Reflections on SiPM: CALICE Collaboration Experience

1. Construction of the hadronic calorimeter prototype for ILC (CALICE collaboration)or experience withGeiger mode operating multipixel photodiodes (SiPM)V. Rusinov, ITEP, Moscow Representing the CALICE collaboration10-th INTERNATIONAL CONFERENCEON INSTRUMENTATION FOR COLLIDING BEAM PHYSICSNovosibirsk, February28-March5,2008

2. Contents • scintillator layers creation • main impressions from SiPM • possible further applications • desirable properties for new generation • of SiPM • conclusions V. Rusinov 10-th INTERNATIONAL CONFERENCEON INSTRUMENTATION FOR COLLIDING BEAM PHYSICS Novosibirsk, March 4, 2008

3. 42m 20m pixel h Al R 50 Depletion Region 2 m Substrate Ubias SiPM – common name and the detector from this producer • - Producer: MEPhI-Pulsar • 1×1 mm2, 1156 pixel • Operating voltage:30-70 Volts • More than 12000 SiPMs were studied LED +β-source See yesterday’s talks by D. Renker and Yu. Musienko V. Rusinov 10-th INTERNATIONAL CONFERENCEON INSTRUMENTATION FOR COLLIDING BEAM PHYSICS Novosibirsk, March 4, 2008

4. Scheme of assembling • Detector unit: • - 3×3, 6×6,12×12cm2 • - uniformity • cross-talk • drop between tiles V. Rusinov 10-th INTERNATIONAL CONFERENCEON INSTRUMENTATION FOR COLLIDING BEAM PHYSICS Novosibirsk, March 4, 2008

5. Test bench for SiPM parameter measurement Set up is realized in CAMAC standard It includes: 16 channel computer driven power supply to feed SiPM’s - 5 mV resolution - 110 V max - 100 μA maximal output current 16 channel computer read-out digital voltmeter to monitor - SiPM bias voltage - SiPM current - temperature during test measurement accuracy voltage – 5 mV current – 5 nA temperature – 0.2O 16 channel 12 bit ADC 0.25pC/count sensitivity PC driven generator to produce LED and random triggers and ignite LED PMT to monitor LED light 15 SiPMs can be tested simultaniously Measurements are done at 2 kHz trigger rate LED driver PC driven generator DATA BASE Digital voltmeter Remote control 16 channel power supply Steering program ……. 16 ch 12 bit ADC gate X~100 PMT 16 ch amp Tested SiPMs 16 ch 12 bit ADC A software package was developed to make easy interface between user and hardware, to perform measurements and to save results in data base V. Rusinov 10-th INTERNATIONAL CONFERENCEON INSTRUMENTATION FOR COLLIDING BEAM PHYSICS Novosibirsk, March 4, 2008

6. Picture from PC screen, one of 8 steps of HV tuning. V. Rusinov 10-th INTERNATIONAL CONFERENCEON INSTRUMENTATION FOR COLLIDING BEAM PHYSICS Novosibirsk, March 4, 2008

7. SiPM parameter distributions Result of selection Rejected reason: Gain – 2.8% Noise at ½ pixel – 5.5% Noise at ½ MIP – 22.6% Cross talk – 3.5% Current – 0.5% Current RMS – 1.4% Yield of good SiPM’s > 70% V. Rusinov 10-th INTERNATIONAL CONFERENCEON INSTRUMENTATION FOR COLLIDING BEAM PHYSICS Novosibirsk, March 4, 2008

8. What detector has been used, comparison with other SiPM (See the talk of Yu. Musienko with recent SiPM achievements) Characteristics of SiPM used for CALICE HCAL prototype are far from today's record values But… V. Rusinov 10-th INTERNATIONAL CONFERENCEON INSTRUMENTATION FOR COLLIDING BEAM PHYSICS Novosibirsk, March 4, 2008

9. Do not forget that the work on HCAL prototype for CALICE has been done in 2004-2007; the SiPM’s for it were developed in 2003. At that time HAMAMATSU (MPPC) (which now produce the devices with record parameters) wasn’t manufacturing it at all. • This business growing extremely fast • And more important. The existing SiPM characteristics are • sufficient and furthermore adequate for our goals Let me illustrate it. This is one of our results – light yield distribution from MIP for all tiles. Looking only on mean value (over all three tile sizes) of the LY = 13.5 pixels. What it means? SiPM has 1156 pixels and therefore has limited dynamic range. Having 13.5 pixels per MIP we can measure energy per cell up to ~ 200 MIP. More efficient detector leads to reduction of this range. Thus, we don’t need higher sensitivity SiPM - only for given task, of course V. Rusinov 10-th INTERNATIONAL CONFERENCEON INSTRUMENTATION FOR COLLIDING BEAM PHYSICS Novosibirsk, March 4, 2008

10. random trigger 1p.e. 2p.e. Ped. 3p.e. Noise rate Mean value for SiPM’s used is equal to 2 MHz, and it looks terrible. But the noise drops fast with threshold increase. So, if Threshold=0.5 MIP noise rate=1.8kHZ It leads to 3 noise events from all 8000 channels for 200 nsec gate and with a such threshold we have 93% efficiency of the whole detector The better detectors could give more flexibility in threshold choice and could add few percent in efficiency. But, nevertheless, characteristics of SiPM’s from MEPhI – PULSAR were quite adequate for our goals. And - of course – for some other tasks. V. Rusinov 10-th INTERNATIONAL CONFERENCEON INSTRUMENTATION FOR COLLIDING BEAM PHYSICS Novosibirsk, March 4, 2008

