This PDF file contains the front matter associated with SPIE Proceedings Volume 10763, including the Title Page, Copyright information, Table of Contents, Author and Conference Committee lists.

To obtain two kinds of tomograms at two different X-ray energy ranges simultaneously, we have constructed a dualenergy (DE) X-ray photon counter with a room-temperature cadmium telluride (CdTe) detector. X-ray photons are detected using the CdTe detector system, and event pulses from an amplifier module are sent to three comparators simultaneously to determine three threshold energies of 33, 48 and 50 keV. The DE counter has energy-range and - region selectors, and the energy range and region are 33-48 and beyond 50 keV (50-100 keV); the maximum energy corresponds to the tube voltage. We performed DE computed tomography (DE-CT) using four lead pinholes at a tube voltage of 100 kV. In Gd-K-edge CT at a range of 50-100 keV, Gd media were observed at high contrasts. The spatial resolutions were 0.5×0.5 mm², and the exposure time for DE-CT was 19.6 min at a total rotation angle of 360°. At a tube voltage of 100 kV and a current of 0.22 mA, the count rate was 36 kilocounts per second.

In this work, we continue the study of an optical based method for annihilation photon detection with the potential for a dramatic improvement in time resolution for time-of-flight positron emission tomography (ToF-PET). Previous work has shown that the refractive index of materials such as bismuth silicon oxide (BSO) and cadmium telluride (CdTe) can be modulated by the charge cloud created by annihilation photon interactions, though the ultrafast nature of the index modulation process remains untested. At the Linac Coherent Light Source (LCLS) at the SLAC National Accelerator Laboratory, the arrival time of X-ray pulses with photon energies between 0.5–10 keV is routinely detected with femtosecond scale time resolution. The ionizing interactions alter the local band structure in optically transparent insulators, changing the refractive index. Using a frequency chirped visible continuum probe pulse for a monotonic wavelength-to-time mapping, we measured the induced refractive index modulation, with interferometric sensitivity, and a sub-picosecond time resolution. In this work, we show that femtosecond scale resolution can be achieved for photon arrival time measurement using the refractive index modulation mechanism. This new detection concept has the potential to also achieve significantly improved timing capability for ToF-PET.

We have developed a preclinical rabbit cardiac SPECT system by re-engineering a classical clinical SPECT scanner with state-of-the-art electronics and control systems. Notable features include digital waveform capture of the time-dependent outputs of the photomultiplier tubes (PMT). The digitization of the scintillation pulses allows for the incorporation of the entire waveform into the maximum-likelihood estimation (MLE) of event parameters (x, y, energy, etc.), rather than one scalar (i.e. integrated current). We present here details of the waveform-inclusive MLE, the measurements of the mean-detector-response functions, and the determination of the point spread function, along with the associated acceleration via graphics-processor-unit (GPU) programming. Additionally, calibration algorithms of the system are discussed.

Light field SPECT (L-SPECT) is an improved version of SPECT and works by introducing the concept of plenoptic imaging to reduce scanning time and to increase the amount of detected information. In L-SPECT, a tungsten pinhole array is used as a collimator to differentiate the incoming direction of radiation, rather than only allowing radiation from a set direction dictated by a conventional tube collimator. The distance of the pinhole array to the sensors’ plane is so that the sensors behind each pinhole are only exposed through that pinhole alone. This paper investigates the effects of the pinholes’ diameter and pitch over the reconstruction resolution using simulation experiments. In this proposed reconstruction algorithm, a ray is back projected from the centre of each detector with non-zero pixel value via the corresponding pinhole’s centre, and towards the area of interest with 128×128×128 voxels. The projected rays’ intersections are identified by using ray tracing and the voxels at which they intersect are updated by incrementing with the sum of the pixel values from each detector involved. Experiments are conducted with pinhole arrays of 100×100, 50×50, 30×30 and pinhole diameter of 0.5mm, 1mm and 2mm. Reconstruction is conducted for various simulated objects. Results indicate that when the number of pinholes is increased, the diameter of the pinholes should be reduced to maintain spatial resolution. Moreover, a reconstruction performed by using only 12 projections shows similar quality for the same with 36 and 72 projections. The analysis of the proposed reconstruction algorithm shows that it improves spatial resolution over the filtered back projection algorithm. Reconstruction quality can be further improved by considering scattering loss and photon attenuation.

