Update on Electronics Activities

1. Update on ElectronicsActivities Jim Pilcher University of Chicago 20-Jan-2006

2. 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 J. Pilcher

3. 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 J. Pilcher

4. PMT Testing • Testing to date is limited • Test with small beaker (~ 200 ml) of liquid scintillator and Co-60 source in a dark box • 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 J. Pilcher

5. PMT Testing • Single pe pulse from Hamamatsu shows reflection ~10 ns after primary peak • Not scope connection • Multiple pe signal includes scintillator properties J. Pilcher

6. 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 J. Pilcher

7. PMT Testing • Much more work to be done on PMTs • 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 • Visitors and/or suggestions welcome J. Pilcher

8. R&D on Readout • 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 J. Pilcher

9. R&D on Readout • Design features of strawman approach • Similar to readout approach in ATL AS Tile Calorimeter, Auger, … • 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 J. Pilcher

10. R&D on Readout • 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 linear line driver Preamp and Line Driver PMT J. Pilcher

11. R&D on Readout • 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 J. Pilcher

12. R&D on Readout • Digitize waveform from PMT/shaper every 15 ns • DSP processing extracts amplitude and time • Shape below is SPICE simulation of shaper J. Pilcher

13. R&D on Readout • Possible organization VME Modules J. Pilcher

14. R&D on Readout • 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 1.0 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 J. Pilcher

15. R&D on Readout • 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 • Atrigger 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 J. Pilcher

16. R&D on Readout • 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 J. Pilcher

17. Prototype tank • Geometry? • ~ 1.6 m3normalliquid scint. • ~ 4.4 ℓ Gd loaded scint. • In 10-cm radius acrylic sphere • Capture length ~ 4 cm. @ 0.2%Gd • Movable along axis of cylinder • 3 PMTs on each end J. Pilcher

18. 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 Kaboth so data is needed by May J. Pilcher

19. Conclusions • That’s it from Chicago! J. Pilcher