Experimental set-up for on the bench tests Abstract Modeling of processes in the MCP PMT Timing and Cross-Talk Properties of BURLE/Photonis Multi-Channel MCP PMTs S.Korpar a,b, I. Adachi c, R. Dolenec b, P. Križan d,a, R. Pestotnik b, A. Stanovnik d,a a University of Maribor, Slovenia, b Jožef Stefan Institute, Ljubljana, Slovenia, c KEK, Tsukuba, Japan, d University of Ljubljana, Slovenia Uniformity of response at B=0T and B=1.5T For the Belle particle identification system upgrade, a proximity focusing RICH detector with aerogel as radiator is being considered. One of candidates for the detector of Cherenkov photons is a microchannel plate PMT. With its excellent timing properties, such a counter could serve in addition as a time-of-flight counter. A prototype of this novel device using BURLE anode, microchannel plate PMT with 25  m pores, was tested in the test beam at KEK. Excellent performance of this counter could be demonstrated (left). In particular, a good separation of pions and protons was observed in the test beam data with a time-of-flight resolution of 35ps (right). Motivation We report on on-the-bench studies of the two types of BURLE multi anode micro- channel plate (MCP) PMTs, one with 64 channels and other with 4 channels, both with 10  m pores. A possible applications of this tubes are RICH and time-of-flight counters. We have investigated the timing properties of the tubes and studied various cross-talks and their influence on the timing and spatial resolution. We have also performed tests in magnetic field up to 1.5 T. Present study: -measure detailed timing properties and cross-talk, -determine their influence on the position resolution and time resolution. BURLE MCP-PMT: - multi-anode PMT with two MCP steps - 2x2(8x8) anode pads - 10  m pores - bialkali photocathode - gain ~ 0.6 x collection efficiency ~ 60% Outside dark box: - PiLas diode laser system EIG1000D (ALS) nm and 635 nm laser heads (ALS) - neutral density filters (0.3%, 12.5%, 25%) - optical fiber coupler (focusing) - optical fiber (single mode,~4  m core) Signal processing: - laser rate 2kHz (~DAQ rate) - amplifier: 350MHz (<1ns rise time) - discriminator: leading edge, 300MHz - TDC: 25ps LSB(  ~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  ~ 10  m) Tests in magnetic field Gain as a function of magnetic field for different operation voltages and as a function of aplied voltage for different magnetic fields = range of back-scattered photo-electrons 2 x 12mm Surface response of PMTs is fairly uniform. Multiple counting is observed at pad boundaries due to charge sharing. Photo-electron: d 0,max ~0.8 mm t 0 ~ 1.4 ns Δt 0 ~ 100 ps  Parameters used: - cathode to MCP potential difference U = 200 V - photocathode to MCP distance L = 6 mm - photoelectron initial energy E 0 = 1 eV Timing with a signal from the second MCP stage Gain in magnetic field Distributions assuming that back- scattering by angle  is uniform over the solid angle. ~ 2.8ns ~ 12mm  = 40ps  = 37ps  = 38ps  = 39ps 70% 20% 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). TDC distribution has three contributions: - prompt signal ~ 70% - short delay ~ 20% - uniform distribution ~ 10% back-scattering Timing Backscattering: d 1,max =2L=12 mm t 1,max ~ 2.8 ns Charge sharing    Slice of 2D distribution shows a uniform response within the pads, and the long range cross talk due to photoelectron back- scattering and photon reflection. Idea: read timing for the whole device from a single channel (second MCP stage), while 64 anode channels are used for position measurement MCP second stage output Time-walk corrected TDC distributions of all four channels of 2x2 MCP PMT. amplifier ORTEC FTA820A signal splitter passive 3-way discriminator Philips model 806 QDC CAEN V965 VME TDC Kaizu works KC3781A CAMAC NIM PC LabWindows CVI ALS PiLas controller Photo-electron range, projected Photo-electron travel time Measurements of gain, uniformity of response snd cross talk Magnet at KEK with B field up to 1.5 T Light source - laser: wavelength 439 nm spot size < 0.5 mm pulse timing 90 ps (FWHM) Scans across a 64 channel PMT without (top) and with magnetic field (bottom). Number of detected hits on individual channels as a function of light spot position. B = 0 T, HV = 2400 V B = 1.5 T, HV = 2500 V If a charged particle passes the PMT window, ~10 Cherenkov photons are detected in the MCP PMT; they are distributed over several anode channels. Single anode Timing resolution as a function of light intensity  ps In the presence of magnetic field, charge sharing and cross talk due to long range photoelectron back-scattering are considerably reduced.