We present a model which describes proton scattering data from ISR to Tevatron energies, and which can be applied to collimation in high energy accelerators, such as the LHC and FCC. Collimators ...remove beam halo particles, so that they do not impinge on vulnerable regions of the machine, such as the superconducting magnets and the experimental areas. In simulating the effect of the collimator jaws it is crucial to model the scattering of protons at small momentum transfer
t
, as these protons can subsequently survive several turns of the ring before being lost. At high energies these soft processes are well described by Pomeron exchange models. We study the behaviour of elastic and single-diffractive dissociation cross sections over a wide range of energy, and show that the model can be used as a global description of the wide variety of high energy elastic and diffractive data presently available. In particular it models low mass diffraction dissociation, where a rich resonance structure is present, and thus predicts the differential and integrated cross sections in the kinematical range appropriate to the LHC. We incorporate the physics of this model into the beam tracking code MERLIN and use it to simulate the resulting loss maps of the beam halo lost in the collimators in the LHC.
In 2018 the world’s first Crab Cavity (CC) experiments with protons were successfully performed, aiming to study the CC effect on a proton beam and evaluate the engineering challenges. Before the ...commencement of these experiments, the impact of the CCs and their multipoles on the long term particle stability of the SPS was studied using dynamic aperture simulations. Furthermore, in order to ensure the long term stability and luminosity performance of the LHC upgrade, the High Luminosity LHC (HL-LHC), the limits of stable motion were also examined in the presence of CC multipole errors, CC voltage errors and additional non-linearities such as the beam–beam effects. This paper presents the comprehensive dynamic aperture results for the SPS and HL-LHC for different CC, accelerator and beam configurations in view of guiding the engineering specifications of the tolerances of the crab cavity multipole errors.
The design stored beam energy in the CERN high-luminosity large hadron collider (HL-LHC) upgrade is about 700 MJ, with about 36 MJ in the beam tails, according to estimates based on scaling ...considerations from measurements at the LHC. Such a large amount of stored energy in the beam tails poses serious challenges on its control and safe disposal. In particular, orbit jitters can cause significant losses on primary collimators, which can lead to accidental beam dumps, magnet quenches, or even permanent damage to collimators and other accelerator elements. Thus, active control of the diffusion speed of halo particles is necessary and the use of hollow electron lenses (HELs) represents the most promising approach to handle overpopulated tails at the HL-LHC. HEL is a very powerful and advanced tool that can be used for controlled depletion of beam tails, thus enhancing the performance of beam halo collimation. For these reasons, HELs have been recently included in the HL-LHC baseline. In this paper, we present detailed beam dynamics calculations performed with the goal of defining HEL specifications and operational scenarios for HL-LHC. The prospects for effective halo control in HL-LHC are presented.
As part of the Large Hadron Collider high luminosity upgrade it is proposed to include crab cavities in the lattice in order to enhance the luminosity. For one proposed cavity design the dynamics of ...the cavity is considered in terms of its impact upon the dynamic aperture of the machine. Taylor maps of the cavity are created and used to perform this analysis with a full assessment of their validity. Furthermore from these Taylor maps, symplectic methods are developed further, guided by the knowledge gained in the study of the physics contained in them.
Abstract
Fixed Field Accelerators are a candidate for future hadron cancer therapy facilities as their high repetition rate and large energy acceptance enables novel treatment modalities such as high ...dose rate FLASH. However, conventional dose delivery mechanisms are still necessary, requiring continuous beam delivery over 1–30s. This work is the first study of slow extraction from a scaling Fixed Field Accelerator, using the LhARA facility for baseline parameters. At a horizontal tune of 10/3, the intrinsic sextupole strength of the nonlinear FFA magnetic field is sufficient to excite the resonance, although extraction is better controlled using an additional excitation sextupole at a tune close to 8/3, with radiofrequency knock-out extraction. Including considerations of issues due to nonlinear fields and limitations required to keep the tune energy-independent, slow extraction from Fixed Field Accelerators is successfully demonstrated.
