Experimental set-up

1. s = 40ps s = 37ps a s = 39ps s = 38ps Timing and Cross-Talk Properties of BURLE Multi-Channel MCP PMTs S.Korpara,b, R.Dolenecb, P.Križanc,a, R.Pestotnikb, A.Stanovnikc,a aUniversity of Maribor, Slovenia, bJožef Stefan Institute, Ljubljana, Slovenia, cUniversity of Ljubljana, Slovenia, ALS PiLas controller TDC Kaizu works KC3781A discriminator Philips model 806 NIM amplifier ORTEC FTA820A signal splitter passive 3-way CAMAC QDC CAEN V965 PC LabWindows CVI Abstract VME Modeling of processes in the MCP PMT We report on on-the-bench studies of the two types of BURLE multianode micro-channel plate(MCP) PMTs, one with 64 channels and 25um pores and the other with 4 channels and 10umpores. A possible applications of this tubes are RICH and time-of-flightcounters. We haveinvestigated the timing properties of the tubes and studied various cross-talks and their influenceon the timing and spatial resolution. Parameters used: - cathode to MCP potential difference U = 200 V - photocathode to MCP distance L = 6 mm - photoelectron initial energy E0 = 1 eV g Photo-electron: • d0,max~0.8 mm • t0 ~ 1.4 ns • Δt0 ~ 100 ps Motivation Photo-electron range, projected g Backscattering: • d1,max=2L=12 mm • t1,max ~ 2.8 ns b Distributions assuming that back-scattering by angle b is uniform over the solid angle. Charge sharing Photo-electron travel time ~ 12mm ~ 2.8ns Timing TDC distribution has three contributions: - prompt signal ~ 70% - short delay ~ 20% - uniform distribution ~ 10% back-scattering • Present study: • measure detailed timing properties and cross-talk, • determine their influence on the position resolution and time resolution. 70% 20% Experimental set-up BURLE 85011 MCP-PMT: - multi-anode PMT with two MCP steps - 2x2(8x8) anode pads - 10(25) mm pores - bialkali photocathode - gain ~ 0.6 x 106 - collection efficiency ~ 60% - box dimensions ~ 71mm square Outside dark box: - PiLas diode laser system EIG1000D (ALS) - 404 nm and 635 nm laser heads (ALS) - neutral density filters (0.3%, 12.5%, 25%) - optical fiber coupler (focusing) - optical fiber (single mode,~4mm core) Signal processing: - laser rate 2kHz (~DAQ rate) - amplifier: 350MHz (<1ns rise time) - discriminator: leading edge, 300MHz - TDC: 25ps LSB(s~11ps) - QDC: dual range 800pC, 200pC - HV 2400V Inside dark box mounted on 3D stage: - optical fiber coupler (expanding) - semitransparent plate - reference PMT (Hamamatsu H5783P) - focusing lens (spot size s ~ 10mm) 10% Time resolution of the main peak is dominated by the photo-electron time spread (26ps rms, estimated from the model); other contributions are laser timing (15ps rms) and electronics (12ps rms). Time-walk corrected TDC distributions of all four channels of 2x2 MCP PMT. For the Belle particle identification system upgrade, a proximity focusing RICH detector withaerogel as radiator is being considered. One of candidates for the detector of Cherenkov photonsis a microchannel plate PMT. With its excellent timing properties, such a counter could serve inaddition as a time-of-flight counter. A prototype of this novel device using BURLE 85011 64-anode, microchannel plate PMT, was tested in the test beam at KEK. Excellent performance ofthis counter could be demonstrated (left). In particular, a good separation of pions and protonswas observed in the test beam data with a time-of-flight resolution of 35ps (right). Uniformity of timing 2x2 channel tube 8x8 channel tube Uniformity of response Surface response of PMTs is fairly uniform. Multiple counting is observed at pad boundariesdue to charge sharing. 1 2 1 2 Time walk correction raw TDC TDC vs. ADC correlation is fitted with and used for TDC correction 2 x 12mm = range of back-scattered photo-electrons Slice of 2D distribution shows uniform response withinthe pads, short range cross-talk due to charge sharingand long range photoelectron backscattering cross-talk. ADC Charge sharing Comparison of the charge sharing effects forred (635 nm)andblue (405 nm) laser. Distributions of hits with equal signals on both padsfor the red and blue lasers. The distribution isbroadened for the blue light due to larger initial photoelectron energy. red red blue Fraction of the signal measured onthe left pad vs. light spotposition while scanning over pad boundary using red and blue lasers. blue