Studies of the Light Output and Oxygen Penetration Depth of Plastic Scintillators during Irradiation*

Results are presented on the decrease of light output for plastic scintillator during irradiation by a Cobalt-60 source at a dose rate of 1.3 Gy/hr and at temperatures of -30, -15, 0, and 10 degrees, wrapped in Tyvek and unwrapped, in standard atmosphere. At -30 degrees C with ESR wrapping, measurements were also made in a 97% nitrogen, 3% oxygen atmosphere and in standard atmosphere. Substantial damage was seen during the -30 degree irradiation with ESR wrapping that annealed quickly when the sample was warmed after the end of irradiation. The damage was less at warmer temperatures. The damage was largest with ESR wrapping and smallest with no wrapping. Damage with 3% oxygen was similar to that in standard atmosphere. Evidence of a plateau in the radical density was seen for the 0 and 10 degree C data. This is the first measurement of damage during irradiation at cold temperatures.