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Design Studies and Sensor Test for the Beam Calorimeter of the ILC Detector

Explore the design and testing of sensors for the International Linear Collider Beam Calorimeter, evaluating the efficiency, radiation hardness, and dynamic range for precision measurements.

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Design Studies and Sensor Test for the Beam Calorimeter of the ILC Detector

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  1. Design Studies and Sensor Test for the Beam Calorimeter of the ILC Detector E. Kuznetsova DESY Zeuthen

  2. International Linear Collider (ILC) – why? f (Z, W-) t- H ~ e- t- (hep-ph/0510088) χ0 f (Z, W+) t+ Z0 ~ e+ t+ χ0 LC e+e-√s = 500 GeV in ~2015 a facility for precision measurements

  3. International Linear Collider (ILC) e+e-, e-e- (eg, gg) 90 GeV ≤√s ≤ 500 GeV (1 TeV) polarized beams 2-20 mrad crossing angle Nominal parameters (Aug.2005)

  4. ILC Detector - Large Detector Concept (LDC) “Particle flow method” (PFLOW) : TPC + calorimetry sEjet/Ejet≈ 30%/√E B = 4 T

  5. Beamstrahlung at ILC ~20 mrad N = 2x1010; sx = 655 nm; sy = 5.7 nm ~1 mrad ng = 1.26 (ILC) TESLA; z = 365 cm Per bunch crossing @ 500 GeV: TESLA 22 TeV 20 mrad crossing angle design 66 TeV B = 4 T

  6. Very Forward Region of the LDC Detector hermeticity Luminosity measurements (LumiCal) Fast Beam diagnostics (BeamCal)

  7. LumiCal and luminosity measurements Cross section calculation polar angle measurements ~ 2(D)sys/  (dL/L)sys Luminosity accuracy goal dL/L ~ 2x10-4 if min = 30 mrad max = 75 mrad 1 year: ~109 events (dL/L)stat ~ 10-4 Si/W calorimeter (26-141) mrad

  8. BeamCal: motivation m- ~ e- m- χ0 m+ Z0 ~ e+ m+ χ0 - e - e g m - m + g + + e e (5.6-26.6) mrad Beam diagnostics: ILC; z = 355 cm + vertical offset of 10nm Low angle detection: σ ~ 106 fb σ ~ 102 fb (SPS1a)

  9. BeamCal: requirements • High radiation hardness (up to 10 MGy/year) • Small Moliere radius and high granularity • Wide dynamic range Diamond-Tungsten sandwich calorimeter

  10. Why diamond? • Resistant enough to e/m radiation • (at least for low energy) • Comparison with silicon: T.Behnke et al., 2001

  11. Simulation studies of the calorimeter performance • TESLA Detector design (r,f) - segmentation : tungsten absorber + -> RM ~ 1 cm diamond sensor cell size ~ 0.5 cm • Z - segmentation : • tungsten 3.5 mm • Layer = = 1 X0 • diamond 0.5 mm

  12. Simulation Studies of the calorimeter performance Event – 50-250 GeV e- Background – pairs from 1 bunch crossing (“Guinea-Pig”) Full detector simulation – BRAHMS (GEANT3) Statistics: 500 bunch crossings

  13. Simulation studies: efficiency

  14. Simulation studies: fake rate • In 10% of bunch crossing a “high” energy e- occurs • BG fluctuations • The reconstruction is not ideal pure BG E> 20 GeV pure BG after reco ~2% of “fake” e- of E > 50 GeV for the chosen parameters

  15. Simulation studies: energy resolution intrinsic s/E=22%/√E with BG (example)

  16. Requirements from the simulation studies: • Dynamic range – 10-105 MIP/cm2 • Digitization - 10 bit (considered segmentation)

  17. Sensor tests: pCVD diamonds Si Polycrystalline Chemical Vapour Deposition Diamonds growth side substrate side Typical growth rate : ( 0.1 – 10 ) mm/hr • Defects at the grain boundaries • Graphite phase presence • Si, N impurities

