Resonant and random excitations on the proton beam in the Large Hadron Collider for active halo control with pulsed hollow electron lenses

We present the results of numerical simulations and experimental studies about the effects of resonant and random excitations on proton losses, emittances, and beam distributions in the Large Hadron Collider (LHC). In addition to shedding light on complex nonlinear effects, these studies are applied to the design of hollow electron lenses (HEL) for active beam halo control. In the High-Luminosity Large Hadron Collider (HL-LHC), a considerable amount of energy will be stored in the beam tails. To control and clean the beam halo, the installation of two hollow electron lenses, one per beam, is being considered. In standard electron-lens operation, a proton bunch sees the same electron current at every revolution. Pulsed electron beam operation (i.e., different currents for different turns) is also considered, because it can widen the range of achievable halo removal rates. For an axially symmetric electron beam, only protons in the halo are excited. If a residual field is present at the location of the beam core, these particles are exposed to time-dependent transverse kicks and to noise. We discuss the numerical simulations and the experiments conducted in 2016 and 2017 at injection energy in the LHC. The excitation patterns were generated by the transverse feedback and damping system, which acted as a flexible source of dipole kicks. Proton beam losses, emittances, and transverse distributions were recorded as a function of excitation patterns and strengths. The resonant excitations induced rich dynamical effects and nontrivial changes of the beam distributions, which, to our knowledge, have not previously been observed and studied in this detail. We conclude with a discussion of the tolerable and achievable residual fields and proposals for further studies.Comment: 33 pages, 32 figures, 46 references. Revised manuscript submitted to Phys. Rev. Accel. Beam

L’ambiente psichiatrico nell’opera di Franco Basaglia e Mario Tobino: verso un’ecologia delle idee (sulla follia)

The aim of the article is to compare the reform and the narration of the psychiatric environment in the work of Franco Basaglia and Mario Tobino from an ecological perspective. Both psychiatrists worked to reform the asylum spaces and the therapeutic relationships within it. Their actions and their narrations were both ecological but had an opposite ending. While Tobino defended until the end the idea of a safe psychiatric environment, protected by society, considered dangerous, Franco Basaglia strongly affirmed the repressiveness of the asylum space, the need to dismantle it and return the madness to society.The aim of the article is to compare the reform and the narration of the psychiatric environment in the work of Franco Basaglia and Mario Tobino from an ecological perspective. Both psychiatrists worked to reform the asylum spaces and the therapeutic relationships within it. Their actions and their narrations were both ecological but had an opposite ending. While Tobino defended until the end the idea of a safe psychiatric environment, protected by society, considered dangerous, Franco Basaglia strongly affirmed the repressiveness of the asylum space, the need to dismantle it and return the madness to society

Pisanie strachem: depresja, afazja, terapia w twórczości Simony Vinci

The purpose of this article is to show different literary representations of depression, fear and anxiety, as well as to analyze the therapeutic role of writing, in the literary work of Simona Vinci.Simona Vinci, classe 1970, è una delle voci letterarie italiane più significative dell’ultimo trentennio. Il suo esordio, nel 1997, con Dei bambini non si sa niente, vincitore nel 2000 del Premio Elsa Morante, viene accolto molto positivamente dal pubblico e dalla critica. La sua raccolta di racconti In tutti i sensi come l’amore (1999) ed il romanzo Come prima delle madri (2003) entrano nella cinquina finalista del Premio Campiello, che l’autrice si aggiudica nel 2016 con il romanzo, La prima verità.Artykuł ma na celu ukazanie różnych literackich obrazów depresji, strachu i lęku, a także analizę terapeutycznej roli pisania w twórczości literackiej Simony Vinci

Operational results with fast automatic beam-based LHC collimator alignment

The CERN Large Hadron Collider (LHC) is the largest and highest-energy particle accelerator ever built. It is designed to collide particles at a centre-of-mass energy of 14 TeV to explore the fundamental forces and constituents of matter. Due to the potentially destructive high-energy particle beams, with a total design energy of 362 MJ, the collider is equipped with a series of machine protection systems. The beam cleaning or collimation system is designed to passively intercept and absorb particles at large amplitudes. The cleaning efficiency depends heavily on the accurate positioning of the jaws with respect to the beam trajectory. Beam-based collimator alignment is currently the only feasible technique that can be used to determine the beam centre and beam size at the collimator locations. If the alignment is performed without any automation, it can require up to 30 hours to complete for all collimators. This reduces the beam time available for physics experiments. This article provides a brief recap of the algorithms and software developed to automate and speed up the alignment procedure, and presents the operational results achieved with fast automatic beam-based alignment in the 2011-2013 LHC runs.peer-reviewe

Conceptual design of hollow electron lenses for beam halo control in the Large Hadron Collider

