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Articles by Salvachua Ferrando
CERN Document Server
Title Reducing Beam-Related Background on Forward Physics Detectors Using Crystal Collimation at the Large Hadron Collider Author(s) Mirarchi, D (Manchester U. ; CERN) ; Avati, V (AGH-UST, Cracow ; CERN) ; Bruce, R (CERN) ; Butcher, M (CERN) ; D'Andrea, M (CERN ; U. Padua (main)) ; Di Castro, M (CERN) ; Deile, M (CERN) ; Dziedzic, B (Cracow, INP) ; Hiller, K (DESY) ; Jakobsen, S (CERN) ; Kašpar, J (Prague, Inst. Phys.
Accelerators
Title Accelerators Video Download Embed Viewed by 2 users Author(s) Salvachua Ferrando, Belen Maria (speaker) (CERN) Corporate author(s) CERN. Geneva Imprint 2019-09-02. - Streaming video. Series (Hadron Collider Physics) (2019 CERN-Fermilab HCP Summer School) Lecture note on 2019-09-02T10:30:00 Subject category Hadron Collider Physics Copyright/License © 2019 CERN Submitted by patricia.mage@cern.ch Record created 2019-09-03, last modified 2019-09-03
Accelerators
Title Accelerators Video Download Embed Viewed by 11 users Author(s) Salvachua Ferrando, Belen Maria (speaker) (CERN) Corporate author(s) CERN. Geneva Imprint 2019-08-31. - Streaming video. Series (Hadron Collider Physics) (2019 CERN-Fermilab HCP Summer School) Lecture note on 2019-08-31T15:30:00 Subject category Hadron Collider Physics Copyright/License © 2019 CERN Submitted by patricia.mage@cern.ch Record created 2019-09-02, last modified 2019-09-02
MD3344 - Fully-Automatic Angular Alignment of LHC Collimators using Machine Learning
Report number CERN-ACC-NOTE-2018-0083 Title MD3344 - Fully-Automatic Angular Alignment of LHC Collimators using Machine Learning Download Embed Viewed by 23 users Author(s) Azzopardi, Gabriella (University of Malta (MT)) ; Valentino, Gianluca (University of Malta (MT)) ; Salvachua Ferrando, Belen Maria (CERN) Corporate author(s) CERN. Geneva. ATS Department Imprint 27 Oct 2018. - 10 p.
MD1653 - Part 1: Characterisation of BLM Response at Collimators
Internal Note Report number CERN-ACC-NOTE-2018-0070 Title MD1653 - Part 1: Characterisation of BLM Response at Collimators Author(s) Azzopardi, Gabriella (University of Malta (MT)) ; Valentino, Gianluca (University of Malta (MT)) ; Salvachua Ferrando, Belen Maria (CERN) Corporate author(s) CERN. Geneva. ATS Department Imprint 16 Jun 2018. - 8 p.
MD3343 - Fully-Automatic Parallel Collimation Alignment using Machine Learning
Internal Note Report number CERN-ACC-NOTE-2018-0071 Title MD3343 - Fully-Automatic Parallel Collimation Alignment using Machine Learning Author(s) Azzopardi, Gabriella (University of Malta (MT)) ; Valentino, Gianluca (University of Malta (MT)) ; Salvachua Ferrando, Belen Maria (CERN) Corporate author(s) CERN. Geneva. ATS Department Imprint 13 Sep 2018. - 8 p.
Spike Pattern Recognition for Automatic Collimation Alignment
The LHC makes use of a collimation system to protect its sensitive equipment by intercepting potentially dangerous beam halo particles. The appropriate collimator settings to protect the machine against beam losses relies on a very precise alignment of all the collimators with respect to the beam. The beam center at each collimator is then found by touching the beam halo using an alignment procedure.
Single bunch stability threshold with at orbit (MD2870)
Internal Note Report number CERN-ACC-NOTE-2018-0012 Title Single bunch stability threshold with at orbit (MD2870) Author(s) Buffat, Xavier (CERN) ; Amorim, David (Centre National de la Recherche Scientifique (FR)) ; Antipov, Sergey (CERN) ; Barraud, Laurent (Centre National de la Recherche Scientifique (FR)) ; Biancacci, Nicolo (CERN) ; Mazzacano, Giacomo (Centre National de la Recherche Scientifique (FR)) ; Mereghetti, Alessio (CERN) ; Metral, Elias (CERN) ; Salvachua Ferrando, Belen Maria...
