CALICE MeetingDESY 14.02.07

ITEP&MEPhI status report ontile production and R&D activities

Michael Danilov ITEP

Status of tile production

Tiles for 32 cassettes have been delivered to DESY

Tiles for cassette # 33 are ready

We have good SiPM’s for 3 more cassettes

Delivery of SiPM’s is going smoothly

We expect all 38 cassettes ready for delivery by the end of March

Comparison of WLSF and direct SiPM coupling

Tiles with WLS fiber

3 mm thick tile with diagonal fiber

3mm thick tile with arch fiber

Standard 5 mm thick tile with arch fiber

Uniformity is good enough and photo-electron yield is sufficient even for 3mm thick tiles

Vertical scale is shown for 1.5MIP

Tile thickness reduction can save a lot of money (~?/mm) or increase HCAL thicknessHowever the effect on the energy resolution (sampling fluctuations) should be estimated

CALICE main meeting, CERN, September 20-22, 2006 M.Danilov ITEP,Moscow

Direct SiPM coupling- desirable to simplify production, but …

Tile 30x30x5 mm3

SiPM

SiPM calibration

CALICE main meeting, CERN, September 20-22, 2006 M.Danilov ITEP,Moscow

Tile 30x30x5 mm3

SiPM on top of a tile

SiPM calibration

Uniformity measurements of 30x30x3mm3 tiles at ITEP synchrotron Arch Fiber&SiPM, 1.5MIP

Uniformity is even worse for 3 mm tiles

Light yield is sufficient for 3mm thick tiles with glued WLSF and SiPM (~15pix./MIP) and larger area SiPMs (3x3mm2) or MRS APD (2x2mm2 blue extended) but noise is too high in these detectors to resolve individual p.e. – bad for calibration

Problems with direct coupling will be more severe for larger size tiles

Direct coupling of 2x2mm2 blue MRS APD

MIP signal for 3x3mm2 SiPM

T241, t2, u=21.2 V

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ch

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SiPM

Tile

3M

Plastic scintillator 30x30x5 mm3 without WLS fiber and 3x3 mm2 SiPM assembly was tested at MEPhI (room temperature) with Sr90

Optical glue

Sr90

SiPM- tile assembly

Efficiency of light registration appr18%

Appr. 30 fired pixels/MIP

signal(x)

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-15 -10 -5 0 5 10 15

x, mmsig

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Noise probability & Light Collection Uniformityfor 3x3 mm2 SiPM-tile assembly

3*10-5 * 8000=0,24 events/prototype

21.2 V, strob 100 ns

0.0000001

0.000001

0.00001

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porog, MIP

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orog

)

Threshold, MIP

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se p

roba

bili

ty

abov

e th

resh

old

Absence of individual p.e. peaks is a serious drawback for calibration

Photo-electron yield for direct MPPC coupling to 30x30 mm^2 tiles

5 mm thick tile, MPPC at side center 3 mm thick tile, MPPC at side center

Gluing increases photo-electron yield for 5 mm thick tiles

Photo-electron yield is too small for 60x60 mm^2 tiles (~2p.e. without gluing)

MPPC in tile corner Glued MPPC in tile corner

350 400 450 500 550 600 650 700

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Wavelength , nm

MPPC Studies

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Overvoltage U, V

PDE agrees well with the MPPC specification

ΔU=1.7V

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Hz (du=1,7V) ExpGro1 fit of f1etemp_f1e

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Temperature C

overvoltage = 1,7 V

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akd

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Temperature C

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Data: Data4_BModel: ExpDec1 Equation: y = A1*exp(-x/t1) + y0 Weighting:y No weighting Chi^2/DoF = 1.1526E-7R^2 = 0.98635 y0 0.00044 ±0.00011A1 -0.02541 ±0.00072t1 7.83714 ±0.25206

Am

plitu

de, a

.u.

time, ns

B ExpDec1 fit of Data4_B

MPPC fast decay time indicates small R and fast recovery time

This leads to double signals from one pixel during a long pulse

LED pulse 28ns

Measurements at DESY and ITEP give 7-9 p.e./MIP for direct MPPC (1600pix)readout of 5mm thick 30x30mm2 tiles and ~5p.e./MIP for 3mm thick tile

MPPC do not provide enough p.e. for direct readout of 3x30x30mm tilesPhoto-electron yield is even smaller for larger tiles (~2p.e. for 60x60x5mm3 tile)

Larger size MPPC can be adequate for direct tile readout since noise is not a limiting factorHowever long term stability and radiation hardness should be demonstrated

MPPC saturation curve dependence on pulse length create problems for calibration

MPPC 28 and 37nsLED pulses

SiPM, R~28 and 37nsLED pulses

Radiation damage measurements

ITEP SynchrotronProtons E=200MeV(preliminary)

Dark current increases linearly with flux Φ as in other Si devices:

Δ I=α Φ Veff Gain, where α=6x10-17A /cm

Veff ~ 0.004mm3 determined from observed ΔI looks a bit too high (since it includes SiPM efficiency)but not completely unreasonable

Since initial SiPM resolution of ~0.15 p.e. is muchbetter than in other Si detectors it suffers sooner:After Φ~1010 individual p.e. signals are smeared out

However MIP signal are seen even after Φ~1011/cm2

At ILC neutron flux is much smaller than 1010/cm2

except a small area (R<50cm) around beam pipe

→ Radiation hardness of SiPM is sufficient for HCAL

Comparison of different Multipixel Geiger Photo Diods (MGPD)

MGPD were illuminated withY11 (green) and scintillator (blue) light

Efficiency was normalizedto MPPC one

.

Noi

se

freq

uenc

y

Scintillator strips with WLSF and SiPM readout can be used for ILC muon system

Cosmics

N pixels =20

Tests of 2 m long strip at ITEP

Position along strip can be determined from time measurements: ΔT~2ns leads to ΔX~25cm(ΔT~2ns was already achieved)

Conclusions

Scintillator tile calorimeter with WLSF and SiPM readout is a viable option for ILC HCAL but industrialization is needed for several hundred times larger system

Thin scint. strips with WLSF+SiPM readoutprovide sufficient light and uniformity (~6%)for last layers of EM calorimeter(approach tested extensively by Japanese groups)

Uniformity measurements for 3x10x45 mm3 strip with WLSF and SiPM readout

Summary

ILC HCAL prototype is the first (and successful!) large scale (~104) applicationof novel photo-detectors – SiPMsAmong 4536 channels in cassettes 3-23 only 1.1% are dead (soldering problems)and 1.1% show long discharges (reason for long discharges was understood, will be fixed in next SiPM version)Within errors situation is stable in time

Scintillator tile calorimeter with WLSF and SiPM readout is a viable option for ILCfor analog and semi-digital approaches, but a lot of industrialization is requiredThe same technique can be used for ILC muon system and last layers of ECAL

Possibility to use direct MGPD coupling is still to be demonstrated(uniformity and p.e. yield)

The field is developing very fast. Photo-detector properties improve every year.The final choice of the Photo-detector depends on the overall optimization

Selection between Analog, Digital or Semi-Digital approaches depends on the outcome of the test program at CERN and FNAL