1. Panel Discussion 3: Impedance Codes
Where do we stand?
Compile/review table of codes
Ideas to control numerics
Ideas to reduce impedance

2. Panel: K. Bane, SLAC W. Bruns, Bruns Field Calculations (GdfidL)
F. Caspers, CERN
M. Dohlus, DESY
E. Jensen, CERN, Secretary
T. Weiland, TU Darmstadt + CST (MAFIA, Microwave Studio) Convener
M. Zobov, INFN Frascati

3. Do we need more codes? No. We need both f-domain and t-domain codes.
Table of codes:
GdfidL
Bruns
t-domain + Eigenfreq.
Linux cluster, parallel 20 CPU’s, 40 GB, up to 109 meshpoints)
HFSS
Ansoft
f-domain
FEM, unstructured mesh with good surface approximation, optimizer
MAFIA
CST
Complete package, includes PIC, limitations in size and precision
MWS
“Successor” of MAFIA. no beam excitation (yet)
TBCI/ABCI
t-domain
Dedicated wakefield codes
Echo/Echo3D
Very long structures, less grid dispersion. …

4. New software or adapt existing?
Adapt existing. What we need:
better surface approximation
window function for short range wake (t-domain)
Extremely short-range wake
medium resistivity (collimator)
Bruns showed how this can be done

5. New area of comp./new physics?
No, but
nonlinear motion + strong shielding
correction of grid dispersion (Novokhatski, Zagorodnow, Weiland: “Echo/Echo3D”)
Resistive wall, thin layers
f-dependent materials
direct calculation in f-domain (see HFSS)
Particle dynamics (breakdown, MP, e-cloud?)

6. Commercial - Research Commercial: Research:
general purpose, not all well adapted
well tested
expensive
Research:
continuous support?
1-man codes risky!
Available for everyone? (Omega3P, Echo, …)

7. Limitations Geometry approximation Grid dispersion
Memory (many modes, large problems )
CPU-time (long range in t-domain)
W32!

8. Optimization? Yes, but not urgently.
Goal functions often hard to define!
Also: Parametric study, sensitivity analysis