A Fibre Coupled, Low Power Laserwire Emittance Scanner at CERN LINAC4

Stephen Gibson, Gary Boorman, Alessio Bosco, Konstantin Kruchinin, Thomas Hofmann, Federico Roncarolo, Juergen Pozimski, Christoph Gabor, Alan Letchford

Research output: Chapter in Book/Report/Conference proceedingConference contribution


The new LINAC4 will accelerate H− ions to 160 MeV and ultimately replace the existing 50 MeV LINAC2 in the injector chain for the LHC upgrade. During commissioning in 2013, a laserwire scanner and diamond strip detector were installed for non-invasive emittance measurements of the 3 MeV H− beam. Synergy with the 3 MeV H− Front End Test Stand at RAL, has stimulated collaborative development of a novel laserwire system. A low peak power (8kW) pulsed laser is fibre-coupled for remote installation and alignment free operation. Motorized focusing optics enable remote control of the thickness and position of the laserwire delivered to the vacuum chamber, in which the laser light neutralises a small fraction of H− ions. Undeflected by a dipole magnet, these H atoms drift downstream, where their spatial profile is recorded by a highly sensitive diamond strip detector with ns-time resolution. We present first tests of the laserwire emittance scanner, including measurements of the photo detachment signal with respect to the background from residual gas interactions. The first laserwire transverse beam profile and emittance measurements are compared with conventional slit-grid diagnostics.
Original languageEnglish
Title of host publication5th International Particle Accelerator Conference
Subtitle of host publication15-20 June 2014 Dresden, Germany
Chapter06 Instrumentation, Controls, Feedback & Operational Aspects, T03 Beam Diagnostics and Instrumentation
Number of pages4
ISBN (Electronic)978-3-95450-132-8
Publication statusPublished - 20 Jun 2014

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