Lead Tungstate Crystals for the CMS Electromagnetic ... · PDF fileAdvanced Technology and Particle Physics Lead Tungstate Crystals for the CMS ... RomeLT@420 CernLT@420 RomeLT@620

Ioan DafineiRegional Centre ECAL-CMS Rome ITALY

Villa Olmo, Como 15-19 October 2001

Advanced Technology and Particle Physics

Lead Tungstate Crystals for the CMS Electromagnetic Calorimeter at the LHC

Ioan DafineiI.N.F.N. Sezione di Roma, Rome ITALY

(on behalf of CMS ECAL Collaboration)




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




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 X0

small Rm

large LY

short dead time fast

radiation hard

high stopping power

high granularity

high energy resolution

LHC

Luminosity 1034 cm-2·s-1

Bunch separation 25 ns

emission spectrum overlapping with spectral sensitivity of commonly used photodetectors

high refractive

index

technological requirements




Introduction

Workshop on tungstate crystals

0

20

40

1992 1993 1994 1995 1996 1997 1998 1999 2000 2001

PWO propertiesPWOusersPWO+Othertotal

ArticleStatistics.QPC

SCINT Conferences

Studied as scintillator since 1979PbWO4 (PWO)

ρ (g/cm3) 8.26X0 (cm) 0.89Rm (cm) 2.2τ (ns) 15λemission 420n@ λemission 2.29

LY 2 %LYtemp.coeff. -2%/°C




PWO General Properties

PWO Crystal Growth

Chang, 1971

1100

1000

900

800

700

20 40 60 80

mole %

WO3PbO

Liquid

16.5%

37%

66.5%

1123°

970°

740°

915°935°

730°

2:1

1:1

PWO4PWO3





Bridgman method

Shanghai Institute of Ceramics, ChinaPWO Crystal Growth

seed

grown crystal

molten PWO

RF heating

Czochralski method

Bogoroditsk Techo Chemical Plant, Russia





LumSp ectra- B +G.QPC

PWO1168

LumSp ectra- green .QPC

green component

PWO1180

0

0.2

0.4

0.6

0.8

1

1.2

300 400 500 600 700

inte

nsity

(a.

u.)

wavelength (nm)

295 K

LumSpec tra-b lue.QPC

blue component

PWO1185

Luminescence Spectrum

a

c WO42-

Pb2+

(WO6) 6-

(MoO4) 3-

a

c

a

c

WO43-




PWO General PropertiesScintillation Characteristics

10-6

10-5

10-4

10-3

10-2

10-1

100

10-8 10-7 10-6 10-5

emision@400 nmemision@500 nmlaser pulse

inte

nsit

y (a

.u.)

time (s)L umL aser Exc.QP C

λexc=308 nm (XeCl excimer laser)

Photoluminescence decay

Itot

I(t)=0.5·exp(-t/3ns)+0.07·exp(-t/12ns)+0.008·exp(-t/102ns)

101

102

103

0 50 100 150 200 250 300 350

decay data3exp fittrue background

counts per channel

time (ns)D ecayIntegral.QPC

Iss

α=100·(Iss/Itot) (%)

Spectrally unresolved scintillation





Scintillation Characteristics

0

200

400

600

800

1000

1200

1400

-200 -150 -100 -50 0 50

light

yie

ld(a

.u.)

temperature (°C)

α20°C = -1.98%/°CI.Dafinei, Mat.Res.Soc. Vol.348(1994), p.99

50

100

150

200

250

300

-5

-4

-3

-2

-1

0

-20 0 20 40 60-40

light

yie

ld(a

.u.)

temperature (°C)

tem

p.co

eff.(

%/°

C)





Radiation Hardness

0

20

40

60

80

300 400 500 600 700 800

tran

smis

sion

(%

)

wavelength (nm)

undoped

La-doped

295 K

RadHar d.QP C

0

1

2

3

300 500 700 900

indu

ced

abso

rptio

n (m

-1)

w avelength (nm)

undoped

La-doped

•light production is not affected

•creation of color centres is quenched by appropriate doping




R&D Short Review

• 1992 : Crystal2000 Conference• 1994 : choice of PWO for CMS-ECAL• 1994-1998 : R&D phase

0

20

40

60

80

100

300 350 400 450 500 550 600 650 700

Tra

nsm

issi

on (%

)

