The Daedalus sensor is the next version of the nanosecond time-gated, multi-frame hybridized CMOS (hCMOS) x-ray sensor, developed by Sandia National Laboratories (SNL). The Daedalus sensor leverages previous hCMOS features such as nanosecond gated frames while expanding features for increased record length, improved full well depth, and one-side abutment capability. The second version of the Daedalus sensor, the DV2, resolves an increased record length feature called interlacing in addition to the sensor’s ability to hold the integrated electrical charge from photocurrent for longer periods of time needed for full dynamic range during readout. The DV2 sensor characteristics, including background oscillations, skew, key sensor features for timing and high full well, and mapping of the internal temperature sensor are presented and discussed.
Many questions regarding dynamic materials could be answered by using time-resolved ultra-fast imaging techniques to characterize the physical and chemical behavior of materials in extreme conditions and their evolution on the nanosecond scale. In this work, we perform multi-frame phase-contrast imaging (PCI) of micro-voids in low density polymers under laser-driven shock compression. At the Matter in Extreme Conditions (MEC) Instrument at the Linac Coherent Light Source (LCLS), we used a train of four x-ray free electron laser (XFEL) pulses to probe the evolution of the samples. To visualize the void and shock wave interaction, we deployed the Icarus V2 detector to record up to four XFEL pulses, separated by 1-3 nanoseconds. In this work, we image elastic waves interacting with the micro-voids at a pressure of several GPa. Monitoring how the material’s heterogeneities, like micro-voids, dictate its response to a compressive wave is important for benchmarking the performances of inertial confinement fusion energy materials. For the first time in a single sample, we have combined an ultrafast x-ray framing camera and four XFEL pulse train to create an ultrafast movie of micro-void evolution under laser-driven shock compression. Eventually, we hope this technique will resolve the material density as it evolves dynamically under laser shock compression.
Electron-based diagnostics at the National Ignition Facility use Sandia’s Icarus sensors for ultrafast imaging. However, the electron detection performance of these sensors has remained mostly unknown. Previous work characterized the singulated Common Anode photodiode structure of the ”Furi” and ”Hippogriff” but did not include the Common Cathode photodiode structure of the Icarus. Using a fully fabricated Icarus sensor, we measured the cross-sectional geometries and modeled the expected performance; then, we measured the sensor’s EQE, quantum yield, and charge gain with an electron gun. These measurements were essential to understanding the space-charge limitations of the electron-based diagnostics that use them.
KEYWORDS: Cameras, National Ignition Facility, Logic, Field programmable gate arrays, Imaging systems, Sensors, Data modeling, X-ray imaging, Diagnostics, Power supplies
The National Ignition Facility’s (NIF) high-yield DT shots create a harsh radiation environment that can cause electronics to malfunction. This paper documents various design tradeoffs and techniques used for a Microsemi FPGA to reduce the impact of Single Event Upsets (SEUs) that enable a camera to capture images in the NIF target chamber during a high-yield shot.
KEYWORDS: Sensors, National Ignition Facility, Imaging systems, Diagnostics, Fringe analysis, Pulsed laser operation, Camera shutters, Cameras, Spatial resolution, Near field
Characterization data for the Icarus 2 hybrid-CMOS (hCMOS) imager using near-infrared (NIR) laser pulses is presented. The Icarus 2 hCMOS imagers are four-frame burst mode cameras, with a 1024 x 512 pixel array and 25μm spatial resolution. Designed and built by Sandia National Laboratory for the Ultra-Fast X-ray Imager (UXI) program where they have been used to capture X-ray images at LLNL’s National Ignition Facility and during HED physics experiments. Temporal and spatial characterization is performed using NIR, 1053nm and 1064nm, laser pulses ranging from 43-ps to 20ns. Specific results include gate response, internal reflections, off-gate sensitivity, side-to-side timing skew, and response to a characteristic NIF-like laser pulse. Comparisons between a commercial gated, intensified CCD camera and a commercial time-integrated CMOS camera are included when relevant.
