1. Avalanche Micro-Pixel Photo-Diodes for Frontier Detector Systems, GSI, 9-10 February 2009 1

2.  DASIPM2 Collaboration  PET Application  SiPM matrices read-out systems  SiPM matrices performance  Conclusions Avalanche Micro-Pixel Photo-Diodes for Frontier Detector Systems, GSI, 9-10 February 2009 2

3.  R&D Experiment funded by INFN – NSC5  Development and Optimization of SiPM matrices and arrays for different applications: › PET, Calorimetry and Fiber optic tracking in HEP, Astroparticle Physics  Pisa, Bari, Bologna, Perugia, Trento with FBK-irst  Spokesman: Prof. Alberto Del Guerra, University and INFN Pisa Avalanche Micro-Pixel Photo-Diodes for Frontier Detector Systems, GSI, 9-10 February 2009 3

4.  Different geometry, size, microcell size and GF  Matrices 16 elements (4x4)  Matrices 64(8 x 8) pixels, C. Piemonte, FBK-irst, talk IV CURVES OF 9 MATRICES. VERY UNIFORM BREAKDOWN POINT 4 mm 40x40μm => GF 44% 50x50 μm => GF 50% 100x100 μm => GF 76% circular (1mm diam) 1x1mm 2x2mm 3x3mm (3600 cells) 4x4mm (6400 cells) Avalanche Micro-Pixel Photo-Diodes for Frontier Detector Systems, GSI, 9-10 February 2009 4

5. 4-head rotating tomograph (same concept as YAP(S)-PET) Ring tomograph to be inserted in a magnet bore of an MR system. GEANT4: Spatial resolution of 0.76 mm FWHM for a 18 F point source in the center of the FOV employing filtered backprojection. A high resolution small animal PET scanner with continuous LYSO crystals and silicon photomultiplier matrices as photodetectors is under development at the INFN Pisa. Avalanche Micro-Pixel Photo-Diodes for Frontier Detector Systems, GSI, 9-10 February 2009 5

6.  Framework: development of a SiPM based PET system demonstrator based on › Matrices of SiPM pixels (FBK-irst) › Final target  8 x 8 ; Currently available  4 x 4 › Front-End ASIC with trigger and digitization capabilities (Politecnico di Bari) › Final target  64 channel ; Currently available  1 channel  Meanwhile, readout of SiPM matrices employing different systems: › Readout system from LAL-Orsay (MAROC2 ASIC). › Readout system for PET applications employing the VA-TA ASICs from gamma medica-IDEAS Avalanche Micro-Pixel Photo-Diodes for Frontier Detector Systems, GSI, 9-10 February 2009 6

7.  ASIC that preserves the high dynamic range and excellent timing properties of the SiPMs  Main features: › Input Current buffer: BW = 250MHz; › Fine tuning of the input voltage (SiPM bias voltage) › Variable gain integrator (slow channel for energy measurement): Selectable by 2 bits ( 1V/pC; 0.5V/pC; 0.33V/pC); › Current discriminator (fast channel for timing) › Variable threshold › Final version w 64 channels:  Peak detector  Fast OR for triggering  Analog MUX Avalanche Micro-Pixel Photo-Diodes for Frontier Detector Systems, GSI, 9-10 February 2009 7

8.  AMS 0.35µm CMOS technology  Size: 190µm x 590µm  Total power consumption 6.6mW Avalanche Micro-Pixel Photo-Diodes for Frontier Detector Systems, GSI, 9-10 February 2009 8

9.  Tests with a pulsed LED  SiPM at 32.5V Gain of integrator. Jitter: sigma=30 ps C. Marzocca et al.IEEE-NSS2008, N30-12. Wed 10:30 Experimental results from an Analog Front-End Channel for Silicon Photomultiplier Detectors Avalanche Micro-Pixel Photo-Diodes for Frontier Detector Systems, GSI, 9-10 February 2009 9

10. Structure: n + -p-  -p + optimized for blue light: Shallow n + layer + specific antireflective coating. Each pixel: 625 (25 x 25) microcells, 40  m x 40  m size. Polysilicon quenching resistor. Fill factor 44%. Composed of 16 (4x4) pixel elements in a common substrate 1 mm pixels in 1.06 mm pitch 4 mm 1 mm Bonded SiPM arraySiPM arraySiPM pixel Avalanche Micro-Pixel Photo-Diodes for Frontier Detector Systems, GSI, 9-10 February 2009 10

