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

2. J.Harkonen and Z.Li, LHCC open session, CERN, 24th November 2004. CERN RD39 Collaboration: Cryogenic Tracking Detectors OUTLINE Trapping: A limiting factor for detector operation RD39 Strategy for radiation hardness up to 10 16 n eq /cm 2 Charge Injected Detector CID Experimental results Cryogenic detector module activities Summary Workplan for 2005

3. J.Harkonen and Z.Li, LHCC open session, CERN, 24th November 2004. 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 v th saturates at 20 kV/cm E-field to  10 7 cm/s 10 16 n eq /cm 2 irradiation produces N T  3-5*10 15 cm -3 with  10 -15 cm 2 Particle generated charge carrier drifts 20-30  m before it gets trapped regardless whether the detector is fully depleted or not ! 10 16 n eq /cm 2 radiation load: 80-90% of the volume of d=300  m detector is dead space !

4. J.Harkonen and Z.Li, LHCC open session, CERN, 24th November 2004. 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 3.75·10 15 cm –2 Bias potential 300 V (Q col ) or 0 V (Q pol ; 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*10 15 n/cm 2

5. J.Harkonen and Z.Li, LHCC open session, CERN, 24th November 2004. CERN RD39 Collaboration: Cryogenic Tracking Detectors DETRAPPING The detrapping time-constant depends exponentially on T If a trap is filled (electrically non- active) the detrapping time-constant is crucial For A-center (O-V at E c -0.18 eV with  10 -15 cm 2 )

6. J.Harkonen and Z.Li, LHCC open session, CERN, 24th November 2004. CERN RD39 Collaboration: Cryogenic Tracking Detectors RD39 Strategy for radiation hardness up to 10 16 n eq /cm 2 The detector CCE can be considered to be a product of two factors:, Depletion term Trapping term o Electric field manipulation to increase depletion depth w (original Lazarus effect) CCE GF ~ 1 o Freeze out trapping effect at T lower than LHe T CCE t ~ 1

7. J.Harkonen and Z.Li, LHCC open session, CERN, 24th November 2004. P+P+ P+P+ JpJp J p = epμE divJ=0 divE=p tr E(x=0) = 0 (SCLC mode) E(x) ~ V √ X J(V) = V 2 E(x) The key advantage: The shape of E(x) is not affected by N mgl, and stable at any fluence Current injected detector (principle of operation) x d +

8. J.Harkonen and Z.Li, LHCC open session, CERN, 24th November 2004. E(x) xxxx Ohmic mode p >>p tr E(x) = V/d J ~ V “Diode” mode p>p tr E(x) ~ E(0) + ax DL saturation p >> p tr E(x) = ax SCLC mode N dl >p tr E(x) ~ SQR(x) J ~ V 2 Evolution of E(x) in CID with the injected current

9. J.Harkonen and Z.Li, LHCC open session, CERN, 24th November 2004. log J log V Ohmic, J ~ V SCLC, J ~ V 2 DL saturation “Diode” I-V characteristic of CID Proof of CID concept: – observation of SCLC and DL saturation behavior Problem: - optimal range of V for CID operation

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

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

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

13. J.Harkonen and Z.Li, LHCC open session, CERN, 24th November 2004. Reproducibility of CID technology (detector dark current) J=V 2 /d 3

14. J.Harkonen and Z.Li, LHCC open session, CERN, 24th November 2004. Reproducibility of CID technology (threshold voltage) V thr = N tr ·d 2 V thr ~ Φ·d 2

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

16. J.Harkonen and Z.Li, LHCC open session, CERN, 24th November 2004. 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 Conclusions

17. J.Harkonen and Z.Li, LHCC open session, CERN, 24th November 2004. 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 ?

18. J.Harkonen and Z.Li, LHCC open session, CERN, 24th November 2004. CERN RD39 Collaboration: Cryogenic Tracking Detectors LOW TEMPERATURE SUMMARY Readout electronics becomes faster and has lower noise 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)

19. J.Harkonen and Z.Li, LHCC open session, CERN, 24th November 2004. 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)  60 Co (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

20. J.Harkonen and Z.Li, LHCC open session, CERN, 24th November 2004. 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. 1.Testing of new etching techniques of edgeless detectors. 2.Improving the cryomodule operation below 200K 3.Module construction of CID strip detectors. Cryomodules