SAP2023 - List of Keywords (impedance)

Paper	Title	Other Keywords	Page
MOCXA02	Beam-Beam Interaction with Longitudinal Impedance and Its Application in TMCI Study	coupling, synchrotron, simulation, electron	1
	C.T. Lin IASF, Shenzhen, Guangdong, People’s Republic of China K. Ohmi KEK, Ibaraki, Japan Y. Zhang IHEP, Beijing, People’s Republic of China
	Simulations have showed a novel coherent head-tail instability induced by beam-beam interaction with a large Piwinski angle. The localized cross-wake force has been introduced to explain the instability. The longitudinal impedance would cause coherent and incoherent synchrotron tune shift and distort the particle¿s trajectories in longitudinal phase space. Further beam-beam simulation revealed that the longitudinal impedance has strong impacts on the beam stability, squeezing the horizontal stable tune area seriously. The instability has become an important issue during the designs of CEPC and FCC-ee. In this paper, we develop a transverse mode coupling analysis method that could be used to study beam-beam instability with and without longitudinal impedance. This method can also be applied in synchrotron light sources to study transverse mode coupling instability (TMCI) with longitudinal impedance and harmonic cavity. Some preliminary results at Shenzhen Innovation Light Source (SILF) are also shown.
DOI •	reference for this paper ※ doi:10.18429/JACoW-SAP2023-MOCXA02
About •	Received ※ 30 June 2023 — Accepted ※ 11 July 2023 — Issued ※ 23 September 2024
Cite •	reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

MOPB004	Lowest Longitudinal and Transverse Resistive-wall Wake and Impedance for Nonultra-relativistic Beams	wakefield, dipole, electron, space-charge	21
	J.Z. Tang TUB, Beijing, People’s Republic of China
	With the development of the steady-state microbunch(SSMB) storage ring, its parameters reveal that the ultra-relativistic assumption which is wildly used is not valid for the electron beam bunch train. For a bunch train with a length in the 100nm range, spacing of 1um, and energy in the hundred MeV range, the action angle of the space charge force is estimated by {r/γ}. The space charge effect of the mirror current loop formed in the wall with a scale of 1cm will have a sustained effect on approximately dozens of microbunches behind the source particle. The strength of the interaction between such bunches and the potential instability it may cause needs careful evaluation. At the same time, the effect of the space charge inside a single bunch due to space charge effect also needs to be considered. We reorganized the lowest-order longitudinal wakefield under non-extreme relativistic conditions, and modified the inconsistent part in the theoretical derivation in some essays of the lowest-order transverse wakefield. We present the modified theoretical results and analysis. The action area are then divided into three parts. It lays foundation in future research.
	Poster MOPB004 [1.278 MB]
DOI •	reference for this paper ※ doi:10.18429/JACoW-SAP2023-MOPB004
About •	Received ※ 30 June 2023 — Revised ※ 08 July 2023 — Accepted ※ 11 July 2023 — Issued ※ 22 November 2023
Cite •	reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

MOPB010	Impact of NEG Coating Thickness and Resistivity on Beam Coupling Impedance	vacuum, ECR, storage-ring, coupling	30
	T.L. He, Z.H. Bai, W.W. Li, H. Xu USTC/NSRL, Hefei, Anhui, People’s Republic of China
	In diffraction-limited storage rings, non-evaporable getter (NEG) coatings are generally used to assure the ultrahigh vacuum, which, however, also increase the beam coupling impedance that can affect beam dynamics. Ignoring the influence of coating roughness, the impact of NEG coatings on the impedance mainly depends on the coating thickness and resistivity. In this paper, we investigate the impedance characteristics of a round CuCrZr vacuum chamber coated by NEG with different thickness and resistivity.
DOI •	reference for this paper ※ doi:10.18429/JACoW-SAP2023-MOPB010
About •	Received ※ 29 June 2023 — Accepted ※ 11 July 2023 — Issued ※ 12 August 2024
Cite •	reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