Scintillator-based gamma-ray detectors convert gamma-ray photons into a burst of scintillation photons, and then into a pulse-shaped electrical signal. By digitizing the pulse waveform, analyses that require information about the shape of the pulse can be performed, such as pulse-shape discrimination, pile-up detection and maximum- likelihood event-parameter estimation of position, energy and time. We have developed an analog-to-digital conversion (ADC) method that hugely reduces the complexity of the data-acquisition (DAQ) system while retaining pulse-shape information, and increases the amount of information that can be extracted from detected gamma rays compared to analog methods. The new DAQ system is based on a modified 2-bit sigma-delta modulator (SDM), in which the possible outputs (00, 01, 10 and 11) are decoded in such a way that they don’t necessarily maintain a linear relationship between them. This makes it possible to optimize the SDM algorithm for different characteristic pulse shapes in order to extract as much information as possible. The optimization method that we present in this work is scintillation-crystal specific, but the use of the ADC method is not limited to gamma-ray detection.

The LAPPD is a 400 cm^2 microchannel plate photomultiplier with a timing resolution better than 100 pS. It has sensitivity to single photoelectrons with a gain of ~7E6. It incorporates a bi-alkali Na2KSb photocathode, with a peak sensitivity near 360 nm. Photocathodes with quantum efficiencies as high as 30% have been fabricated. The anode has a parallel stripline configuration, with a position resolution of ~4mm or better. The large area makes the LAPPD suitable for viewing large area scintillator radiation detectors. The high speed response makes it useful for applications such as neutron detectors (i.e. Weinfurther et al., 2018), or Cerenkov light detectors for high energy physics applications. Two LAPPDs were recently used as a telescope in a 150 MeV cancer therapy proton beam, in a project designed to verify beam targeting. LAPPDs are manufactured with a borosilicate glass envelope, and a fused silica window. The microchannel plates are fabricated using a glass substrate, with 20 micron pores. Thin films are applied to the substrate with the Atomic Layer Deposition technique. These films impart the resistive and emissive qualities needed for charge multiplication within the microchannels. Recently, improvements in the deposition method for an MgO secondary electron emission film have provided a breakthrough in gain, as the MgO retains a high gain throughout the manufacturing process of the LAPPD. Recent measurements of gain, timing, position and quantum efficiency will be shown, and applications discussed.

The IAEA has developed the International Radiation Monitoring Information System (IRMIS), an international web- based application in support of the implementation of the Convention on Early Notification of a Nuclear Accident. IRMIS provides a mechanism for the reporting and visualization of large quantities of environmental radiation monitoring data during nuclear or radiological emergencies. The radiation monitoring data can be uploaded to IRMIS in the International Radiological Information Exchange (IRIX) format. A web interface has been designed in IRMIS through which authorized users may upload the reports of Emergency Data into IRMIS, either in IRIX format or using a pre-formatted spreadsheet template. These reports are subsequently reviewed and published on IRMIS by the IAEA Incident and Emergency Centre (IEC). IRIX is a technical standard developed by the IAEA in cooperation with experts from Member States and the European Commission (EC). It is designed to enable the development of interoperable systems and solutions for exchanging emergency information and data between organizations at both national and international level during a nuclear or radiological incident or emergency. IRIX is an open format developed by the IAEA based on the Extensible Markup Language (XML), which makes it both machine- and human-readable. It should be used to exchange radiological information between IAEA and RANET teams, or between any other two (or more) assisting parties, during a nuclear or radiological emergency. The IAEA has developed the IRIX format as the recommended standard to exchange information among emergency response organizations at national and international levels during a nuclear or radiological emergency. The standard covers the data content, the data format (XML), and the system interface specification. Data can include status information about a nuclear installation, information about any radioactive releases to the environment, information on protective actions taken or planned by affected countries, and environmental radiation monitoring data. The system interface specification (or web-service specification) enables organizations to interconnect their emergency information systems to automate their information exchange in an emergency. The IRIX standard allows the information to be processed quickly, summarized, and presented in an easily understood format: for example, on status boards in emergency response centres. Once the national system has been interconnected with a counterpart system, the information contained in reports in the IRIX format can be automatically exchanged via “machine-to-machine” transactions. These can replace or complement “operator-to-machine” or “operator-to-operator” information exchange, which is usually slower and not error-free. At present, US DOE/NNSA efforts to collect and share large quantities of radiological or nuclear emergency monitoring data are fragmented. The Emergency Response Group acquires data using multiple cell-nets, and communicates these data back to the Search Management Centre (SMC), which produces maps and briefing products. The RAP regions--which are vast--are using the RadResponder Network that is outside the scope of SMC and mainstream NNSA emergency response. The IAEA proposes to integrate all types of radiation data--survey, monitoring, environmental, and sampling — under one international umbrella, the International Radiation Monitoring Information System (IRMIS). The most significant restriction is that SMC is not a client server based system, whereas IRMIS is a distributed web- based application: it is managed by issuing user-level credentials with multi-level privileges. Unlike SMC, IRMIS is also independent of the origin and type of equipment used to collect the data (e.g. backpack, vehicle monitoring, or networked fixed-monitoring stations).

