Slides

Multi-PMT Optical Modules
for application in harsh and remote environments
HAP Workshop: Advanced Technologies
University of Mainz, 2. Feb. 2016
Alexander Kappes
Institut für Kernphysik
2
Target applications
Detection 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
KM3NeT (artist’s view)
(CP phase, mass ordering)
- MeV supernova neutrinos, solar neutrinos
- proton decay
• Neutrino detectors in lakes (CHIPS)
- CP phase in neutrino oscillations
Alexander Kappes, HAP Workshop: Advanced Technologies, 2. Feb. 2016
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)
Alexander Kappes, HAP Workshop: Advanced Technologies, 2. Feb. 2016
4
Optical modules in neutrino telescopes
Until 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)
Alexander Kappes, HAP Workshop: Advanced Technologies, 2. Feb. 2016
IceCube Optical Module
4
Optical modules in neutrino telescopes
Until 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
Alexander Kappes, HAP Workshop: Advanced Technologies, 2. Feb. 2016
IceCube Optical Module
Borog et al,
Proc. DUMAND Workshop 1979
Multi-PMT optical modules
• Already thought of in the DUMAND era (1979) and realized in NEVOD!
NEVOD module
• 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
Alexander Kappes, HAP Workshop: Advanced Technologies, 2. Feb. 2016
KM3NeT
5
single PMT rate
Borog et al,
40K coincident rate
Proc.
DUMAND
Workshop 1979
between
2 PMTs
Multi-PMT optical modules
• Already thought of in the DUMAND era (1979) and realized in NEVOD!
NEVOD module
• 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)
in electronics
- advances
KM3NeT,
Eur. Phys.
J. C (2014) / data transmission
• Successful in-situ application in KM3NeT
Alexander Kappes, HAP Workshop: Advanced Technologies, 2. Feb. 2016
KM3NeT
5
single PMT rate
Borog et al,
40K coincident rate
Proc.
DUMAND
Workshop 1979
between
2 PMTs
Multi-PMT optical modules
• Already thought of in the DUMAND era (1979) and realized in NEVOD!
NEVOD module
KM3NeT
• 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)
in electronics
- advances
KM3NeT,
Eur. Phys.
J. C (2014) / data transmission
• Successful in-situ application in KM3NeT
• Under development for IceCube-Gen2 (mDOM)
(alternative to baseline design with single, large PMT)
IceCube mDOM
Alexander Kappes, HAP Workshop: Advanced Technologies, 2. Feb. 2016
5
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 properties
Alexander Kappes, HAP Workshop: Advanced Technologies, 2. Feb. 2016
KM3NeT DOM
7
Photomultipliers
• Available PMTs with adequate properties (based on KM3NeT criteria)
Hamamatsu R12199-02
- 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
Hamamatsu R12199-02 HA
insulation
cathode potential
improves dark count
for cathode @ −HV
• Potential other manufactures: HZC (China), MELZ (Russia)
Alexander Kappes, HAP Workshop: Advanced Technologies, 2. Feb. 2016
ETEL 9320 KFL
- photocathode Ø = 87 mm
- length = 95 mm / cylinder Ø = 52 mm
- characteristics under investigation
8
Mechanics: Pressure vessel
© Nautilus MARINE
SERVICE GmbH
• 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
Alexander Kappes, HAP Workshop: Advanced Technologies, 2. Feb. 2016
IceCube mDOM
pressure vessel
9
Mechanics: Transmissivity
• Cherenkov photon spectrum ~ 1/λ2
→ transparency in UV range important
• Significant differences between glasses of same material (borosilicate glass)
• But also radioactive contamination Japanese glass (reduced Fe2O3)
Nautilus glass
current IceCube glass (Bentos)
important → optical background
typ. HQE PMT
Alexander Kappes, HAP Workshop: Advanced Technologies, 2. Feb. 2016
Cher
enko
v
spec
t
rum
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
Alexander Kappes, HAP Workshop: Advanced Technologies, 2. Feb. 2016
11
Effect of reflectors on angular acceptance
