1. PMT characterisation for the KM3NeT Project
Oleg Kalekin
Representing the KM3NeT Consortium
VLVnT 2009, Athens

2. Photomultipliers for KM3NeT optical 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 R5912
ET Enterprises 9354
3-inch: Hamamatsu R prototype
ET Enterprises prototype
O.Kalekin, VLVnT 09, Athens,

3. 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
O.Kalekin, VLVnT 09, Athens,

4. Quantum efficiency All dynodes and anode connected electrically
and at a few hundred
volts relative to the cathode
No amplification
100% collection efficiency
Photocathode current
measured
Comparison with absolute
calibrated photodiode
Photocathode QE
O.Kalekin, VLVnT 09, Athens,

5. Quantum efficiency
O.Kalekin, VLVnT 09, Athens,

6. Scan of PMT surfaces X-Y scanner Step motors, min step 7.5 μm
Optical fibre 1mm diameter
LED pulses, ~10 ns FWHM
A few tens photoelectrons (phe)
A few hundred pulses in each measured point
Charge and peak position recorded
Effective area:
Integral of scanned points with weights
S= π∙ΔrΣf∙r
Transit time spread over surface:
Arrival time distribution weighted
with radius and charge
O.Kalekin, VLVnT 09, Athens,

7. Effective area 27sq.cm Effective diameter 58mm
O.Kalekin, VLVnT 09, Athens,

8. Transit time spread
TTS=0.73ns
O.Kalekin, VLVnT 09, Athens,

9. Effective area and TTS Measured eff. photocathode Specified photocath.
(A few tens of photoelectrons signal)
Measured eff. photocathode Specified photocath.
TTS, ns Area,cm Diameter, mm diameter, mm R
9354KB
R6233MOD
9822B
O.Kalekin, VLVnT 09, Athens,

10. TTS of R6233MOD
R6233 modified on demand of the KM3NeT from flat input window
to plano-concave
Further modification
needed/planed:
Convex-concave window
O.Kalekin, VLVnT 09, Athens,

11. Single photoelectron jitter
ECAP test bench for PANDA experiment
Picosecond laser, 20ps FWHM
LeCroy TDC 2228A, 50ps/ch
LeCroy ADC 2249A, 0.25pC/ch
PMTs illuminated at single photoelectron level
O.Kalekin, VLVnT 09, Athens,

12. Single photoelectron jitter
Time RMS = 1.45ns
Long noise tail
O.Kalekin, VLVnT 09, Athens,

13. Single photoelectron jitter
Tail ns
Non single phe
Time RMS = 1.45ns
Gauss sigma=0.55ns
FWHM=1.5ns
Long noise tail
O.Kalekin, VLVnT 09, Athens,

14. Single photoelectron jitter
single phe TTS, ns
Gauss sigma FWHM R R
9354KB
R6233MOD
9822B
O.Kalekin, VLVnT 09, Athens,

15. Single photoelectron jitter
Peak at
23-30 ns
Real late peaks
O.Kalekin, VLVnT 09, Athens,

16. Summary The most part of evaluated PMTs meets KM3NeT specifications
Variations of parameters observed
Detailed calibration of the PMT’s subset will be needed
O.Kalekin, VLVnT 09, Athens,