CERN Accelerating science

Accelerator Physics

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2018-10-20
06:01
Electron cloud buildup driving spontaneous vertical instabilities of stored beams in the Large Hadron Collider / Romano, Annalisa (CERN ; Darmstadt, Tech. U.) ; Boine-Frankenheim, Oliver (Darmstadt, Tech. U.) ; Buffat, Xavier (CERN) ; Iadarola, Giovanni (CERN) ; Rumolo, Giovanni (CERN)
At the beginning of the 2016 run, an anomalous beam instability was systematically observed at the CERN Large Hadron Collider (LHC). Its main characteristic was that it spontaneously appeared after beams had been stored for several hours in collision at 6.5 TeV to provide data for the experiments, despite large chromaticity values and high strength of the Landau-damping octupole magnet. [...]
2018 - 9 p. - Published in : Phys. Rev. Accel. Beams 21 (2018) 061002 Fulltext: PDF;

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2018-10-19
06:47
Vlasov description of the effects of nonlinear chromaticity on transverse coherent beam instabilities / Schenk, M (CERN ; Ecole Polytechnique, Lausanne) ; Buffat, X (CERN) ; Li, K (CERN) ; Maillard, A (Ecole Normale Supérieure, Paris)
This paper extends the existing Vlasov theory for transverse coherent beam instabilities to account for nonlinear chromaticity. It confirms the hypothesis that nonlinear chromaticity has two effects on the beam dynamics: (i) it changes the effective impedance which results in a modification of the coherent frequencies of the head-tail modes, and (ii) it can introduce betatron detuning with longitudinal action and provide Landau damping of transverse modes. [...]
2018 - 14 p. - Published in : Phys. Rev. Accel. Beams 21 (2018) 084402 Fulltext: PDF;

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2018-10-19
06:47
Experimental stabilization of transverse collective instabilities in the LHC with second order chromaticity / Schenk, M (CERN ; Ecole Polytechnique, Lausanne) ; Buffat, X (CERN) ; Carver, L  R (CERN) ; De Maria, R (CERN) ; Li, K (CERN) ; Métral, E (CERN)
This paper discusses measurements on the stabilization of single bunches with second order chromaticity ($Q′′$) in the Large Hadron Collider (LHC) at CERN. $Q′′$ introduces an incoherent betatron tune spread which can produce Landau damping of transverse instabilities. [...]
2018 - 12 p. - Published in : Phys. Rev. Accel. Beams 21 (2018) 084401 Fulltext: PDF;

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2018-10-19
06:47
A low energy ion beamline for TwinEBIS / Pahl, H (CERN ; Heidelberg U.) ; Bencini, V (CERN ; INFN, Rome ; Rome U.) ; Breitenfeldt, M (CERN ; ADAM, Geneva) ; Granadeiro Costa, A R (CERN ; IST, Lisbon (main)) ; Pikin, A (CERN ; Brookhaven Natl. Lab.) ; Pitters, J (CERN) ; Wenander, F (CERN)
A low energy beamline has been designed for the TwinEBIS setup. The beamline will be used to transport ions extracted from the electron beam ion source into an accelerating radio frequency quadrupole or into secondary devices, like a time of flight-mass spectrometer, attached to the beamline via a fast three way 20° ion switchyard. [...]
2018 - 21 p. - Published in : JINST 13 (2018) P08012 Fulltext: pdf - PDF; 10.1088_1748-0221_13_08_P08012 - PDF;

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2018-10-18
09:02
Distributed Optical Fiber Radiation Sensing in the Proton Synchrotron Booster at CERN / Di Francesca, D (CERN) ; Toccafondo, I (CERN) ; Li Vecchi, G (CERN ; Lab. Hubert Curien, St. Etienne) ; Calderini, S (CERN) ; Girard, S (Lab. Hubert Curien, St. Etienne) ; Alessi, A (Lab. Hubert Curien, St. Etienne) ; Ferraro, R (CERN) ; Danzeca, S (CERN) ; Kadi, Y (CERN) ; Brugger, M (CERN)
In this paper, we report on the development and first deployment of a distributed optical fiber radiation sensor (DOFRS) for the online monitoring of radiation levels in the high-energy accelerator facilities of CERN. [...]
2018. - 6 p.

