Published on November 7, 2007
Update on ElectronicsActivities: Update on Electronics Activities Jim Pilcher University of Chicago 20-Jan-2006 Readout Electronics: Readout Electronics Last talk on electronics was some time ago Need update on recent activities at Chicago PMT testing R&D on readout Prototype tank being prepared Recall electronics parameter list on web site http://hep.uchicago.edu/~pilcher/th13/electronics/electronics.html Active Excel file which will update if input assumptions are changed Also earlier electronics talk on web site PMT Testing: PMT Testing The prototype tank being prepared will use six 8-inch PMTs More details on tank later in the talk We have 2 from each of three vendors Candidate tubes for final detector Hamamatsu R5912 10 stages, G=107 @ 1500V, dark count rate 4.0 KHz Photonis XP1806 11 stages, G=107 @ 1340V, dark count rate 1.6 KHz Electron Tubes 9354KFLB 12 stages, G=107 @ 1300V, dark count rate 4.0 KHz All have low activity glass envelope All equipped with manufacturers’ bases PMT Testing: PMT Testing Testing to date is limited Have looked mainly at single pe pulse shapes Impacts readout electronics Have looked with illumination of full photocathode and of a 2 cm x 2 cm region Have operated at HV for G = 107 Measurements also underway in low background lab on activity of glass Will be reported at future meeting Test with small beaker (~ 200 ml) of liquid scintillator and Co-60 source in a dark box PMT Testing: PMT Testing Single pe pulse from Hamamatsu shows reflection ~10 ns after primary peak Not scope connection Multiple pe signal includes scintillator properties PMT Testing: PMT Testing Photonis tube showed low gain and broad signal Perhaps faulty Need to test second tube Electron Tubes tube is similar to Hamamatsu but slightly slower PMT Testing: PMT Testing Much more work to be done on PMTs Suggestions and/or visitors welcome No special hardware on hand for detailed measurements Photocathode uniformity, linearity, quantum efficiency, gain, after-pulsing, magnetic field sensitivity, etc. Our goal was to take a first look before using them in prototype tank We would be happy to have help from others on PMTs Readout R&D: Readout R&D Strawman proposal presented in earlier talk on web site Dual range, 12-bit readout on each PMT Gain ratio 32:1 between two scales Separate ADCs on each scale for easy inter-calibration of scales Overall dynamic range 17 bits 15 counts/pe at low end of range High end ~70 times most probable single muon signal for “average” PMT PMTs close to muon will receive much larger signals High energy radiative tail for muons Multiple muons from cosmics Suitability to be confirmed by Monte Carlo studies Readout R&D: Readout R&D Design features of strawman approach Similar to readout approach in ATL AS Tile Calorimeter, Auger, Quiet, … Convert PMT signal to a pulse of standard shape but amplitude proportional to input charge Create Gaussian shape with FWHM of 30 ns Sample with commercial 12-bit ADCs every 15 ns. Extract amplitude and time of signal with respect to sampling clock by digital signal processing Can give sub-1% amplitude resolution and ns time resolution (seen in ATLAS) Shaper and pre-amp on PMT base Digitizer in VME crate outside containment sphere Readout R&D: Readout R&D Shaping obtained with purely passive components (LC) Exploits current source nature of PMT Linearity guaranteed Very low noise Insensitive to input shape Follow with active preamp and line driver PMT Preamp and Line Driver Readout R&D: Readout R&D Packaging and system planning Shaper on PMT Perhaps on same PCB as voltage divider Two shielded twisted pair outputs Digitizer on VME board 32 channels per board Form local trigger information from patch of 32 PMTs Total number of pe Overall trigger could be based on trigger info from 32 patches Would allow some geometrical requirements as well as total signal Trigger could be based on same data as read out Readout R&D: Readout R&D Digitize waveform from PMT/shaper every 15 ns DSP processing extracts amplitude and time Shape below is SPICE simulation of shaper Readout R&D: Readout R&D Possible organization VME Modules Readout R&D: Readout R&D Status Working on shaper design Thinking about VME board How do we prove this will do the job? Prototype tank already being prepared Record data with calibration sources Use proposed shaper but commercial digitizer A CAEN VME module can sample every 0.5 ns Can sample PMT directly to show ultimate time resolution Can sample shaped signal every 15 ns to show time resolution and performance of shaped scheme Readout Electronics: Readout Electronics CAEN V1729 VME digitizer for prototype tests Bandwidth 300 MHz Up to 2 GHz sampling rate into storage caps. 12 bit A-to-D conversion after trigger Memory with 2520 samples per channel A trigger stops the continuous sampling 4 differential inputs per module (2 PMTs) 16-bit dynamic range using high-gain and low-gain inputs from each PMT 11 bits reading PMT directly $2.2K / channel (very pricey!) 3 modules on order Readout R&D: Readout R&D How might electronics design evolve? We have a strawman proposal for front-end and organization Other options should be considered too Cost and performance important metrics Alternative readout schemes could be tried with prototype tank Visitors welcome Many important electronics topics need work Trigger, signal processing, LV system, HV system, DAQ system Prototype tank: Prototype tank Geometry? ~ 1.6 m3 normal liquid scint. ~ 4.4 ℓ Gd loaded scint. In acrylic sphere Movable along axis of cylinder 3 PMTs on each end Prototype tank: Prototype tank Plan is to run with various sources and cosmic muons Californium a fission source giving prompt gammas plus delayed gammas from neutrons capture in Gd Co-60 for photons Validate Monte Carlo code Tank has different geometry but most of the physics processes of the full detector Validate readout electronics Get experience with candidate PMTs Test bed for candidate readout systems Status Tank being fabricated and expected in early February Three CAEN V1729 modules on order A senior thesis project for Abby so data is needed by May Conclusions: Conclusions That’s it from Chicago!