LENALENADetector developmentDetector development

ANT2010, Santa FeANT2010, Santa Fe2010/09/182010/09/18

Marc TippmannMarc TippmannTechnische Universität MünchenTechnische Universität München

Most relevant topics at the moment

LENA (Low Energy Neutrino Astronomy)Detector layout:

Liquid scintillatorca. 50kt LAB

Inner vessel (nylon)Radius (r) = 13m

Buffer (inactive liquid scint.)Δr =2m

Cylindrical steel tank, 48k PMTs (8“) with Winston Cones (2x area)

r = 15m, height = 100m, optical coverage: 30%

Water cherenkov muon veto5000 PMTs, Δr > 2m to shield fast

neutronsCavern egg-shaped for increased stabilityRock overburden: 4000 mwe

Physics objectives:

Low energy:• Neutrinos from galactic

Supernova• Diffuse Supernova neutrinos• Solar neutrinos• Geoneutrinos• Reactor neutrinos• Indirect dark matter search

Higher energy:• Proton decay• Long-baseline neutrino /

beta beams• Atmospheric neutrinos

Detector constructionDetector construction

Detector construction

LAGUNA:• European site +

design study for a next generation neutrino and p-decay detector

• 7 preselected sites• Proposed

experiments: GLACIER, LENA, MEMPHYS

Includes cavern design study

Detector construction: Cavern construction• New: Rockplan tank +

excavation study for Pyhäsalmi• Based on Technodyne study →

substantial improvements• Worked out excavation process

and extra structures to fulfill safety requirements:

• 2 access tunnels, spherical work tunnel, 1 or 2 new shafts

• Long term rock stability simulations → elliptical horizontal cross-section and kink in vertical cross-section

• → Higher volume for Water Cherenkov detector

Detector constructionTank design

Conventional Steel Tank+ well known, straightforward to build, robust- expensive, single passive layer defense, a lot of

elements and connectionsSandwich Steel Tank+ cost effective, room for cooling, fast install,

high QA/QC, laser welds- a lot of welding, little used solution,

mechanically challenging

Sandwich Concrete Tank+ well known, straightforward to build, robust, improved physics- steel plates and rebar prevent continuous casting, slow to buildHollow Core Concrete Tank+ room for cooling, mechanically strongest, improved physics, quick build- little used solution, active leak prevention may lead to sustained pumping

Liquid Scintillator propertiesLiquid Scintillator properties

• Extensively covered last year on ANT09 by Michael Wurm → only new results

• Liquid Scintillator properties are essentially understood + known

• Only particular measurements remain to be done• Started to repeat measurements with higher precision

10m

• Already measured with a 1m scintillator tube (10nm accuracy) + 10cm cell (1nm) → transparency considerably increases with wavelength → need longer tube

• → New experiment with ≈10m tube length• Is being set up at new Munich underground lab (≈ 10mwe rock

overburden)• All parts ordered, most have arrived• Should be able to start measurements within the next months

Wavelength (nm)

Atten

uatio

n le

ngth

(m)

Liquid scintillator propertiesAttenuation length vs. wavelengthMichael Wurm

Martin Hofmann

1m

Liquid Scintillator propertiesDecay time constants

• Paolo Lombardi has set up a new experiment in Milan

• Measured time behavior of different scintillators (PC, LAB, DIN) with varying PPO concentration

• → Cross-check with Munich experiment possible

• Measurements on LAB in both experiments in good agreement in some variables, deviation in others → maybe due to different manufacturers / batches →will study this further

Paolo Lombardi, LENA Meeting 2010-07-05

Liquid Scintillator propertiesEmission spectra

• Measurements done in Perugia by Fausto Ortica and Aldo Romani

• → Cross-check with Munich experiment possible

• Very good agreement of results for LAB with 1.5 resp. 2g/l PPO

Paolo Lombardi, LENA Meeting 2010-07-05

Teresa Marrodan, PhD thesis

Photo sensorsPhoto sensors

Photo sensors: Photo sensor requirementsPMT timing behavior

Normal Pulses

Early Pulses

Pre-Pulses

Late Pulses

Transit Time Spread(FWHM, spe)

Dark Noise

• Area Inner Detector: 10430 m²Targeted optical coverage: 30% → 3130 m² effective photosensitive area

