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CERN RD39 Collaboration: Cryogenic Tracking Detectors

CERN RD39 Collaboration: Cryogenic Tracking Detectors. RD39 Status Report 2004. Jaakko Härkönen Helsinki Institute of Physics, Finland. Zheng Li Brookhaven National Laboratory, USA. CERN RD39 Collaboration: Cryogenic Tracking Detectors. OUTLINE.

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CERN RD39 Collaboration: Cryogenic Tracking Detectors

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  1. CERN RD39 Collaboration: Cryogenic Tracking Detectors RD39 Status Report 2004 Jaakko Härkönen Helsinki Institute of Physics, Finland Zheng Li Brookhaven National Laboratory, USA J.Harkonen and Z.Li, LHCC open session, CERN, 24th November 2004.

  2. CERN RD39 Collaboration: Cryogenic Tracking Detectors OUTLINE • Trapping: A limiting factor for detector operation • RD39 Strategy for radiation hardness up to 1016 neq/cm2 • Charge Injected Detector CID • Experimental results • Cryogenic detector module activities • Summary • Workplan for 2005 J.Harkonen and Z.Li, LHCC open session, CERN, 24th November 2004.

  3. CERN RD39 Collaboration: Cryogenic Tracking Detectors Trapping: A limiting factor for detector operation The trapping time-constant is not dependent on T The thermal velocity vth saturates at 20 kV/cm E-field to 107cm/s 1016 neq/cm2irradiation produces NT3-5*1015 cm-3 with 10-15cm2 Particle generated charge carrier drifts 20-30m before it gets trapped regardless whether the detector is fully depleted or not ! 1016 neq/cm2 radiation load: 80-90% of the volume of d=300m detector is dead space ! J.Harkonen and Z.Li, LHCC open session, CERN, 24th November 2004.

  4. CERN RD39 Collaboration: Cryogenic Tracking Detectors HOW A TRAP CAN BE NEUTRALIZED ? By filling them with current/charge or light injection. • p+np+ symmetric structure irradiated to 3.75·1015 cm–2 • Bias potential 300 V (Qcol) or 0 V (Qpol ; the electric field is induced by the polarization of the detector) • The p+np+ detector with this fluence can be operated already at 100 V bias • Standard p+nn+ detector would deplete fully only above 1 kV bias at this fluence CID (Charge Injected Detector) irradiated with 3,8*1015 n/cm2 J.Harkonen and Z.Li, LHCC open session, CERN, 24th November 2004.

  5. CERN RD39 Collaboration: Cryogenic Tracking Detectors DETRAPPING If a trap is filled (electrically non-active) the detrapping time-constant is crucial The detrapping time-constant depends exponentially on T For A-center (O-V at Ec-0.18 eV with  10-15 cm2 ) J.Harkonen and Z.Li, LHCC open session, CERN, 24th November 2004.

  6. CERN RD39 Collaboration: Cryogenic Tracking Detectors RD39 Strategy for radiation hardness up to 1016 neq/cm2 The detector CCE can be considered to be a product of two factors: Trapping term Depletion term • Electric field manipulation to increase depletion depth w (original Lazarus effect) • CCEGF~ 1 • Freeze out trapping effect at T lower than LHe T • CCEt~ 1 , J.Harkonen and Z.Li, LHCC open session, CERN, 24th November 2004.

  7. Current injected detector (principle of operation) x d Jp = epμE divJ=0 divE=ptr E(x=0) = 0 (SCLC mode) + Jp P+ P+ E(x) E(x) ~V √ X J(V) = V2 The key advantage: The shape of E(x) is not affected by Nmgl, and stable at any fluence J.Harkonen and Z.Li, LHCC open session, CERN, 24th November 2004.

  8. E(x) Evolution of E(x) in CID with the injected current E(x) E(x) E(x) x x x x “Diode” mode p>ptr E(x) ~ E(0) + ax SCLC mode Ndl>ptr E(x) ~ SQR(x) J ~ V2 DL saturation p >> ptr E(x) = ax Ohmic mode p>>ptr E(x) = V/d J ~ V J.Harkonen and Z.Li, LHCC open session, CERN, 24th November 2004.