Rapid and efficient radiation monitoring and environmental sample collection and analysis are of primary importance in a nuclear/radiological emergency response. It is an essential step in an emergency response to characterize the intensity and geographical extent of any release of radioactive materials into the atmosphere in terms of the ground deposition and air concentrations of specific radioisotopes. In a large-scale incident/accident the radiation monitoring and environmental sampling analysis data should be compatible and comparable over large (>100 km) distances to be used for a proper assessment and prognosis of the event. This large area, beyond the control of the facility operator are defined under two off-site emergency zones (a) precautionary action zone (PAZ) and (b) urgent protective action planning zone (UPZ). This vast expanse of contaminated area requires that the data is free of built-in biases, statistical errors, free of environmental effects and overall harmonized. This article examines the different facets of data qualities that constitute meaningful emergency monitoring data at different stages of the event and draws attention to the geostatistical and other tools and techniques that facilitate harmonization.

Our team at Los Alamos National Laboratory has performed many successful energy-spectra measurements of both continuous and flash, intense radiographic sources with Compton spectrometers. In this method, a collimated beam of x-rays incident on a convertor foil ejects Compton electrons. A collimator may be inserted into the entrance of the spectrometer to select the angular acceptance of the forward-scattered electrons, which then enter the magnetic field region of the spectrometer. The position of the electrons at the magnet’s focal plane is proportional to the square root of their momentum, allowing the x-ray spectrum to be reconstructed. A Compton spectrometer with an energy range of <0.5 to 20 MeV recently measured the x-ray energy spectrum produced by the Mercury pulsed-power machine at the Naval Research Laboratory in its large-area diode configuration. These first-ever results from a distributed x-ray source will be presented.

In digital X-ray imaging, a crucial factor determining image resolution of all indirect detection systems is the spread of light in the X-ray scintillator. Currently deployed clinical x-ray detectors, with a resolution between 75 and 300 microns, are affected by such spread of light. This work demonstrates the significantly improved the resolution of an indirect X-ray scintillation detector using a new structuring approach The new structured scintillator consists of three main components: a high optical quality ‘channel plate’, a reflective material within the capillaries of the channel plate, and a polymer-based scintillating material that is incorporated in the capillaries. Channel plates, which are utilized for a variety of optical applications, are produced from bundles of hollow drawn borosilicate glass fibers, with repeated bundling and drawing reducing the diameter of the core and capillary pores down to values as low as 5 microns. These bundles are then cut to make high quality plates (‘channel plates’) with a thickness around 1 mm. Channel plates contain geometrically ordered capillary channels (about 5 million channels per square cm). The channel walls were coated with a 70 nm thick coating of Al₂O₃:W using atomic layer deposition (ALD) to optically confine the photoemission within the channel. The optical channel plates were infiltrated with a new bismuth-based scintillating polymer developed at Lawrence Livermore National Laboratory, with a photon yield of > 30,600 photons/keV for X-ray energies of 20-30 keV, a range of interest for mammography. The new scintillator plate was used to experimentally demonstrate an X-ray resolution of 10 microns (or 50 linepairs/ mm), an approximately 7 times improvement over existing scintillating detectors. A structured scintillator plate, coupled with a digital detection system may be used to improve the spatial resolution in applications such as mammography, radiography, and computed tomography.

