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Studies on Module 0 HAC

Studies on Module 0 HAC . V. Fascianelli , V. Kozhuharov , M. Martini, T. Spadaro, D. Tagnani. Outline. Reminder: HAC insertion in NA62: why/how M odule 0 HAC tests at BTF@LNF, for: obtaining order-zero measurement of light yield assessing possible FEE readout schemes

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Studies on Module 0 HAC

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  1. Studies on Module 0 HAC V. Fascianelli, V. Kozhuharov, M. Martini, T. Spadaro, D. Tagnani

  2. Outline • Reminder: HAC insertion in NA62: why/how • Module 0 HAC tests at BTF@LNF, for: • obtaining order-zero measurement of light yield • assessing possible FEE readout schemes • First data/MC comparison studies: • simple digitization/reconstruction algorithms implemented, following FEE scheme assumed Photon veto meeting - Liverpool

  3. HAC: why, how • From the work by Ruggiero (23/5/2012) and Spasimir (06/02/2013): • need a new detector to reject O(10) residual background events from K->p+p+p- / year • events with p- lost (due to nuclear interaction), and a p+ escaping detection through the hole, grazing the pipe, emerging at various depths in the range 247 < z < 255 m • need to efficiently veto p of ~40 GeV, with a detector at z = 253.35 m, while sustaining a muon halo rate of ~4 MHz (dominated by p+m+ decays downstream GTK3) • bad energy resolution expected due to lateral leakage • total rate reduced by x10 if E>100 MeV is required • O(<1ns) time resolution to correctly match HAC information with the rest of event Photon veto meeting - Liverpool

  4. HAC: why, how • A single HAC channel collects light from 6 scintillator tiles (4 mm wide) alternating to 16-mm Pblayers • Lights from each scintillatorcollected by a green-centered 1-mm2 WLS fibers • Tentative detector setup: 9 modules, each with 10 channels along the longitudinal direction From F. Hahn Photon veto meeting - Liverpool

  5. RO: order of magnitude cost estimate Consider 90 channels in total SiPM case: • 100 E/SiPM, 150 E / amplifier + Voltage bias electronics (evaluation scaling from CHANTI board, 4000 E/32 ch’s): 22500 E • Digitizer (GANDALF, 12 bit 500 MS/s): 60000 E for 96 channels • Grand total: 82 500 E PMT case: • 400 E/PMT, 200 E/HV-ch: 54000 E • The GANDALF is a common solution for both setups • Grand total is 115 000 E Photon veto meeting - Liverpool

  6. HAC studies • Order-0 questions: is the scintillator performance still valid and is the light collection enough? • Order-1 questions: can it be instrumented with SiPM’s or we have to consider PMT’s? • Order-2 question: can it be readout with Flash ADC’s? Photon veto meeting - Liverpool

  7. Measurement of HAC response rates Order-0 questions: are the scintillator performance and the light collection still OK? • Data taken with SiPM at nominal bias voltage • Trigger set at ~30 mV (~7 photoelectrons), rates in dark of ~20 Hz • Use a Cs137, 0.18 MBq, 30.07 years radioactive source • Study trigger rates as the source is moved along the longitudinal direction Photon veto meeting - Liverpool

  8. Measurement of HAC response rates Order-0 questions: are the scintillator performance and the light collection still OK? • Measurement from each position repeated 4 times • Expect spacing of 4 + 16 mm, OK • 6 peaks spotted, rates span a range of x3... need cosmic-ray characterization, to be done Counts from channel 3 / 10 s no source Longitudinal Position (cm) Photon veto meeting - Liverpool

  9. BTF runs • Trigger setup with two positive signals from scintillator paddles • Electron beam, 50 Hz, O(1) electron multiplicity • Readout via Flash ADC, CAEN module V1751, 8 ch’s, 10 bit, 1 GS/s: • from signal shape, evaluate maximal voltages, integrated charge around the maximum, event-by-event pedestal, time of the maximum • HAC runs: 570-MeV beam impact head-on onto channel 0 region at the center • Expect some lateral leakage due to beam angular dispersion: the HAC is placed ~ 1 m downstream the pipe end Photon veto meeting - Liverpool

  10. BTF runs: e- beam multiplicity, Q’s Integrated Charge horizontal paddle (C) • - 0 electrons • - 1 electron • - 2 electrons • - 3 electrons Integrated Charge vertical paddle (C) Photon veto meeting - Liverpool

  11. BTF runs: e- beam multiplicity Poisson distribution fit: m = 0.94(1), c2 = 1.8/1 Photon veto meeting - Liverpool

  12. HAC readout • Interface 6+1 (for calibration) fiber bundle at module end with 3x3 mm2 prototypal high-density SiPM, Hamamatsu MPPC 15 mm x15 mm pixels: • Gain of 2.5 105, at 69.3 V bias at room termperature • 57,600 15 x 15 mm2 pixels in 3x3 mm2 active area • ~ 370 pF capacitance • Gain lower than available SiPM’s by ~x3, but better time resolution expected, since novel corrections due to delay for far pixels are present (TSV, Through Silicon Via, no wire bonding, see http://kicp-workshops.uchicago.edu/ieu2013/depot/talk-ghassemi-ardavan__1.pdf) • Voltage supply and amplification during run with electronics tuned for a 70 pF SiPM: time performance not reliable • Runs were acquired with a PMT readout, as well Photon veto meeting - Liverpool

