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Polycrystalline CVD Diamonds for the Beam Calorimeter of the ILC

Polycrystalline CVD Diamonds for the Beam Calorimeter of the ILC. C.Grah ILC ECFA 2006 Valencia, 9 th November 2006. Contents. Very forward region of the detectors for the International Linear Collider BeamCal – requirements Testbeam at CERN Linearity of the response of CVD diamonds

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Polycrystalline CVD Diamonds for the Beam Calorimeter of the ILC

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  1. Polycrystalline CVD Diamonds for the Beam Calorimeter of the ILC C.Grah ILC ECFA 2006 Valencia, 9th November 2006

  2. Contents • Very forward region of the detectors for the International Linear Collider • BeamCal – requirements • Testbeam at CERN • Linearity of the response of CVD diamonds • Testbeam at the TU Darmstadt • Radiation hardness of CVD diamonds • Conclusions C.Grah: CVD Diamonds

  3. Very Forward Region of the ILC Detectors • The purpose of the instrumentation of the very forward region is: • Hermeticity: increase the coverage to polar angles > 5mrad • Optimize Luminosity BeamCal Interaction point • EM calorimeter with sandwich structure: • 30 layers of 1 X0 • 3.5mm W and 0.3mm sensor • Angular coverage from 5mrad to 28 mrad • Moliére radius RM ≈ 1cm • Segmentation between 0.5 and 0.8 x RM LDC C.Grah: CVD Diamonds

  4. The Challenges for BeamCal e+ e- e+ e- γ Interaction γ e- e- e.g. Breit-Wheeler process Creation of beamstrahlung at the ILC • e+e- pairs from beamstrahlung are deflected into the BeamCal • 15000 e+e- per BX => 10 – 20 TeV total energy dep. • ~ 10 MGy per year strongly dependent on the beam and magnetic field configuration => radiation hard sensors • Detect the signature of single high energetic particles on top of the background. => high dynamic range/linearity ≈ 1 MGy/a ≈ 5 MGy/a C.Grah: CVD Diamonds

  5. Polycrystalline Chemical Vapour Deposited Diamonds (courtesy of IAF) • pCVD diamonds are an interesting material: • radiation hardness (e.g. LHC pixel detectors) • advantageous properties like: high mobility, low εR = 5.7, thermal conductivity • availability on wafer scale • Samples from two manufacturers are under investigation: • Element SixTM • Fraunhofer Institute for Applied Solid-State Physics – IAF • 1 x 1 cm2 • 200-900 μm thick (typical thickness 300μm) • Ti(/Pt)/Au metallization (courtesy of IAF) C.Grah: CVD Diamonds

  6. Linearity Test at CERN PS 17 s 10 ns Hadronic beam, 3 & 5 GeV Fast extraction mode ~104-107 particles / ~10 ns Setup Beam Scint.+ PMTs. Diamond gate signal ADC Response of diamond sensor to beam particles (no preamplifier/attenuated) Photomultiplier signals C.Grah: CVD Diamonds

  7. Response vs. Particle Fluence Fraunhofer IAF Element Six E64 FAP2 30% deviation from a linear response for a particle fluence up to ~106 MIP/cm2 The deviation is at the level of the systematic error of the fluence calibration. C.Grah: CVD Diamonds

  8. High Dose Irradiation Superconducting DArmstadt LINear ACcelerator Technical University of Darmstadt • Irradiation up to several MGy using the injector line of the S-DALINAC: 10 ± 0.015 MeV and beam currents from 10 to 100 nA corresponding to about 59 to 590 kGy/h V.Drugakov 2X0 Energy spectrum of shower particles in BeamCal C.Grah: CVD Diamonds

  9. Preparations and Programme preamp box GEANT4 simulation of the geometry Beam setup absorber collimator Apply HV to the DUT Measure CCD ~20 min Irradiate the sample ~1 hour => R = NFC/NSensor = 0.98 <Edep>/particle = 5.63 MeV/cm CCD: Charge Collection Distance C.Grah: CVD Diamonds

  10. Realization: Beam Setup exit window of beam line collimator (IColl) Faraday cup (IFC, TFC) sensor box (IDia, TDia, HV) C.Grah: CVD Diamonds

  11. CCD Setup PA Sr90 ADC diamond delay Sr90 source Scint. discr PM1 & Gate discr PM2 Preamplifier Sensor box Trigger box Setups partly financed by EUDET. typical spectrum of an E6 sensor C.Grah: CVD Diamonds

  12. Results: CCD vs. Dose 100 nA (FAP5) CCD = Qmeas/Qinduced x thickness Bias voltage = 400V ≈> 1 V/μm Silicon starts to degrade at 30 kGy. High leakage currents. Not recoverable. After absorbing 7MGy: CVD diamonds still operational. 100 nA (E6_4p) C.Grah: CVD Diamonds

  13. Behaviour after Irradiation No significant change of the current-voltage characteristics up to 1.5 MGy. Slight increase of currents for higher doses. C.Grah: CVD Diamonds

  14. CCD Behaviour after Irradiation ~ -80% ~ -30% after 7 MGy after 1.5 MGy C.Grah: CVD Diamonds

  15. After Irradiation: IAF Sample before/after ~ 7MGy ▪before irradiation ▪after irradiation strong „pumping“ behaviour. signal recovery after 20 Gy ▪FAP 5 irradiated, 1st measurement ▪FAP 5 irradiated, additional 20 Gy C.Grah: CVD Diamonds

  16. Summary • PCVD diamonds are an interesting material as sensors for the BeamCal. • The linearity of pCVD diamonds up to particle fluences of 106 particles/cm2/10ns is better than 30%. • High dose irradiation using 10MeV electrons shows: • all CVD diamonds stay functional even after absorbing up to 7MGy. • degradation of the signal at high doses and dose rates. • partial recovery of the signal after absorbing additional small doses (~20 Gy). • wide variation of the signal sizes as a function of the absorbed dose is an issue for the use as a sensor for BeamCal. • Started to investigate also other materials (GaAs, SiC) as alternative. • Successfull irradiation-testbeam at the S-DALINAC. We plan to repeat the irradiation with more and other types of sensors next year. http://www-zeuthen.desy.de/ILC/fcal/ C.Grah: CVD Diamonds

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