Pixilated Photon Detectors
and possible uses at ILC and SLHC
WSU, 23 Oct 09
Rubinov “at” fnal.gov 23 Nov 09 1Rubinov, WSU HEP seminar
Intro to SiPM Q: What is an SiPM?
A: SiPM (Silicon Photo Multiplier)
23 Nov 09 Rubinov, WSU HEP seminar
MRS-APD (Metal Resistive Semiconductor APD)SPM (Silicon Photo Multiplier)MPGM APD (Multi Pixel Geiger-mode APD)AMPD (Avalanche Micro-pixel Photo Diode)SSPM (Solid State Photo Multiplier) GM-APD (Geiger Mode APD)SPAD (Singe Photon Avalanche Diode)MPPC (Multi Pixel Photon Counter)
FromYamamoto
Pixelated Photon Detector
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-- T. Nakaya (Kyoto) @ Pixel08 --
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Photodiodes:
• p-n junction , reverse bias• Electron-hole pair generated by an incoming
photon drifts to the edges of the depleted region• I(t) = QE * q * dN/dt(t)• Absolute calibration• No gain • Suitable for large signals
From A Para (Fermilab)
23 Nov 09 Rubinov, WSU HEP seminar
Photodiodes, Avalanche, Geiger Mode
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Photodiodes, Avalanche, Geiger Mode
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Avalanche Photodiodes:• Photodiodes operating at higher bias voltage• Higher voltage stronger electric field higher energy of drifting
carriers impact ionization Gain • (Im)Balance between the number of carriers leaving the depletion
region and the number generated carriers per unit time: dNleave/dt > dNgenerated/dt
• Stochastic process: signal quenches when the ‘last’ electron/hole fails to ionize.
• Large fluctuations of the multiplication process Gain fluctuations Excess noise factor (beyond-Poisson fluctuations)
From A Para (Fermilab)
23 Nov 09 Rubinov, WSU HEP seminar 4
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Geiger Mode Avalanche Photodiodes:• Avalanche Photodiodes operated at the
elevated bias voltage. • Larger field carriers gain kinetic energy
faster shorter mean free path• Breakdown voltage: nothing really breaks
down, but dNleave/dt = dNgenerated/dt (on average) at this voltage
• Some electrons can generate self-sustaining avalanche (current limited eventually by the series resistance)
• Probability of the avalanche generation increases with bias voltage (electric field)
• Operation mode: one photon (sometimes) ~1e6 electron avalanche
From A Para (Fermilab)
23 Nov 09 Rubinov, WSU HEP seminar
Photodiodes, Avalanche, Geiger Mode
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First prototype of MAPD (MRS APD 1989)
First metall-resistor-semiconductor APD (MRS APD) structure was designed by A.Gasanov, V.Golovin, Z.Sadygov (russian patent #1702881, from 10/11/1989)
Low-light intensity spectrum of MRS APD (A. Akindinov et. al, NIM387 (1997) 231
PDE of MRS APD is just few %
Anfim
ov N
ikola
y,
Dubna,
JIN
R
23 Nov 09 6Rubinov, WSU HEP seminar
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Q=CD*(Vbias-Vbd)
23 Nov 09 Rubinov, WSU HEP seminar 9
Intro to SiPMs Analogy
When comparing PMTs to SiPMs, SiPMs enthusiast usually list advantages of SiPMs
BORING and PREDICTABLE
I list advantages of conventional PMTs on next slide from a tube company
23 Nov 09 Rubinov, WSU HEP seminar 10
PMT vs SiPMAdapted from IEEE & Eric Barbour
Tubes: Advantages 1. Characteristics highly independent of temperature.
2. Wider dynamic range, due to higher operating voltages.
3. Very low dark current.
SiPM: Disadvantages 1. Device parameters vary considerably with temperature,
complicating biasing.
2. May need cooling, because lower operating temperature may be required.
23 Nov 09 Rubinov, WSU HEP seminar 11
Analogy?I think we have seen
transition from vacuum tubes to solid state before.