Wavelength (nm)

Theoretical transmission

'95 crystal

'98 crystal

1995 1998

• 1998-2000 : Pre-Production of 6000 crystals• 2001 : Start of the Production




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 communitySetting up the Regional CentresInstallation 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 CERN800 re-measured on ACCOR at Rome (ACCOS-ACCOR intercalibration)




Requisites & Qualification Parameters

Qualification parametersLight Yield

LY(x)= a · x+b

LY@8X0 =7.5·a+b

FNUF =100·(-0.89·a)/(11.5·a+b)

• LY@8X0 ≥ 8 pe/MeV at 18°C

• -0.35 %/X0 ≤ FNUF ≤ +0.35 %/X0

• LY(100ns)/LY(1µs) > 90%





Qualification parametersTransmission

0

20

40

60

80

300 400 500 600 700

LT1535557595115135155175195215

Tran

smis

sion

(%)

wavelength (nm)PWO1713_Ro.QPC

TTLT

LT

TT

T=p2·exp(-(p3)/w-exp((p0-w)·p1))

•LT360nm ≥ 25%

•LT420nm ≥ 55%

•LT620nm ≥ 65%

•LTslopeinflection > 3%/nm

• δλTT=50% ≤ 3nm

Check general quality and radiation resistance





Qualification parametersDimensios

•dimensions within +0.00 mm , -0.10 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 < 0.020 µm

•unpolished face with roughness = 0.350 µm

ECAL-CMS




Regional CentersCERN Lab.27 Regional Center

ACCOCE http://cmsdoc.cern.ch/cms/ECAL/html/wp/rc/

Light yield uniformity

CERN Lab.27 EP-CMA

Transmission

Dimensions




Regional Centers

Rome, Italy Regional Center http://www.roma1.infn.it/exp/cms/

Dark roomtemperature : 20±0.5°C rel. humidity: 50±10%

ACCOR

Capacity:35 crystals/run1 run time:approx. 10 hours

Dimensions

Coord3 S.p.A.

Casaccia

TransmissionCo60

PM

LED

Light yield uniformity




Regional Centers

ACCOS-ACCOR Intercalibration

Measure 2-3 pe !

LY>8pe/MeV

σR-C=0.8pe/MeV

σR-C=0.19%/Xo

-0.35<FNUF(%/Xo)<+0.35




Regional Centers


LT@360nm

0

10

20

30

40

50

60

0 10 20 30 40 50 60RomeLT@360

Cer

nLT@

360

60

65

70

75

60 65 70 75

LT@420nm

RomeLT@420

Cer

nLT@

420

RomeLT@620

Cer

nLT@

620

65

70

75

80

65 70 75 80

LT@620nm

σR-C=1.4% σR-C=0.8% σR-C=0.5%




Regional Centers


σR-C=0.15%/nm

00.5

11.5

22.5

33.5

4

0 0.5 1 1.5 2 2.5 3 3.5 4

Rom

a TT

sp (n

m)

Cern TTsp (nm)

TT spread at 50%

Inflection Wavelength

345

349

353

357359

345 349 353 357Rome

Cer

n

2

2.5

3

3.5

4

2 2.5 3 3.5 4Rome S@infl (%/nm)

Cer

n S@

infl

(%/n

m)

Rad hard check

LT slope@inflection

σR-C=0.15%/nm




Regional Centers


Statistics made on 373 Xtals

CF

AF

BFCR

AR

BR

229.5

230

230.5

229.5 230.0 230.5

L@Ro

ma

(mm

)

L@CERN (mm)

L

21.5

21.75

21.50 21.75

AF@

Rom

a (m

m)

AF@CERN (mm)

AF

22.4

22.6

22.8

22.40 22.60 22.80

BF@

Rom

a (m

m)

BF@CERN (mm)

BF

21.6

21.8

22.0

22.2

21.6 21.8 22.0 22.2

CF@

Rom

a (m

m)

CF@CERN (mm)

CF




Pre-Production Crystal Properties

0

2

4

6

8

10

30 35 40 45 50 55 60 65 70 75 80

Num

ber

of c

ryst

als

Transmission at 420nm (%)

Mean: 61.88%StDev. : 7.5%batch 1

Wavelength (nm)

0102030405060708090100

300 350 400 450 500 550 600 650 700

Lon

gitu

d ina

l Tra

n sm

i ssi

o n(%

)