IceCube mDOM
• Reflectors significantly
increase directionality of PMT
with reflector
without reflector
Alexander Kappes, HAP Workshop: Advanced Technologies, 2. Feb. 2016
12
Electronics: General considerations
• Detectors at remote locations (deep sea, South Pole)
IceCube cabling scheme
→ 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)
2700 m
IceCube Coll. PINGU LOI arXiv:1401.2046 (2014)
Alexander Kappes, HAP Workshop: Advanced Technologies, 2. Feb. 2016
13
DOM electronics: Generic block diagram
PMT
serial DAC
HV ctrl
comms
HV generator
power supply
front end
electronics
signal
digitization
FPGA
PMT base
mainboard
Alexander Kappes, HAP Workshop: Advanced Technologies, 2. Feb. 2016
13
DOM electronics: Generic block diagram
PMT
serial DAC
HV ctrl
comms
HV generator
power supply
front end
electronics
signal
digitization
FPGA
PMT base
• Digitization on base
- minimize noise pickup
- no need to drive differential analog signal
- requires low footprint components
Alexander Kappes, HAP Workshop: Advanced Technologies, 2. Feb. 2016
mainboard
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
Alexander Kappes, HAP Workshop: Advanced Technologies, 2. Feb. 2016
Timmer, 2010 JINST 5 C12049
Electronics: Readout schemes
• Standard signal digitization: sampling of amplitude in fixed interval
(IceCube baseline DOM: flash ADC with 14 bit, 250 MHz)
amplitude
15
→ disadvantage: high power consumption, size
- 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)
amplitude
• Alternative: Time-over-Threshold (ToT)
time
time
- disadvantage: ambiguities for fast consecutive signals
(particularly the case for IceCube because of large scattering in ice)
amplitude
IceCube waveform (example)
˝
time
Alexander Kappes, HAP Workshop: Advanced Technologies, 2. Feb. 2016
16
Electronics: Multi-comparator readout
• Multi-comparator design for IceCube mDOM
mDOM 63-comparator ASIC design
Top-Ref
R1
• Challenges: limited space (backside of base) and power (~50 mW)
R2
R3
• Two-fold strategy
- Discrete design: allows for ~4 comparators R4
2
on/off
R5
on/off
R6
R7
• Output: pseudo-digital signal (single-ended)
R8
.
.
R64
Bot-Ref
Alexander Kappes, HAP Workshop: Advanced Technologies, 2. Feb. 2016
6bit
on/off
(under development @ DESY-Zeuthen)
- ASIC design: 63 comparators with 6 bit encoder
(under development @ LTE Univ. Erlangen)
→ time-stamping in FPGA with 250−500 MHz
on/off
on/off
on/off
.
..
63Comparators
©JürgenRöber(LTE)
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
true
reco
Alexander Kappes, HAP Workshop: Advanced Technologies, 2. Feb. 2016
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 . . . )
Alexander Kappes, HAP Workshop: Advanced Technologies, 2. Feb. 2016
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
Alexander Kappes, HAP Workshop: Advanced Technologies, 2. Feb. 2016
21
PMTs: HV polarity and background
-HV
●
easy coupling to readout
●
low dark count rates require
some effort
●
easier to reach low dark count rates
●
galvanic decoupling of anode
→ affects signal & electronics
+HV
Alexander Kappes, HAP Workshop: Advanced Technologies, 2. Feb. 2016
22
Dark-count rates
Dark current
Glacial ice very radioactive clean
→ module itself dominant background source
Sources for dark count rate
• Radioactive decays (e.g. K40)
gain
dark
current
(glass of PMT and pressure vessel)
• Thermal emission from photocathode
→ low temperatures
• Field effect emission from PMT electrodes
→ not too high voltages/gains
Flyckt, S.-O. & Marmonier, C. PHOTOMULTIPLIER
TUBES principles & applications
Alexander Kappes, HAP Workshop: Advanced Technologies, 2. Feb. 2016
23
Dark count rate vs. temperature
Hamamatsu R12199-02
(very) preliminary
cooling
probably due to lagging PMT temperature
heating
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.)
