Abstract
This thesis reports the implementation of the Medipix detector-based neutron radiation measurement system at the Compact Muon Solenoid experiment on the Large Hadron Collider at CERN. This work encompasses simulations to study particle tracking capabilities of the Medipix3RX device as well as energy and angular spectra of the radiation field in the cavern. The thesis describes the design, calibration and the commissioning of the detector modules as well as its data analysis algorithms. It concludes with data taking and comparison of the recorded fluxes with those obtained from simulation studies.
Medipix3RX is the latest of the hybrid pixelated detectors initially developed for medical imaging applications. These detectors could be used to evaluate the spectral composition of a mixed field in the CMS cavern. The direct flux and dose measurements carried in the cavern would help estimate the performance and lifetimes of detector systems at CMS.
To begin with, energy and angular distributions of the neutrons in the mixed field radiation present in the cavern were analysed. The Medipix detectors were modelled using Monte-Carlo tools which enable the study of response and performance through simulations. Special conversion layers were investigated and optimised to improve detector efficiencies for slow and fast neutrons. The locations of seven Medipix detector modules, in the experimental cavern, were cabled for the installation of said modules and their back-end readout electronics in the service cavern. Post-processing algorithms were developed for track reconstruction and recognition using cluster analysis techniques, which determines the count of clusters formed by incident particles and consequently estimates the particle fluxes in the cavern.
Four CMS-MPX detectors were installed in the cavern for data taking and are in continuous operation since March 2018. The measured fluxes from the installed detectors were compared to the luminosity from the LHC and were seen to be in good agreement.
Plans are on to upgrade the CMS-MPX network to Timepix3 detectors during the next CMS upgrade which will enable neutron spectroscopy in the CMS cavern and deliver luminosity results to the LHC.