  9. log J DL saturation SCLC, J ~ V2 “Diode” Ohmic, J ~ V log V I-V characteristic of CID Proof of CID concept: – observation of SCLC and DL saturation behavior Problem: - optimal range of V for CID operation J.Harkonen and Z.Li, LHCC open session, CERN, 24th November 2004.

  10. CID I-V simulation software J.Harkonen and Z.Li, LHCC open session, CERN, 24th November 2004.

  11. CID I-V characteristics J.Harkonen and Z.Li, LHCC open session, CERN, 24th November 2004.

  12. CID I-V characteristics Experimental and simulated IV’s of CIDs @ 220K Decreasing I with fluence !! J.Harkonen and Z.Li, LHCC open session, CERN, 24th November 2004.

  13. Reproducibility of CID technology (detector dark current) J=V2/d3 J.Harkonen and Z.Li, LHCC open session, CERN, 24th November 2004.

  14. Reproducibility of CID technology (threshold voltage) Vthr= Ntr·d2 Vthr~ Φ·d2 J.Harkonen and Z.Li, LHCC open session, CERN, 24th November 2004.

  15. CCE measurements Injection mode Standard mode J.Harkonen and Z.Li, LHCC open session, CERN, 24th November 2004.

  16. Conclusions • Silicon P+ - n – N+ and P+ - n – P+ structures heavily irradiated by neutrons operate in SCLC mode with hole injection • The I-V threshold voltage and the dark current are in the range of hundreds volts, which fits to the detector application requirements • CID I-Vs are stable under irradiation • Technology of CIDs is developed with pre-irradiation by neutrons • No effect for the detector performance by: • type of Si • technology • The developed software for CIDs engineering allows proper simulation of I-Vs with two key physical parameters: • Deep trap activation energy of 0.48eV from the valence band • Deep trap concentration proportional to fluence J.Harkonen and Z.Li, LHCC open session, CERN, 24th November 2004.

  17. CERN RD39 Collaboration: Cryogenic Tracking Detectors CHARGE INJECTION SUMMARY If a trap level is filled (say, by current or charge injection) and then frozen (very long detrapping time) at cryogenic temperatures, this trap level will no longer be able to trap free carriers again, and it becomes electrically inactive. In this case, the CCE can be improved as well to a value close to 1 CCE can be increased close to 1 by manipulating the electric field in the detector via current and/or charge injection at temperatures from 130 K to 150 K. Feasible solution for very high luminosity colliders ? J.Harkonen and Z.Li, LHCC open session, CERN, 24th November 2004.

  18. CERN RD39 Collaboration: Cryogenic Tracking Detectors LOW TEMPERATURE SUMMARY No leakage current >> low electrical power from HV supply Low depletion voltage (original Lazarus effect) CCE increase without reduction of detector thickness (increase of charge collection depth) Readout electronics becomes faster and has lower noise J.Harkonen and Z.Li, LHCC open session, CERN, 24th November 2004.

  19. CERN RD39 Collaboration: Cryogenic Tracking Detectors RD39 RESOURCES *Device processing: Brookhaven National Laboratory BNL (USA), Ioffe PTI (Russia), Helsinki Institute of Physics HIP (Finland). *Irradiations: protons (Accelerator Laboratory,Univ. of Jyvaskyla,Univ. of Karlsruhe) neutron (Jozef Stefan Institute JSI, Ljubljana)  60Co(Brookhaven National Laboratory) *Characterizations: CCE JSI, FCT Algarve University, Faro, Portugal DLTS Univ. of Florence, PTI TCT BNL, PTI CV/IV Practically all member institutes J.Harkonen and Z.Li, LHCC open session, CERN, 24th November 2004.

  20. CERN RD39 Collaboration: Cryogenic Tracking Detectors RD39 WORKPLAN FOR 2005 • Device Physics and Basic Research • Optimization of Deep Level (DL) spectra by CID pre-irradiation and intentional contamination. • CCE measurements on CID pre-irradiated by protons and neutrons • Strip detectors based on CID approach (strips). • Completetion of LH TCT setup construction at CERN cryolab. • Cryomodules • Testing of new etching techniques of edgeless detectors. • Improving the cryomodule operation below 200K • Module construction of CID strip detectors. J.Harkonen and Z.Li, LHCC open session, CERN, 24th November 2004.

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