R&D on CsI(Tl) + APD

Optimisation of the energy resolution

M. Gascón

I.Durán

R3B calorimeter

Total absorption efficiency 80 % (Eg=15 MeV lab) Very large crystals

Eg sum s(Esum)/<Esum> <10% (same as DE/E)

g Multiplicity s(Ng)/<Ng> < 10% Moliere Radius

DE/E for g 2-3 % Scintillation propertiesDetector granularity

DE/E for p (up to 300 MeV)Calorimeter for p

3 % Large crystalsDynamic range

Large dynamic range for detecting p,g

Inner radius 35 cm ( house Si trackers)

Main characteristics (from R3B Tech Proposal) :

R&D on crystals + readout systems

Design based on CAD + GEANT4 full simulations

see http://www.usc.es/~genp -> calorimeter -> reports and talks

Calorimeter sectors

Demonstrator meeting, Madrid May-09

Due to the Lorentz boost we identify three sectors:

ECM = 10 MeV

β = 0.82

88

15

45130

Crystals

!?

R3B/EXL meeting Milan Oct-06

Crystals

M. Mozynski et al., NIM A 485(2002)504 (API LAAPD)

CsI (Tl) 10x10x10, 10x10x50 ,10x10x100, 10x20x170 mm

CsI (pure) 10x10x10, 10x10x50 ,10x10x100 mm

LaCl3(Ce) 10x10x10, 10x10x50 ,10x10x100, 10x20x170 mm

Standard 10-stage, 19 mm tube, lima glass, Green bi-alkaliXP1901

Standard 10-stage, 19 mm tube, fused silica, UV bi-alkaliXP1918

Standard 10-stage, 25 mm tube, borosilicate glass, bi-alkaliXP3102

19 mm2 UV extended (200-1000 nm)S5345+ API

10x10 mmS86641010(PANDA)

5x5 mmS8665-55 (CMS)

St

Gob

ain

Pho

toni

sH

amam

atsu

R3B/EXL meeting Milan Oct-06

Material we used for test

R&d on crystals and APDs

Crystals from StGobain (France) tested coupled to LAAPD from Hamamatsu (Japan) and API (USA)

R3B/EXL meeting Milan Oct-06

Data-taking setups

Standard pulse-height analysis :

- preamplifiers: Canberra 2001A, Ortec R142

- Shapping amplifier: Canberra 2022

- Multichannel analyzer: Ortec Maestro or Amptek MCA-8000

Pulse-shape analysis :

- Oscilloscope Tektronix TDS3054B

- Off-line Digital filtering: Trapezoidal finite-impulse algorithm

Not used for APDs but providing the best results for PMT!

Experimental setup

Test at Genp-Lab (USC)

Test at Genp-Lab (USC)

APD gain vs. Bias Voltage

5 cm length

The energy resoltution depends on the APD gain and the Bias Voltage

~380V Dgain/DV= 2.84 %

The energy resoltution shows a minimum when The APD Bias Voltage=380

Dependence on shapping time

For small crystals 4ms is a good compromise between energy-resolution and pile-up

Dependence on the acquisition time

Best results achieved for acquisition times between 30-60 s

These curves conatin two effects: statistics and bias voltage drift.

Could be solved by controling Temperature and Bias Voltage

Dependence on Amplifier Gain

Energy resolution improves by increasing the amplifier gain

Best results

Study of the non-uniformity

Energy resolution dependence on the first interaction point

Non-uniformity ~ 8.4 %, to compare with < 3% measured by St. Gobain

Light collection uniformity CMS CAL

P. Sempere PhD Thesis

CsI(Tl) Resolution

R3B/EXL meeting Milan Oct-06

Energy resolution improves for increasing energy

CsI(Tl) with a 60Co source

(1171 keV) and (1332 keV)

Some conclusions

• Several test (wrapping, optical coupling,amplifier gain, shapping time) have been performed to optimise the energy resolution of CsI(Tl)

•APDs from API showed the best energy resolution for CsI(Tl) crystals•APDs S8664-1010 from Hamamatsu showed a very good energy resolution almost independent on the crysal size

• The main drawback of APDs vs PMT is the strong dependence of the gain with Temperature and Bias Voltage

How to improve the resolution:

-Better stabilisation of both temperature and bias-voltage.- Better optical coupling --> Scionix- Surface coating --> Ukranian Institute for Crystals

- New generation of scintillating crystals

T and V dependence

Both Crystals and APDs response depends on Tº

T must be kept very stable ! ~0.1o

otherwise, T should be accurately measured in order to keep gain constant by controlling the bias voltage

Characterization of S8664-1010 APD

T. Ikagawa et al., NIM A 538(2995) 640

T stabilisation ~0.1ºC keep the gain variarion ~ 0.3%

Temperature stabilisation

Refrigerator 4-5 º C

Humidity control box < 30% (1%)

radiator

Resistor warm focusT probe T stable within 0.1ºC

Ceramics Cold focus~ 10ºC

T controller

22ºC

Allow pulse shape analysis with Tektronix TDS3054B

Crystal type-2 Bi-frustrum shaped

Waiting for an agreement with StGobain and IMP- Lanzhou(China) --> Price drop!

Exit face fits to LAAPD S8664-2010 under negotiation

First prototypes done at Lanzhou (China

Further tests through prototype

• Good results are only achieved when there is a perfect matching between the crystal exit surface and the APD entrance area

Type 2 View of the Barrel

average dimensions

3x1x13 cm

Study of St. Gobain vs IMP Lanzhou crystals

Tests performed with API APD Crystal dimensions 1x1x1 cm

Very similar behaviour

Resolution achieved

IMP Lanzhou St. Gobain

R3B Type Crystal

Uniformity of the crystal

Wrapped with ESR (from 3M), tested with 60Co

0 2 4 6 8 10 12 14 16 18 201500

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Rel

ativ

e Li

ght-

out(

arbi

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its)

CsI Position

The light-out uniformity is 2.8%