This PDF file contains the front matter associated with SPIE Proceedings Volume 9211, including the Title Page, Copyright information, Table of Contents, Invited Panel Discussion, and Conference Committee listing.

X-ray framing cameras based on proximity-focused micro-channel plates (MCP) have been playing an important role as diagnostics of inertial confinement fusion experiments [1]. Most of the current x-ray framing cameras consist of a single MCP, a phosphor, and a recording device (e.g. CCD or photographic films). This configuration is successful for imaging x-rays with energies below 20 keV, but detective quantum efficiency (DQE) above 20 keV is severely reduced due to the large gain differential between the top and the bottom of the plate for these volumetrically absorbed photons [2]. Recently developed diagnostic techniques at LLNL require recording backlit images of extremely dense imploded plasmas using hard x-rays, and demand the detector to be sensitive to photons with energies higher than 40 keV [3]. To increase the sensitivity in the high-energy region, we propose to use a combination of two MCPs. The first MCP is operated in low gain and works as a thick photocathode, and the second MCP works as a high gain electron multiplier [4,5]. We assembled a proof-of-principle test module by using this dual MCP configuration and demonstrated 4.5% DQE at 60 keV x-rays.

A high energy electron beam is proposed to be used for time resolved imaging measurements of hydrodynamic processes in High Energy Density Laboratory Plasma (HEDLP). Generation of a high quality sub-picosecond electron beam with present RF photocathode technologies is technologically mature and cost effective. An electron bunch train with a flexible time structure is used to penetrate a time varying high density target. By imaging the scattered electron beam, the detailed target profile and its density evolution can be accurately determined. To illustrate the concept design, an experiment is proposed based on Argonne Wakefield Accelerator (AWA) beamline. An imaging lattice design and particle tracking simulation is finished.

Testing of the gamma ray imaging system will continue at the High Intensity Gamma Source (HIGS) at Duke University. Previous testing at OMEGA gave useful information but at much lower photon energies. Utilizing HIGS 10⁸ gammas/s and its tight beam we will be able to characterize the system in the energy regime that it was designed for namely 4.44 MeV. HIGS offers the ability to tune the beam’s energy from 1-20 MeV by way of controlling the inverse Compton scattering off of a relativistic electron beam. With this feature characterization in a range of energies will be possible. Targets were made using a ray-tracing program that replicates a 12-micron ideal pinhole and a 20 cm long 300-micron gold penumbra aperture. The latter will require reconstruction of the coded images.

Our paper will describe a recently designed Mk x Nk x 10 um pixel CMOS gated imager intended to be first employed at the LLNL National Ignition Facility (NIF). Fabrication involves stitching MxN 1024x1024x10 um pixel blocks together into a monolithic imager (where M = 1, 2, . .10 and N = 1, 2, . . 10). The imager has been designed for either NMOS or PMOS pixel fabrication using a base 0.18 um/3.3V CMOS process. Details behind the design are discussed with emphasis on a custom global reset feature which erases the imager of unwanted charge in ~1 us during the fusion ignition process followed by an exposure to obtain useful data. Performance data generated by prototype imagers designed similar to the Mk x Nk sensor is presented.

The requirement from large scale facilities for high repetition rate operations is rapidly approaching, and is increasingly important for studies into high intensity secondary source generation, QED studies and the push for inertial confinement fusion. It is envisioned that multiple PW systems at high repetition rates will be built for projects such as the European Extreme Light Infrastructure project. Depending on the interaction physics involved, a number of differing parameters in the interaction increase in importance, including positioning accuracy and target surface quality, and to ensure reproducible optimum interaction conditions, presents a significant problem for accurate target positioning. With these requirements in mind, a co-ordinated project is underway at the Central Laser Facility amongst the experimental science, engineering and target fabrication groups, to tackle some of the challenges that we as a community face in working towards high repetition rate operations. Here we present the latest work being undertaken at the CLF to improve capability in key areas of this project, specifically in the areas of reliable motion control and rapid target positioning.

We report on the first observation of tertiary reaction-in-flight (RIF) neutrons produced in compressed deuterium and tritium filled capsules using the National Ignition Facility at Lawrence Livermore National Laboratory, Livermore, CA. RIF neutrons are produced by third-order, out of equilibrium (“in-flight”) fusion reactions, initiated by primary fusion products. The rate of RIF reactions is dependent upon the range of the elastically scattered fuel ions and therefore a diagnostic of Coulomb physics within the plasma. At plasma temperatures of ∼5 keV, the presence of neutrons with kinetic energies greater than 15 MeV is a unique signature for RIF neutron production. The reaction ¹⁶⁹Tm(n,3n)¹⁶⁷Tm has a threshold of 15.0 MeV, and a unique decay scheme making it a suitable diagnostic for observing RIF neutrons. RIF neutron production is quantified by the ratio of ¹⁶⁷Tm/¹⁶⁸Tm observed in a ¹⁶⁹Tm foil, where the reaction ¹⁶⁹Tm(n,2n)¹⁶⁸Tm samples the primary neutron fluence. Averaged over 4 implosions1^–4 at the NIF, the ¹⁶⁷Tm/¹⁶⁸Tm ratio is measured to be 1.5 ± 0.3 x 10⁻⁵, leading to an average ratio of RIF to primary neutron ratio of 1.0 ± 0.2 x 10⁻⁴. These ratios are consistent with the predictions for charged particle stopping in a quantum degenerate plasma.

