1. Multi PMT
P.Kooijman
Just 1

2. Separation 1 photon (Background) from 2 photons (Signal)
Why Multi-PMT?
Coincidences
Separation 1 photon (Background) from 2 photons (Signal)
Purity: 2 PMs ≥ 2 Photons guaranteed 100%
Efficiency: 7 PMs look at signal – only 14% of all 2pe are in 1 tube
86%
14%

3. Non-grouped PMs are background
signal
background

4. Can easily customize angular acceptance
MEASURE the background from atm. Muons
MEASURE showers on tracks
Solid angle 45deg->90deg 3x 0deg->45deg
Large Photocathode area in one sphere
Less connectors/cm2
No magnetic shielding
Failure not full OM
Less collected charge / tube – aging (0.5 C/10 years)

5. Further advantage:
Ease of assembly
Prepare GEL “contact lens” in advance
Place tubes in styrofoam holder
Stick on contact lens
Cover with silicon glue
Put glass hemisphere over
Press outward
Front shaped to sphere – max 2-3 mm gel
Test gluing directly to glass sphere – pressure test

6. Readout:
options:
TOT (low ph not important because photon counting)
Custom ASIC (LP)
…….

7. Plans:
Test New Photocathode PM (Herbert)
Full system test for
Long term stability
Heat
Gain stability
Coincidence ideas
Tests of gluing / putting together
Pressure tests
Deployment

9. 2 photon 40% probability 32 m to 41 m
1.23=1.7 in volume