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Radiation Hard Sensors for the BeamCal of the ILC

Radiation Hard Sensors for the BeamCal of the ILC. C. Grah FCAL Collaboration 10 th ICATPP Conference, Villa Olmo. Contents. The ILC and the very forward region of the detectors for the International Linear Collider BeamCal – requirements Radiation hard materials under investigation:

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Radiation Hard Sensors for the BeamCal of the ILC

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  1. Radiation Hard Sensors for the BeamCal of the ILC C. Grah FCAL Collaboration 10th ICATPP Conference, Villa Olmo

  2. Contents • The ILC and the very forward region of the detectors for the International Linear Collider • BeamCal – requirements • Radiation hard materials under investigation: • CVD diamond • Silicon • GaAs and SiC • Conclusions C.Grah: Radhard Sensors for BeamCal

  3. The International Linear Collider ILC ~ 30 km Parameters of the ILC: • e+e- accelerator, sc cavities, gradient 31.5 MV/m => 30km long • CMS energy: 200 to 500 GeV (possible upgrade to 1 TeV) • One interaction region, beam crossing angle of 14mrad and two detectors („push-pull“ scenario) • Peak luminosity: 2 x 1034 cm-2s-1 • typical beam size: (h x v) 650 nm x 5.7nm & beam intensity 2 x 1010 e+e- C.Grah: Radhard Sensors for BeamCal

  4. Very Forward Region of the ILC Detectors LumiCal • R&D of the detectors in the forward region is done by the FCAL Collaboration. • Precise (LumiCal) and fast (BeamCal) luminosity measurement • Hermeticity (electron detection at low polar angles) • Mask for the inner detectors • Not shown here: GamCal, a beamstrahlung photon detector at about 180m post-IP. TPC HCAL BeamCal ECAL C.Grah: Radhard Sensors for BeamCal

  5. The Beam Calorimeter - BeamCal BeamCal LDC Interaction point ~10cm ~12cm • Compact EM calorimeter with sandwich structure: • 30 layers of 1 X0 • 3.5mm W absorber and 0.3mm radiation hard sensor • Angular coverage from 5mrad to 28 mrad (6.0 > |η| > 4.3) • Moliére radius RM ≈ 1cm • Segmentation between 0.5 and 0.8 x RM Space for electronics C.Grah: Radhard Sensors for BeamCal

  6. 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: Radhard Sensors for BeamCal

  7. Diamond as Sensor Material • Manufacturing of diamond has become more and more available. CVD deposition of polycrystalline diamonds is available at wafer scale (3”-6” diameter) Properties: Diamond Silicon Hardness* 10,000 kg/mm2 1100 kg/mm2 Density 3.52 g/cm3 2.33 g/cm3 Atom density* 1.77 x 1023 1/cm3 0.50 x 1023 1/cm3 Thermal expansion coefficient 1.1 ppm/K 2.6 ppm/K Thermal conductivity* 20.0 W/cmK 1.412 W/cmK Dielectric strength 10 MV/cm 0.3 MV/cm Resistivity 1013 - 1016Ωcm 2.3 x 105Ωcm Electron mobility 2,200 cm2/Vs 1350 cm2/Vs Hole mobility 1,600 cm2/Vs 480 cm2/Vs Bandgap 5.45 eV 1.12 eV Energy/eh-pair 13eV 3.62 eV Av. eh/100μm (MIP) 3600 7800 *highest value of all solid materials (diamond values from Fraunhofer IAF webpage) C.Grah: Radhard Sensors for BeamCal

  8. 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: Radhard Sensors for BeamCal

  9. IV Characteristics • Typical current-voltage characteristics of a good pCVD diamond. • No breakthrough up to 500V. • Very low currents of a few picoamperes. • Symmetric (linear) behavior (ramping up) • Hysteresis observed for all pCVD samples (ramping down). C.Grah: Radhard Sensors for BeamCal

  10. MiP Response of pCVD Diamond PA Sr90 ADC diamond delay Sr90 source Scint. discr PM1 & Gate discr PM2 Preamplifier Sensor box Trigger box typical spectrum of an E6 sensor C.Grah: Radhard Sensors for BeamCal

  11. CCD Measurement ~ CCD CCD = Charge Collection Distance = mean drift distance of the charge carriers = charge collection efficiency x thickness Counts ADC Channels ~ charge C.Grah: Radhard Sensors for BeamCal

  12. CCD Behavior • CCD is a function of the applied electric field. • Saturation at about 1V/µm. C.Grah: Radhard Sensors for BeamCal

