Ioan Dafinei Regional Centre ECAL-CMS Rome ITALY Villa Olmo, Como October 2001 Advanced Technology and Particle Physics Lead Tungstate Crystals for the CMS Electromagnetic Calorimeter at the LHC Ioan Dafinei I.N.F.N. Sezione di Roma, Rome ITALY (on behalf of CMS ECAL Collaboration)

Ioan Dafinei Regional Centre ECAL-CMS Rome ITALY Villa Olmo, Como October 2001 Advanced Technology and Particle Physics Index 1.Introduction 2.PWO General Properties -Luminescence Spectrum -Scintillation characteristics -Radiation hardness 3.PWO for ECAL-CMS -R&D Short Review -Requisites & Qualification Parameters -Regional Centers 4.Preproduction Crystal Properties Present Status 5.Recent Developments in PWO Crystal Growth Technology 6.Conclusions

Ioan Dafinei Regional Centre ECAL-CMS Rome ITALY Villa Olmo, Como October 2001 Advanced Technology and Particle Physics Introduction Requirements for scintillators to be used for ECAL construction ECAL-CMS high density and high Z mechanical ruggedness chemical stability uniformity of properties low price small X 0 small R m large LY short dead time fast radiation hard technological requirements high stopping power high granularity high energy resolution LHC Luminosity cm -2 ·s -1 Bunch separation 25 ns emission spectrum overlapping with spectral sensitivity of commonly used photodetectors high refractive index

Ioan Dafinei Regional Centre ECAL-CMS Rome ITALY Villa Olmo, Como October 2001 Advanced Technology and Particle Physics Workshop on tungstate crystals SCINT Conferences Introduction Studied as scintillator since 1979 PbWO 4 (PWO) (g/cm3) 8.26 X 0 (cm)0.89 R m (cm)2.2 (ns) 15 emission 420 emission 2.29 LY2 % LY temp.coeff. -2%/°C

Ioan Dafinei Regional Centre ECAL-CMS Rome ITALY Villa Olmo, Como October 2001 Advanced Technology and Particle Physics Bridgman method Shanghai Institute of Ceramics, China PWO General Properties PWO Crystal Growth Chang, mole % WO 3 PbO Liquid 16.5% 37% 66.5% 1123° 970° 740° 915° 935° 730° 2:11:1 PWO 4 PWO 3 seed grown crystal molten PWO RF heating Czochralski method Bogoroditsk Techo Chemical Plant, Russia

Ioan Dafinei Regional Centre ECAL-CMS Rome ITALY Villa Olmo, Como October 2001 Advanced Technology and Particle Physics PWO1168 green component PWO1180 blue component PWO1185 PWO General Properties Luminescence Spectrum a c WO 4 2- Pb 2+ a c WO 4 3- (MoO 4 ) 3- a c (WO 6 ) 6-

Ioan Dafinei Regional Centre ECAL-CMS Rome ITALY Villa Olmo, Como October 2001 Advanced Technology and Particle Physics PWO General Properties Scintillation Characteristics I tot I(t)=0.5·exp(-t/3ns)+0.07·exp(-t/12ns)+0.008·exp(-t/102ns) I ss =100·(I ss /I tot ) (%) Spectrally unresolved scintillation exc =308 nm (XeCl excimer laser) Photoluminescence decay

Ioan Dafinei Regional Centre ECAL-CMS Rome ITALY Villa Olmo, Como October 2001 Advanced Technology and Particle Physics PWO General Properties Scintillation Characteristics light yield (a.u.) temperature (°C) 20°C = -1.98%/°C I.Dafinei, Mat.Res.Soc. Vol.348(1994), p light yield (a.u.) temperature (°C) temp.coeff.(%/°C)

Ioan Dafinei Regional Centre ECAL-CMS Rome ITALY Villa Olmo, Como October 2001 Advanced Technology and Particle Physics PWO General Properties Radiation Hardness light production is not affected creation of color centres is quenched by appropriate doping