Thallium-doped cesium iodide (CsI:Tl) single crystal is a well-known scintillator that has found many applications in nuclear science, radiography, and active interrogation of cargo in transit. It has relatively high density, high light yield, light emission matched with photodetectors and is less hygroscopic than sodium iodide. On the other hand, it has been hampered by a persistent afterglow, attributed to thermal ionization of trapped electrons (Tl⁰) followed by radiative recombination with trapped holes, which causes pulse pile-up in high count- rate applications. However, codoping by an appropriate modifier ion, especially divalent samarium and europium, has been found to be quite successful in suppressing this afterglow. But this effect had not yet been demonstrated in the crystal sizes and excitation energies relevant to real-time scanning of cargo. It is the purpose of this work to address this issue. In this work, codoping of CsI single crystal with Sm²⁺ or Eu²⁺ was carried out using the vertical Bridgman technique. Large diameter CsI crystals, in the range of 1 to 3 inches, were grown for application in sentry portal detector. The crystals were cut in the form of pillars suitable to use in the detector module and tested for after-glow. At 2 ms after excitation cut-off, the codoped CsI:Tl crystal pillars showed afterglow on the order of 0.5-0.8 % compared to 2% for CsI doped with Tl alone. In scaling up the crystal growth process for larger diameter, it was observed that Eu²⁺-codoped crystals had much better reproducibility than those codoped with Sm²⁺.

We have demonstrated a high resolution (10 micron) X-ray scintillator plate as part of an indirect X-ray detection system. Scintillator plates are typically integrated with a 2-dimensional array of photodiodes based upon amorphous Si. This paper describes an alternative digital capture system that leverages low cost CCD/CMOS cameras. Our detector has a broad set of potential applications, however the initial target application is mammography. Full-field mammography mandates an imaging area of 180mm x 240mm or larger. Very large CCD/CMOS sensors have recently been developed for high resolution cameras, such as the 250-pixel Canon camera which has sensor dimensions of 202mm x 205mm, and could conceivably be matched to our high-resolution scintillator plate without any intervening optics for magnification. However, such large format CCD/CMOS sensors have limited availability because of low production yields and high cost considerations. On the other hand, small form (36mm x 24mm) and medium format (44mm x 33mm) CCD/CMOS-based photodiodes have become widely available at low cost due to their applications in the large markets of mobile devices and consumer cameras. We have therefore developed a simple optical scheme for utilizing four small or medium format CCD/CMOS cameras to capture a larger, high-resolution image. Current systems employed in screening mammography resolve tissue features of 75-100 microns. Suspicious features found during preliminary mammographic screenings are further investigated during diagnostic mammographic tests which use a high-resolution detector that is focused over the suspicious lesion. Typically, an area less than 100mm x 80mm, the current maximum size of our high-resolution scintillation plate, is interrogated. We show that diagnostic mammography, over an area of 100mm x 80mm, could be performed using our system with a feature resolution down to 7 microns.

The application of Additive Manufacturing (AM) in medicine is extensive with the production of anatomical models, endoprosthetics, surgical guides, implants and scaffold implants. This is due to its design flexibility and cost effectiveness when geometrical complexity is required. Total hip arthroplasty is a common surgical procedure with a prevalence increase of 0.72% in 20 years that it is expected to grow faster in the next decades. The work presented demonstrates a novel non-destructive, non-contact examination method utilising X-ray Computed Tomography (XCT) and image processing. This method examines an AM bone-mimetic structure that enhances bone ingrowth and implant fixation of acetabular hip prosthesis cups. The results of the image processing analysis include information on the interconnectivity of the bone-mimetic structure, local thickness and spatial distribution.

Sandia National Laboratories has developed a method that applies machine learning methods to high-energy spectral x-ray computed tomography data to identify material composition for every reconstructed voxel in the field-of-view. While initial experiments led by Koundinyan et al. demonstrated that supervised machine learning techniques perform well in identifying a variety of classes of materials, this work presents an unsupervised approach that differentiates isolated materials with highly similar properties, and can be applied on spectral computed tomography data to identify materials more accurately compared to traditional performance. Additionally, if regions of the spectrum for multiple voxels become unusable due to artifacts, this method can still reliably perform material identification. This enhanced capability can tremendously impact fields in security, industry, and medicine that leverage non-destructive evaluation for detection, verification, and validation applications.