Alexander Kappes, HAP Workshop: Advanced Technologies, 2. Feb. 2016
24
Controlling
the dark-count rate with negative
HV
Hamamatsu R12199-02
coated Hamamatsu R12199-02
photocathode area in silicone gel (oil)
(higher costs)
insulation
−HV
silicone oil
2000
dark rate @ thr=-30mV, amplify x10
zb6180, -HV, air
zb6180, -HV, oil
zb6180, +HV, air
in air, −HV, preliminary
dark rate [Hz]
1500
−HV, air
1000
−HV, silicone oil
500
+HV, air
0
0
100
200
300
400
500
time elapsed [h]
Alexander Kappes, HAP Workshop: Advanced Technologies, 2. Feb. 2016
25
Effective area from GEANT4 simulation
400
mean effective area [cm 2]
350
300
250
200
mDOM
IceCube DOM
mDOM with QE
IceCube DOM with QE
(not HQE PMT)
150
100
50
× ~2.5
mDOM
IceCube DOM
0
300 320 340 360 380 400 420 440 460 480
wavelength [nm]
Alexander Kappes, HAP Workshop: Advanced Technologies, 2. Feb. 2016
6
1
2
7
3
4
8
5
6
7
9
8
9
10
10
11
42.7
°
16
A
42.7
°
2.9
2
12
26
R6
R6
B
• Pressure vessel diameter limited to 14”
10
2.9
50
(size of borehole)
12.9
°
86.7
25
C
18°
40.2
°
90
PMT form factor
356
C-C
and • Length (including vacuum seal)
diameter
of PMT critical
parameters
1
2
3
D
22.5°
4
6
R6
5
8x4
5°
A
42
4x
90
°
E
98
R6
2
10.9
14
45.
3°
4.1
R6
R25.5
90°
13
8
2.9R6
mm
.1
174
→ even moderatelyDshorter PMTs highly beneficial
7
F
47.5
Mittelpunktsabstand: 10mm
52
G
C
57
°
C
19
34
22.5
47.5
B
A
.1
134
19
Oberfläche
Maßstab
1:2
Position
000
Menge
1
14.1
Werkst.
C
D-D
Bearb.
Datum
Name
23.10.2014
Kärcher
Gepr.
H
Hamamatsu
R12199-02
(units
in4mm)
1
2
3
1 mm
D
6
7
8
12.7
36.3
Alexander
Kappes, HAP Workshop: Advanced Technologies, 2. Feb. 2016
D
Ansicht A
M 2:1
Blatt
27-10-2014-02.000
Zust.
5
Anordnung 24-fach-10mm
PMT-Halter III
Norm
Änderungen
9
Datum
1
A2
Name
10
11
12
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 shape
with HV circuitry
Alexander Kappes, HAP Workshop: Advanced Technologies, 2. Feb. 2016
Backside with front-end electronics
Layoutimpressions
CockcraftWalton
implementedon
Topside:
Stefan Lindner
Voltagepotential
dependentclearance
checkandgroundplane
calculation:
mDom Base Design
Full3ddesignwith
clearancerulesfor
optimizedroomusage
28
TestboardTopview
Finaloutline
ASICCoCov2(Nikhef)
PowerSupply
AnalogOutput
Connectorsfordigital
Communication
Stefan Lindner
mDom Base Design
29
TestboardTopview
Microcontroller
FreescaleKL03
(inDelivery)
- ID
- Communication
- Monitoring
- DAC?
- CockcraftWalton
Control?
LowPowerDAC
LT1662
(inDelivery)
- RefVoltageforA/
DConversion
- HVControl
Voltage
Stefan Lindner
mDom Base Design
30
Preamplifier
• BasedonCurrentFeedbackOpampOPA2683
• Evaluationof
– InvertingvoltageAmplifier
– Non-invertingvoltageAmplifier
– ChargeAmplifier
• Test-PCB
Stefan Lindner
mDom Base Design
31
FirstresultsPreamplifier
• PowerConsumption<10mWat~75MHzBandwidth
Stefan Lindner
mDom Base Design
32
PreamplifierPulseresponse
Stefan Lindner
mDom Base Design
33
34
Discrete layout for single ToT readout
• Low power & tiny footprints
Load
Consumption
• Micro controller
HV generation
~5 mW
Microcontroller
<< 1 mW
DACs
~10 µW
Charge Amplifier
~5 mW
ToT
~5 mW
Signalling to mainboard
??
-
Communication
Control of DACs (HV, threshold ToT)
PMT-Status
Calibration
• Low Power Charge Amplifier & Comparator
Test setup
charge
amplifier
Alexander Kappes, HAP Workshop: Advanced Technologies, 2. Feb. 2016
ToT (Schmitt-
Trigger)
©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)
Alexander Kappes, HAP Workshop: Advanced Technologies, 2. Feb. 2016