Titel der Prsentation
Bunch Emission Simulation for the PITZ* Electron Gun Using CST
Particle StudioTMYe Chen, Erion Gjonaj, Wolfgang Mller,Thomas
WeilandDESY-TUD Meeting 09.08.201309. August 2013 | TU Darmstadt |
Fachbereich 18 | Institut Theorie Elektromagnetischer Felder | Ye
Chen |7. August 2013| Fachbereich 18 | Institut Theorie
Elektromagnetischer Felder | Prof. Dr.-Ing. Thomas Weiland| 1The
European XFEL is more than three kilometers long. It will begin at
the DESY site in Hamburg-Bahrenfeld and run to the town of
Schenefeld, where the main building with its underground experiment
hall will be located.ContentsIntroduction CST field
simulationEigenmode simulation for Gun 4.3 cavitySolenoids
simulationCST PIC simulation Modified simulation modelASTRA
particles importSimulation resultsDiscussionCathode studiesNext
steps09. August 2013 | TU Darmstadt | Fachbereich 18 | Institut
Theorie Elektromagnetischer Felder | Ye Chen |Introduction
Motivation Main tasks 3D CST field simulations (Gun 4.1/4.3 cavity,
Solenoids)3D CST beam dynamic simulationsfor different bunch
charges with homogeneous/inhomogeneous particle
distributionsconvergence study and comparisons to ASTRA Cathode
studiesInfluences from materials, non-uniformities, on beam
qualitiesEmittance study09. August 2013 | TU Darmstadt |
Fachbereich 18 | Institut Theorie Elektromagnetischer Felder | Ye
Chen |CST Field SimulationSimulation resultsMode modeField
Ratio1.04Frequency1.3019 GHzEigenmode Calculations
Accelerating Ez field along z-axiszEz
Simulation Model for Gun 4.3 Geometry
Settings/mm55100180.64179.902010009. August 2013 | TU Darmstadt |
Fachbereich 18 | Institut Theorie Elektromagnetischer Felder | Ye
Chen |7. August 2013| Fachbereich 18 | Institut Theorie
Elektromagnetischer Felder | Prof. Dr.-Ing. Thomas Weiland| 4CST
Field (Solenoids) Simulation Pos. of Main = 276 mm Pos. of Bucking
= -172 mm Curr. of Main = 375 A Curr. of Bucking = -31 A Bzmax
0.2279 T Bz(0,0,0) 10-7 T
Geometrical Settings/cm
Simulation Modelfor Solenoids
Longitudinal B field along z-axisBzz09. August 2013 | TU
Darmstadt | Fachbereich 18 | Institut Theorie Elektromagnetischer
Felder | Ye Chen |PIC Simulation ModelMin. mesh step=
0.01mmMeshcell numbers: up to 1000MIncluding PIC position monitor,
phase-space monitors for momentum, energy, velocity , 2D particle
monitors and particle import interfaces
electron bunch2D Particle Monitors:
transversal/longitudinalParticle Import InterfaceLocal Mesh
Refinement CST PIC SimulationBunch Parameters & Fields Data
Bunch radius = 0.4 mm Bunch charge = -1 nC Bunch length = 21.5 ps
Rise/Fall time = 2 ps Macro particles = 500 k Cavity frequency =
1.30 GHz Ez at cathode = 60.58 MV/m Field ratio = 1.04 Bzmax =
0.2279 T09. August 2013 | TU Darmstadt | Fachbereich 18 | Institut
Theorie Elektromagnetischer Felder | Ye Chen |CST PIC
Simulation
Amplitude of EzzImported longitudinal electric field along
z-axis for PIC simullationfield interpolation at the cathode
planeProblem descriptionmesh resolution difference in the cathode
region between eigenmode simulation and PIC simulation can lead to
field interpolation at the cathode planefield interpolation within
the first meshcell between PEC and vacuum Solutionskeep the mesh
resolution same, but very mesh-consumingmodify PIC simulation
model09. August 2013 | TU Darmstadt | Fachbereich 18 | Institut
Theorie Elektromagnetischer Felder | Ye Chen |CST PIC
SimulationGoalto improve the accuracy of the field solution within
a short distance from the cathode plane at z = 0Implementationsend
