Michael Hostettler

JACoW : Online coupling measurement and correction throughout the LHC cycle

With high intensity beams, a precise measurement and effective correction of the betatron coupling is essential for the performance of the Large Hadron Collider (LHC). In order to measure this parameter, the LHC transverse damper (ADT), used as an AC dipole, will provide the necessary beam excitation. The beam oscillations will be recorded by the Beam Position Monitors and transmitted to dedicated analysis software. We set up the project with a 3-layer software architecture: The central part is a Java server, orchestrating the different actors: The Graphical User Interface, the control and triggering of the ADT AC dipole, the BPMs, the oscillation analysis (partly in Python), and finally the transmission of the correction values. The whole system was developed in a team using Scrum, an iterative and incremental agile software development framework. In this paper we present an overview of the system, experience from machine development and commissioning as well as how scrum helped us to achieve our goals. Improvement and re-use of the architecture with a nice decoupling between data acquisition and data analysis are also briefly discussed.

arXiv : Modeling and Measurements of Bunch Profiles at the LHC

At the LHC, the interplay between a series of effects (e.g. intrabeam scattering, longitudinal beam manipulations, machine non-linearities) can lead to a tails population change, that may result in non-Gaussian beam distributions. Since the calculated beam size depends on the tail formation, it is important to follow the bunch profile evolution. In this paper, the benchmarking of a Monte-Carlo simulation code able to track 3D particle distributions, with the analytical IBS formulas is discussed. Novel distribution functions are employed to describe the beam profiles, and are used as a guideline for generalizing emittance estimations due to IBS and radiation effects. The impact of the distribution shape on the evolution of the bunch characteristics is studied. Bunch profile observations from the LHC Run 2 are compared to simulations and analytical results.

Observations from LHC proton-proton operation

This paper describes two distinct effects observed during the operation of the LHC in 2012: first, the impacts on beam parameter evolution of the end-of-squeeze instabilities encountered in the second half of the 2012 run; and, second, the very reproducible loss pattern of Beam 1 observed (while a similar pattern was negligible, if present at all, for Beam 2). Statistics for 2012 are provided and the impact on luminosity production is highlighted.