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-QPImpedance meeting / 25 June 2012

Simplified BSRT model is considered

Mirror front

(BSRT complete assembly)

Beam

22 mm

Mirror back (most likely coated)

Silicon

Excitation:

Single bunch with Gaussian charge distributionCharge = 1.7e-8 CBunch length: 0.3 m / 1 ns / [-4s, 4s]s = 40 mm / 130 picosecondsBunch transverse size: point

Wake potential along beam axis

Simulated mirror modifications @ 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

Simulated mirror modifications @ ACE3P

Coated/Steel mirror have a resonant mode at around 658-670 MHz

Harmonics?

Silicon mirror (eps = 11.9,el.cond=2.5e-4)

Silicon + coated mirror (by putting an electric boundary on back surface)

Stainless-steel mirror

Crosscheck with CST Particle Studio (coated mirror sample)

Full assembly VS. Simplified assembly

Full assembly peak at: 640 MHzSimplified peak at: 655 MHz

First test run with 3-bunch train (Steel mirror sample) @ ACE3P

Peak at 670 MHz

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

“Old” simplified mirror support

“New” complete mirror support assembly

Mirror in

Beam-mirror: 22 mm

Mirror out

Beam-mirror: 50 mm

“Ferrite” ring (made of Steel so far, can not simulate ferrite)

Additional cavities behind mirror support.

Full electric contact between washer and body. Thus no vacuum considered behind washer.

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”.

UPDATE