HB2023 - Table of Session: TUA1I (Invited Presentations WG A)

Paper	Title	Page
TUA1I1	Inverse Stability Problem in Beam Dynamics
	A.V. Burov Fermilab, Batavia, Illinois, USA
	Funding: Fermilab is operated by Fermi Research Alliance, LLC under Contract No. DE-AC02-07CH11359 with the United States Department of Energy. Beam stability is conventionally described by means of the stability diagram, which is a threshold line in a complex plane of a particular intensity parameter, the coherent tune shift; the diagram separates stable and unstable states. The incoherent tune spread of the beam particles normally causes the transverse stability diagram to be an asymmetric bell-shaped curve above the real axis; for a given optical nonlinearity, the diagram is determined by the beam distribution function only. Recently, such a diagram was measured by means of an antidamper, see S. Antipov et al., Phys. Rev. Lett. 126, 164801 (2021). Such measurements open the door to a new method of beam diagnostics, finding the beam phase space density as a solution of an inverse stability problem. The main idea, methods of its implementation, possible obstacles and optimizations are discussed.
	Slides TUA1I1 [0.761 MB]
Cite •	reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

TUA1I2	New Understanding of Longitudinal Beam Instabilities and Comparison with Measurements	45
	I. Karpov CERN, Meyrin, Switzerland
	Beam instabilities driven by broad- and narrowband impedance sources have been treated separately so far. In this contribution, we present the generalised beam stability analysis based on the concept of van Kampen modes. In the presence of broadband impedance, the loss of Landau damping (LLD) in the longitudinal plane can occur above a certain single-bunch intensity. For significantly higher intensities, the broad-band impedance can drive violent radial or azimuthal mode-coupling instabilities. We have shown that the synchrotron frequency spread due to RF field non-linearity, counter-intuitively, reduces the single-bunch instability threshold. We have also demonstrated that a multi-bunch instability driven by a narrow-band impedance source can be significantly affected by LLD when adding broad-band impedance. These findings are supported by macroparticle simulations and beam observations in the Super Proton Synchrotron and the Large Hadron Collider at CERN.
	Slides TUA1I2 [1.517 MB]
DOI •	reference for this paper ※ doi:10.18429/JACoW-HB2023-TUA1I2
About •	Received ※ 01 October 2023 — Revised ※ 06 October 2023 — Accepted ※ 13 October 2023 — Issued ※ 13 October 2023
Cite •	reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

Paper

Title

Page

TUA1I1

Inverse Stability Problem in Beam Dynamics

A.V. Burov
Fermilab, Batavia, Illinois, USA

Funding: Fermilab is operated by Fermi Research Alliance, LLC under Contract No. DE-AC02-07CH11359 with the United States Department of Energy.
Beam stability is conventionally described by means of the stability diagram, which is a threshold line in a complex plane of a particular intensity parameter, the coherent tune shift; the diagram separates stable and unstable states. The incoherent tune spread of the beam particles normally causes the transverse stability diagram to be an asymmetric bell-shaped curve above the real axis; for a given optical nonlinearity, the diagram is determined by the beam distribution function only. Recently, such a diagram was measured by means of an antidamper, see S. Antipov et al., Phys. Rev. Lett. 126, 164801 (2021). Such measurements open the door to a new method of beam diagnostics, finding the beam phase space density as a solution of an inverse stability problem. The main idea, methods of its implementation, possible obstacles and optimizations are discussed.

Slides TUA1I1 [0.761 MB]

Cite •

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

TUA1I2

New Understanding of Longitudinal Beam Instabilities and Comparison with Measurements

45

I. Karpov
CERN, Meyrin, Switzerland

Beam instabilities driven by broad- and narrowband impedance sources have been treated separately so far. In this contribution, we present the generalised beam stability analysis based on the concept of van Kampen modes. In the presence of broadband impedance, the loss of Landau damping (LLD) in the longitudinal plane can occur above a certain single-bunch intensity. For significantly higher intensities, the broad-band impedance can drive violent radial or azimuthal mode-coupling instabilities. We have shown that the synchrotron frequency spread due to RF field non-linearity, counter-intuitively, reduces the single-bunch instability threshold. We have also demonstrated that a multi-bunch instability driven by a narrow-band impedance source can be significantly affected by LLD when adding broad-band impedance. These findings are supported by macroparticle simulations and beam observations in the Super Proton Synchrotron and the Large Hadron Collider at CERN.

Slides TUA1I2 [1.517 MB]

DOI •

reference for this paper ※ doi:10.18429/JACoW-HB2023-TUA1I2

About •

Received ※ 01 October 2023 — Revised ※ 06 October 2023 — Accepted ※ 13 October 2023 — Issued ※ 13 October 2023

Cite •

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