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TY - CONF AU - Lechner, A. AU - Auchmann, B. AU - Bravin, E. AU - Gorzawski, A.A. AU - Grob, L. K. AU - Holzer, E.B. AU - Lindstrom, B. AU - Medvedeva, T. AU - Mirarchi, D. AU - Schmidt, R. AU - Valette, M. AU - Wollmann, D. ED - Koscielniak, Shane ED - Satogata, Todd ED - Schaa, Volker RW ED - Thomson, Jana TI - Beam Loss Measurements for Recurring Fast Loss Events During 2017 LHC Operation Possibly Caused by Macroparticles J2 - Proc. of IPAC2018, Vancouver, BC, Canada, April 29-May 4, 2018 C1 - Vancouver, BC, Canada T2 - International Particle Accelerator Conference T3 - 9 LA - english AB - The availability of the LHC machine was adversely affected in 2017 by tens of beam aborts provoked by frequent loss events in one standard arc cell (16L2). In most of the cases, the dumps were triggered by concurrently developing fast beam instabilities leading to particle losses in the betatron cleaning insertion. Many of the events started with a distinct sub-millisecond loss peak comparable to regular dust particle events, which have been observed along all the LHC since the start-up. In contrast to regular dust events, persistent losses developed in cell 16L2 after the initial peaks which can possibly be explained by a phase transition of macroparticles to the gas phase. In this paper, we summarize the observed loss characteristics such as spatial loss pattern and time profiles measured by Beam Loss Monitors (ionization chambers). Based on the measurements, we estimate the energy deposition in macroparticles and reconstruct proton loss rates as well as the gas densities after the phase transition. Differences between regular dust events and events in 16L2 are highlighted and the ability to induce magnet quenches is discussed. PB - JACoW Publishing CP - Geneva, Switzerland SP - 780 EP - 783 KW - proton KW - simulation KW - operation KW - dipole KW - insertion DA - 2018/06 PY - 2018 SN - 978-3-95450-184-7 DO - 10.18429/JACoW-IPAC2018-TUPAF040 UR - http://jacow.org/ipac2018/papers/tupaf040.pdf ER -