Lawrence Livermore’s National Ignition Facility (NIF) requires a radiation tolerant video camera to remotely monitor varied activities in and around the NIF target chamber. Our present suite of monitor cameras must be either, removed during high yield shots, requiring substantial resources or left in place which greatly reduces their life expectancy. Our goal was to develop a relatively inexpensive, radiation tolerant monitor camera which could be left in place during high yield laser experiments yet continue to give quality data for up to (5) years of operation or about 250 high yield shots. The camera was built around the CMOSIS CMV 2000 / 4000 sensor. Camera components were chosen based on their radiation tolerant performance at the Cobham radiation test facility in CO Springs. The prototype camera was tested both at Cobham and on the NIF during high yield shots. We will present test results as well as predictions for camera life expectancy.
At the National-Ignition-Facility (NIF) and other laser facilities, X-ray transmission photocathodes are used in streak cameras and pulse-dilation framing cameras with temporal resolution well below 100 ps. For X-ray imaging quality assurance, signal-to-noise ratios of at least a couple, and optimally higher, have to be achieved. The signal-to-noise ratio depends on the photon influence and the Detective Quantum Efficiency (DQE). X-ray photocathodes are notoriously noisy, since they have large pulse height distributions, and their DQE is both material and photon-energy dependent. Furthermore, for high temporal resolution, in pulse dilation instruments space charge effects may further limit the achievable signal-to-noise ratio. Here, we look into details on what to consider when choosing photocathode materials to optimize the achievable signal-to-noise and touch on further potential improvements using structured photocathodes.
The Icarus camera system, combining a sensor developed by Sandia and readout electronics by LLNL, provides 0.5 Hz bursts of four frames with 3 ns separation. The sensor has 1024×512 25 μm pixels and is 25 μm thick. The system was developed for single line-of-sight measurements at the ns time scale for electrons and X-rays at facilities such as NIF. We report on initial tests of the Icarus system with hard X-rays pulse pairs with nanosecond time spacings at the LCLS, a newly available beam mode. We describe noise, gate profiles, gain, cross-talk, persistence, linearity, and quantum efficiency for the first version of the sensor. We present evidence of the suitability of the system for science measurements at a free electron laser with an X-ray pump X-ray probe experiment. We expect further developments of the technology to allow use of 350 ps bunch separation from the LCLS accelerator and, with a pulsed delay tube like DIXIE, to eventually reach sub-25 ps time-resolved X-ray imaging of processes such as plasma evolution.
Since 2015 a high-speed (minimum integration time ≈ 2 ns) gated CMOS camera with a “Furi” sensor has been used in the G-LEH diagnostic at the National Ignition Facility to record time-resolved X-ray images of the targets in hundreds of high energy density physics experiments. As these images were analyzed, it became apparent that a more detailed characterization of the camera was needed — specifically, the gate timing profile and responsivity of each pixel — in order to correctly interpret the dynamics in the images. To this end, a pixel-level characterization of the G-LEH Furi camera was recently performed using the COMET laser as a short-pulse ( < 20 ps ) X-ray source. This paper describes the experimental setup and key results for several different timing modes of the camera. The actual widths of the pixel gate profiles were found to be wider than the design goals, with minimum width of ≈ 2 ns. The absolute timing of the pixel gates was measured relative to the output Monitor pulse, reducing the uncertainty in previous timing estimates. Most importantly, pixel-level maps have been produced that show the distribution of responsivity, gate profile width, and gate timing delay across the sensor array, enabling more accurate comparison of the timing and brightness of image features at different locations on the sensor.
This work was performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Security, LLC, under Contract No. DE-AC52- 07NA27344.
The Nano-Second Gated CMOS Camera (NSGCC) team at Lawrence Livermore National Laboratory has developed a radiation tolerant camera for Inertial Confinement Fusion (ICF) experiments at NIF with total yields of 10^16 neutrons. To achieve the desired level of operational reliability in a prompt dose environment, several firmware hardening strategies were evaluated, such as redundancy, auto-recovery from single-event upsets (SEU), and remote manual recovery if a SEU causes the system to hang. These approaches work well in a low-dose rate space environment; however, it was not clear how they would perform in a high-dose rate environment. The team generated several exploratory FPGA firmware builds with varying levels of protective circuitry and timing margin, subjected the camera to prompt dose radiation using a 20 ns short pulse x-ray source, and varied the dose. Based on this testing, a hardening strategy to achieve the highest level of radiation tolerance was identified, resulting in an FPGA firmware design that had a high probability of remaining operational in NIF’s radiation environment during a high yield shot.