To obtain three kinds of tomograms at three different X-ray energy ranges simultaneously, we have constructed a triple-energy (TE) X-ray photon counter with a cooled cadmium telluride (CdTe) detector and three sets of comparators and microcomputers. X-ray photons are detected using the CdTe detector, and the event pulses produced using amplifiers are sent to three comparators simultaneously to regulate three threshold energies of 15, 33 and 50 keV. Using this counter, the energy ranges are 15-33, 33-50 and 50-100 keV; the maximum energy corresponds to the tube voltage. We performed TE computed tomography (TE-CT) at a tube voltage of 100 kV. Using four lead pinholes, three tomograms were obtained simultaneously. Iodine-K-edge CT was carried out utilizing an energy range of 33-50 keV. At a tube voltage of 100 kV and a current of 0.11 mA, the count rate was 21 kilocounts per second (kcps).

To perform low-dose low-scattering X-ray computed tomography (CT), we have constructed a dual-energy (DE) X-ray photon counter with a high-count-rate detector system and energy-range and -region selectors. The detector system consists of a cerium-doped yttrium aluminum perovskite [YAP(Ce)] crystal, a small photomultiplier tube (PMT), and an inverse amplifier for the PMT with a pulse-width extender. In DE-CT, both the X-ray source and the detector module are fixed, and the object on the turntable oscillates on the translation stage. A line beam for DE-CT is formed using a two lead (Pb) pinholes in front of the object. The scattering-photon count from the object is reduced using a Pb pinhole behind the object. To improve the spatial resolution, a 0.5-mm-diam Pb pinhole is attached to the YAP(Ce)-PMT detector. X-ray photons are detected using the detector system, and the event pulses are input to the two energy selectors. In DE-CT, the tube voltage and the maximum current were 100 kV and 0.60 mA, respectively. The energy range and region for soft and gadolinium-K-edge CT are 20-40 and beyond 50 keV (50-100 keV), respectively. The maximum count rate of DE-CT was 84 kilocounts per second, and the exposure time for tomography was 19.6 min at a total rotation angle of 360°.

The National Ignition Facility (NIF) at Lawrence Livermore National Laboratory (LLNL) uses the world’s largest and most energetic laser system to explore High-Energy-Density (HED) physics. Historically, experiments at the NIF could not radiograph an Inertial Confinement Fusion (ICF) experiment at late times due to self-emission from the capsule. The Crystal Backlighter Imager diagnostic (CBI) fielded on NIF in 2017 and has allowed radiography of ICF capsules at late times. This capability is due to the very narrow bandwidth of the imaging system, which eliminates much of the self-emission. X-rays from a backlighter source (driven by NIF beams) pass through the experiment, and the CBI uses a spherically curved crystal to reflect these x-rays at near-normal incidence (Bragg angle close to 90°) onto the detector, resulting in a very narrow bandwidth microscope. The geometry of a near-normal-incidence microscope is challenging to implement at the NIF, since the crystal must be positioned and aligned to high precision on the opposite side of the target relative to the detector. The in-chamber alignment procedure cannot take significantly longer than a simple pinhole imager, since demand for NIF shots is high and a given experiment is allotted a strict time limit. Avoiding any collision between diagnostic hardware and the target is paramount and any instrument that is placed in close proximity to a target must be able to withstand the debris produced by a 2.0 MJ NIF shot. CBI overcomes these challenges by mounting the detector and crystal on a single diagnostic instrument manipulator (DIM). The crystal is mounted on an arm that passes around the target, positioning the crystal on the opposite side of the target to the detector. This allows much of the crystal alignment to be done before the instrument is inserted into the NIF chamber, saving time. The arm that supports the crystal is mechanized so that, during insertion of the CBI, the risk of collision with the target is minimized. The CBI is designed as a robust platform that is capable of maintaining alignment tolerances of <200 microns relative to the target, as well as survive the harsh loading on the mechanical components during a NIF 2.0 MJ energy experiment. This paper discusses the engineering challenges of the CBI system.

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 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.

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.

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.

Neutron imaging is a powerful diagnostic to study inertial confinement fusion (ICF) implosions at the National Ignition Facility (NIF) using neutrons emitted in the fusion reactions. Analysis of time-gated images of the primary fusion (14.1 MeV) and down-scattered (6-12 MeV) neutrons based on their time-of-flight allows for the reconstruction of the burning hot spot undergoing fusion and the surrounding cold fuel. The Los Alamos National Laboratory (LANL) Advanced Imaging team has been providing these images since 2011. Now, two additional lines of sight are being designed and built for NIF to allow three-dimensional reconstructions. Neutron imaging relies on the conversion of neutrons into light to be captured by an imaging system through the use of a scintillator. While the current neutron imaging system utilizes a fiber scintillator array, a newly designed imaging system will consist of a thick monolithic scintillator and custom-designed lenses to collect the light. The custom lens has to resolve an image produced in the thick volume of the scintillator and therefore needs a large depth of field.

