N. S. P. King

Charged Particle Radiography

New applications of charged particle radiography have been developed over the past two decades that extend the range of radiographic techniques providing high-speed sequences of radiographs of thicker objects with higher effective dose than can be obtained with conventional radiographic techniques. In this paper, we review the motivation and the development of flash radiography and in particular, charged particle radiography.

A Survey of High Explosive‐Induced Damage and Spall in Selected Metals Using Proton Radiography

Multiple spall and damage layers can be created in metal when the free surface reflects a Taylor wave generated by high explosives. These phenomena have been explored in different thicknesses of several metals (tantalum, copper, 6061 T6‐aluminum, and tin) using high‐energy proton radiography. Multiple images (up to 21) can be produced of the dynamic evolution of damaged material on the microsecond time scale with a <50 ns “shutter” time. Movies and multiframe still images of areal and (Abel inverted) volume densities are presented. An example of material that is likely melted on release (tin) is also presented.

Total cross sections for the production of 22Na and 24Na in proton-induced reactions on 27Al from 0.40 to 22.4 GeV

Total cross sections for production of 22 Na and 24 Na from the irradiation of 27 Al by protons with incident energies between 0.40 and 22.4 GeV have been measured. The overall uncertainties for these measurements were less than 3%. The measured values compare well with previous measurements and evaluations. � 2003 Elsevier B.V. All rights reserved.

Proton Radiography Examination of Unburned Regions in PBX 9502 Corner Turning Experiments

PBX 9502 Corner Turning Experiments have been used with various diagnostics techniques to study detonation wave propagation and the boosting of the insensitive explosive. In this work, the uninitiated region of the corner turning experiment is examined using Proton Radiography. Seven transmission radiographs obtained on the same experiment are used to map out the undetonated regions on each of three different experiments. The results show regions of high‐density material, a few percent larger than initial explosive density. These regions persist at nearly this density while surrounding material, which has reacted, is released as expected. Calculations using Detonation Shock Dynamics are used to examine the situations that lead to the undetonated regions.

Time-resolved spectral measurements for the Boeing free-electron laser experiments

Abstract A time-resolved optical spectrometer based on the integration of a Jarrell-Ash monochromator and a Hamamatsu streak camera has been used to evaluate the Boeing burst-mode oscillator experiment. The system provides information about spectral evolution on both the micropulse (10 ps) and macropulse (50–100 μs) time scales. Besides measuring the micropulse duration, a wavelength shift within a micropulse and the development of a discrete second wavelength during a macropulse are reported and discussed.

Proton Radiography Experiments on Shocked High Explosive Products

We studied the propagation of detonation waves and reflections of normal incident detonation waves in explosive products using the 800 MeV proton radiography facility at LANSCE. Using this system, we obtain seven to twenty‐one radiographic images of each experiment. We have examined the experimental wave velocity and density of the materials ahead and behind of the shocks as inferred from radiographs and compare them to standard explosive equations of state. Finally we compare the experiments with calculations of the experiments using the MESA hydrodynamics code.

Determination of the absolute efficiency of an organic scintillator for neutrons with energies between 0.5 and 800 MeV

Abstract We have determined the absolute efficiency of an NE-213 scintillator for neutrons with energies from 0.5 to 800 MeV. The detector was 5.1 cm in diameter and 2.5 cm deep. The efficiencies were obtained for detector thresholds of 0.011, 0.48, 1.12, and 4.48 MeVee. Our results are compared to predictions of the STANTON computer code.

Longitudinal linac beam focusing for neutron time-of-flight measurements

Abstract A method is described in which 805 MHz acceleration cavities in the LAMPF linac are used to form a nearly isochronous beam of particles for use in high-resolution neutron time-of-flight spectroscopy at energies less than 800 MeV.

Design, construction, alignment, and calibration of a compact velocimetry experiment

A velocimetry experiment has been designed to measure shock properties for small cylindrical metal targets (8-mm-diameter by 2-mm thick). A target is accelerated by high explosives, caught, and retrieved for later inspection. The target is expected to move at a velocity of 0.1 to 3 km/sec. The complete experiment canister is approximately 105 mm in diameter and 380 mm long. Optical velocimetry diagnostics include the Velocity Interferometer System for Any Reflector (VISAR) and Photon Doppler Velocimetry (PDV). The packaging of the velocity diagnostics is not allowed to interfere with the catchment or an X-ray imaging diagnostic. A single optical relay, using commercial lenses, collects Doppler-shifted light for both VISAR and PDV. The use of fiber optics allows measurement of point velocities on the target surface during accelerations occurring over 15 mm of travel. The VISAR operates at 532 nm and has separate illumination fibers requiring alignment. The PDV diagnostic operates at 1550 nm, but is aligned and focused at 670 nm. The VISAR and PDV diagnostics are complementary measurements and they image spots in close proximity on the target surface. Because the optical relay uses commercial glass, the axial positions of the optical fibers for PDV and VISAR are offset to compensate for chromatic aberrations. The optomechanical design requires careful attention to fiber management, mechanical assembly and disassembly, positioning of the foam catchment, and X-ray diagnostic field-of-view. Calibration and alignment data are archived at each stage of the assembly sequence.

Two-Dimensional Time-Dependent Imaging Utilizing Tomographic Concepts

Tomography is the process of obtaining two-dimensional spatial distributions (images) from one-dimensional externally derived profiles or projections. This chapter is not intended as a general review of this broad, far reaching field, but will focus on tomographic solutions to imaging problems utilizing recent developments in electro-optics and fiber optics. Some of the imaging experiments considered here are complicated by hostile environments which require transferring the data over distances of 10 meters or more to protect the recording equipment. It is also often a requirement that complete information be obtained in a single, non-repetitive experiment. These complications on the application of tomographic techniques necessitate the use of high speed photonic solutions involving fiber optic arrays combined with high speed detectors.