Collimation with hollow electron beams is a technique for halo control in high-power hadron beams. It is based on an electron beam (possibly pulsed or modulated in intensity) guided by strong axial magnetic fields which overlaps with the circulating beam in a short section of the ring. The concept was tested experimentally at the Fermilab Tevatron collider using a hollow electron gun installed in one of the Tevatron electron lenses. Within the US LHC Accelerator Research Program (LARP) and the European FP7 HiLumi LHC Design Study, we are proposing a conceptual design for applying this technique to the Large Hadron Collider at CERN. A prototype hollow electron gun for the LHC was built and tested. The expected performance of the hollow electron beam collimator was based on Tevatron experiments and on numerical tracking simulations. Halo removal rates and enhancements of halo diffusivity were estimated as a function of beam and lattice parameters. Proton beam core lifetimes and emittance growth rates were checked to ensure that undesired effects were suppressed. Hardware specifications were based on the Tevatron devices and on preliminary engineering integration studies in the LHC machine. Required resources and a possible timeline were also outlined, together with a brief discussion of alternative halo-removal schemes and of other possible uses of electron lenses to improve the performance of the LHC.Comment: 24 pages, 1 table, 10 figure

Collimator settings generation, management and verification

Different collimator settings are required throughout the LHC operational cycle following the evolution of key beam parameters like energy, orbit and β-functions. Beam-based alignment is used to determine the beam centers and beam sizes at the collimators at discrete times in the cycle, such as injection, flat-top and collisions. These parameters are then used to generate setting functions for the collimator positions and interlock limits. An overview of the settings generation, management and verification cycle is presented, and potential error scenarios in the settings generation are identified. Improvements foreseen for the post LS1 operation are discussed. The present collimator status monitoring system is reviewed with suggestions for improvement. The role of MAD-X online is discussed. Finally, the results and current status towards maximizing the potential of the embedded-BPM collimators that will be installed in 18 collimator slots during LS1 is presented, including the tested automatic alignment procedure, software interlocks and orbit monitoring.peer-reviewe

Combined Ramp and Squeeze at the Large Hadron Collider

In the first two years of operation of the CERN Large Hadron Collider (LHC), the betatron squeeze has been carried out at constant flat top energy of 3.5 TeV. Squeeze setting functions are separated from the energy ramp functions. This ensured a maximum flexibility during commissioning because stopping at all intermediate optics for detailed measurements was possible. In order to then improve the efficiency of the operational cycle, combining the ramp and squeeze has been considered. In this paper, the various possibilities for this scheme are reviewed, and proposals of optimized operational cycles with combined ramp and squeeze are presented for different energies. Results of beam tests are also discussed

The Online Model for the Large Hadron Collider

The control of the high intensity beams of the CERN Large Hadron Collider is particular challenging and requires a good modeling of the machine. In recent years efforts were devoted to the design of a software infrastructure aimed at mimicking the behavior of the LHC. An online model of the machine, based on the accelerator design tool MAD-X, has been developed to support the commissioning and the operation of the LHC. This model is integrated into the Java-based LHC development framework and provides the full computing power of MAD-X, including the best knowledge of the machine aperture and magnetic models. In this paper, we present the status of the MAD-X online application and illustrate how it has been used during the LHC commissioning. Possible future implementations are also discussed

Operational results on the fully automatic LHC collimator alignment

The Large Hadron Collider has a complex collimation system installed to protect its sensitive equipment from normal and abnormal beam losses. The collimators are set around the beam following a multistage transverse setting hierarchy. The insertion position of each collimator is established using beam-based alignment techniques to determine the local beam position and rms beam size at each collimator. During previous years, collimator alignments were performed semiautomatically, with collimation experts present to oversee and control the alignment. During run II, a new fully automatic alignment tool was developed and used for collimator alignments throughout 2018. This paper discusses the improvements on the alignment software to automate it using machine learning, whilst focusing on the operational results obtained when testing the new software in the LHC. The alignment tests were conducted with both proton and ion beams, and angular alignments were performed with proton beams. This upgraded software successfully decreased the alignment time by a factor of 3 and made the results more reproducible, which is particularly important when performing angular alignments.peer-reviewe

Software architecture for automatic LHC collimator alignment using machine learning

The Large Hadron Collider at CERN relies on a collimation system to absorb unavoidable beam losses before they reach the superconducting magnets. The collimators are positioned close to the beam in a transverse setting hierarchy achieved by aligning each collimator with a precision of a few tens of micrometres. In previous years, collimator alignments were performed semi-automatically, requiring collimation experts to be present to oversee and control the entire process. In 2018, expert control of the alignment procedure was replaced by dedicated machine learning algorithms, and this new software was used for collimator alignments throughout the year. This paper gives an overview of the software re-design required to achieve fully automatic collimator alignments, describing in detail the software architecture and controls systems involved. Following this successful deployment, this software will be used in the future as the default alignment software for the LHC.peer-reviewe