• PMTs probably the only photosensor type • Meeting the physical requirements• Having a low enough cost /(area*photon

detection efficiency)• Durable for at least 30 years AND• Utilizable until start of construction

Important properties: Transit time spread, afterpulsing, gain, dynamic range, area, quantum efficiency, dark noise, peak-to-valley-ratio, early + pre-pulsing, late pulsing, pressure resistance, long term stability, low radioactivity, price

Photo sensors: Photosensor requirements

Photo sensors: Photosensor requirementsNecessary parameters for PMTs

Diameter Transit Time Spread (FWHM)

Ion Afterpulses,Brems-strahlung AP

Dark Noise

Dynamic Range (pe)

Gain Number PMTs in Inner Detector (using 2x Winston cones )

3“ <3ns <1%(if not less!)

<0.75 kHz

1 to > 10 some 106

343,000

5“ “ “ <2kHz 1 to > 40 “ 124,000

8“ “ “ <5kHz 1 to >100 “ 48,000

10“ “ “ <8kHz 1 to >150 “ 31,000

Photo sensors: PMT characterizationSelection of feasible PMT models for LENA

• Manufacturers available for 100k+ PMTs:• Hamamatsu Photonics • Electron Tubes Enterprises Ltd.

• Study most promising PMTs with diameters from 3“-10“ • Measured until now: – Hamamatsu: R6091(3“), R6594(5“), R5912(8“) and R7081(10“)– ETEL: 9351(8“)

• Borexino PMT testing facility @LNGS:• Excellent time resolution:

410nm laser diode light source, pulse FWHM <30ps, trigger output jitter <100ps; electronics jitter ≈45-90ps → total time resolution <140ps

• Can measure up to 32 PMTs simultaneously

Photo sensors: PMT characterization

• Repaired + reactivated setup• Further improved setup:• Use second channel to measure

fast AP up to ≈25-30 ns after primary pulse, triggered by pulse in first channel

• Low noise preamp near PMT → increased p/V by a factor of 2

5“

10“

R6594 (5“) R7081 (10“)

Voltage +1670V +1520V

Gain 1.0 10∙ 7 1.3 10∙ 7

pe/trigger (npe)

5.53% 2.91%

TTS(FWHM) (acc. to HP)

1.91ns (1.5ns)

3.05ns (3.5ns)

EP (all non-gaussian)

2.95% 0.57%

LP (all non-gaussian)

34.16% 42.90%

LP (after NP peak)

3.13% 3.09%

Photo sensors: PMT characterizationResults: Comparison R6594(+) vs. R7081(+)

Photo sensors: PMT characterization - Comparison PMTs

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 10∙ 7 1.0 10∙ 7 1.3 10∙ 7 1.3 10∙ 7 1.0 10∙ 7 1.0 10∙ 7

pe/trigger (npe) 2.21% 5.53% 1.83% 2.91% 4.78% 5.19%

TTS (FWHM) (manufacturer)

1.89ns(2.0ns)

1.91ns (1.5ns)

2.04ns(2.4ns)

3.05ns (3.5ns)

2.16ns 2.76ns

EP (all non-gaussian) 0.14% 2.95% 1.93% 0.57% 1.23% 0.75%(3σ)

LP (all non-gaussian) 27.29% 34.16% 55.01% 42.90% 8.70% -

LP (after NP peak) 6.26% 3.13% 2.88% 3.09% 4.08% 7.90%(3σ)

DN 0.192kHz (5.23kHz) 1.62kHz 2.64kHz 1.72kHz 2.48kHz

DN/m² 120.9 kHz/m²(eff.)

(462.6 kHz/m²)

50.5 kHz/m²

52.6 kHz/m²

53,0 kHz/m²

76,5 kHz/m²

Ion AP 0.14% 0.94% 6.62% 5.12% 2.57% 4.9%

p/V 2.04 3.88 2.99 3.09 2.25 2.10

Photo sensors: PMT characterization Improve + extend Munich PMT testing setup

PMT test setup at TUM, Garching (currently)• FlashADC (10bit, up to 8 Gigasample/s =

125ps time resolution, 4 channels) → excellent

• Currently using LED (430nm peak-wavelength) with moderate relaxation time (≈5-10ns) driven by 5ns FWHM voltage pulse

→ bad

→ Build in fast light pulser developed by George Korga: fast LED driven by Avalanche Diode -> total time jitter FWHM ≈1ns or lower

