Study of Photon Sensors using the Laser System

ACFA2005@Daegu,Korea05/7/12

Niigata University, JapanSayaka Iba, Editha P. Jacosalem, Hiroaki Ono,

Noriko Nakajima, Hitoshi MiyataGLD Calorimeter Group

Contents

1. Introduction

2. Outline of new photon sensor – MPC3. Setup of MPC measurement using laser system

4. Voltage dependence of signal and noise5. Laser intensity dependence of signal6. Pixel signal uniformity in one pixel7. Sensor signal uniformity dependent on the pixel

location

8. Summary9. Future Plan

Fine segmentation scintillatorRead 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 : 40x40x1mmThis granularity will be checked by simulation soon

2. New photon sensor --MPC-- MPC :Multi pixels Photon Counter Made by Hamamatsu Photonics a

nd 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

3. Setup of MPC measurement using laser system

Output circuit

YAG LaserLogic readout

YAG Laser Wave length & power: 532nm (10mJ/cm2), 1064nm (20mJ/cm2) Filter : Laser intensity is down to10-8

Trigger : from Laser systemPulse width : <10nsecLaser beam minimum spot size : <2um Precision of laser position : ±2um

MPC

MPC

Signal

From the ADC graph, we calculated the Charge output of 1pixel which is ~ 2.5pc and Gain is ~107 for 100pixels MPC

10mV

500nsec

View from oscilloscopeMPC : 100pixels

From ADC signalMPC : 100pixe ｌ s

0pixel (0photon)

1pixel (1photon)

2pixel (2photon)

signal

trigger

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)

100pixels 400pixels

48.4V 49.6V 48.5V 51.0V

PH PH

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 48.5V 51.0V

30 3

σ σ

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

highestregion

much tail

49.0V

48.4V 49.6V

400pixels

flat region

much tail

50.3V48.5V 51.0V

S/N S/N

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 160for 1photon injection

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 pixel

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)

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-axisline-5 +6

Y-axisline-5+6

Cross sectional view (Edge part)

X-axisline-9 +10

Y-axisline-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≧

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 40

0pixels Operation voltage range of 100pixels is smaller than that of 400pi

xels

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 sho

wed inefficiency in the light collection

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 connectionscintillator and MPC

MPC