Design and Performance Evaluation of Nonlinear Collimation Systems for CLIC and LHC

The beam collimation systems are an essential part of the high energy colliders. A collimation system should remove beam halo to reduce detector background and ensure the machine protection, thus minimizing the activation and damage of sensitive accelerator components. The mechanical and optics design of collimation systems is not simple, and they should fullfil some often conflicting constraints and requirements: high cleaning efficiency, high mechanical robustness, and low wakefields (impedances). The conventional collimation systems are generally based on linear optics. Nevertheless, several alternative advanced concepts on collimation have been proposed in the literature. In this thesis report we have studied in detail nonlinear collimation systems. These are based on a general scheme with a skew sextupole pair, which can be adapted to both linear and circular colliders. In particular we have designed a nonlinear collimation system for the Compact Linear Collider (CLIC). This system fullfils the function of machine protection against mis-steered or errant beams with energy offset higher than 1.5 % of the nonimal energy 1.5 TeV. The performance of this collimation system has been evaluated by means of tracking studies, and compared with that of the conventional baseline linear collimation system. Since the collimation requirements for linear colliders designed to operate at center-of-mass energy around TeV are similar to tho se for the Large Hadron Collider (LHC) at collision beam energy 7 TeV, it is thus close thought to apply a similar LHC nonlinear collimation scheme as that designed for CLIC. We have explored this possibility, and have proposed an alternative nonlinear system for the Phase-II betatron cleaning in the LHC. Its performance and cleaning efficiency have further been evaluated by tracking studies. Moreover a comparison of the features of the nonlinear collimation system and the linear collimation system has been made for the LHC

A hydrodynamic model for particle beam-driven plasmon wakefield in carbon nanotubes

Charged particles moving through a carbon nanotube may be used to excite electromagnetic modes in the electron gas produced by π and σ orbitals in the cylindrical graphene shell that makes up a nanotube wall [1]. This effect has recently been proposed as a potential novel method of short-wavelength-high-gradient particle acceleration [2, 3]. In this contribution, first we review the existing theory based on a linearised hydrodynamic model for a non-relativistic, localised point-charge propagating in a single wall nanotube (SWNT) [4]. Then we extend it to the relativistic case. In this hydrodynamic model the electron gas is treated as a plasma with additional contributions to the fluid momentum equation from specific solid- state properties of the gas. The governing set of differential equations is formed by the continuity and momentum equations for the involved species: beam charges, electrons and ions of the lattice. These equations are then coupled by Maxwell’s equations. The ions are assumed to be quasistatic and provide a neutralising background. To solve the differential equation system a modified Fourier-Bessel transform has been applied. Furthermore, a spectral analysis has been realised to determine the plasma modes able to excite a longitudinal electrical wakefield component in the SWNT to accelerate test charges. Eventually, we discuss the suitability and possible limitations of the method proposed in this study for particle acceleration

Excitation of wakefields in carbon nanotubes: a hydrodynamic model approach

The interactions of charged particles with carbon nanotubes may excite electromagnetic modes in the electron gas produced in the cylindrical graphene shell constituting the nanotube wall. This wake effect has recently been proposed as a potential novel method of short-wavelength high-gradient particle acceleration. In this work, the excitation of these wakefields is studied by means of the linearized hydrodynamic model. In this model, the electronic excitations on the nanotube surface are described treating the electron gas as a 2D plasma with additional contributions to the fluid momentum equation from specific solid-state properties of the gas. General expressions are derived for the excited longitudinal and transverse wakefields. Numerical results are obtained for a charged particle moving within a carbon nanotube, paraxially to its axis, showing how the wakefield is affected by parameters such as the particle velocity and its radial position, the nanotube radius, and a friction factor, which can be used as a phenomenological parameter to describe effects from the ionic lattice. Assuming a particle driver propagating on axis at a given velocity, optimal parameters were obtained to maximize the longitudinal wakefield amplitude.<br/

Recent Improvements of PLACET

PLACET[1] is a program used to simulate the dynamics, including wakefields, of a beam in the main accelerating or decelerating part of a linac. It allows for the investigation of single- and multi-bunch effects, the simulation of normal RF cavities with relatively low group velocities, as well as transfer structures specific to CLIC. Recent improvements, including the possibility to simulate bunch compressors, ground motion, and the use of parallel computer systems, are presented in this paper

An alternative nonlinear collimation system for the LHC

The optics design of an alternative nonlinear collimation system for the LHC is presented. We discuss an optics scheme based on a single spoiler located in between a pair of skew sextupoles for betatron collimation. The nonlinear system allows opening up the collimator gaps, thereby, reduces the collimator impedance, which presently limits the LHC intensity. After placing secondary collimators at locations behind the spoiler, we analyze the beam losses and calculate the cleaning efficiency from tracking studies. The results are compared with those of the conventional linear collimation system

Understanding the impact of hamstring injuries on match performance in Spanish professional soccer players: two full seasons follow-up

