Studies of Silicon Photomultipliers for the CMS HCAL Upgrade Yu. - - PowerPoint PPT Presentation

Studies of Silicon Photomultipliers for the CMS HCAL Upgrade

• Yu. Musienko1,2, A. Heering2, A. Karneyev1, V. Postoev1
• R. Ruchti2, M. Wayne2

1INR RAS, Moscow 2University of Notre Dame, Notre Dame

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Outline

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• The CMS Hadron calorimeter (HCAL) at the LHC
• Motivation for the photodetector upgrade
• SiPM requirements for the CMS HCAL Upgrade
• SiPM R&D goals and proposed solutions
• HPK and KETEK SiPM performances (developed for the

CMS HCAL project)

• 175 preproduction array results
• Summary for the preproduction array measurements
• Conclusion

CMS Hadron Calorimeter (HCAL)

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HB, HE, HO similar technology: scintillator tiles with Y11 WLS fiber readout, brass (steel for HO) absorber. HPD was selected as the CMS HCAL photodetector. The CMS HCAL photodetector upgrade was proposed after several years of successful operation of the HPDs at the LHC.

Motivation for the HB/HE photo- detector upgrade

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1. SiPMs have better quantum efficiency, higher gain, and better immunity to magnetic fields than HPDs. Since SiPMs operate at relatively low voltages, they do not produce large pulses from high voltage breakdown that mimic energetic showers like HPDs do. These features of the SiPMs together with their low cost and compact size compared to HPDs enable several major changes to the HCAL. 2. Implementation of depth segmentation which has advantages in coping with higher luminosities and compensating for radiation damage to the scintillators. This is made possible by the use of SiPMs. 3. Use of timing to clean up backgrounds, made possible by the extra gain and better signal-to- noise of the SiPMs.

Main CMS HCAL HB/HE SiPM requirements

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• Area: ~Ø3 mm
• PDE(515 nm): > 15%
• Operating voltage: <90 V
• Gain: <700 000
• ENF: <1.3
• Optical X-talk between cells: <20%
• Temperature coefficient: <5%/°C
• Dynamic range: > 20 000 “effective” cells/SiPM
• Cell recovery time: <10 ns
• Dark current (T=24 °C, after 2*1012 n/cm2): <1000 µA
• Fractional Gain*PDE (after 2*1012 n/cm2): >65%
• Neutron sensitivity: low

HO estimated neutron fluence: <1011 n/cm2 HE estimated neutron fluence: ~1011 n/cm2 HB estimated neutron fluence: ~7*1011 n/cm2

> 5 years of R&D to develop SiPMs for the CMS HCAL Phase I Upgrade

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Why it was difficult? High neutron fluences  high dark noise  large size cells (we need them for high PDE!!) are permanently fired  V-VB approaches “0”  significant drop of the SiPM PDE and gain  SiPM has low PDE, gain and it is useless as a photodetector for the calorimetry… To achieve the goal we performed an optimization of the SiPM structure:

• Small cell size (<15 µm)  smaller dark noise generation rate (to avoid cell blocking effects);
• Fast cell recovery (<10ns)  1/(dark count rate)<<cell recovery time  small PDE*Gain

losses

• Improve SiPM’s geometric factor High PDE (>15%)  better S/N ratio after irradiation
• “Thick” epitaxial layer and deep p-n junction  better PDE for green Y11 light  Small gain

(700 000)  less dark current after irradiation

• small “parasitic” (parallel to Rq) capacitance  smaller gain smaller X-talk&afterpulsing

smaller dark current and smaller noise after irradiation

• SiPM electric field engineering  smaller dark noise generation rate, faster noise reduction

with temperature Many different SiPM structures were developed during >5 years of R&D performed by the CMS SiPM group and commercial companies (CPTA, Zecoteck, Hamamatsu, KETEK, FBK …) Below we report the results achieved with the Hamamatsu and the KETEK SiPMs

Progress in PDE for the 15 µm cell pitch HPK and KETEK SiPMs (2011-2014)

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Significant improvement of PDE for the HPK and KETEK developers during 2011-2014 R&D (most of the results were presented at NDIP-14 conference, see talks of A.Heering and Y. Musienko) In June 2015 Hamamtsu was selected by the CMS collaboration as a vendor for the HE HCAL after testing of 175 preproduction arrays

