scintillating crystals for particle physics

PPARC forum on developments in scintillator technology 17.9.02 R M Brown - RAL 1

Scintillating Crystals forParticle Physics

Outline

Performance considerations

Table of crystal properties

Properties of Lead tungstate

Lead tungstate in CMS

Other future experiments

Summary


Performance Considerations

Light yield

Speed (scintillation decay time)

Radiation length / Molière radius

Resistance to radiation-induced darkening

Emission spectrum

Cost (including implications for associated detectors)

The relative weight given to these considerations depends on the application.

The choice of crystal usually involves a compromise


Crystal Properties

NaI CsI CsI CsI BGO BaF2 CeF3 PWO LSO HfF4 NE (TI) (TI) (Na) (Ce) glass 110

Light Yield (ph/MeV)

4.104 5.104 4.104 200 9000 1.104

1400

1600 100 3.104 160 1.104

max (nm)

(slow/fast) 410 565

/420 420 450

/320 480 310

/220 310 /340

530 /440

440 325 434

Decay (ns) (slow/fast)

230 600 /3.5

630 1000 6-28

300 600 /0.8

30 /9

40 /10

40 25 /10

3.3

Radiation length (cm)

2.59 1.86 1.86 1.86 1.12 2.06 1.68 0.89 1.14 1.60 43

Moliere radius (cm)

4.8 3.8 3.8 3.8 2.3 3.4 2.6 2.2 2.3 2.6

Density (g/cm3)

3.7 4.5 4.5 4.5 7.1 4.9 6.2 8.3 7.4 6.0 1.0

Refractive Index

1.85 1.80 1.84 1.95 2.15 1.50 1.68 2.16 1.81 1.50 1.58

Rad Hard (krad)

0.1 1.0 1.0 10 1.0 1.0 103 103 105 10

Hygro- scopic?

Yes Slight Weak Slight No No No No No No No

Cost ($/cm3)

1-2 2 3 10 2.5 3 1.5 100 1?


Lead Tungstate Properties

Advantages:• Fast• Dense• Radiation hard• Emission in visible

Disadvantages:• Temperature dependence• High refractive index• Low light yield Photodetector with gain

PWO Radioluminescence Spectrum

0

5

10

15

20

340 380 420 460 500 540 580 620

Wavelength (nm)

Inte

ns

ity

Density [g/cm3] 8.28

Radn length,X0 [mm] 8.9

Interaction length [mm] 224

Molière radius [mm] 21.9

Decay time [ns] 5(39%)15(60%)100 (1%)

Refractive index 2.30

Max emission [nm] 425

Light yield [photon/MeV] ~50

Temp coeff [%/ºC] -2


Compact Muon Solenoid

Total mass : 12,500tOverall Diameter: 15.0mOverall Length: 21.6mMagnetic field: 4T

ECAL

Superconducting coil

HCAL


CMS ECAL Layout

6.3 m

2.6 m

Parameter Barrel End caps

Xtal size (mm3)Depth in X0

21.8 × 21.8 × 23025.8

30.0 × 30.0 × 22024.7

No. crystalsVolume (m3)Xtal mass (t)

612008.1467.4

146642.7722.9

Full projective geometry (‘Off-pointing’ by 3o)

Barrel: 17x2 Crystal typesEnd cap: 1 Crystal type


PWO Production at BTCP - Russia


ALICE (A Large Ion Collider Expt for LHC)

PHOS


PHOS (Photon Spectrometer)

Crystals from North Crystals-Apatity

17 280 Crystals

(180 x 22 x 22 mm3)

1.5 m3, ~12.5 t

PbWO4 with PIN Diode readout


BTeV at Fermilab

Due to start

in 2008


BTeV Electromagnetic Calorimeter

PbWO4 with pmt readout

10 000 Crystals

(220 x 28 x 28 mm3)

1.7 m3, ~14.3 t

Prototype crystals:- Shanghai Institute of Ceramics- Bogoroditsk (BTCP)


MECO (Muon-electron conversion) BNL

Electromagnetic Calorimeter

Crystal option:

2300 crystals:120 x 30 x 30 mm3

BGO, PbWO4,(GSO)under consideration

APD Readout

Planned operation: 2006

Search for - e- (to 1 in 1017)


ANKE (Apparatus for studies of Nucleon and Kaon Ejectiles)

Photon detector proposed for ANKE at COSY (Jülich)

Due to operate in 2004


Photon detector for ANKE

0 0.5 m

800 Crystals

(120 x 20 x 20 mm3) x 35 x 35

0.075 m3, ~630 kg

PbWO4 with fine-mesh pmt readout


Primex at Jefferson Lab

PbWO4/Lead glass

1200 PbWO4 Crystals

180 x 20 x 20 mm3

Ordered from Shanghai Institute of Ceramics

HyCal (Hybrid Calorimeter)


Comparison: PbWO4, CeF3 , BaF2

Application to Medium Energy Physics (E( 1 GeV)(Novotny et al. NIM A486(2002) 131)

BaF2 considered as the bench mark

Conclude: PbWO4 performs well, despite limited light yield

CeF3 attractive, requires further development of large homogeneous crystals

Note: Studies elsewhere show light yield of PbWO4 (andenergy resolution) improved by doping with Tb or Mo- at expense of speed


Super B Factory

BaBar: 6580 CsI(Tl) Xtals

Belle: 8736 CsI(Tl) Xtals

Scheme for Super B Factory Detector

Super B Factory

Candidate crystals:

Pure CsI with APS

LSO or GSO with APD

( )


Summary

Several future high energy experiments require very large volumes of crystal scintillator

The material of choice is PbWO4

(Density, speed, radiation resistance, cost)

Despite low light yield, PbWO4 is also proposed for medium energy applications

Improvements in light yield through doping could extend the range of applications of PbWO4

Super B Factory might require a Fast, High light-yield, Radiation-resistant scintillator (CsI, GSO, LSO)


CMS Group at RAL - Interests

Electromagnetic Calorimeter design & construction

Photodetector development

Scintillator performance studies:Light yield, decay time using HEP Test Beam at ISISRadiation Hardness (in collaboration with Brunel)

Dense scintillating glass R&D(In collaboration with Sheffield, Dept of Engineering Materials)


Photodetectors: CMS ECAL end caps

•B-field orientation favourable for VPTs (Axes: 8.5o < || < 25.5o wrt to field)

•More radiation hard than Si diodes (with UV glass window)

• Gain 8 -10 at B = 4 T

• Active area of ~ 280 mm2/crystal

• Q.E. ~ 20% at 420 nm

= 26.5 mm

MESH ANODE

Vacuum Phototriode (VPT):Single stage photomultiplier tube with fine metal grid anode

scintillating crystals for particle physics

Documents

crystals220 x

m800 crystals120 x

choice of crystal

tprototype crystals

crystal typepwo production

north crystalsapatity17

radiation cm2

17x2 crystal typesend