Multi-PMT Optical Modules · (mainboard, power supply etc. subtracted) ... 1401.2046 (2014) 00 m IceCube cabling scheme. Alexander Kappes, HAP Workshop: Advanced Technologies, 2

Institut für KernphysikAlexander Kappes

Multi-PMT Optical Modulesfor application in harsh and remote environments

HAP Workshop: Advanced Technologies

University of Mainz, 2. Feb. 2016

Alexander Kappes, HAP Workshop: Advanced Technologies, 2. Feb. 2016

2

Target applicationsDetection of Cherenkov radiation of charged particles

Examples of target experiments

• Neutrino telescopes (IceCube, KM3NeT, BAIKAL) - high-energy astrophysics

- MeV supernova neutrinos

- neutrino oscillation at GeV energies (oscillation parameters, mass ordering)

• Large-volume-tank detectors (e.g. Hyper-K) - neutrino oscillations in sub-GeV to GeV range

(CP phase, mass ordering)

- MeV supernova neutrinos, solar neutrinos

- proton decay

• Neutrino detectors in lakes (CHIPS) - CP phase in neutrino oscillations

KM3NeT (artist’s view)

Hyper-K


3

Desired properties of optical modules• Large effective area

• Single photon detection and high dynamic range ( > several 100 p.e.)

• Good photon separation (photon counting)

• ns timing

• Low background

• Directional information (with 4π sensitivity)

• 10+ years of maintenance-free operation under (and/or) - high pressure (up to 600 bar),

- low temperatures (-45°C),

- corrosive environments (salt water)

• Low power consumption (few Watts)

• Cheap (≪ 10 kEUR)


4

Optical modules in neutrino telescopesUntil recently, single large PMT in glass sphere looking downwards(DUMAND, BAIKAL, AMANDA, ANTARES, IceCube)

• Advantageous features

- in particular sensitive to up-going neutrinos (main target in the beginning)

- only one readout channel (electronics complexity)

- price per photocathode area used to be lower for large PMTs

• Disadvantages

- no directional sensitivity (direction reconstruction)

- ≪ 0.5 of solid angle covered (sensitivity to down-going ν)

- ambiguities in photon counting (energy determination)

- no local coincidences on single module (e.g. for background suppression)

IceCube Optical Module


4

Optical modules in neutrino telescopesUntil recently, single large PMT in glass sphere looking downwards(DUMAND, BAIKAL, AMANDA, ANTARES, IceCube)

• Advantageous features

- in particular sensitive to up-going neutrinos (main target in the beginning)

- only one readout channel (electronics complexity)

- price per photocathode area used to be lower for large PMTs

• Disadvantages

- no directional sensitivity (direction reconstruction)

- ≪ 0.5 of solid angle covered (sensitivity to down-going ν)

- ambiguities in photon counting (energy determination)

- no local coincidences on single module (e.g. for background suppression)

→ multi-PMT optical modules aim at improving on these

IceCube Optical Module


5

Multi-PMT optical modules

NEVOD module• Already thought of in the DUMAND era (1979)

and realized in NEVOD!

• First “modern” version in KM3NeT (Kavatsyuk et al, NIM A 695 (2012))

- PMTs still best choice for low background applications

- today, price per photocathode area for 3” PMTs < 10” PMTs(in mass production)

- advances in electronics / data transmission

• Successful in-situ application in KM3NeT

Borog et al, Proc. DUMAND Workshop 1979

KM3NeT


5










KM3NeT

single PMT rate 40K coincident rate between 2 PMTs

KM3NeT, Eur. Phys. J. C (2014)


5










KM3NeT

IceCube mDOM

• Under development for IceCube-Gen2 (mDOM)(alternative to baseline design with single, large PMT)

single PMT rate 40K coincident rate between 2 PMTs

KM3NeT, Eur. Phys. J. C (2014)


6

Challenges for multi-PMT modules

• Tight available space and power constraints

• Large number of readout channels

• Production of large number of small (3”) PMTs (up to several 100k)

