Transcript Document

Selection of Silicon Photomultipliers for ILC
Analogue Hadron Calorimeter Prototype
New Photon Detectors Workshop PD07
University of Kobe, June 27-29, 2007
E.Tarkovsky (ITEP Moscow),
Lay-out
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in the frame of CALICE collaboration
ILC Hadron Calorimeter prototype with SiPM readout
Selection criteria of photodetectors
Experimental set-up for SiPM test
Result of selection
Other useful applications
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Results reported in this talk have been obtained in
the frame of construction of hadron calorimeter
prototype for ILC
The physics goals forward requirement of excellent
energy resolution for such a calorimeter (~30%/√E)
which may be reached using PFLOW. This results in
obligatory high granularity in both longitudinal and
transversal directions.
The cubic meter prototype currently built by
CALICE collaboration has 38 planes of 5 mm thick
scintillators interleaved with 20 mm thick steel
absorbers.
Detecting plane with 216 tiles
The total number of scintillators in the
prototype is 7608.
Adding detectors for TCMT and spare
ones - overall amount ~ 9000 pcs
PD07 workshop University of Kobe June 27-29, 2007
E.Tarkovsky, ITEP, Moscow
We have chosen for prototype construction
novel solid state photo detectors – Silicon
PMs. This is a matrix of tiny photo diodes –
”pixels” working in Geiger mode and connected
to a common bus. Because of big amount of
pixels the output signal is equal to the sum of
standard signals of individual pixels and is
proportional to the number of photons
impinging the SiPM area.
The recent test of “minical” – prototype with
11 planes (99 tiles read out with silicon
photomultipliers) at DESY positron beam in 1-6
GeV/c momentum range showed that SiPM is
an adequate photo-detector for the
calorimetry.
The measured response linearity, energy
resolution, longitudinal and transversal shower
distributions are in good agreement with
Monte Carlo calculations.
Main features of SiPM’s
like ordinary vacuum phototubes they have
high gain and PDE
•high gain ~106
•PDE ~10-20% in green part of spectrum
•they are not sensetive to magnetic field
•SiPM operation voltage is low (30-80 V)
•match to WLS fiber readout by size and
spectral sensitivity
•small size ~10 mm3
Some drawbacks:
•high noise – may reach ~MHz at 1/2 pe level
•limited dynamic range ~1000 pe
•inter pixel cross talk
PD07 workshop University of Kobe June 27-29, 2007
E.Tarkovsky, ITEP, Moscow
We have been using for 1 m3 prototype SiPM’s manufactured by MEPhI-PULSAR
collaboration These devices have 34x34 pixel matrix at 1.12 mm2 area
Thanks to extremely small size of a photo-detector we have it incorporated in a
scintillator without noticeable loss of efficiency.
PD07 workshop University of Kobe June 27-29, 2007
E.Tarkovsky, ITEP, Moscow
The flow chart of photodetector selection
As SiPM is a non linear device it is very convenient to have all photo detectors
equalized by response expressed in pixels. We have chosen value for response
to MIP to be equal 15 pixels.
This choice is a compromise between requirements to have high (>95%) efficiency
to MIP at ~ 1/2 MIP threshold and from other hand requirement to have
dynamic range as wide as possible.
1. Tune Vbias for each SiPM to have response of 15 pixels
2. At chosen voltage measure main SiPM parameters:
- Gain (G),
- Cross talk (xt)
- Noise at 1/2 pe level (F0)
- Current and its stability (I and RMSI)
- Noise at the ½ MIP level (F1/2MIP)
- Response curve in the ~0.3 - 200 MIP range
PD07 workshop University of Kobe June 27-29, 2007
E.Tarkovsky, ITEP, Moscow
3. Apply selection criteria
- G > 4*105 in 140 ns gate -> 1MIP ~ 1pC
- F0 < 3 MHz
- I < 2 μA
- RMSI < 20 nA
- F1/2MIP < 3 kHz
- xt < 0.35
- Response(light~200 MIPs) > 900 pixels
- Minimal gain is chosen from requirement to eliminate noise of FE electronics
above ½ MIP threshold.