positrons & electrons at the same timeall velocity directions
reversedkeep field ratio same
Longitudinal E field in the mirrored cavityzEzelectron
bunchpositron bunchMirrored gun model for PIC09. August 2013 | TU
Darmstadt | Fachbereich 18 | Institut Theorie Elektromagnetischer
Felder | Ye Chen |
Note that,simulations with both of the models showed trends of
convergencebetter convergence rate with the mirrored
model43.532.521.510.5040353025201510500 250 500 750 1000 1250
1500Xrms /mmDiscrepancy /%z /mmCST-1, z0.075mmCST-2, z0.05mmCST-3,
z0.03mm, with original modelASTRA SimulationDiscrepancy with ASTRA
for CST-3CST-5, z0.015mmCST-4, z0.03mm, with mirrored
modelDiscrepancy for CST-3ASTRACST-1CST-2CST-3CST-5CST-4horizontal
rms size of the beam along z-axis (Gun4.1)Discrepancy with ASTRA
for CST-5Discrepancy for CST-5CST PIC Simulation09. August 2013 |
TU Darmstadt | Fachbereich 18 | Institut Theorie
Elektromagnetischer Felder | Ye Chen
|Lt=21.5E-3nsrt=2E-3nsLE=0.00055keVsig_x=sig_y=0.4mmQ
=1nCIpart=500,000
Species=electronsDist_z=pDist_pz=iDist_y=Dist_x=rDist_px=Dist_py=rRef_zpos=0.0mInput
Data for ASTRA:ASTRA Particle ImportParticles z=z0, t(t0,t1)
Astra2CSTParticles t=t0, z(z0,z1)Particle Import
Interface(CST-PS)CST PIC Simulation09. August 2013 | TU Darmstadt |
Fachbereich 18 | Institut Theorie Elektromagnetischer Felder | Ye
Chen |CST PIC Simulation
average energy of the beam along z-axis09. August 2013 | TU
Darmstadt | Fachbereich 18 | Institut Theorie Elektromagnetischer
Felder | Ye Chen |7. August 2013| Fachbereich 18 | Institut Theorie
Elektromagnetischer Felder | Prof. Dr.-Ing. Thomas Weiland| 11CST
PIC Simulation
horizontal rms size of the beam along z-axis
beam energy spread along z-axis09. August 2013 | TU Darmstadt |
Fachbereich 18 | Institut Theorie Elektromagnetischer Felder | Ye
Chen |CST PIC Simulation
bunch length of the beam along z-axis
horizontal normalized emittance of the beam along z-axis09.
August 2013 | TU Darmstadt | Fachbereich 18 | Institut Theorie
Elektromagnetischer Felder | Ye Chen |Discussion Cathode
StudiesSurface impedance: Frequency-dependent isotropic surface
impedance model
Gun cavity materialCathode material
Gun 4.3 Cavitycathode plane at z = 0yz : conductivity, : angular
frequency09. August 2013 | TU Darmstadt | Fachbereich 18 | Institut
Theorie Elektromagnetischer Felder | Ye Chen |Cathode StudiesSpace
charge field vs. time in correspondence to various conductivities
of cathode materialSPCH Field
with bunch parameters: -1nC, 0.4mm(radius), 500k(particle
numbers), 2ps/21.5ps\2psby using the same mesh resolutionduring
propagation time up to 80psat the same location, z=5mmSimulation
performed Time /ps09. August 2013 | TU Darmstadt | Fachbereich 18 |
Institut Theorie Elektromagnetischer Felder | Ye Chen |Summary
& PlansSummary Field simulations for gun 4.1 & 4.3 done,
desired fields produced CST PIC results (1nC) on beam energy and
spread, beam size, bunch length and beam emittance obtained,
compared to ASTRA. The discrepancy with ASTRA is about 10%, 5%, 9%
and 20%, respectively. Simulations on cathode study showed the
influence of the cathode material on the space charge field. Plans
Perform PIC simulations for various bunch chargeswith inhomogeneous
particle distributions Further study on the influence of cathode
material on the beam qualities09. August 2013 | TU Darmstadt |
Fachbereich 18 | Institut Theorie Elektromagnetischer Felder | Ye
Chen |Thanks for your attention!09. August 2013 | TU Darmstadt |
Fachbereich 18 | Institut Theorie Elektromagnetischer Felder | Ye
Chen |