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2018-10-17
06:01
Cross-wake force and correlated head-tail instability in beam-beam collisions with a large crossing angle / Kuroo, Nami (KEK, Tsukuba ; Tsukuba U. (main)) ; Ohmi, Kazuhito (KEK, Tsukuba) ; Oide, Katsunobu (KEK, Tsukuba ; CERN) ; Zhou, Demin (KEK, Tsukuba ; CERN) ; Zimmermann, Frank (CERN)
This paper discusses novel coherent beam-beam instability in collisions with a large crossing angle. The instability appears in the correlated head-tail motion of two colliding beams. [...]
2018 - 15 p. - Published in : Phys. Rev. Accel. Beams 21 (2018) 031002 Fulltext: PDF;

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2018-10-17
06:01
Beam measurement of the high frequency impedance sources with long bunches in the CERN Super Proton Synchrotron / Lasheen, A (CERN ; Orsay) ; Argyropoulos, T (CERN) ; Bohl, T (CERN) ; Esteban Müller, J  F (CERN) ; Timko, H (CERN) ; Shaposhnikova, E (CERN)
Microwave instability in the Super Proton Synchrotron (SPS) at CERN is one of the main limitations to reach the requirements for the High Luminosity-LHC project (increased beam intensity by a factor 2). To identify the impedance source responsible of the instability, beam measurements were carried out to probe the SPS impedance. [...]
2018 - 13 p. - Published in : Phys. Rev. Accel. Beams 21 (2018) 034401 Fulltext: PDF;

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2018-10-17
06:01
Experimental Observation of “Shadowing” in Optical Transition Radiation / Kieffer, R (CERN) ; Bergamaschi, M (CERN ; Royal Holloway, U. of London) ; Bravin, E (CERN) ; Farabolini, W (CERN) ; Karataev, P (Royal Holloway, U. of London) ; Lefevre, T (CERN) ; Mazzoni, S (CERN)
We report the observation of shadowing between two optical transition radiation (OTR) sources from a 205 MeV electron beam. The total optical intensity is measured as a function of the distance $d$ between the sources, covering the range $0 \lt d \lt 4L_{\nu}$, where $L_{\nu}$ is the formation length of the particles. [...]
2018 - 5 p. - Published in : Phys. Rev. Lett. 120 (2018) 094802 Fulltext: PDF;

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2018-10-17
06:01
Development and validation of a multilateration test bench for particle accelerator pre-alignment / Kamugasa, Solomon William (CERN ; Zurich, ETH) ; Rothacher, Markus (Zurich, ETH) ; Gayde, Jean-Christophe (CERN) ; Mainaud Durand, Helene (CERN)
The development and validation of a portable coordinate measurement solution for fiducialization of compact linear collider (CLIC) components is presented. This new solution addresses two limitations of high-accuracy state-of-the-art coordinate measuring machines, i.e. [...]
2018 - 11 p. - Published in : Meas. Sci. Technol. 29 (2018) 034010

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2018-10-16
06:47
Quadrupole-free detector optics design for the Compact Linear Collider final focus system at 3 TeV / Plassard, Fabien (CERN) ; Latina, Andrea (CERN) ; Marin, Eduardo (CERN) ; Tomás, Rogelio (CERN) ; Bambade, Philip (Orsay, LAL)
Aiming to simplify the machine detector interface of the Compact Linear Collider (CLIC), a new detector model has been designed allowing the last quadrupole QD0 of the final focus system (FFS) to be located outside of the experiment with a distance L* from the interaction point of 6 m. In this paper, the beam delivery system (BDS) has been reoptimized, offering a luminosity performance that exceeds the design requirements by 11% for the total luminosity and by 7% in the energy peak. [...]
2018 - 13 p. - Published in : Phys. Rev. Accel. Beams 21 (2018) 011002 Fulltext: PDF;

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