Status of photon sensor study at Niigata University -- SiPM and MPPC -- Photon sensor mini workshop 05/9/16 University Niigata University HEP-Lab Sayaka IBA Editha P. Jacosalem (Mindanao-U), Hiroaki Ono, Noriko Nakajima, Hitoshi Miyata

Contents 1. Study at Niigata university 2. SiPM study 1. Signal 2. Sensor signal uniformity dependence 3. MPPC study 1. Signal 2. Laser intensity dependence 3. Sensor signal uniformity dependence 4. Summary and future plan

Fine segmentation scintillator Read out by photon sensor -> Study of photon sensor (by Iba) Scintillator (by Editha-san) 1. Study at Niigata university Present design of GLD Calorimeter We might need smaller segmentation calorimeter  10x40x2mm strip type scinti X, Z-layer strip scinti: 10x200x2mm Tile-layer: 40x40x1mm This granularity will be checked by simulation soon MPPC

2. SiPM Study

SiPM from Russia Wire Bonding 2mm 34x34 =1156pixels 1.2mm K A about 30um Using SiPM for read out Micro Avalanche Photo Diode (APD)  Each pixel in Geiger mode Compact Suitable for WLS fiber readout 34x34=1156 pixels in small area Pixel Size : 30x30um High Gain : ~10 6 Operational at low voltage : 60~70V

YAG Laser Wave length & power: 532nm (10mJ/cm 2 ), 1064nm (20mJ/cm 2 ) Use filter : down to10 -8 Trigger : from Laser system Pulse width : <10nsec Spot size : <2um Precision of laser position : ±2um Output Circuit YAG laser & scan table system Logic Setup

Signal of laser(1064nm, 532nm) 532nm signal is smaller than 1064nm 532nm result has many noise than 1064nm  Rise time : ~10ns  Fall time : ~200ns 1064nm 65.0V 532nm 65.0V 532nm 66.0V 20mV 10mV 50nsec

Laser wave length : 1064nm Sensor bias : 66.5V 49points (7x7points) were measured Deviation (RMS) : ~28% Laser output fluctuation range : ~10% Central part showed higher PH Laser hitting area (3x3=9 pixel) 5x5 pixel area Sensor signal uniformity dependent Fluctuation histogram

Cross sectional view Cross section of X-axis line 4 and Y-axis line 4 Y-axis line 4 X-axis line4 Cutting X-axis line-4 Cutting Y-axis line-4

3. MPPC Study

MPPC from HPK MPPC :Multi Pixels Photon Counter Made by HPK and under development Compact device Works with much lower voltage than PMT (~50V) Suitable for wavelength shifter fiber We have two types of MPPC  100pixels : 10x10pixels  400pixels : 20x20pixels MPPC 400pixels MPPC 100pixels (10x10pixels) ~85um ~100um

Setup Output circuit YAG Laser Logic readout YAG Laser Wave length & power: 532nm (10mJ/cm 2 ), 1064nm (20mJ/cm 2 ) Filter : Laser intensity is down to10 -8 Trigger : from Laser system Pulse width : <10nsec Laser beam minimum spot size : <2um Precision of laser position : ±2um MPPC

Signal Rise time : ~10ns, Fall time : ~500ns + tail From the ADC graph, we calculated the Charge output of 1pixel which is ~ 2.5pc and Gain is ~1.6x10 7 for 100pixels MPPC 10mV 500nsec View from oscilloscope MPPC : 100pixels From ADC signal MPPC : 100pixe ｌ s 0pixel (0photon) 1pixel (1photon) 2pixel (2photon) signal trigger

Laser intensity dependence For getting the best laser intensity corresponding to 1photon injection Measurement conditions  MPPC : 100pixels  Pixel position : center (X=5,Y=6)  Laser hitting area : within the 1pixel  Wavelength : 532nm  Used filter : for laser intensity down to10 -8 We think laser intensity 160 corresponds to 1photon injection, because this value is beginning of max of 1photon and min of 0photon Efficiency of 0pe, 1pe vs. Laser intensity ● : Efficiency of 0photon event ▲ : Efficiency of more than 1photon event Laser intensity 160 for 1photon injection

Pixel signal uniformity in one pixel (Position dependence between two pixels) Checked efficiency between two pixels as uniformity measurement Scanned 7points between two pixels Wavelength : 532nm Sensor bias : 49.0V Efficiency of more than 1photon event becomes minimum at the boundary line between 2pixels Efficiency vs Position ▲ : Efficiency of 0photon event ● : Efficiency of ≧ 1photon event Efficiency = # of 0 or 1photon event / # of All events pixel

Sensor signal uniformity dependent on the pixel locations Injected laser single photon to each pixel and got response Measurement conditions  MPPC : 100pixels  Sensor bias : 49.0V  Laser wavelength : 532nm, Intensity : 160  Laser hitting area is smaller than 1pixel area  Measured points are 50points that are shown as gray area ~30um ~35um Laser hitting area (smaller than 1pixel) ~85um Measured points : 50points (Gray pixels)

Pulse height = 1photon mean value – 0photon mean value Deviation of PH (RMS) : 10% Laser long term fluctuation : ≦ 5% Pulse Height 1photon mean 0photon mean Pulse height vs Pixel position Distribution of the PH # of pixels

Cross sectional view (Central part) Cross section of X-axis (line-5 + line-6) and Y-axis (line-5 + line-6) which are shown in previous slide  Central part of sensor Cutting X-axis line-5▲ + line-6▲ Cutting Y-axis line-5▲ + line-6▲ X-axis line-5 +6 Y-axis line-5+6

Cross sectional view (Edge part) X-axis line Y-axis line-9+10 Cutting X-axis line-9▲ + line-10▲ Cutting Y-axis line-9▲ + line-10▲ Cross section of X-axis (line-9 + line-10) and Y-axis (line-9 + line- 10)  Edge of sensor We can see that pulse height level and deviation look same as previous slide

Position dependence of efficiency Compare efficiencies between 0photon events and more than 1photon events Efficiency = #of 0photon (or ≧ 1photon) event / #of all photon events Edge of sensor shows low signal efficiency Central area of sensor has good efficiency Efficiency : 0photon Efficiency : ≧ 1photon

Intensity dependence at other points Efficiency : 0photon position X=8,Y=9 eff: poor position X=4,Y=3 eff: good position X=5,Y=10 eff: too bad Intensity Eff. Efficiency of more than 1photon event vs. Laser intensity 160 flat region

Efficiency : 0photon position X=8,Y=9 eff: poor position X=4,Y=3 eff: good position X=5,Y=10 eff: too bad Intensity Eff. Pulse height vs. Laser intensity 160 down

4. Summary and future plan SiPM study (position dependence)  PH uniformity was 28%(RMS), while laser fluctuation was 10%  Edge part showed low PH MPPC study (pixel position & intensity dependence)  PH uniformity was 10% (RMS), while laser long term fluctuation was less than 5%  Central part of a sensor had good efficiency while edge part showed inefficiency in the light collection  For poor efficiency pixels, their efficiency don’t increase and PH decreases as intensity increases Future of Niigata study  Try to connect scintillator strip and MPC through Wavelength- shifter fiber and to do beta-ray test  Measure more detail for 400pixels