Pixilated Photon Detectors and possible uses at ILC and SLHC WSU, 23 Oct 09 Rubinov “at”...

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

2

-- 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)


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)


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




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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)


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


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.


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


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)


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)


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


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


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


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


Forward Bias Scan

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Exponential growth with V

Limited by quenching resistor

dI/dV = 1/R

Resistance decreases with temperature(polysilicone)


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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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



Vbd(T). Preliminary analysis


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


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 !


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 %)


Pulse measurements


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


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


SiPM pulse shape

Actually, there is some subtle issues in measuring pulse shape


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


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


CMS


Linearity number of cells is the issue


Radiation is an issue

23 Nov 09 44

EDU


The EDU 100% compatible with existing mechanics/optics

CMSEither of these could use fantastic new devices from Zecotek


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

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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


Scint HCAL for SiD


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


Our setupDetail of optical coupling and

adopter board

using Keithley 2400 for bias

(not shown)


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


Single PE signals

Scope traces5mv/div

using LED


Ham-100 during beam spillNotice the Y scale is 100mv/div!



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


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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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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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

Pixilated Photon Detectors and possible uses at ILC and SLHC WSU, 23 Oct 09 Rubinov “at”...

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