0

200

400

600

800

1000

1200

1400

30 35 40 45 50 55 60 65 70 75 80


6000 crystals

no.o

f Xta

ls

55%

0

50

100

150

200

250

30 35 40 45 50 55 60 65 70 75 80Transmission at 420nm (%)

Mean: 69.01%StDev. : 1.59%

batch 8

Transmission at 420nm (%) 11.04.01

Mean: 70.07%

StDev. : 1.46%

0

50

100

150

30 35 40 45 50 55 60 65 70 75 80

batch 14





Pre-Production in China

0 10 20 30 40 50 60 70 80LT@360nm (%)

0

2

4

6

8

10

12

14

16

18

#cr

ysta

ls

0

2

4

6

8

10

12

14

16

#cr

ysta

ls

0 10 20 30 40 50 60 70 80LT@420nm (%)

0

5

10

15

20

25

30

35

40

45

#cr

ysta

ls

0 10 20 30 40 50 60 70 80LT@620nm (%)

Transmission characteristics

0

2

4

6

8

10

12

14

16

18

20

0.2 2.2 4.2 6.2 8.2 10.2TTspread@50% (nm)

#cr

ysta

ls

0

5

10

15

20

25

30

35

40

0.1 1.1 2.1 3.1Slope@infl (%/nm)

#cr

ysta

ls

Statistics madeon 100 crystals




Pre-Production Crystal PropertiesBatch 1 to 7 <Ra> depolished face +0.2µ

0

50

100

150

200

250

300

350

-1.5 -1 -0.5 0 0.5 1 1.5 2NuF Front (%/Xo)

FNUF

0

100

200

300

400

500

0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16LY@8X0 (pe/MeV)

LY@8X0

Batch 8 to 14 <Ra> depolished face +0.39µ

0

200

400

600

800

1000

1200

-1.5 -1 -0.5 0 0.5 1 1.5 2NuF Front (%/Xo)

FNUFLY@8X0

0

200

400

600

800

1000

1200

1400

0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16LY@8X0 (pe/MeV)





Pre-Production in ChinaLight production characteristics

Statistics madeon 100 crystalsLY@8X0 (ACCOS measured)

0

5

10

15

20

25

30

35

0 2 4 6 8 10 12 14 16LY (p.e./MeV)

#cr

ysta

ls





Front irrad., 1.5Gy, 0.15Gy/h

90

95

100

105

0 0.5 1 1.5 2 2.5

Low dose rate irradiation of some BTCP crystals of Batch06 in lab27

PWO4510 (%LY)

PWO4579 (%LY)

PWO4585 (%LY)

PWO4590 (%LY)

PWO4622 (%LY)

PWO4623 (%LY)

PWO4533 (%LY)

PWO4481 (%LY)

PWO4473 (%LY)

Dose (Gy)PWO_batch06lowdoselab27.qpcE. Auffray, EP_CMA

18/01/2000

LY

irr/L

Y0

(%) LYloss=(LY0-LYirr)/LY0 (%)





LY loss (%)

0

2

4

6

8

10

0 1 2 3 4 5 6 7 8 9 10

N = 32 Xtals StDev : 1.21%Mean : 3.39%

batch 1

batch 8

0

4

8

12

16

20 N = 33 Xtals

0 1 2 3 4 5 6 7 8 9 10LY loss (%)

StDev : 0.9%Mean : 1.92%

batch 14

N = 19 Xtals StDev : 1.21%Mean : 0.92%

0

4

8

12

16

20

0 1 2 3 4 5 6 7 8 9 10LY loss (%)


0

20

40

60

80

100

0 0.5 1 1.5 2 2.5 3 3.5 4 4.5 5 5.5 6 6.5 7 7.5 8 8.5 9 9.5 10

LY loss (%)

Statistics on 368 crystals Mean : 2.45 % StDev : 1.06%

Rej

ecte

d fo

r LTs

lope

< 1

.5%

/m

Rej

ecte

d fo

r LT@

350n

m <

10%





Pre-Production in ChinaRadiation hardness characteristics

95

96

97

98

99

100

101

102

103

104

105

0 2 4 6 8 10 12

SIC800 (%LY)SIC803 (%LY)SIC807 (%LY)SIC819 (%LY)SIC829 (%LY)SIC834 (%LY)SIC840 (%LY)SIC841 (%LY)SIC849 (%LY)SIC850 (%LY)SIC858 (%LY)SIC868 (%LY)SIC869 (%LY)SIC879 (%LY)SIC880 (%LY)SIC872(%LY)SIC891 (%LY)SIC883 (%LY)SIC892 (%LY)

