HB2023 - List of Keywords (octupole)

Paper	Title	Other Keywords	Page
THA1C1	High Intensity Beam Dynamics Challenges for HL-LHC	impedance, electron, cavity, luminosity	344
	N. Mounet, H. Bartosik, P. Baudrenghien, R. Bruce, X. Buffat, R. Calaga, R. De Maria, C.N. Droin, L. Giacomel, M. Giovannozzi, G. Iadarola, S. Kostoglou, B. Lindström, L. Mether, E. Métral, Y. Papaphilippou, K. Paraschou, S. Redaelli, G. Rumolo, B. Salvant, G. Sterbini, R. Tomás García CERN, Meyrin, Switzerland
	The High Luminosity (HL-LHC) project aims to increase the integrated luminosity of CERN’s Large Hadron Collider (LHC) by an order of magnitude compared to its initial design. This requires a large increase in bunch intensity and beam brightness compared to the first LHC runs, and hence poses serious collective-effects challenges, related in particular to electron cloud, instabilities from beam-coupling impedance, and beam-beam effects. Here we present the associated constraints and the proposed mitigation measures to achieve the baseline performance of the upgraded LHC machine. We also discuss the interplay of these mitigation measures with other aspects of the accelerator, such as the physical and dynamic aperture, machine protection, magnet imperfections, optics, and the collimation system.
	Slides THA1C1 [3.385 MB]
DOI •	reference for this paper ※ doi:10.18429/JACoW-HB2023-THA1C1
About •	Received ※ 01 October 2023 — Revised ※ 10 October 2023 — Accepted ※ 12 October 2023 — Issued ※ 15 October 2023
Cite •	reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

THC2I2	Extraction of LHC Beam Parameters from Schottky Signals	synchrotron, betatron, diagnostics, simulation	382
	K. Łasocha, D. Alves, C. Lannoy, N. Mounet CERN, Meyrin, Switzerland C. Lannoy, T. Pieloni EPFL, Lausanne, Switzerland
	Analysis of Schottky signals provides rich insights into the dynamics of a hadron beam, with well-established methods of deriving the betatron tune and machine chromaticity. In this contribution, we will report on recent developments in the analysis and understanding of the signals measured at the Large Hadron Collider during proton and Pb⁸²⁺ fills. A fitting-based technique, where the measured spectra are iteratively compared with theoretical predictions, will be presented and compared with the previous methods. As a step beyond the classical theory of Schottky spectra, certain signal modifications due to the activity of the LHC machine systems will be discussed from the perspective of the applicability of the modified signal to the beam diagnostics.
	Slides THC2I2 [9.053 MB]
DOI •	reference for this paper ※ doi:10.18429/JACoW-HB2023-THC2I2
About •	Received ※ 04 October 2023 — Revised ※ 08 October 2023 — Accepted ※ 09 October 2023 — Issued ※ 12 October 2023
Cite •	reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

THBP12	Slow vs Fast Landau Damping Threshold Measurement at the LHC and Implications for the HL-LHC	damping, experiment, simulation, emittance	470
	X. Buffat, L. Giacomel, N. Mounet CERN, Meyrin, Switzerland
	The mechanism of Loss of Landau Damping by Diffusion (L2D2) was observed in dedicated experiments at the LHC using a controlled external source of noise. Nevertheless, the predictions of stability threshold by L2D2 models are plagued by the poor knowledge of the natural noise floor affecting the LHC beams. Experimental measurements of the stability threshold on slow and fast time scales are used to better constrain the model. The improved model is then used to quantify requirements in terms of Landau damping for the HL-LHC.
DOI •	reference for this paper ※ doi:10.18429/JACoW-HB2023-THBP12
About •	Received ※ 29 September 2023 — Revised ※ 07 October 2023 — Accepted ※ 10 October 2023 — Issued ※ 30 October 2023
Cite •	reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

THBP15	Optimizing Resonance Driving Terms Using MAD-NG Parametric Maps	optics, resonance, injection, emittance	483
	L. Deniau, S. Kostoglou, E.H. Maclean, K. Paraschou, T.H.B. Persson, R. Tomás García CERN, Meyrin, Switzerland
	In 2023, a review of the LHC octupolar resonance driving terms at injection was carried out, motivated by two observations: (i) unwanted losses during the injection process with strongly powered octupoles and (ii) an expected reduction in emittance growth from e-cloud effects in simulations with weaker octupolar resonances. The MAD-NG code was used to simultaneously optimise the main octupolar resonances: 4Qx, 4Qy, and 2Qx-2Qy by adjusting 16 quadrupole families and 16 octupole families, for a total of 32 parameters. These knobs were introduced as parameters in the transfer map, allowing the Jacobian required by the optimiser to be calculated in a single pass, saving 32 additional optics evaluations and avoiding finite difference approximations. Constraints on tunes, amplitude detuning and optics around the machine were also considered as part of the optimisation process. This paper reviews the parametric optimisation with MAD-NG and compares the results with MADX-PTC.
	Poster THBP15 [0.938 MB]
DOI •	reference for this paper ※ doi:10.18429/JACoW-HB2023-THBP15
About •	Received ※ 02 October 2023 — Revised ※ 06 October 2023 — Accepted ※ 10 October 2023 — Issued ※ 17 October 2023
Cite •	reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

