Development of radiation stable plastic scintillator. Final technical report, July 1991--July 1993

The Detector Development Group at the University of Florida has identified the only known optically radiation hard polymer, scintillator and wavelength shifter materials. The authors summarize their findings here. They conducted an extensive study of siloxane polymers using monomers of dimethyl, diphenyl and methylphenyl siloxanes. An important finding of that study was that polymethylphenylsiloxane is a candidate polymer for use at the SSC. However, the most important result of that work was the demonstration of the existence of optical polymers with extreme resistance to radiation damage. It held out the promise that other possibly more convenient polymers with similar properties could be identified. The first high viscosity, transparent, radiation hard siloxane with high fluor solubility was processed into prototype plates. The authors propose a mechanism to account for radiation induced annealable color center formation in commercial scintillator polymers such as PS and PMMA. The authors produced analogues of these polymers with T{sub g} < room temperatures. These polymers are optically radiation hard. The University of Florida has applied for a patent on this breakthrough discovery. It was found that dye mobility for radiation hard elastomers (T{sub g} < room temperature) was unacceptable over a period of one year. Dyes would tend to crystallize on the surface of the plates. The work concentrated therefore on thermoplastic polymers which had T{sub g} {approximately} 50 C (i.e., high enough for structural stability) and with high color center annealing rate such as polyisobutylmethacrylate. These polymers were both radiation hard and had minimal dye migration. The University of Florida has a patent on these materials. These materials were extruded and tested for stability and found adequate for operation up to 10 Mrad at the SSC