18.05.2014 | TU Darmstadt | Fachbereich 18 | Institut Theorie Elektromagnetischer Felder | Dip.-Ing. Cong Liu | 1 Various approaches to electromagnetic

11.04.23 | TU Darmstadt | Fachbereich 18 | Institut Theorie Elektromagnetischer Felder | Dip.-Ing. Cong Liu | 1

Various approaches to electromagnetic field simulations for RF cavities

Cong Liu

11.04.23 | TU Darmstadt | Fachbereich 18 | Institut Theorie Elektromagnetischer Felder | Dip -Ing. Cong Liu | 2

Outline

▪ Cavity modeling in CST MICROWAVE STUDIO®

▪ Field simulation in time domain ▪ Field simulation in frequency domain▪ Detection of the eigenmodes in the transmission spectrum

▪ Future work


SPL Cavity Modeling in CST MICROWAVE STUDIO®


Field Simulation in Time Domain

Field probe

Field excitation

Field Simulation in Time domain

▪ Probe Time Signal


15

10

5

0

-5

-10

-15 0 50 100 150 200 250 300 Time / ns


Field Simulation in Time Domain

▪ Using the Fourier transform => Transmission spectrum

dipolepassband

70

60

50

40

30

20

10

0

-10

-20

monopolepassband

0.5 1 1.5 2 2.5 3 Frequency / GHz


Field Simulation in Frequency Domain

▪ Calculation of the resonance frequencies and the corresponding eigenmodes

E



▪ The TM010 Pi-mode for particle acceleration

E



▪ The TM010 Pi-mode for particle acceleration

E


Detection of the Eigenmodes in Transmission Spectrum

▪ The modes of the TM010 band

Result from time domain

Result from frequency domain

90

80

70

60

50

40

30

20

10 690 692 694 696 698 700 702 704 706 708 710 Frequency / MHz

Mag

nitu

de (

db)


Detection of the Eigenmodes in Transmission Spectrum

▪ The modes of the TM110 band

10

0

-10

-20

-30

-40

-50

-60

-700.98 0.985 0.99 0.995 1 1.005 1.01 1.015 1.02 1.025 Frequency / GHz

Result from frequency domain

Result from time domain

Mag

nitu

de (

db)


Future Work

▪ Simulation with higher resolution by means of higher order curvilinear elements

▪ Detection of all higher order modes (HOMs) in the transmission spectrum up to 3 GHz

▪ Damping consideration for HOM-couplers

2023年4月11日 | TU Darmstadt | Fachbereich 18 | Institut Theorie Elektromagnetischer Felder | Wolfgang Ackermann | 13

Cavity Simulations

▪ Particle accelerators- FLASH at DESY, Hamburg

http://www.desy.de

TESLA 1.3 GHz

TESLA 3.9 GHz

▪ Problem definition- Geometry


Elliptic Cavity with Couplers

TESLA 3rd harmonic9-cell cavityincluding couplers

▪ Problem definition- Accelerating field


Fundamental Mode


z

Ez

Longitudinalelectric field strength

▪ Problem definition- Accelerating field


High Precision Field Calculations


Determine the accelerating-mode with high precision


- Task


Simulation Setup

TESLA 3rd harmonic9-cell cavityincluding long beam tubes

PECboundary condition

Search for the - mode field distribution Grid: CST – STUDIO SUITE®

1 W

1 W


- Task


Parallelisation on Cluster Computer

Distributionon 64 nodes

ParMeTiS and VTK

TESLA 3rd harmonic9-cell cavityincluding long beam tubes

Search for the - mode field distribution Grid: CST - Studio Suite®

▪ Simulation results


Electric Field on Cavity Axis

|Ez|

Ex Ez

Ey

585 409 cells, unsymmetric mesh

▪ Simulation results


Higher Resolution

908 268 cells, unsymmetric mesh

Ex

Ey |Ez|

Ez

Mesh has to be Symmetric

▪ Transversal grid information- Cut plane plots


Iris

Equator

unsymmetric mesh generation


Construction of Symmetric Mesh

▪ Symmetric mesh generation

Coaxial coupler

Higher order mode coupler (HOM)

HOM

Beam tube

TESLA 9 cell cavity

Idea:1) Meshing performed only on ¼ of the model2) Copy mesh to assemble the full information

CST - Studio Suite®

Mirror Symmetric Mesh

▪ Transversal grid information- Cut plane plots


Iris

Equator

symmetric mesh generation

Transversal Forces on Particles

▪ Simulation results- TESLA 3.9 GHz


Ex

z zFx

Fy

Ey

c0 By

c0 Bx

Contributions to the force for a particle moving with speed of light along the axis

▪ Integrated forces

Integrated Forces


Quantity used to characterize the fields (kick factors)

▪ Integrated forces

Resulting Kick Factors


TESLA 3.9 GHz (lower resolution) TESLA 3.9 GHz

Full:

Upstream:

Downstream:

Full:

Upstream:

Downstream:

1 904 470 Cells11 780 962 DOFs

3 282 467 Cells20 370 322 DOFs


Summary / Outlook

▪ Summary:

- Request for precise modeling of electromagnetic fields in

resonant structures including small geometric details

such as high power / HOM coupler

- Geometric modeling with CST STUDIO SUITE®

- Kick factor calculation for TESLA 1.3 GHz and 3.9 GHz

▪ Outlook:

- Detailed study of longitudinal and transversal fields for

accurate beam dynamics simulations for SPL / ESS?

Documents

18.05.2014 | TU Darmstadt | Fachbereich 18 | Institut Theorie Elektromagnetischer Felder | Dip.-Ing. Cong Liu | 1 Various approaches to electromagnetic