Beam secondary shower acquisition design for the CERN high accuracy wire scanner

The LHC injectors upgrade (LIU) project aims to boost the LHC luminosity by doubling the beam brightness with the construction of the new LINAC4, the first linear accelerator on the LHC chain. The brighter beams require upgrades on the full injector chain to deliver low emittance beams for the future High-Luminosity LHC (H-LHC). Thus, new and more precise beam instrumentation is under development to operate on this new scenario. These upgrades include the development of a new beam wire scanners generation (LIU-BWS), interceptive beam profile monitors used for the beam emittance calculation. Wire scanners determine the transverse beam profile by crossing with a carbon wire (30 um) through the particle beam. The beam profile is inferred from the intensity of the shower of secondary particles, scattered from beam-wire interaction, and the wire position. The current BWS generation features high operational complexity and its performance is in part limited by their secondary shower detectors and acquisition systems. They are traditionally based on scintillators attached to a Photo-Multiplier tube (PMT) through optical filters. These detectors require tuning according to the beam energy and intensity prior to a measurement to not saturate the readout electronics, located on the surface buildings. Under these circumstances, many configurations lead to a poor SNR and very reduced resolution, directly affecting the measurement reliability. In addition, bunch-by-bunch profile measurements are degraded by the use of long coaxial lines, which reduce the system bandwidth leading to bunch pile-up. This thesis covers the design of an upgraded secondary shower acquisition system for the LIU-BWS. This includes the study of a novel detector technology for BWS, based on polycrystalline Chemical Vapour Deposited (pCVD) diamond, and the implementation of two acquisition system prototypes. This work reviews operational acquisition systems to identify their limitations and shows advanced particle physics simulations with FLUKA for better understanding of the secondary particles shower behaviour around the beam pipe. Simulations, along with a study of the different beams in each machine, leaded to the estimation of the required dynamics per accelerator, and an optimised placement of the upgraded detectors. To cope with the injectors working points, the acquisition systems implemented performed high dynamic range signal acquisition and digitisation in the tunnel with a radiation-hard front-end nearby the detector, digital data is afterwards transmitted to the counting room through a 4.8Gbps optical link. This novel schema not only allowed low-noise measurements, but also avoided the bandwidth restrictions imposed by long coaxial lines, and greatly simplified the scanner operation. The upgraded design investigates two approaches to cover a dynamic of about 6 orders of magnitude: a single-channel system with logarithmic encoding, and a multi-channel system with different gains per channel. Prototypes of both schemas were fully developed, characterised on laboratory and successfully tested on SPS and PSB under different operating conditions. The evaluation of the acquisition systems during beam tests allowed the study of the LIU-BWS mechanical performance and comparative the measurements with operational systems. pCVD diamond detectors, with a typical active area of 1cm2 were systematically evaluated as BWS detectors. This document analyses the results from several measurement campaigns on SPS over its energy and intensity boundaries (5e9 - 1.1e11 protons per bunch and 26 - 450 GeV). The SPS results suggest a potential application on LHC beam wire scanners.