LENA Photosensor R&D
Marc Tippmann
Lothar Oberauer, Michael Wurm, Gyorgy Korga, Quirin
Meindl, Michael Nöbauer, Thurid Mannel, Martin
Zeitlmair, German Beischler
Technische Universität München
DPG-Frühjahrstagung 2011, Karlsruhe
2011/03/31
Overview
LENA photosensor requirements
PMT characterization
• Measurements at the Laboratori Nazionali del Gran Sasso
Outlook
• Munich test stand
• Optical module development
Summary
LENA photosensor requirements
LENA photosensor requirements:
Overview
Requirements on photo sensors
• Sensor performance
• Environmental properties
• Availability until start of
construction
• Cost-performance-ratio
Desired energy resolution for low energies:
→ Light yield ≥ 200 photoelectrons/MeV
→ 30% optical coverage
→ 3000m² effective photosensitive area needed
→ Current standard configuration:
Liquid scintillator detector:
63,000 PMTs (8“)
with Winston Cones (area ×1.75)
Water cherenkov muon veto:
6,000 PMTs (8“)
1/9
LENA photosensor requirements: List
Timing
TTS (spe, FWHM)
<3.0ns
Early pulses
<1%
Late pulses
<4%
2/9
LENA photosensor requirements: List
Timing
TTS (spe, FWHM)
<3.0ns
Early pulses
<1%
Late pulses
<4%
Photo detection efficiency
PDE for λpeak=420nm
>20%
Dynamic range
spe – 0.3pe/cm²
2/9
LENA photosensor requirements: List
Timing
TTS (spe, FWHM)
<3.0ns
Early pulses
<1%
Late pulses
<4%
Michael Wurm, TUM, LENA - PMm² meeting 07/04/2009
Photo detection efficiency
PDE for λpeak=420nm
>20%
Dynamic range
spe – 0.3pe/cm²
Noise (for PMTs)
Gain
>3∙106
spe p/V
>2
Dark count per area
<15Hz/cm²
Ionic afterpulses (0.1-200 μs)
<5%
Fast afterpulses (5-100 ns)
<5%
2/9
LENA photosensor requirements: List
Teresa Marrodán, PhD thesis
Timing
TTS (spe, FWHM)
<3.0ns
Early pulses
<1%
Late pulses
<4%
Photo detection efficiency
PDE for λpeak=420nm
>20%
Dynamic range
spe – 0.3pe/cm²
Noise (for PMTs)
Gain
>3∙106
spe p/V
>2
Dark count per area
<15Hz/cm²
Ionic afterpulses (0.1-200 μs)
<5%
Fast afterpulses (5-100 ns)
<5%
Photon
Fast afterpulse
2/9
LENA photosensor requirements: List
Teresa Marrodán, PhD thesis
Timing
TTS (spe, FWHM)
<3.0ns
Early pulses
<1%
Late pulses
<4%
Photo detection efficiency
PDE for λpeak=420nm
>20%
Dynamic range
spe – 0.3pe/cm²
Noise (for PMTs)
Environmental properties
Gain
>3∙106
Pressure resistance
>10bar
spe p/V
>2
238U
<3∙10-8 g/g
Dark count per area
<15Hz/cm²
232Th
Ionic afterpulses (0.1-200 μs)
<5%
natK
Fast afterpulses (5-100 ns)
<5%
Detector lifetime
content
content
content
<1∙10-8 g/g
<2∙10-5 g/g
>30yrs
2/9
LENA photosensor requirements
Fast afterpulses (fAP):
Ongoing measurements of fAP time distribution for
candidate PMT series →
• Investigate causes
• Currently studying their influence on the efficiency of the
p decay coincidence: Bachelor thesis by Thurid Mannel
• Possible methods of discrimation from photons?
