1. Simulation of 200 MHz RF cavities. 11 cells preliminary results
Alexej Grudiev
20/04/2016

2. HFSS setup: 3D model from Ton
Port 6
Port 5
Port 4
Port 3
Port 2
Port 1

3. Comparison measurements vs CST MS vs HFSS
Very good agreement between CST MS and HFSS for S-parameters

4. HFSS: Eigenmode. Mesh and E-field of f0=628.5 MHz mode
PML
PML
PML
PML

5. HFSS: Eigenmodes: Ez (red), Ey (blue)

6. HFSS eigenmode: Modes parameters table, 2nd order tetr
HFSS eigenmode: Modes parameters table, 2nd order tetr., 12 iterations (~10% error in R/Q)
f [MHz] Q
R/Q [linacOhm]
Z [Ohm] 1
620.2
160
3.2
256 2
622.3
5891
0.055
162 3
623.0
17351
13.85
120156 4
624.5
14359
0.91
6533 5
625.2
518
29.3
7589 6
626.9
6451
15.28
49286 7
628.6
473
29.43
6960 8
631.0 57
8.41
240 9
631.4
261
5.55
724 10
634.4
445
0.23 51
Definitions:
R/Q = Vz2/ωU
Circuit impedance
Z=R/Q*Q/2

7. Plane wave excitation setup: dYpw=1mm
CompMagE in log scale: f=630MHz

8. E-field on axis with PW excitation: dYpw = 1mm; f=630MHz

9. E-field on axis with PW excitation: dYpw = 1mm; f=622
E-field on axis with PW excitation: dYpw = 1mm; f=622.86MHz (Highest Q-factor)
10π/11-eigenmode
f0=623.0MHz
Q = 17400

10. CST wake setup 3D model from Ton
Mesh is good but still might be not good enough to describe narrow band 200 MHz rejection filter.
So 200 MHz impedance might be different from FEM codes or measurements

11. CST wake, longer wake

12. CST impedance (FFT, cos^2 filter)
df = 1/Tmax=c/s_max =3e8/300 = 1 MHz, better

13. Comparison of Re{Zl} between HFSS eigenmode, HFSS plane wave and CST wakefield