Optimisation des parametres de scintillation des cristaux de tungstate de plomb pour leur application dans la calorimetrie electromagnetique de haute precision

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OPTIMISATION DES PARAMETRES DE SCINTILLATION DES CRISTAUX DE TUNGSTATE DE PLOMB POUR LEUR APPLICATION DANS LA CALORIMETRIE ELECTROMAGNETIQUE DE HAUTE PRECISION

CHAMBERY -BU Bourget (730512101) / SudocSudocFranceF

Measurement of Light Collection of CMS PbWO4 Crystals: Comparison with the Cristal Monte Carlo Simulation Program and Further Evaluation

The measurement of the signal for light collection limited by the effective area of the present APD detectors has been evaluated using a photomultiplier and co60 source. Comparison of the methods and experimental results for simple geometrical situations has been made with the results of the CRISTAL Monte Carlo program which is also used to evaluate more complicated geometries including evaluation of a wavelength shifter used with an APD as a photodetector

Studies and Proposals for an Automatic Crystal Control System

This document presents the status of the studies for an Automatic Crystal Control System ( ACCOS) performed since autumn 1995 for the CMS collaboration. Evaluation of a startstop method for light yield, light uniformity and decay time measurements of PbWO4 crystals is presented, as well as the first results obtained with a compact double-beam spectrophotometer for transverse transmission. Various overall schemes are proposed for an integrated set-up including crystal dimension measurement. The initial financial evaluationperformed is also given

Results of PWO Radiation Hardness Optimization.

The results of analysis of the PWO radiation hardness depending of crystal growth technology are presented. The PWO crystals of different crystallization numbers with one kind of doping and double doped as well as crystals grown from recycled raw materials were analyzed. The presented results show high level of crystal technology reproducibility. More than 95% of double doped crystals satisfy to the CMS ECAL specification requirements

Systematic Study of the PbWO4 Crystal Short Term Instalibity Under Irradiation

The effect of the irradiation on the lead tungstate ( PWO) scintillator properties has been studied at different irradiation facilities. Lead tungstate crystals grown with the tuning of oxides content in the melt to the stoichiometry of pure sheelite or sheelite-like type crystals and doped with heterovalent, trivalent and pentavalent impurities have been studied in order to optimize their resistance to irradiation. A combination of a selective cleaning of raw materials, a tuning of the melt from crystallization to crystallisation, and a destruction or compensation of the point structure defects has been used to minimize the short-term instability of PWO parameters under irradiation