THBP20	Optics for Landau Damping with Minimized Octupolar Resonances in the LHC	optics, resonance, injection, focusing	503
	R. Tomás García, F.S. Carlier, L. Deniau, J. Dilly, J. Keintzel, S. Kostoglou, M. Le Garrec, E.H. Maclean, K. Paraschou, T.H.B. Persson, F. Soubelet, A. Wegscheider CERN, Meyrin, Switzerland
	Operation of the Large Hadron Collider (LHC) requires strong octupolar magnetic fields to suppress coherent beam instabilities. The amplitude detuning that is generated by these octupolar magnetic fields brings the tune of individual particles close to harmful resonances, which are mostly driven by the octupolar fields themselves. In 2023, new optics were deployed in the LHC at injection with optimized betatronic phase advances to minimize the resonances from the octupolar fields without affecting the amplitude detuning. This paper reports on the optics design, commissioning and the lifetime measurements performed to validate the optics.
DOI •	reference for this paper ※ doi:10.18429/JACoW-HB2023-THBP20
About •	Received ※ 01 October 2023 — Revised ※ 07 October 2023 — Accepted ※ 10 October 2023 — Issued ※ 23 October 2023
Cite •	reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

THBP21	Increasing High Luminosity LHC Dynamic Aperture Using Optics Optimizations	optics, luminosity, dynamic-aperture, resonance	507
	R. De Maria, Y. Angelis, C.N. Droin, S. Kostoglou, F. Plassard, G. Sterbini, R. Tomás García CERN, Meyrin, Switzerland
	Funding: Work supported by the HL-LHC project. CERN’s Large Hadron Collider (LHC) is expected to operate with unprecedented beam current and brightness from the beginning of Run 4 in 2029. In the context of the High Luminosity LHC project, the baseline operational scenarios are currently being developed. They require a large octupole current and a large chromaticity throughout the entire cycle, which drives a strong reduction of dynamic aperture, in particular at injection and during the luminosity production phase. Despite being highly constrained, the LHC optics and sextupole and octupole corrector circuits still offer a few degrees of freedom that can be used to reduce resonances and the extent of the tune footprint at constant Landau damping, thereby leading to an improvement of the dynamic aperture. This contribution presents the status of the analysis that will be used to prepare the optics baseline for LHC Run 4.
	Poster THBP21 [1.286 MB]
DOI •	reference for this paper ※ doi:10.18429/JACoW-HB2023-THBP21
About •	Received ※ 29 September 2023 — Revised ※ 06 October 2023 — Accepted ※ 10 October 2023 — Issued ※ 31 October 2023
Cite •	reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

THBP27	Experimental Investigation of Nonlinear Integrable Optics in a Paul Trap	lattice, resonance, experiment, space-charge	523
	J.A.D. Flowerdew University of Oxford, Oxford, United Kingdom D.J. Kelliher, S. Machida STFC/RAL/ISIS, Chilton, Didcot, Oxon, United Kingdom S.L. Sheehy STFC/RAL/ASTeC, Chilton, Didcot, Oxon, United Kingdom
	Funding: Work supported by Royal Society grants Octupoles are often used to damp beam instabilities caused by space charge. However, in general the insertion of octupole magnets leads to a nonintegrable lattice which reduces the area of stable particle motion. One proposed solution to this problem is Quasi-Integrable Optics (QIO), where the octupoles are inserted between a specially designed lattice called a T-insert. An octupole with a strength that scales as 1/β³(s) is applied in the drift region to create a time-independent octupole field, leading to a lattice with an invariant Hamiltonian. This means that large tune spreads can be achieved without reducing the dynamic aperture. IBEX is a Paul trap which confines low energy ions with an RF voltage, simulating the transverse dynamics of an alternating gradient accelerator. IBEX has recently undergone an upgrade to allow for octupole fields to be created in the trap in addition to quadrupole focusing. We present our first experimental results from testing QIO with the IBEX trap. jake.flowerdew@physics.ox.ac.uk
	Poster THBP27 [4.163 MB]
DOI •	reference for this paper ※ doi:10.18429/JACoW-HB2023-THBP27
About •	Received ※ 30 September 2023 — Revised ※ 09 October 2023 — Accepted ※ 10 October 2023 — Issued ※ 31 October 2023
Cite •	reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

