L. Arruda, J. Casaus, C. Díaz, J. Marín, C. Palomares. Preflight PMT calibration: functionality tests. CIN105. spe =(67.5+/-0.3)% syst=(0.94+/-0.03)%. Z measurement error contributions. statistical: systematics from non-uniformities: radiator: n, thickness, clarity, ...
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syst=(0.94+/-0.03)%Z measurement error contributions
with <Sk> ~ 92.9 A/lum
From Hamamatsu datasheet:
systematic effect detected signal (npe)
ssyst~/npe~ Dmax/sqrt(20) = 6%/sqrt(20) ~ 1.5%
In order to reach the Z accurate measurement (sytematics <1%), precise knowledge (<6% level) of single Unit Cell photo-detection efficiency and gains are required
The intrinsic spread in PMT gains and QE (even more when additional elements are considered, i.e. LG, glue...) imply the need of a well defined calibration and monitoring strategy at different stages of the RICH assemblyZ measurement requirements
The system has been validated on a row with 8 PMTs (R7600-M16-00) coupled to light guides used in the vibration and thermal tests in July 2005
Hamamatsu data available only for 6 out of 8 PMTs show a wide range to try and find a linear correlation with the measurements
HV at 800VPreliminary functionality tests
POS. Gx5 (@800V) Cath. Sens. Cath. Blue Sens.
1 49.0 105.0 11.5
2 91.3 ---- ----
3 59.6 75.1 9.13
4 103.5 ---- ----
5 43.5 92.7 10.9
6 43.6 82.6 9.43
7 152.4 109.0 10.5
8 133.2 87.1 9.53
Final flight electronics for the acquisition
Blue pulsed LED (430 nm) operating at 3.48 V with filters to attenuate the light (3 blue filters to attenuate the light)
The whole setup is placed inside a black box (1140 X 890 X 720 mm, wall thickness 20 mm) with a top door and lateral door that allows an easier access to the devices.
Efficiency variation: eQ, optical contacts
PMT id 7
First, in order to confirm the black box light isolation and the stability of the electronics pedestals runs with 50000 events were regularly acquired .Pedestals analysis
For the pedestal fit:
Geff= a G(m,s1) + (1 - a) G(m,s2)
s2eff= as21+(1 - a)s22
Differences to the first measurement
Dark current is estimated as the fraction of events beyond 4 sigma of the second Gaussian
Fit failure !!!
To study the stability of the LED, two consecutive spe runs of 60000 events were acquired in the same conditions.
A bi-parametric model of the photomultiplier response was applyed wich allows to extract: gain, sigma gain, average npe
Relative variations of gains and <npe>
The LED is stable for gains within 3% and for <npe> within 4%
Pixels with a gain variation within (2-3)%
Pixels <npe> with a variation <5%
Relative radiant intensity