1. Measurements on Single and Poly Crystal CVD Diamond Sensors
Christian Grah, Desy
FCAL Workshop
12-13 February
Cracow

2. Contents
Low dose rate irradiation of polycrystalline CVD sensors, measure the Charge Collection Distance, CCD vs dose
E64
Desy7
Single crystal diamond IV
Individual spectra
CCD vs HV/time
Summary & outlook
FCAL Workshop Cracow, Feb 2006
C.Grah: Diamond Sensors

3. Low Dose Rate Irradiation
Usually irradiation in our laboratory is done by:
Irradiation with closest possible distance between source and sensor (typically 2.6 cm) to achieve high dose rate.
Measure the CCD of the sensor in regular time intervals with a reasonable distance to prevent a high double hit rate (typically 7.5cm).
This enables for reproducible measurements on a timescale of several days to get into the 100 Gy range of accumulated dose.
BUT: need of an operator
LOW DOSE RATE IRRADIATION: => automatic CCD measurement at low dose rate, but needs much more time.
Did this at the time of the TAU workshop 2005.
FCAL Workshop Cracow, Feb 2006
C.Grah: Diamond Sensors

4. CCD Measurement
Use the high energetic part of a Sr90-β- source => MIP spectrum.
Δt = 30min
FCAL Workshop Cracow, Feb 2006
C.Grah: Diamond Sensors

5. E64 Irradiations
Have done 2 irradiation periods with different dose rates:
29.8. – 5.9. (~7d)
6.9. – (~64d)
FCAL Workshop Cracow, Feb 2006
C.Grah: Diamond Sensors

6. Desy7 and Desy8 Got these two new samples in Nov. 06.
The samples are 300 μm thick and 12x12 mm in size.
The metallization is 10x10 mm in size divided into 4 pads on one side.
100 nm Ti nm Pt nm Au.
Material selection was with focus on avoiding micro cracks.
FCAL Workshop Cracow, Feb 2006
C.Grah: Diamond Sensors

7. Desy7 and Desy8 (cont.) FAP7 series
pCVD Diamonds from Freiburg (Fraunhofer IAF)
Main issue from former samples:
micro cracks
IV behavior
CCD performance
CCD vs irradiation
Large part of the measurements were presented by K. Afanaciev. Much better performance than earlier samples.
Issue of signal decreasing with time.
FAP7 series
FCAL Workshop Cracow, Feb 2006
C.Grah: Diamond Sensors

8. Spectra of Desy7 Shortly after switching the
high voltage a large signal is
measured.
Took pedestal as determined
by the early measurements
and fixed it for the rest.
FCAL Workshop Cracow, Feb 2006
C.Grah: Diamond Sensors

9. Low Dose Rate Result switching voltage Stable signal!
FCAL Workshop Cracow, Feb 2006
C.Grah: Diamond Sensors

10. BDS7 - IV Started to investigate a sCVD Diamond.
Got the sample (BDS7) in December from the GSI Darmstadt.
5 x 5 x mm3 ; Cr(50 nm)Au (100 nm) or Ti(30nm)Pt(50nm)Au(100nm)
known “breakthrough”
FCAL Workshop Cracow, Feb 2006
C.Grah: Diamond Sensors

11. Mip signal of BDS7 FCAL Workshop Cracow, 12-13 Feb 2006
C.Grah: Diamond Sensors

12. BDS7 CCD The single crystal diamond shows a high (100%) and
thickness
The single crystal diamond shows a high (100%) and
stable (t) signal even at low E-field.
FCAL Workshop Cracow, Feb 2006
C.Grah: Diamond Sensors

13. Summary
Have tested sensors from E6 and IAF (Freiburg) up to highest doses so far in our lab (>250 Gy).
Desy7 and Desy8 show a small but stable signal and did not show any microcrack related problem.
Started to test a single crystal diamond (sCVD) from E6.
Superior efficiency at low E-field and very stable behaviour of the sCVD sample.
FCAL Workshop Cracow, Feb 2006
C.Grah: Diamond Sensors

14. Outlook
We will get pCVD samples back from Freiburg with annealed metallization. Expected this week.
Waiting for new thin samples from Freiburg from a dedicated wafer with reduced nitrogen concentration during growth.
We will have a testbeam period (end of April) at the TU Darmstadt DALINAC (10MeV and ~15Gy/s) and will investigate high dose behavior of diamonds.
sCVD diamonds are interesting but they are not (yet) available on waferlevel. Will follow the development of this technology.
FCAL Workshop Cracow, Feb 2006
C.Grah: Diamond Sensors