MOPB014	Development of a Vlasov Solver for Arbitrary Sub-optimal Lengthening Conditions in Double-RF System	synchrotron, coupling, betatron, cavity	34
	J.Y. Xu, N. Wang, H.S. Xu, Y. Zhang IHEP, Beijing, People’s Republic of China C.T. Lin IASF, Shenzhen, Guangdong, People’s Republic of China
	Solving Vlasov equation is a classic method for analyzing collective beam instabilities. Considering longitudinal impedance and the nonlinear longitudinal potential well, we developed a new Vlasov solver which can be used to study the transverse mode-coupling instability under the arbitrary sub-optimal lengthening and the optimal lengthening conditions in a double-RF system. Several different techniques to deal with the radial direction of longitudinal phase space have been tested. Numerical discretization method is selected in this paper. The development of the solver is presented in details here. Benchmarks and crosscheck of the solver have been made and presented as well.
DOI •	reference for this paper ※ doi:10.18429/JACoW-SAP2023-MOPB014
About •	Received ※ 30 June 2023 — Revised ※ 08 July 2023 — Accepted ※ 11 July 2023 — Issued ※ 21 August 2024
Cite •	reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

MOPB018	Longitudinal Beam Dynamics Design for Super Tau-Charm Facility	luminosity, collective-effects, damping, synchrotron	45
	L.H. Zhang, J.Y. Tang USTC/SNST, Hefei, Anhui, People’s Republic of China S.Y. Li, T. Liu, Q. Luo USTC/NSRL, Hefei, Anhui, People’s Republic of China
	The project of Super Tau-Charm Facility (STCF) pro-posed in China, as a new-generation high-luminosity e⁺/e⁻ collider in the low-energy region with the center-of-mass energy of 2¿7 GeV, is well underway. The luminosity is targeted at 1.0×10³⁵ cm^-2s⁻¹ at the optimized beam energy of 2 GeV. Longitudinal beam dynamics becomes of great importance for the STCF due to the constraints from the novel beam-beam effect called coherent X-Z instability and severe beam collective effects. In this paper, we will develop an iterative optimization model for the STCF longitudinal beam dynamics design, which takes into account the influence of transverse dynamics, coherent X-Z instability, and collective effects.
DOI •	reference for this paper ※ doi:10.18429/JACoW-SAP2023-MOPB018
About •	Received ※ 30 June 2023 — Accepted ※ 11 July 2023 — Issued ※ 01 November 2023
Cite •	reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

MOPB028	Investigation on the Trapped Modes of CPMU at HEPS	damping, synchrotron, simulation, wakefield	62
	S. Yue, J.T. Li, S.K. Tian, N. Wang IHEP, Beijing, People’s Republic of China
	The Cryogenic Permanent Magnet Undulator (CPMU) is a crucial component in synchrotron radiation sources. Due to the small magnet gap of CPMU, the interaction between the beam and its surroundings is strong, which can result in a significant contribution to coupling impedance. In this work, the influence of CPMU on coupling impedance was investigated using wakefield and eigenmode solvers. The results indicated that some of the transverse impedance resonances in CPMU were much stronger than the impedance threshold determined by synchrotron radiation damping, which could cause vertical beam instability. To address this issue, different types of damping materials were investigated through simulations to suppress the resonances.
DOI •	reference for this paper ※ doi:10.18429/JACoW-SAP2023-MOPB028
About •	Received ※ 10 July 2023 — Revised ※ 11 July 2023 — Accepted ※ 12 July 2023 — Issued ※ 01 October 2023
Cite •	reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

TUPB029	Wakefield Studies for the Step Structure and the Skin Depth of Coated Dielectric Tubes	wakefield, electron, FEL, simulation	147
	H. Liu SINAP, Shanghai, People’s Republic of China S. Chen, H.X. Deng, B. Liu, Y.M. Wen SARI-CAS, Pudong, Shanghai, People’s Republic of China J.J. Guo Zhangjiang Lab, Shanghai, People’s Republic of China
	Funding: This work was supported by YSBR-042, 12125508, 11935020, 21XD1404100 and JCYJ-SHFY-2021-010. Wakefield issues are always important research objects in free electron laser (FEL) facilities. Since the wakefield in free electron laser facilities usually leads to a decrease of FEL performance, the research of the wakefield impacts is of great significance. Step structures are almost ubiquitous in the overall undulator section of an FEL facility, which always generate critical wakefields. In this paper, we systematically analyze and summarize the wakefield characteristics of step structures including the step-in structure and the step-out structure. In addition, the skin depth issue of the wakefield is still controversial. We study the skin depth of the wakefield field in the vacuum chamber of the kicker in the SHINE, which is made of the dielectric pipe. We proposed the conception of ¿effective skin depth¿ from two different perspectives and wrote simulation codes to calculate the ¿effective skin depth¿. We hope these methods could provide new mentalities for related research in the future.
	Poster TUPB029 [0.392 MB]
DOI •	reference for this paper ※ doi:10.18429/JACoW-SAP2023-TUPB029
About •	Received ※ 30 June 2023 — Revised ※ 09 July 2023 — Accepted ※ 12 July 2023 — Issued ※ 21 September 2023
Cite •	reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

