Generation of the bunch
Posted: 10 Mar 2022, 08:36
Dear all,
I did some tracking simulations along a linac using bunched_beam. My line is a FODO with some RF cavities, so I computed the optics to have periodic beta and alfa, and all was working.
Now I would like to simulate the same line, but using sdds_beam, because I can have a better representation of the beam longitudinal phase space.
For the optics I used sddsmatchtwiss from the distribution at the entrance of my line:
sddsmatchtwiss elegant_distr.sdds distr_matched.sdds -xPlane=beta=2.398316000894728e+00,alpha=5.018045512606445e-01 -yPlane=beta=1.230486994429303e+01,alpha=-2.328639432567440e+00
This worked, because if I check with:
sddsprintout output.txt -col=betax -col=betay -col=alphax -col=alphay
I obtain:
betax betay alphax alphay
m m
--------------------------------------------------------------------------------
2.398587e+00 1.230482e+01 5.016243e-01 -2.328620e+00
My .ele file is (for the parts where I have the beam definition):
&sdds_beam
input = "distr_matched.sdds",
input_type = "elegant",
fiducialization_bunch = 1,
center_arrival_time = 1,
sample_interval = 5,
reuse_bunch = 0,
&end
The problem is that the Twiss parameters are not what I expect.
The questions are:
- Is there a simple way to match also the emittance of the distribution like it is done for the Twiss functions, or should I do a script to do it taking the particles? (I have a smaller emittance now that before, because some margin was added for the emittance);
- Any idea of why I see this strange behaviour of the optics? Did I misunderstand anything?
Thanks in advance for any feed-back, and have a nice day,
Simona.
I did some tracking simulations along a linac using bunched_beam. My line is a FODO with some RF cavities, so I computed the optics to have periodic beta and alfa, and all was working.
Now I would like to simulate the same line, but using sdds_beam, because I can have a better representation of the beam longitudinal phase space.
For the optics I used sddsmatchtwiss from the distribution at the entrance of my line:
sddsmatchtwiss elegant_distr.sdds distr_matched.sdds -xPlane=beta=2.398316000894728e+00,alpha=5.018045512606445e-01 -yPlane=beta=1.230486994429303e+01,alpha=-2.328639432567440e+00
This worked, because if I check with:
sddsprintout output.txt -col=betax -col=betay -col=alphax -col=alphay
I obtain:
betax betay alphax alphay
m m
--------------------------------------------------------------------------------
2.398587e+00 1.230482e+01 5.016243e-01 -2.328620e+00
My .ele file is (for the parts where I have the beam definition):
&sdds_beam
input = "distr_matched.sdds",
input_type = "elegant",
fiducialization_bunch = 1,
center_arrival_time = 1,
sample_interval = 5,
reuse_bunch = 0,
&end
The problem is that the Twiss parameters are not what I expect.
The questions are:
- Is there a simple way to match also the emittance of the distribution like it is done for the Twiss functions, or should I do a script to do it taking the particles? (I have a smaller emittance now that before, because some margin was added for the emittance);
- Any idea of why I see this strange behaviour of the optics? Did I misunderstand anything?
Thanks in advance for any feed-back, and have a nice day,
Simona.