Image plates (IPs) are a reusable recording media capable of detecting ionizing radiation, used to diagnose x-ray emission from laser-plasma experiments. Due to their superior performance characteristics in x-ray applications [C. C. Bradford, W. W. Peppler, and J. T. Dobbins III, Med. Phys. 26, 27 (1999) and J. Digit. Imaging. 12, 54 (1999)], the Fuji Biological Analysis System (BAS) IPs are fielded on x-ray diagnostics for the HELEN laser by the Plasma Physics Department at AWE. The sensitivities of the Fuji BAS IPs have been absolutely calibrated for absolute measurements of x-ray intensity in the energy range of 0-100 keV. In addition, the Fuji BAS IP fading as a function of time was investigated. We report on the characterization of three Fuji BAS IP responses to x-rays using a radioactive source, and discrete x-ray line energies generated by the Excalibur soft x-ray facility and the Defense Radiological Standards Centre filter-fluorescer hard x-ray system at AWE.

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The Henway spectrometer! was developed by Koppel and Eckels at Lawrence Livemore National Laboratory, and this was followed by the later development of the HENEX spectrometer for studies of laser-plasma interactions at OMEGA (Laboratory for Laser Energetics) and the National Ignition Facility.The design of these previous x-ray spectrometers has been analysed in order to produce a four-channel high-energy x-ray spectrometer (HEX-ID) with superior resolution. The shielding has been adapted for use on short-pulse laser-plasma experiments. HEX-ID is intended for: verification of backlighter materials; identification of plasma ion species and their charged states; and measurement of plasma opacity and absolute conversion efficiency of characteristic x-ray line emissions. The spectrometer will be fielded at the new Orion laser facility at AWE (UK) and on OMEGA.The minimum theoretical resolving power E/8E of HEX-ID ("" 640) has been improved upon that of HENEX ("" 500). The enhancement in resolving power has been achieved by reducing the crystal radius-of-curvature and allowing up to 30 mm variation in the crystal-to-detector distance, which can be adjusted manually before TIM-based deployment. A convex reflection crystal in each of the four channels provides a total spectral range of 1-10 keY in overlapping bands. In order to achieve a desired spatial and temporal resolution, adapt the spectrometer dynamic range to long-pulse and short-pulse laser shots, as well as for cross-channel comparison of the energy dispersion and spectral range, HEX-ID can utilize a number of detectors including image plate and CCD.

A pulse-dilation photomultiplier tube (PD-PMT) with sub-20 ps temporal resolution has been developed for use with γ-ray-sensitive gas Cherenkov detectors at the National Ignition Facility to improve the diagnosis of nuclear fusion burn history and the areal density of the remaining capsule ablator. The pulse-dilation mechanism entails the application of a time-dependent, ramp waveform to a photocathode-mesh structure, introducing a time-dependent photoelectron accelerating potential. The electric field imparts axial velocity dispersion to outgoing photoelectrons. The photoelectron pulse is dilated as it transits a drift region prior to amplification in a microchannel plate and read out with a digital oscilloscope. We report the first measurements with the prototype PD-PMT demonstrating nominal <20 ps FWHM across a 400 ps measurement window and <30 ps FWHM for an extracted charge up to 300 pC. The output peak areas are linear to within 20% over 3 orders of magnitude of input intensity. 3D particle in cell simulations, which included space charge effects, have been carried out to investigate the device temporal magnification, resolution, and linearity.

The Cherenkov mechanism used in Gas Cherenkov Detectors (GCDs) is exceptionally fast. However, the temporal resolution of GCDs, such as the Gamma Reaction History diagnostic at the National Ignition Facility (NIF), has been limited by the current state-of-the-art photomultiplier tube technology to ∼100 ps. The soon-to-be deployed Pulse Dilation Photomultiplier Tube (PD-PMT) at NIF will allow for temporal resolution comparable to that of the gas cell or ∼10 ps. Enhanced resolution will contribute to the quest for ignition in a crucial way through precision measurements of reaction history and ablator areal density (ρR) history, leading to better constrained models. Features such as onset of alpha heating, shock reverberations, and burn truncation due to dynamically evolving failure modes may become visible for the first time. Test measurements of the PD-PMT at Atomic Weapons Establishment confirmed that design goals have been met. The PD-PMT provides dilation factors of 2 to 40× in 6 increments. The GCD-3 recently deployed at the NIF has been modified for coupling to a PD-PMT and will soon be making ultrafast measurements.