Bochum 1998 – wissenschaftliches Programm
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HK: Hadronen und Kerne
HK 56: Postersitzung
HK 56.59: Poster
Mittwoch, 18. März 1998, 17:00–19:00, Foyer
Optical and radiation resistance properties of PbF2 crystals* — •Patrick Achenbach — Universität Mainz
The A4 collaboration at the Mainz microtron MAMI is preparing a measurement of the parity violating asymmetry in elastic electron-proton scattering. The electromagnetic calorimeter comprising 1022 lead fluoride crystals will experience a dose of 0.1 kGy during the experiment. Therefore the radiation resistance of this material is a main subject of interest. First of all this talk will deal with the optical properties of large size crystals concerning their applicability as detection material. Optical transmittance curves, which mainly determine the energy resolution of Čerenkov radiators, will be presented for crystals of three different international manufacturers. The crystals’ radiation resistance with regard to absorbed energy doses between 0.1 and 7 kGy of 60Co γ-radiation will be discussed. In addition to the observed small spontaneous recovery of the damages illuminations have been performed which has led to an almost complete restoration of the original characteristics. This so-called optical bleaching will be presented thoroughly in the talk. A concept to implement such a procedure in the planned A4 calorimeter by transferring the light through optical fibres will be introduced. Finally, measurements with high energetic electrons will be presented which extend the knowledge about the radiation induced changes in lead fluoride.
* supported by the DFG in the Sonderforschungsbereich 201