- 3 kHz limit at F1/2MIP – number of noise hits in an event is of order of 1 per 8000
channels
- Limits at xt and F0 correspond to limits at F1/2MIP, requirements of high MIP
efficiency and wide dynamic range
4. Keep SiPM’s at elevated (+3.5 V) voltage during at least 40 hours. This allows to detect
those devices which due to technological defects have discharge between the common bus
and pixel area.
5. Repeat measurement of SiPM parameters to confirm that SiPM parameters have not
been changed.
PD07 workshop University of Kobe June 27-29, 2007
E.Tarkovsky, ITEP, Moscow
Test bench for SiPM parameter measurement
Set up is realized in CAMAC standard
LED
driver
It includes:
PC driven
generator
16 channel computer driven power supply
to feed SiPM’s
- 5 mV resolution
- 110 V max
- 100 μA maximal output current
16 channel computer read-out digital
voltmeter to monitor
- SiPM bias voltage
- SiPM current
- temperature during test
measurement accuracy
voltage
– 5 mV
current
– 5 nA
temperature – 0.2O
DATA
Digital voltmeter
BASE
Remote control
16 channel
power supply
Steering
program
…….
16 ch
X~100
PMT
12 bit
gate
PC driven generator to produce LED and
random triggers and ignite LED
ADC
Tested SiPMs
16 channel 12 bit ADC 0.25pC/count
sensitivity
16 ch amp
16 ch
12 bit
ADC
PMT to monitor LED light
15 SiPMs can be tested simultaniously
Measurements are done at 2 kHz trigger
rate
A software package was developed to make easy interface between user and hardware, to
perform measurements and to save results in data base
PD07 workshop University of Kobe June 27-29, 2007
E.Tarkovsky, ITEP, Moscow
Extraction of SiPM parameters from LED and random spectra
F0 and F1/2MIP are extracted from random
trigger spectrum
-ln(N0/Ntot)
N>1/2MIP
F0 =
F1/2MIP =
Tgate
Ntot*T gate
Fit of LED spectrum with Poisson distribution
distorted by cross talk gives values of G, xt, Npe
Response to MIP, pixel
Choice of operation Vbias
Bias voltage, V
For each value of bias voltage
the number of pixels per MIP
is calculated and operating
bias voltage is found from
the fit of response points by
a power function
pix/MIP = A * ( V - Vbd )B
and requirement Npix/MIP=15
At chosen bias voltage the saturation curve of a SiPM is
measured in light range ~0.3-200 MIPs as well as SiPM
current and its stability
PD07 workshop University of Kobe June 27-29, 2007
E.Tarkovsky, ITEP, Moscow
SiPM parameter distributions
Result of selection
Rejected :
Gain – 2.8%
Noise at ½ pixel – 5.5%
Noise at ½ MIP – 22.6%
Cross talk – 3.5%
Current – 0.5%
Current RMS – 1.4%
Yield of good SiPM’s > 70%
PD07 workshop University of Kobe June 27-29, 2007
E.Tarkovsky, ITEP, Moscow
Accuracy of parameter measurement
R M S / m e a n ,
%
Multiple measurement of the same
SiPMs in the same test bench channels
allows to estimate statistical errors in
determination of parameters which are
subject to selection cuts:
Operational bias voltage ~0.1%
Number of pixels per MIP ~1.5%
Noise ~2%
Gain ~ 2%
SiPM current ~2.5%
Cross talk ~3%
C h a n n e l
n u m b e r
PD07 workshop University of Kobe June 27-29, 2007
Noise at ½ MIP level ~20%
for limit F0 the accuracy is higher –
1./√(3*103*2*10-7*3.5*105)=7%
E.Tarkovsky, ITEP, Moscow
From measurements of parameters at various bias voltages it is possible
to derive value of of parameter variation at 100 mV Vbias variation
One has to know what stability of bias voltage and temperature has to be kept in order to
have SiPM parameters stable at necessary level, for example in order to have gain stable at
1% level one needs to keep bias voltage with accuracy 30 mV.
PD07 workshop University of Kobe June 27-29, 2007
E.Tarkovsky, ITEP, Moscow
Long term stability of measurements
Measurements of SiPM parameters and determination of operational bias voltage have
been repeated many times (~100) during almost 2 years with set of 15 SiPM’s. Analysis
of these data shows the stability of the set up and gives opportunity to study the
temperature dependence of main SiPM parameters as temperature was not stable
during measurements.
