COMPARISON OF nfl DAMAGE IN PLASTIC SCINTILLATORS.pdf

COMPARISON OF n/ DAMAGE IN PLASTICSCINTILLATORSU. HOLM, A. MEYER-LARSENI. Institut fur ExperimentalphysikUniversitat Hamburg22761 Hamburg, GermanyWe have irradiated polystyrene based scintillators SCSN38, SCSN81T2, pure poly-methylmetacrylateGS218, and wave-length shifterY7 in PMMA with a nearly purebeam of fast neutrons (mean energy 6 MeV) as well as with a 60Co source to about5 kGy (n) respectively 7 kGy ( ). The optical damage of SCSN38 (SCSN81T2) isa factor 5 (3) higher for neutron compared to irradiations. For PMMA materialsGS218, Y7 the neutron damage is smaller. Destruction of uors is, in both cases,smaller for neutron irradiation.1 Introduction VIIth International Conference on Calorimetry in High-Energy PhysicsTucson, November 1997 The radiation stability of plastic scintillators, wavelength shifters and lightguides for calorimeters in high energy physics detectors generally is investigatedby irradiations. But hadronic and electromagnetic showers produce a strong ux of fast neutrons in detectors, at LHC e.g. more than 1015n=cm2
yearare expected for the most aected regions. The energy distribution peaks atabout 1 MeV. The question arises whether the data can be taken over forn damaging simply by calculating the dose, released by ionizing secondaryparticles. It is known that in polymeric materials fast neutrons may causedierent damage compared to s with the same released dose. For this reason itis necessary to investigate the materials under question with fast neutrons. Wealready have performed neutron irradiations in reactors 13 with dominating background. This paper deals with an irradiation in a nearly pure beam offast neutrons.2 Experimental2.1 IrradiationsThe materials under investigation are the polystyrene (PS) based scintillatorsSCSN384, 2.6 mm thick, and SCSN81T25, 3mm thick, the wave-length shifter(WLS) Y7 4;3 with polymethylmetacrylate (PMMA) base and ultra-violet ab-sorber, 2 mm thick, and pure PMMA GS218 6, 5mm thick. All samples