1. Properties of Recent SIC Crystals
Rihua Mao
Shanghai Institute of Ceramics

2. Contents
Samples & pretreatment
Measurement methods
Results

3. Samples & pretreatment
CMS Endcap Crystal
15 EE crystals produced in Jun at SIC by Modified Bridgman method were evaluated.
All crystals were 200 centigrade for 4Hrs before test.

4. Experiment Properties measured: transmittance and Light output.
Three samples, SIC70, 76 and 78, were irradiated at 15 rad/h and 300 rad/h step by step to evaluate the radiation hardness.

5. Measurement methods – 1 L.Transmittance
Longitudinal transmittance were measured by a Shimadzu UV/Visible spectrophotometer equipped with a large sample compartment.
Optical layout of the spectrophotometer

6. Measurement methods – 2 Light output
The crystals were excited by a collimated Cs-137 source, and L.O. was measured by using XP2262B PMT.
Room temperature was set to be 24oC.
The Big End of the crystal was coupled to PMT with silicon oil, while all other surfaces were wrapped with two layers of Tyvek paper to increase the collected light.
Schematic setup for L.O. measurement

7. Measurement methods – 3 Radiation hardness
Radiation hardness was measured at USTC. A Co-60 source which provides dose rate of up to 300 rad/h was used.
The crystals were front 15 rad/h and 300 rad/h step by step until saturation. L.O. before and after irradiation were measured to evaluate the radiation damage.

8. Measurement methods – 3 Radiation hardness
Co60 source, up to 300 rad/h
Lead shell
PWO crystal
PMT
Layout of irradiation facility

9. Results L. Transmittance - 1
L. Transmittance as a function of wavelength for SIC76, 78 and 79.
The ideal transmittance is calculated using equation:

10. Results L. Transmittance - 2
The average 360 nm of 15 SIC EE crystals is 24.8%, which is lower than previous crystals’. Further studies is needed to find out the reasons.

11. Results L. Transmittance - 3
Quite 420 nm
420 nm for all crystal is larger than 55%, and the mean value is ~65%.

12. Results L. Transmittance - 4
The mean 620 nm is about 72%, showing good transmittance at long wavelength.

13. Light output is shown as function of integration time for SIC-76
Results Light output - 1
Light output is shown as function of integration time for SIC-76
L.O. for SIC-76.
Total L.O. is 11.1 p.e./MeV
The ratio of L.O. between 100 and 1000 ns is 98%

14. Light output is shown as function of integration time for SIC-76
Results Light output - 2
Total L.O. is 11.6 p.e./MeV
The ratio of L.O. between 100 and 1000ns is 97%
Light output is shown as function of integration time for SIC-76

15. Results Light output - 3
The ratio of L.O. between 100 and 1000ns is 97%.
As can be seen, SIC crystals are fast decay. This is consistent with previous result.

16. Measurement done @ Caltech
Results Light output - 4
Measurement Caltech

17. Results Light output - 5 Summary L.O.
Average L.O. of 15 SIC PWO crystals is 11.5 p.e./ MeV measured by using a XP2262B PMT.

18. Results Radiation damage - 1
Radiation damage for SIC-76 (without temperature correction).
L.O. degradation after 15 rad/h is ~5%, and
A damage of ~13% is found after 300 rad/h irradiation.
Before irradiation 5%
15 rad/h saturate
13%
300 rad/h saturate

19. Results Radiation damage - 2
Radiation damage for SIC-78 (without temperature correction).
L.O. degradation after 15 rad/h is ~4%, and
A damage of ~7% is found after 300 rad/h irradiation.
Before irradiation
15 rad/h
300 rad/h

20. Summary
Longitudinal transmittance of recent SIC 360 nm is slightly lower than previous crystals. Further studies are needed to find out the reasons.
L.T. at 420 and 620 nm for SIC crystals are good enough.
Recent SIC crystals are fast decay with an average L.O. of 11.5 p.e./MeV.
Radiation damage of three crystals studied with front irradiation dose rate of 300 rad/h varies from 7% to 13%. Further research to improve the uniformity of radiation hardness is needed.