Transistors are not tiny vacuum tubes and SiPMs are not tiny PMTs
23 Nov 09 Rubinov, WSU HEP seminar
I think that the reason we have transistors instead of tubes boils down to this:
$
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Is the SiPM the perfect LLL sensor?
• Die eierlegende Woll-Milch-Sau (german) (approximate english translation: all-in-one device suitable for every purpose)
23 Nov 09 Rubinov, WSU HEP seminar
R. Mirzoyan
There will be different devices optimized for different applications
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SiPM Animal Research in SiPMs is very active, in many
different directions – I’m not going to do a survey Extended blue sensitivity (Cherenkov light, dual
readout calorimetry) Increased PDE ( muon detectors) Reduced crosstalk (improved noise factor) Improved timing (PET) Large area (Cherenkov) Increased dynamic range (Calorimeters) LOWER COST (everyone)
23 Nov 09 Rubinov, WSU HEP seminar 14
Areas of interest for LHC Issues of special interest to SLHC
(more detail on CMS specifics later)
Radiation hardness
Dynamic range/Linearity
Stability (radiation, temperature and time)
CERN has a strong, active community working on all these issues
23 Nov 09 Rubinov, WSU HEP seminar 15
Areas of interest for LC Issues of special interest to LC
(more detail on SiD specifics later)
Blue sensitivity
Cost/unit area
Optical coupling to detector
Calice is a strong collaboration doing fantastic work on these areas
23 Nov 09 Rubinov, WSU HEP seminar 16
Understanding SiPM operation
Here I'm going to focus on 2 issues DC measurements
Vb determination Rquench determination Cross talk measurement
Pulse measurements Afterpulsing measurements
23 Nov 09 Rubinov, WSU HEP seminar 17
DC Measurements
Static characteristics - IV curves at fixed temperatures: Keithley 2400 sourcemeter Temperature controlled chamber Labview data acquisition program
Forward bias series (quenching) resistance Reverse bias breakdown voltage, integral
behaviour of the detector s a function of the operating temperature
1823 Nov 09 Rubinov, WSU HEP seminar 18
Forward Bias Scan
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Exponential growth with V
Limited by quenching resistor
dI/dV = 1/R
Resistance decreases with temperature(polysilicone)
23 Nov 09 Rubinov, WSU HEP seminar 19
Quenching Resistance Summary for MPPCs
Detector type
Quenching Resistor @ 25 oC, k
dR/dTk/oC
1/R dR/dT
25 200 2.23 0.011
50 105 1.08 0.010
100 85 0.91 0.011
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From A Para (Fermilab)
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Reverse Bias Scan
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100 pA
1 V above breakdownI~5x10-7AGain ~ 4x106
‘Photodiode’ currentlevel ~ 10-13 AHow relevant is the current below the breakdown voltage?
1 V above breakdownI~5x10-7AGain ~ 4x106
‘Photodiode’ currentlevel ~ 10-13 AHow relevant is the current below the breakdown voltage?
Quenching resistance
Temperature
Breakdown
From A Para (Fermilab)
23 Nov 09 Rubinov, WSU HEP seminar 21
Vbd(T). Preliminary analysis
23 Nov 09 Rubinov, WSU HEP seminar
y = 0.0002x2 + 0.0482x + 29.168
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-50 -40 -30 -20 -10 0 10 20 30 40 50
T (C)
Vb
d (
V)
IRST #30Fermilab
August 29th 2008
Diego Cauz
University & INFN of Udine
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Cross Talk Measurement
Single avalanche rate
Single + 1 cross talk
Single +2 cross talk
Single +3 cross talk
Ratios of rates give relative probabilities of 1,2,3 extra pixels firing due to cross-talk
23 Nov 09 Rubinov, WSU HEP seminar 23
Cross Talk Rates as a Function of Bias Voltage
• Cross talk probability increases with the bias voltage
• Cross talk probability is bigger for larger size pixels
But… The cross talk is mediated by infrared photons produced in the avalanche, hence is ought to be proportional to the gain. And different size pixel detectors have different gain !
