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Transcript
Study of the Multi-Pixel Photon Counter for ILC calorimeter Satoru Uozumi (Kobe University) BNM2008 @ Atami • Introduction of ILC and MPPC • The MPPC performance • Calorimeter Prototype with MPPC • Summary The International Linear Collider and ILD • e+e- collider with center-of-mass energy at 500 ~ 1000 GeV. • ILD (International Large Detector) is one of the detector concepts proposed for the ILC experiment. • Various precision measurements expected: – e+e- g H, W, Z, tt, SUSY, etc … g Multi-jets final states. • Particle Flow Algorithm (PFA) allows precise jet-energy measurement . ETOT = pe+ p + pcharged hadron + E + Eneutral hadron [ tracks only] [calorimeter only] • Separation of jet particles in the calorimeter is required for the PFA g Fine granular calorimeter is necessary. The ILC Scintillator-Strip Calorimeter • One approach for the fine granular calorimeter. other approaches : silicon strip cal, digital cal • Sampling calorimeter with W/Pb - scintillator sandwich structure. • Scintillator stirp structure to achieve fine granularity (strip size ~ 1 x 4.5 x 0.2~0.3 cm). • Signal of all the strips are read out individually.. • Therefore the number of channels is huge (~10M for ECAL, ~4M for HCAL). • The calorimeter is placed inside 3 T magnetic field. Need small, cheap, magnetic-field tolerant photon sensor while having high performance comparable with conventinal PMTs. The Multi-Pixel Photon Counter (MPPC) - A Geiger-mode avalanche photo-diode with multi-pixel structure ~ 1 mm Substrate • Belongs to Pixelated Photon Detector family (same as SiPM) • Manufactured by Hamamatsu Photonics. • High Gain (105~106) • Good Photon Detection Efficiency (~15% with 1600 pixel) • Compact (package size ~ a few mm) • Low Cost • Insensitive to magnetic field • Dark noise exists ( ~100 kHz) • Input vs output is non-linear We are developing and studying the 1600-pixel MPPC with Hamamatsu for the ILD calorimeter readout. What are required to the MPPC ? • Gain, Photon Detection Efficiency (P.D.E.) comparable to PMTs. – Gain at least 105 – P.D.E. ~ 20% • Dark noise rate (due to thermal electrons) and inter-pixel cross-talk probability as low as possible. – Dark noise rate < 1 MHz, Cross-talk probability ~ a few per cent. • Uniform performance over many pieces. • Dynamic range enough to measure EM shower max. – Electromagnetic shower is quite dense. – Need dynamic range corresponds to 2000~5000 photoelectrons. • Stability & Robustness. Tolerance to temperature change, long-term use, magnetic field and radiation. • Low cost, compactness. – Price order of $1~5, package size ~ 2 x 2 mm2. • Time resolution ~ 1 ns – Useful for bunch-ID, neutron separation Gain, Dark Noise Rate, Inter-pixel Cross-talk •30oC •25oC •20oC •15oC •10oC •0oC •-20oC • • • • • • • DV0/DT = (56.0±0.1) mV/oC 1600 pixel Over-voltage – C … Pixel capacity – V0 … Breakdown voltage • Gain comparable to conventional PMTs. • Dark noise rate ~100 kHz. • Performance is temperature sensitive. gtemperature control / monitoring is important. • • • • • • • 30 oC 25 oC 20 oC 15 oC 10 oC 0 oC -20 oC 30 oC 25 oC 20 oC 15 oC 10 oC 0 oC -20 oC Gain – 800 pieces Noise Rate (kHz) Piece-by-piece Variation Noise Rate 450 pieces 400 kHz 200 kHz 1 2 3 4 5 Over-voltage (V) • Piece-by-piece variation is acceptably small. g No need for further selection or categorization on massive use ! Just a small tuning of operation voltages is necessary. • Further effort is ongoing by Hamamatsu to make the variation even smaller. Photon Detection Efficiency (PDE) Measured by njecting same light pulse into both MPPC and PMT, and comparing light yield. WLSF LED MPPC PMT 0.5 mm f hole PDEMPPC N pMPPC .e . N PMT p .e . PDEPMT ~ 16 % MPPC 1600 pixel PMT The 1600-pixel MPPC has comparable P.D.E. with normal photomultipliers (15~20%). w Response Curve •If the recovery time is very long, MPPC output is defined only by number of pixels. •However if the recovery time is shorter than input light, dynamic range may be enhanced. 