In this thesis, measurements of the inelastic cross-sections of proton-proton collisions at
centre-of-mass energies of \sqrt{s} = 5 TeV and \sqrt{s} = 13 TeV with the LHCb detector are
presented. The cross-section measurements are performed using pp collisions with at least one
prompt long-lived charged particle in the pseudorapidity range 2 2
GeV/c. The extrapolation to the full phase-space is also performed using the official LHCb
simulation generated using the Pythia 8 event generator.
During the second long shut down of the LHC (2018-2019), the LHCb experiment will be upgraded,
and all its subdetectors will be modified. Specifically, the Vertex Detector (VELO) will move from
silicon strips to silicon pixels. The new readout ASIC will be the VeloPix, a successor of the Medipix
family of ASICs. The Single Event Upset robustness of the Medipix3 chip, an ancestor of the
VeloPix, is studied in order to evaluated the radiation hardness of the VeloPix. Different beam tests
at a cyclotron facility were designed and performed with the subsequent data analysis.
Using the Timepix3, a successor of the Medipix3, a telescope was developed. This telescope was
designed to test the sensors and readout electronics prototypes for the VELO upgrade. The design
and the performance of this telescope under very high particle incident rates are also presented