Multispectral x-ray imaging with a pinhole array and a flat Bragg mirror

Abstract

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 quasi-monochromatic xray 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.1

Inference of ICF implosion core mix using experimental dataand theoretical mix modeling

“…Narrow-band x-ray images of the Ar line emission were recorded with the MMI (Multi-Monochromatic X-ray Imager) [26]. In this case, MMI recorded a series of pinhole sub-images over a spectral energy range encompassing the Ar Lyβ (1s-3p), Ar Heβ (1s 2 -1s3p), and Ar Lyα (1s-2p) lines.…”

Multiple-view spectrally resolved x-ray imaging observations of polar-direct-drive implosions on OMEGA

“…Specific target details for the shots discussed in this paper are shown in Table 2. Gated, spectrally resolved x-ray images were recorded with the MMI instruments available at OMEGA for fielding in direct-drive implosions [19][20][21][22][23]. The MMI imagers viewed the implosion along both equatorial and polar LOS.…”

“…In this work, we present the first PDD imaging data that is spatially, spectrally, and temporally resolved, along both the equatorial and polar LOS. This was accomplished by fielding two or three identical x-ray multi-monochromatic imager (MMI) instruments [19][20][21][22] in quasi-orthogonal ports (i.e., TIM: ten-inchmanipulators) on the OMEGA target chamber. The best data showing K-shell emission from the titanium shell tracer came from late in the implosion (well after the laser drive was turned off) and thus provide information on the shape of the implosion core during the deceleration phase, as well as electron temperature and density after spectral data unfolding, in the few hundred picoseconds leading up to bang time.…”

Processing of spectrally resolved x-ray images of inertial confinement fusion implosion cores recorded with multimonochromatic x-ray imagers

“…2). [12][13][14] The pinhole array has about a thousand 10 lm pinholes drilled on a tantalum substrate in a periodic hexagonal pattern, which, in turn, creates an array of implosion core images. The Bragg mirror consists of 300 bilayers (15 Å thick each) of boron carbide and tungsten, and reflects the collection of core images yielding a spectral resolution (E/DE $ 150) along the axis parallel to the plane of incidence.…”

“…[3][4][5][6] The ideal implosion requires spherically symmetric compression, which is hard to achieve due to laser nonuniformity, laser power imbalance, and surface roughness amplified by various hydrodynamic instabilities. To study the symmetry and spatial structure of the compressed core, various imaging instruments have been developed including the gated monochromatic x-ray imager, 7,8 monochromatic x-ray imaging with bent crystals, [9][10][11] and multimonochromatic x-ray imager (MMI) applied to indirect-drive, [12][13][14][15] and direct-drive 16,17 laser-driven implosions. Monochromatic images (or narrowband images) show core images of specific line transitions from spectroscopic tracers, which have potential to unveil the spatial structure of temperature and density in the core.…”