Vacuum Acceptance Tests for Particle Accelerator Equipment

The effective and reliable operation of particle accelerator machines is strongly related to obtaining and keeping the required ultra-high vacuum level. This paper briefly presents some generic requirements to take in consideration for components that need to be installed in a particle accelerator like design constraints, materials choices, chemical cleaning process, outgassing rate, and their possible mitigation. Moreover, it will discuss vacuum acceptance tests put in place in the CERN accelerator complex for both, baked and unbaked system.Comment: 11 pages, 8 figures, Proceedings of the 2017 CERN Accelerator School course on Vacuum for Particle Accelerators, Glumsl\"ov, (Sweden

Achievement and Evaluation of the Beam Vacuum Performance of the LHC Long Straight Sections

The bake-out and activation of the TiZrV NEG coatings of the 6 km Long Straight Sections (LSS) of the Large Hadron Collider (LHC) is in its final step. After the bakeout and the NEG activation, the average ultimate pressure, over more than one hundred vacuum sectors, is below 10^-10 Pa. Therefore, the nominal requirement for the four experimental insertions is fulfilled. The nominal performances are also ensured for all the insertions housing the collimator systems, the RF cavities and the beam dumping systems. The main difficulties encountered during the bake-out and the activation of the NEG coated chambers is presented and discussed. In particular, the acceptance test and the limiting factors of the reached ultimate pressures are addressed. Furthermore, the influence on the ultimate pressures of the beam components (collimators, beam instrumentation, etc.) is discussed. Finally, preliminary results obtained from a NEG vacuum pilot sector installed in the laboratory and dedicated to the evaluation of the NEG performance is presente

A simple, high-yield, apparatus for NEG coating of vacuum beamline elements

Non-Evaporable Getter (NEG) materials are extremely useful in vacuum systems for achieving Ultra High Vacuum. Recently, these materials have been used to coat the inner surfaces of vacuum components, acting as an internal, passive, vacuum pump. We have constructed a low cost apparatus, which allows coating of very small diameter vacuum tubes, used as differential pumping stages. Despite the relative ease of construction, we are routinely able to achieve high coating yields. We further describe an improvement to our system, which is able to achieve the same yield, at an even lower complexity by using an easily manufactured permanent magnet arrangement. The designs described are extendible to virtually any combination of length and diameter of the components to be coated

Magnetization on rough ferromagnetic surfaces

Journal ArticleUsing Ising-model Monte Carlo simulations, we show a strong dependence of surface magnetization on surface roughness. On ferromagnetic surfaces with spin-exchange coupling larger than that of the bulk, the surface magnetic ordering temperature decreases toward the bulk Curie temperature with increasing roughness. For surfaces with spin-exchange coupling smaller than that of the bulk, a crossover behavior occurs: at low temperature, the surface magnetization decreases with increasing roughness; at high temperature, the reverse is true

Update on Beam Induced RF Heating in the LHC

Since June 2011 the rapid increase of the luminosity performance of the LHC has come at the expense of both increased temperature and pressure of specific, near-beam, LHC equipment. In some cases, this beam induced heating has caused delays while equipment cool-down, beam dumps and even degradation of some devices. This contribution gathers the observations of beam induced heating, attributed to longitudinal beam coupling impedance, their current level of understanding and possible actions planned to be implemented during the 1st LHC Long Shutdown (LS1) in 2013-2014

Machine learning for beam dynamics studies at the CERN Large Hadron Collider

Machine learning entails a broad range of techniques that have been widely used in Science and Engineering since decades. High-energy physics has also profited from the power of these tools for advanced analysis of colliders data. It is only up until recently that Machine Learning has started to be applied successfully in the domain of Accelerator Physics, which is testified by intense efforts deployed in this domain by several laboratories worldwide. This is also the case of CERN, where recently focused efforts have been devoted to the application of Machine Learning techniques to beam dynamics studies at the Large Hadron Collider (LHC). This implies a wide spectrum of applications from beam measurements and machine performance optimisation to analysis of numerical data from tracking simulations of non-linear beam dynamics. In this paper, the LHC-related applications that are currently pursued are presented and discussed in detail, paying also attention to future developments

Beam gas curtain monitor: Vacuum studies for LHC integration and operation

A beam gas curtain (BGC) monitor has been designed to obtain information about the relative position between the LHC proton beam and the hollow electron lens electron beam through a minimally invasive process. Its working principle relies on intersecting the path of both beams with a supersonic gas curtain, introduced transversely into the LHC beamline, to produce a fluorescence signal. As an intermediate project stage (phase II), a preliminary version of the BGC monitor has been installed into the LHC beamline. To ensure the successful integration of the monitor and subsequent operation under LHC ultrahigh vacuum conditions, a series of vacuum studies have been performed. These can be classified as follows: An off-line laboratory test campaign, to assess BGC behavior during pump down and gas injections; simulations and analytical calculations, to evaluate BGC behavior and estimate the impact of its installation and operation in the LHC. This document will briefly present the off-line tests campaign, followed by a more extensive description of the simulations performed

The LHCb upgrade I

The LHCb upgrade represents a major change of the experiment. The detectors have been almost completely renewed to allow running at an instantaneous luminosity five times larger than that of the previous running periods. Readout of all detectors into an all-software trigger is central to the new design, facilitating the reconstruction of events at the maximum LHC interaction rate, and their selection in real time. The experiment's tracking system has been completely upgraded with a new pixel vertex detector, a silicon tracker upstream of the dipole magnet and three scintillating fibre tracking stations downstream of the magnet. The whole photon detection system of the RICH detectors has been renewed and the readout electronics of the calorimeter and muon systems have been fully overhauled. The first stage of the all-software trigger is implemented on a GPU farm. The output of the trigger provides a combination of totally reconstructed physics objects, such as tracks and vertices, ready for final analysis, and of entire events which need further offline reprocessing. This scheme required a complete revision of the computing model and rewriting of the experiment's software

Vacuum Acceptance Tests for Particle Accelerator Equipment

The effective and reliable operation of particle accelerator machines is strongly related to obtaining and keeping the required ultra-high vacuum level. This paper briefly presents some generic requirements to take in consideration for components that need to be installed in a particle accelerator like design constraints, materials choices, chemical cleaning process, outgassing rate, and their possible mitigation. Moreover, it will discuss vacuum acceptance tests put in place in the CERN accelerator complex for both, baked and unbaked system