This paper describes the engineering architecture and function of the neutron Time-of-Flight (nToF) diagnostic suite installed on the National Ignition Facility (NIF) at Lawrence Livermore National Laboratory (LLNL). These instruments provide key measures of neutron yield, ion temperature, drift velocity, neutron bang-time, and neutron downscatter ratio. Currently, there are five nToFs on three collimated lines-of-site (LOS) from 18m to 27m from Target Chamber Center, and three positioned 4.5m from TCC, within the NIF Target Chamber but outside the vacuum and confinement boundary by use of re-entrant wells on three other LOS. NIF nToFs measure the time history and equivalent energy spectrum of reaction generated neutrons from a NIF experiment. Neutrons are transduced to electrical signals, which are then carried either by coaxial or Mach-Zehnder transmission systems that feed divider assemblies and fiducially timed digitizing oscilloscopes outside the NIF Target Bay (TB) radiation shield wall. One method of transduction employs a two-stage process wherein a neutron is converted to scintillation photons in hydrogen doped plastic (20x40mm) or bibenzyl crystals (280x1050mm), which are subsequently converted to an electrical signal via a photomultiplier tube or a photo-diode. An alternative approach uses a single-stage conversion of neutrons-to-electrons by use of a thin (0.25 to 2 mm) Chemical Vapor Deposition Diamond (CVDD) disc (2 to 24mm radius) under high voltage bias. In comparison to the scintillator method, CVDDs have fast rise and decay times (<ns), have very low residual tails, are insensitive to shot gammas, and are less sensitive to the neutron signal of interest.

The Kirkpatrick Baez Optic (KBO) diagnostic designed for the National Ignition Facility (NIF) requires very precise alignment between four pairs of mirrors that make up four x-ray imaging channels. Furthermore, the overlapping image axis of the four pairs must be aligned to within a 50 μm radius of the NIF target center. In order to achieve this the diagnostic utilizes a telescoping snout that when extended, locates the mirrors at the end of a Diagnostic Load Package (DLP), cantilevered more than three meters out from its bolted connection points. Discussed in this paper are the structural challenges and the mechanical design solutions that were implemented to achieve the ±50 μm pointing accuracy. During an Inertial Confinement Fusion (ICF) experiment, the KBO diagnostic will be 117 mm away from the extremely high impulse, target implosion shock wave, which requires a unique approach to protecting the sensitive optics which will also be discussed.

As neutron yields increase at the National Ignition Facility (NIF) the need for neutron ‘hardened’ diagnostics has also increased. Gated Imagers located within the target chamber are exposed to neutrons which degrade image quality and damage electronics. In an effort to maintain the signal to noise ratio (S/N) on our images and mitigate neutron induced damage, we have implemented numerous upgrades to our X-ray framing cameras. The NIF Gated X-ray Detector (GXD), design has evolved into the Hardened Gated X-ray Detector, HGXD. These improvements are presented with image data taken on high yield NIF shots showing enhanced image quality. Additional upgrades were added to remotely locate sensitive electronics and ease operational use.

We present lessons learned from the fielding of various Mach-Zehnder (MZ) based diagnostic systems on the National Ignition Facility (NIF) and potential solutions. The DANTE X-ray diagnostic is the next in a series of applications for Mach-Zehnder based signal transport and acquisition systems on NIF and as such will incorporate many of these upgrades. In addition to extended dynamic-range performance and improved reliability, the upgrades presented also enable multiplexing of the signals from DANTE’s 18 X-Ray Diodes (XRD) to economize on system cost and rack space. Previous deployments on other NIF diagnostics highlighted the necessity to decouple the input light intensity from the bias point of the Mach-Zehnder. Areas of concern including polarization, temperature, bias point and optical power level control will be addressed.

The National Ignition Facility (NIF) at Lawrence Livermore National Laboratory uses the world’s largest and most energetic laser system to explore Inertial Confinement Fusion (ICF) and High-Energy-Density (HED) physics, with the potential of creating pressure and density conditions normally found in the cores of stars or large planets. During NIF experiments, the laser energy is directed to the target, driving the desired physics conditions, and the breakup of the target. During this breakup there is the potential to generate debris fields with both vaporized and solid target material, traveling at extremely high velocities (~10 km/s). For future shots, it is desirable to minimize distribution of the certain target materials within NIF. The High Energy Imaging Diagnostic (HEIDI), which comes within 8 cm of the target, will be modified to minimize the distribution of the ejected material. An external cone will be added to HEIDI which will block a larger angle than the existing hardware. Internal shielding will be added to isolate target material within the front portion of the diagnostic. A thin aluminum bumper will slow low-density vaporized material and contribute to the breakup of high velocity particles, while a thicker wall will block solid chunks. After the shot, an external cover will be installed, to contain any stray material that might be disturbed by regular operations. The target material will be retrieved from the various shielding mechanisms and assayed.

X-ray streak cameras are used at the National Ignition Facility for time-resolved measurements of inertial confinement fusion metrics such as capsule implosion velocity, self-emission burn width, and x-ray bang time (time of brightest x-ray emission). Recently a design effort was undertaken to improve the performance and operation of the streak camera photocathode and related assemblies. The performance improvements include a new optical design for the input of UV timing fiducial pulses that increases collection efficiency of electrons off the photocathode, repeatability and precision of the photocathode pack assembly, and increase the input field of view for upcoming experiments. The operational improvements will provide the ability to replace photocathode packs between experiments in the field without removing the diagnostic from the Diagnostic Instrument Manipulator (DIM). The new design and preliminary results are presented.

A Kirkpatrick-Baez (KB) x-ray microscope has been developed for the diagnostics of inertial confinement fusion (ICF). The KB microscope system works around 2.5keV with the magnification of 20. It consists of two spherical multilayer mirrors. The grazing angle is 3.575° at 2.5keV. The influence of the slope error of optical components and the alignment errors is simulated by SHADOW software. The mechanical structure which can perform fine tuning is designed. Experiment result with Manson x-ray source shows that the spatial resolution of the system is about 3-4μm over a field of view of 200μm.