11.  Full characterization of first run performed at LAL, Orsay.  Excellent uniformity. › Breakdown voltage 30.5V ;  var = 0.5% › Gain @33V 1.46x10 6  var  4%  Mean dark rate @33V (  V=2.5V): 1.98 MHz  PDE @ 33V 8-10% from 420 to 680 nm wavelength. N. Dinu et al. Pixel 2008 workshop, Fermilab, September 2008. Expected PDE >15% for the results shown here (run II and  V=4V) Avalanche Micro-Pixel Photo-Diodes for Frontier Detector Systems, GSI, 9-10 February 2009 11

12.  Developed at Laboratoire de l'Accelerateur Lineaire, Orsay.  64 channels (only 16 used)  low noise preamplifier w variable gain (6 bits)  Slow shaper (~20-150 ns, adjustable)  Fast shaper (15 ns) + 3 discriminators =>Trigger signal.  Designed for MAPMT – not optimized for SiPMs, but allows us to make the tests satisfactorily. Avalanche Micro-Pixel Photo-Diodes for Frontier Detector Systems, GSI, 9-10 February 2009 12

13.  Altera FPGA  USB Port  ADC on the board.  ASIC calibration input.  LabVIEW software for data acquisition Avalanche Micro-Pixel Photo-Diodes for Frontier Detector Systems, GSI, 9-10 February 2009 13

14.  Results with pixilated crystals › Results matrix + crystal array  Results with continuous crystals › Results matrix + slab  Position determination G. Llosa et al., IEEE- MIC2008, paper M02-1 Avalanche Micro-Pixel Photo-Diodes for Frontier Detector Systems, GSI, 9-10 February 2009 14

15. Holder for precise positioning: Error < 50  m. LYSO crystal array: 16 (4x4) crystals of 0.96 mm x 0.96 mm x 10 mm separated by 100  m of white epoxy resin. One-to-one coupling to the SiPM matrix 4 mm Avalanche Micro-Pixel Photo-Diodes for Frontier Detector Systems, GSI, 9-10 February 2009 15

16. NO AMPLIFIER ● Matrix + crystal array -Na-22 spectra from one/all SiPM pixels ● Measurements in coincidence with single SiPM+crystal 1x1x10mm 3 ● Overvoltage  V=2V MAROC2 ALL CHANNELS  variation in peak position variation  =4.4% at  V=2V.  Correcting: data all channels in a single spectrum. Avalanche Micro-Pixel Photo-Diodes for Frontier Detector Systems, GSI, 9-10 February 2009 16

17.  Theory: Post, Schiff Phys. Rev. 80 p.1113 (1950) Double threshold setup: High thres to select photopeak events and avoid time walk. Low thres to measure the time difference N – number of photons  – decay time of scintillator Q – trigger level Avalanche Micro-Pixel Photo-Diodes for Frontier Detector Systems, GSI, 9-10 February 2009 17

18.  In coincidence with single SiPM+1x1x10mm crystal  MAROC2 single threshold. Trigger one channelOR of all channels peak  1.4 ns  +tail peak  1.3 ns peak  ps peak  ps  +tail Low threshold (Compton) High threshold (photopeak)  900 ps  1300 ps Avalanche Micro-Pixel Photo-Diodes for Frontier Detector Systems, GSI, 9-10 February 2009 18

19.  Matrix + white slab: LYSO 4 mm x 4 mm x 5 mm wrapped with white teflon tape.  Na-22 spectrum summing signals from all channels for each event.  DAQ with MAROC2 4 mm  V=4V SPECTRUM WITH PMT SPECTRUM WITH SiPM 4 mm x 4 mm SPECTRUM WITH SiPM MATRIX + MAROC2 Fill factor 44% Fill factor 50% Avalanche Micro-Pixel Photo-Diodes for Frontier Detector Systems, GSI, 9-10 February 2009 19

20.  Coincidence with a 2 nd detector: 1 mm x 1 mm x 1 mm crystal coupled to a SiPM  Source close to the matrix, far from 2 nd detector  Move together source and 2 nd detector. 30 mm 2 mm Avalanche Micro-Pixel Photo-Diodes for Frontier Detector Systems, GSI, 9-10 February 2009 20

21. Avalanche Micro-Pixel Photo-Diodes for Frontier Detector Systems, GSI, 9-10 February 2009 21

22. Hitmap for different source positions with crystal array + 0.5 mm + 1.5 mm + 1 mm + 2 mm Avalanche Micro-Pixel Photo-Diodes for Frontier Detector Systems, GSI, 9-10 February 2009 22

23. VERY PRELIMINARY Avalanche Micro-Pixel Photo-Diodes for Frontier Detector Systems, GSI, 9-10 February 2009 23

24.  Matrix + LYSO crystal 4mmx4mmx5mm painted black  Center of gravity algorithm – problems at the edges  Difficulties due to the small size of the devices  More precise measurements and analysis to be done. VERY PRELIMINARY TO BE IMPROVED... Avalanche Micro-Pixel Photo-Diodes for Frontier Detector Systems, GSI, 9-10 February 2009 24

