Diamond Sensor Tests for the CMS BCM Alexandr Ignatenko FCAL collaboration meeting May 7, 2008

2 FCAL collaboration meeting2 Overview  BRM system overview  Standard set of measurements in Zeuthen  Thickness  Capacitance  I-V characteristic  Charge collection distance  Results  Usual behavior  Abnormal cases  Conclusion

May 7, 2008FCAL collaboration meeting3 The components:

May 7, 2008FCAL collaboration meeting4 BCM1, 1.8m BCM2+BSC2, 14.4m

5May 7, 2008FCAL collaboration meeting5 Thickness and capacitance measurements Thickness: mechanically with 10 µm precision Values µm A sensor assembled in the frame Capacitance: with LCR meter HP 4263A pF

6 I-V characteristic N 2 atmosphere V 50V/30 sec steps Voltage source and picoamperemeter: Keithley 487 May 7, 2008FCAL collaboration meeting

7 Charge collection efficiency  = Q meas /Q ind Charge collection distance CCD =  × d May 7, 2008FCAL collaboration meeting Detection mechanism traps Charge collection distance (CCD)

May 7, 2008FCAL collaboration meeting8 CCD setup

99 ~ CCD CCD = (Mean-Ped)×calib×corr/N exp May 7, 2008 FCAL collaboration meeting Typical spectrum CCD = (MPV-Ped)*calib/N exp

1010 May 7, 2008FCAL collaboration meeting CCD setup Source holder with collimator Sensor box Trigger box Low voltage power supply HV supply and picoampearmeter

Results Normal behavior P28 depumped pumped negative positive May 7, FCAL collaboration meeting

1212 CCD vs dose, pumping May 7, 2008FCAL collaboration meeting The current in the sensor circuit was monitored CCD dependence on dose, Gy/h irradiation started

13 13 CCD dependence on time for the fully pumped sensors May 7, 2008FCAL collaboration meeting The current in the sensor circuit was monitored After additional 60 mGy 200 V applied 400 V applied

Abnormal cases P18 Depumped statePumped state Currents up to hundreds of nA at high bias voltages May 7, FCAL collaboration meeting

P 45 depumped pumped May 7, FCAL collaboration meeting

1616 Currents had changed in time even without irradiation May 7, 2008FCAL collaboration meeting

1717May 7, 2008FCAL collaboration meetingConclusion  25 samples have been investigated  The characterization of each sample has been given  6 sensors have shown unstable currents currents  The parameters of the sensor were reproducible