1. Heavy ion irradiation on silicon strip sensors for GLAST S.Yoshida, K.Yamanaka, T.Ohsugi, H.Masuda T.Mizuno, Y.Fukazawa (Hiroshima Univ.) Y.Iwata, T.Murakami (NIRS) H.Sadrozinski (SCIPP,UCSC) K.Yamamura, K.Yamamoto, K.Sato (HPK)

2. GLAST (Gamma-ray Large Area Space Telescope) e+e+ e-e-  Array of Silicon Strip Sensor Detect gamma-ray through e + e - conversion

3. GLAST prototype sensor Single-sided, N-bulk,P-strip AC coupling readout 448 strips 208  m strip pitch 9.5cm ↑ quarter

4. The Aim of the heavy ion irradiation (1) Investigate radiation damage due to high dE/dx particles. →slowed-down Fe ions (8GeV/g/cm 2 = 5000×MIP) check items : full depletion voltage, leakage current, coupling capacitance, inter strip capacitance (2)Investigate the differece between Crystal Orientations. and Al p + strip n+n+ SiO 2 Si bulk The difference comes from the nature of the interface between the SiO 2 layer and the Si bulk

5. Irradiation (HIMAC@NIRS, Japan) Fe ion 500MeV/n Absorber to slow down Fe ions Sensor (in the box) 150V bias dE/dx= 8GeV/g/cm 2

6. 410  m thick 320  m thick Fe ion dose “10 krad” 111,10krad (7.8 krad) 100,10krad (7.4 krad) Fe ion dose “30 krad” 111,30krad (23.3 krad) 100,30krad (21.2 krad) Iradiated Sensors (4 sensors) Expected dose for 5 years GLAST mission: 1 krad

7. Full Depletion Voltage 111(410  m) : 100V 100(320  m) : 80V

8. Leakage Current 111 (410  m) 100 (320  m) ↑ full depletion voltage

9. Leakage Current (strip) 111(10krad) before irradiation after irradiation leakage current is very uniform (before and after) no dead or noisy channel (before and after) 100(10krad) after irradiation before irradiation

10. Leakage Current vs Dose 100 10krad 111 10krad 100 30krad 111 30krad Leakage current is generated in bulk no difference between 111 and 100 10nA/cm 2 /krad: typically expected for ionizing damage

11. Coupling Capacitance after irradiation before irradiation Readout strip: grounded 111(10krad) None of the coupling capacitors were broken. No differences between grounded strips and floating strips. 100(10krad) Readout strip: grounded after irradiation before irradiation Al strip SiO2 p + strip Si bulk n+n+ Al +150V 40M 

12. Inter strip Capacitance Readout strip: grounded after irradiation before irradiation after irradiation before irradiation 111(10krad)100(10krad) No differences between before and after the irradiation. No differences between grounded strips and floating strips.

13. Conclusion Full Depletion Voltage: No significant differences between before and after the irradiation. Leakage Current: The increase after the irradiation is as expected from total dose. The strip current are very uniform before and after the irradiation. Coupling Capacitance: None of strip were broken. Inter Strip Capacitance: No significant difference between before and after the irradiation. None of the strips has become insensitive. No significant differences between and. No differences between grounded strips and floating strips.

14. Full Depletion Voltage 111(410μm) ～ 100V 100(320μm) ～ 80V

15. 111 (410μm) 100 (320μm) Leakage Current

16. 111(30krad) after irradiation before irradiation 100(30krad) after irradiation before irradiation Leakage Current (strip) very uniform (before and after the irradiation) no dead or noisy channel (before and after)

17. 111(30krad)100(30krad) after irradiation before irradiation after irradiation before irradiation Readout strip: grounded Coupling Capacitance None of the coupling capacitors were broken. No differences between grounded strips and floating strips.

18. Inter strip Capacitance No differences between before and after the irradiation. No differences between grounded strips and floating strips. 111(30krad)100(30krad) Readout strip: grounded after irradiation before irradiation after irradiation before irradiation