1. EM Simulation of wakes in BSRT beampipe with extraction mirror
Tool: Time domain solver of ACE3P Suite.
Crosscheck with CST Particle Studio.
Andriy Nosych / CERN BE-BI-QP
Impedance meeting / 25 June 2012

2. (BSRT complete assembly)
Simplified BSRT model is considered
(BSRT complete assembly)
Beam
22 mm
Mirror back (most likely coated)
Silicon
Mirror front

3. Excitation: Single bunch with Gaussian charge distribution
Charge = 1.7e-8 C
Bunch length: 0.3 m / 1 ns / [-4s, 4s]
s = 40 mm / 130 picoseconds
Bunch transverse size: point

4. Stainless-steel mirror
Simulated mirror ACE3P
Silicon mirror
(eps = 11.9,el.cond=2.5e-4)
Silicon + coated mirror (by putting an electric boundary on back surface)
Stainless-steel mirror
Wake potential along beam axis

5. Stainless-steel mirror
Simulated mirror ACE3P
Silicon mirror
(eps = 11.9,el.cond=2.5e-4)
Silicon + coated mirror (by putting an electric boundary on back surface)
Stainless-steel mirror
Coated/Steel mirror have a resonant mode at around MHz
Harmonics?

6. Crosscheck with CST Particle Studio (coated mirror sample)
Full assembly VS Simplified assembly
Full assembly peak at: 640 MHz
Simplified peak at: 655 MHz

7. First test run with 3-bunch train (Steel mirror sample) @ ACE3P
Peak at 670 MHz

8. E-field Magnitude @ ACE3P + E-field probe along white line (mirror edge)

9. UPDATE “New” complete mirror support assembly
Full electric contact between washer and body. Thus no vacuum considered behind washer.
Additional cavities behind mirror support.
“Ferrite” ring (made of Steel so far, can not simulate ferrite)
“Old” simplified
mirror support
CONCLUSIONS:
With a complete model of a mirror support, the resonating mode frequency shifts to 600 MHz.
No big difference between resonances with the mirror “in” and “out”.
Mirror in
Beam-mirror: 22 mm
Mirror out
Beam-mirror: 50 mm