1. 1 HERSCHEL: PMT status report The order to replicate PCB for divider of R1828-01 has been launched on 11-02-2014 a) digital file for production(promised by 14-03-2014) b) production of PCB(not started, on critical path) Prototype base modifications a) old base like for BLS counters(ready, waiting for R1828 delivery 2pieces) b) new base for modified voltages sequence (waiting for ordered components - FARNELL) Stand for study of PMTs with LEDs a) pulsing LED with signal recording(in use, scope LeCroy WaveRunner 104MXi-A) b) permanent illuminating LED (scheduled for coming week-end) Cosmic stand with prototype counters and PMTs a)trigger counters (ready) b)prototype counters(to be assembled during next week - Raphael) c)oscilloscope “LeCroy WR 104MXi-A” (ready – 350CHF/month) Two LEDs to be embedded inside scintillator – transparency monitoring! (to be checked with prototype) 30 old PMTs “56AVP” available from UA1thanks to Raphael and Heinrich!!! Extensively checked last few days(first results available) RD 21/03/2014

2. 2 HERSCHEL: PMT status report RD 21/03/2014 STAND for PMT TESTS with LEDs base for test R1828 old resistive base for 56AVP (UA1) scope LeCroy WR 104MXi-A (1GHz, 4 ch., WindowsXP ) NIM crate with LED driver and trigger logic HV power supply and current monitoring All 30 PMTs “56AVP” passed check : all are alive and working relative photocathode quantum efficiency measured Gain = A (HV) α measured to be ~12.2

3. 3 HERSCHEL: PMT status report RD 21/03/2014 STAND for COSMIC TESTS Prototype scintillator counter

4. 4 HERSCHEL: PMT status report RD 21/03/2014 Two LEDs allow plastic transmittance monitoring LED – 1 LED – 2 Aim – to monitor ratio LED1/ LED2 during shut-down Vacuum pipe

5. 5 HERSCHEL: PMT status report RD 21/03/2014 OLD PMTs from UA1 For the same LED brightness and HV=1850V the response varies from min - 35mV max – 729mV All 30 “56AVP” are alive – responding to LED pulse.

6. 6 HERSCHEL: PMT status report RD 21/03/2014 OLD divider from UA1 Magnetic steel shielding with 2 LEDs on top Mu-metal screening Electro-static screening @photocathode HV Pure resistive divider Average pulse height.vs. HV (two LED intensity settings) 56AVP #22544

7. 7 HERSCHEL: PMT status report RD 21/03/2014 Comparison of 30 PMTs “56AVP” Pulse height spread for fixed LED intensity and same HV=1850V no stability guarantee, few minutes averaging

8. 8 HERSCHEL: PMT status report RD 21/03/2014 Single Photo-electron spectra PMT 56AVP # 49667 (~1M sweeps, @2500V) LED Pedestal

9. 9 HERSCHEL: PMT status report RD 21/03/2014 Outcome: Divider production under large concern Stand for prototype testing ready by next week 56AVP could be considered as a back-up solution (more study required) Dividers from UA1 to be investigated (if available) COMPASS group from Mainz asked to search spare parts for divider housing LEDs worth to embed in to scintillator to be able to monitor its transparency The coming weeks are crucial to finalize the baseline solution for counters.