Landau Damping with Electron Lenses in Space-Charge Dominated Beams

Abstract

Progress on the Intensity Frontier of high energy physics critically depends on record high intensity charged particles accelerators. Beams in such machines become operationally limited by coherent beam instabilities, particularly enhanced in the regime of strong space charge (SC). Usual methods to control the instabilities, such as octupole magnets, beam feedback dampers and employment of chromatic effects, become less effective and insufficient. In [1] it was proposed to employ electron lenses for introduction of sufficient spread in particle oscillation frequencies needed for beam stabilization and in [2] it was shown that electron lenses are uniquely effective for Landau damping of transverse beam instabilities in high energy particle accelerators and their employment does not compromise incoherent (single particle) stability, dynamic aperture and the beam lifetime. Here we consider an important issue of effectiveness of the Landau damping with electron lenses in space-charge dominated beams and demonstrate that the desired stability can be assured with proper choice of the electron beam parameters and current distributions.

Landau Damping of Beam Instabilities by Electron Lenses

“…Electron lenses may also be helpful in low-energy high-brightness accelerators, where Landau damping is intrinsically suppressed by a shift of single particle tunes away from the frequency of coherent oscillations [30]; a preliminary study of this issue is suggested in Ref. [31].…”

Electron lenses: historical overview and outlook

“…Similar practical proposals considered a hollow bi-Gaussian electron lens (see Fig. 2a, no.5) as the nonlinear element for creating a tunespread for Landau damping in the 8 GeV proton Recycler storage ring [71] and in the space-charge dominated high intensity beams [72].…”

“…For example, within the parameters of the Future Circular Collider (FCC-hh), a single few meters long conventional electron lens would provide stabilization superior to tens of thousands of superconducting octupole magnets. Similar practical proposals considered a hollow bi-Gaussian electron lens (see figure 2a, no.5) as the nonlinear element for creating a tunespread for Landau damping in the 8 GeV proton Recycler storage ring [75] and in the space-charge dominated high intensity beams [76].…”

“…Other attractive ideas that may come forward for exploration in the next decade include: i) conceptual studies and initial development of the electron current sheets (jaws) above and below flat 𝑒 + 𝑒 − beams in the SuperKEKB collider to reduce the background and protect collimators, and, possibly, to reduce the machine impedance; ii) technological development of "passive" electron lenses (electron columns); and iii) further development of the modeling capabilities for the lenses themselves and addressing technological challenges, such as, e.g., faster pulse-to-pulse current modulation [87].…”

Beam physics research with the IOTA electron lens

“…Studies presented in refs. [85,86] predicted that there are regimes for which Landau damping with electron lenses, described in section 2.3, is effective under space-charge conditions as well. Experiments with protons in IOTA could shed light on this topic, with a significant impact on the performance of high-intensity accelerators.…”