Ioan Dafinei Regional Centre ECAL-CMS Rome ITALY Villa Olmo, Como October 2001 Advanced Technology and Particle Physics R&D Short Review 1992 : Crystal2000 Conference 1994 : choice of PWO for CMS-ECAL : R&D phase Transmission (%) Wavelength (nm) Theoretical transmission '95 crystal '98 crystal : Pre-Production of 6000 crystals 2001 : Start of the Production

Ioan Dafinei Regional Centre ECAL-CMS Rome ITALY Villa Olmo, Como October 2001 Advanced Technology and Particle Physics R&D Short Review Goals of Pre-production Activity For Producer : Increase the rate of production Improve the crystal quality and homogeneity of properties For CMS-ECAL community Setting up the Regional Centres Installation of Automatic Crystal Control System (ACCOS) (machines designed to make the full characterisation of 30 crystals in 7 hours) All the 6000 crystals have been measured on ACCOS at CERN 800 re-measured on ACCOR at Rome (ACCOS-ACCOR intercalibration)

Ioan Dafinei Regional Centre ECAL-CMS Rome ITALY Villa Olmo, Como October 2001 Advanced Technology and Particle Physics Requisites & Qualification Parameters Qualification parameters Light Yield 0 8 pe/MeV at 18°C %/X 0 FNUF %/X 0 LY(100ns)/LY(1 s) > 90% 0 =7.5·a+b FNUF =100·(-0.89·a)/(11.5·a+b) LY(x)= a · x+b

Ioan Dafinei Regional Centre ECAL-CMS Rome ITALY Villa Olmo, Como October 2001 Advanced Technology and Particle Physics Requisites & Qualification Parameters Qualification parameters Transmission LT 360nm 25% LT 420nm 55% LT 620nm 65% LTslope inflection > 3%/nm TT=50% 3nm TT LT Check general quality and radiation resistance LT TT T=p 2 ·exp(-(p 3 )/w-exp((p 0 -w)·p 1 ))

Ioan Dafinei Regional Centre ECAL-CMS Rome ITALY Villa Olmo, Como October 2001 Advanced Technology and Particle Physics dimensions within mm, mm of nominal values planarity for all faces within 0.02 mm chamfers between 0.3 mm and 0.7 mm polished faces with roughness < m unpolished face with roughness = m ECAL-CMS Requisites & Qualification Parameters Qualification parameters Dimensios !

Ioan Dafinei Regional Centre ECAL-CMS Rome ITALY Villa Olmo, Como October 2001 Advanced Technology and Particle Physics Regional Centers CERN Lab.27 Regional Center Dimensions Light yield uniformity Transmission ACCOCE CERN Lab.27 EP-CMA

Ioan Dafinei Regional Centre ECAL-CMS Rome ITALY Villa Olmo, Como October 2001 Advanced Technology and Particle Physics Regional Centers Rome, Italy Regional Center Casaccia Co 60 PM LED Light yield uniformity Dimensions Coord3 S.p.A. Dark room temperature : 20±0.5°C rel. humidity: 50±10% ACCOR Capacity: 35 crystals/run 1 run time: approx. 10 hours Transmission

Ioan Dafinei Regional Centre ECAL-CMS Rome ITALY Villa Olmo, Como October 2001 Advanced Technology and Particle Physics Regional Centers ACCOS-ACCOR Intercalibration Measure 2-3 pe ! LY>8pe/MeV R-C =0.8pe/MeV R-C =0.19%/X o -0.35<FNUF(%/X o )<+0.35

Ioan Dafinei Regional Centre ECAL-CMS Rome ITALY Villa Olmo, Como October 2001 Advanced Technology and Particle Physics Regional Centers ACCOS-ACCOR Intercalibration R-C =1.4% R-C =0.8% R-C =0.5%

Ioan Dafinei Regional Centre ECAL-CMS Rome ITALY Villa Olmo, Como October 2001 Advanced Technology and Particle Physics Regional Centers ACCOS-ACCOR Intercalibration R-C =0.15%/nm Roma TTsp (nm) Cern TTsp (nm) TT spread at 50% Inflection Wavelength Rome Cern Rome (%/nm) Cern (%/nm) Rad hard check LT R-C =0.15%/nm

