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beam size
Posted: 16 Apr 2023, 05:21
by Samira.kasaei
Hello Michael,
I tried to calculate beam size for my ring but variation of the beam size is not small along the ring. Could you please take a look to my files?
Thanks alot and best regards,
Samira
Re: beam size
Posted: 02 Jun 2023, 10:25
by michael_borland
Samira,
You need to ensure that you generate a matched beam to start. You have
Code: Select all
&bunched_beam
n_particles_per_bunch = 1000,
one_random_bunch=0,
emit_x = 26e-9,
emit_y = 26e-9,
distribution_type[0] = 3*"gaussian",
distribution_cutoff[0] = 3*3,
! symmetrize = 1,
enforce_rms_values[0] = 1,1,1,
&end
&twiss_output
filename = "%s.twi",
final_values_only = 0
&end
The beam distribution has no defined beta functions, so some defaults will be used. What you want are the periodic beta functions from twiss_output. You can get the desired result by changing the order of twiss_output and bunched_beam, and adding the use_twiss_command_values=1 parameter to bunched_beam:
Code: Select all
&twiss_output
filename = "%s.twi",
final_values_only = 0
&end
&bunched_beam
n_particles_per_bunch = 1000,
one_random_bunch=0,
emit_x = 26e-9,
emit_y = 26e-9,
distribution_type[0] = 3*"gaussian",
distribution_cutoff[0] = 3*3,
! symmetrize = 1,
enforce_rms_values[0] = 1,1,1,
use_twiss_command_values = 1
&end
--Michael
Re: beam size
Posted: 13 Jun 2023, 03:36
by Samira.kasaei
Dear Michael,
Now it is working. However when I add some skew quads in my lattice I got the same vertical beam size. What is wrong in your opinion?
Many thanks and best regards,
Samira
Re: beam size
Posted: 13 Jun 2023, 05:41
by michael_borland
Samira,
Please post your files and I'll take a look.
--Michael
Re: beam size
Posted: 18 Jun 2023, 04:18
by Samira.kasaei
Dear Michael,
Please find the attached.
Best regards,
Samira
Re: beam size
Posted: 19 Jun 2023, 12:12
by michael_borland
Samira,
I think the problem is partly that your skew quadrupoles are relatively weak. For example, if I multiply the skew strengths by 100, there's a clear effect on Sx and Sy in the .sig file.
Also, please note that &twiss_output does not give trustworthy results in the presence of strong coupling. You can use &coupled_twiss_output instead, as well as &moments_output.
--Michael