rfmode with noise

[li.chao]

Hi,

I would like to simulate the influence on beam from the generator current (Ig) noise, together with the rf-feedbacks.
Is there any example showing how to set the generator current noise in rf mode element?

yours Chao

[michael_borland]

Chao,

You can find something very similar to what you need in the examples file, under storageRingRfNoise.

--Michael

[li.chao]

Dear Michael,
Thanks for your quick reply.

What I am trying to simulate is the rf-noise and rf-feedbacks in the mode element.
The purpose is to know if the feedback can follow the rf-noise and maintain the cavity voltage.

In the simulation, the filling pattern is set as 3840=80*(1bunch+47gap), which is uniformly filled by 80 bunches.

I have a preliminary one-trun rf-feedback, which is represented by the inPhase- and outPhase- feedback filters.
Since it is one-turn feedback, there are 81 rows. Meanwhile, there is a noise file, represented by rfNoise_harm.sdds.
Inside this file, I specified the voltage and phase errors, in a very ideal sinusoid noise.


I am using the filles in this way:

RFMODE3FB: RFMODE, RS=36.0e6, Q=17000, beta=5.0, bin_size=1e-12, n_bins=1000, FREQ="f0 ringHarm * 3 * detune_fre3 +", DRIVE_FREQUENCY="f0 ringHarm * 3 * ", &
V_SETPOINT="V_Hc", PHASE_SETPOINT="Phi_Hc", PRELOAD=1,PRELOAD_HARMONIC="ringHarm 3 *", bunched_beam_mode=1, LONG_RANGE_ONLY=1, &
sample_interval=1,flush_interval=100, &
IN_PHASE_FILTER="InPhase_FeedbackFilters.sdds", QUADRATURE_FILTER="OutPhase_FeedbackFilters.sdds",update_interval=3840,feedback_record="%s.rfhc-fb", &
NOISE_ALPHA_V="rfNoise_harm3.sdds=time+volError", NOISE_PHI_V="rfNoise_harm3.sdds=time+phiError"

In simulation, I set the beam current as zero. When I look into the IgAmplitude data, specified by the "feedback_record", it gives me
result as shown. Could you please help me to set the simulation up appropriately ?

yours Chao

[michael_borland]

Chao,

It's a bit hard to comment without having all the files, but have you tried a simple bandpass filter for the feedback filters? That should suppress the modulation you are imposing in the noise input.

--Michael