CTA report 152:

Comparison of photon detection performanceof photomultiplier tube and silicon
photomultiplier for Medium Sized Telescopes
Anatolii Zenin, Hiroyasu Tajima, Akira Okumura,
Yuki Nakamura

ISEE, Nagoya University

Outline
Introduction• CTA and Cherenkov imaging• Motivation• PMT and SiPM
• Medium-sized telescope
Main Partand• Setupanalysis technique• Measurement results• Discussion
2

CTA and atmospheric
Cherenkov imaging

Very-high-energy
Gamma Ray
(20 GeV –300 TeV)Electromagnetic Cascade

LST:
20 GeV ~ 150 GeV

Cherenkov Photons

MST:
150 GeV ~ 5 TeVSST:
5 TeV ~ 300 TeV

K. Bernlöhr

3

Motivation
Advantages of SiPM:• Background-tolerant, no degradation over time
• Stable quantum eﬃciency and photon detection eﬃciency• Can be operated with 60V• Lightweight, compact

4

To ensure that theperformance of SiPM
cameras will not be inferior
to the current PMT cameras,
we have to compare:• QE / PDE• Sensitivity to signal• Sensitivity to noisearb. unit

PMT and SiPM
54.5

CTA PMT QECTA SiPM PDE

43.5
32.5

100 GeV γ
Cherenkov
spectrum21.5• High NSB (moonlight)

tolerance and performance
under high NSB conditions• Overall telescope

performance (the end goalof this work)

1

La Palma
NSB spectrum

0.5
0200300

400500600

700
wavelength, nm

PMT and SiPM sensitivity comparison(not to scale)5Medium-sized telescope
Cutoﬀ angle
26˚≤αc≤28˚(technical requirement)

αc

ROBAST simulation of MST optical system

6

Measurement setup

PMT on a rotation stage
Readout module (TARGET)
on a rotation stage

7

Analysis technique
PMT charge spectrum sample

SiPM chargesample
365spectrum
nmnoiseh_spec1
Entries39900
Mean

15.31

Entries

Std Dev18.79

108004Signal + dark countOnly dark count7006001031025004003001020010010−40−20020406080
Integral Value (ns × mV)

Poisson distribution:kP (k) =<latexit sha1_base64="oeIIB7kHc47mJxUDmVkUPZ7sMuE=">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</latexit>k!

e−2000200400600800100012001400 1600
Charge (mV × ns)

Crosstalk does not aﬀect
0pe peaks in SiPM

Can extract mean value from pedestal:=ln P (0)<latexit sha1_base64="zWnPk8B8mEXbQb2nXx/pjxwn5fk=">AAAB/nicdVDLSsNAFJ3UV62vqLhyM1iEujAkpdB2IRTduKxgH9CEMplM2qGTSZiZCCUU/BU3LhRx63e482+cphVU9MDA4ZxzuXeOnzAqlW1/GIWV1bX1jeJmaWt7Z3fP3D/oyjgVmHRwzGLR95EkjHLSUVQx0k8EQZHPSM+fXM393h0Rksb8Vk0T4kVoxGlIMVJaGppHLtPhAMELeA5dxrN2xT6bDc2ybTWbjWq1BnNSc5wFceoN6Fh2jjJYoj00390gxmlEuMIMSTlw7ER5GRKKYkZmJTeVJEF4gkZkoClHEZFelp8/g6daCWAYC/24grn6fSJDkZTTyNfJCKmx/O3Nxb+8QarChpdRnqSKcLxYFKYMqhjOu4ABFQQrNtUEYUH1rRCPkUBY6cZKuoSvn8L/SbdqObbl3NTKrctlHUVwDE5ABTigDlrgGrRBB2CQgQfwBJ6Ne+PReDFeF9GCsZw5BD9gvH0CUKSUbw==</latexit>

8

Photoelectron distribution in
SiPM

365 nmmean PEyPE distribution in data
80.09
0.00291888-0.00117109

0.0395916

0.0910576

0.0869906

0.0381313-0.000498826

0.00173501

0.0181476

0.0732873

0.0366851

0.0603641

0.0581927

0.0318337

0.0642246

0.013782

7

0.08
0.07

6
0.080206

0.0730602

0.0395963

0.0324879

0.0133267

0.034744

0.077408

0.0757741

0.06

5SiPM photo

0.0667145

0.0487292

0.0168159

0.011876

0.0162426

0.0156332

0.0485464

0.0633529

0.05

0.0145181

0.0176383

0.0133915

0.01318

0.0485025

0.0478063

0.04
0.03

4
0.0509001

30.0817675

0.0739368

0.0170783

0.0146918

0.0229714

0.021240.0693322

0.0787186

0.0471951

0.0805923

0.0508806

0.0415147

0.0400246

0.0471579

0.0808369

0.0388827

0.0027222

0.00747551

0.0469161

0.09266

0.0896353

0.0360592

0.00623342

0.000213355

2

0.02

1
0
00.01
12

34

5

6

7

8
x

08

photon countySimulated photon distribution140071200
61000
5SiPM
geometry

800
4600

3400

2200

10012345678x09Results for azimuthal angle φ = 0(see the figure on the left)

Measurement results
λ465 nm

Our simulation can not reproduce absolutevalues, so it is normalized to fit on-axis SiPM
data

3

PMT simulation
PMT experiment

Preliminary

SiPM simulation
SiPM expermiment2.5

cutoﬀangle

2

There are still some issues with themeasurement setup and analysis

1.5

1

It is likely that consideration in terms of onlygeometrical optics is not good enough tosimulate SiPM behavior properly

0.500510152025303540
θ angle, deg.

λ375 nm
3.5

Preliminary

PMT simulation
PMT experiment
SiPM simulation
SiPM expermiment3

cutoﬀangle

2.5
2
1.5
10.5
005

10

15

2025303540
θ angle, deg.

10Discussion• Although the results are not final, our measurement technique isusable and only needs a little polishing• There are still some diﬃculties with the setup, but that will besolved in a short time

• Relative performance is not consistent with the simulation, likely

due to interference eﬀects in Si3N4 and SiO2 layers and on siliconsurface• Cutoﬀ angle for SiPM configuration has to be checked11

To doSeveral things have to be done before making any solid conclusions:• Design a new light concentrator to remove the gaps and optimize
the cutoﬀ angle(in progress)• Compare the performance of PMT and SiPM by a simple raytracing simulation(after designing a new light concentrator)• Perform a full telescope simulation with CORSIKA andsim_telarray and study how NSB aﬀects new cameras(the final step)12