Mo`module analysis

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APD GAIN MEASUREMENTS AT H4
F. Cavallari (Roma), M. Obertino (Minnesota)
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Summary

• Method
• Data available
• Preliminary results

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APD GAIN measured by Hamamatsu
a50
G50

• HV at H4 is not exactly
• V50 for every APD.
• To estimate G at H4 for M0
• we can use
• Hamamatsu measurements
• M0 data

V50
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GAPD from M0 datamethod(I)

• APD gain cannot be directly measured at H4 ( is
  difficult
• to measure the signal for very low bias voltage )
• BUT
• we can
• determine a (see CMS IN 2001/33)
• find a relation between a and the APD gain
• use this relation to calculate the APD gain

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GAPD from M0 datamethod(II)

• At H4 a can be determined perfoming an mini HV
  scan
• around the working point (Vn)

at the voltage VN
where
G APD gain
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GAPD from M0 data method(III)
This analysis is based on ROOT preprocessed data
Pulse shape fit meth. 1
Ratio Laser/PIN fitted with a Gaussian
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GAPD from M0 data Method (III)
To reconstruct laser signal we use pulse shape
fit method 1
M0,1,2
M4
M3
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HV SCANS

• 2 HV SCANS
• 1 NOV ( 20OC )
• 7 NOV ( 18OC )

• CH3 ( Vn355V )
• 5 HV Steps
• 350
• 352.5
• 355
• 357.5
• 360

• CH2 (Vn360 V)
• 5 HV Steps
• 355
• 357.5
• 360
• 362.5
• 365

CH3
CH2
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am vs Gain_Hamamatsu
18o
20o
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(aM a50 )vs Gain_Hamamatsu
In order to be indipendent from APD type we fit
the distribution
(aM a50 )
(aM a50 )AB Gain_Ham
Ham.
From this formula we can calculate the G_tb for
each APD
Test beam
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Difference between G_Ham and G_tb
Precision of our G measurement 1.5
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Relative light yield
Milans group has shown the distribution of
without any correction and corrected for the APD
gain (G_Ham)
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LYs distributions corrected for the APD gain
Correction with G_tb
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Conclusion future

• Conclusion the method allows to estimate the APD
  gain is situ
• Next step analyse the SCAN at 20o to understand
  the gain variation with the temperature