Particle Beam Radiography

Abstract

Particle beam radiography, which uses a variety of particle probes (neutrons, protons, electrons, gammas and potentially other particles) to study the structure of materials and objects noninvasively, is reviewed, largely from an accelerator perspective, although the use of cosmic rays (mainly muons but potentially also high-energy neutrinos) is briefly reviewed. Tomography is a form of radiography which uses multiple views to reconstruct a three-dimensional density map of an object. There is a very wide range of applications of radiography and tomography, from medicine to engineering and security, and advances in instrumentation, specifically the development of electronic detectors, allow rapid analysis of the resultant radiographs. Flash radiography is a diagnostic technique for large high-explosive-driven hydrodynamic experiments that is used at many laboratories. The bremsstrahlung radiation pulse from an intense relativistic electron beam incident onto a high-Z target is the source of these radiographs. The challenge is to provide radiation sources intense enough to penetrate hundreds of g/cm 2 of material, in pulses short enough to stop the motion of high-speed hydrodynamic shocks, and with source spots small enough to resolve fine details. The challenge has been met with a wide variety of accelerator technologies, including pulsed-power-driven diodes, air-core pulsed betatrons and high-current linear induction accelerators. Accelerator technology has also evolved to accommodate the experimenters' continuing quest for multiple images in time and space. Linear induction accelerators have had a major role in these advances, especially in providing multiple-time radiographs of the largest hydrodynamic experiments.

Beam Breakup in an Advanced Linear Induction Accelerator

“…T WO linear induction accelerators (LIAs) have been in operation at the Dual Axis Radiographic Hydrodynamic Test (DARHT) facility at the Los Alamos National Laboratory [1], [2], and now, a new multipulse LIA is being designed. For the new accelerator, the ferrite cores of DARHT-I will be replaced with enough Metglas to provide a four-pulse operation.…”

Observation of the Dynamics of a Focal Spot Using a Long-Pulse Linear Induction Accelerator

“…L INEAR induction accelerators (LIAs) of electrons have found applications in applied problems [1] and fundamental research for the production of warm dense matter [2]. In these applications, a strong focusing of the beam on the target surface is required.…”

Beam breakup in a solid-state powered linear induction accelerator

“…The Scorpius beam injector will produce four 2-kA, 2-MeV pulses, which will be accelerated by the LIA to 20-MeV. These electron pulses will then be focused onto a bremsstrahlung radiation converter for point-projection imaging of the experiment [2]. The radiation pulse-lengths will be less than 60-ns FWHM, which is sufficient to provide stop-action radiographs of the experiment at four discrete times.…”