  18. Sensor tests: samples Samples: Fraunhofer IAF, Element Six Requirements: - stability under irradiation - linearity of response First step - Fraunhofer IAF (Freiburg) : • CVD diamond 12 x 12 mm2 • 300 and 200 mm thickness • Different wafers and different surface treatment (3 samples/group): • #1 – substrate side polished; 300 mm • #2 – substrate removed; 200 mm • #3 – growth side polished; 300 mm • #4 – both sides polished; 300 mm

  19. Sensor tests: Current-Voltage characteristics HV Diamond Keithley 487 N2 • 0 < |V| < 500 V • 0 < |F| < ~2 V/mm • Shielded box • Light tight • N2 flow + open circuit measurements: |I| < 0.05 pA for 0 < |V| < 500 V

  20. Sensor tests: Current-Voltage characteristics “ohmic” behaviour, “low” current “non-ohmic” behaviour, “high” current No correlation with group# (wafer, surface treatment) R ~ (1011-1014W) at F = 1 V/mm

  21. Sensor tests: Charge Collection Distance (CCD) L Polycrystalline material with large amount of charge traps Qinduced < Qcreated e= Qinduced/Qcreated CCD ≈ e L

  22. Sensor tests: CCD measurements MIP: Qcreated/L= 36 e-/mm CCD = L x Qmeasured/Qcreated CCD[mm] = Qmeasured[e-]/36 Fast measurements - in 2 minutes after the voltage applied… CCD range = f(wafer), but no correlation with surface treatment

  23. Sensor tests: CCD vs dose F = 1 V/mm Group#2 (wafer#2, cut substrate) Group#3 (wafer#3, untreated substrate) Group#3 (wafer#3, untreated substrate)

  24. Sensor tests: more samples! Fraunhofer sample Element Six I < 0.3 nA • Stabilizes after ~20 Gy! • CCD ~ 30 mm • dose rate influence…

  25. Sensor tests: linearity test 17 s 10 ns Scint.+PMT& Diamond gate signal ADC Hadronic beam, 3 & 5 GeV (CERN PS) Fast extraction mode ~104-107 / ~10 ns

  26. Linearity test – relative intensity measurements “Relative Intensity” Beam intensity wide intensity range PMT1,PMT2 Beam intensity + offline PMTs calibration + absolute intensity measurement (Thermoluminescence dosimetry)

  27. Linearity test – particle flux estimation Linearity of the corrected PMT response (at a reduced range) + absolute calibration for one of the runs 1 RI = (27.3±2.9) 103 MIP/cm2

  28. Linearity of the diamond response Element Six sample Fraunhofer sample y = p[0]x E64 FAP2 30% deviation from a linear response for a particle fluence up to ~107 MIP/cm2 The deviation is at the level of systematic errors of the fluence calibration

  29. Conclusions -> Simulation studies • diamond-tungsten sandwich design of the BeamCal is feasible • For Ee~ √s/2 an efficient detection is possible for most of  • For lower Ee:  > 15 mrad • (sE/E)intr = 22%/√E; sE/E = f(BG) • s ~ 10-4 rad; sφ~ 10-2 rad - for low BG density • Dynamic range 10-105 MIP/cm2 (TESLA) • pCVD diamond – a promising sensor material • A set of measurements is established to test the sensor quality • A feedback to Fraunhofer IAF allows to improve quality • We already have samples • with CCD of ~30 mm • with a stable response • with a ~linear response for a fluence up to 107 MIP/cm2 -> Sensor studies

  30. Reserve

  31. Simulation studies: efficiency Ngen = 500 Nreco = 521 E = 100 GeV

  32. Simulation studies: energy resolution

  33. Simulation studies: angular resolution

  34. Simulations:Sr + diamond

  35. CCD – irradiation studies – results Group #2 (substrate side removed). HV = 200V Group #1 (substrate side polished). HV = 300V

  36. CCD – irradiation studies – results Group #3 (growth side polished). HV = 300V Group #4 (both sides polished). HV = 300V

  37. Linearity test – PMT calibration

  38. Raman spectroscopy Resolution ~ 1 cm-1 Result= S(diam)/S(graphite)*1000

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