MD 3246: 16L2 UFO dynamics investigations

Abstract

Micrometer sized particles (UFOs) entering the beam are a known cause of localized beam losses since the beginning of high intensity beam operations, however the origin of these particles is not fully known. Furthermore, during 2017 a new type of UFO events appeared around the 16L2 interconnection in the LHC, leading to beam instabilities resulting in a major impact on beam availability. In MD#2889 these 16L2 UFOs were studied with the help of very fast diamond beam loss monitors (dBLM) that were installed at the source of the UFOs, providing important data on the dynamics of the UFOs. However, only one event could be recorded. In order to acquire more data, and of better quality using the significantly improved data acquisition system, this MD was executed. The MD was done in parallel with MD2484. and the procedure was adjusted for both MDs to profit as much as possible. The UFO part of the MD was split into two parts; one with a small number of blown-up bunches as not to negatively impact the other MD, and lastly one EOF where a large number of bunches were to be blown-up and a 16L2 event was to be provoked, however the beams were dumped at the start of the blow-up. One small event was recorded during the first part of the MD