The Use of Ionization Electron Columns for Space-Charge Compensation in High Intensity Proton Accelerators

Abstract

Abstract. We discuss a recent proposal to use strongly magnetized electron columns created by beam ionization of the residual gas for compensation of space charge forces of high intensity proton beams in synchrotrons and linacs. The electron columns formed by trapped ionization electrons in a longitudinal magnetic field that assures transverse distribution of electron space charge in the column is the same as in the proton beam. Electrostatic electrodes are used to control the accumulation and release of the electrons. Ions are not magnetized and drift away without affecting the compensation. Possible technical solution for the electron columns is presented. We also discuss the first numerical simulation results for space-charge compensation in the FNAL Booster and results of relevant beam studies in the Tevatron.

US Accelerator R&D Program Toward Intensity Frontier Machines

“…Several experiments are planned at IOTA: i) Test of Integrable Optics (IO) with Electrons with a goal to create IO accelerator lattice with several additional integrals of motion (angular momentum and McMillan-type integrals, quadratic in momentum); ii) IO with Non-linear Magnets, Test with Protons will demonstrate nonlinear integrable optics with protons with a large betatron frequency spread ΔQSC>1 and stable particle motion in a realistic accelerator design; iii) IO with e-lens(es), Tests with Protons to demonstrate IO with non-Laplacian electron lenses with the electron charge distribution as n(r)=1/(1+r 2 ) 2 to obtain a large betatron frequency spread ΔQSC>1 and stable particle motion in a realistic accelerator design; iv) Space-Charge Compensation (SCC) with e-lens(es), Test with Protons has the main goal of demonstrating SCC with Gaussian ELs with protons with a large betatron frequency spread ΔQ>0.5 and stable particle motion in a realistic accelerator design. Similar SCC tests are envisioned with electron columns [8].…”

“…Experimental R&D with high brightness beam at IOTA ring Progress of the Intensity Frontier accelerator based HEP is hindered by fundamental beam physics phenomena such as space-charge effects, beam halo formation, particle losses, transverse and longitudinal instabilities, beam loading, inefficiencies of beam injection and extraction, etc. The Integrable Optics Test Accelerator (IOTA) facility at Fermilab [4] is being built as a unique test-bed for transformational R&D towards the next generation high-intensity proton facilitiessee The goal of the IOTA research program is to carry out experimental studies of transformative techniques to control proton beam instabilities and losses, such as integrable optics [6] with non-linear magnets and with electron lenses, and space-charge compensation with electron lenses and electron columns [7,8] at beam intensities and brightness 3-4 times the current operational limits, i.e., at the space-charge parameter ΔQSC approaching or even exceeding 1. Several experiments are planned at IOTA: i) Test of Integrable Optics (IO) with Electrons with a goal to create IO accelerator lattice with several additional integrals of motion (angular momentum and McMillan-type integrals, quadratic in momentum); ii) IO with Non-linear Magnets, Test with Protons will demonstrate nonlinear integrable optics with protons with a large betatron frequency spread ΔQSC>1 and stable particle motion in a realistic accelerator design; iii) IO with e-lens(es), Tests with Protons to demonstrate IO with non-Laplacian electron lenses with the electron charge distribution as n(r)=1/(1+r 2 ) 2 to obtain a large betatron frequency spread ΔQSC>1 and stable particle motion in a realistic accelerator design; iv) Space-Charge Compensation (SCC) with e-lens(es), Test with Protons has the main goal of demonstrating SCC with Gaussian ELs with protons with a large betatron frequency spread ΔQ>0.5 and stable particle motion in a realistic accelerator design.…”

Electron lenses: historical overview and outlook

“…Initial modeling of such compensation indicated the method had significant promise [59]. Electron columns -see figure 7 -were proposed as a possible technical solution for simple and economical space-charge compensation devices [60,61]. They have no external electron source and assume trapping of ionization electrons (created by beam ionization of the residual gas) in a strong longitudinal magnetic field that assures transverse distribution of the electron cloud space charge to be the same or close to that of the proton beam.…”

IOTA (Integrable Optics Test Accelerator): facility and experimental beam physics program

“…The IOTA ring will be also used to study space charge compensation using so called "electron column" [61]. The compensation is achieved through trapping and controlling of intense negative charge of electrons, generated from residual gas ionizations by intense and stable circulating proton beams inside a strong solenoidal magnetic field (figure 23).…”