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The Multi-Pixel Photon Counter for the GLD Calorimeter Readout
Jul-20 2006 LCWS@VancouverSatoru Uozumi
University of Tsukuba, Japan
1. Introduction2. Recent R&D results3. Summary
Contents
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EM-Scintillator-layer model
TT 10Aug05
particles
T-Layer
X-Layer
Z-Layer
4cmx4cmx2mm
1cmx4cmx2mm
1cmx4cmx2mm
MPC R/O with WLSF
MPC R/O with WLSF
MPC R/O with WLSF
absorber plate
• Sampling calorimeter with Pb/W - scintillator sandwich structure with WLSF readout
• Particle Flow Algorithm (PFA) needs particle separation in the calorimeter
• Fine granularity with strip/tile scintillator
• Huge number of readout channels– ~10M (ECAL) + 4M (HCAL) !
– 10k for muon detector
• Used inside 3 Tesla solenoid
Need new photon sensorwhich is compact and low-cost, but has enough performance.
The GLD Calorimeter
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~ 1 mm
Depletion region ~ 2 m
~ 8 m
Substrate
substrate p+
p-
Guard ring n-
Al conductorp+ n+
Si Resistor Vbias
The Multi-Pixel Photon Counter … named by Hamamatsu
(Silicon Photomultiplier … general name)
is a novel type semiconductor photon sensor
We have the MPPCsamples with:• 400 pixels• 1600 pixels
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PMT MPPC
Gain ~106 105~106
Photon Detection Eff. 0.1 ~ 0.2 0.1~ 0.4
Response fast fast
Photon counting Yes Great
Bias voltage ~ 1000 V 30 ~ 70 V
Size Small Compact
B field Sensitive Insensitive
Cost Expensive Low ($1~10?)
Dynamic range Good Determined by # of pixels
Long-term Stability Good Unknown
Robustness decent Unknown, maybe good
Noise (fake signal by thermions)
Quiet Noisy (order of MHz)
The MPPC performance
The MPPC looks feasible for theGLD Calorimeter readout!
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Required performance for the GLD Calorimeter
• Gain: ~ Best to have 106 , at least 105
• Dynamic range: can measure ~1000 p.e.– satisfactory to measure EM shower maximum– need > 2500 pixels
• Photon Detection Efficiency ~ 30 %– to distinguish MIP signal
• Noise rate : ~ 1 MHz (threshold = 0.5 p.e., threshold =1.5 p.e is also acceptable) • good uniformity, small cross-talk• Timing Resolution ~ 1 nsec
– Necessary for bunch ID, slow neutron separation• Sensor area: 1.5 x 1.5 mm
– suitable for 1.5 mm fiber• Should be stable against bias voltage / temperature / time
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• The MPPC performance looks feasible for the GLD calorimeter readout, but still not sufficient.
• Need study and improvement of the fundamental property to achieve our goal.
• Now we are measuring performance of latest 400 / 1600 pixel MPPC prototypes provided by Hamamatsu.
• Based on its results, we provide feedback to Hamamatsu to have improved sample.
R&D Status @ GLD Calorimeter
Evaluate performance of the MPPC prototypes
Provide feedback to HPK
Improved samples from HPK
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Current Results of R&Dwith the 1600 pixel prototype
• Gain• Noise Rate• Microscopic Laser Test
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Gain vs Bias Voltage
400 pixels 1600 pixels
400 pixelwith x63 amp
Green LED MPPC
• Typical Gain ~ 5-12 x 105 (400 pixels),
1.5-3 x 105 (1600 pixels)• Need precise control of bias voltage to
have stable gain
Pedestal
1 p.e signal
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Count rate of dark noises above threshold (>0.5 / 1.5 photoelectrons)
● -20℃● -10℃● 0℃● 10℃● 20℃
threshold=0.5pe thr=1.5pe
1 MHz
2 MHz
Noise (Dark Counting) Rate (1600 pixels)
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Laser Bench Test of 1600 pixel MPPC
MPPC
• YAG Laser ( = 532 m) with microscope
• Pulse width ~ 2 nsec
• Laser spot size ~ 1 m
• Moving stage pos. resolution ~ 0.02m
• Can perform precise pinpoint scan with the well-focused laser
It is important to understand pixel-by-pixel / inside-pixel variation of the performance.
Need of the pin-point light source
The microscopic laser system launched at KEK in Mar 2006
Results are yet preliminary !
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Scan within a pixel- Detection Efficiency -
All
ep
N
N=Eff ..1 Num. of >= 1 pix. fired events
Num. of all events
• Geometrical acceptance within a pixel ~ 20 %• Variation within an active region ~ 7-13%
One pixel
・ -71.0V・ -70.0V・ -69.5V
Vbias = 70 V
・ -71.0V・ -70.0V・ -69.5V
y-po
int
x-point x-point
Eff
.
1600 pixel P
reliminary
Eff.
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Gain (x105)
Scan within a pixel- Gain -
• Center part have higher gain
• Gain Variation inside sensitive region ~ 2-3 %
Gain (x105)
x-point
y
-poi
nt
x-point
y
-poi
nt
1600 pixel P
reliminary
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Summary & Plans• MPPC is a great device, and feasible for the GLD calorimeter re
adout.• Extensive R&D is ongoing collaborating with the Hamamatsu Ph
otonics.• We still have lots of things to do in a short term:
– Need more study of the fundamental properties (Photon Detection Efficiency, Linearity, etc)– Stability, Robustness, B-field tolerance– Time resolution– Device-by-device variation– More test with microscopic laser
• We may have next improved MPPC samples soon from HPK• Current target is a beam test of EM calorimeter prototype with the full MPPC readout (next talk). ~500 MPPCs necessary, we will have them by the end of this ye
ar.
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Backups
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PMT* MCP-PMT*
HPD* APD* MPPC (SiPM)
HV 1kV 1kV 8kV+300V 300V 50V
Gain 106 106 105 102 106
Noize <10Hz <10Hz ?? Very Sensitive
1MHz
B Filed NA OK OK OK OK
Price/channel
$25 $60 --- $30 $10
QE 15% 8% 8% 70% 10~20%
R&D No marginal necessary Marginal necessary
(*) Multi-pixels
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Setup
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-ray test (in 2005)
Scintilltor (10x40x2mm)
• Practical test with Scintillator & WLSF• Compare performance with PMT
Device# of p.e.
detected
# of photons
from fiber
MPPC(100 pix)
6.1±0.7
(pixels)
28±10
PMT 5.8±0.5
(p.e.)
29±6(1mm
MPPC performance is comparable with PMT
for the practical use.
Co60
- ray
MPPCor PMT
Preliminary result