Medium term: build in ps laser diode → time jitter ≈30ps

→ Confirm results from Italy→ Can measure in addition pulseshape + fast

afterpulses (Δt<30ns) + prepulses Status: coincidence running; working with

two students on improving readout + evaluation software

Photo sensors: PMT characterizationHQE measurements

• Measured Hamamatsu super-bialkali PMTs (~34% peak-QE): R6594-SEL, R5912-SEL, R7081-SEL

• → Direct comparison with standard photocathode PMTs measured @ Borexino PMT testing facility possible

• (Another) experimental setup of Paolo Lombardi in Milan to characterize PMTs:• Picosecond laser (405nm)• 8bit 1GS/s FADC

Paolo Lombardi, LENA Meeting 2010-07-05

Photo sensorsWinston Cones

• Attach Compound Parabolic Concentrators („Winston Cones“) to increase effective area of PMTs by a factor of 2-8(!) → increases number of detected photons / MeV deposited → increased resolution

• Limits field of view by introducing an acceptance angle (conservation of etendue) → can be used to limit field of view to fiducial volume

• …coming soon: study influence on detector performance with the Geant4 Monte Carlo simulation of LENA (software development finished + working)

Borexino Winston Cone

CTF Winston Cone

Photo sensorsPressure encapsulations

• Pressure at tank bottom might be too high for PMT glass envelopes →

• a) Try if thicker glass envelope (4mm) fulfills pressure tests

• b) Develop pressure encapsulations → • Can use standard PMTs• Integrate Winston Cones + µ metal

shielding into design• Starting points for development e.g.

Borexino encapsulation with pressure-withstanding window instead of thin PET window with pressure-resistant window in front

• Development will commence soon

ElectronicsElectronics

Electronics: PMT arrays• Employ PMT arrays with central

on-site front-end electronics on chip → Reduce number of channels (only 1

cable for data + voltage); however voltage not adjustable for individual PMTs after installation + can read out pulse shape only for sum of PMT channels

• Currently under development in PMm² project

• PICS collaboration between LENA + MEMPHYS

• → can use existing R&D of PMm² (3 years) for LENA!

• PMm²: 16 PMs(12“) + frontend electronics (PARISROC)

J.E. Campagne, LENA - PMm² meeting 07/04/2009

• Triggerless• Individual channels• Charge + time measurement• Variable gain of preamplifier• Common HV for PMs• 1/3pe 100% efficiency• 1ns time resolution• 16 trigger channels or 1 OR-trigger-output• 2 gains per channel (not showed here):

0-10pe & 0-300pe• Scaleability

Electronics: PMT arraysPMm² frontend electronics: PARISROC

Electronics: PMT arrays• Advantages: • Data transfer digital → less attenuation• Lower cost (less cables, voltage in cables smaller,

bundled frontend electronics reduces data processing cost/channel)

• Disadvantages:• Same HV for each PMT within module → counter measures: partial compensation via individual gain adjustment, combine similar PMTs for a module

• Different physical requirements for PMT Arrays → adopt R&D of PMm² as far as possible

+ adapt setup where neccessary

SoftwareSoftware

SoftwareTracking in Liquid Scintillator Detectors

J. Learned, arXiv/0902.4009, J. Peltoniemi, arXiv/0909.4974

• Light front generated by GeV particles resembles a Cherenkov cone → directionality → can use arrival time of first photons on PMTs and total photon count for tracking

• → Can be used for p decay, neutrino beams and atmospheric neutrinos

• Have developed two event reconstruction programs for tracking:

• „Scinderella“ by Juha Peltoniemi

• Tracking script for the Geant4 LENA optical detector model by Dominikus Hellgartner

• Detector simulation software based on Java developed by Juha Peltoniemi

• Can do both event simulation and event reconstruction

• Event simulation → record observation time of photons in PMTs

• Track reconstruction by comparing light pattern produced by test track with that of track from simulation → minimalization of deviation

Software: Tracking in Liquid Scintillator Detectors: „Scinderella“

• Single-Particle Tracks (leptons, CC QES): excellent reconstruction

• Multi-Particle Vertices (deep inelastic neutrino scattering creates pions, 1-5GeV): new reconstruction algorithm fits a superposition of the light fronts generated by MC sample tracks to the overall PMT signal• → for ≤ 3 pions good track

reconstruction at ≤ 5% E resolution possible

• → LSD is good tracking detector at E > 1GeV: excellent flavour recognition, E resolution typically < 5%, very good for neutrino beams: sin²(2ϑ) > 10-2 – 10-3 if not lower

