Speaker
Mr
David Dossett
(University of Warwick)
Description
The VELO is the silicon detector surrounding the LHCb interaction point. The sensors have an inner radius of only 7mm from the LHC beam and an outer radius of 42 mm. Consequently the sensors receive a large and non-uniform radiation dose. A dose of $0.5\times10^{13}$ 1 MeV neutron equivalents /cm$^2$ per fb$^{-1}$ of data is predicted at the tip of the sensors. The sensors are fabricated from oxygenated n-on-n silicon with one module made from n-on-p silicon, the only n-on-p module operated at the LHC.
LHCb is a dedicated experiment to study new physics in the decays of beauty and charm hadrons at the Large Hadron Collider (LHC) at CERN. The beauty and charm hadrons are identified through their flight distance in the Vertex Locator (VELO). The VELO is the highest resolution vertex detector at the LHC.
The radiation damage is monitored by three studies: 1) the currents drawn as a function of temperature and voltage 2) studying the noise versus voltage behaviour and 3) charge collection efficiency, studied with tracks from proton-proton collisions, as a function of voltage. The results of all three studies are presented. Clear differences in behaviour, as expected, are observed between n-on-n and n-on-p sensors. Type inversion is observed in the n-in-n sensors. The p-type sensors depletion voltage first reduced and is now increasing. Radiation induced charge loss due to the second metal layer on the sensors is also observed and will be discussed.
for the collaboration
LHCb
Primary author
Prof.
Chris Parkes
(University of Machester)