At the National Ignition Facility, new designs for x-ray diagnostics and ICF targets place high energy density capacitors in the harsh radiation environment of the target chamber. In these applications, dielectric breakdown would be catastrophic. This study considers the behavior of three dielectric types in a prompt-dose radiation environment; aluminum electrolytic, multilayer ceramic, and metalized polypropylene. The experiments exposed the capacitors with a flash x-ray machine and measured the internal discharge from shot-to-shot for a range of doses. From the results, the thinner aluminum electrolytic dielectrics internally discharged less than the thicker ones. The results from the flash x-ray source were compared to a limited set of data taken in NIF’s neutron test-well. The aluminum electrolytic and metalized polypropylene capacitors did not fail while biased at their rated voltage during eight shots in NIF, mostly between 1e9 n/cm2 and 4e9 n/cm2.
L. Claus, A. Boone, T. England, L. Fang, Q. Looker, B. Mitchell, A. Montoya, J. Porter, M. Sanchez, A. Vigil, E. Hurd, A. Carpenter, M. Dayton, C. Durand, G. Rochau
The Daedalus camera is a second-generation imager for the Ultra-Fast X-ray Imager (UXI) program, achieving 1 ns, time-gated, multi-frame image sets for High Energy Density (HED) physics experiments. Daedalus includes a 1024 x 512 pixel array with 25 μm spatial resolution with three frames of storage per pixel with three times larger full well (1.5 million e-) than the last generation camera, Icarus. Daedalus incorporates an improved timing generation and distribution concept to facilitate broader user configurability and application space while improving timing resolution to 1 ns. Electrical timing measurements demonstrated 1 nanosecond shutters. Analog dynamic range is sufficient to provide the expected full well. Read noise of 210 e- has been measured, exceeding design goals. 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.
In this paper characterization data for two versions of a gated hybrid-CMOS image sensor are presented. These sensors, referred to as Icarus and Icarus 2, are two and four frame burst mode cameras respectively, with 1024 x 512 pixel array and 25μm spatial resolution. Designed and built by Sandia National Laboratory for the Ultra-Fast X-ray Imager (UXI) program, they have been used to capture X-ray images at LLNL’s National Ignition Facility and during High Energy Density Physics (HEDP) experiments. Performance data including timing mode, oscillator performance, and gate widths for the Icarus series sensors is covered; this is the first reported data for the four frame Icarus 2 sensors. Additional impacts on device performance due to diode passivation layer for low energy electron sensitivity and low signal linearity are presented. A discussion of oscillator performance, bond wire inductance, and linear response is also covered.
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.
The National Ignition Facility’s (NIF) harsh radiation environment can cause electronics to malfunction during high-yield DT shots. Until now there has been little experience fielding electronic-based cameras in the target chamber under these conditions; hence, the performance of electronic components in NIF’s radiation environment was unknown. It is possible to purchase radiation tolerant devices, however, they are usually qualified for radiation environments different to NIF, such as space flight or nuclear reactors. This paper presents the results from a series of online experiments that used two different prototype camera systems built from non-radiation hardened components and one commercially available camera that permanently failed at relatively low total integrated dose. The custom design built in Livermore endured a 5 × 1015 neutron shot without upset, while the other custom design upset at 2 × 1014 neutrons. These results agreed with offline testing done with a flash x-ray source and a 14 MeV neutron source, which suggested a methodology for developing and qualifying electronic systems for NIF. Further work will likely lead to the use of embedded electronic systems in the target chamber during high-yield shots.
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.
KEYWORDS: Cameras, Camera shutters, X-ray imaging, National Ignition Facility, Sensors, Photodiodes, X-rays, Picosecond phenomena, X-ray characterization, Signal to noise ratio
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.
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