pmt characterisation for the km3net project

PMT characterisation for the KM3NeT Project

Oleg Kalekin

Representing the KM3NeT Consortium

VLVnT 2009, Athens

14.10.2009

Photomultipliers for KM3NeToptical modules

3 (2+1) main options for optical modules (OM) in the KM3NeT

• OM with 1 photomultiplier tube (PMT) 10 or 8 inch diameter• OM with two 8-inch PMTs• Multi-PMT OM with 31 three-inch PMTs

PMTs considered as candidates

10-inch: Hamamatsu R7081

8-inch: Hamamatsu R5912ET Enterprises 9354

3-inch:Hamamatsu R6233 - prototypeET Enterprises 9822 - prototype

O.Kalekin, VLVnT 09, Athens, 15.10.2009

PMT parameters

Quantum efficiency (QE)

Effective photocathode area

Time resolution – Transit time spread (TTS)

Amplification

Dark rate

Peak to valley ratio

All parameters are measured on the PMT test bench At the Erlangen Centre for Astroparticle Physics


Quantum efficiency

All dynodes and anode connected electricallyand at a few hundred volts relative to the cathode

No amplification

100% collection efficiency

Photocathode current measured

Comparison with absolutecalibrated photodiode

Photocathode QE


Quantum efficiency


Scan of PMT surfaces

X-Y scanner

Step motors, min step 7.5 μmOptical fibre 1mm diameterLED pulses, ~10 ns FWHMA few tens photoelectrons (phe)

A few hundred pulses in each measured pointCharge and peak position recorded

Effective area: Integral of scanned points with weightsS= π∙ΔrΣf∙r

Transit time spread over surface:Arrival time distribution weighted with radius and charge


Effective area

Effective area27sq.cm

Effective diameter58mm


Transit time spread

TTS=0.73ns


Effective area and TTS(A few tens of photoelectrons signal)

Measured eff. photocathode Specified photocath.TTS, ns Area,cm2 Diameter, mm diameter, mm

R7081 1.0 380 220 220

9354KB 0.62 264 183

R6233MOD 3.1 35 67 70

9822B 0.73 27 58


TTS of R6233MOD

R6233 modified on demand of the KM3NeT from flat input window

to plano-concave

Further modification

needed/planed:

Convex-concave window


Single photoelectron jitter

ECAP test bench for PANDA experiment

Picosecond laser, 20ps FWHMLeCroy TDC 2228A, 50ps/chLeCroy ADC 2249A, 0.25pC/ch

PMTs illuminated at single photoelectron level



Time RMS = 1.45ns

Long noise tail



Tail 17.5-19ns

Non single phe

Time RMS = 1.45ns

Gauss sigma=0.55ns

FWHM=1.5ns

Long noise tail



single phe TTS, ns

Gauss sigma FWHM

R7081 1.2 3.1

R5912 0.57 1.4

9354KB 0.67 1.6

R6233MOD 1.5 3.2

9822B 0.55 1.5



Peak at

23-30 ns

Real late peaks


Summary

The most part of evaluated PMTs meets KM3NeT specifications

Variations of parameters observed

Detailed calibration of the PMT’s subset will be needed


pmt characterisation for the km3net project

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