TUPB033	Heating Estimation of Undulator Vacuum Chamber at S3FEL	electron, wakefield, vacuum, undulator	151
	H. Yi IASF, Shenzhen, Guangdong, People’s Republic of China X.F. Wang Institute of Advanced Science Facilities, Shenzhen, People’s Republic of China X.M. Yang, W.Q. Zhang DICP, Dalian, Liaoning, People’s Republic of China
	Heating of the vacuum chambers are unavoidable when electron beams pass through the chamber channels at relativistic speeds. In the undulator vacuum chambers, such effects might lead to temperature increase of the magnets and eventually cause degradations in the FEL lasing process. Thus, in this paper, the heating of the undulator vacuum chambers at S3FEL due to wake field effects and spontaneous synchrotron radiation are estimated using an analytical approach. For the wake field effects, the contribution from finite conductivity of the vacuum chamber material and from the inner surface roughness are considered. A electron beam profile from a start-to-end simulation is used to calculate the total wake field and the induced heat. For the synchrotron radiation, a simple analytical expression is used.
DOI •	reference for this paper ※ doi:10.18429/JACoW-SAP2023-TUPB033
About •	Received ※ 05 July 2023 — Revised ※ 09 July 2023 — Accepted ※ 12 July 2023 — Issued ※ 26 September 2024
Cite •	reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

Paper

Title

Other Keywords

Page

MOCXA02

Beam-Beam Interaction with Longitudinal Impedance and Its Application in TMCI Study

coupling, synchrotron, simulation, electron

1

C.T. Lin
IASF, Shenzhen, Guangdong, People’s Republic of China
K. Ohmi
KEK, Ibaraki, Japan
Y. Zhang
IHEP, Beijing, People’s Republic of China

Simulations have showed a novel coherent head-tail instability induced by beam-beam interaction with a large Piwinski angle. The localized cross-wake force has been introduced to explain the instability. The longitudinal impedance would cause coherent and incoherent synchrotron tune shift and distort the particle¿s trajectories in longitudinal phase space. Further beam-beam simulation revealed that the longitudinal impedance has strong impacts on the beam stability, squeezing the horizontal stable tune area seriously. The instability has become an important issue during the designs of CEPC and FCC-ee. In this paper, we develop a transverse mode coupling analysis method that could be used to study beam-beam instability with and without longitudinal impedance. This method can also be applied in synchrotron light sources to study transverse mode coupling instability (TMCI) with longitudinal impedance and harmonic cavity. Some preliminary results at Shenzhen Innovation Light Source (SILF) are also shown.

DOI •

reference for this paper ※ doi:10.18429/JACoW-SAP2023-MOCXA02

About •

Received ※ 30 June 2023 — Accepted ※ 11 July 2023 — Issued ※ 23 September 2024

Cite •

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

MOPB004

Lowest Longitudinal and Transverse Resistive-wall Wake and Impedance for Nonultra-relativistic Beams

wakefield, dipole, electron, space-charge

21

J.Z. Tang
TUB, Beijing, People’s Republic of China

With the development of the steady-state microbunch(SSMB) storage ring, its parameters reveal that the ultra-relativistic assumption which is wildly used is not valid for the electron beam bunch train. For a bunch train with a length in the 100nm range, spacing of 1um, and energy in the hundred MeV range, the action angle of the space charge force is estimated by {r/γ}. The space charge effect of the mirror current loop formed in the wall with a scale of 1cm will have a sustained effect on approximately dozens of microbunches behind the source particle. The strength of the interaction between such bunches and the potential instability it may cause needs careful evaluation. At the same time, the effect of the space charge inside a single bunch due to space charge effect also needs to be considered. We reorganized the lowest-order longitudinal wakefield under non-extreme relativistic conditions, and modified the inconsistent part in the theoretical derivation in some essays of the lowest-order transverse wakefield. We present the modified theoretical results and analysis. The action area are then divided into three parts. It lays foundation in future research.

