Speaker
Description
Summary
Plans are being formulated at CERN for a luminosity upgrade to the Large Hadron
Collider (LHC) machine. The LHC upgrade (SLHC) is being designed to increase the
luminosity from 1034cm-2s-1 to 1035cm-2s-1. The expected time-scale would be around
year 2015. The fluences at the SLHC will be 10 times higher than at LHC. For radii
greater than 20 cm the expected fluence is 1015 hadrons/cm2. It is not clear, if the
current opto-electronic components of the inner detector readout system are able to
cope with this challenging radiation environment of SLHC.
Previous radiation tests have shown that the opto-electronic components (VCSEL
lasers, PIN diodes and optical fibres) can survive 10 years of LHC operation.
Radiation tests by the ATLAS Pixel detector group have demonstrated that these
components can survive fluences and doses up to a factor of two higher than the SCT
values.
Therefore there is an open question of whether this type of opto-electronics could
be used on the upgraded SCT detector at the SLHC. This is a critical question for
the design of this detector as it will have a major influence on the layout of all
the readout services and therefore needs to be answered before the detector design
can advance very far.
We are presenting the results of irradiation tests of Truelight VCSEL lasers,
Centronic PIN-diodes, and SIMM fibres up to SLHC fluences.
Our previous radiation tests have shown that VCSELs and PIN diodes suffer from bulk
damage but are insensitive to surface charge effects. These tests have also
demonstrated good agreement with the NIEL scaling hypothesis. Hence, the first
irradiation tests for SLHC we plan to be perform at the Ljubljana neutron reactor
using NIEL scaling as a first step. We intend to confirm these results with other
beams in the future.
For the irradiation studies of VCSEL lasers we are planning to have several cycles
of irradiation and annealing as we had demonstrated that nearly full recovery of the
VCSEL performance can be achieved with injection annealing (i.e. running the VCSELs
with a DC current of 10 to 20 mA).
The radiation damage mechanism in fibre is due to creation of “colour centres” in
the electronic levels of the molecules. This is then only sensitive to ionising
dose, so can be most conveniently studied with a gamma source. We need a high dose
rate gamma source and a large area source to give a uniform dose over the sample. A
suitable facility is the INER in Taiwan, which we will use to irradiated the fibres
up to 100 Mrad. We will determine the induced attenuation of the fibres during
irradiation.
We are presenting in this paper the results of the irradiation tests of the VCSEL
lasers, PIN diodes and fibres up to SLHC doses and show the performance degradation
of these devices as function of radiation dose.
In the future we intend also to determine SEU cross section of the GOL driver
chip and QPLL chip while operating them at 1.6 GBits/sec.
