Abstract
In the Collider Run II, the Tevatron operates with 36 high intensity bunches of 980 GeV protons and antiprotons. Particles not captured by the Tevatron RF system pose a threat to quench the superconducting magnet during acceleration or at beam abort. We describe the main mechanisms for the origination of this uncaptured beam, and present measurements of its main parameters by means of a newly developed diagnostics system. The Tevatron Electron Lens is effectively used in the Collider Run II operation to remove uncaptured beam and keep its intensity in the abort gaps at a safe level.
Highlights
The Tevatron is a 6.3 km long circular collider operating with 36 proton and 36 antiproton bunches at a beam energy of 980 GeV
Uncaptured beam has been found to be very dangerous for Tevatron operation in the collider run II
We identified the main mechanisms of uncaptured beam generation, namely intrabeam scattering and longitudinal instabilities, are dominant at the injection energy of 150 GeV and at the top energy of 980 GeV while rf noise and rf cavity trips contribute occasionally at 980 GeV
Summary
The Tevatron is a 6.3 km long circular collider operating with 36 proton and 36 antiproton bunches at a beam energy of 980 GeV. Coalescing in the MI typically leaves a few percent of the beam particles outside rf buckets These particles are transferred together with the main bunches. This energy loss is not being replenished by the rf system, so they slowly spiral radially inward and die on the collimators, which determine the tightest aperture in the Tevatron during collisions. The total uncaptured beam intensity is a product of the rate at which particles leak out of the main bunches and the time required for them to leave the machine. The outermost orbit, called the separatrix, determines the boundary of the rf bucket: p
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