Tracking with LRWAKE and ILMATRIX

Moderators: cyao, michael_borland

Post Reply
Siwei_Wang
Posts: 15
Joined: 27 Jun 2017, 07:28

Tracking with LRWAKE and ILMATRIX

Post by Siwei_Wang » 05 Jan 2022, 10:26

Dear Michael,

I'm studying transverse coupled-bunch instability from long-range resistive-wall wake. In my tracking, I only used ILMATRIX and LRWAKE elements, together with several watch points for each bunch. I calculated the maximum growth rate of each bunch. Then the growth rate is exchanged to 1A.
At first I tracked with only one-particle per bunch, and the result is consistent with the analytic formula, then I increased the number of particles per bunch to 10,000. Then the growth rate of each particle decreases greatly (10 times smaller). But the other parameters are all the same. The exchanged growth rate at 1A is also different when the beam current in tracking is different. Do you have any idea what the reason might be?

Best regards,
Siwei
Attachments
10000particles.zip
Tracking files
(4.4 MiB) Downloaded 92 times

michael_borland
Posts: 1795
Joined: 19 May 2008, 09:33
Location: Argonne National Laboratory
Contact:

Re: Tracking with LRWAKE and ILMATRIX

Post by michael_borland » 07 Jan 2022, 15:49

Siwei,

Can you supply the file bunchid-offset, used by the sdds_beam command?

Thanks--Michael

Siwei_Wang
Posts: 15
Joined: 27 Jun 2017, 07:28

Re: Tracking with LRWAKE and ILMATRIX

Post by Siwei_Wang » 08 Jan 2022, 08:33

Dear Michael,

I wanted to attach the bunch file at first but it was too large and failed to be uploaded.
So I attached the script to generate the bunch. The file makebunch.ele uses bunched_beam to generate the bunch file for a single bunch bunchid-10000.out. And trackSB1.ele uses sdds_beam and duplicate the single bunch and save the multi-bunch file bunchid-offset.out. The final bunch file is nearly 500MB.

Many thanks,
Siwei
Attachments
makebunch.zip
(478.46 KiB) Downloaded 81 times

Siwei_Wang
Posts: 15
Joined: 27 Jun 2017, 07:28

Re: Tracking with LRWAKE and ILMATRIX

Post by Siwei_Wang » 13 Jan 2022, 05:01

Dear Michael

It seems the problem comes from when I duplicated the bunch to make the beam, I give a minus value to the duplicate_stagger[4], making the bunches in the beam have a decreasing sequence in time. In this case it seems LRWAKE is dealing with the beam as a single bunch, so it gave a much smaller growth rate. I removed the minus sign in sdds_beam and generated a new beam, the result seems to be correct.

Best regards,
Siwei

michael_borland
Posts: 1795
Joined: 19 May 2008, 09:33
Location: Argonne National Laboratory
Contact:

Re: Tracking with LRWAKE and ILMATRIX

Post by michael_borland » 13 Jan 2022, 18:55

Siwei,

Good to know that you solved the problem.

It makes sense that having a negative stagger would cause problems. It corresponds to the higher-numbered bunches arriving earlier in time. I'll modify the code to detect this and issue a warning.

Thanks.

--Michael

Post Reply