Arthur C. Carpenter

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.

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 of radiation tolerant FPGAs for the LLNL nanosecond gated CMOS camera program

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.

Design and characterization of a novel 1-ns multi-frame imager for the Ultra-Fast X-ray Imager (UXI) program at Sandia National Laboratories

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.

Performance characterization of a four-frame nanosecond gated hybrid CMOS image sensor

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.

Capacitor transient effects in a high-dose-rate environment

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.

Radiation effects on active camera electronics in the target chamber at the National Ignition Facility

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.