CERN Accelerating science

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2021-02-20
06:37
Incoherent electron cloud effects in the Large Hadron Collider / Paraschou, K (CERN ; Aristotle U., Thessaloniki) ; Iadarola, G (CERN)
During the operation of the Large Hadron Collider in 2018, the majority of physics data was collected with a beam energy of 6.5 TeV, a bunch spacing of 25 ns and with β-functions in the high luminosity interaction points equal to 30 cm. In this configuration, it was found through several experimental measurements that electron cloud induces a significant degradation of the beam lifetime. [...]
2020 - 7 p. - Published in : CERN Yellow Rep. Conf. Proc. 9 (2020) 249-255 Fulltext: PDF;
In : ICFA mini-Workshop on Mitigation of Coherent Beam Instabilities in Particle Accelerators (MCBI 2019), Zermatt, Switzerland, 23 - 27 Sep 2019, pp.249-255 (CERN-2020-009)

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2021-02-20
06:37
Destabilising effect of resistive transverse dampers / Métral, E (CERN)
A resistive transverse damper is needed for multi-bunch operation in a machine like the CERN LHC and it is very efficient as it considerably reduces the necessary amount of nonlinearities (from octupoles) needed to reach beam stability through Landau damping. However, a resistive transverse damper also destabilizes the single-bunch motion below the transverse mode coupling instability (TMCI) intensity threshold (for zero chromaticity), introducing a new kind of instability, which has been called “ISR instability” (for Imaginary tune Split and Repulsion). [...]
2020 - 6 p. - Published in : CERN Yellow Rep. Conf. Proc. 9 (2020) 221-226 Fulltext: PDF;
In : ICFA mini-Workshop on Mitigation of Coherent Beam Instabilities in Particle Accelerators (MCBI 2019), Zermatt, Switzerland, 23 - 27 Sep 2019, pp.221-226 (CERN-2020-009)

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2021-02-20
06:37
Impact of coherent and incoherent beam-beam effects on the beams stability / Buffat, Xavier (CERN)
Various coherent instability mechanisms involving colliding beams are described together with techniques for their mitigation. They are illustrated with some examples based mostly on the recent experience at the Large Hadron Collider..
2020 - 6 p. - Published in : CERN Yellow Rep. Conf. Proc. 9 (2020) 256-261 Fulltext: PDF;
In : ICFA mini-Workshop on Mitigation of Coherent Beam Instabilities in Particle Accelerators (MCBI 2019), Zermatt, Switzerland, 23 - 27 Sep 2019, pp.256-261 (CERN-2020-009)

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2021-02-20
06:37
Beam transfer function and stability diagram in the Large Hadron Collider / Tambasco, C (Ecole Polytechnique, Lausanne) ; Pieloni, T (Ecole Polytechnique, Lausanne) ; Buffat, X (CERN) ; Métral, E (CERN)
Predictions of transverse instability thresholds in the LHC are based on the computation of Landau damping by calculating the stability diagram (SD). However any modification of the tune spread and/or particle distribution modifies the expected Landau damping in the beams. [...]
2020 - 6 p. - Published in : CERN Yellow Rep. Conf. Proc. 9 (2020) 115-120 Fulltext: PDF;
In : ICFA mini-Workshop on Mitigation of Coherent Beam Instabilities in Particle Accelerators (MCBI 2019), Zermatt, Switzerland, 23 - 27 Sep 2019, pp.115-120 (CERN-2020-009)

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2021-02-18
06:11
Consequences of longitudinal coupled-bunch instability mitigation on power requirements during the HL-LHC filling / Karpov, I (CERN) ; Baudrenghien, P (CERN) ; Medrano, L E Medina (CERN) ; Timko, H (CERN)
During the filling of the Large Hadron Collider (LHC), it is desirable to keep the RF cavity voltage constant both in amplitude and phase to minimize the emittance blow-up and injection losses. To have a constant voltage and to minimize power consumption, a special beam-loading compensation scheme called half-detuning is used in the LHC, for which the cavity fundamental resonant frequency needs to be de-tuned from the RF frequency by an appropriate value. [...]
2020 - 6 p. - Published in : CERN Yellow Rep. Conf. Proc. 9 (2020) 312-317 Fulltext: PDF;
In : ICFA mini-Workshop on Mitigation of Coherent Beam Instabilities in Particle Accelerators (MCBI 2019), Zermatt, Switzerland, 23 - 27 Sep 2019, pp.312-317 (CERN-2020-009)