Ioan Dafinei Regional Centre ECAL-CMS Rome ITALY Villa Olmo, Como October 2001 Advanced Technology and Particle Physics Regional Centers ACCOS-ACCOR Intercalibration Statistics made on 373 Xtals CF AF BF CR AR BR

Ioan Dafinei Regional Centre ECAL-CMS Rome ITALY Villa Olmo, Como October 2001 Advanced Technology and Particle Physics Pre-Production Crystal Properties Wavelength (nm) Longitudinal Transmission (%) Transmission at 420nm (%) 6000 crystals no.of Xtals 55% Number of crystals Transmission at 420nm (%) Mean: 61.88% StDev. : 7.5% batch Transmission at 420nm (%) Mean: 69.01% StDev. : 1.59% batch 8 Transmission at 420nm (%) Mean: 70.07% StDev. : 1.46% batch 14

Ioan Dafinei Regional Centre ECAL-CMS Rome ITALY Villa Olmo, Como October 2001 Advanced Technology and Particle Physics Pre-Production Crystal Properties (nm) # crystals (%/nm) # crystals Pre-Production in China (%) # crystals # crystals (%) # crystals (%) Transmission characteristics Statistics made on 100 crystals

Ioan Dafinei Regional Centre ECAL-CMS Rome ITALY Villa Olmo, Como October 2001 Advanced Technology and Particle Physics Pre-Production Crystal Properties Batch 1 to 7 depolished face +0.2 Batch 8 to 14 depolished face NuF Front (%/Xo) FNUF (pe/MeV) NuF Front (%/Xo) FNUF (pe/MeV)

Ioan Dafinei Regional Centre ECAL-CMS Rome ITALY Villa Olmo, Como October 2001 Advanced Technology and Particle Physics Pre-Production Crystal Properties (ACCOS measured) LY (p.e./MeV) # crystals Pre-Production in China Light production characteristics Statistics made on 100 crystals

Ioan Dafinei Regional Centre ECAL-CMS Rome ITALY Villa Olmo, Como October 2001 Advanced Technology and Particle Physics Pre-Production Crystal Properties Front irrad., 1.5Gy, 0.15Gy/h LY irr /LY 0 (%) LYloss=(LY 0 -LY irr )/LY 0 (%)

Ioan Dafinei Regional Centre ECAL-CMS Rome ITALY Villa Olmo, Como October 2001 Advanced Technology and Particle Physics Pre-Production Crystal Properties LY loss (%) N = 32 Xtals StDev : 1.21% Mean : 3.39% batch 1 Front irrad., 1.5Gy, 0.15Gy/h LY loss (%) Statistics on 368 crystalsMean : 2.45 % StDev : 1.06% Rejected for LTslope < 1.5%/m Rejected for < 10% batch N = 33 Xtals LY loss (%) StDev : 0.9% Mean : 1.92% batch 14 N = 19 Xtals StDev : 1.21% Mean : 0.92% LY loss (%)

Ioan Dafinei Regional Centre ECAL-CMS Rome ITALY Villa Olmo, Como October 2001 Advanced Technology and Particle Physics Pre-Production Crystal Properties Pre-Production in China Radiation hardness characteristics Change of total light output during front irradiation at 0.15 Gy/h data for 21 crystals LY irr /LY 0 (%)

Ioan Dafinei Regional Centre ECAL-CMS Rome ITALY Villa Olmo, Como October 2001 Advanced Technology and Particle Physics Pre-Production Results 6000 Crystals produced by BTCP Increased production rate yield Improved stability of parameters Xtals quality Sept to Dec. 2000

Ioan Dafinei Regional Centre ECAL-CMS Rome ITALY Villa Olmo, Como October 2001 Advanced Technology and Particle Physics To be produced before end 2004 : crystals for Barrel crystals for Endcaps Present status : 6000 preproduction crystals 2000 production crystals increased productivity is needed New crystal development : Ingot diameter increase Production Schedule Started in 2001

