Centre de l'accélérateur linéaire de Stanford

Résumé

Le Laboratoire national de l'accélérateur SLAC (SLAC National Accelerator Laboratory, précedemment Centre de l'accélérateur linéaire de Stanford) est un laboratoire de physique dépendant du Département de l'Énergie des États-Unis et géré par l'Université Stanford. Ses activités de recherche se concentrent sur la physique des particules théorique et expérimentale, et depuis quelques années s'ouvrent à la photonique au travers du projet LCLS. L'accélérateur de particules de 3,2 km de long situé sur le site est le plus long accélérateur linéaire au monde. Historique et découvertes Fondé en 1962 en tant que Centre de l'accélérateur linéaire de Stanford (SLAC) est situé sur un terrain appartenant à l'université Stanford en Californie d'une surface de 1,72 kilomètre carré et situé à l'ouest du campus principal. L'accélérateur principal (LINAC), d'une longueur de 2 miles (3.2 kilomètres, le plus grand accélérateur linéaire du monde) est capable d'accélérer des électrons et des p

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https://fr.wikipedia.org/wiki/Centre_de_l'acc%C3%A9l%C3%A9rateur_lin%C3%A9aire_de_Stanford

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Hadron beams - approximately 200 MeV protons and 400 MeV/u fully stripped carbon ions - are better suited to treat deep-seated tumours than X ray beams - produced by electrons accelerated by linear accelerators (linacs) to 5-25 MeV - because they leave the maximum energy density at the end of their range in matter, in the so-called Bragg peak. This physical property allows dose depositions that are more conformal to the tumour target and spare much better the surrounding healthy tissues, so that hadron therapy treatment rooms could substitute X ray therapy rooms (about 20 000 worldwide) if the needed accelerators could be made of similar dimensions and costs. Cyclotrons and synchrotrons are at the heart of today proton and carbon ion therapy centres, respectively. At the end of 2015, more than 130 000 patients have been treated with proton beams and almost 20 000 with carbon ions [Particle Therapy Co-Operative Group data, \url{https://www.ptcog.ch/index.php/patient-statistics}]. High frequency hadron therapy linacs have been studied in the last 30 years. Their main advantage is represented by their active beam energy modulation, which permits quick treatments with superior beam quality and novel dose delivery techniques. This thesis is the last of many research works on the development of linear accelerators for hadron therapy. The preliminary design of two linear accelerator facilities, for proton therapy (TULIP) and carbon ion therapy (CABOTO), was completed. The introductory Chapter will review the rationale of hadron therapy as a treatment methodology, together with a discussion of the advantages of linacs in hadron therapy compared to state-of-art technologies. Finally, the most important past research activities based on which this thesis started will be presented. The second Chapter describes the RF design of accelerating structures performed for the proton and carbon ion therapy facilities later on presented. The third Chapter is dedicated to the proton linac design, called TULIP: TUrning LInac for Protontherapy. The forth Chapter describes the carbon ion linac design, called CABOTO: CArbon BOoster for Therapy in Oncology. The fifth Chapter presents the experimental activity performed on the backward travelling wave prototype built. Goal of the test is to study the high-gradient break-down limitation of S-Band cavities. The thesis is completed by an Appendix where the beam dynamics codes developed to design the linacs are discussed.

EPFL2018

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In this paper we describe the technical design of an ongoing proof-of-principle echo-enabled harmonic generation (EEHG) experiment at the Next Linear Collider Test Accelerator (NLCTA) at SLAC.We present the design considerations and the technical details of the experiment.

2010

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The ring cyclotron of the Paul Scherrer Institute (PSI) accelerates an intense proton beam from 72MeV up to 590MeV. This happens in four cavities of very high quality factor, oscillating in the fundamental mode. The beam can excite parasitic oscillation modes (HOMs), because of its time structure. Measurements showed that their field can leak out into the vacuum chamber. Until now, there is no tool available to predict the potentially harmful effect of these HOMs onto the beam operation of the cyclotron. It is foreseeable that these effects might play a role if even higher beam currents have to be accelerated. This dissertation therefore deals with the numerical analysis and measurement of beam-cavity interactions. First calculations for a single cavity, interacting with a proton bunch were performed with MAFIA's eigenmode- (E3), time domain- (T3) and particle-in-cell (TS3) solvers. However, the structured grid and the limited computing performance of MAFIA make realistic simulations impossible. A simplified computation method is developed in this dissertation since a self-consistent simulation is impossible on today's computers: The parallel eigensolver Omega3P of the Stanford Linear Accelerator Center (SLAC) allowed us to calculate eigenmodes of the entire ring cyclotron for the first time ever. The rf fields are expanded onto a superposition of these modes and the excitation is calculated in frequency domain. Trajectories of the particles in the static magnetic field, superposed with the space charge fields and the beam excited HOMs, are then simulated. However, the quantitative accuracy of this model is still limited. On the one hand, because of the simplification in the geometry of the simulated rf structure, which otherwise would lead to a problem size going beyond the available computing resources. On the other hand, because it is not yet possible to simulate strongly absorbing boundaries more accurately. The simulation results confirm that up to proton beam currents of 2mA, corresponding to the routinely accelerated beam intensities, only a small deformation of the charge distribution appears. This thesis leads to a new simulation tool for further studies of intensity increases in high power cyclotrons.

EPFL2004

Chargement

EPFL2018

EPFL2004