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2021-02-18
05:04
Damping rate limitations for transverse dampers in large hadron colliders / Lebedev, V.A. (Fermilab)
The paper focuses on two issues important for design and operation of bunch-by-bunch transverse damper in a very large hadron collider, where fast damping is required to suppress beam instabilities and noise induced emittance growth. The first issue is associated with kick variation along a bunch which affects the damping of head-tail modes. [...]
arXiv:2004.10249; FERMILAB-CONF-20-089-AD.- 2020-12-16 - 8 p. - Published in : CERN Yellow Rep. Conf. Proc. 9 (2020) 203-210 Fulltext: fulltext1792176 - PDF; fermilab-conf-20-089-ad - PDF; 2004.10249 - PDF; External link: Fermilab Library Server (fulltext available)
In : ICFA mini-Workshop on Mitigation of Coherent Beam Instabilities in Particle Accelerators (MCBI 2019), Zermatt, Switzerland, 23 - 27 Sep 2019, pp.203-210 (CERN-2020-009)

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2021-02-17
06:31
Active methods of suppressing longitudinal multi-bunch instabilities / Bertin, F (CERN) ; Damerau, H (CERN) ; Favia, G (CERN) ; Lasheen, A (CERN)
Longitudinal multi-bunch instabilities limit the beam intensity and quality reach of hadron synchrotrons. In case the impedance source driving the instability is well known, for example an RF cavity, active feedback can be set up locally to reduce its effect on the beam. [...]
2020 - 6 p. - Published in : CERN Yellow Rep. Conf. Proc. 9 (2020) 197 Fulltext: PDF;
In : ICFA mini-Workshop on Mitigation of Coherent Beam Instabilities in Particle Accelerators (MCBI 2019), Zermatt, Switzerland, 23 - 27 Sep 2019, pp.197 (CERN-2020-009)

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2021-02-17
06:31
Low-impedance beam screen design for future hadron colliders / Arsenyev, S (Saclay) ; Schulte, D (CERN)
In future hadron colliders with collision energies greater than the energy of the Large Hadron Collider (LHC), the beamscreen becomes an increasingly important source of beam coupling impedance. This may lead to coherent beam instabilities, especially in the transverse plane, and potentially a failure to reach the desired beam intensity. [...]
2020 - 4 p. - Published in : CERN Yellow Rep. Conf. Proc. 9 (2020) 175-178 Fulltext: PDF;
In : ICFA mini-Workshop on Mitigation of Coherent Beam Instabilities in Particle Accelerators (MCBI 2019), Zermatt, Switzerland, 23 - 27 Sep 2019, pp.175-178 (CERN-2020-009)

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2021-02-17
06:31
ADTOBSBOX to catch instabilities / Söderén, M E (CERN) ; Valuch, D (CERN)
During Long Shutdown 2 (2019–2020) the transverse observation system (ADTObsBox) in the LHC will undergo a substantial upgrade. The purpose of this upgrade is to allow for true low latency, online processing of the 16 data-streams of transverse bunch-by-bunch, turn-by-turn positional data provided by the beam position monitors in transverse feed-back system in the LHC (ADT). [...]
2020 - 2 p. - Published in : CERN Yellow Rep. Conf. Proc. 9 (2020) 154 Fulltext: PDF;
In : ICFA mini-Workshop on Mitigation of Coherent Beam Instabilities in Particle Accelerators (MCBI 2019), Zermatt, Switzerland, 23 - 27 Sep 2019, pp.154 (CERN-2020-009)

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2021-02-17
06:31
Transverse damper and stability diagram / Antipov, S A (CERN ; DESY) ; Amorim, D (CERN ; SOLEIL, Saint-Aubin) ; Biancacci, N (CERN) ; Buffat, X (CERN) ; Métral, E (CERN) ; Mounet, N (CERN) ; Oeftiger, A (CERN ; Darmstadt, GSI) ; Valuch, D (CERN)
We describe a proof-of-principle test to measure Landau damping in a hadron ring using a destabilizing transverse feedback acting as a controllable source of beam coupling impedance. The test was performed at the Large Hadron Collider and stability diagrams for a range of its Landau octupole strengths have been measured for its injection energy of 450 GeV. [...]
2020 - 9 p. - Published in : CERN Yellow Rep. Conf. Proc. 9 (2020) 121-129 Fulltext: PDF;
In : ICFA mini-Workshop on Mitigation of Coherent Beam Instabilities in Particle Accelerators (MCBI 2019), Zermatt, Switzerland, 23 - 27 Sep 2019, pp.121-129 (CERN-2020-009)

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