Neutron imagers based on thick apertures have become important diagnostics for the shape and size of the burning and cold fuel regions of inertial confinement fusion sources for high-energy density physics. Over time, the designs of these apertures have changed to meet the requirements of newer sources and taken advantage of improvements in manufacturing and alignment technology. In this paper, we discuss the evolution of thick apertures for neutron imaging at laser-driven ICF facilities. We describe the parameters that define the apertures and the apertures that have been fabricated and fielded. We also discuss the lessons learned with each iteration. We also discuss the impact that added features such as collinear or near-collinear γ-ray and x-ray imaging systems have had on the designs of the aperture arrays.

The National Ignition Facility at Lawrence Livermore National Laboratory is in need of a gamma-ray imaging diagnostic system to image imploding capsules for inertial confinement fusion experiments. A prototype system was designed and constructed to image 4.44 MeV gammas resulting from 12C(n,n’ γ)12C interactions with the plastic ablator. Testing of the system was undertaken at the OMEGA Laser at the University of Rochester using hard x-rays from an imploding capsule and at the High Intensity Gamma Source at Duke University using a 4.47 MeV gamma beam. The results of these tests produced a number of lessons and recommendations presented here.

Many of the new large European facilities that are in the process of coming online will be operating at high power and high repetition rates. The ability to operate at high repetition rates is important for studies including secondary source generation and inertial confinement fusion research. In these interaction conditions, with solid targets, debris mitigation for the protection of beamline and diagnostic equipment becomes of the upmost importance. These facilities have the potential to take hundreds, if not thousands, of shots every day, creating massive volumes of debris and shot materials. In recent testing of the Central Laser Facility’s High Accuracy Microtargetry Supply (HAMS) system on the mid-repetition rate Gemini facility (15 J, 40 fs, 1 shot every 20 seconds), diagnostics were deployed in order to specifically look at the debris emitted from targets designed for high repetition rate experiments. By using a high frame rate camera, it has been possible to observe and characterize some of the debris production, whilst also looking at target fratricide. Alongside these results from Gemini, we also present results of static debris measurements undertaken on the Vulcan Petawatt high energy, high power facility, where the cumulative effects of debris produced by high power laser experiments have been observed.

In this paper we demonstrate the implementation of a modified uniformly redundant array (MURA) coded aperture in the x-ray imaging of high power laser produced plasma. We detail the process of design and manufacture of a self-supporting tantalum coded aperture with ~ 50% open area to work in the 1-25 keV x-ray regime. The advantage of using a coded aperture imaging system in this high noise environment in comparison to a standard pinhole aperture is its larger solid angle and increased signal to noise. The increased solid angle allows the aperture and detector to be placed at a further distance from the interaction point. This is beneficial as it reduces the mechanics in the close proximity of the often crowded interaction region and moves the detector which can include sensitive electronics further away from the source of EMP, hard x-rays and secondary sources generated in the interaction. Here we present initial data taken on an experiment using the Vulcan Petawatt Laser at the Central Laser Facility of a prototype x-ray imager.

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.

The SEPAGE spectrometer (Spectromètre Electrons Protons A Grandes Energies) was realized within the PETAL+ project funded by the French ANR (French National Agency for Research). This plasma diagnostic, installed on the LMJ-PETAL laser facility, is dedicated to the measurement of charged particle energy spectra generated by experiments using PETAL (PETawatt Aquitaine Laser). SEPAGE is inserted inside the 10-meter diameter LMJ experimental chamber with a SID (Diagnostic Insertion System) in order to be close enough to the target. It is composed of two Thomson Parabola measuring ion spectra and more particularly proton spectra ranging from 0.1 to 20 MeV and from 8 to 200 MeV for the low and high energy channels respectively. The electron spectrum is also measured with an energy range between 0.1 and 150 MeV. The front part of the diagnostic carries a film stack that can be placed as close as 100 mm from the target center chamber. This stack allows a spatial and spectral characterization of the entire proton beam. It can also be used to realize proton radiographies.