2012 DPP Meeting
DPP 2012 Meeting Abstracts
UV Enhancement of Etch Parameters of Nuclear Tracks in CR39
Graham Jensen, Dante Tufano, Gregory Marks, Joseph Mifsud, Mark Teets, James McLean; SUNY Geneseo
Michelle Burke, Craig Sangster; Laboratory for Laser Energetics
The use of CR-39 plastic as a nuclear particle track detector is an effective technique for recovering data in high energy particle experiments including inertial confinement nuclear fusion. To analyze particle track data after irradiation, CR-39 is chemically etched at elevated temperatures with Sodium Hydroxide, producing measurable pits at the nuclear track sites. When CR-39 is exposed to ultraviolet light between nuclear irradiation and chemical etch an increase in pit diameter by a factor of as much as 1.7 occurs, due to an enhancement in the track etch rate relative to the bulk etch rate. We have focused specific attention on pinpointing the critical wavelengths which produce this effect: UV below approximately 320nm is effective, and work is proceeding to determine whether the effect ceases at a shorter wavelength. A detailed analysis of how this effect depends on the intensity and duration of ultraviolet exposure is underway. Initial results suggest that this is not simply proportional to UV energy absorbed.
*Funded in part by a grant from the DOE through the Laboratory for Laser Energetics
X-ray Enhancement of Etch Parameters of Nuclear Tracks in CR39
Michael Giordano, Krystalyn Sadwick, Kurt Fletcher; SUNY Geneseo
Michelle Burke, Craig Sangster; Laboratory for Laser Energetics
The nuclear track detector CR-39 is a polymer used to measure charged particles produced in inertial confinement fusion experiments. Alpha particles stopping in CR-39 produce nanometer-scale damage sites. When the CR-39 is etched in 6-N sodium hydroxide at 80? C for six hours, the difference in etch rates between the damage sites and the bulk material results in the formation of pits 20 to 25 microns in diameter. These can be characterized and counted using optical microscopy. A modest increase in the pit diameter is observed when the CR-39 detector is irradiated by x-rays from a tungsten cathode after exposure to charged particles and before etching. This enhancement of the diameter increases as the total x-ray dose increases, with enhancements of about 1.10 for 1000 Gy doses. Controlled experiments show that the effect is due to the x-ray dose rather than a difference in the handling or the environment. The ratio of the track-etch rate to bulk-etch rate seems to be independent of x-ray dose. The mechanism for this effect is currently under investigation. These results show that modest increases in pit diameters can be obtained through irradiation with x-rays.
*Funded in part by a grant from the DOE through the Laboratory for Laser Energetics
Simultaneous measurement of proton and electron energy spectra using a Thomson parabola ion spectrometer
K.R. Crompton, M.J. Schepis, J.P. Shortino, C.G. Freeman; SUNY Geneseo
G. Fiksel, C. Mileham, T.C. Sangster; Laboratory for Laser Energetics
Simultaneous measurements of the energy spectrum of protons and electrons accelerated from the rear side of thin targets illuminated with ultra-intense laser light have been carried out at the Multiterawatt (MTW) laser facility at the Laboratory for Laser Energetics. The particles enter a Thomson parabola ion spectrometer consisting of a permanent magnet and a pair of electrostatic deflector plates. A Fujifilm imaging plate mounted at the rear of the device was used to detect the protons. A thin tantalum foil was placed on top of the imaging plate to prevent all ions other than the protons from reaching the plate. Electrons, with a much smaller magnetic rigidity, are deflected strongly by the Thomson parabola permanent magnet and exit the magnet before entering the electrostatic deflector plates. Another imaging plate placed on top of the permanent magnet was used to detect these electrons. A computer program has been written to analyze the resulting data from the imaging plates. This enables the proton and electron energy spectrum to be determined simultaneously for a particular shot.
*Funded in part by a grant from the DOE through the Laboratory for Laser Energetics
Measurements of the sensitivity and spatial resolution of radiochromic film using ion beams and X-rays
M.J. Schepis, J.P. Shortino, K.R. Crompton, C.R. Stillman, C.G. Freeman; SUNY Geneseo
P.M. Nilson, C. Sorce, T.C. Sangster; Laboratory for Laser Energetics
Radiochromic film (RCF) is used to study protons and other ions that are accelerated from the rear side of targets illuminated with ultra-intense laser light. An experiment is underway to measure the sensitivity of RCF to protons and alpha particles of various energies using the 1.7 MV tandem Pelletron accelerator at SUNY Geneseo. An ion beam incident on a gold foil is used to expose the RCF to elastically scattered ions in a 28-inch diameter scattering chamber. The film is positioned in a circular arc in the chamber so the scattered ion fluence on the RCF strip varies as a function of the scattering angle. After exposure, the RCF is scanned in color negative transmission mode using an Epson 10000 XL flatbed scanner. The red channel of the resulting scan is used to determine the optical density of the film. The spatial resolution of the film was measured by blocking part of the film with a tantalum knife edge. The sensitivity of RCF to X-rays was also measured by exposing the film to X-rays produced by a biological irradiator. The response of the new Gafchromic HD-V2 radiochromic film is compared with the discontinued Gafchromic HD radiochromic film.
*Funded in part by a grant from the DOE through the Laboratory for Laser Energetics