Ioan Dafinei Regional Centre ECAL-CMS Rome ITALY Villa Olmo, Como October 2001 Advanced Technology and Particle Physics Recent Developments 1996 Barrel 32 mm 1999 Endcap 44 mm End 2000 Barrel 65 mm Crystal Growth Technology Steps

Ioan Dafinei Regional Centre ECAL-CMS Rome ITALY Villa Olmo, Como October 2001 Advanced Technology and Particle Physics Recent Developments = 32 mm = 65 mm PWO crystals made in BTCP Bogoroditsk

Ioan Dafinei Regional Centre ECAL-CMS Rome ITALY Villa Olmo, Como October 2001 Advanced Technology and Particle Physics Recent Developments Large PWO crystals made in BTCP Bogoroditsk time (ns)% A. N. Anenkov et all, Scint2001 Conference scintillation characteristics

Ioan Dafinei Regional Centre ECAL-CMS Rome ITALY Villa Olmo, Como October 2001 Advanced Technology and Particle Physics Recent Developments A. N. Anenkov et all, Scint2001 Conference saturation dose radiation hardness longitudinal uniformity Large PWO crystals made in BTCP Bogoroditsk

Ioan Dafinei Regional Centre ECAL-CMS Rome ITALY Villa Olmo, Como October 2001 Advanced Technology and Particle Physics Recent Developments radiation hardness radial uniformity centerside A. N. Anenkov et all, Scint2001 Conference Large PWO crystals made in BTCP Bogoroditsk

Ioan Dafinei Regional Centre ECAL-CMS Rome ITALY Villa Olmo, Como October 2001 Advanced Technology and Particle Physics Recent Developments radiation hardness Large PWO crystals made in BTCP Bogoroditsk PWO st irradiation at the Geneve Hospital i1 1irr1 Irr1 + 20' Irr1 + 40' Irr1 + 24h Transmission (%) Wavelength (nm) 60 Co 430 Gy

Ioan Dafinei Regional Centre ECAL-CMS Rome ITALY Villa Olmo, Como October 2001 Advanced Technology and Particle Physics count s Transmission at 420nm (%) N = 300 Mean: 69.91% StDev : 0.85% Batch P2 from CERN/ISTC production contract #1718 was used to compare: –260 barrel crystals produced with the standard technology –40 barrel crystals produced with the new technology New vs Old Technology count s Transmission at 360nm (%) N = 300 Mean: 31.36% StDev : 3.3%

Ioan Dafinei Regional Centre ECAL-CMS Rome ITALY Villa Olmo, Como October 2001 Advanced Technology and Particle Physics 260 barrel crystals produced with the standard technology 40 barrel crystals produced with the new technology New vs Old Technology (%/nm) N = 300 crystals Mean : 3.30%/nm StDev : 0.06%/nm LT counts N = 300 crystals Mean : 9.1 pe/MeV StDev : 0.57 pe/MeV Light Yield (pe/MeV) counts

Ioan Dafinei Regional Centre ECAL-CMS Rome ITALY Villa Olmo, Como October 2001 Advanced Technology and Particle Physics New vs Old Technology Front irrad., 1.5Gy, 0.15Gy/h

Ioan Dafinei Regional Centre ECAL-CMS Rome ITALY Villa Olmo, Como October 2001 Advanced Technology and Particle Physics Success of the R&D phase –Increase of the production rate –good quality crystals –uniform optical properties Technology for ingots up to 65mm diameter is now well under control The possibility to further increase the as grown PWO diameter and to apply this approach to endcap crystals is realistic Present status of physics and technology of scintillating materials shows that the CMS Collaboration decision to use PWO crystals for the ECAL construction was the best possible choice Conclusions

Ioan Dafinei Regional Centre ECAL-CMS Rome ITALY Villa Olmo, Como October 2001 Advanced Technology and Particle Physics Ready to Construct the CMS-ECAL 1st module of 400 crystals build in 2001 for ECAL CERN Lab.27 EP-CMA Casaccia & Conclusions