Philip Burrows

Abstract:

The luminosity of a particle collider is an extremely crucial performance parameter describing its capability of producing interactions in the collision point. However, imperfections in a collider can lead to luminosity loss. Among different imperfections, an important one is stray magnetic fields. For the Compact Linear Collider (CLIC), a collider being considered as one of the main options in Europe after the Large Hadron Collider, simulations showed an unprecedented sensitivity of the machine to fields on the order of 0.1 nT. Hence, such tight constraints require special design considerations to prevent performance loss. Different shielding techniques are available in the literature, typically relying on an active shielding strategy and capable of reducing the magnetic field amplitudes down to the nano-Tesla level. However, measuring fields with such amplitudes is challenging by using state-of-the-art commercially available sensors and therefore, a passive shielding strategy, consisting in enveloping sections of the beamline with a magnetic shield, is a more attractive option. For CLIC, Mumetal®, a Ni–Fe alloy with advertised relative permeability above 100,000, was chosen. In this paper, the DC and AC magnetic characterization of two samples of Mumetal®, one annealed in its final form and the other one non-annealed is presented, showcasing how the annealing results in a boost of the magnetic permeability of more than order of magnitude. As a case study, the shielding performance of a 1-mm thin layer of Mumetal® enveloping CLIC’s beamline is estimated.

Abstract:

Plasma Physics and Controlled Fusion PAPER Proton beam defocusing in AWAKE: comparison of simulations and measurements A A Gorn1,2, M Turner3, E Adli4, R Agnello5, M Aladi6, Y Andrebe5, O Apsimon7,8, R Apsimon7,8, A-M Bachmann3,9,10, M A Baistrukov1,2Show full author list Published 6 November 2020 • © 2020 IOP Publishing Ltd Plasma Physics and Controlled Fusion, Volume 62, Number 12 Citation A A Gorn et al 2020 Plasma Phys. Control. Fusion 62 125023 80 Total downloads Turn on MathJax Get permission to re-use this article Share this article Share this content via email Share on Facebook Share on Twitter Share on Google+ Share on Mendeley Article information Abstract In 2017, AWAKE demonstrated the seeded self-modulation (SSM) of a 400 GeV proton beam from the Super Proton Synchrotron at CERN. The angular distribution of the protons deflected due to SSM is a quantitative measure of the process, which agrees with simulations by the two-dimensional (axisymmetric) particle-in-cell code LCODE to about 5%. The agreement is achieved in beam population scans at two selected plasma densities and in the scan of longitudinal plasma density gradient. The agreement is reached only in the case of a wide enough simulation box (several plasma wavelengths) that is closer to experimental conditions, but requires more computational power. Therefore, particle-in-cell codes can be used to interpret the SSM physics underlying the experimental data.

Abstract:

The Compact Linear Collider is one of the two main European options for a collider in a post Large Hadron Collider era. This is a linear e+e-collider with three center-of-mass energy stages: 380 GeV, 1.5 TeV, and 3 TeV. The luminosity performance of the first stage at 380 GeV is presented including the impact of static and dynamic imperfections. These calculations are performed with fully realistic tracking simulations from the exit of the damping rings to the interaction point and including beam-beam effects in the collisions. A luminosity of 4.3×1034 cm-2 s-1 can be achieved with a perfect collider, which is almost three times the nominal luminosity target of 1.5×1034 cm-2 s-1. In simulations with static imperfections, a luminosity of 2.35×1034 cm-2 s-1 or greater is achieved by 90% of randomly misaligned colliders. Expressed as a percentage of the nominal luminosity target, this is a surplus of approximately 57%. Including the impact of ground motion, a luminosity surplus of 53% or greater can be expected for 90% of colliders. The average expected luminosity is 2.8×1034 cm-2 s-1, which is almost twice the nominal luminosity target.