1. Study of Photon Sensors using the Laser System ACFA2005@Daegu,Korea 05/7/12 Niigata University, Japan Sayaka Iba, Editha P. Jacosalem, Hiroaki Ono, Noriko Nakajima, Hitoshi Miyata GLD Calorimeter Group

2. Contents 1. Introduction 2. Outline of new photon sensor – MPC 3. Setup of MPC measurement using laser system 4. Voltage dependence of signal and noise 5. Laser intensity dependence of signal 6. Pixel signal uniformity in one pixel 7. Sensor signal uniformity dependent on the pixel location 8. Summary 9. Future Plan

3. Fine segmentation scintillator Read out by photon sensor -> Study of photon sensor 1. Introduction Present design of GLD Calorimeter We might need smaller segmentation calorimeter  10x40x2mm strip type scintillator X, Z-layer strip scintillator : 10x200x2mm Tile-layer : 40x40x1mm This granularity will be checked by simulation soon

4. 2. New photon sensor --MPC-- MPC :Multi pixels Photon Counter Made by Hamamatsu Photonics and under development Each pixel is in Geiger mode and as a whole pixels they worked in avalanche mode Compact device Works with much lower voltage than PMT Suitable for wavelength shifter fiber We have two types of MPC  100pixels : 10x10pixels  400pixels : 20x20pixels MPC 400pixels MPC 100pixels (10x10pixels) ~85um ~100um

5. 3. Setup of MPC measurement using laser system 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 MPC

6. Signal From the ADC graph, we calculated the Charge output of 1pixel which is ~ 2.5pc and Gain is ~10 7 for 100pixels MPC 10mV 500nsec View from oscilloscope MPC : 100pixels From ADC signal MPC : 100pixe ｌ s 0pixel (0photon) 1pixel (1photon) 2pixel (2photon) signal trigger

7. 4. Sensor bias dep. of 1pixel PH at 532nm Below 48.6V of 100pixels, signal was low rate Above 49.4V of 100pixels and above 50.6V of 400pixels, there were long tail of signal and exceeds the gate width (Gate full width: 1us) The laser light covered all pixels (100pixels) 100pixels400pixels 48.4V 49.6V 48.5V51.0V PH

8. Noise level Noise level = Sensor bias dependent of Pedestal sigma 100pixels 400pixels We wanted to know the best operation voltage, so we used Noise level and S/N for above-mentioned condition 100pixels : Noise level rapidly increases as bias voltage increases 400pixels : Noise increase is more gently than that of 100pixels 48.4V 49.6V 48.5V51.0V 303 σσ

9. S/N 100pixels: S/N peak was ~49.0V as the best operation voltage 400pixels: S/N peak was above 50.5V. But it had long signal tail exceeding the gate width. So we decided to use the lower voltage (50.3V) as the best operation voltage 400pixels operation voltage is higher than that of 100pixels and also operation voltage range is wider than that of 100pixels S/N = Pulse Height / Pedestal sigma 100pixels highest region much tail 49.0V 48.4V 49.6V 400pixels flat region much tail 50.3V 48.5V 51.0V S/N

10. 5. Laser intensity dependence For getting the best laser intensity corresponding to 1photon injection Measurement conditions  MPC : 100pixels  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 # of event (0pe, 1pe) vs. Laser intensity ● : # of 0photon event ▲ : # of more than 1photon event Laser intensity 160 for 1photon injection

11. 6. 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

12. 7. Sensor signal uniformity dependent on the pixel locations Injected laser single photon to each pixel and got response Measurement conditions  MPC : 100pixels  Sensor bias : 49.0V  Laser wavelength : 532nm  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)

13. 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

14. 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

15. Cross sectional view (Edge part) X-axis line-9 +10 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

16. 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

17. 8. Summary We measured two types of Hamamatsu MPC which are under development; 100pixels and 400pixels Bias voltage dependence of PH, noise level and S/N were measured  Good operation voltage was 49.0V for 100pixels and 50.3V for 400pixels  Operation voltage range of 100pixels is smaller than that of 400pixels Position dependence of PH, number of photons were measured with 532nm laser for 100pixels MPC  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

18. 9. Future plan Try to connect scintillator strip and MPC through Wavelength-shifter fiber and to do beta-ray test Measure more detail for 400pixels  Position dependence  Intensity dependence etc. Supply our test results to Hamamatsu Photonics for further improvement Thank you very much for listening ! Setup of connection scintillator and MPC MPC