This study aimed to analyze the changes in match physical demands in professional soccer players after sustaining a hamstring injury, which was categorized based on injury severity. Seventy-two hamstring injuries involving sixty-four professional soccer players from the Spanish LaLiga™ were considered for this study. All injuries were classified according to their severity as moderate (resulting in eight to 28 missed days) and major (resulting in more than 28 missed days). Mediacoach video-tracking system collected time and external load variables and subsequently compared them between the pre-injury and return-to-play periods. The analyzed variables included distance covered at different velocities (i.e., total distance, at 18-21 km.h−1, at 21-24 km.h−1, and at more than 24 km.h-1), the number of sprints, accelerations, decelerations, and high metabolic load distance (HMLD). The results showed that players with both moderate and major injuries played fewer minutes after injury (p<.001 to p<.05) and experienced a decrease in maximum speed (p<.01 to p<.05), covering less total distance (p<.05) and exhibiting a decrease (p<.05) in average speed (only observed in players with major injuries). Additionally, moderately injured players experienced a reduction in the number of maximum accelerations (p<.05) and decelerations (p<.05), high metabolic load distance/min (p<.05), and average accelerations (p<.05). Furthermore, a significant reduction in the magnitude of maximum decelerations was observed in players with major injuries (p<.05). These findings highlight the importance of implementing strategies that enable the attainment of initial levels of high-intensity actions and maximum speed in reconditioning programs following hamstring injuries

Oral Serum-Derived Bovine Immunoglobulin/Protein Isolate Has Immunomodulatory Effects on the Colon of Mice that Spontaneously Develop Colitis

Dietary immunoglobulin concentrates prepared from animal plasma can modulate the immune response of gut-associated lymphoid tissue (GALT). Previous studies have revealed that supplementation with serum-derived bovine immunoglobulin/protein isolate (SBI) ameliorates colonic barrier alterations in the mdr1a-/- genetic mouse model of IBD. Here, we examine the effects of SBI on mucosal inflammation in mdr1a-/- mice that spontaneously develop colitis. Wild type (WT) mice and mice lacking the mdr1a gene (KO) were fed diets supplemented with either SBI (2% w/w) or milk proteins (Control diet), from day 21 (weaning) until day 56. Leucocytes in mesenteric lymph nodes (MLN) and in lamina propria were determined, as was mucosal cytokine production. Neutrophil recruitment and activation in MLN and lamina propria of KO mice were increased, but were significantly reduced in both by SBI supplementation (p < 0.05). The increased neutrophil recruitment and activation observed in KO mice correlated with increased colon oxidative stress (p < 0.05) and SBI supplementation reduced this variable (p < 0.05). The Tact/Treg lymphocyte ratios in MLN and lamina propria were also increased in KO animals, but SBI prevented these changes (both p < 0.05). In the colon of KO mice, there was an increased production of mucosal proinflammatory cytokines such as IL-2 (2-fold), IL-6 (26-fold) and IL-17 (19-fold), and of chemokines MIP-1β (4.5-fold) and MCP-1 (7.2-fold). These effects were significantly prevented by SBI (p < 0.05). SBI also significantly increased TGF-β secretion in the colon mucosa, suggesting a role of this anti-inflammatory cytokine in the modulation of GALT and the reduction of the severity of the inflammatory response during the onset of colitis

Future Particle Accelerators

Particle accelerators have enabled forefront research in high energy physics and other research areas for more than half a century. Accelerators have directly contributed to 26 Nobel Prizes in Physics since 1939 as well as another 20 Nobel Prizes in Chemistry, Medicine and Physics with X-rays. Although high energy physics has been the main driving force for the development of the particle accelerators, accelerator facilities have continually been expanding applications in many areas of research and technology. For instance, active areas of accelerator applications include radiotherapy to treat cancer, production of short-lived medical isotopes, synchrotron light sources, free-electron lasers, beam lithography for microcircuits, thin-film technology and radiation processing of food. Currently, the largest and most powerful accelerator is the Large Hadron Collider (LHC) at CERN, which accelerates protons to multi-TeV energies in a 27 km high-vacuum ring. To go beyond the maximum capabilities of the LHC, the next generation of circular and linear particle colliders under consideration, based on radiofrequency acceleration, will require multi-billion investment, kilometric infrastructure and massive power consumption. These factors pose serious challenges in an increasingly resource-limited world. Therefore, it is important to look for alternative and sustainable acceleration techniques. This chapter pays special attention to novel accelerator techniques to overcome present acceleration limitations towards more compact and cost-effective long-term future accelerators

Update on Nonlinear Collimation Schemes for the LHC

In this paper we review the status of the studies on nonlinear collimation schemes for the LHC. Concretely we describe the design of a nonlinear optics for betatron cleaning in IR7. The aim is to investigate alternative nonlinear collimation systems to reduce the collimator-induced impedance that may limit the beam intensity towards the LHC luminosity upgrade. The performance of the LHC nonlinear collimation system is studied by means of tracking simulations and compared with the present LHC system. Furthermore, the advantages and possible limitations of such nonlinear collimation scheme are discussed

Studies on Nonlinear Post-linac Protection for CLIC

The post-linac energy collimation system of CLIC is designed to fulfill an essential function of protection of the Beam Delivery System (BDS) against miss-steered beams generated by failure modes in the main linac. Guaranteeing the collimator survivability in case of direct beam impact is very challenging, if we take into account the need to deal with an unprecedented transverse beam energy density per beam of the order of GJ/mm². This translates into a high damage potential of uncontrolled beams. In this paper we present an alternative nonlinear energy collimation system as a potential solution to guarantee the survival of the collimators. The performance and error tolerances of this system are studied by means of beam tracking simulations, and compared with those of the conventional baseline CLIC energy collimation system