Poster MOPB004 [1.278 MB]

DOI •

reference for this paper ※ doi:10.18429/JACoW-SAP2023-MOPB004

About •

Received ※ 30 June 2023 — Revised ※ 08 July 2023 — Accepted ※ 11 July 2023 — Issued ※ 22 November 2023

Cite •

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

MOPB010

Impact of NEG Coating Thickness and Resistivity on Beam Coupling Impedance

vacuum, ECR, storage-ring, coupling

30

T.L. He, Z.H. Bai, W.W. Li, H. Xu
USTC/NSRL, Hefei, Anhui, People’s Republic of China

In diffraction-limited storage rings, non-evaporable getter (NEG) coatings are generally used to assure the ultrahigh vacuum, which, however, also increase the beam coupling impedance that can affect beam dynamics. Ignoring the influence of coating roughness, the impact of NEG coatings on the impedance mainly depends on the coating thickness and resistivity. In this paper, we investigate the impedance characteristics of a round CuCrZr vacuum chamber coated by NEG with different thickness and resistivity.

DOI •

reference for this paper ※ doi:10.18429/JACoW-SAP2023-MOPB010

About •

Received ※ 29 June 2023 — Accepted ※ 11 July 2023 — Issued ※ 12 August 2024

Cite •

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

MOPB014

Development of a Vlasov Solver for Arbitrary Sub-optimal Lengthening Conditions in Double-RF System

synchrotron, coupling, betatron, cavity

34

J.Y. Xu, N. Wang, H.S. Xu, Y. Zhang
IHEP, Beijing, People’s Republic of China
C.T. Lin
IASF, Shenzhen, Guangdong, People’s Republic of China

Solving Vlasov equation is a classic method for analyzing collective beam instabilities. Considering longitudinal impedance and the nonlinear longitudinal potential well, we developed a new Vlasov solver which can be used to study the transverse mode-coupling instability under the arbitrary sub-optimal lengthening and the optimal lengthening conditions in a double-RF system. Several different techniques to deal with the radial direction of longitudinal phase space have been tested. Numerical discretization method is selected in this paper. The development of the solver is presented in details here. Benchmarks and crosscheck of the solver have been made and presented as well.

DOI •

reference for this paper ※ doi:10.18429/JACoW-SAP2023-MOPB014

About •

Received ※ 30 June 2023 — Revised ※ 08 July 2023 — Accepted ※ 11 July 2023 — Issued ※ 21 August 2024

Cite •

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

MOPB018

Longitudinal Beam Dynamics Design for Super Tau-Charm Facility

luminosity, collective-effects, damping, synchrotron

45

L.H. Zhang, J.Y. Tang
USTC/SNST, Hefei, Anhui, People’s Republic of China
S.Y. Li, T. Liu, Q. Luo
USTC/NSRL, Hefei, Anhui, People’s Republic of China

The project of Super Tau-Charm Facility (STCF) pro-posed in China, as a new-generation high-luminosity e⁺/e⁻ collider in the low-energy region with the center-of-mass energy of 2¿7 GeV, is well underway. The luminosity is targeted at 1.0×10³⁵ cm^-2s⁻¹ at the optimized beam energy of 2 GeV. Longitudinal beam dynamics becomes of great importance for the STCF due to the constraints from the novel beam-beam effect called coherent X-Z instability and severe beam collective effects. In this paper, we will develop an iterative optimization model for the STCF longitudinal beam dynamics design, which takes into account the influence of transverse dynamics, coherent X-Z instability, and collective effects.