• Availability of PMTs with suitable propertiesKM3NeT DOM


7

Photomultipliers

Hamamatsu R12199-02 Hamamatsu R12199-02 HA ETEL 9320 KFL

- photocathode Ø = 80 mm - length = 98 mm /

cylinder Ø = 52 mm - TTS (FWHM) = ~3.5 ns - peak-to-valley ratio = ~3.5 - gain ~5×106 @ ~1100 V

cathode potential

insulation

improves dark countfor cathode @ −HV

- photocathode Ø = 87 mm - length = 95 mm /

cylinder Ø = 52 mm - characteristics under

investigation

• Available PMTs with adequate properties (based on KM3NeT criteria)

• Potential other manufactures: HZC (China), MELZ (Russia)


8

Mechanics: Pressure vessel• Spherical glass vessels (borosilicate glass) routinely used

in deep-sea exploration

- transparent to optical light

- high compression strength (~1400 N/mm2 (MPa))

- typ. sizes 13”, 17” with thickness 15−20 mm

- inert to salt water

- low price

• Challenges for usage in ice: max ∅ ≲ 14” (bore hole size)→ additional space for electronics needed

- 14” sphere with cylindrical extension (developed with Nautilus)

- glass thickness: 14 mm

- pressure rating: 700 bar (to be tested)

- Production with same technique as “standard” glass spheres → comparable low price

© Nautilus MARINE SERVICE GmbH

IceCube mDOM pressure vessel


9

Mechanics: Transmissivity

current IceCube glass (Bentos)

Japanese glass (reduced Fe2O3)

Nautilus glass

Cherenkov spectrum

• Cherenkov photon spectrum ~ 1/λ2

→ transparency in UV range important

• Significant differences between glasses of same material (borosilicate glass)

• But also radioactive contamination important → optical background

typ. HQE PMT


10

Mechanics: PMT holding structure

• Complex structure with e.g. - O-ring cavity (sealing and PMT fixation) - distance holders for “gel-coating” of PMT

• Nowadays, fast and well-priced production via laser sintering (type of 3D-printing)

• Allows for mounting of reflective cones

IceCube mDOM


11

Effect of reflectors on angular acceptance

• Reflectors significantly increase directionality of PMT

IceCube mDOM

with reflector

without reflector


12

Electronics: General considerations

• Detectors at remote locations (deep sea, South Pole)→ power consumption crucial factor

• Particulate important for IceCube

- power (+ comm.) through ~20 copper wire pairs

- power usage limited by voltage drop from surface

→ max. ~3.4 W per DOM (3 DOMs per wire pair)

→ ~60 mW per PMT (readout/digitization + HV) (mainboard, power supply etc. subtracted)

IceCube Coll. PINGU LOI arXiv:1401.2046 (2014)

270

0 m

IceCube cabling scheme


13

DOM electronics: Generic block diagram

FPGA

HV generator

front end electronics

serial DAC HV ctrl

signal digitization

comms

power supplyPMT

mainboard

PMT base


13

DOM electronics: Generic block diagram

FPGA

HV generator

front end electronics

serial DAC HV ctrl

signal digitization

comms

power supplyPMT

mainboard

PMT base

• Digitization on base - minimize noise pickup

- no need to drive differential analog signal

- requires low footprint components


14

Electronics: PMT base

• Requirements - individually adjustable HV (~1000 V)

- low-power

- compact design

• KM3NeT design (Nikhef)(also used for IceCube-mDOM)

- Cockroft-Walton circuit

- power consumption 3−4 mW

- fits on single side of PMT base

Timmer, 2010 JINST 5 C12049


• Standard signal digitization: sampling of amplitude in fixed interval(IceCube baseline DOM: flash ADC with 14 bit, 250 MHz)

→ disadvantage: high power consumption, size

• Alternative: Time-over-Threshold (ToT)

- shape of single photon pulse known (amplitude variable)→ sample with comparator (time-over-threshold, KM3NeT)

- advantages: low-power, small footprint (fits on backside of base)

- disadvantage: ambiguities for fast consecutive signals(particularly the case for IceCube because of large scattering in ice)

15

Electronics: Readout schemes

IceCube waveform (example)

time

ampl

itude

time

ampl

itude

˝

time

ampl

itude


16

Electronics: Multi-comparator readout

• Multi-comparator design for IceCube mDOM

• Challenges: limited space (backside of base) and power (~50 mW)

• Two-fold strategy

- Discrete design: allows for ~4 comparators (under development @ DESY-Zeuthen)

- ASIC design: 63 comparators with 6 bit encoder(under development @ LTE Univ. Erlangen)

• Output: pseudo-digital signal (single-ended)→ time-stamping in FPGA with 250−500 MHz

©JürgenRöber(LTE)

on/off

on/off

on/off

on/off

on/off

on/off

Top-Ref

Bot-Ref

63Comparators

6bit

R2

2

R3

R4

R5

R6

R7

R8

.

