HB2023 - Table of Session: TUA1C (Contributed Presentations WG A)

Paper	Title	Page
TUA1C1	Major Longitudinal Impedance Sources in the J-PARC Main Ring	53
	A. Kobayashi KEK, Tokai, Ibaraki, Japan
	Beam intensity upgrade is ongoing at the J-PARC main ring. The beam instability is controlled by feedback systems in both longitudinal and transverse directions respectively. However, in recent years, microbunch structures have been observed during debunching, inducing electron cloud and transverse beam instability, which has become a problem. It is essential to identify the cause and take countermeasures. A summary of model and measurement comparisons will be reported for the major impedances RF-cavities, FX-septa, and FX-kickers. Of the five septa, two have been subjected to impedance reduction measures. The remaining three septa are of different types, but similar measures are planning.
	Slides TUA1C1 [26.758 MB]
DOI •	reference for this paper ※ doi:10.18429/JACoW-HB2023-TUA1C1
About •	Received ※ 29 September 2023 — Revised ※ 06 October 2023 — Accepted ※ 11 October 2023 — Issued ※ 18 October 2023
Cite •	reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

TUA1C2	Coherent Dispersion Effects in 2-D Coasting Beams and 3-D Bunched Beams in High-Intensity Hadron Synchrotrons
	Y.S. Yuan IHEP, Beijing, People’s Republic of China G. Franchetti GSI, Darmstadt, Germany
	Both space charge and dispersion have an effect on high intensity beams in circular accelerators or transport sections with bending magnets, and may lead to emittance growth or even beam loss. In this work we study the combined effect of dispersion and space charge on both 2-D and 3-D high-intensity beams. Based on 2-D envelope equations extended by dispersion, and particle-in-cell simulations, we investigate the mismatched oscillation and coherent instabilities in an rms self-consistent manner. Main characteristics of the space-charge modified dispersion are discussed. It is found that the parametric and confluent resonances in 90 deg envelope insatiability can be separated because of dispersion. The recently-discovered 120 deg dispersion instability is also detailed discussed. For 3-D bunched beams, a splitting effect on dispersion mode and side bands of envelope modes due to synchrotron motion are presented. The mechanism of the splitting effect on the dispersion mode with space charge is analyzed. Moreover, the 120 deg dispersion instability in the 3-D bunched beam are presented with a discussion on possible methods for measuring the dispersion mode in hadron synchrotrons.
	Slides TUA1C2 [1.499 MB]
Cite •	reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

Paper

Title

Page

Major Longitudinal Impedance Sources in the J-PARC Main Ring

53

A. Kobayashi
KEK, Tokai, Ibaraki, Japan

Beam intensity upgrade is ongoing at the J-PARC main ring. The beam instability is controlled by feedback systems in both longitudinal and transverse directions respectively. However, in recent years, microbunch structures have been observed during debunching, inducing electron cloud and transverse beam instability, which has become a problem. It is essential to identify the cause and take countermeasures. A summary of model and measurement comparisons will be reported for the major impedances RF-cavities, FX-septa, and FX-kickers. Of the five septa, two have been subjected to impedance reduction measures. The remaining three septa are of different types, but similar measures are planning.

Slides TUA1C1 [26.758 MB]

DOI •

reference for this paper ※ doi:10.18429/JACoW-HB2023-TUA1C1

About •

Received ※ 29 September 2023 — Revised ※ 06 October 2023 — Accepted ※ 11 October 2023 — Issued ※ 18 October 2023

Cite •

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

TUA1C2

Coherent Dispersion Effects in 2-D Coasting Beams and 3-D Bunched Beams in High-Intensity Hadron Synchrotrons

Y.S. Yuan
IHEP, Beijing, People’s Republic of China
G. Franchetti
GSI, Darmstadt, Germany

Both space charge and dispersion have an effect on high intensity beams in circular accelerators or transport sections with bending magnets, and may lead to emittance growth or even beam loss. In this work we study the combined effect of dispersion and space charge on both 2-D and 3-D high-intensity beams. Based on 2-D envelope equations extended by dispersion, and particle-in-cell simulations, we investigate the mismatched oscillation and coherent instabilities in an rms self-consistent manner. Main characteristics of the space-charge modified dispersion are discussed. It is found that the parametric and confluent resonances in 90 deg envelope insatiability can be separated because of dispersion. The recently-discovered 120 deg dispersion instability is also detailed discussed. For 3-D bunched beams, a splitting effect on dispersion mode and side bands of envelope modes due to synchrotron motion are presented. The mechanism of the splitting effect on the dispersion mode with space charge is analyzed. Moreover, the 120 deg dispersion instability in the 3-D bunched beam are presented with a discussion on possible methods for measuring the dispersion mode in hadron synchrotrons.

Slides TUA1C2 [1.499 MB]

Cite •

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