Properties of Recent SIC Crystals

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Properties of Recent SIC Crystals

• Rihua Mao
• Shanghai Institute of Ceramics

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Contents

• Samples pretreatment
• Measurement methods
• Results

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Samples pretreatment
CMS Endcap Crystal

• 15 EE crystals produced in Jun at SIC by Modified
  Bridgman method were evaluated.
• All crystals were annealed _at_ 200 centigrade for
  4Hrs before test.

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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.

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Measurement methods 1L.Transmittance

• Longitudinal transmittance were measured by a
  Shimadzu - 2501 UV/Visible spectrophotometer
  equipped with a large sample compartment.

Optical layout of the spectrophotometer
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Measurement methods 2Light 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
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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 irradiated _at_ 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.

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Measurement methods 3Radiation hardness
Co60 source, up to 300 rad/h
Lead shell
PWO crystal
PMT
Layout of irradiation facility
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ResultsL. Transmittance - 1

• L. Transmittance as a function of wavelength for
  SIC76, 78 and 79.
• The ideal transmittance is calculated using
  equation

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ResultsL. Transmittance - 2

• The average L.T. _at_ 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.

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ResultsL. Transmittance - 3
Quite good _at_ 420 nm

• L.T. _at_ 420 nm for all crystal is larger than 55,
  and the mean value is 65.

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ResultsL. Transmittance - 4

• The mean value _at_ 620 nm is about 72, showing
  good transmittance at long wavelength.

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ResultsLight 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

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ResultsLight 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
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ResultsLight 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.
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ResultsLight output - 4
Measurement done _at_ Caltech
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ResultsLight 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.

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ResultsRadiation 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
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ResultsRadiation 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
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Summary

• Longitudinal transmittance of recent SIC crystals
  _at_ 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.