1600 pix Results LED PMT MPPC w = 50 ns 24 ns 1600 8 ns 1600pix Simulation Slow recovery 16 ns 1600 • Linearity of 1600 pixel MPPC is not limited by number of pixels thanks to quick recovery time (~4ns). • No significant influence from changing bias voltage. • Time structure of the light pulse gives large effects in non-linear region. • Knowing time structure of input light is important. Things done / not yet done Performance status Gain 105~106 OK Photon Detection Eff. ~0.2 for 1600 pix. MPPC OK Dark Noise Rate ~ 100 kHz OK Photon counting Great OK Bias voltage ~ 70 V OK Size Compact OK Dynamic range Determined by # of pixels and recovery time underway Cost Expected to be < $10 Negotiating Long-term Stability Unknown To be checked Robustness Unknown, presumably good underway Radiation hardness Concerned underway B field Expected to be Insensitive Looks OK Timing resolution Expected to be 0.1~1 ns To be checked 468 channels In total ECAL Prototype Performance MPPCs (1600 pixels) Tungsten (3.5 mm thick) Scintillator layer The calorimeter with Full MPPC readout + (3 mm thick) e Frame is proven toScintillator work !strip (1-6 GeV) Energy Resolution for e+ (1 x 4.5 x 0.3 cm) WLS fibre Linearity + 1% Summary & Prospects • For the ILC calorimeter readout, study of the MPPC is extensively ongoing collaborating with Hamamatsu. • Measured performance of 1600 pixel MPPC is almost satisfactory for the requirement: – – – – Comparable gain / P.D.E. with photomultipliers. Low noise rate (~100kHz) comparing with SiPMs. Small piece-by-piece variation. Short recovery time enhances the dynamic range for scintillator signal. • The first EM calorimeter prototype with MPPC readout shows good and reasonable performance. • We are still working on further study and improvement. – More number of pixels for more dynamic range. – Need to check long-term stability, robustness, radiation hardness. • The MPPC is a promising device which has lots of excellent features ! The MPPC Line-up Comparing with other Pixelated Photon Detectors (PPD), the MPPC has, • Low dark noise • High sensitivity to blue light • Small device-by-device variation Number of pixels From HPK catalog 100 1600 1 x 1 mm2 Sensor size Nominal Bias Volt. 400 70 10 V 77 10 V Gain (x 105) 24.0 7.5 2.75 Noise Rate (kHz) 400 270 100 Photon Detection Efficiency 65 % 50 % 25 % Temperature dependence (DV0/DT) 50 mV / oC MPPC New Release Timeline (informed at NSS Nov 2007 by Hamamatsu) • 2007 Dec : 3x3 mm2 commercial sample 1x1mm2 SMD small package mechanical sample 2x2, 1x4 Array (3x3mm2) mechanical sample • 2008 Jan : SMD small package commercial samples • 2008 Apr : 3x3 mm2 product release 1x4 array Array commercial samples 2x2 array Backups Recovery Time Measurement Oscilloscope view (with x63 amp) Dt 1600 pixel t (nsec) Black … MPPC output for 1st Laser Green … MPPC output for 2nd Laser Red … Laser + LED Blue … (Laser+LED) – Laser = net response to 2nd laser Ratio of Blue / Green gives recovery fraction. • Recovery time of the 1600-pixel MPPC is measured to be ~ 4 ns. • This number is consistent with RC time constant of a pixel (C ~ 20 fC, R ~ 200 kW, RC ~ 4 ns). Excellent photon counting ability 0,1,2,3,4,5,6,7, . . . Photoelectrons ! 1 photoelectron 2 photoelectrons The MPPC has lots of advantages Photomultiplier MPPC Gain ~106 105~106 Photon Detection Eff. 0.1 ~ 0.2 ~0.2 for 1600 pix. MPPC Response fast fast Photon counting Yes Great Bias voltage ~ 1000 V ~ 70 V Size Small Compact B field Sensitive Insensitive Cost Very expensive ! Not very expensive Dynamic range Good Determined by # of pixels Long-term Stability Good Unknown Robustness decent Unknown, presumably good Noise (fake signal by thermions) Quiet Noisy (order of 100 kHz) The MPPC is a promising photon sensor, and feasible for the GLD Calorimeter readout ! Radiation hardness of MPPC (100 / 400 pixels) Proton irradiation (400 pixel MPPC) Gamma-ray 100 pixel MPPC Neutron 3.3 x 107 n /cm 1 x 1010 n /cm