole-array x-ray spectrometer, core images are obtained at energies below and above the K-edge energy of a titanium dopant. The ratio of these images reflects the nonuniformity of the cold shell around the time of peak compression, independently of modulation in core emission. The two-dimensional images of ρΔR modulations are of interest in laser fusion because they show the final result of unstable implosion evolution. The measured average ρΔR of the cold shell and the amplitude and spectrum of its modulations are in agreement with the results of two-dimensional code simulations that include imprinting of laser nonuniformity on the target. © 2000 American Institute of Physics. [ABSTRACT FROM AUTHOR]