• If pulse-shape of PMT signals available even better

J. Peltoniemi

Reco of 4GeV deep-inelastic sample event

Software: Tracking in Liquid Scintillator DetectorsTracking script for Geant4 optical model

• Developed by Dominikus Hellgartner based on work done by Michael Wurm on tracking in Borexino

• Procedure: minimize log-likelihood value of photon pattern depending on all track parameters

• → Look at even lower energies than 1GeV:

• First preliminary results:• a) 100 500MeV single-track muons: very

good track reconstruction with <≈1+/-2cm position uncertainty and 0.1+/-0.1ns time uncertainty for the starting point and 2.5° direction deviation

• b) 100 750MeV single-track electrons: all uncertainties comparable to muon events, however one problem occurring: for some events, the direction is reconstructed with wrong sign → starting point at end of track → outliers; are working on this right now

Dominikus Hellgartner

Software: Tracking in Liquid Scintillator DetectorsProof of principle: Borexino

• Reconstructed tracks from CNGS beam in Borexino

• No simulation: real data!

• Borexino is actually a low E calorimetry detector; not optimized for tracking at all

• LENA will be designed for tracking capability

Michael Wurm

SummarySummary• Pyhäsalmi site study finished → elliptical cavern, Pyhäsalmi site study finished → elliptical cavern,

steel or concrete tanksteel or concrete tank• Liquid scintillator properties mostly known, setting Liquid scintillator properties mostly known, setting

up attenuation length precision measurement at up attenuation length precision measurement at the momentthe moment

• Photo sensor: 5“-10“ PMTs (which type will be Photo sensor: 5“-10“ PMTs (which type will be decided shortly) with Winston Cones and pressure decided shortly) with Winston Cones and pressure encapsulationsencapsulations

• Bundle PMTs to arrays to save channelsBundle PMTs to arrays to save channels• Geant4 detector simulation is running, have to Geant4 detector simulation is running, have to

measure last missing properties for optical modelmeasure last missing properties for optical model• Liquid Scintillator Detectors are actually quite good Liquid Scintillator Detectors are actually quite good

at trackingat tracking

Backup slidesBackup slides

Detector constructionExcavation

Scattering Length ResultsScattering Length Results no hints for Mie-scat. anisotropic scattering in good agreement with Rayleigh expectation correct wavelength- dependence found literature values for PC, cyclohexane correctly reproduced

Results for =430nm

LS = 22±3 mLS = 22±3 m

after purification in Al2O3-column

Michael Wurm

Timo Lewke, Jürgen Winter

Gamma Quenchinglight output of low-energeticelectrons (E<200keV) by small-angle Compton scattering…in progress

scintillator sample

Liquid Scintillator propertiesQuenching factors

Proton Quenchingusing neutron recoils(AmBe-source, n-generator)…coming soon

Proton decayLarge impact on proton decay (into K+) detection efficiency:

Signal of kaon (=13ns) and of its decay products (mostly muons) must be separated by rise time analysis

Kaon Muon

Background Source:Atmospheric Muon-Neutrinos

Efficiency ranges from 56% to 69%for typical rise times of 7 to 10 ns

Proton decay

Single-Particle Tracks• excellent flavour recognition• Positional accuracy: a few cm• Angular accuracy: a few

degrees• initial neutrino energy +

momentum can be determined at 1%(?) accuracy from lepton track (CC QES)

Multi-Particle Vertices• - deep-inelastic scattering of

neutrinos creates pions (1-5 GeV) • - new reconstruction algorithm

fits a superposition of the light fronts generated by MC sample tracks to the overall PMT signal

• - resolution of vertices featuring ≤ 3 ‘s is possible at % accuracy

• - recoil protons/neutrons quenched, not invisible, allowing a calorimetric measurement of the event energy deposited.

