Liam D. Claus

High-brightness, high-spatial-resolution, 6.151keV x-ray imaging of inertial confinement fusion capsule implosion and complex hydrodynamics experiments on Sandia’s Z accelerator (invited)

When used for the production of an x-ray imaging backlighter source on Sandia National Laboratories’ 20MA, 100ns rise-time Z accelerator [M. K. Matzen et al., Phys. Plasmas 12, 055503 (2005)], the terawatt-class, multikilojoule, 526.57nm Z-Beamlet laser (ZBL) [P. K. Rambo et al., Appl. Opt. 44, 2421 (2005)], in conjunction with the 6.151keV, Mn–Heα curved-crystal imager [D. B. Sinars et al., Rev. Sci. Instrum. 75, 3672 (2004)], is capable of providing a high quality x radiograph per Z shot for various high-energy-density physics experiments. Enhancements to this imaging system during 2005 have led to the capture of inertial confinement fusion capsule implosion and complex hydrodynamics images of significantly higher quality. The three main improvements, all leading effectively to enhanced image plane brightness, were bringing the source inside the Rowland circle to approximately double the collection solid angle, replacing direct exposure film with Fuji BAS-TR2025 image plate (read with a Fuji BAS-5000 sc...

An overview of the Ultrafast X-ray Imager (UXI) program at Sandia Labs

The Ultra-Fast X-ray Imager (UXI) program is an ongoing effort at Sandia National Laboratories to create high speed, multi-frame, time gated Read Out Integrated Circuits (ROICs), and a corresponding suite of photodetectors to image a wide variety of High Energy Density (HED) physics experiments on both Sandia’s Z-Machine and the National Ignition Facility (NIF). The program is currently fielding a 1024 x 448 prototype camera with 25 μm pixel spatial resolution, 2 frames of in-pixel storage and the possibility of exchanging spatial resolution to achieve 4 or 8 frames of storage. The camera’s minimum integration time is 2 ns. Minimum signal target is 1500 e- rms and full well is 1.5 million e-. The design and initial characterization results will be presented as well as a description of future imagers.

Design and characterization of an improved, 2 ns, multi-frame imager for the Ultra-Fast X-ray Imager (UXI) program at Sandia National Laboratories

The Icarus camera is an improvement on past imagers (Furi and Hippogriff) designed for the Ultra-Fast X-ray Imager (UXI) program to deliver ultra-fast, time-gated, multi-frame image sets for High Energy Density Physics (HEDP) experiments. Icarus is a 1024 × 512 pixel array with 25 μm spatial resolution containing 4 frames of storage per pixel. It has improved timing generation and distribution components and has achieved 2 ns time gating. Design improvements and initial characterization and performance results will be discussed. Sandia National Laboratories is a multimission laboratory managed and operated by National Technology and Engineering Solutions of Sandia LLC, a wholly owned subsidiary of Honeywell International Inc. for the U.S. Department of Energy’s National Nuclear Security Administration under contract DE-NA0003525.

Initial characterization results of a 1024x448, 25-μm multi-frame camera with 2ns integration time for the Ultrafast X-ray Imager (UXI) program at Sandia National Laboratories

The Hippogriff camera developed at Sandia National Laboratories as part of the Ultra-Fast X-ray Imager (UXI) program is a high-speed, multi-frame, time-gated imager for use on a wide variety of High Energy Density (HED) physics experiments on both Sandia’s Z-Machine and the National Ignition Facility. The camera is a 1024 x 448 pixel array with 25 μm spatial resolution, containing 2 frames per pixel natively and has achieved 2 ns minimum integration time. It is sensitive to both optical photons as well as soft X-rays up to ~6 keV. The Hippogriff camera is the second generation UXI camera that contains circuitry to trade spatial resolution for additional frames of temporal coverage. The user can reduce the row-wise spatial resolution from the native 25 μm to increase the number of frames in a data set to 4 frames at 50 μm or 8 frames at 100 μm spatial resolution. This feature, along with both optical and X-ray sensitivity, facilitates additional experimental flexibility. Minimum signal is 1500 erms and full well is 1.5 million e-.

The dilation aided single–line–of–sight x–ray camera for the National Ignition Facility: Characterization and fielding

Crystal x-ray imaging is frequently used in inertial confinement fusion and laser-plasma interaction applications as it has advantages compared to pinhole imaging, such as higher signal throughput, better achievable spatial resolution, and chromatic selection. However, currently used x-ray detectors are only able to obtain a single time resolved image per crystal. The dilation aided single-line-of-sight x-ray camera described here was designed for the National Ignition Facility (NIF) and combines two recent diagnostic developments, the pulse dilation principle used in the dilation x-ray imager and a ns-scale multi-frame camera that uses a hold and readout circuit for each pixel. This enables multiple images to be taken from a single-line-of-sight with high spatial and temporal resolution. At the moment, the instrument can record two single-line-of-sight images with spatial and temporal resolution of 35 μm and down to 35 ps, respectively, with a planned upgrade doubling the number of images to four. Here we present the dilation aided single-line-of-sight camera for the NIF, including the x-ray characterization measurements obtained at the COMET laser, as well as the results from the initial timing shot on the NIF.