Bachelor thesis by Martin Zeitlmair
3/9
PMT characterization
Measurements at the LNGS, Gran Sasso
Borexino PMT testing facility
• Pulsed ps laser diode light source:
410nm, light pulse FWHM <30ps
• Total time resolution <140ps
• Can measure up to 32 PMTs
simultaneously
• Measure transit time distribution
(TDC), fast + ionic afterpulse time
distribution (MTDC), charge
spectrum (ADC)
Measured 1 sample each of:
• Hamamatsu: R6091(3“), R6594(5“),
R5912(8“) and R7081(10“)
• ETEL: 9351(8“)
4/9
Measurements @LNGS:
R6594 vs. R7081
5“
10“
R6594 (5“)
R7081 (10“)
Voltage
+1670V
+1520V
Gain
1.0∙107
1.3∙107
Photoelectrons
(pe) per trigger
5.53%
2.91%
Threshold
0.2pe
0.2pe
TTS (FWHM)
(Hamamatsu)
1.91ns
(1.5ns)
3.05ns
(3.5ns)
Early pulses (all
non-gaussian)
2.95%
0.57%
Late pulses
(after photon
pulse peak)
3.13%
3.09%
5/9
Measurements @LNGS:
R6594 vs. R7081
R6594 (5“)
R7081 (10“)
Voltage
+1670V
+1520V
Gain
1.0∙107
1.3∙107
Photoelectrons
(pe) per trigger
5.53%
2.91%
Threshold
0.2pe
0.2pe
TTS (FWHM)
(Hamamatsu)
1.91ns
(1.5ns)
3.05ns
(3.5ns)
Early pulses (all
non-gaussian)
2.95%
0.57%
Late pulses
(after photon
pulse peak)
3.13%
3.09%
(5.23kHz)
2.64kHz
(46.3
Hz/cm²)
5.26 Hz/cm²
0.94%
5.12%
Dark count
Dark count per
area
Ionic afterpulses
5/9
Measurements @LNGS:
R6594 vs. R7081
R6594 (5“)
R7081 (10“)
Voltage
+1670V
+1520V
Gain
1.0∙107
1.3∙107
Photoelectrons
(pe) per trigger
5.53%
2.91%
Threshold
0.2pe
0.2pe
TTS (FWHM)
(Hamamatsu)
1.91ns
(1.5ns)
3.05ns
(3.5ns)
Early pulses (all
non-gaussian)
2.95%
0.57%
Late pulses
(after photon
pulse peak)
3.13%
3.09%
(5.23kHz)
2.64kHz
(46.3
Hz/cm²)
5.26 Hz/cm²
0.94%
5.12%
3.88
3.09
Dark count
Dark count per
area
Ionic afterpulses
Peak-to-valley
ratio
5/9
Measurements @ LNGS: Results
Parameters +
Constraints
R6091 (3“) with
1.8“ aperture
R6594
(5“)
R5912
(8“)
R7081
(10“)
ETL9351 (8“)
no. 1732
ETL9351 (8“)
average
Voltage
+1760V
+1670V
+1425V
+1520V
+1500V
≈+1450V
Gain
1.0∙107
1.0∙107
1.3∙107
1.3∙107
1.0∙107
1.0∙107
pe/trigger (npe)
2.21%
5.53%
1.83%
2.91%
4.78%
5.19%
TTS (FWHM) <3.0ns
(manufacturer)
1.89ns
(2.0ns)
1.91ns
(1.5ns)
2.04ns
(2.4ns)
3.05ns
(3.5ns)
2.16ns
2.76ns
EP (all nongauss.) <1%
0.14%
2.95%
1.93%
0.57%
1.23%
0.75% (3σ)
LP (after PP peak) <4%
6.26%
3.13%
2.88%
3.09%
4.08%
7.90% (3σ)
0.192kHz
(5.23kHz)
1.62kHz
2.64kHz
1.72kHz
2.48kHz
12.1
Hz/cm²(eff.)
(46.3
Hz/cm²)
5.1
Hz/cm²
5.3
Hz/cm²
5.3 Hz/cm²
7.7 Hz/cm²
0.14%
0.94%
6.62%
5.12%
2.57%
4.9%
2.04
3.88
2.99
3.09
2.25
2.10
DN
DN/area <15Hz/cm²
Ionic AP < 5%
p/V >2
At the moment no conclusive decision possible:
Need to measure ≈10 PMTs/series and determine limits +
implications on physics from simulations
6/9
Outlook
Outlook: Munich photosensor test stand
• FADC: Acqiris DC282, 10bit, 8 GHz
• Light sources:
• Pulsed ps diode laser:
Edinburgh Instruments EPL-405-mod,
403nm, pulse width 48ps
• Fast LED driven by avalanche diode:
430nm, time jitter (FWHM) <≈1ns
Currently being set up



Done: Light sources implemented and
working, electronics running
Next steps: include fiber and beam
widening optics, finish online analysis
software based on Labview
Plan to study: PMTs: time distribution,
fast AP, ionic AP, pulse shape, dynamic
range, surface scans; also SiPMs
7/9
Outlook: Optical module development
Light Concentrators (Winston Cones)
Borexino
Winston Cone
• MC simulations of light concentrators
with geant4
• Incorporate results into optical model of
detector (geant4 MC) → determine
optimum light concentrator
• Build prototype + scan with laser over
aperture and incident angles
Diploma thesis by Michael Nöbauer
Pressure encapsulations
• Design pressure encapsulations with
FEM pressure simulation, e.g. spherical
shape or conical shape, integrate
Winston Cones + Mu-metal shielding
into design
• Build + test prototypes
Bachelor thesis by German Beischler
8/9
Summary
• Approximate limits on photosensor properties
known → do simulations to refine values
• Have tested promising PMT series from
Hamamatsu @ LNGS → repeat for more
samples of Hamamatsu + ETEL PMTs in Munich
• Also test SiPMs and Hybrid Phototubes
• Have started development of pressurewithstanding optical modules for PMTs
incorporating Winston Cones and Mu-metal
9/9