Operational bias V vs temperature
Deviation of operational bias V from fit
RMS=
0.052 V
Temperature factor of Vb
mean=0.057 V/oC
RMS=0.008 V/oC
PD07 workshop University of Kobe June 27-29, 2007
E.Tarkovsky, ITEP, Moscow
Temperature dependence of SiPM noise (F0)
mean=12.9oC
RMS=0.9oC
F0 temperature factor, oC
F0 = A * exp( T / T0 )
T0 = (12.9 ± 0.2)oC
PD07 workshop University of Kobe June 27-29, 2007
E.Tarkovsky, ITEP, Moscow
Temperature dependence of SiPM noise at ½ MIP (F1/2MIP)
mean=6.1oC
RMS=0.6oC
F1/2MIP temperature factor, oC
F1/2MIP = B * exp( T/ T1/2MIP )
T1/2MIP = (6.1 ± 0.2)oC
PD07 workshop University of Kobe June 27-29, 2007
E.Tarkovsky, ITEP, Moscow
Comparison of parameters of multi pixel Geiger mode photo-detectors
New photodetectors manufactured by
Hamamatsu Corp. recently became
available. We have done the comparative
test of such MPPCs with Russian MRS
APD from CPTA enterprise with ~550
pixels/mm2 and SiPMs from MEPhIPULSAR collaboration.
Designed to work in blue region of spectrum
MPPC have 2-3 times more PDE in blue light.
MRS APD with 2x2mm2 area has PDE close to
MPPC.
At green light PDE of MPPC and MRS APD
are close to each other (15-25%).
Gain of 1600 pixel MPPC is more than twice
less than gain of SiPM and MRS APD.
MPPC1600 and MRS APD have rather low
cross talk – less than 0.2
MPPC400 has larger efficiency and gain but
larger cross talk
PD07 workshop University of Kobe June 27-29, 2007
E.Tarkovsky, ITEP, Moscow
Comparison of noise at level ½ pixel
shows that noise frequency of single
samples of 1600 pixel and 400 pixel
MPPCs is smaller by at least one
order of magnitude.
PD07 workshop University of Kobe June 27-29, 2007
E.Tarkovsky, ITEP, Moscow
Test of radiation hardness of Geiger mode multi pixel photon
detectors with Co60.
Dose rate ~330 kRad/hour
 energy – continuous spectrum up to 1.33 MeV
All devices except one are operational
after 800krad
but with increased dark current and
deteriorated single photoelectron
resolution
For most of tested devices the increase
of current is seen to be proportional to
accumulated dose:
ΔI ~(1-3)μA / 500 kRad
But 1600 pixel MPPC shows several times
worse proportionality: current increased
up to 14 μA after the first 200 kRad and
up to 60 μA after the second 200 kRad
PD07 workshop University of Kobe June 27-29, 2007
E.Tarkovsky, ITEP, Moscow
Current of 1600 pixel MPPC (after 200 kRad+200 kRad) vs annealing time
200 kRad
200 kRad
1600 pixel MPPC shows big annealing after doses of 200 kRad, the current is not constant
even after several hours after bias voltage is on
PD07 workshop University of Kobe June 27-29, 2007
E.Tarkovsky, ITEP, Moscow
After the first irradiation pedestal is very broad and individual pixels are not seen
Situation improves with time and is better for smaller Vbias
Only one sample was tested
and it is too early to make
conclusions
More studies are necessary
with reasonable dose rate
PD07 workshop University of Kobe June 27-29, 2007
E.Tarkovsky, ITEP, Moscow
Conclusions
• We have tested and made selection of more than 9000 SiPMs for prototypes of
hadron calorimeter and tail catcher for future linear collider experiments
• The computerized LED test bench for SiPM test and selection was designed,
constructed and used for measurements at ITEP
• Parameters of selected SiPMs meet requirements from the physical performance
• Variation of SiPM parameters at variable bias voltage and temperature have been
measured
• Comparison of various multi pixel Geiger mode photo detectors has been done
• This work was supported by ISTC grant # 3090
PD07 workshop University of Kobe June 27-29, 2007
E.Tarkovsky, ITEP, Moscow
Backup slides