23 Nov 09 Rubinov, WSU HEP seminar 24
Cross Talk Probability as a Function of Gain
• At the same gain the cross-talk probability is much larger for smaller size pixels
• At the operating point the Hamamatsu detectors have very small cross talk (~few %)
23 Nov 09 Rubinov, WSU HEP seminar 25
Pulse measurements
23 Nov 09 Rubinov, WSU HEP seminar
MPPC-11-050C#37 at 71.1deg F operating at 69.81 (recommended V is 70.02 at 25C)
Current reading is 0.044uA
1pe is about 13.25mV
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A little bit about after pulses
Observed signal grows with the bias voltage. This growth has several components:• increase of the gain• increase of afterpulsing.The latter is a much bigger effect. So what?? Afterpulses provide a kind of additional gain. True, but this contribution fluctuates degrades the charge measurement resolution (excess noise factor).
Relative width of the observed pulse height spectrum slightly decreases with bias voltage for 10 nsec gate (presumably a reflection of the increased number of detected photons), but it increases for longer gates.
Bottom plot shows a contribution to resolution from fluctuations of the afterpulses contribution in different gates. 23 Nov 09 Rubinov, WSU HEP seminar 27
Detector Recovery / Afterpulsing
Pulse arrival distribution: clear afterpulsing for about~ 1 sec
At least two components: 1=39 nsec
2=202 nsec
These components probably correspond to traps with different lifetimes
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F. Retiere @ NDIP08
Ph
oto
-Ele
ctro
ns
Time after the first pulse (ns)
S10262-11-050CS10262-11-050C
Time after the first pulse (ns)
short~15ns
long~85ns
Dark-noise rate
23 Nov 09 29Rubinov, WSU HEP seminar
After subtracting the effects of cross-talk + after pulse, the dark noise is found to be linear to V.
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F. Retiere @ NDIP08
23 Nov 09 30Rubinov, WSU HEP seminar
SiPM pulse shape
Actually, there is some subtle issues in measuring pulse shape
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The idea is to model the avalanche as a fast, brief (almost) short across a capacitor (Cdet) which is then recharged through a resistor (Rq)
this is one micro pixel, so 1 pe by definition
Also include parasitic capacitance across this resistor (Crq)
Also model the rest of the device by a collection of Cdetp, Rqp, Crqp the parallel stuff is important, it gives that characteristic “kink”
This kink
There are 4 values of Crq from 1 to 10 fF. So Crq is important for “spike” but not “tail”
is this
plus this
and this is what we are left with... So the size of the “spike” makes a huge difference to the shape
of what is observed- including the integral
Crq= 10fF, 5fF, 2.5fF, 1fF
But, the slow component is not so affected
This fig has 8 plots: before and after the filter for each value of Crq
But its even worse than that...
The details of the assumed filter make a big difference as well
I picked this very gentle, 6db stop band filter to prevent this...
