collimation wakefield simulations carl beard astec daresbury laboratory
DESCRIPTION
MAFIA 3D Time domain simulations allow the possibility of TDR simulations Many benchmarks with measurement and code have validated results (SNS, CEBAF). Limited to below 30 GHz due to memory constraints. Particle-in-cell Diagonal filled cells (though mesh Many benchmarks have also unvalidated the codeTRANSCRIPT
Collimation Wakefield Simulations
Carl BeardASTeC
Daresbury Laboratory
Computer Simulations of Spoiler designs
1mm
1m
•Codes being developed to measure the impedance of vessels
•ECHO2D, MWStudio, HFSS, GDFIDL
•Calculation errors due to small angle of taper
•Off axis measurements
user defined pulse possibleThe length of the structure and the frequency make
simulation time very long
MAFIA
MAFIA 3D Time domain simulations allow
the possibility of TDR simulations Many benchmarks with measurement
and code have validated results (SNS, CEBAF).
Limited to below 30 GHz due to memory constraints.
Particle-in-cell Diagonal filled cells (though mesh
Many benchmarks have also unvalidated the code
Meshing solutions
Quadratic mesh yields fast results but poor resolution
Diagonal mesh cells do allow tapers to be accurately meshed, however shallow angles lead to poor aspect ratios
Time V’s accuracy
Coarse mesh
Fast run-time
Low accuracy
Fine mesh
Slow run-time
Good accuracy
Finding the
balance
Microwave Studio
Same solver as MAFIA Improved meshing (PBA) Still limited to below 30 GHz Early days…
GDFIDL
3D Finite difference time domain code Lossy materials are allowed for calculations of resistive
wall wakefield. Particle-in-cell Capability
Bunch lengths could lead to lengthy simulation time Some verifiaction with “Real” tests up to 120 GHz
Synergy with LC-ABD Cavity BPM Energy Spectrometry GDFIDL Simulations Bench tests with Impedance Test Apparatus Beam tests
Cluster license purchased, to be hosted at UCL.
Other codes
HFSS Frequency domain solver
Over large bandwidths sharp resonance's could be overlooked. Tetrahedral meshing
MAGIC MAFIA-esque
No diagonal cells, so stepped geometry guaranteed ECHO-2D 3D??
Only 2D FDTD version working Initial discussions suggested that bunch lengths were too
demanding Unproven CST Solver (again) Availability ?????
Bench Test TDR and Transmission impedance measurements
Current apparatus provides ~ 25ps pulse waveform analysis provides loss parameter Critical issue:
Pulse speed! Time ~ LC bunch z
~1 ps 10 ps fastest pulse time available VNA ~6GHz Above 10 GHz Signal-to-noise ratio is
too low
~1.7m
Test Rig
Test Rig 2
Matching Parts
Launch cone
Test Vessels
Impedance Rig 3
Tektronics 7854
TDR Scope
6 GHz NA –
S-parameter test set
Purpose of the test
Following the last meeting in February there was a recommendation that the test gear should NOT be used for spoiler design
Benefits Experimental expertise Benchmarking Low frequency verification
of designs Improve the understanding
of the physics By scaling at 100ps, 50ps, 25ps
and 10ps, extrapolate for 1psTimescale
Impe
danc
e