• - time-resolved response of individual PMTs needed for optimum result

Software: Tracking in Liquid Scintillator Detectors: „Scinderella“

Software: Tracking in Liquid Scintillator DetectorsTracking script for Geant4 optical model

• Developed by Dominikus Hellgartner based on work done by Michael Wurm on tracking in Borexino

• Procedure: • For muon: separate track signal + decay signal: look for

second peak in detected photons vs. time -> time cut• Determine start values for fits:

• Energy → from number of photons of track; barycenter fit → position on track; first PMT hit → crude direction: vertical or horizontal

• Vertical: Fit point-like source from first hit times for PMT-ring containing minimum hit time PMT → starting point → with barycenter fit direction → with energy track length → track

• Horizontal: TOF-correction to barycenter → direction from most negative first hit times; table of position of charge barycenter vs track E (input from other simulations) → with energy track

• Main fit: minimize log-likelihood value depending on all track parameters

• → Look at even lower energies than 1GeV:• First preliminary results:• a) 100 500MeV single-track muons: very good track

reconstruction with <≈1+/-2cm position uncertainty and 0.1+/-0.1ns time uncertainty for the starting point and 2.5° direction deviation

• b) 100 750MeV single-track electrons: all uncertainties comparable to muon events, however one problem occurring: for some events, the direction is reconstructed with wrong sign → starting point at end of track → outliers; are working on this right now

Dominikus Hellgartner

Requirements on PMTs in LENARequirements on PMTs in LENA

Other types of photosensors

• Avalanche Photodiode (APD): solid state equivalent to PMTs; price/area too high; Dark Noise very high, if not cooled; low amplification

• SiPM: array of small APDs; excellent tts (FWHM < 0.5ns), excellent energy resolution, high QE(?), immense cost/area; huge dark count (some 100kHz up to several MHz)

• Cupid/ Hybrid Photo-Detector: Photocathode just like in PMTs, e- however focussed on APD in center instead of dynode chain; problems with huge DN? Still working on fixing that

• Microchannel Plate (MCP): Photocathode, e- accelerated along very thin etched channels perpendicular to cathode, coated with metal on inside, thickness of coating varies along axis -> increasing voltage along flight path, e- crashes on walls + knocks out more e- -> amplification

Other types of photosensors• Quasar: Photocathode, solid scintillator

block in center with a small PMT looking at it; apply very high voltages (typ.25-30kV) -> e- creates scintillation light in crystal -> light signal on PMT advantages: small jitter even for large photocathode area, excellent energy resolution, …, price=? Already used in BAIKAL, however needs further development

• Hybrid-Gas Photomultiplier: photocathode in vacuum, e- accelerated through mebrane into Thick Gas Electron Multiplier (THGEM) -> accelerated through holes in metal-covered plate, different voltage on upper+ lower side -> very high field inside holes -> e- scatters off gas atoms -> produces further e- -> amplification; use several THGEMs in series for higher amplificationstill under development, needs several more years to be ready for production

Photomultiplier Tubes (PMTs)Principle of operation

• Extremely sensitive light detectors capable of detecting single photons

• Photon → photo electron(pe) → amplified by ≈10^7 in dynode chain

• Gain = amplification factor

• Afterpulse: delayed additional pulse caused by the primary pulse• Ion Afterpulses:

typically 0.3-15µs later

• Bremsstrahlung Afterpulses:typ. 30-60ns later

• Dark Noise: electrons emitted from cathode without incident photon; mostly thermionic emission

PMTsOcurring effects + basic parameters

Ion Afterpulses

Dark Noise

Primary Pulses

(Next laser pulse)

• Single photo electron (spe) spectrum: 3 components: normal pulses, underamplified pulses + noise

• Peak-to-valley-ratio (p/V): ratio between value of maximum and valley

PMTsOcurring effects + basic parameters

spe (normal pulses)

2 pe

Peak

Valley

under-amplified

pulses

noise

PMTsVoltage behavior

• Two different modes of applying voltage:a) Photocathode at ground potential → positive voltage on anode

→ need capacitor to separate DC voltage from electronicsb) Negative voltage applied to photocathode → anode at ground

potential → signal can be sent directly to electronics• Advantage: faster• Disadvantage: DN higher

• Dynamic Range: number of photons incident at the same time on the cathode, which can be detected

• Raise voltage → gain rises, transit time decreases, jitter decreases, however: AP rise, DN rises if voltage is very high (field emission), dynamic range decreases→ find optimum working point

