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1 Optical and Scintillation Properties of Heavy Crystal Scintillators Rihua Mao, Liyuan Zhang and Ren-yuan Zhu California Institute of Technology November 2, 2007 N49-1. Rihua Mao, Caltech 1

2 Introduction This is a part of the work to improve the inorganic scintillator section in the particle data book (PDB). The crystal table in the PDB provides a comparison of light output measured by PMTs with a bi-alkali cathode for samples with undefined size and wrapping. To accommodate readout devices other than PMT with bi-alkali cathode, such as silicon photodiode (PD) and avalanche photodiode (APD), the quantum efficiencies (QE) of the PMT should be taken out. To reduce sample size and wrapping dependence samples should have defined dimension and wrapping. Properties investigated: UV excitation and emission spectra, optical transmittance, light output, decay kinetics and temperature coefficient. November 2, 2007 N49-1. Rihua Mao, Caltech 2

3 Inorganic Scintillators in the 2006 PDB Crystal NaI(Tl) CsI(Tl) CsI BaF 2 BGO PbWO 4 LSO(Ce) GSO(Ce) Density (g/cm 3 ) Melting Point (ºC) Radiation Length (cm) Molière Radius (cm) Interaction Length (cm) Refractive Index a Hygroscopicity Yes Slight Slight No No No No No Luminescence b (nm) (at peak) Decay Time b (ns) Light Yield b,c (%) d(ly)/dt b (%/ ºC) ~ ~ ~0-0.1 Experiment Crystal Ball CLEO BaBar BELLE BES III KTeV TAPS (L*) (GEM) L3 BELLE PANDA? CMS ALICE PANDA? (BTeV) - - a. at peak of emission; b. up/low row: slow/fast component; c. measured by PMT of bi-alkali cathode. November 2, 2007 N49-1. Rihua Mao, Caltech 3

Samples Sample size: All are cube of 1.5 X 0. NaI(Tl) is a cylinder of 1.5 X 0 long and 1.5 1.5 X 02 area at two ends to match 2 PMT.

4 Samples Sample size: All are cube of 1.5 X 0. NaI(Tl) is a cylinder of 1.5 X 0 long and X 02 area at two ends to match 2 PMT. Sample Wrapping: All are wrapped with Tyvek paper. Hygroscopic samples (NaI and CsI) are sealed in 3 mm thick quartz window. November 2, 2007 N49-1. Rihua Mao, Caltech 4

5 Excitation & Photo Luminescence Emission measured with θ = 10 o : No internal absorption UV lamp and monochromator Sample Orientation Excitation θ Monochromator and PMT Emission Sample Hitachi F-4500 November 2, 2007 N49-1. Rihua Mao, Caltech 5

6 Transmittance Measurement Perkin Elmer Lambda-950 spectrophotometer with double beam, double monochromator and GPOB Reference beam Sample beam Theoretical limit: R.Y. Zhu, NIM A333 (1993) 422 November 2, 2007 N49-1. Rihua Mao, Caltech 6

7 LSO/LYSO Refractive Index Wavelength dependent measurement by a V-prism Cubic sample placed inside a V-prism Incident light shooting perpendicularly to one side of the prism Refractive Index: n The refractive index is calculated according to the following the equation: Refractive Index: N λ (nm) R. I November 2, 2007 N49-1. Rihua Mao, Caltech 7

8 Excitation, Emission, Transmittance Watch emission versus transmittance edge for self-absorption self-absorption: November 2, 2007 N49-1. Rihua Mao, Caltech 8

9 Scintillation Light Decay Time Recorded with an Agilent 6052A digital scope Fast Scintillators Slow Scintillators November 2, 2007 N49-1. Rihua Mao, Caltech 9

10 Light Output Measurement Wrapping: Tyvek Source: Cs-137 Gate: 45~ 4,000 ns System uncertainty <1% Temperature: 20 o C November 2, 2007 N49-1. Rihua Mao, Caltech 10

11 Light Output and Decay Kinetics Photoelectron/MeV measured with a XP2254B PMT Fast scintillators Slow scintillators Main decay time Main decay time November 2, 2007 N49-1. Rihua Mao, Caltech 11

12 PMT Quantum Efficiencies Emission weighted QE used to calculate Photons/MeV Emission weighted QE is calculated according to the following equation: Where QE(λ): quantum efficiency of cathode Em(λ): scintillation intensity November 2, 2007 N49-1. Rihua Mao, Caltech 12

13 Light Output and Decay Kinetics Light output, decay time & relative L.O. with PMT QE taken out Relative L.O. Relative L.O November 2, 2007 N49-1. Rihua Mao, Caltech 13

14 Temperature Coefficient Measurement A NESLAB circulator used to keep sample at a fixed temperature with precision 0.01 o C Sensitivity of PMT cathode versus temperature checked by LED November 2, 2007 N49-1. Rihua Mao, Caltech 14

15 Light Output Temperature Coefficient Temperature Range: 5 ~ 35 o C November 2, 2007 N49-1. Rihua Mao, Caltech 15

16 BaF 2 : Fast and Slow Components Two filters used to select scintillation component Transmittance for filter BPF-214 (fast component) Transmittance for filter BPF-300 (slow component) Scintillation of BaF 2 has two components: the fast one peaked at 220 nm while the slow one peaked at 300 nm. Special band pass filters were used to measure the light output temperature coefficients for individual component. November 2, 2007 N49-1. Rihua Mao, Caltech 16

17 BaF 2 Light Output Temperature Coefficient Fast and slow components have very different temperature coefficient Fast Slow November 2, 2007 N49-1. Rihua Mao, Caltech 17

18 Light Output Temperature Coefficient Temperature Range: 15 ~ 25 o C November 2, 2007 N49-1. Rihua Mao, Caltech 18

19 Table of Inorganic Scintillators Crystal NaI(Tl) CsI(Tl) CsI(Na) CsI CeF 3 BaF 2 BGO PWO(Y) LSO(Ce) Density (g/cm 3 ) Melting Point (ºC) Radiation Length (cm) Molière Radius (cm) Interaction Length (cm) Refractive Index a Hygroscopicity Yes Slight Slight Slight No No No No No Luminescence b (nm) (at peak) Decay Time b (ns) Light Yield b,c (%) d(ly)/dt b (%/ ºC) a. at peak of emission; b. up/low row: slow/fast component; c. QE of readout device taken out. November 2, 2007 N49-1. Rihua Mao, Caltech 19

20 Summary A comparative study on inorganic crystal scintillators commonly used in high energy physics experiments was carried out. Refractive indices for LSO/LYSO were measured by using a V-prism. Relative light output was measured for samples of 1.5 X 0 with Tyvek wrapping and with quantum efficiencies of the readout devices taken out. Light output temperature coefficients at room temperature were measured. Result presented here will be used in the inorganic scintillator section of the 2008 PDB. November 2, 2007 N49-1. Rihua Mao, Caltech 20

Microsoft PowerPoint - ryz_030708_pwo.ppt

Microsoft PowerPoint - ryz_030708_pwo.ppt Long Term Recovery of Seven PWO Crystals Ren-yuan Zhu California Institute of Technology CMS ECAL Week, CERN Introduction 20 endcap and 5 barrel PWO crystals went through (1) thermal annealing at 200 o