12
2.3.
The
radiation
environment
of
plastic
scintillators in the Tile Calorimeter of the ATLAS
detector
Prior to Run 1
of LHC data taking, several studies were conducted in order to
estimate the impact of the predicted radiation environment on the performance of
the detector. GCALOR [11] and FLUKA [12] simulations
predicted that the
radiation levels in the Gap region would be greater than those in the barrel
regions, with the MBTS scintillators being exposed to the most radiation. The
predicted radiation map of the total ionising dose accumulated over a
year in the
calorimeter region at
√𝑠 = 14 TeV
and nominal luminosity of 10
34
cm
-2
s
-1
is
shown in Figure 2-7 [13]. The dose is calculated in units of Gray (Gy), which is
defined as 1 Joule of radiation energy absorbed per 1 kilogram of matter.
Figure 2-7: Radiation map of the total ionising dose accumulated over a year in the
calorimeter region at √s=14 TeV and nominal luminosity of 10
34
cm
-2
s
-1
13
The position of the MBTS scintillators
is outlined in white, whilst the cryostat
and gap scintillators are positioned
at larger radial values, R, along the Gap
region. For the scintillators
in the Tile Barrels, it was predicted that the worst
light losses after 10 years of LHC operation would be approximately 5% in the
region closest to the beam pipe [13].
After Run 1, with
√𝑠
reaching a maximum of 7 TeV, the estimated dose that the
MBTS scintillators received was between
0.1~0.4 × 10
4
Gy
[14]. At a dose in the
range of
10
4
Gy
, a loss of 50% in light transmission of the scintillator plus fiber
system was anticipated [14]. A small fraction of
yellow discolouration was
observed in these scintillators