  13. HAC response: sampling a signal Signal amplitude [mV] SiPM readout Signal amplitude [mV] PMT readout Time [ns] Photon veto meeting - Liverpool

  14. HAC response: maximal amplitude • - 0 electrons • - 1 electron • - 2 electrons • - 3 electrons Amplitude (mV) Photon veto meeting - Liverpool

  15. HAC Response: charge • - 1 electron • - 2 electrons • - 3 electrons Integrated charge (C) Photon veto meeting - Liverpool

  16. HAC Response: maximum amplitude s(V)/V <V> [mV] Nominal impact energy (MeV) Photon veto meeting - Liverpool

  17. HAC Response: charge s(Q)/Q <Q> [C] Nominal impact energy (MeV) s(E)/E ~ 35%/Sqrt(E[GeV]) Photon veto meeting - Liverpool

  18. SiPM characterization in dark • SiPM signals sampled in laboratory at fixed temperature and with no input source • FEE electronics adapted from project developed for Mu2e (Martini, Tagnani, Corradi) performing accurate APD preamplification • FEE electronics providing x97, while being matched to the SiPM capacitance • The value correspond to optimal matching and lowest noise • Bias voltage provided via linear power supply • Study of the V-I characteristics Current (mA) Vop Bias voltage (V) Photon veto meeting - Liverpool

  19. SiPM characterization in dark • Apply a 3 mV threshold, corresponding to < 1 pe (see after) • Use oscilloscope as a Flash ADC • Sampling frequency, 1 sample every 0.4 ns ~20 ns fall time pedestal evaluation region ~8 ns rise time FADC channel # = T [0.4 ns] Photon veto meeting - Liverpool

  20. SiPM in dark: the analog signal Amplitude (10 mV / division) Vbias = 71.4 V Trigger Time (10 ns / division) Photon veto meeting - Liverpool

  21. SiPM characterization in dark • Evaluate maximum of SiPM signals and the related population • Fit the first 3 peaks, corresponding to n, n+1, n+2 photoelectrons • Perform a single fit allowing the peak-to-peak distance as free parameter Repeat the above steps in a wide range of voltage bias: 69.3 V (nominal + 0.3V)  71.8 V Photon veto meeting - Liverpool

  22. SiPM characterization in dark • Change of the single-photoelectron voltage with the bias, as expected • Single photoelectron ranges from 4.5 mV to 8.5 mV as Vbias varies from 69.3 to 71.8 V peak to peak distance (V) bias voltage (V) Photon veto meeting - Liverpool

  23. SiPM characterization in dark • Change of the single-photoelectron voltage with the bias, as expected • Single photoelectron ranges from 4.5 mV to 8.5 mV as Vbias varies from 69.3 to 71.8 V • Result confirmed by the position of the first peak position of first peak (V) bias voltage (V) Photon veto meeting - Liverpool

  24. SiPM characterization in dark • Change of the poissonian probability, ranging from ~0.2 to ~0.6 as the bias voltage varies • Probably an effect linked to PDE variation bias voltage (V) Photon veto meeting - Liverpool

  25. SiPM characterization in dark • Evaluate charge of SiPM signals and the related population • Fit the first 3 peaks, corresponding to n, n+1, n+2 photoelectrons • Perform a single fit allowing the peak-to-peak distance as free parameter • Repeat the above steps in the bias range: 69.3 V (nominal + 0.3V)  71.8 V Charge (pC) Photon veto meeting - Liverpool

  26. SiPM characterization in dark • Gain evaulation within the expectation: 105 2 105, after correcting for the FEE amplification of 100 (actually 97) • Position of 1st peak confirms that the distribution is due to 1, 2, 3 photoelectrons Gain = 1.8 105 Gain = 105 bias voltage (V) Photon veto meeting - Liverpool

  27. MC HAC Digitization • Complement the MC made by Spasimir with digitization and reconstruction • The following assumptions are used: • Scintillator produces 104 photons / MeV • 10-3 of the produced photons reach the SiPM • SiPM PDE = 0.6 • The SiPM Gain is 106 (it will be changed in future) • With a FEE electronics amplification of 10, a single photo-electron produces a 4-mV peak with a 8 ns rise time and a 20 ns fall time Photon veto meeting - Liverpool

  28. HAC MC: energy release electrons head-on impact s(E)/E <E> [MeV] Electron energy (MeV) Photon veto meeting - Liverpool

  29. HAC MC: electrons MC reconstructed electrons head-on impact s(V)/V <V> [mV] Electron energy (MeV) Photon veto meeting - Liverpool

  30. HAC Data/MC comparison: electrons data Fractional resolution • - Data • - MC reco • - MC truth Electron energy Photon veto meeting - Liverpool

  31. Conclusions Experience with HAC basically shows a working detector: • Satisfactory operation with electron beam at Frascati BTF • SiPM characterization in dark in agreement with Hamamatsu specifications • Benefiting of previous work by Spasimir on MC, a simple procedure for digitization/reconstruction added (at the moment the code is kept private) • Good linearity of energy response observed • Agreement between data and MC after digitization has to be proved with cosmic rays: data with 2-3 electrons probably affected by lateral leakage SiPM operation + Flash ADC readout satisfactory To-do list: • improved description of MC digitization (pileup of scintillator signals) • Complete development of the low-noise voltage regulator • cosmic ray tests and additional acquisitions with radioactive source • test of final electronics (at the moment, in production) • Channel by channel intercalibration studies • Final design of readout on-board electronics and mechanical interface Photon veto meeting - Liverpool

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