Preproduction Hamamatsu arrays

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Entire order of 175 arrays in ceramic packages protected by 100 micron thick glass windows

Delivered as scheduled on April 1, 2015 175 eight-channel arrays – 1400 channels 70% of arrays with 2.8 mm devices, complement are 3.3 mm

IV curves for all 1400 SiPMs

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IV curve – no light

Dark current within spec A few channels show high dark current below operating voltage – may remove with additional spec at production stage

2.8 mm – 984 channels 3.3 mm – 416 channels

All 1400 channels operational

IV curve – LED illumination

Good uniformity in Vb and at

• perating voltage

Vop = (Vb + 3 volts) After calibration, spread at

• perating voltage will give us

spread in PDE

VB measurements

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Spread in Vb

123 arrays, 984 channels All 2.8 mm diameter devices Overall spread < 1.0 volt, RMS will be smaller

Spread in Vb

52 arrays, 416 channels All 3.3 mm diameter devices Overall spread < 1.0 volt, RMS will be smaller

1/IdI/dV method is used (see talk Y. Musienko et al., NDIP-2014)

Gain*PDE uniformity for 2.8 and 3.3 mm SiPMs

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10 20 30 40 50 60 70 80 0.95 1 1.05 1.1 Frequency Current(dVB=3 V)/Cal. Coeff.

960 SiPMs (Ø2.8 mm)

Mean= 1.00 RMS = 1.13 %

5 10 15 20 25 30 35 0.95 1 1.05 Frequency Current (dVB=3 V)/Cal. Coeff.

320 SiPMs (Ø3.3 mm)

Mean = 1.00 RMS = 0.96 %

Excellent Gain*PDE uniformity: RMS~1%

Gain vs V-VB (T=22 °C)

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Gain is 350k at V - VB= 4 volts, meets the specification

100 200 300 400 500 600 1 2 3 4 5 Gain, 103 V-VB [V] 2.8 mm dia. SiPM 3.3 mm dia. SiPM

Photon Detection Efficiency vs V-VB

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PDE ~ 30% at dVB = 3 Volts, 35% at dVB = 4 volts, exceeds the specification PDE the same within errors for 2.8 mm and 3.3 mm devices

10 20 30 40 50 1 2 3 4 5 6 7 PDE(515 nm) [%] V-VB [V]

2.8 mm dia. SiPM 3.3 mm dia. SiPM

PDE – Spectral response

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5 10 15 20 25 30 35 40 45 350 400 450 500 550 600 650 700 750 800 PDE [%] Wavelength [nm]

T=25 C

dVB=4.0 V

Glass widow with special filter was designed by Hamamatsu for the CMS SiPM arrays to cut UV light which can be produced by muons and hadrons in plastic fibers

Optical Cross Talk

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x-talk from one micro-pixel to another within a single SiPM < 20% at V - Vb = 4 volts, meets the specification Note: x-talk from one device to its neighbor is too small to measure

5 10 15 20 25 30 35 40 45 1 2 3 4 5 6 7 X-talk [%] V-VB [V]

2.8 mm dia. SiPM 3.3 mm dia. SiPM

C vs V measurements

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Two arrays plotted Good uniformity within array Similar behavior for 2.8 mm and 3.3 mm devices Capacitance at operating voltage well within spec

0.0E+00 2.0E-10 4.0E-10 6.0E-10 8.0E-10 1.0E-09 20 40 60 80 Capacitance [F] Bias [V]

2.8&3.3 mm dia. HPK arrays

Ch1 Ch2 Ch3 Ch4 Ch5 Ch6 Ch7 Ch8 Ch9 Ch10 Ch11 Ch12 Ch13 Ch14 Ch15 Ch16

IV dependences (forward bias)

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0.0E+00 5.0E-03 1.0E-02 1.5E-02 2.0E-02 2.5E-02 1 2 Current [A] Bias [V]

2.8 mm dia. SiPMs

ch1 ch2 ch3 ch4 ch5 ch6 ch7 ch8

0.0E+00 5.0E-03 1.0E-02 1.5E-02 2.0E-02 2.5E-02 1 2 Current [A] Bias [V]

3.3 mm dia. SiPMs

ch1 ch2 ch3 ch4 ch5 ch6 ch7 ch8

Used to measure forward resistances  quenching resistances

Forward resistance

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 Rq ~ 900 kOhm (small spread <4% RMS)

