Since 2015 the LHC has been operating at 6.5 TeV. In 2016 the β-functions at the interaction points of ATLAS and CMS were squeezed to 0.4 m. This is below the design β Ã ¼ 0.55 m at 7 TeV, and has been instrumental to surpass the design luminosity of 10 34 cm −2 s −1. Achieving a lower than nominal β Ã has been possible thanks to the extraordinary performance of the LHC, in which the control of the optics has played a fundamental role. Even though the β-beating for the virgin machine was above 100%, corrections reduced the rms β-beating below 1% at the two main experiments and below 2% rms around the ring. This guarantees a safe operation as well as providing equal amount of luminosity for the two experiments. In this article we describe the recent improvements to the measurement, correction algorithms and technical equipment which allowed this unprecedented control of the optics for a high-energy hadron collider.
Abstract-Beam instabilities cover a wide range of effects in particle accelerators and they have been the subject of intense research for several decades. As the machines performance was pushed new mechanisms were revealed and nowadays the challenge consists in studying the interplays between all this intricate phenomena, as it is very often not possible to treat the different effects separately. The aim of this paper is to review the main mechanisms, discussing in particular the recent developments of beam instability theories and simulations.
With the progress made in 2015, the beams produced by the CERN Proton Synchrotron using multiturn extraction (MTE) have been delivered to the Super Proton Synchrotron (SPS) for the fixed-target physics run. Operation successfully started in the second half of September 2015 and continued until the end of the proton physics program by mid November. In this paper the overall performance and beam quality is discussed in detail considering the complete chain of accelerators, from the PS-Booster to the SPS. Moreover, a thorough comparison of the global performance of the MTE scheme against the previously used technique, the so-called continuous transfer (CT), is also carried out.
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