Dose (Gy)

Change of total light output during front irradiation at 0.15 Gy/h data for 21 crystals

LY

irr/L

Y0

(%)




Pre-Production Results

Sept. 1998 to Dec. 2000

6000 Crystals produced by BTCP

0

200

400

600

800

1000

set-98

dic-98

mar-99

giu-99

set-99

dic-99

mar-00

giu-00

set-00

dic-00

Planning Delivered

0

10

20

30

40

50

set-98

dic-98

mar-99

giu-99

set-99

dic-99

mar-00

giu-00

set-00

dic-00

Dimensions TransmissionLight Yield Decay timeSlope/Rad.hardness

Increased production rateyield

Improved stability of parametersXtals quality




Production Schedule

Started in 2001

To be produced before end 2004 :•56000 crystals for Barrel•16000 crystals for Endcaps

Present status :•6000 preproduction crystals•2000 production crystals

increased productivity is needed

New crystal development :Ingot diameter increase




Recent Developments

Crystal Growth Technology Steps

1996

Barrel

32 mm

1999

Endcap

44 mm

End 2000

Barrel

65 mm




Recent Developments

PWO crystals made in BTCP Bogoroditsk

Φ = 32 mm

Φ = 65 mm




Recent Developments

Large PWO crystals made in BTCP Bogoroditsk

time (ns) %

30.0 80.350.0 89.9

100.0 96.4300.0 99.3

1000.0 99.91525.5 99.9

A. N. Anenkov et all, Scint2001 Conference scintillation characteristics




Recent Developments


A. N. Anenkov et all, Scint2001 Conference

saturation dose

radiation hardness

longitudinal uniformity




Recent Developments


radiation hardness

radial uniformitycenter side

A. N. Anenkov et all, Scint2001 Conference




Recent Developments


radiation hardnessPWO 7365 1st irradiation at the Geneve Hospital

0

20

40

60

80

100

300 350 400 450 500 550 600 650 700

1i11irr1Irr1 + 20'Irr1 + 40'Irr1 + 24h

Tra

nsm

issi

on (%

)

Wavelength (nm)

60Co

430 Gy




New vs Old Technology

30 35 40 45 50 55 60 65 70 75 80

LT@420

coun

ts


N = 300Mean: 69.91%StDev : 0.85%

0

20

40

60

80

100

120

140

LT@360

coun

ts

0

10

20

30

40

50

60

0 5 10 15 20 25 30 35 40 45 50 55 60 65 70Transmission at 360nm (%)

N = 300Mean: 31.36%StDev : 3.3%

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





0

20

4060

80

100120

140

0 1 2 3 4 5 6 7 8 9 10Slope@inflection (%/nm)

N = 300 crystals

Mean : 3.30%/nmStDev : 0.06%/nm

LT slope@inflection

coun

ts

0

50

100

150

200

250

300

5 6 7 8 9 10 11 12 13 14

N = 300 crystals

Mean : 9.1 pe/MeVStDev : 0.57 pe/MeV

LY@8X0

Light Yield (pe/MeV)

coun

ts

260 barrel crystals produced with the standard technology

40 barrel crystals produced with the new technology





90

92

94

96

98

100

0 1 2 3 4 5

Low dose rate irradiation of some crystals from BatchP2-1

PWO_P7277 (%LY)PWO_P7356 (%LY)PWO_P7365 (%LY)PWO_P7366 (%LY)

Dose (Gy)PWO_batchP2lowdoselab27_1.qpc E. Auffray, EP_CM10/06/2001





Conclusions

• 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

• 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




Conclusions

CERN Lab.27 EP-CMA

Casaccia

&Ready to Construct the CMS-ECAL

1st module of 400 crystals build in 2001 for ECAL

Documents

Lead Tungstate Crystals for the CMS Electromagnetic ... · PDF fileAdvanced Technology and Particle Physics Lead Tungstate Crystals for the CMS ... RomeLT@420 CernLT@420 RomeLT@620