DOI •

reference for this paper ※ doi:10.18429/JACoW-SAP2023-MOPB018

About •

Received ※ 30 June 2023 — Accepted ※ 11 July 2023 — Issued ※ 01 November 2023

Cite •

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

MOPB028

Investigation on the Trapped Modes of CPMU at HEPS

damping, synchrotron, simulation, wakefield

62

S. Yue, J.T. Li, S.K. Tian, N. Wang
IHEP, Beijing, People’s Republic of China

The Cryogenic Permanent Magnet Undulator (CPMU) is a crucial component in synchrotron radiation sources. Due to the small magnet gap of CPMU, the interaction between the beam and its surroundings is strong, which can result in a significant contribution to coupling impedance. In this work, the influence of CPMU on coupling impedance was investigated using wakefield and eigenmode solvers. The results indicated that some of the transverse impedance resonances in CPMU were much stronger than the impedance threshold determined by synchrotron radiation damping, which could cause vertical beam instability. To address this issue, different types of damping materials were investigated through simulations to suppress the resonances.

DOI •

reference for this paper ※ doi:10.18429/JACoW-SAP2023-MOPB028

About •

Received ※ 10 July 2023 — Revised ※ 11 July 2023 — Accepted ※ 12 July 2023 — Issued ※ 01 October 2023

Cite •

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

TUPB029

Wakefield Studies for the Step Structure and the Skin Depth of Coated Dielectric Tubes

wakefield, electron, FEL, simulation

147

H. Liu
SINAP, Shanghai, People’s Republic of China
S. Chen, H.X. Deng, B. Liu, Y.M. Wen
SARI-CAS, Pudong, Shanghai, People’s Republic of China
J.J. Guo
Zhangjiang Lab, Shanghai, People’s Republic of China

Funding: This work was supported by YSBR-042, 12125508, 11935020, 21XD1404100 and JCYJ-SHFY-2021-010.
Wakefield issues are always important research objects in free electron laser (FEL) facilities. Since the wakefield in free electron laser facilities usually leads to a decrease of FEL performance, the research of the wakefield impacts is of great significance. Step structures are almost ubiquitous in the overall undulator section of an FEL facility, which always generate critical wakefields. In this paper, we systematically analyze and summarize the wakefield characteristics of step structures including the step-in structure and the step-out structure. In addition, the skin depth issue of the wakefield is still controversial. We study the skin depth of the wakefield field in the vacuum chamber of the kicker in the SHINE, which is made of the dielectric pipe. We proposed the conception of ¿effective skin depth¿ from two different perspectives and wrote simulation codes to calculate the ¿effective skin depth¿. We hope these methods could provide new mentalities for related research in the future.

Poster TUPB029 [0.392 MB]

DOI •

reference for this paper ※ doi:10.18429/JACoW-SAP2023-TUPB029

About •

Received ※ 30 June 2023 — Revised ※ 09 July 2023 — Accepted ※ 12 July 2023 — Issued ※ 21 September 2023

Cite •

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

TUPB033

Heating Estimation of Undulator Vacuum Chamber at S3FEL

electron, wakefield, vacuum, undulator

151

H. Yi
IASF, Shenzhen, Guangdong, People’s Republic of China
X.F. Wang
Institute of Advanced Science Facilities, Shenzhen, People’s Republic of China
X.M. Yang, W.Q. Zhang
DICP, Dalian, Liaoning, People’s Republic of China

Heating of the vacuum chambers are unavoidable when electron beams pass through the chamber channels at relativistic speeds. In the undulator vacuum chambers, such effects might lead to temperature increase of the magnets and eventually cause degradations in the FEL lasing process. Thus, in this paper, the heating of the undulator vacuum chambers at S3FEL due to wake field effects and spontaneous synchrotron radiation are estimated using an analytical approach. For the wake field effects, the contribution from finite conductivity of the vacuum chamber material and from the inner surface roughness are considered. A electron beam profile from a start-to-end simulation is used to calculate the total wake field and the induced heat. For the synchrotron radiation, a simple analytical expression is used.

DOI •

reference for this paper ※ doi:10.18429/JACoW-SAP2023-TUPB033

About •

Received ※ 05 July 2023 — Revised ※ 09 July 2023 — Accepted ※ 12 July 2023 — Issued ※ 26 September 2024

Cite •

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