Effect of a resonant excitation on the evolution of the beam emittance and halo population
Collimation with hollow electron beams or lenses (HEL) is currently one of the most promising concepts for active halo control in HL-LHC. In previous studies it has been shown that the halo can be efficiently removed with a hollow electron lens. Equally important as an efficient removal of the halo, is to demonstrate that the core stays unperturbed. In the case of an ideal hollow electron lens without bends, the field at the location of the beam core vanishes and the core thus remains unperturbed.
Automatic Angular alignment of LHC Collimators
The LHC is equipped with a complex collimation system to protect sensitive equipment from unavoidable beam losses. Collimators are positioned close to the beam using an alignment procedure. Until now they have always been aligned assuming no tilt between the collimator and the beam, however, tank misalignments or beam envelope angles at large-divergence locations could introduce a tilt limiting the collimation performance.
Limitations due to strong head-on beam-beam interactions (MD 1434)
Internal Note Report number CERN-ACC-NOTE-2017-0044 Title Limitations due to strong head-on beam-beam interactions (MD 1434) Author(s) Buffat, Xavier (CERN) ; Furuseth, Sondre Vik ; Iadarola, Giovanni (CERN) ; Papadopoulou, Parthena Stefania (University of Crete (GR)) ; Papaphilippou, Yannis (CERN) ; Pellegrini, Dario (CERN) ; Pojer, Mirko (CERN) ; Crockford, Guy (CERN) ; Salvachua Ferrando, Belen Maria (CERN) ; Trad, Georges (CERN) ; Barranco Garcia, Javier (Ecole Polytechnique Federale de...
FESA class for off-momentum lossmaps and decomposition of beam losses at LHC
The project consisted of two main parts. The first part was to build a FESA class which would serve as lossmap feedback controller for off-momentum lossmaps, capable of handling 100 Hz BLM data, contrary to existing controller. Thanks to the efficient management RF frequency, beam dumps during this procedure would be avoided and machine availability would improve by shortening the duration of machine validation after technical stops.
MD 1407 - Landau Damping: Beam Transfer Functions and diffusion mechanisms
In the 2012, 2015 and 2016 run several instabilities were developing at flat-top, during and at the end of the betatron squeeze where beam-beam interactions are present. The tune spread in the beams is therefore modified by the beam-beam long-range interactions and by other sources of spread. Studies of the stability area computed by evaluating the dispersion integral for different tune spreads couldn’t explain the observed instabilities during the squeeze and stable beams.
MD 1856 - Landau Damping: Beam Transfer Functions and diffusion mechanisms
In the 2012, 2015 and 2016 several instabilities were developing during the betatron squeeze where beam-beam interactions become stronger modifying the tune spread provided by the octupoles magnets. Studies of the stability area computed by evaluating the dispersion integral for different tune spread couldn’t explain the 2012 observed instabilities during the squeeze.
MD1878: Operation with primary collimators at tighter settings
Primary (TCP) collimators of the betatron cleaning insertion determine the betatron cut of the LHC beam. During the 2016 they were set at 5.5 nominal beam sigmas at 6.5 TeV (i.e. by using a normalized emittance " = 3:5 m is used). Reducing their settings is a possible way to push the at the LHC, which depends on the collimation hierarchy. This study aims at understanding possible limitations of operating the LHC with tighter settings of the primary collimators.
MD1878: Operation with primary collimators at tighter settings
Primary (TCP) collimators of the betatron cleaning insertion determine the betatron cut of the LHC beam. During the 2016 they were set at 5.5 nominal beam sigmas at 6.5 TeV (i.e. by using a normalized emittance ?* = 3:5 ?m is used). Reducing their settings is a possible way to push the ß* at the LHC, which depends on the collimation hierarchy. This study aims at understanding possible limitations of operating the LHC with tighter settings of the primary collimators.
Measured and simulated heavy-ion beam loss patterns at the CERN Large Hadron Collider
The Large Hadron Collider (LHC) at CERN pushes forward to new regimes in terms of beam energy and intensity. In view of the combination of very energetic and intense beams together with sensitive machine components, in particular the superconducting magnets, the LHC is equipped with a collimation system to provide protection and intercept uncontrolled beam losses. Beam losses could cause a superconducting magnet to quench, or in the worst case, damage the hardware.
Luminosity Anti-leveling with Crossing Angle (MD 1669)
A significant fraction of the LHC luminosity ($\sim$30\% in 2016) is lost due to the presence (and necessity) of the crossing angles at the IPs. At the LHC the crossing angle is typically set to a value that provides sufficient separation of the beams at the start of fills for the peak bunch intensities. As the bunch intensity decays during a fill, it is possible to reduce the crossing angle and recover some luminosity.
