CBM-RICH: Photodetector developementH8500+nXyter+ROC readoutP.Koczo, R.Karabowicz, R.Lalik, C.Schmidt, V.Kleipe, W.F.J.Mller H8500+UV LED + nXyter readout Optical properties of pTer rsum Outlook: WLS foils
H8500HVPulseGeneratornXyter+ROCLighttight boxUV LEDgatesignal20 cmH8500+nXyter+ROC - setupSchematic view of themultiparameter measurementof WLS/H8500 propertiesAperture maskwith pinholesChargeDivider
H8500+nXyter+ROC - setupChargeDivider nXyterROC
Charge dividerH8500 multiplication factor ~106 @ 800V biasing voltage but sensitivity of nXyter input ~ 5 mips (125000 e) => an adapter is necessary!!The charge divider (details in http://cbm-wiki.gsi.de/cgi-bin/viewauth/Rich/CbmRichMeeting031208 ) is a C/R circuit :PMTN-XYTERWe prepared several boards with different sets of R1, R2, C1, C2:(Simone Bianco)S3S5
R1R2C2C10 10 k1 nF10 pF91 10 0 nF2 pF0 100 1 nF10 pF91 10 0 nF10 pF0 100 0 nF10 pF50 10 k10 pF470 pF
Charge divider 3rd try: not so bad10 ns1.6 V15 ns40 mV, S5More advanced simulations by Tim Armbruster Uni HDresult in an attenuation factor of 48.71QinQoutQin / Qout = attenuation factorH.C. Soltveit (one of nXyter developers)claims that it should be possible to trimmthe chip such, that the charge dividerwill be obsolete.
H8500 pinhole apertureAperture maskPin holes
System noiseChannel #Amplitude [ch]nXyter has a very sensitive input, it is very noisy.Only by adjusting of global (and channel)offsets and thresholds can be done operational.
H8500 signal readoutCh#1 Ch#64Collected charge
Collected chargeH8500 signal readoutChannel #18 channel# 82 112
H8500 readoutH8500 - rear sidePixelnumber - Channel number - correspondence112 -> P3278,82 -> P29, P3018 -> P4
?H8500 readoutThere ist obviously a misaligment betw.the mask and the PM
P4 not understood
WLSWindow (1mm)PM structureTo do 1) H8500 cross-talk future plans
Hamamatsu claims for H8500: cross talk < 3% (electronics)
WLS can add an additional cross-talk between neighbouring pixels when a photon undergoes absorption-reemision in the WLS layer or falls inclined on the PMs entrance window Simulations (Paola Solevi, Det.Lab. CERN): =3mm(WLS layer)Inclined photonPhoton transformed in WLSPropagation in WLS
To do 2) Single photon counting capability using H8500+CD+nXyter+ROCSingle photon?Double hit?Single Photon Counting capabilityhas been demonstrated (Dubna 2008) in a coincidence measurementwith 2 Hamamatsu X2020 and Picoscope.
SPC has to be also proved for H8500with nXyter!
Ad 2) Single photon counting capability using H8500+CD+nXyter+ROCChannel #deltaT[ns]Coincidence measurement using nXyter system
Conclusions (Part 1)
nXyter+ROC with CD seem to work with H8500 Further measurements of a) cross talk between pixels with and w/o WLS coating b) single photon counting capability with nXyter system are necessary
WLS summaryP.Koczo, C.Hhne, A.BraemC.Joram, M. van Stenis choice of the wavelength shifter material silicon pads with WLS
Choice of the WLS material Several WLS materials have been tested (TPB, pTerphenyl, YellowX) Different coating methods (evaporation, spraying) evaporated p-Terphenyl shows the highest gain ageing in CO2 not (yet) observed timing properties not studied
Integrated QE of pTer and TPB as function of photon energypTerphenyl shows the highest integrated gainextrapolation
WLS embeded in silicon padsWLS - Si padPM structureWindow (1mm)~0.3 mmAdvantages:1) Much easier production as compared to evap. procedure2) Can be prepared in advance in different thicknesses and WLS concentrations3) Can be changed on the PM at any time4) Can be easily exchanged in case of damage5) WLS material protected from chem. influences ? Does it work at all ??? Is thickness an issue ??
Thank You !
Cross-talks - setupH8500HVPulseGeneratorDAQgrey filterLight guide bundleLighttight boxLEDgatesignalXY-table