John David Zumbro

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.

Proton radiography as a means of material characterization

We describe how protons with energies of 800 MeV or greater can be used as radiographic probes for material characterization. A feature which distinguishes protons from x-rays is their charge, which results in multiple Coulomb scattering effects in proton radiographs. Magnetic lensing can ameliorate these effects and even allow mixed substances to be disentangled. We illustrate some of these effects using 800 MeV protons radiographs of a composite step wedge composed of Aluminum, Foam, and Graphite. We discuss how proton radiographs must be manipulated in order to use standard tomographic reconstruction algorithms. We conclude with a brief description of an upcoming experiment, which will be performed at Brookhaven National Laboratory at 25 GeV.

Intensified/shuttered cooled CCD camera for dynamic proton radiography

An intensified/shuttered cooled PC-based CCD camera system was designed and successfully fielded on proton radiography experiments at the Los Alamos National Laboratory ALNSCE facility using 800-MeV protons. The four camera detector system used front-illuminated full-frame CCD arrays fiber optically coupled to either 25-mm diameter planar diode or microchannel plate image intensifiers which provided optical shuttering for time resolved imaging of shock propagation in high explosives. The intensifiers also provided wavelength shifting and optical gain. Typical sequences consisting of four images corresponding to consecutive exposures of about 500 ns duration for 40-ns proton burst images separated by approximately 1 microsecond were taken during the radiography experiments. Camera design goals and measured performance characteristics including resolution, dynamic range, responsivity, system detection quantum efficiency, and signal-to-noise will be discussed.

Integrating image detector for high-energy neutrons

We describe an integrating cathode-pad read-out wire chamber for imaging high energy neutrons. This technology allows construction of a detector with a wide dynamic range, which is gatable, easily read out, and provides millimeter scale resolution. Results from a prototype 48 by 48 pixel array are presented.

High-energy neutron radiography

High-energy spallation neutron sources are now being considered in the US and elsewhere as a replacement for neutron beams produced by reactors. High-energy and high intensity neutron beams, produced by unmoderated spallation sources, open potential new vistas of neutron radiography. We discuss the basic advantages and disadvantages of high- energy neutron radiography, and consider some experimental results obtained at the Weapons Neutron Research facility at Los Alamos.