PMTs in LENA• Transit time spread must be low

→ tracking• Bremsstrahlung Afterpulses (fast

AP) can blur out proton decay coincidence

• Ion Afterpulses (slow AP) can prevent position reconstruction of neutrons → decreases detection rate of cosmogenics (C11): C11 is main background for CNO-ν-flux

Michael Wurm, TUM, LENA - PMm² meeting 07/04/2009

PMTs in LENA• High Dark Noise: random coincidences of

DN pulses + bad for tracking; DN approx. Q cathode area

• Gain must be high enough or part of pulses overlaps with noise in spe spectrum → less pulses usable

• Dynamic range: Detector must be able to detect single photons as well as HE events (muon, proton decay)

Assuming 1GeV event, 500pe/MeV, illuminating only 10% of PMTs →

1pe - 1700pe/(m² effective photosensitive area) = 1pe – 100pe for 8“ PMT with 2x Winston Cone

upper boundary x10 if only 1% illuminated

• p/V: the bigger it is, the better spe events can be distinguished from noise

PMTs in LENA• EP + PreP + maybe LP bad for tracking (uses

first pulses = first photons)• Area per sensor:

Smaller → better tracking, dynamic range of detector increases, transit time spread smallerBigger → less sensors + channels → cost/area lower (if not too big)→ generally sensor area as small as

affordable • Quantum efficiency: higher → less PMTs

needed for same energy resolution + threshold

• Pressure resistance: At least 10 (100m head of liquid scintillator) +1 (vacuum in tube) + 3 (safety margin for implosions) = 14bar

at the moment no PMTs meet the pressure requirements → maybe use encapsulations for lower PMTs

Measurements at the Measurements at the Borexino PMT testing facility Borexino PMT testing facility

@LNGS (INFN), Italy@LNGS (INFN), Italy

Measurements @LNGSSetup + Measurements

• Setup can measure:• Transit time (TDC) → TTS, EP, PreP, LP• AP/Primary Pulse (PP) transit time (MTDC) →

slow AP (+some fast AP), DN, pe/laser trigger (npe)

• In second channel: transit time of first AP (TDC) → fast AP

• For both channels: charge spectrum (ChargeADC) -> p/V

Measurements:• Measured all PMTs with positive + negative

HV at a gain of 1·107

• Find new operating point for LENA → Sampled over complete reasonable voltage

range for pos. voltages → scanned PMT properties over

complete feasible range of gain for single photon electrons

• Also: • Developed fast LED light source

with emission time spread (fwhm) <≈ 1ns

• Measured R6233-100SEL: 3“ UBA photocathode, max. QE ≈43%(!)

• Measured several ETL9351 PMTs for comparison → gave one to Paolo Lombardi to calibrate new flash ADC setup in Milano → planned to exchange data of measured PMTs; e.g. R7081 ↔ R7081-100SEL (UBA)

• Evaluated up to now: Runs with ≈107 gain + positive voltage

Measurements @LNGSMeasurements

Borexino PMT testing facilityBlock diagram - original configuration

R6594 (5“) R7081 (10“)

Voltage +1670V +1520V

Gain 1.0 10∙ 7 1.3 10∙ 7

npe 5.53% 2.91%

DN (5.23kHz) 2.64kHz

DN/m² (462.60 kHz/m²)

52.59 kHz/m²

Ion AP 0.94% 5.12%

Measurements @LNGSResults: Comparison R6594(+) vs. R7081(+)

R6594 (5“) R7081 (10“)

Voltage +1670V +1520V

Gain 1.0 10∙ 7 1.3 10∙ 7

npe 5.53% 2.91%

DN (5.23kHz) 2.64kHz

DN/m² (462.60 kHz/m²)

52.59 kHz/m²

Ion AP 0.94% 5.12%

Measurements @LNGSResults: Comparison R6594(+) vs. R7081(+)

R6594 (5“) R7081 (10“)

Voltage +1670V +1520V

Gain 1.0 10∙ 7 1.3 10∙ 7

npe 5.53% 2.91%

p/V 3.88 3.09

Measurements @LNGSResults: Comparison R6594(+) vs. R7081(+)

Measurements @LNGS Preliminary Results• Most promising candidate –

judging from only one sample each:

Hamamatsu R6594 (5“ diameter) using positive HV (dark noise rate much higher for negative HV): • transit time spread 1.9ns, total

afterpulse rate 0.9%, peak-to-valley ratio 3.9

→ Need more samples to be able to determine mean parameters