Response of CR-39 to Heat Exposure

As a nuclear track detector, CR-39 (polyallyl diglycol carbonate) is used to reveal the products of fusion reactions. Positioned around the OMEGA target chamber, pieces of CR-39 absorb and are damaged by ejected particles. The plastic is then etched in NaOH solution at 80°C for 6 hours, resulting in the formation of nuclear tracks visible under a digital microscope. The etching process also reveals background noise, speculated in part to be the result of exposure to heat during shipment between suppliers and laboratories. To determine the effects of heat exposure on data analysis, pieces of CR-39 were exposed to high temperatures for various times. Heated pieces were then exposed to protons of known energies using the particle accelerator at SUNY Geneseo. Each exposed piece was etched and compared to a control. Pieces were found to oscillate between a visibly cloudy and clear appearance as a function of time exposed to high temperatures. This property was measured and quantified via reflectance and transmission of light. Furthermore, it was observed that exposure to temperatures above 100°C resulted in inaccurate data collection as etch rate and therefore track size were affected. This combination of results is an indication that current tests of the purity of CR-39 before use on OMEGA may not be sufficient.