Experimental studies of compensation of beam–beam effects with Tevatron electron lenses

Abstract

Applying the space-charge forces of a low-energy electron beam can lead to a significant improvement of the beam-particle lifetime limit arising from the beam-beam interaction in a highenergy collider [1]. In this article we present the results of various beam experiments with "electron lenses," novel instruments developed for the beam-beam compensation at the Tevatron, which collides 980-GeV proton and antiproton beams. We study the dependencies of the particle betatron tunes on the electron beam current, energy and position; we explore the effects of electron-beam imperfections and noises; and we quantify the improvements of the high-energy beam intensity and the collider luminosity lifetime obtained by the action of the Tevatron Electron Lenses.

Long-Range Beam–Beam Compensation Using Wires

“…On the other hand such an implementation is beyond what has been achieved so far: Assuming an effective length of 6 m on both sides of the IP an electron beam current of about 30 A would be needed in order to produce the field equivalent to a 1 m long wire powered at 177 A. This is about an order of magnitude larger than what has been achieved for the Tevatron Electron Lens [27,34] and with the electron lenses at RHIC [35]. A factor of 2 could be gained by placing a second electron beam wire on the other side of the IP, resulting in a total of eight installations.…”

Collider Beam Physics

“…The collision with the electron beam can cancel part of the head-on tune spread (and possibly of the resonance excitation) induced in the same main beam by primary collisions with a positively charged (proton) beam. A first set of electron lenses was implemented and operated at the Tevatron [49]. Instead of compensating head-on beam-beam effects, the Tevatron electron lenses were successfully used as pulsed quadrupoles to equalize the tunes along a bunch train.…”

“…collisions with a large Piwinski angle [62] -including "superbunch" schemes in hadron colliders [3,39]; "nanobeam schemes" proposed for the former SuperB (together with crab waist collisions [60]) and adopted for SuperKEKB, in which the short length of the beambeam overlap enables the implementation of an extremely low  y * [63];; colliding hadron bunches with longitudinally flat profile [64,65]; or compensating the beam-beam tune shift with electron(-beam) lenses [48] as implemented at the Tevatron [49] and at RHIC [50], and proposed for the HL-LHC.…”

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

“…They are described in great detail in [7,8]. The TELs employ strong solenoids and have electrostatic electrodes which can be used to arrange the configuration similar to what is depicted in Fig.1.…”