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Internal Note
Report number CERN-ACC-NOTE-2014-0061
Title Study on off-momentum tail scraping in the LHC
Author(s) Mirarchi, D ; Redaelli, S ; Bruce, R
Corporate author(s) CERN. Geneva. ATS Department
Publication 2014
Imprint 22 Aug 2014
Number of pages 13
Subject category Accelerators and Storage Rings
Accelerator/Facility, Experiment CERN LHC
Project CERN Collimation
Keywords LHC beam scraping, ; o -momentum tail, ; collimation, ; abort gap cleaning,
Abstract A study on o-momentum tail population in the LHC was performed through collimator scraping at high dispersion region. High intensity measurements at the end of a physics ll with 25ns bunch spacing were carried out on 16th December 2012, using primary collimators (TCPs) in the momentum cleaning insertion (IR3) as scrapers. The o-momentum cuts were applied up to the level where the IR3 primary collimator is the aperture bottleneck for all particles outside the bucket, and the TCPs in the betatron cleaning insertion (IR7) are still the primary restriction of aperture of the machine in the transverse plane for particles inside the bucket. This because whether a particle is lost in IR3 or IR7 is not given only by the momentum oset but also by the betatron amplitude, as explained in the text. A signicant decay of the abort gap (AG) population was observed, while moving in the collimator jaw on the side where particles with negative o-momentum are expected. The level of the AG popupation achieved was at a similar level as when the active AG cleaner was on, opening the possibility to establish a passive AG cleaning with TCPs. At the end of the measurement the closed collimator jaw was opened in one step, allowing to see the repopulation time of the abort gap.
Submitted by [email protected]

 


 Record created 2014-08-22, last modified 2016-07-01


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