Development of scintillation detectors with MRS APD light readout for CBM Muon

system and ECAL preshower

Alexander AkindinovITEP(Moscow) on behalf of

ALICE-ITEP group

Outlook

• MRS APD – fast Geiger mode high gain photodetector

• START – technology• ALICE CRTF – first implementation for START

technology• Counters for CBM muon systems• Counters for EMCAL preshower• Conclusion

MRS APD – fast Geiger mode high gain photodetector

-Voper

Readout

MRS APD structure

47 48 49 50 51 52 53U , VAPDg

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Entries 1019173e

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ADC channels

pede

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Single electron resolution is a result of dispersion of Ubr and Ccell across diode area.

Slope corresponds to elementary micro-cell capacity Q/U.

M = C*(U - Ubr)

Q = Ncell*C*(U - Ubr)

Many other name:SiPM, MPPC, GAPD…

Optical trench(CPTA) – low optical coupling between cells.Acceptable noise rate for reasonable thresholds

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Noise spectrum slope is a result of “red” cross-talks between cells, when avalanche in one cell initiate avalanche in neighboring one via photon.

Probability to have more than one pixel fired from a single primary e-h pair = (N n+1)/ (N n )

CPTA MRS APD α= 0.1 For 4th cell threshold noise count about a few kHzHigh geometrical factor

PDE is optimize for WLS fibers

P.D.E. = Q.E. * g* R εg – geometrical fill-factorR – probability to initiate Geiger avalancheQ.E. – quantum efficiency

START- (Scintillation Tile with MRS APD Light ReadouT)

Two MRS APD in coincidence

σ-shape groove for uniform response

“On board” FEE

Mosaic array

MRS APD optimize geometry (d=1.15 mm) for the fiber readout

Polisterol 165 150X150X10 mm1 groove, 2 rings Y11 and glued

Threshold

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Coincidence F1 * F2 * 100 ns (250 ns delay for Dn2)

Count ,

Hz

Threshold , mV

Cosmic μ

Signal/noise

First implementation - ALICE CRTF

Inner trigger counters

Outer trigger counters

TOF modules

Frame

Up to 5 ALICE TOF modules under the test.

Bottom plane10 strips 8 STARTs

in each (80 STARTS)

Upper plane10 strips 8

STARTs in each (80 STARTS)

Trigger and monitoring

•!!Monitoring the only by counting rate of individual detector, no any LED system was used.!!!•Efficiency was measured as difference in counting rate for 80 pairs.

Simple logic block for trigger configuration and monitoring were connected via USB to LabView

Long term operation results

Reason Number of diodes

Explanation Action

Leakage current increasing up to 20 μA

27 Bad insulation between metal and cell for trench technology

Informing CPTA, work in progress

Zero current 4 Bad bonding Negligible, but informing

CPTA

Total: 31 !!!!<10 % for 3 years continuos operation!!!!!

First real experiment with 320 new photosensors (CPTA firm MRS APD). About 3 years of continues operation, all 87 ALICE TOF modules was tested.

Summary of “dead” and replaced diodes

Counters for CBM muon system

INTAS Ref. Nr 06-1000012-8781“Develop and produce START prototypes adapted for dE/dx measurements. Five detectors of each of two types of START will be produced: tiles sized 100x100x 10 mm3 and strips sized 5x200x10 mm3

Tiles with different groove diameters to find optimal uniformity (d = 90, 80, 70, 60, 50 mm)

Strips 5x200x10 mm3

ROLAND milling machine!!!Many thanks to our friends from ITEP-CALICE group!!!!

New package to minimize “dead zone” and new connector

New transparent optical connector produced by the same digital milling machine as tiles

Very uniform response (about 8%). Main sources - regions near optical connectors and groove.

TO-18 New package

Diodes calibration and fiber cut

Setup to cut fiber with microscope

Each diode after placement into connector was checked (how well diode active area is with connector hole)

Mixer

12 channel board

Setup for diodes test

Diodes calibration and fiber cut

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I-U curve to find out breakdown point Number of photoelectrons for given light was checked

Single cell noise and photoionization (α) coefficient were measured

Detector assembly and electronics

FEE card for tiles

Simple amplifier for strips (10mm width)

Tiles were wrapped in Tyveсk and light shield

GND +4-+10 VLVDS

Amplitude 1(50 Ω)

Jumper 1 for coincidence(on)

Jumper 2 for coincidence(on)

Threshold

Ubias

Ubias сontrolTest input (50 Ω)Jumper 2 for test

LED

FEE for tiles

Amplitude 2(50 Ω)

Jumper 1 for test

First task: find optimal geometry for uniform response

D=50 mm

D=60 mm

D=70 mm

D=80 mm

D=90 mm

D 50 60 70 80 90

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Scans were done using Ru β – source with 2.5 mm collimator. 19x19 points (5 mm step).

New improved MRS APD (2007)

Data was taken from http://www.photonique.ch/Photonique SA C.P. 15621211 Geneva-1Switzerland

2005 – diodes for ALICE CRTF

New diodes 2007

Reduced thickness of n+ - PDE increased + blue enhanced

Light yield with old and new diodes

“43V” old “23V”new

N ≈16 ph.e.

Tile 150x150x10 mm3

N ≈ 29 ph.e.N ≈ 22 ph.e.

“23V”new

Tile 100x100x10 mm3

Beam test CERN PS (2x2 cm2 trigger center of tile)

With this significant improvement can we work with one diode?

Tiles with single diodes

So called “half-board” designed for long strips

100x100x10 mm3 with one output for fiber ( d=80 mm )

Three reasons to produce tiles with one diode:1.To check if we can improve light yield using another glue2.Check if we can work with one diode3.Make prototype for ECAL preshower

3 tiles were used for test2 were assembled for cosmic test

Other task: to improve gluing

Not glued

Bicron optical cement

Mono-component optical glue (UV light polymerized)

Epo-Tek 301

1 1.58 1.41 1.68

How it’s important

Does not depend on plastic type

Measurements were done before and after gluing with the same diode

4 grams each timeAccuracy up to 0.01g

Since refractive indexes almost the same we can suppose that difference is due to acid type (groove walls “melting” – more uniform and transparent volume). For our milling process – Epo-Tek 301 is the best.

Cosmic ray test one diode

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nts,

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Threshold, mV

It works!!! We can use only one diode.

Diode noise

“Soft” and “hard” part of cosmic ray

“Soft”

Muons

MuonsPed

Last task: Strips

4 stripes shows some “oscillating” signals. Reason bad 3M mirror contact. All tiles were reassembled. New test will be done about 20 of October.

3M tape

R.M.S ≈ 12%

Conclusion• START detector was adopted for dE/dx measurements• Optimal diameter d=80 mm for tile 100x100x10 mm3

response was found (r.m.s < 5.0 %).• EPO-TEK 301 glue was found as optimal to increase light

yield.• 3 types of FEE board were produced (all commercially

evaluable)• Progress in MRS APD development allows to use only one

diode for readout keeping signal/noise ratio almost the same like for two old diodes

• 4 strips 200x10x5 mm3 were reassembled and will be tested again. Good one has 12% r.m.s.(?)

• Tools for mass production were produced.

Thank you!

BACKUP

MRS APD calibration Ubias for given amplification about 106

Thank to Yuri Musienkofrom CMS APD lab.

Response and leakage tests

All current is due to intrinsic noise, no significant leakage

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SMR

PQN

Difference – small difference in α and coupling with fiber (epoxy layer share)

Noise measurements

Photoionization αDifference – different field noise contribution to the thermal noise

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