Multi-bunch Instability Simulations

[Tyagi]

Dear all,
I want to simulate multi-bunch instability under the influence of long range RW wake field. But I see that without any wake the bunch length grows rapidly. I am attaching here the input files. Please suggest me where is the problem with my input files. I have generated the bunch train using following command.

generateBunchTrain -input bunch_10kP.out -output train_500bunches.out -patternString "500*1*1 967*1*0" -rfFrequency 500e6

Thanks & regards
Deepak

[michael_borland]

Deepak,

The problem may be that you didn't insert the rf cavity into the beamline.

Also, be careful with your rf frequency values in the generateBunchTrain command and RFCA definition. They should match exactly.

--Michael

[Tyagi]

Hi, as per your reply I added RF cavity into the beamline and generate bunch train using RF frequency exactly as in RFCA element even than when I plot "Pass vs st" for first bunch and last bunch the graph are attached.

[michael_borland]

Some possible sources of the problem:
1. You are not setting the START_PID and END_PID parameters on the WATCH elements correctly, so you are seeing the length computed over several bunches.
2. You have one or more particles outside the rf bucket, so that those particles deviation from the centroid grows quickly.

Most likely #1.

--Michael