Space-charge compensation in high-intensity proton rings

Abstract

Recently, it was proposed to use negatively charged electron beams for compensation of beambeam effects due to protons in the Tevatron collider [1]. We show that a similar compensation is possible in space-charge dominated low energy proton beams. The idea has a potential of severalfold increase of the FNAL Booster beam brightness. Best results will be obtained using three electron lenses around the machine circumference, using co-moving electron beam with time structure and profile approximately matched to the proton beam. This technique, if feasible, will be more cost effective than the straightforward alternative of increasing the energy of the injection linac.

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

“…There are two ways an electron lens can be used as a space-charge compensator. One relies on an electron gun that generates the required charge distribution in transverse space and possibly in time, to reproduce the bunch shape of the circulating beam [58]. In the other scheme, the so-called 'electron column', the electrons are generated by ionization of the residual gas and trapped axially by electrodes and transversely by the solenoidal field, in a configuration similar to a Penning-Malmberg trap [59] (see also section 3.4 below).…”

Accelerator R&D at Fermilab’s FAST/IOTA for Future High Intensity Proton Accelerators

“…Both neutralize the space charge force by creating an electron distribution that matches that of the circulating proton beam. The first method is similar to the electron lens in that it works by using an electron gun to generate the desired distribution, then injecting the electrons into the ring, co-propagating with the proton beam [13]. After a short distance, the electrons are extracted from the ring (see Fig.…”

Compensating tune spread induced by space charge in bunched beams

“…Since the compensation scheme we are presenting here does not depend on the details of the transverse beam distribution, e.g. similarly to compensation techniques suggested for coasting beams, the transverse profile of the electron beam (or a column) should compensate both the tune shift and its dependence on the amplitudes of the transverse oscillations [24][25][26][27][28]. Naturally the maximum tune shift is experienced by the particles in the center of the beam, while the particles with large amplitude of oscillations have a smaller value of the tune shift.…”

“…A number of practical schemes for space-charge tune shift and tune spread compensation using an electron beam colliding with hadron beam (e.g. an electron lens) or an electron column induced in a residual gas [24][25][26][27][28] were suggested. The tune shift given by the colliding beam does not suffer from γ h −2 cancelation.…”

“…As explained in [24,28], selecting a proper transverse distribution of electron beam, one can match the space charge tune shift dependence on the transverse amplitudes. The only, but important, short-coming of this method is that the tune-shift introduced by the electron lens (or the column) is identical for all particles independent on the longitudinal location inside the bunch.…”