.

.

..

R1

R64

mDOM 63-comparator ASIC design


17

Pulse reconstruction with 63 discriminators

• Encouraging first results

- Input: 10 pulses, mean amplitude 3 pe

- ΔCharge < 1%

- Δt(first pulse) ≲ 1 ns

• True pulse times vs. reconstructed

truereco


18

Summary• PMTs still first (only) choice for low-background, single-photon detection scenarios

• Multi-PMT optical modules provide several attractive advantages compared to “standard” single-large-PMT modules (directionality, increased photocathode area, improved photon counting, local coincidences)

• Challenges: tight space and power constraints + costs - mechanics for large number of PMTs

- readout of large number of channels, digitization of complex signals

• In KM3NeT, 31 PMTs with individual, single time-over-threshold readout→ successfully tested in situ (deep sea)

• IceCube-Gen2 aims at advanced version for application in the deep ice - ASIC development for 63-comparator readout of 24 PMTs

- optimized UV sensitivity (pressure vessel, optical gel) and mechanics

- with moderate modification also applicable in other experiments (Hyper-K, CHIPS . . . )

Backup


20

Photomultipliers

Requirements (KM3NeT)

quantum efficiency @ 470 nm > 20%

transit time spread (σ, FWHM) < 2 ns, < 4.6 ns

gain > 2 · 106

supply voltage < 1400 V

dark count rate @ 15°C < 1.5 kHz

peak to valley ratio > 3

length < 120 mm

power consumption incl. base < 4 mW


21

PMTs: HV polarity and background

-HV

+HV

● easier to reach low dark count rates

● galvanic decoupling of anode→ affects signal & electronics

● easy coupling to readout ● low dark count rates require

some effort


22

Dark-count ratesGlacial ice very radioactive clean → module itself dominant background source

Sources for dark count rate

• Radioactive decays (e.g. K40) (glass of PMT and pressure vessel)

• Thermal emission from photocathode→ low temperatures

• Field effect emission from PMT electrodes→ not too high voltages/gains

Dark current

gaindark current

Flyckt, S.-O. & Marmonier, C. PHOTOMULTIPLIER TUBES principles & applications


23

Dark count rate vs. temperature

Dark-count rate reduction from ~500 Hz @ 20º C to 100-150 Hz < -30º C (thresh. ~0.3 pe, -HV)

(comparison: standard IceCube 10” PMT: ~300-400 Hz @ 0.25 p.e.)

probably due to lagging PMT temperature

cooling

heating

Hamamatsu R12199-02

(very) preliminary


24

Controlling the dark-count rate with negative HV

silicone oil

Hamamatsu R12199-02 photocathode area in silicone gel (oil)

coated Hamamatsu R12199-02 (higher costs)

in air, −HV, preliminary

−HV

insulation

−HV, air

−HV, silicone oil

0

500

1000

1500

2000

0 100 200 300 400 500

dark

rate

[Hz]

time elapsed [h]

zb6180, -HV, airzb6180, -HV, oil

zb6180, +HV, air

dark rate @ thr=-30mV, amplify x10

+HV, air


25

Effective area from GEANT4 simulation

0

50

100

150

200

250

300

350

400

300 320 340 360 380 400 420 440 460 480

mea

n ef

fect

ive

area

[cm

2 ]

wavelength [nm]

mDOMIceCube DOM

mDOM with QEIceCube DOM with QE

× ~2.5

(not HQE PMT)

mDOM

IceCube DOM


26

PMT form factor• Pressure vessel diameter limited to 14”

(size of borehole)

• Length (including vacuum seal) and diameter of PMT critical parameters

→ even moderately shorter PMTs highly beneficial

C-C

D-D

C C

D

D

1

H

2 3 4 5 6 7 8 9 10 11 12

1 2 3 4 5 6 87

G

F

E

D

C

B

A

H

G

F

E

D

C

B

A

9 10 11 12 Zust. Änderungen Datum Name

Datum Name Bearb.