In this paper we present a new lattice design for a 30–350 MeV scaling fixed-field alternating gradient accelerator for proton therapy and tomography—NORMA (NOrmal-conducting Racetrack Medical ...Accelerator). The energy range allows the realization of proton computed tomography and utilizes normal conducting magnets in both a conventional circular ring option and a novel racetrack configuration, both designed using advanced optimization algorithms we have developed in pyzgoubi. Both configurations consist of ten focusing-defocusing-focusing triplet cells and operate in the second stability region of Hills equation. The ring configuration has a circumference of 60 m, a peak magnetic field seen by the beam of <1.6 T, a maximum horizontal orbit excursion of 44 cm and a dynamic aperture of 68 mm mrad—determined using a novel dynamic aperture (DA) calculation technique. The racetrack alternative is realized by adding magnet-free drift space in between cells at two opposing points in the ring, to facilitate injection and extraction. Our racetrack design has a total magnet-free straight lengths of 4.9 m, a circumference of 71 m, a peak magnetic field seen by the beam of <1.74 T, a maximum horizontal orbit excursion of 50 cm and a DA of 58 mm mrad. A transverse magnet misalignment model is also presented for the ring and racetrack configurations where the DA remains above 40 mm mrad for randomly misaligned error distributions with a standard deviation up to 100 μm.
Abstract
TURBO – Technology for Ultra Rapid Beam Operation – is a novel beam delivery system (BDS) in development at the University of Melbourne. The BDS determines several aspects of treatment ...delivery where a key bottleneck is the deadtime associated with beam energy variation. Beamlines at treatment facilities have a ±1% momentum acceptance range, requiring all the magnetic fields to adjust to deliver different energy beams at multiple depths in the tumour volume. A BDS using Fixed Field Alternating Gradient (FFA) optics could reduce the energy layer switching time (ELST) by enabling the transport of a large range of beam energies within the same fixed fields. We present recent progress and ongoing developments with TURBO, a proof-of-concept demonstrator adapted for low energy protons. Characterisation measurements were performed to determine realistic parameters for beam transport and particle tracking modelling. Simulation and experimental studies are shown for an energy degrader. We mention considerations of canted-cosine-theta magnets and further work to explore the clinical feasibility of a scaled-up BDS for charged particle therapy.
The advent of circular accelerators based on superconducting magnets has revolutionized the field of beam dynamics, with particle motion turning from linear to nonlinear due to unavoidable high-order ...field errors generated by the ring magnets. Nonlinear dynamics was already well mastered, e.g., in the close field of celestial mechanics as similar problems had been considered and successfully tackled. Hence, several results were available to aid comprehension of the behavior of charged particle beams under the influence of nonlinear forces. Here, we discuss how concepts derived from the theory of dynamical systems, linked with the fundamental Kolmogorov–Arnold–Moser theory and Nekhoroshev theorem, can be successfully applied to the analysis of nonlinear motion of charged particles in a circular accelerator. Based on these ideas, an innovative method to measure the extent of the phase-space region within which bounded motion occurs is presented, which has been successfully tested for the first time at the CERN LHC.
Halo diffusion measurements at the CERN Large Hadron Collider (LHC) were conducted with beams for physics at 6.5 TeV by means of collimator scans, carried out between 2016 and 2018. From the time ...evolution of the beam losses recorded during a collimator scan, in which collimator jaws are moved in steps toward the beam core cutting beam tails, one can extract information on the halo diffusion and its population as a function of the transverse amplitude. In this paper, results of the first scans performed at different beam intensities for both planes and both beams using the primary collimators of the betatron-cleaning system are presented. The scans were performed with squeezed optics and colliding beams after a few hours of regular physics production, during so-called end-of-fill measurements. Beam losses are measured with ionization chambers close to the collimators, which enable 1 and 100 Hz acquisitions, as well as diamond beam loss monitors, which enable turn-by-turn and bunch-by-bunch acquisitions. Parametric fits of a diffusion model are applied to the time profile of losses, for both total and individual bunch intensity. The analysis of the measurements performed in various conditions was used to estimate the diffusion coefficient as a function of the transverse amplitude and the population of LHC beam tails.
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