  13. 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: Radhard Sensors for BeamCal

  14. 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: Radhard Sensors for BeamCal

  15. 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 60 to 600 kGy/h Energy spectrum of shower particles in BeamCal V.Drugakov 6X0 C.Grah: Radhard Sensors for BeamCal

  16. 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: Radhard Sensors for BeamCal

  17. Testbeam Setup Beam Collimator Sensor Faraday Cup C.Grah: Radhard Sensors for BeamCal

  18. Results: CCD vs. Dose 100 nA (FAP5) 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: Radhard Sensors for BeamCal

  19. 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: Radhard Sensors for BeamCal

  20. CCD Behaviour after Irradiation ~ -80% ~ -30% after 7 MGy after 1.5 MGy C.Grah: Radhard Sensors for BeamCal

  21. 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: Radhard Sensors for BeamCal

  22. Monocrystalline CVD Diamond Sensors -25 V sCVD diamond area: a few mm2, ~thickness 300 µm, metallization Ø3mm IV Characteristics (too low current for our setup) 100% efficient at low electric fields! C.Grah: Radhard Sensors for BeamCal

  23. GaAs Sensor Material • Produced by the Siberian Instituteof Technology, Tomsk • semi-insulating GaAs doped by Sn (shallow donor) • compensated by Cr (deep acceptor):to compensate electron trapping centers EL2+ and provide i-type conductivity. C.Grah: Radhard Sensors for BeamCal

  24. 500 µm thick detector, divided into 87 5x5 mm pads Mounted on a 0.5 mm PCB with fanout Metallization is V (30 nm) + Au (1 µm) Works as a solid state ionization chamber and structure is provided by metallization (similar to diamond) GaAs Prototype Details C.Grah: Radhard Sensors for BeamCal

  25. Properties of the GaAs Sensor Rpad  500 MOhm, pad capacity about 12 pF, dark current 1 μA @ 500 V CCD = 50% of sensor thickness C.Grah: Radhard Sensors for BeamCal

  26. First View on Testbeam Results • Spatial CCD distribution corresponds to the beam profile • Pad with 2 CCD regions - due to collimation while irradiation → No trap diffusion • Dark current increased up to about 2 μA @ 500 V beam spot (~1 MGy) C.Grah: Radhard Sensors for BeamCal

  27. Radiation Hard Silicon guard rings 400 V reverse voltage depletion zone • mCz Si, radiation hard, thickness 380 μm, 5x5 mm2 • n+ on n-configuration • works as solid state ionization chamber, but active volume = depletion zone signal by drifting excess charge carriers • guard rings to avoid surface currents C.Grah: Radhard Sensors for BeamCal

  28. Radhard Silicon - Before Irradiation depletion voltage: 336 V → operational voltage 400 V C.Grah: Radhard Sensors for BeamCal

  29. Silicon - Under Irradiation • Intended as a first step using the radhard silicon • CCD remained constant • Noise increased strongly • No cooling Signal/Noise vs DOSE CCD vs DOSE preliminary C.Grah: Radhard Sensors for BeamCal

  30. Silicon Carbide • SiC is a potential sensor material with a high bandgap of > 3eV • First SiC material provided by the Technical University of Cottbus (BTU) • ~1cm2 size • very asymmetric behavior with high dark currents at low voltages => no signal detectable. • Need material with higher resistivity. C.Grah: Radhard Sensors for BeamCal

  31. Summary • The FCAL Collaboration develops the detectors in the very forward region of the ILC detectors. • BeamCal is an important part of the instrumentation. • The requirements on the radiation hardness and linearity of the sensors are challenging. • CVD diamonds, radiation hard silicon, GaAs and SiC are interesting materials for this task and are under investigation. http://www-zeuthen.desy.de/ILC/fcal/ C.Grah: Radhard Sensors for BeamCal

  32. luminosity detectors beam monitors Collaboration FCAL High precision design FCAL Collaboration Aim: design and construction of University of Colorado Brookhaven National Lab NY Yale University New Haven Laboratoire de l Accélérateur Linéaire Orsay Royal Holloway University London AGH University, Cracow Instituteof Nuclear Physics, Cracow DESY Joint Institute Nuclear ResearchDubna National Centerof Particle & HEP Minsk Prague Acad. of Science VINCA Inst. f. Nuclear Science Belgrade Tel Aviv University photon detectors http://www-zeuthen.desy.de/ILC/fcal/ EUROTeV, EUDET, NoRHDIA INTAS Cooperation with:SLAC Stanford University Iowa State University Wayne State University

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