25. › Detectors: SiPM matrices (4x4) developed at IRST-FBK › Front-End ASIC: IDEAS VA32_HDR11 (Peaking Time = 1usec) › Trigger ASIC: IDEAS TA32CG2 › High Voltage RC (П or T configuration) Filter › A/D Converter: Analog Device AD7677 (16-bit, Tc = 1usec) › Board Controller: Altera Stratix II (Active Serial configuration): › USB Interface controller: Cypress CY7C68013 › DC/DC converters & Low Noise Regulators › Bias network based on digital potentiometers (Dallas DS1267) › Level Translators based on quad line receivers (Dallas DS26C32) › Connectors for Micro Coaxial Cables (2 x 17) G. Magazzu et al. IEEE-NSS2008, N52-1. An FPGA based DAQ System for the Readout of SiPM Arrays in PET applications. Avalanche Micro-Pixel Photo-Diodes for Frontier Detector Systems, GSI, 9-10 February 2009 25

26. HVF Bias Block LTFPGAUSBI SiPM HVF SiPM HVF SiPM HVF SiPM VA TA ADC DA TADA VAADC Avalanche Micro-Pixel Photo-Diodes for Frontier Detector Systems, GSI, 9-10 February 2009 26

27. Connectors for micro-coaxial cables SiPM arraysVA & TA ASICs Bias NetworkADCs Level translators Altera FPGACypress USB uC DC/DC converters DASIPM0 floorplan and building blocks Avalanche Micro-Pixel Photo-Diodes for Frontier Detector Systems, GSI, 9-10 February 2009 27

28.  Voltage steps (different amplitudes) have been applied to the VA calibration input through a 47nF capacitor with the calibration enabled in different channels (output of the S/H circuit connected to the VA differential output)  An external trigger (synchronous with the calibration step) has been used  The ADC input voltages (yellow and magenta) and their difference (brown) are shown in the left plot and the ADC output in the right plot (32 consecutive acquisitions on the same channel for each trigger, calibration enabled for the second and for the third trigger only) Peaking time = 1usec Avalanche Micro-Pixel Photo-Diodes for Frontier Detector Systems, GSI, 9-10 February 2009 28

29.  A LED (1 KHz) has been used used to excite the array of 4x4 SiPM pixels under test (only 8 channels bonded)  An external trigger (synchronous with the LED) excitation has been used  The ADC input voltages (yellow and magenta) and their difference (brown) are shown in the left plot and the ADC output (for a different event) in the right plot Un-bonded channels Bonded channels Avalanche Micro-Pixel Photo-Diodes for Frontier Detector Systems, GSI, 9-10 February 2009 29

30.  Coincidence events triggerd by means of an external signal  Coincidence window 7.5ns  Internal Clock 192 MHz. Avalanche Micro-Pixel Photo-Diodes for Frontier Detector Systems, GSI, 9-10 February 2009 30

31. FPGA Memory USB port FE HPTDC (?) Bias NetworkPower 8×8 SiPM arrays + 64 channel FE (1 × ASIC_BARI) = SIPM1 Avalanche Micro-Pixel Photo-Diodes for Frontier Detector Systems, GSI, 9-10 February 2009 31

32.  A very high resolution PET tomograph for small animals employing SiPMs as photodetectors is under development at the INFN Pisa. A spatial resolution better than 1 mm FWHM is expected.  FBK-irst has developed SiPM matrices with 16 SiPM pixels in a common substrate. The first results obtained are very good. SiPM matrices with 64 pixels have been produced  The first tests towards the PET scanner construction are ongoing with good results. Tests with both pixilated and continuous crystals have been performed.  A first prototype with two rotating heads is under construction employing slabs. Avalanche Micro-Pixel Photo-Diodes for Frontier Detector Systems, GSI, 9-10 February 2009 32

33.  Matrices with 64 (8x8) pixels have been produced  First test prototype under construction › 2 rotating heads › Pixellated crystals and slabs  Dedicated ASIC for SiPMs › 8channel version is being produced  DAQ for 64 channels matrix read-out, architecture is being defined Avalanche Micro-Pixel Photo-Diodes for Frontier Detector Systems, GSI, 9-10 February 2009 33

