1. EM Simulations for PETRA3
N. Baboi, DESY, Hamburg
Introduction
1. Electrostatic simulations with MAFIA
BPM for damping wiggler
BPM for “standard” vacuum chamber
2. Simulations with Microwave Studio (MWS)
Coupling between BPM-buttons
BPM Workshop, Lüneburg, Nov. 30, 2006

2. PETRA3 Energy: 6 GeV Emittance: 1nm rad Current: 100 mA
Bunches: 40 / 960

3. BPMs for PETRA3
235 BPMs (buttons) for various chamber sections

4. Monitor Constant 1/K
FUR
FDR
FUL
FDL

5. 1. Electrostatic Simulations (MAFIA)
Electrostatic calculation
1 V at one button
calculate field distribution
 monitor constant K
through reflections  field for all 4 buttons
combine these fields  FH and FV  KH and KV
 coupling factor between beam and BPM-pickups
= voltage at middle of BPM for 1 V at one button (in %)

6. 1a. BPM for Damping Wiggler
distance between buttons = 24 mm
chamber: 30 x 120

7. BPM for Damping Wiggler: Coupling

8. BPM for Damping Wiggler: Monitor ConstantFH FV

9. BPM for Damping Wiggler: Monitor Constant (2)
1/KH = 0.08 mm-1
1/KV = 0.06 mm-1
For 1 mm resolution need 8·10-5 resolution in FV
Button
distance
1/Kx [mm-1]
1/Ky [mm-1]
Coupling [%] 20
0.074
0.070 12 24
0.083
0.061 10 31
0.093
0.045 7

10. 1b. “Standard” Chamber 1/KH = 0.059 mm-1 for j = 55 deg
1/KV = mm-1
for j = 55 deg
R. Wanzenberg

11. 2. Coupling between Buttons: UR – UL MAFIA-S: Electrostatic Simulation
defined as vacuum
~0.9e-4V
coupling to beam: 23%
coupling to button ≈ 0.009%

12. Coupling between Buttons: UR – DR MAFIA-S: Electrostatic Simulation
defined as vacuum
~0.12V
coupling to button ≈ 10%
BUT measurement (Neumann): -45dB -> 0.6%!

13. Coupling between Buttons Microwave Studio: S-parameters
good agreement to measurements
(normalized to 50 Ohm)

14. Coupling between Buttons Microwave Studio: Time Domain
source
port 1
port 3
electric
(or magnetic)
boundaries
port 4
port 2

15. Coupling between Buttons Time Domain – Results

16. Coupling between Buttons “Beam” Simulation
1-4: ports
5: discrete port (source)
port 1
port 3
discrete
port 5
(S-Param, 10kW:
practically I-source)
electric
boundaries
port 2
port 4

17. Coupling between Buttons “Beam” Simulation - Results

18. Coupling between Buttons “Beam” Simulation - Results (2)
Current / Voltage

19. Coupling between Buttons “Beam” Simulation - Results (3)
Effect of other buttons
worst case: other buttons are short-circuited => no difference!

21. 3. Error Analysis: BPM for Straight Section
chamber: 94 x 94
15 mm buttons (Meggitt)
5deg error in UR and DL pickups

22. Preliminary: BPM for Straight Section: Monitor Constant
Without error
With 5 deg error  10% error

23. Preliminary: BPM for Straight Sections Fields without/with angle error
5deg angle error