Recovery time

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Response to laser pulse for: 2.8 mm devices (above) 3.3 mm devices (below) Recovery time is ~ 7-8 nsec for both, meets specification

• 0.35
• 0.25
• 0.15
• 0.05

0.05 2.0E-08 4.0E-08 6.0E-08 8.0E-08 1.0E-07 Amplitude [V] Time [s]

2.8 mm dia. SiPMs

ch1 ch2 ch3 ch4 ch5 ch6 ch7 ch8

• 0.35
• 0.25
• 0.15
• 0.05

0.05 2.0E-08 4.0E-08 6.0E-08 8.0E-08 1.0E-07 Amplitude [V] Time [s]

3.3 mm dia. SiPMs

ch1 ch2 ch3 ch4 ch5 ch6 ch7 ch8

Accelerated aging and thermal cycling tests

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• Total of 80 channels were operated nonstop at 70o C for a 4 week period
• 24 channels were subjected to temperature cycling between -15o C and

50o C under high humidity – initially with a one hour cycle time, then fast cycling every 15 minutes

• Devices were monitored continuously during these tests
• Before/after measurements of IV curves to assess damage

Stability at high temperature

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10 arrays, 80 channels in continuous operation at 70oC for 4 weeks Vb was increased after two days, correct for temperature effect Stable dark current, no runaways, no failing channels First 2 weeks of data are shown at this slide.

IV curves for dark current after 4 weeks at 70 °C

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IV curves for dark current, before (top) and after (bottom) four weeks of continuous operation at 70o C 80 channels plotted no failures, no increase in dark current (actually a bit quieter!)

Temperature cycling (and humidity) tests

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Temperature cycling between -15oC  +50oC, one hour per cycle, 200 cycles Humidity relatively low and stable 3 arrays, 24 channels tested, all channels monitored Repeated with fast cycles (15 min), higher humidity – devices still stable

IV curves for dark current before/after thermal cycling (with high humidity) tests

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IV curves for dark current, before (top) and after (bottom) three days of fast thermal cycling with high humidity 8 channels plotted no discernible effect observed

Radiation damage studies

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• 4 arrays (32 channels) were

irradiated in the IRRAD facility at CERN with 24 GeV protons

• Dosage was independently

monitored using APDs

• Dosage across each array was

position dependent due to the profile of the beam – this effect is very evident in the data

• Peak dosage of nearly 5E12

neutrons/cm2 (ch# 7)

• Channel 4 dose corresponds

to max expected in HE

Estimated dose per channel number – Array 35

ch# Fluence, n/cm2 1 2.33E+10 2 3.42E+10 3 5.21E+10 4 1.12E+11 5 4.82E+11 6 3.05E+12 7 5.00E+12 8 1.70E+12

IV curves for all 32 channels after irradiation

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• All channels survived
• Correspondence between dark current and dose very evident
• Dark current at expected max dose for HE within specs

Vb of each channel in one array: before (above) and after (below) irradiation

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Shift in Vb of less than 100 mV

Relative amplitude for each channel after irradiation

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Channel 4 dose corresponds to max expected in HE: Gain*PDE change is less then 5%

0.0E+00 5.0E-09 1.0E-08 1.5E-08 2.0E-08 2.5E-08 3.0E-08 2 4 6

Amplitude [a.u.]

V-VB [V]

T=25.3 °C

ch#1 ch#2 ch#3 ch#4 ch#5 ch#6 ch#7 ch#8

Dark current and equivalent noise charge for each channel after irradiation

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Channel 4 dose corresponds to max expected in HE: within spec at V-Vb = 4 volts

1.0E-07 1.0E-06 1.0E-05 1.0E-04 1.0E-03 1.0E-02 1 2 3 4 5 6 7 Dark Current [A] V-VB [V] T=25.3 °C

ch#1 ch#2 ch#3 ch#4 ch#5 ch#6 ch#7 ch#8

1 10 100 1 2 3 4 5 6 ENC [p.e.] V-VB [V] T=25.3 °C (50 ns gate)

ch#1 ch#2 ch#3 ch#4 ch#5 ch#6 ch#7 ch#8

Signal to noise ratio for each channel after irradiation

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S/N vs. dVB is almost flat for 1.5<dVB<4.5 V (peaks at dVB~2.7 V)