34.  Energy spectra 57 Co(122keV) 22 Na(511keV) Saturation! Estimated Number of photons detected by SiPM = 900 while N microcells =650 ● Good resolution for gamma spectroscopy (Comparable with standard solid state detectors) ● Saturation with small diode for 511keV peak (higher dynamic range is required) Avalanche Micro-Pixel Photo-Diodes for Frontier Detector Systems, GSI, 9-10 February 2009 34

35. SiPM energy calibration with 1x1x10mm LSO crystal coupled to 1x1 SiPM SiPM 40x40 µm & SiPM 50x50 µm Results of the fit in agreement with SiPM parameters 10% di errore nella posizione del picco di 511 keV se si considera lineare Se il SiPM ha una curva di saturazione che segue la statistica Poissoniana: Avalanche Micro-Pixel Photo-Diodes for Frontier Detector Systems, GSI, 9-10 February 2009 35

36. Avalanche Micro-Pixel Photo-Diodes for Frontier Detector Systems, GSI, 9-10 February 2009 36

37.  Single SiPM FBK-irst 1 mm x 1 mm – 625 microcells (40  m microcell size) + LYSO crystal 1mm x 1mm x 10 mm.  DAQ with a QDC CAEN V795  SiPM follows the response curve linear if Avalanche Micro-Pixel Photo-Diodes for Frontier Detector Systems, GSI, 9-10 February 2009 37

38.  Summary results timing › SiPMs 1mm x 1mm with crystal 1mm x 1mm x 10mm › SiPMs 3mm x 3mm with crystal 2mm x 2mm x 10mm Avalanche Micro-Pixel Photo-Diodes for Frontier Detector Systems, GSI, 9-10 February 2009 38

39. Single SiPM IRST 4mm x 4mm – 6400 microcells ( 50  m microcell size) + white slab: LYSO crystal 4mm x 4mm x 5mm white teflon Energy resolution 15% FWHM assuming negligible saturation effects at 511 keV  V=2.5V Avalanche Micro-Pixel Photo-Diodes for Frontier Detector Systems, GSI, 9-10 February 2009 39

40.  Matrix + white slab in coincidence with single SiPM+1x1x10 mm crystal (double threshold).  MAROC2 single threshold. peak  1.4 ns  +tail peak  1.8 ns Avalanche Micro-Pixel Photo-Diodes for Frontier Detector Systems, GSI, 9-10 February 2009 40

41. one-to-one coupling Hit position given by pixel number Avalanche Micro-Pixel Photo-Diodes for Frontier Detector Systems, GSI, 9-10 February 2009 41

42.  When a trigger is generated in the TA ASIC (or received through a dedicated LEMO connector) the coincidence condition between triggers associated to the two detectors is evaluated (if the coincidence detection is enabled).  In case of a detected coincidence (if the coincidence detection is enabled) or in case of a simple trigger, SiPM data are sampled and hold in the VA ASIC, serially downloaded and converted in a 16-bit ADC.  Conversion results are read by the FPGA where they can be pre-processed and then stored (2 Memory Banks, 256 x 16-bits each) together with information as event number, time stamp and error flags.  At “run time” the memory banks are continuously polled and when one of them is full it is downloaded using the USB fast read mode. Avalanche Micro-Pixel Photo-Diodes for Frontier Detector Systems, GSI, 9-10 February 2009 42

43.  32 input channels (each SiPM channel is connected to two VA input pads to increase the dynamic range)  Nominal peaking time: 0.9us (adjustable in the range 0.8us  1.2us)  Dynamic range: -35pC  25pC  Pre-Amp outputs available on output pads to be connected to input pads of the associated TA ASIC  Calibration input that can drive any pre-amp associated (the corresponding S/H circuit drives the differential analog output ) VA ASIC architectureVA ASIC layout Avalanche Micro-Pixel Photo-Diodes for Frontier Detector Systems, GSI, 9-10 February 2009 43

44.  32 input channels (each connected to one output of the associated VA ASIC)  Optional input gain stage followed by a fast CR-RC (75ns) shaper and by a level- sensitive discriminator with threshold adjustable through an individual 3-bit DAC  Wired-or connection among trigger signals to drive the TA trigger output  32-bit mask to disable trigger from noisy channels can be routed to any input gain-stage  Test input that can be routed to any input gain-stage TA ASIC architectureTA ASIC layout Avalanche Micro-Pixel Photo-Diodes for Frontier Detector Systems, GSI, 9-10 February 2009 44

45.  Circular SiPMs  Application to FAST scintillator: 1 bar of Bicron BC400 4x4x200mm3 equipped with 2 1mm diam wavelength shifting fiber  Test SiPM readout coupling each fiber to a SiPM Avalanche Micro-Pixel Photo-Diodes for Frontier Detector Systems, GSI, 9-10 February 2009 45