2018/05/04 by L. Prost, J.-P. Carneiro, J. -P. Carneiro +4
Engineering · Physics and Astronomy · #Accelerator Physics (physics.acc-ph) #FOS: Physical sciences #Magnetic confinement fusion research #Particle Accelerators and Free-Electron Lasers #Particle accelerators and beam dynamics #physics.acc-ph
paper · pdf · doi:10.48550/arxiv.1805.01920
10 pp
arxiv created 2018/05/04 · openalex publication_date 2018/05/04 · arxiv updated 2018/05/08 · openalex created_date 2019/06/27 · openalex updated_date 2026/07/28
In a Low Energy Beam Transport line (LEBT), the emittance growth due to the beam's space charge is typically suppressed by way of neutralization from either electrons or ions, which originate from ionization of the background gas. In cases where the beam is chopped, the neutralization pattern usually changes throughout the beginning of the pulse, causing the Twiss parameters to differ significantly from their steady state values, which, in turn, may result in beam losses downstream. For a modest beam perveance, there is an alternative solution, in which the beam is kept un-neutralized in the portion of the LEBT that contains the chopper. The emittance can be nearly preserved if the transition to the un-neutralized section occurs where the beam exhibits low transverse tails. This report introduces the rationale for the proposed scheme and formulates the physical arguments for it as well as its limitations. An experimental realization of the scheme was carried out at Fermilab's PIP2IT where low beam emittance dilution was demonstrated for a 5 mA, 30 keV H- beam.