Sub-nanosecond single line-of-sight (SLOS) x-ray imagers (invited)

A new generation of fast-gated x-ray framing cameras have been developed that are capable of capturing multiple frames along a single line-of-sight with 30 ps temporal resolution. The instruments are constructed by integrating pulse-dilation electron imaging with burst mode hybrid-complimentary metal-oxide-semiconductor sensors. Two such instruments have been developed, characterized, and fielded at the National Ignition Facility and the OMEGA laser. These instruments are particularly suited for advanced x-ray imaging applications in Inertial Confinement Fusion and High energy density experiments. Here, we discuss the system architecture and the techniques required for tuning the instruments to achieve optimal performance. Characterization results are also presented along with planned future improvements to the design.

A characterization technique for nanosecond gated CMOS x-ray cameras

We present a characterization technique for nanosecond gated CMOS cameras designed and built by Sandia National Laboratory under their Ultra-Fast X-ray Imager program. The cameras have been used to record images during HED physics experiments at Sandia’s Z Facility and at LLNL’s National Ignition Facility. The behavior of the camera’s fast shutters was not expected to be ideal since they propagate over a large pixel array of 25 mm x 12 mm, which could result in shutter timing skew, variations in the FWHM, and variations in the shutter’s peak response. Consequently, a detailed characterization of the camera at the pixel level was critical for interpreting the images. Assuming the pixel’s photo-response was linear, the shutter profiles for each pixel were simplified to a pair of sigmoid functions using standard non-linear fitting methods to make the subsequent analysis less computationally intensive. A pixel-level characterization of a ”Furi” camera showed frame-to-frame gain variations that could be normalized with a gain mask and significant timing skew at the sensor’s center column that could not be corrected. The shutter profiles for Furi were then convolved with data generated from computational models to forward fit images collected with the camera.

Single Line of Sight CMOS radiation tolerant camera system design overview

This paper covers the preliminary design of a radiation tolerant nanosecond-gated multi-frame CMOS camera system for use in the NIF. Electrical component performance data from 14 MeV neutron and cobalt 60 radiation testing will be discussed. The recent development of nanosecond-gated multi-frame hybrid-CMOS (hCMOS) focal plane arrays by the Ultrafast X-ray Imaging (UXI) group at Sandia National Lab has generated a need for custom camera electronics to operate in the pulsed radiation environment of the NIF target chamber. Design requirements and performance data for the prototype camera system will be discussed. The design and testing approach for the radiation tolerant camera system will be covered along with the evaluation of commercial off the shelf (COTS) electronic component such as FPGAs, voltage regulators, ADCs, DACs, optical transceivers, and other electronic components. Performance changes from radiation exposure on select components will be discussed. Integration considerations for x-ray imaging diagnostics on the NIF will also be covered.

Design and implementation of a gated-laser entrance hole imaging diagnostic (G-LEH-1) at NIF

Gated x-ray images through the laser entrance hole (LEH) of a hohlraum can provide critical information for ICF experiments at the National Ignition Facility (NIF), such as the size of the LEH vs time, the growth of the gold bubble1, and the change in the brightness of inner beam spots due to time-varying cross beam energy transfer2. Incorporating a high-speed multi-frame CMOS x-ray imager developed by Sandia National Laboratories3,4 into the existing Static X-ray Imager (SXI) diagnostic5 at NIF, the new Gated LEH Imager #1 (G-LEH-1) diagnostic is capable of capturing two to four LEH images per shot on its 1024x448 pixel photo detector array, with integration times as low as 2 ns per frame. The design of this diagnostic and its implementation on NIF will be presented.

The single-line-of-sight, time-resolved x-ray imager diagnostic on OMEGA

The single-line-of-sight, time-resolved x-ray imager (SLOS-TRXI) on OMEGA is one of a new generation of fast-gated x-ray cameras comprising an electron pulse-dilation imager and a nanosecond-gated, burst-mode, hybrid complementary metal-oxide semiconductor sensor. SLOS-TRXI images the core of imploded cryogenic deuterium-tritium shells in inertial confinement fusion experiments in the ∼4- to 9-keV photon energy range with a pinhole imager onto a photocathode. The diagnostic is mounted on a fixed port almost perpendicular to a 16-channel, framing-camera-based, time-resolved Kirkpatrick-Baez microscope, providing a second time-gated line of sight for hot-spot imaging on OMEGA. SLOS-TRXI achieves ∼40-ps temporal resolution and better than 10-μm spatial resolution. Shots with neutron yields of up to 1 × 1014 were taken without observed neutron-induced background signal. The implosion images from SLOS-TRXI show the evolution of the stagnating core.