CCD based Vertex Detector for GLC

1. CCD based Vertex Detector for GLC Yasuhiro Sugimoto KEK KEK/Niigata/Tohoku/Toyama Collaboration @VERTEX2003, Sep. 16, 2003 CCD based Vertex Detector for GLC

2. Contents • Project Overview of GLC • Accelerator • Detector • CCD Vertex Detector • Merit/Demerit of CCD at GLC/TESLA • R&D Status • Radiation Damage : Energy Dependence of Electron Damage • Dark Current, Flat-band Voltage Shift, Hot Pixels • Charge Transfer Inefficiency • Summary CCD based Vertex Detector for GLC

3. GLC Project • JLC has changed its name as GLC (Global Linear Collider) • 500GeV – 1TeV LC based on X-band linac • Future global organization is anticipated • Start experiment at 2013 CCD based Vertex Detector for GLC

4. GLC Accelerator CCD based Vertex Detector for GLC

5. GLC Acc. Parameters CCD based Vertex Detector for GLC

6. GLC Beam Structure GLC/NLC: Readout between trains ( 1 frame/6.7ms ) TESLA: Readout during trains ( 1 frame/50ms )  GLC/NLC is more favorable for vertex detectors CCD based Vertex Detector for GLC

7. GLC Detector CCD based Vertex Detector for GLC

8. GLC Detector CCD based Vertex Detector for GLC

9. CCD Vertex Detector • Merits of CCD for Vertex Detectors • Very thin (~20mm) sensitive region (=Epitaxial (p-type) layer)  Small multiple scattering • Diffusion of electrons in epitaxial layer • Key of excellent spatial resolution for CCD ( and CMOS ) • Takes time to diffuse : d = sqrt(Dt) ~ 6mm @ t=10ns  OK for GLC/NLC (Fully depleted CCD at TESLA) • CCD has simple structure • Large area sensor • High yield CCD based Vertex Detector for GLC

10. CCD Vertex Detector • Demerits of CCD for Vertex Detectors • Long charge transfer path • Charge transfer inefficiency (CTI) by traps created by radiation damage • Long readout time Multi-port readout CP-CCD CCD based Vertex Detector for GLC

11. CCD Vertex Detector • Baseline Design of GLC Vertex Detector • R=24, 36, 48, 60 mm • |cosq| < 0.9 • s = 4 mm • Wafer thickness = 300 mm • B = 3T  sb = 7 + 20/(pbsin3/2q) mm • This design is just a working assumption and the starting point of further R&D CCD based Vertex Detector for GLC

12. R&D Issues • Design Criteria : “The Highest Vertex Resolution with Technical Feasibility” • High spatial resolution of the sensors • Minimize multiple scattering  Thin wafer • Close to the IP  Radiation Hardness • Room temperature operation, if possible  Next milestone: sb = 5 + 10/(pbsin3/2q) mm CCD based Vertex Detector for GLC

13. R&D Status • Spatial Resolution: • < 3mm has been demonstrated by beam tests • Thin Wafer: • Partially thinned (honeycomb type) wafer is being designed ( average thickness ~ 100 mm ) • Radiation Damage Study: • Neutron damage study by Cf-252 • Electron damage study by Sr-90/150MeV beam CCD based Vertex Detector for GLC

14. Electron Damage Study • Damage in CCDs • Surface Damage • Due to dE/dx in SiO2 • Cause surface dark current and flat-band voltage shift • Bulk Damage • Due to lattice dislocation in Si bulk • Cause bulk dark current and CTI CCD based Vertex Detector for GLC

15. Electron Damage Study • Expected Beam Background at GLC CCD based Vertex Detector for GLC

16. Electron Damage Study • Test Sample CCDs • 256x256 pixcels • Made by Hamamatsu • Readout Freq : 250kHz • Readout Cycle : 2 sec • Irradiation: • Sr-90: 0.6, 1.0, 2.0 x 1011/cm2 • 150 MeV beam: 0.5, 1.0 x 1011/cm2 CCD based Vertex Detector for GLC

17. Electron Damage Study • NIEL Hypothesis • Bulk damage is thought to be proportional to non-ionizing energy loss (NIEL) • NIEL of electrons has strong energy dependence • e+/e- pair background hitting the inner-most layer of VTX at LC peaks at ~20MeV  High energy electron beam irradiation test CCD based Vertex Detector for GLC

18. Electron Damage Study • Dark Current • Surface dark current is very well suppressed by using MPP (multi pinned phase) mode (inverted mode) • In MPP mode, dark current is dominated by bulk current CCD based Vertex Detector for GLC

19. Electron Damage Study • Dark Current Pedestal • In MPP mode, however, spurious dark current (dark current pedestal: DCP) which is generated during clocking is observed • This DCP is thought to be due to impact ionization by holes trapped in interface levels CCD based Vertex Detector for GLC

20. Electron Damage Study • Flatband Voltage Shift • Surface damage in SiO2 causes shift of operation voltage • FVS is observed as shift of MPP threshold CCD based Vertex Detector for GLC

21. Electron Damage Study • Hot Pixels CCD based Vertex Detector for GLC

22. Electron Damage Study • Hot pixels • Average dark current of 150MeV beam irradiated CCD is x2~5 larger than Sr-90 irradiated CCD • But hot pixel generation rate is completely different • This could be due to threshold effect of cluster-defect generation CCD based Vertex Detector for GLC

23. Electron Damage Study • Charge Transfer Inefficiency (CTI) CCD based Vertex Detector for GLC

24. Electron Damage Study • CTI Model Calculation CCD based Vertex Detector for GLC

25. Electron Damage Study • Other CTI Improvements • Notch Channel CCD based Vertex Detector for GLC

26. Electron Damage Study • Other CTI Improvements (cont.) • Reduction of number of transfer  Multi Thread CCD (MT-CCD) CCD based Vertex Detector for GLC

27. Summary CCD based Vertex Detector for GLC

28. Summary (cont.) CCD based Vertex Detector for GLC