Speaker
Mr
Vinicius Franco Lima
(University of Liverpool)
Description
The upgrade of the LHCb experiment, planned for 2019, will transform the experiment to a trigger-less system reading out the full detector at the LHC collision rate and up to $2\times 10^{33}cm^{−2} s^{-1}$ instantaneous luminosity. The Vertex Locator (VELO) is the silicon detector surrounding the interaction region. The upgraded VELO is based on a hybrid pixel system equipped with data driven electronics and designed to withstand a radiation dose up to 370 MRad or $8\times 10^{15} $ 1 MeV n$_{eq}$ $cm^{-2}. The detector will be composed of silicon pixel sensors with 55 × 55 $\mu ^2$ pitch, read out by the VeloPix ASIC which is being developed based on the TimePix/MediPix family. The VeloPix is capable of reading out up to 800 million hits per second. An additional challenge is the non uniform nature of the radiation damage, which results in requiring a guard ring design with excellent high voltage control. In addition, the n-in-p design requires the guard ring to be on the chip side making the high voltage reach the vicinity of the ground plane (about 30 $\mu$m apart). This requires a high voltage tolerant setup for irradiated assemblies which can be achieved using a vacuum chamber. Other solutions were also tried out and will be discussed in this presentation.
The performance of the prototype sensors has been investigated in a test beam in which a dedicated telescope system was created with two arms each equipped with 4 Timepix3 assemblies. The device to be tested can be mounted, rotated, and cooled in the central region, with a optional vacuum setup. This allows several different tests of the performance of the sensor prototypes before and after irradiation.
A collection of preliminary results will be presented, as well as a comparison of the performance of the different sensor prototypes produced by Micron semiconductors and Hamamatsu photonics. The evaluation programme of the prototypes also includes studies to show the effects of radiation damage. The sensors were irradiated at several facilities, including: JSI reactor neutrons in Ljubliana, mid energy (23 MeV) protons at KIT in Karlsruhe and high energy (24 GeV) protons from IRRAD at CERN.
Primary author
Prof.
Kazuyoshi Akiba
(IF-UFRJ)
