This thesis describes the wide subject of the luminosity leveling and its requirements for the LHC and the HL-LHC. We discuss the advantages and disadvantages of different leveling methods focusing the thesis on the beta star leveling technique. We review the beams offset build--up due to the environmental (i.e. natural ground motion) and mechanical (i.e. moving quadrupole) sources. We quantify the instrumentation requirements for the reliable and reproducible operation with small offsets at the interaction points. Last but not least, we propose a novel method for the beam offset stabilization at the collision point based on the feedback from the luminosity.

Luminosity control and beam orbit stability with beta star leveling at LHC and HL-LHC

A new generation of the Beam Wire Scanner (BWS) instrument is being developed for the Large Hadron Collider (LHC) and its injector chain at the European Organization for Nuclear Research (CERN). This is an electro-mechanical system based on a Permanent Magnet Synchronous Motor (PMSM), a robust resolver and a high precision optical encoder. This system is located in underground installations and has to withstand large irradiation levels provoked by particle beams. The control electronics is situated away from it to avoid the destructive impact of ionizing particles, introducing long distances of up to 250m for powering and measuring the system. Challenges arise when imposing large acceleration to obtain a scanning speed of the wire of no less than 20ms−1 and above, with a target position accuracy of 5µm rms. This paper details the methodology of the system and control design, which includes performance evaluation benchmark at different design stages and the target electronics development. Finally, the first field results performed inside the Super Proton Synchrotron (SPS) accelerator machine are presented.

Design and validation methodology of the control system for a particle beam size measurement instrument at the CERN laboratory

Le LHC met en collision deux faisceaux de protons avec une energie de 7 Tevchacun, entrainant ainsi un taux de particules d'environ 109 Hz. Le taux departicules est determine la production d'une coupe transversale, une constancenaturelle, la luminosite et un parametre dependant de l'accelerateurcapable de decrire les faisceaux de particules. La luminosite depend dunombre de particules dans chaque faisceau lineairement et des dimensionstransversales du faisceau inversement. Elle augmente avec la densite dufaisceau de particules et en consequence, la probabilite d'interactions estaccrue. Pour optimiser les tailles des faisceaux transversaux, on utilisedes dispositifs de contrle de pro_le, qui permettent de mesurer les changementsde parametres dependants. A l'interieur du LHC, trois di_erentstypes de dispositifs de contrle des pro_les sont installes, savoir le WireScanner (WS), le Synchroton Light Monitor et le Rest Gas Pro_le Monitor.Le WS est considere comme etant le plus precis de ces trois dispositifsde contrle et sert d'appareil de calibrage pour les deux autres. Ils'agit d'un appareil electromecanique qui mesure l'etat de densite du faisceautransversale de faon intermittente. Lorsque le cble traverse le faisceau,l'interaction particule-matiere genere une cascade de particules secondaires.Ces derniers sont interceptes par un scintillateur, lequel est attache un photo-multiplieur, et ce a_n de mesurer l'intensite de la lumiereainsi produite. L'amplitude du signal lumineux est proportionnelle la densite de la portion de faisceau interceptee. L'acquisition de la position du_l et celle de l'intensite du signal sont synchronisees avec la frequence dela revolution de particules puis sont combinees pour construire le pro_lede densite du faisceau transversal. Le WS est installe et mis en marchedans tous les accelerateurs circulaires du CERN sur une base reguliere

Design and construction of a new actuator for the LHC wire scanner

Performance Assessment of Pre-Series Fast Beam Wire Scanner Prototypes for the Upgrade of the CERN LHC Injector Complex

Particle accelerators have a singular environment where multiple constraints are driving the engineering of equipment. Designers have to deal with the destructive effects of charged particles, high vacuum requirements, large temperatures and particular system architectures due to large-scale installations such as the Large Hadron Collider (LHC) at the CERN laboratory. At the same time, there is a continuous challenge to produce, measure and control smaller particle beams to increase the discovery potentials of large physics experiments. In this context, an innovative actuator has been built to measure precisely the size of beams down to 150$\mu$m sigma, by moving a thin carbon wire of 3$ 0\mu$m at about 20m·$\mathrm{s}^{-1}$ through particle beams. Called Beam Wire Scanner (BWS), this system uses direct drive coupling to actuate a shaft inside a vacuum vessel without moving parts outside it. We are reporting on the design and validation of its control system based on torque control feedback as the only on-line closed-loop system to operate this instrument. The proposed strategy keeps the smoothest action as possible on the system avoiding speed and position corrections that would lead to undesired torque variations, increasing the uncertainty of the carbon wire position.

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A low fluctuation control strategy for PMSM direct drive system targeting Particle Beam Instrumentation Application

The Beam Instrumentation group of the European Organization for Nuclear Research (CERN) has been developing an instrument called the Beam Wire Scanner (BWS) for the past few years. This system is used to measure the size of proton beams in the Large Hadron Collider (LHC) and its injector chain. An electro-mechanical system moves a very thin wire of 30 μm through the particle beam and measures the induced radiation losses generated by this interaction. The actuator, based on a Permanent Magnet Synchronous Motor (PMSM), a solid rotor resolver and an in-house designed high precision optical encoder are located in underground installations and have to cope with large irradiation levels. Another difference with respect to its predecessors is the placement of all moving parts in the vacuum. The control electronics is situated far away from the beam tunnels to minimize the destructive impact of ionizing particles. Challenges arise from the long distance between these two parts, up to 250 meters, and the high scanning speed of the wire of up to 20 ms1, with a target position accuracy as low as 5 μm rms. This paper describes the challenges of the BWS design, details the current status and introduces the philosophy of its conception to the IEEE control application community.

A fast and accurate wire scanner instrument for the CERN accelerators to cope with severe environmental constraints and an increased demand for availability

B. Schneider

Papers

A fast and accurate wire scanner instrument for the CERN accelerators to cope with severe environmental constraints and an increased demand for availability