Gepr.

Norm

Blatt

Maßstab Position MengeOberfläche

Werkst.

27-10-2014-02.000

Anordnung 24-fach-10mm23.10.2014 Kärcher

1 A2

1:2

PMT-Halter III

000 1

Mittelpunktsabstand: 10mm

90°

25

16

5040

.218°

90°

2

356P

57°

174.1

134.1

2

86.7°

10 12.9

22.5°45°

8x

90°

4x

42.7°

R6R6

2.9

45.3°

R6

R6

4.1

C-C

D-D

C C

D

D

1

H

2 3 4 5 6 7 8 9 10 11 12

1 2 3 4 5 6 87

G

F

E

D

C

B

A

H

G

F

E

D

C

B

A


Datum Name Bearb.

Gepr.

Norm

Blatt


Werkst.

27-10-2014-02.000

Anordnung 24-fach-10mm23.10.2014 Kärcher

1 A2

1:2

PMT-Halter III

000 1

Mittelpunktsabstand: 10mm

90°

25

16

5040

.2

18°

90°

2

356P

57°

174.1

134.1

2

86.7°

10 12.9

22.5°45°

8x

90°

4x

42.7°

R6R6

2.9

45.3°

R6

R6

4.1

Hamamatsu R12199-02 (units in mm)

2.9 mm

1 mm

F

87654321

1 2 3 4

A

B

C

D

E

F

A

B

C

D

E


Datum Name Bearb.

Gepr.

Norm

Blatt


Werkst.

3 CC PMT III

Photomultiplier26.03.2015 Kärcher

1 A3

1:1

PMT- Halter III

3 CC PMT III

A

Ansicht A M 2:1

42

47.5

R25.5

42

47.5

12.7

36.3

14.1

P3419

19

14

112.6

P52

P80

13

22.5

10.9

98


27

PMT base• HV generation on base; copied from KM3NeT

(Cockcroft Walton design, Nikhef)

- low power (3−5 mW)

- small adaptions due to new board shape

• Front-end electronics for signal processing on backside

KM3NeT: HV generation New optimized board shapewith HV circuitry

Backside with front-end electronics

mDom Base DesignStefan Lindner

Layoutimpressions

28

CockcraftWaltonimplementedonTopside:

Voltagepotentialdependentclearancecheckandgroundplanecalculation:

Full3ddesignwithclearancerulesforoptimizedroomusage


TestboardTopview

29

Finaloutline

ASICCoCov2(Nikhef)

ConnectorsfordigitalCommunication

AnalogOutput

PowerSupply


TestboardTopview

30

MicrocontrollerFreescaleKL03 (inDelivery) - ID - Communication - Monitoring - DAC? - CockcraftWalton

Control?

LowPowerDAC LT1662 (inDelivery)- RefVoltageforA/

DConversion- HVControl

Voltage


• BasedonCurrentFeedbackOpampOPA2683• Evaluationof

– InvertingvoltageAmplifier– Non-invertingvoltageAmplifier– ChargeAmplifier

• Test-PCB

Preamplifier

31


• PowerConsumption<10mWat~75MHzBandwidth

FirstresultsPreamplifier

32


PreamplifierPulseresponse

33


34

Discrete layout for single ToT readout• Low power & tiny footprints

• Micro controller - Communication - Control of DACs (HV, threshold ToT) - PMT-Status - Calibration

• Low Power Charge Amplifier & Comparator

Load ConsumptionHV generation ~5 mWMicrocontroller << 1 mWDACs ~10 µWCharge Amplifier ~5 mWToT ~5 mWSignalling to mainboard ??

charge amplifier

ToT (Schmitt-Trigger)

Test setup

©StefanLindner(LTE)


35

Electronics: Baseline readout IceCube mDOM• 4 ToTs discrete discriminators

• Measured power consumption: ~40 mW per base for 0.001 – 1 MHz toggle rate (expected rates ≲ 0.05 MHz)

©AxelKretzschmann(DESY)

Documents

Multi-PMT Optical Modules · (mainboard, power supply etc. subtracted) ... 1401.2046 (2014) 00 m IceCube cabling scheme. Alexander Kappes, HAP Workshop: Advanced Technologies, 2