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

11/09/2006 C.Grah: CVD Diamonds2 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

11/09/2006 C.Grah: CVD Diamonds3 Very Forward Region of the ILC Detectors Interaction point  The purpose of the instrumentation of the very forward region is:  Hermeticity: increase the coverage to polar angles > 5mrad  Optimize Luminosity  EM calorimeter with sandwich structure:  30 layers of 1 X 0 o3.5mm W and 0.3mm sensor  Angular coverage from 5mrad to 28 mrad  Moliére radius R M ≈ 1cm  Segmentation between 0.5 and 0.8 x R M BeamCal LDC

11/09/2006 C.Grah: CVD Diamonds4 The Challenges for BeamCal  e+e- pairs from beamstrahlung are deflected into the BeamCal  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 e-e- e+e+ Creation of beamstrahlung at the ILC ≈ 1 MGy/a ≈ 5 MGy/a e-e- e-e- γ e-e- γ e+e+ e.g. Breit-Wheeler process

11/09/2006 C.Grah: CVD Diamonds5 Polycrystalline Chemical Vapour Deposited Diamonds  pCVD diamonds are an interesting material:  radiation hardness (e.g. LHC pixel detectors)  advantageous properties like: high mobility, low ε R = 5.7, thermal conductivity  availability on wafer scale  Samples from two manufacturers are under investigation:  Element Six TM  Fraunhofer Institute for Applied Solid-State Physics – IAF  1 x 1 cm 2  μm thick (typical thickness 300μm)  Ti(/Pt)/Au metallization (courtesy of IAF)

11/09/2006 C.Grah: CVD Diamonds6 Linearity Test at CERN PS Hadronic beam, 3 & 5 GeV Fast extraction mode ~ particles / ~10 ns ADC signal gate 10 ns 17 s Diamond Setup Beam Scint.+ PMTs. Response of diamond sensor to beam particles (no preamplifier/attenuated) Photomultiplier signals

11/09/2006 C.Grah: CVD Diamonds7 Response vs. Particle Fluence 30% deviation from a linear response for a particle fluence up to ~10 6 MIP/cm 2 The deviation is at the level of the systematic error of the fluence calibration. E64 FAP2 Fraunhofer IAF Element Six

11/09/2006 C.Grah: CVD Diamonds8 High Dose Irradiation  Irradiation up to several MGy using the injector line of the S-DALINAC: 10 ± MeV and beam currents from 10 to 100 nA corresponding to about 59 to 590 kGy/h Superconducting DArmstadt LINear ACcelerator Technical University of Darmstadt Energy spectrum of shower particles in BeamCal V.Drugakov 2X 0

11/09/2006 C.Grah: CVD Diamonds9 Preparations and Programme GEANT4 simulation of the geometry => R = N FC /N Sensor = 0.98 /particle = 5.63 MeV/cm Beam setup SampleThickness, µm Dose, MGy E6_B2 (E6)500>1 DESY 8 (IAF)300>1 FAP 5 (IAF)470>5 E6_4p (E6)470>5 Apply HV to the DUT Measure CCD ~20 min Irradiate the sample ~1 hour CCD: Charge Collection Distance collimator preamp box absorber

11/09/2006 C.Grah: CVD Diamonds10 Realization: Beam Setup exit window of beam line collimator (I Coll ) sensor box (I Dia, T Dia, HV) Faraday cup (I FC, T FC )

11/09/2006 C.Grah: CVD Diamonds11 CCD Setup typical spectrum of an E6 sensor Sr90 source Preamplifier Sensor box Trigger box & Gate PA discr delay ADC Sr 90 diamond Scint. PM1 PM2 Setups partly financed by EUDET.

11/09/2006 C.Grah: CVD Diamonds12 Results: CCD vs. Dose 100 nA (E6_4p)100 nA (FAP5) Silicon starts to degrade at 30 kGy. High leakage currents. Not recoverable. CCD = Q meas /Q induced x thickness Bias voltage = 400V ≈> 1 V/μm After absorbing 7MGy: CVD diamonds still operational.

11/09/2006 C.Grah: CVD Diamonds13 Behaviour after Irradiation Slight increase of currents for higher doses. No significant change of the current-voltage characteristics up to 1.5 MGy.

11/09/2006 C.Grah: CVD Diamonds14 CCD Behaviour after Irradiation after 1.5 MGy ~ -30% ~ -80% after 7 MGy

11/09/2006 C.Grah: CVD Diamonds15 After Irradiation: IAF Sample strong „pumping“ behaviour. before/after ~ 7MGy signal recovery after 20 Gy ▪ FAP 5 irradiated, 1st measurement ▪ FAP 5 irradiated, additional 20 Gy ▪ before irradiation ▪ after irradiation

11/09/2006 C.Grah: CVD Diamonds16 Summary  PCVD diamonds are an interesting material as sensors for the BeamCal.  The linearity of pCVD diamonds up to particle fluences of 10 6 particles/cm 2 /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.