11. Advantages Small size compact and high granulated detector Low operating voltage Fast Large gain, simple electronic Self-calibration possibility Insensitivity to magnetic field Reliability – problems solved Price (?) Limitations Low radiation hardness* Strong voltage (temperature) dependence** Limited dynamic range High noise level Impressions from dealing with SiPM In conclusion of this part. It was really a pleasure to work with MEPhI – PULSAR team: Boris Dolgoshein, Sergey Klemin, Elena Popova and other people, who developed SiPM’s and produced many thousands of them! * Peak resolution up to ~ 1krad protons, 500 krad e (or gamma), 5×1010 fast neutrons/cm2; recovery for some of detectors; necessary to think separately in each case ** d(MIP)/dT=-4.5%/K ; d(MIP)/dV=7%/V the dependence from only one value! V. Rusinov 10-th INTERNATIONAL CONFERENCEON INSTRUMENTATION FOR COLLIDING BEAM PHYSICS Novosibirsk, March 4, 2008

12. Our HCAL prototype is working! The unique granularity allows to separate closest showers Reconstruction algorithm: (V. Morgunov) applied to HCAL only. Clusters grouped according to topology and hit amplitude. Separate: EM and HAD shower components + neutrons (= isolated hits) Event with 2 hadrons after reconstruction. Two showers separated in depth are visible V. Rusinov 10-th INTERNATIONAL CONFERENCEON INSTRUMENTATION FOR COLLIDING BEAM PHYSICS Novosibirsk, March 4, 2008

13. scintillator Detector unit: scintillating tile+ WLS+ SiPM gives possibility to construct HCAL . But for scalable prototype we still search other solutions. Example 1: How to make calorimeter with >106 channels? One of the first possible steps is to read out light directly from tile without WLS • 2 problems right away: • low light • response non-uniformity SiPM glue MC simulation by E. Tarkovsky (ITEP) Result from ITEP proton beam We can equalize the response only by cutting the peak, but the light problem will grow. New detectors are necessary. V. Rusinov 10-th INTERNATIONAL CONFERENCEON INSTRUMENTATION FOR COLLIDING BEAM PHYSICS Novosibirsk, March 4, 2008

14. Example 2. Scintillating strip as detector unit -Time measurements. Trigger counters Strip with WLSF D1 D2 1.2 mm Y11 1 mm BCF 92 Delays t12=t1-t2, t1T=t1-tT, t2T=t2-tT have been measured V. Rusinov 10-th INTERNATIONAL CONFERENCEON INSTRUMENTATION FOR COLLIDING BEAM PHYSICS Novosibirsk, March 4, 2008

15. Example 3. Scintillating strip as detector unit. - Light Yield and Efficiency 1000x40x10 mm3 coated with TiO2 white paint Ø1.2 mm Kuraray Y11 WLS fiber glued into a groove MRS APD + mirror at opposite end 2000x25x10 mm3 2 SiPM’s Strip efficiency and noise vs threshold V. Rusinov 10-th INTERNATIONAL CONFERENCEON INSTRUMENTATION FOR COLLIDING BEAM PHYSICS Novosibirsk, March 4, 2008

16. Activities Direct light reading from tile. Long scintillating strips with WLS: muon detector veto or trigger wall time (or coordinate) measurements Neutrino detector based on scintillating strips and WLS ( ν + p = n + e+) Neutron detector based on scintillator doped with B10 and WLS Gamma detection in liquid Xe Requirements to detector Energy measurement up to hundreds MIP, large dynamic range (>103 pixel), high efficiency in blue light (>20%), low noise (<100 Hz at ½ MIP), larger area, flat packaging. No energy measurement, 102 pixel, small area (1-1.5 mm2), high efficiency in green (>30%), not so strong requirements to noise level. 3.-4. Energy measurement from ½ MIP, 103 pixel, small area (1-1.5 mm2), high efficiency in green (>30%), lowest noise level (to start with low threshold). No energy, 102 pixel, large area (16, 25 mm2), sensitivity to UV, any noise Possible directionsandwhat do we want from SiPM One of main impressions from SiPM – non-universality. New task requires new detectors. V. Rusinov 10-th INTERNATIONAL CONFERENCEON INSTRUMENTATION FOR COLLIDING BEAM PHYSICS Novosibirsk, March 4, 2008

17. 1mm2 green MRS with ε=30% 4 mm2 ------------------------- 25% 4 mm2 blue MRS with ε=25% Noise rate~ 2.5 MHz/mm2 It is clearly seen - various detectors are needed MRS APD from CPTA, Moscow Efficiency - good for different purposes Noise – not so good yet So, we continue to work with producer, hoping to get better and various detectors The cooperation with Russian producers looks perspective due to easy communication and fast response. Important to have a possibility to order what you really need together with a possibility to buy in a good shop (HAMAMATSU) what they have V. Rusinov 10-th INTERNATIONAL CONFERENCEON INSTRUMENTATION FOR COLLIDING BEAM PHYSICS Novosibirsk, March 4, 2008

18. CONCLUSION • The active layers construction for HCAL prototype • was a big and interesting work for our group, the • 8000-channel device was finished last summer • We have obtained an unique experience with • more than 10000 SiPM’s and positive impressions of them • We principally know how to produce HCAL based on unit described (tile – WLS – SiPM) and we are searching other possibilities • We see further possible applications for such kind of • detectors And – thanks to organizers! V. Rusinov 10-th INTERNATIONAL CONFERENCEON INSTRUMENTATION FOR COLLIDING BEAM PHYSICS Novosibirsk, March 4, 2008