A multi-PMT module for IceCube GenTwo

Transcription

A multi-PMT module
for IceCube GenTwo
Lew Classen, Alexander Kappes, Uli Katz HAP Workshop
Aachen, 10.12.2014
Multi-PMT OMs: Concept advantages
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Increased photocathode area at ≤ price per photocathode area
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4π angular acceptance
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Directional sensitivity
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Single photon counting
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Background suppression with local coincidences
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No magnetic shielding needed
KM3NeT DOM
Alexander Kappes, HAP Workshop, Aachen, 10.12.2014
2
mDOM: Adaptation for the use in the deep ice
PMT base
*
●
ar
PMTs
down to
- 35°C
55
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0b
Reusable components from KM3NeT
Adaption / new development
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Pressure vessel
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PMT holders + reflectors
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Signal processing
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Interface to IceCube DAQ
ca. 13″ - 15″
* during refreezing
3
mDOM features
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Pressure vessel:
- 14” diameter
- rated for 700 bar
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24× 3” PMTs (Hamamatsu R12199-02)
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2× effective area of standard IceCube DOM
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Full 4π coverage
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Effective PMT saturation level: ~5000 p.e.
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Data readout (base concept)
- time-over-threshold for each PMT
- summed analog signal
4
PMT characteristics
KM3NeT requirements
Hamamatsu
R12199
Ø = 80 mm
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
length
power consumption incl. base
ETEL
D792KFL
Ø = 86 mm
>3
< 120 mm
< 4 mW
HZC
XP53B20
Ø = 76 mm
5
Hamamatsu R12199-02: Dark rate measurements I
Setup:
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3 different PMTs with voltage divider base (cathode @ -1100 V)
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Threshold: 30 mV (with 10× amplifier)
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PMTs mounted in foam holding structure
Anti-noise measures (PMT shaft)
1. no measures
2. tape insulation + grounded copper foil
3. only tape insulation
4. +5. tape insulation + copper housing (1 PMT)
6
Hamamatsu R12199-02: Dark rates II
Changed setup
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photocathode part of PMT in silicone oil (same electrical properties as optical gel)
silicone oil
drak rate @ -30mV, PMTs inside silicone oil
4000
Long-term dark rates
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500 - 700 Hz @20ºC (dominated by thermal emission)
3500
zb6171 G=4.7e6 thr=0.51 pe
zb6055 G=6.4e6 thr=0.35 pe
zb6180 G=5.6e6 thr=0.4 pe
3000
dark rate [Hz]
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zb6171
zb6055
zb6180
@ -30ºC
- thermal emission: factor 2 decrease every ~6ºC → factor ~300
- field effects dominate → measurements in climate chamber beginning next year
2500
2000
1500
1000
500
0
0
100
200
300
400
500
600
700
800
900
time elapsed [h]
Ivren/Classen 2014
7
Hamamatsu R12199-02: Dark rates III
First measurement with reversed polarity (cathode @ 0 V, foam holding structure)
dark rate with positive HV polarity, PMTs inside foam holder (=no insulation)
900
zb6055 @ -15mV
zb6055 @ -30mV
dark rate [Hz]
800
thr=0.17 pe
700
600
500
thr=0.35 pe
400
300
0
20
40
60
80
100
120
140
160
time elapsed [h]
8
PMT holding structure
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Produced via laser sintering (type of 3D-printing) (first prototype delivered)
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Takes up 12 PMTs (4 + 8)
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Tube for pouring of optical gel
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Allows for mounting of reflective cones
9
Effect of reflectors
old form factor
Frytz 2014
relative intensity [%]
no holder/reflector
holder only
reflector
photon incidence angle [o]
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Holding structure reduces amount of gel needed (screening recovered by reflectors)
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Reflectors increase directionality significantly (30% gain in intensity for |Φ| < 60º)
10
Pressure vessel
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Two 14” glass half spheres (borosilicate glass)
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Aluminium cylinder with 5-10 cm height for electronics (similar design used for first AMANDA modules) → potential stability/thickness issues Alternative: cast glass half spheres with few cm cylindrical extension
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Connection of parts either via under-pressure or with flanges
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Angular acceptance simulation
PMT model
Ham R12199-2
optical gel
photocathode
reflector
absorber
glass bulb
(massive)
aluminium
glass
12
θ [o]
Acceptance simulation results
φ
[o]
mDOM with reflectors
IceCube DOM
Average acceptance: mDOM = 2× DOM
45 cm2
380 cm2
13
θ [o]
Acceptance simulation results
φ
[o]
mDOM with reflectors
IceCube DOM
Average acceptance: mDOM = 2× DOM
45 cm2
380 cm2
13
Electronics: PMT base
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High voltage supply
- HV generation on base (Cockroft-Walton)
- 3-4 mW power consumption
- cathode @ ~1100 V; anode @ 0 V
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Signal processing
- pre-amp + comparator (ToT) + LVDS drivers on ASIC
- power consumption:
● ToT signal only: ~20 mW
● ToT + analog signal: ~50 mW (?)
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Voltage + threshold can be set via I2C
Modifications:
● Pre-amp/pulse shaping not optimal → probably needs adaption
● Reduction of power consumption of analog part? (first have to check 50 mW)
Timmer, 2010 JINST 5 C12049
14
Electronics: Integration into IceCube DAQ
DAQ block diagram (1x 10” PMT)
e.g. CYCLON V (SoC variant)
10” PMT
Interface
3” PMT
FPGA: digitization (ToT)
time-stamping
data packaging
SUM
...
...
...
24x
24x
Base:
pre-amp
comparator
Alexander Kappes, Occasion, Place, Date
15
Summary and timeline
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DOM with larger number of small PMTs provides several advantages (increased acceptance, 4π coverage, local coincidences, inherent directionality)
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mDOM design provides
- 2× average acceptance of IceCube DOM
- with almost uniform 4π coverage
- and 24× segmented photocathode area
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Status
- General mechanical layout close to final
- PMTs for prototypes selected and available
- Base: photocathode probably at negative voltage (KM3NeT design) (final decision requires some further measurements)
- Electronics/integration into IceCube DAQ: major focus during next months
Timeline
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Mechanical prototype within ~6 months
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Prototype of electronics setup until end of 2015
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A multi-PMT module for IceCube GenTwo

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