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The beam scrapers were at 0R04 when it was the middle of the chicane. I think they then wound up in PEPPo.</div>
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Would be nice to have a robot for real time surveying.</div>
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Mike</div>
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<div id="divRplyFwdMsg" dir="ltr"><font face="Calibri, sans-serif" style="font-size:11pt" color="#000000"><b>From:</b> BTeam <bteam-bounces@jlab.org> on behalf of Jay Benesch <benesch@jlab.org><br>
<b>Sent:</b> Friday, June 18, 2021 9:07 AM<br>
<b>To:</b> bteam@jlab.org <bteam@jlab.org><br>
<b>Subject:</b> [BTeam] Beam-based aperture measurements with movable collimator jaws as performance booster of the CERN Large Hadron Collider</font>
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<div class="PlainText">In skimming this I had two thoughts that I'll throw out to get shot down<br>
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1. Could we install movable collimators in the NE spreader to improve our ability to find the tight spots that cause BLM trips? I recall Valeri had movable collimators installed but I can't remember location. I do remember them being removed.
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2. Can the beam be blown up with the first step triplet, starting from fourth pass and working to lower energy, followed by aperture scan to try to find tight spots? Not useful if the problem is before/in the first step but no new hardware required.
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<a href="https://arxiv.org/abs/2106.09656">https://arxiv.org/abs/2106.09656</a><br>
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Beam-based aperture measurements with movable collimator jaws as performance booster of the CERN Large Hadron Collider<br>
N. Fuster-Martínez, R. W. Aßmann, R. Bruce, M. Giovannozzi, P. Hermes, A. Mereghetti, D. Mirarchi, S. Redaelli, J. Wenninger<br>
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The beam aperture of a particle accelerator defines the clearance available for the circulating beams and is a parameter of paramount importance for the accelerator performance. At the CERN Large Hadron Collider (LHC), the knowledge and control of the available
aperture is crucial because the nominal proton beams carry an energy of 362 MJ stored in a superconducting environment. Even a tiny fraction of beam losses could quench the superconducting magnets or cause severe material damage. Furthermore, in a circular
collider, the performance in terms of peak luminosity depends to a large extent on the aperture of the inner triplet quadrupoles, which are used to focus the beams at the interaction points. In the LHC, this aperture represents the smallest aperture at top-energy
with squeezed beams and determines the maximum potential reach of the peak luminosity. Beam-based aperture measurements in these conditions are difficult and challenging. In this paper, we present different methods that have been developed over the years for
precise beam-based aperture measurements in the LHC, highlighting applications and results that contributed to boost the operational LHC performance in Run 1 (2010-2013) and Run 2 (2015-2018).
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Comments: 21 pages, 14 figures<br>
Subjects: Accelerator Physics (physics.acc-ph)<br>
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