Experimental results of the laserwire emittance scanner for LINAC4 at CERN

TL;DR

This paper presents experimental results of a laserwire emittance scanner designed for LINAC4 at CERN, demonstrating a novel non-invasive method to measure beam emittance using laser photo-detachment.

Contribution

The paper introduces a new laserwire emittance measurement system for LINAC4, detailing its design, concept, and experimental validation, advancing non-invasive beam diagnostics.

Findings

Successful demonstration of laserwire emittance measurement

Effective laser beam scanning across H- beam

Accurate reconstruction of transverse emittance

Abstract

Within the framework of the LHC Injector Upgrade (LIU), the new LINAC4 is currently being commissioned to replace the existing LINAC2 proton source at CERN. After the expected completion at the end of 2016, the LINAC4 will accelerate H- ions to 160 MeV. To measure the transverse emittance of the H- beam, a method based on photo-detachment is proposed. This system will operate using a pulsed laser with light delivered via an optical fibre and subsequently focused through a thin slice of the H- beam. The laser photons have sufficient energy to detach the outer electron and create H0/e- pairs. In a downstream dipole, the created H0 particles are separated from the unstripped H- ions and their distribution is measured with a dedicated detector. By scanning the focused laser across the H- beam, the transverse emittance of the H- beam can be reconstructed. This paper will first discuss the concept, design and simulations of the laser