Luminosity Scans for Beam Diagnostics

TL;DR

This paper introduces a new fast luminosity separation scan method at the CERN LHC that enables precise, bunch-by-bunch beam diagnostics and provides insights into beam-beam effects through direct measurements and simulations.

Contribution

It presents a novel emittance scan technique performed systematically at the LHC, allowing detailed beam diagnostics and validation of beam-beam interaction models.

Findings

Successful implementation of emittance scans at the LHC

Quantitative observation of long-range beam-beam PACMAN effects

Good agreement between measurements and numerical simulations

Abstract

A new type of fast luminosity separation scans ("Emittance Scans") was introduced at the CERN Large Hadron Collider (LHC) in 2015. The scans were performed systematically in every fill with full-intensity beams in physics production conditions at the Interaction Point (IP) of the Compact Muon Solenoid (CMS) experiment. They provide both emittance and closed orbit measurements at a bunch-by-bunch level. The precise measurement of beam-beam closed orbit differences allowed a direct, quantitative observation of long-range beam-beam PACMAN effects, which agrees well with numerical simulations from an improved version of the TRAIN code.