Development of scintillation detectors with MRS APD light readout for CBM Muon system and ECAL preshower Alexander Akindinov ITEP(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 -V oper Readout MRS APD structure Single electron resolution is a result of dispersion of U br and C cell across diode area. Slope corresponds to elementary micro-cell capacity Q/ U. M = C*(U - U br ) Q = N cell *C*(U - U br ) Many other name: SiPM, MPPC, GAPD…

Optical trench(CPTA) – low optical coupling between cells. Acceptable noise rate for reasonable thresholds 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 4 th cell threshold noise count about a few kHz High geometrical factor PDE is optimize for WLS fibers P.D.E. = Q.E. * g * R ε g – geometrical fill-factor R – probability to initiate Geiger avalanche Q.E. – quantum efficienc y

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 X150X10 mm 1 groove, 2 rings Y11 and glued Threshold Cosmic μ Signal/noise

First implementation - ALICE CRTF Up to 5 ALICE TOF modules under the test. Bottom plane 10 strips 8 STARTs in each (80 STARTS) Upper plane 10 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 ReasonNumber of diodes ExplanationAction Leakage current increasing up to 20 μA 27Bad insulation between metal and cell for trench technology Informing CPTA, work in progress Zero current4Bad bondingNegligible, 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 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 mm 3 and strips sized 5x200x10 mm 3 Tiles with different groove diameters to find optimal uniformity (d = 90, 80, 70, 60, 50 mm) Strips 5x200x10 mm 3 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 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 V LVDS Amplitude 1 (50 Ω) Jumper 1 for coincidence (on) Jumper 2 for coincidence (on) Threshold Ubias Ubias сontrol Test 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 R.M.S 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 Photonique SA C.P 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 23Vnew N 16 ph.e. Tile 150x150x10 mm 3 N 29 ph.e. N 22 ph.e. 23Vnew Tile 100x100x10 mm 3 Beam test CERN PS (2x2 cm 2 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 mm 3 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 glue 2.Check if we can work with one diode 3.Make prototype for ECAL preshower 3 tiles were used for test 2 were assembled for cosmic test

Other task: to improve gluing Not glued Bicron optical cement Mono-component optical glue (UV light polymerized) Epo-Tek How its important Does not depend on plastic type Measurements were done before and after gluing with the same diode 4 grams each time Accuracy 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 It works!!! We can use only one diode. Diode noise Soft and hard part of cosmic ray Soft Muons Ped

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 mm 3 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 mm 3 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 U bias for given amplification about 10 6 Thank to Yuri Musienko from CMS APD lab.

Response and leakage tests All current is due to intrinsic noise, no significant leakage Difference – small difference in α and coupling with fiber (epoxy layer share)

Noise measurements Photoionization α Difference – different field noise contribution to the thermal noise