... how about we lower the HiFreq cutoff and concentrate on the shape of the falling edge. Lets say cut at 100MegHz
So that corresponds to digitizing at 200MSPS
For this run, I dropped the Crq=10fF curve
These are 5fF, 2.5fF and 1fF curves
recall that Cdet is 3fF for this MPPC 025u
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Simulation vs reality
Time
0.98us 1.00us 1.02us 1.04us 1.06us 1.08us 1.10us 1.12us 1.14us 1.16us 1.18usV(BPASS1:out)
-10mV
0V
10mV
20mV
30mV
40mV
50mV
60mV
70mV
Using SiPMs
23 Nov 09 Rubinov, WSU HEP seminar
Until you have spread your wings, you will have no idea how far you can walk despair.com
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CMS
Two approaches Straight replacement of the HPD
Coupling individual fibers to individual SiPMs:Electrical Decoder Unit
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CMS
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Linearity number of cells is the issue
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Radiation is an issue
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EDU
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The EDU 100% compatible with existing mechanics/optics
CMSEither of these could use fantastic new devices from Zecotek
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MAPD-1 with surface pixels (p-type substrate) 556 pixels*mm-2
MAPD-3N with deep microwells (n-type substrate) 15 000 pixels*mm-2
PDE = QE· eg· Ptr Ptr=Ptr(V)
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MAPDs main characteristicsA
nfim
ov N
ikola
y,
Dubna,
JIN
R
ILC- SiD
For SiD there are two possible uses of SiPM HCAL : 3x3 cm cells directly coupled to SiPMs Tail catcher/Muon system with scintilator strips
and WLS fibers coupled to SiPMs
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Scint HCAL for SiD
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The key issue here is coupling of the scintillator to SiPMNorthern Illinois University has some very clever and pioneering work on this(basic idea is to put a dimple in the center of the cell)
We have made an Integrated Readout Layer board for tests of these cells
SiD muon system
For SiD muon system there are 3 main issues1. Cost2. Cost3. Cost
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Our setupDetail of optical coupling and
adopter board
using Keithley 2400 for bias
(not shown)
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MTest 2008
Beam from Nov10 to 16Minerva test of TOF counters
Added one bar with SiPM for testing (Ham, IRST)
Using NIM based 6ch amp built at Fermilab for this work
Using optical coupling designed at Notre Dame
Using 120 GeV proton beam (1in x 1in spot)
Very preliminary results below
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Single PE signals
Scope traces5mv/div
using LED
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Ham-100 during beam spillNotice the Y scale is 100mv/div!
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IRST SiPM with 1.8m sint in 120Gev Beam at 34V, I=1.1uANotice the Y scale is 100mv/div!
Summary of test beam If you have enough photons, SiPMs will
make PERFECT muon detectors. So the questions are:
Size of scintillation strip and WLS fiber diameter(cost)
Length of strip and WLS fiber (cost) Area of the SiPM (coupling the fiber to the SiPM)
(cost) Electronics to readout the SiPM – does not drive
the cost
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Conclusion
We are on a cusp of a revolution in Low Light Level photo detectors.
The only questions is are we going to be manning the barricades
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The Future
I have seen the future of SiPM readout
Readout electronics will be integrated into the SiPM!
because SiPM is an inherently digital device We ALWAYS convert the signal from the SiPM to digital So why do we have an analog step in between?!?
0pe
1pe
2pe
ADC
0pe
1pe
2pe
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The Future
Ingredients required for integrated readout
1. SiPM is CMOS compatibleRMD makes SiPMs through Mosis
2. Will work for in HEP applicationsPixel architectures have demonstrated
readout of arrays like this
3. Cost effective(in volume)
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So why DIGITAL-ANALOG-DIGITAL?
Because this requires an ASIC The people who make SiPMs do not know what we
want The people who know what we want do not make
SiPMs (yet)
Application Specific IC has to have a specific application
Because it gives us the most flexibility
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Back from the future
Our current strategy is to maximize flexibility which is the opposite of what we eventually want
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Next step(s): 4ch board Still very generic, but now think infrastructure Best available commercial components without
heroic efforts (~1ns resolution, ~400 pe range) Integrated with SiPM specific features
(bias generator, current readback, temp sensor) Optimized for medium ch count (dozen(s) SiPMs) Flexible: using 50ohm input, generic daughter
board connection to support faster readout/more memory
Large FPGA to allow DSP and TDC features
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Next step(s)
Still very generic, but now think infrastructure
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Still very generic, but now think infrastructure
CW bias generator
bias offset/ch
hi res current readback/ch
2 stages of diff amps
12bit, 250MSPS ADCs
largish FPGA
simple USB interface
daughter brd for faster interface
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Still very generic, but now think infrastructure
CW bias generator
bias offset/ch
hi res current readback/ch
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Near future
Move from more generic to more specific
Develop a simple ASIC
Optimize for 100s of SiPMs
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