1 10 100 1000 1 2 3 4 5 6 Signal/Noise Ratio V-VB [V] T=25.3 °C, Ng~670 photons (515 nm)

ch#1 ch#2 ch#3 ch#4 ch#5 ch#6 ch#7 ch#8

Summary for HPK measurements

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• A number of tests have been performed on a significant

sample of Hamamatsu SiPMs

• The devices meet or exceed the design specifications for all measurements

done thus far

• Spread in breakdown voltage well within 1 volt all devices
• Spreads in gain, PDE are narrow across many devices
• Gain, PDE, x-talk, recovery time, capacitance all meet specs
• Behavior of the 2.8 mm and 3.3 mm are the same within errors
• The devices held up well during high temperature operation and survived fast

thermal cycling under high humidity with no effects

• All devices tested survived radiation, including doses much larger than

expected in HE. Performance after irradiation is within specs.

Conclusion

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As a result of 2011-2014 R&D on SiPMs for the CMS HCAL Upgrade project (performed with KETEK and Hamamatsu) SiPM photon detection efficiency for green light was improved from 10-15% up to 25-30 % for these producers, sensitivity to fast neutrons was significantly reduced, resistance to hadron radiation for all SiPMs was also improved in comparison to the previous SiPM prototypes. In June 2015 Hamamatsu (Japan) was selected as a vendor for the CMS HE HCAL Upgrade:

• Preproduction batch of 175 arrays was delivered right on schedule
• All channels are operational under normal conditions
• Devices meet spec for all measurements performed
• Devices survived accelerated aging and aggressive thermal cycling
• Devices survived irradiation beyond maximum dose expected at HE

1100 SiPM arrays for the CMS HE HCAL Upgrade will be delivered to CERN at the end of 2015 – beginning 2016. Test stands for SiPM quality control, accelerating aging, radiation tests were developed and produced at CERN by the CMS SiPM group (University of Notre Dame and INR RAS). R&D on the SiPMs for the CMS HB HCAL Phase I Upgrade continue until fall of 2016. R&D on SiPMs for the CMS Phase II Calorimeter Upgrade has been started!

Acknowledgments

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This work was supported by the U.S. National Science Foundation and by the Russian Ministry of Education (Russian state grant RFMEFI61014X0004).

Back-up

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HE HCAL specs and measured SiPM parameters

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Spec Value HPK KETEK-I KETEK-II

Cell size [µm]

15 15 15 15

• Sens. area [Ømm]

2.8 2.8 2.8 2.8

Operating temperature [°C]

24 24 24 24

VB [V]

<90 ~65 ~28 ~43

Vop-VB (V)

>2 4.0 4.0 4.0

Dark Current [nA]

<1000 150 300 60

PDE(515 nm) [%]

>25 30 27 33

Gain, x103

<700 350 600 420

Capacitance [pF]

<600 215 525 330

Recovery time [ns]

≤10 10 10 5

Excess Noise Factor

<1.3 1.18 1.14 1.16

Optical Cross-Talk [%]

<20 17 14 15

After-pulses [%]

<5 <2 <2 <2

dVB/dT [mV/°C]

<60 58.5 20.4 35.4

Temperature sensitivity [%/C]

<6 3 0.8 1.5

Voltage sensitivity [%/V]

<60 50 38 48

Neutron noise sensitivity

low low no no

Dark current ( 2*1011 n/cm2 ) [µA]

<500 140 450 215

ENC (50 ns, 2*1011 n/cm2 ) [pe]

<12 8 11 10

Fractional gainXPDE after 2*1011 n/cm2[%]

>95 >95 >95 >95

Laser resp., 10 Ohm (Int=90%, ns)

• 30

62 39

Laser resp., 10 Ohm (Int=95%, ns)

• 41

78 50

Idark(20 °C)/Idark(10 °C)

• 1.86

1.66 1.78

HPK SiPM neutron detection probability (Am-Be n-source)

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1.E-06 1.E-05 1.E-04 1.E-03 1.E-02 1.E-01 20 40 60 Neutron detection probability Electronics threshold [pe]

epo+mixer epo+no-mixer no-epo+quartz+mixer no-epo+mixer no-epo+quartz+paint+mixer no-epo+glass+mixer no-epo+no-mixer no-source-no-epo+quartz+mixer