Paper

Title

Other Keywords

Page

THA1C1

High Intensity Beam Dynamics Challenges for HL-LHC

impedance, electron, cavity, luminosity

344

N. Mounet, H. Bartosik, P. Baudrenghien, R. Bruce, X. Buffat, R. Calaga, R. De Maria, C.N. Droin, L. Giacomel, M. Giovannozzi, G. Iadarola, S. Kostoglou, B. Lindström, L. Mether, E. Métral, Y. Papaphilippou, K. Paraschou, S. Redaelli, G. Rumolo, B. Salvant, G. Sterbini, R. Tomás García
CERN, Meyrin, Switzerland

The High Luminosity (HL-LHC) project aims to increase the integrated luminosity of CERN’s Large Hadron Collider (LHC) by an order of magnitude compared to its initial design. This requires a large increase in bunch intensity and beam brightness compared to the first LHC runs, and hence poses serious collective-effects challenges, related in particular to electron cloud, instabilities from beam-coupling impedance, and beam-beam effects. Here we present the associated constraints and the proposed mitigation measures to achieve the baseline performance of the upgraded LHC machine. We also discuss the interplay of these mitigation measures with other aspects of the accelerator, such as the physical and dynamic aperture, machine protection, magnet imperfections, optics, and the collimation system.

Slides THA1C1 [3.385 MB]

DOI •

reference for this paper ※ doi:10.18429/JACoW-HB2023-THA1C1

About •

Received ※ 01 October 2023 — Revised ※ 10 October 2023 — Accepted ※ 12 October 2023 — Issued ※ 15 October 2023

Cite •

reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

THC2I2

Extraction of LHC Beam Parameters from Schottky Signals

synchrotron, betatron, diagnostics, simulation

382

K. Łasocha, D. Alves, C. Lannoy, N. Mounet
CERN, Meyrin, Switzerland
C. Lannoy, T. Pieloni
EPFL, Lausanne, Switzerland

Analysis of Schottky signals provides rich insights into the dynamics of a hadron beam, with well-established methods of deriving the betatron tune and machine chromaticity. In this contribution, we will report on recent developments in the analysis and understanding of the signals measured at the Large Hadron Collider during proton and Pb⁸²⁺ fills. A fitting-based technique, where the measured spectra are iteratively compared with theoretical predictions, will be presented and compared with the previous methods. As a step beyond the classical theory of Schottky spectra, certain signal modifications due to the activity of the LHC machine systems will be discussed from the perspective of the applicability of the modified signal to the beam diagnostics.

Slides THC2I2 [9.053 MB]

DOI •

reference for this paper ※ doi:10.18429/JACoW-HB2023-THC2I2

About •

Received ※ 04 October 2023 — Revised ※ 08 October 2023 — Accepted ※ 09 October 2023 — Issued ※ 12 October 2023

Cite •

reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

THBP12

Slow vs Fast Landau Damping Threshold Measurement at the LHC and Implications for the HL-LHC

damping, experiment, simulation, emittance

470

X. Buffat, L. Giacomel, N. Mounet
CERN, Meyrin, Switzerland

The mechanism of Loss of Landau Damping by Diffusion (L2D2) was observed in dedicated experiments at the LHC using a controlled external source of noise. Nevertheless, the predictions of stability threshold by L2D2 models are plagued by the poor knowledge of the natural noise floor affecting the LHC beams. Experimental measurements of the stability threshold on slow and fast time scales are used to better constrain the model. The improved model is then used to quantify requirements in terms of Landau damping for the HL-LHC.

DOI •

reference for this paper ※ doi:10.18429/JACoW-HB2023-THBP12

About •

Received ※ 29 September 2023 — Revised ※ 07 October 2023 — Accepted ※ 10 October 2023 — Issued ※ 30 October 2023

Cite •

reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

THBP15

Optimizing Resonance Driving Terms Using MAD-NG Parametric Maps

optics, resonance, injection, emittance

483

L. Deniau, S. Kostoglou, E.H. Maclean, K. Paraschou, T.H.B. Persson, R. Tomás García
CERN, Meyrin, Switzerland

In 2023, a review of the LHC octupolar resonance driving terms at injection was carried out, motivated by two observations: (i) unwanted losses during the injection process with strongly powered octupoles and (ii) an expected reduction in emittance growth from e-cloud effects in simulations with weaker octupolar resonances. The MAD-NG code was used to simultaneously optimise the main octupolar resonances: 4Qx, 4Qy, and 2Qx-2Qy by adjusting 16 quadrupole families and 16 octupole families, for a total of 32 parameters. These knobs were introduced as parameters in the transfer map, allowing the Jacobian required by the optimiser to be calculated in a single pass, saving 32 additional optics evaluations and avoiding finite difference approximations. Constraints on tunes, amplitude detuning and optics around the machine were also considered as part of the optimisation process. This paper reviews the parametric optimisation with MAD-NG and compares the results with MADX-PTC.

