Performance of 1600-pixel MPPC for the GLD Calorimeter Readout Jan. 30(Tue.) Korea-Japan Joint Shinshu Univ. Takashi Maeda （ Univ. of Tsukuba) for the GLD Calorimeter Group

1600-pixel MPPC Guard ring Si Resistor The Multi-Pixel Photon Counter (MPPC) … Novel photon sensor that used for GLD calorimeter readout

The Multi-Pixel Photon Counter (MPPC)  Old Sample  Can package  20 improved samples in last October and 400 samples in last December.  Very compact plastic package for Beam DESY 4 mm 1.3 mm 3 mm 1 x 1 mm ---Improved Point--- Higher Gain Lower Noise rate Package becomes compact etc …

Pulse Shape 1 p.e. 2 p.e.

Measurement of Basic Characteristics  Evaluate 1600-pixel MPPC performance as a function of Bias Voltage and Temperature –Gain, Noise rate, Cross-talk, P.D.E. Set up Thermostatic chamber Blue LEDMPPC

30 o C 25 o C 20 o C 15 o C 10 o C 0 o C -20 o C Gain S : ADC Sensitivity = 0.25 pC/ADCcount A : Amp gain = 63 e : electron charge = 1.6 x C C : Pixel Capacitance V 0 : Breakdown voltage d Pedestal peak 1 p.e. peak 2 p.e. peak

V 0 with Temperature Variation  V 0 is linear to temperature –  V = V Bias – V 0 (T) is sensitive to temperature –Most of MPPC performances are affected by temperature change  Must be improved  V 0 /  T = (56.0 ± 0.1) mV/ o C C : Pixel Capacitance V 0 : Breakdown voltage

Noise Rate  Dark noise : Avalanche amplification by thermal electron Noise rate is lower in lower  V( = V bias – V 0 ) and temperature 30 o C 25 o C 20 o C 15 o C 10 o C 0 o C -20 o C Threshold 0.5 p.e. 0.5 p.e. Threshold 1.5 p.e. Threshold

Cross-talk Probability  Cross-talk : The cross-talk to adjacent pixels is caused by photons created in an avalanche.  2 pixels fired signals in dark noises are caused by cross-talk  Cross-talk probability is not sensitive to temperature change 30 o C 25 o C 20 o C 15 o C 10 o C 0 o C -20 o C

Photon Detection Efficiency (P.D.E)  Q.E. : e - h + pair production probability for single photon injection ( Quantum Efficiency )   Geiger : Avalanche amplification probability from single p.e.   geom : Fraction of sensitive region in a sensor ( Geometrical Efficiency) Measurement method  Compare # of p.e. of MPPC with # of p.e. of PMT (Reference) MPPC 0.5 mm  Pin-hole PMT LED WLSF ~ 16 % ~ Detection probability for single photon injection

Photon Detection Efficiency 6.3 % uncertainty comes from estimation of PMT’s P.D.E ~ 6.3 % P.D.E. of PMT

Summary  We are evaluating 1600-pixel MPPC characteristic for the GLD calorimeter readout  Gain, Noise rate are sufficient for our requirement  Breakdown voltage is sensitive to temperature change –Have to monitor the temperature  Photon Detection Efficiency is higher than PMT Plans  Response curve (Input light-yield vs. Output signal)  Evaluate Uniformity in the sensor  Measure long-term stability  Figure out radiation damage effect and magnetic field stability

Back up …

Old sample results - Gain 30 o C 25 o C 20 o C 15 o C 10 o C 0 o C -20 o C a = (5.67 ± 0.03) x10 -2 V/ o C b = 66.2 ± 0.1 V V 0 =aT+b

Old sample results – Noise rate V bias – V 0 (T) [V] 30 o C 25 o C 20 o C 15 o C 10 o C 0 o C -20 o C

Old sample results – Cross-talk  Cross-talk probability looks stable with temperature in V bias – V 0 < 2.5V. The cross-talk to adjacent pixels is caused by photons created in an avalanche. Cross-talk probability is measured from dark noise rates : ・ 30 ℃ ・ 25 ℃ ・ 20 ℃ ・ 15 ℃ ・ 10 ℃ ・ 0 ℃ ・ - 20 ℃ V bias – V 0 (T) [V]

Set up Gate Generator Delay Voltage source HV PMT MPPC Stage WLSF Green LED AMP *63 Signal input Gate PC Thermo-static chamber Clock Generator Voltage source

Light yeild measurement ( with noise and cross-talk subtraction)  Measure light yeild of LED light pulse  Fit ADC distributon  Supposed signals are dominated by Poisson statistics  Count number of events below 0.5 p.e. threshold ( both LED on and off ) pedestal Events 0.5 p.e. threshold pedestal Events

Calculation of Np.e.  f(0,μ LED on) = f(0, μ+μ noise ) = f(0,μ) × f(0,μ noise ) f(0,μ) = f(0,μ LED on) / f(0,μ noise ) = e -μ μ = -ln( f(0,μ) ) f(n,μ) is Poisson distribution function μ is Expectated number of Np.e. f(0,μ LED on ), f(0,μ LED off ) are probability of 0 p.e. f(0,μ noise ) = N LED off / N LED off = e -μnoise f(0,μ LED on ) = N LED on / N LED on =e -μLED on pedestal all pedestal all

Npe MPPC / Npe PMT (Npe ratio)

WLS Fiber Y-11 Reference : JLC ストリップ・ファイバー電磁カロリメータの性能研究 Katsumi Sekiguchi March. 2003

QE of H1161GS

Mean of QE for 1 p.e. QE × relative light yeild on each wave length ∑ （ QE × relative light yeild on each wave length ） = Mean of QE for 1 p.e. ~16.7 %

Response / Correction curves ( with small cross-talk ) Response curve Correction curve R -1 (p;N fired ) p=0.1 R (p;N pe ) p=0.1 (no cross-talk) p=0