Stephane Fartoukh

A First Baseline for the Magnets in the High Luminosity LHC Insertion Regions

The High Luminosity LHC (HL-LHC) project aims at accumulating 3000 fb-1 in the years 2023-2035, i.e., ten times more w.r.t. the nominal LHC performance expected for 2010-2021. One key element to reach this challenging performance is a new insertion region to reduce the beam size in the interaction point by approximately a factor two. This requires larger aperture magnets in the region spanning from the interaction point to the matching section quadrupoles. This aperture has been fixed to 150 mm for the inner triplet quadrupoles in 2012. In this paper, we give a first baseline of the interaction region. We discuss the main motivations that lead us to choose the technology, the combination of fields/gradients and lengths, the apertures, the quantity of superconductor, and the operational margin. Key elements are also the constraints given by the energy deposition in terms of heat load and radiation damage; we present the main features related to shielding and heat removal.

BREACHING THE PHASE I OPTICS LIMITATIONS FOR THE HL-LHC

This paper scrutinizes the performance goal of the HLLHC Project and proposes a solution to reach it. This solution is based on an Achromatic Telescopic Squeezing (ATS) principle which can push β ∗ well below the limits which were identified in the context of the so-called Phase I Upgrade studies. The novel optics scheme is described, with its main weak points, possible mitigation measures and hardware modifications needed in the LHC ring in order to implement it. Other implications or by-products are also highlighted. Some of them are rather exotic and are worth to be mentioned in the abstract even if not completely developed in the paper: the possibility to run with a third low-β experiment installed in IR3 or IR7 (which is an interesting direction for a smooth co-habitation between the HL-LHC and the LHeC), a notable reduction of the IBS growth rate in the longitudinal plane (generally the most critical plane), or a boost by more than one order of magnitude for the efficiency of the Landau octupoles, making them strong enough to shape the head-on beam-beam tune footprint (but without yet any demonstration of the possible benefits) or, at least, to relax the constraints on the transverse impedance budget of the LHC at 7 TeV.

A statistical approach to analyse effect of misalignments and correction algorithms in high-energy linacs

This paper presents a new and general tracking method capable of analysing, in a statistical way, the dipole wakefield effects on a high-energy charged-particle beam.