In this paper, we report the progress of the Tevatron Beam-Beam Compensation (BBC) project [1]. Proton and antiproton tuneshifts of the order of 0.009 induced by electron beam have been reported in [2], suppression of an antiproton emittance growth in the Tevatron High Energy Physics (HEP) store has been observed, too [1]. Currently, the first electron lens (TEL1) is in operational use as the Tevatron DC beam cleaner. Over the last two years, we have greatly improved its reliability. The 2nd Tevatron electron lens (TEL2) is under the final phase of development and is being prepared for installation in the Tevatron in 2005. OPERATION AND STUDIES WITH TEL1The TEL1 was mainly operated as a gentle remover of the Tevatron proton DC beam in the abort gaps [3], which keeps the Tevatron safe from the quench during abort. It also effectively surpresses the proton halo loss spikes which cause high background and limit the CDF detector operation. TEL1 was also instrumental for calibration of the Tevatron Abort Gap Monitors [5]. Since luminosity runs are of much higher priority, time for BBC beam studies was and is very limited. Issues Identified in Previous StudiesThe tuneshift produced by TEL-1 did help to reduce growth of a single antiproton bunch emittance at the beginning of one HEP store (see e.g.[1]).The effect was not repeated reqularly because of two reasons; a) in consequent stores, a global tune correction was introduced that greatly suppressed emittance growth of all antiproton bunches; b) there were difficulties with proper alignment of the electron beam w.r.t. the antiproton beam. The latter is caused by a systematic dependence of the BPM electric centers on frequency. The scale of the offset is about 1-1.5 mm (see discussion below). A mm-scale misalignment of high-current electron beam caused full-scale tuneshift error and thought to lead to a significant reduction of of antiproton lifetime.
In the framework of collaboration between IHEP and FNAL, a magnetic system of the Tevatron Electron Lens (TEL) has been designed and built. The TEL is currently installed in the superconducting ring of the Tevatron proton-antiproton collider and used for experimental studies of beam-beam compensation [1].
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