TDR of PMT Timing issues Gain Slope H

TDR of PMT: Timing issues • Gain Slope H d(log. GS)/d(log. HV): 6. 5<H<8 • HV at nominal gain 3 E 6 (difference between Nominal HV and NHVp -pulse mode- are expected) • Dark rate: 2 k. Hz @ 0. 3 spe • Prepulses: <1 % • Afterpulses 1 (early): < 2% • Afterpulses 2 (late): < 10% • Delayed pulses: < 3. 5 % • Transit Time (difference among PMTs): < 7 ns • Transit Time Spread < 5 ns 24/01/2017 G. Riccobene

TDR of PMT: Timing issues • PMT timing characteristics are a key ingredient to optimise track reconstruction: Transit Time (TT), TT Spread (TTS) • TT is a function of HV: HV tuning procedure is crucial: on shore and offshore (Alex) TT is not measured in KM 3 Ne. T: we measure the time delay between a photon hit and the hit time recorded by the CLB (time calibration procedure in dark room: laser and 40 K). This includes also the front-end electronics delay • TTS: is one of the uncertainities that enters into the track reconstruction, unavoidable: need to check that TTS is compliant with tender specs. 24/01/2017 G. Riccobene

TDR of PMT: Timing issues • TTS: The contribution from the photomultipliers for KM 3 Ne. T is less than 2 ns • FWHM<4. 5 ns <2 ns Letter of Intent of KM 3 Ne. T 2. 0 ar. Xiv: 1601. 07459 Journal of Physics G: Nucl. and Part. Phys. 43 (8), 084001, 2016 24/01/2017 G. Riccobene Example of typical time distribution for TTS measurement. In this case = 1. 4 ns Couretsy of Jd. D. Zornoza

© Low Cost TX/RX SFP √ © SFP RJ 45 adapter √ External network Dark Box Setup DAQ PC White Rabbit Master switch © © √ √ monitor Laser splitter 31 x 31 PMTs Octopuses and 31 cable extenders Broadcast Octopuses and 31 cable extenders Laser splitter 31 x Laser CLB 1© √ data CLB 2© data √ Optical splitter 50/50

Dark Box Setup • “CLB 1” with PPS signal modified (output is LEMO, signal is 20 k. Hz trigger, synchronized with PPS). • “CLB 2” standard • Laser Pilas Advanced Laser diodes • White rabbit switch, SFP avago & comm fibers • Extended cables for the PMT bases • Calibrated Optical fibers to each PMT (equalized time delay). 24/01/2017 G. Riccobene

TDR of PMT: Timing issues All the time delays due to electronics cabling and fiber optics network are measured: The Dark Box can effectively measure the TT and the TTS of PMTs But only TTS are recorded 24/01/2017 G. Riccobene

• • • delta T for all Octopus channels (same PMT and setup) Large-Small mean difference is 780 ps Max difference 1. 4 ns LARGE SMALL PMT+Laser+CLB I, PMT + CLB II 24/01/2017 G. Riccobene

Delay (TT proxy) dependence from HV 24/01/2017 G. Riccobene

TDR of PMT: Timing issues HV tuning and timing The HV tuning aims equalising the gain (G) of all PMTs to the reference value of 26. 4 ns for 1 spe (corresponding to G=3 x 106) PMT amplitude doesn’t enter strongly in track reconstruction, so far. But amplitude will be fully exploited asap. Photon Hit time is a key parameter in track reconstruction, so we have to determine it precisely -> time calibration procedure 24/01/2017 G. Riccobene

TDR of PMT: Timing issues Time calibration procedure: Green/Blue box: Intra-DOM delays 40 K Dark Room: a) HV tuninig b) intra-DOM delays (glass 40 K) [L 0 or L 1 Runs] c) Inter-DOM time calibration (laser source and reference PMTs) [L 1 Runs] See TDR on Time Calibration and DU Time Calibration Procedure : KM 3 Ne. T_CALIB_2016 (M. Bowhuis) In Situ: a) Periodic LED beacon and 40 K calibration b) HV tuninig intra-DOM delays (sea 40 K) [wrt reference PMTs with HV unchanged] Inter-DOM time calibration with LED beacons [L 0 Runs] Procedure for the estimation of the time shift due to high voltage tuning (A. Creusot) 24/01/2017 G. Riccobene

TDR of PMT: Timing issues Dark Room Measurement: Scheme of Inter-DOM Calibration Extracted from Time Calibration TDR 24/01/2017 G. Riccobene

TDR of PMT: Timing issues Dark Room Measurement: Inter-DOM Calibration Extracted from Time Calibration TDR All DOMs superimposed Delay or reference PMT subtracted 24/01/2017 G. Riccobene

TDR of PMT: Timing issues Dark Room Measurement: Intra-DOM time calibration (glass 40 K) Extracted from Time Calibration TDR 24/01/2017 G. Riccobene

© Low Cost TX/RX SFP √ CH 59 SFP © √ © SFP RJ 45 adapter √ External network Possible upgrade of Green Box Setup DAQ PC White Rabbit Master switch © © © √ √ √ Reference CLB data 10 d. B Laser DOM optical test Box 1 99 Optical splitter 99/1 FFC-C 161 PB 115 Broadcast (CH 59) DOM © √ data