Poster THBP15 [0.938 MB]

DOI •

reference for this paper ※ doi:10.18429/JACoW-HB2023-THBP15

About •

Received ※ 02 October 2023 — Revised ※ 06 October 2023 — Accepted ※ 10 October 2023 — Issued ※ 17 October 2023

Cite •

reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

THBP20

Optics for Landau Damping with Minimized Octupolar Resonances in the LHC

optics, resonance, injection, focusing

503

R. Tomás García, F.S. Carlier, L. Deniau, J. Dilly, J. Keintzel, S. Kostoglou, M. Le Garrec, E.H. Maclean, K. Paraschou, T.H.B. Persson, F. Soubelet, A. Wegscheider
CERN, Meyrin, Switzerland

Operation of the Large Hadron Collider (LHC) requires strong octupolar magnetic fields to suppress coherent beam instabilities. The amplitude detuning that is generated by these octupolar magnetic fields brings the tune of individual particles close to harmful resonances, which are mostly driven by the octupolar fields themselves. In 2023, new optics were deployed in the LHC at injection with optimized betatronic phase advances to minimize the resonances from the octupolar fields without affecting the amplitude detuning. This paper reports on the optics design, commissioning and the lifetime measurements performed to validate the optics.

DOI •

reference for this paper ※ doi:10.18429/JACoW-HB2023-THBP20

About •

Received ※ 01 October 2023 — Revised ※ 07 October 2023 — Accepted ※ 10 October 2023 — Issued ※ 23 October 2023

Cite •

reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

THBP21

Increasing High Luminosity LHC Dynamic Aperture Using Optics Optimizations

optics, luminosity, dynamic-aperture, resonance

507

R. De Maria, Y. Angelis, C.N. Droin, S. Kostoglou, F. Plassard, G. Sterbini, R. Tomás García
CERN, Meyrin, Switzerland

Funding: Work supported by the HL-LHC project.
CERN’s Large Hadron Collider (LHC) is expected to operate with unprecedented beam current and brightness from the beginning of Run 4 in 2029. In the context of the High Luminosity LHC project, the baseline operational scenarios are currently being developed. They require a large octupole current and a large chromaticity throughout the entire cycle, which drives a strong reduction of dynamic aperture, in particular at injection and during the luminosity production phase. Despite being highly constrained, the LHC optics and sextupole and octupole corrector circuits still offer a few degrees of freedom that can be used to reduce resonances and the extent of the tune footprint at constant Landau damping, thereby leading to an improvement of the dynamic aperture. This contribution presents the status of the analysis that will be used to prepare the optics baseline for LHC Run 4.

Poster THBP21 [1.286 MB]

DOI •

reference for this paper ※ doi:10.18429/JACoW-HB2023-THBP21

About •

Received ※ 29 September 2023 — Revised ※ 06 October 2023 — Accepted ※ 10 October 2023 — Issued ※ 31 October 2023

Cite •

reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

THBP27

Experimental Investigation of Nonlinear Integrable Optics in a Paul Trap

lattice, resonance, experiment, space-charge

523

J.A.D. Flowerdew
University of Oxford, Oxford, United Kingdom
D.J. Kelliher, S. Machida
STFC/RAL/ISIS, Chilton, Didcot, Oxon, United Kingdom
S.L. Sheehy
STFC/RAL/ASTeC, Chilton, Didcot, Oxon, United Kingdom

Funding: Work supported by Royal Society grants
Octupoles are often used to damp beam instabilities caused by space charge. However, in general the insertion of octupole magnets leads to a nonintegrable lattice which reduces the area of stable particle motion. One proposed solution to this problem is Quasi-Integrable Optics (QIO), where the octupoles are inserted between a specially designed lattice called a T-insert. An octupole with a strength that scales as 1/β³(s) is applied in the drift region to create a time-independent octupole field, leading to a lattice with an invariant Hamiltonian. This means that large tune spreads can be achieved without reducing the dynamic aperture. IBEX is a Paul trap which confines low energy ions with an RF voltage, simulating the transverse dynamics of an alternating gradient accelerator. IBEX has recently undergone an upgrade to allow for octupole fields to be created in the trap in addition to quadrupole focusing. We present our first experimental results from testing QIO with the IBEX trap.
jake.flowerdew@physics.ox.ac.uk

Poster THBP27 [4.163 MB]

DOI •

reference for this paper ※ doi:10.18429/JACoW-HB2023-THBP27

About •

Received ※ 30 September 2023 — Revised ※ 09 October 2023 — Accepted ※ 10 October 2023 — Issued ※ 31 October 2023

Cite •

reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)