CERN Document Server
For the High Luminosity upgrade the β* in IR1 and IR5 will be further reduced compared to the current LHC. As the β* decreases the β-functions in the inner triplet (IT) increase resulting in a higher sensitivity of the HL-LHC to ground motion in the IT region or to increases of the low frequency noise. Noise can in general lead to emittance growth and higher halo population and diffusion rate.
CERN Document Server
HL-LHC will rely on very large beam-beam head-on shift and spread. Also LHC to push for higher luminosity will go in the same direction. A clear understanding of colling high brightness beams is fundamental to guarantee the operation of such beams and to anticipate problematics linked to such configuration. We want to explore the beam dynamics of colliding beams with high brightness: intensities as high as possible close to 2e11 ppb or higher and small emittances.
CERN Document Server
Internal Note Report number CERN-ACC-NOTE-2016-0020 Title MD 400: LHC emittance growth in presence of an external source of noise during collision Author(s) Barranco Garcia, Javier (Ecole Polytechnique Federale de Lausanne (CH)) ; Buffat, Xavier (CERN) ; Pieloni, Tatiana (CERN) ; Tambasco, Claudia (Ecole Polytechnique Federale de Lausanne (CH)) ; Qiang, Ji (3Lawrence Berkeley National Laboratory) ; Trad, Georges (CERN) ; Valuch, Daniel (CERN) ; Betz, Michael (CERN) ; Wendt, Manfred (CERN) ;...
CERN Document Server
Colliding the beams during the squeeze to profit from Landau damping due to head--on beam-beam and beta--star leveling are two operational modes that may have to be used in a not so distant future at the LHC. This MD aimed at improving the orbit control during the squeeze with much improved handling of orbit feedback references and at evaluating instruments and techniques to maintain the beam in collisions with active feedback on luminosity or beam position.
CERN Document Server
Identifying the minimum crossing angle achievable in the LHC is a key parameter to identify the collider luminosity reach. In this note, we summarise the observations collected during a dedicated experiment performed in 2015, where the strength of the long range beam-beam interaction is varied by reducing the crossing angle at IP1 and IP5. The crossing angle and the impact of the long range beam-beam interaction is analysed with respect to the beam and luminosity lifetimes.
CERN Document Server
Internal Note Report number CERN-ACC-NOTE-2016-0009 Title Active halo control through narrow-band excitation with the ADT Author(s) Wagner, Joschka (Johann-Wolfgang-Goethe Univ.
CERN Document Server
Beam halo measurements at 6.5 TeV in the LHC were conducted via collimator scrapings in an MD carried out on the 4th November 2015. From the time evolution of the beam losses in a collimator scan, it is possible to extract information on the halo diffusion and population. Six scans were performed with two collimators in the vertical and horizontal planes in B1 and B2 respectively.
CERN Document Server
This report summarises the results of the MD314 about the hierarchy limit of the IR7 collimation system and its impedance. While the activity, the procedures and the results concerning the collimator hierarchy limit are detailed here, the main outcomes from the impedance studies are only briefly reported, as a detailed MD report has been prepared. The MD was carried out during MD block II of 2015, on 29th August, at 6.5 TeV.
CERN Document Server
Internal Note Report number CERN-ACC-NOTE-2015-0043 Title Collide and Squeeze MD Author(s) Gorzawski, Arkadiusz (Ecole Polytechnique Federale de Lausanne (CH)) ; Mirarchi, Daniele (CERN) ; Papotti, Giulia (CERN) ; Salvachua Ferrando, Belen Maria (CERN) ; Wenninger, Jorg (CERN) Corporate author(s) CERN. Geneva.
CERN Document Server
This note summarizes MD 307, performed on August 27 2015, during which we measured with beam the global apertures at 6.5 TeV with IR1 and IR5 squeezed to β* =40 cm and a half crossing angle of 205 rad. The measurement technique involved opening collimators in steps, while inducing beam losses at each step, until the main loss location moved from the collimators to the global bottleneck in one of the triplets.
CERN Document Server
MD 310 was carried out on August 28 2015, in order to investigate the collimation performance using nominal optics with B*=40 cm, 2 o retraction collimator settings in IR7, and the very tight TCT settings which are necessary to protect the small normalized aperture. With these tight settings, we expect higher losses on the TCTs which should cause also higher beam-halo background at the experiments.
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