Beam centroid in linac

[yuehao]

Hi, Michael

I have a very long beam line that the beam only pass once. After I throw in quad alignment error, is there a easy way to get the beam centroid assuming zero initial condition, like 'close_orbit' for a ring.

If I have to add WATCH elements, is there a special string pattern that assign the WATCH output file name same as the element name, like %s for root name.

Thanks a lot.
Best,
Yue

[michael_borland]

Yuehao,

You can get this using the "centroid" parameter in &run_setup:

Code: Select all

&run_setup
...
centroid = %s.cen
...
&end

Once the run is complete, the .cen file will have all the centroids vs s. There is also a sigma file available (sigma = %s.sig) with beam sizes, emittances, etc.

--Michael

[yuehao]

Thanks a lot, Michael.

Further question is, when I want to do orbit correction, should I use element WATCH or HMON/VMON as BPM. Is there any difference?

Stay warm,
Yue

[michael_borland]

Yue,

You'll need to use MONI or HMON/VMON for orbit correction. WATCH elements are only for output.

--Michael

[yuehao]

Another question is: If one KICKER element occurs multiple times in the beam line, are they treated as same element with one kick strength, or each occurance are independent element?

Thanks again.
Yue

[michael_borland]

Yue,

The answer is: a bit of both. If you define the element to have a certain strength in the lattice file, then all instances will have that strength at the start. However, orbit/trajectory correction will change them individually and (by default) ignore the initial kick settings.

--Michael

[yuehao]

Thank you for your quick answer.
Just to confirm, there is no way to force the orbit correction to have same strength if the kicker 's name is same?

Best,
Yue

[michael_borland]

Thank you for your quick answer.
Just to confirm, there is no way to force the orbit correction to have same strength if the kicker 's name is same?

Best,
Yue

That's correct.

--Michael