Etude et impact du bruit de fond corrélé pour la mesure de l'angle ...

3.4 The calibration system 59
tel-00821629, version 1 - 11 May 2013
Figure 3.14: FADC baseline mean position (left) and RMS (right) as function
of the PMT number. ID PMT are identified by PMT number smaller
that 390 while IV PMT by number bigger than 390. This monitoring unit allows
to identify abnormal channels through the position and the fluctuation
of the FADC baseline.
3.4.1 Light Injection
LED fibers system is used to inject light of known waveform into the ID an
the IV. The fibers are routed inside the detector on the edge of some PMTs.
Some injection points are equipped with di↵user plates to illuminate widely
the detector. The fibers are connected to a blue and UV LEDs flasher which
rate and light intensity is controlled remotely. The light injection system
is used daily to monitor the stability of the PMT gain and their timing
response.
3.4.2 Radioactive Sources
Gamma sources 137 Cs (0.667 MeV), 68 Ge (2⇥0.511 MeV), 60 Co (1.173 and
1.333 MeV) and neutron source 252 Cf, whose rates is at the level of 50 Hz,
have been deployed into the target and the gamma catcher.
Deployment in the target is performed along the symmetry axis using a
motorised pulley-and-weight system, operated from a glove-box installed
above the chimney. The deployment range span from 1 cm above the target
bottom up to the target chimney, with 1 mm precision on the source position.
Deployment in the gamma catcher is performed using a motor driven wire,
guided through a rigid looped tube. The guide tube traverses the gamma
catcher passing near the boundaries of the target and the bu↵er. The source
position is known within 1 cm precision along the loop and the perpendicular
distance between the source and the target wall is known within 2 mm.