0DUFK   CMS Week, CERN Yttrium Doped Lead Tungstate CrystalsRen-yuan ZhuCalifornia Institute of Technology0DUFK   CMS Week, Ren-yuan ZhuOutline Segregation coefficient of the yttrium in PbWO4crystal. Performance of the yttrium doped PbWO4crystals. The transmittance and the birefringence.0DUFK   CMS Week, Ren-yuan Zhu The Glow Discharge Mass Spectroscopy (GDMS) was used to determine yttrium concentration in crystals. A fit to the GDMS data extracts the yttrium segregation coefficient kein PbWO4. Ke= 0.91 ± 0.04Yttrium Segregation Coefficient0DUFK   CMS Week, Ren-yuan ZhuProperties of Yttrium Doped PWO Crystals UV-excited photo luminescence and γ–excited radio luminescence. Decay kinetics. Radiation damage. Light response uniformity. Radiation Induced Color centers.  Published in NIM A480 (2002), 468.0DUFK   CMS Week, Ren-yuan ZhuSet-up for Luminescence MeasurementPhoto-LuminescenceRadio-Luminescence• Surface excited by UV• No Internal absorption• Whole body excited by γ-ray• With internal absorption0DUFK   CMS Week, Ren-yuan Zhu 15-20 nm red shift of the peak of the radio luminescence to that of the photo luminescence. The shift is explained by internal absorption.Photo and Radio Luminescence0DUFK   CMS Week, Ren-yuan ZhuLuminescence before and after IrradiationsBoth excitation and emission spectra are not affected by the γ-ray irradiation0DUFK   CMS Week, Ren-yuan ZhuDecay Kinetics>85 and 95% of light in 50 and 100 ns0DUFK   CMS Week, Ren-yuan ZhuRadiation Damage5-15% and 15-30% light output loss under 15 and 500 rad/h0DUFK   CMS Week, Ren-yuan ZhuSummary of Light Output Measurements---57.373.593.594.785.073.010.8SIC-679BGRI-82697.786.680.283.691.398.297.392.056.88.4SIC-S392ID------63.676.183.959.58.8BTCP-5658---------77.498.586.848.67.2BTCP-5618---------82.998.548.67.2BTCP-561568.270.376.886.197.989.862.89.3BTCP-216270.572.378.689.297.889.955.48.2BTCP-2133---62.274.786.096.784.475.711.2---69.978.789.095.583.577.011.4BGRI-824---59.676.094.293.585.270.310.4SIC-678------79.391.798.488.370.310.4SIC-606---81.484.291.594.285.671.610.6SIC-S762------79.888.398.988.860.18.9SIC-S64385.385.991.298.298.694.656.18.3SIC-S41278.082.188.695.197.891.366.99.9SIC-S34774.379.587.396.696.692.063.59.4SIC-S301100050010015100ns/1Ps50ns/1PsJp.e.LO (%) at R (rad/h)Fraction (%)LO (1/MeV)Sample0DUFK   CMS Week, Ren-yuan ZhuLight Response Uniformity)1/(1 −+=midmidxxyyδThe response (y) along the axis was fit to a linear function:0DUFK   CMS Week, Ren-yuan ZhuColor Center Density Radiation induced color center density, or absorption coefficient:beforemequilibriuLALLALD11−=LAL:light attenuation length0DUFK   CMS Week, Ren-yuan ZhuColor Center DecompositionC1: 3.07 eV (400 nm) / 0.76 eV, C2: 2.30 eV (540 nm) / 0.19 eV0DUFK   CMS Week, Ren-yuan ZhuLongitudinal TransmittanceTransmittance approaches theoretical limit: low intrinsic absorptionC axis limitA axis limit0DUFK   CMS Week, Ren-yuan ZhuTransmittance and BirefringenceCzochralski: grown along the a axis Bridgman: grown along the c axis0DUFK   CMS Week, Ren-yuan ZhuPWO Crystals Grown along c AxisPWO crystals grown along the c axis are isotropic transversely0DUFK   CMS Week, Ren-yuan ZhuPWO Crystals Grown along c Axis (cont.)Good longitudinal uniformity in the transverse transmittance0DUFK   CMS Week, Ren-yuan ZhuPWO Crystals Grown along a AxisSome longitudinal non-uniformity in the transverse transmittance.0DUFK   CMS Week, CERN SummaryThe concentration of yttrium ions in PbWO4crystals is rather uniform, the segregation coefficient is 0.91±0.04.The scintillation light of yttrium doped PbWO4crystals has a broad distribution with a peak at 420 nm, the luminescence spectra and longitudinal light response uniformity are not affected by the J – ray irradiations.Yttrium doping is effective in reducing slow scintillation component, the ratio between light outputs integrated in 100 and 1000 ns is about 95%.The yttrium doped PbWO4crystals have adequate radiation hardness for the barrel ECAL, but may fall short for the end caps.0DUFK   CMS Week, CERN Summary (Cont.) The radiation induced absorption in all yttrium doped samples can be decomposed to two common color centers peaked at 400 nm (3.07 eV) and 540 nm (2.30 eV) with widths of 0.76 eV and 0.19 eV respectively. Because of the birefringence PWO crystals grown along the c axis is isotropic transversely, while crystals grown along the a axis are optically not isotropic transversely. Also because of the birefringence PWO crystals grown along the c axis have lower theoretical limit in longitudinal transmittance, which is significant in the short wavelength