Title: Compensation of the long-range beam-beam interactions as a path towards new configurations for the high luminosity LHC

Abstract

Colliding bunch trains in a circular collider demands a certain crossing angle in order to separate the two beams transversely after the collision. The magnitude of this crossing angle is a complicated function of the bunch charge, the number of long-range beam-beam interactions, of β* and type of optics (flat or round), and possible compensation or additive effects between several low-β insertions in the ring depending on the orientation of the crossing plane at each interaction point. About 15 years ago, the use of current bearing wires was proposed at CERN in order to mitigate the long-range beam-beam effects [J.P. Koutchouk, CERN Report No. LHC-Project-Note 223, 2000], therefore offering the possibility to minimize the crossing angle with all the beneficial effects this might have: on the luminosity performance by reducing the need for crab-cavities or lowering their voltage, on the required aperture of the final focus magnets, on the strength of the orbit corrector involved in the crossing bumps, and finally on the heat load and radiation dose deposited in the final focus quadrupoles. In this paper, a semianalytical approach is developed for the compensation of the long-range beam-beam interactions with current wires. This reveals the possibility of achieving optimal correction throughmore » a careful adjustment of the aspect ratio of the β functions at the wire position. We consider the baseline luminosity upgrade plan of the Large Hadron Collider (HL-LHC project), and compare it to alternative scenarios, or so-called ''configurations,'' where modifications are applied to optics, crossing angle, or orientation of the crossing plane in the two low-β insertions of the ring. Furthermore, for all these configurations, the beneficial impact of beam-beam compensation devices is then demonstrated on the tune footprint, the dynamical aperture, and/or the frequency map analysis of the nonlinear beam dynamics as the main figures of merit.« less

Authors:

Fartoukh, Stéphane; Valishev, Alexander; Papaphilippou, Yannis; Shatilov, Dmitry

Publication Date:

Tue Dec 01 00:00:00 EST 2015

Research Org.:

Fermi National Accelerator Laboratory (FNAL), Batavia, IL (United States)

Sponsoring Org.:

USDOE Office of Science (SC), High Energy Physics (HEP)

OSTI Identifier:

1227334

Alternate Identifier(s):

OSTI ID: 1235051

Report Number(s):

FERMILAB-PUB-15-539-APC
Journal ID: ISSN 1098-4402; PRABFM; 121001

Grant/Contract Number:  

AC02-07CH11359

Resource Type:

Published Article

Journal Name:

Physical Review Special Topics. Accelerators and Beams

Additional Journal Information:

Journal Name: Physical Review Special Topics. Accelerators and Beams Journal Volume: 18 Journal Issue: 12; Journal ID: ISSN 1098-4402

Publisher:

American Physical Society

Country of Publication:

United States

Language:

English

Subject:

43 PARTICLE ACCELERATORS