The OPAL Discussion Forum

[Anastasia Ierides <Anastasia.Ierides AT varian.com>]

Hi Andreas,

Attached you will find my input files for both cases (with the full linac 
geometry and the separated linac geometry) as well as a plot of the expected 
(red) normalized electric field felt by the reference particle, versus what 
is outputted by OPAL (blue), where the geometry seems to be extended to 
almost twice the distance. I have looked at the initial distribution file 
(LINAC1D_DIST.dat) and it shows a spatial increase between the separated 
cavities, even though the cavities are specified to be one right after the 
other. I have not attached the field map files here as they are a bit large. 
Will you need the field map files as well?

Thanks,

Anastasia

-----Original Message-----
From: Adelmann Andreas (PSI) <andreas.adelmann AT psi.ch> 
Sent: Wednesday, December 18, 2019 10:49 PM
To: Anastasia Ierides <Anastasia.Ierides AT varian.com>
Cc: opal AT lists.psi.ch
Subject: Re: [Opal] Extra travel distance added to reference particle data 
between subsequent attached RF cavities

Hi Anastasia can you attach a example, showing your problem?
A

> On 19 Dec 2019, at 02:51, Anastasia <anastasia.ierides AT varian.com> wrote:
> 
> Hello all,
> 
> As a tutorial, I am trying to model a linear accelerator as a beam 
> line of separate RF cavities rather than the whole LINAC geometry as 
> one RFCavity element. I have run the simulation both with a single 
> RFCavity element and with multiple cavities, wherein the dimensions 
> are appropriately defined in the field map files, such that the 
> elements are right next to each other with no space in between.
> 
> In the single element simulation, the refence particle electric field 
> is observed to depict expected behavior in the defined geometry, but 
> in the case of separate elements, there seems to be an additional 
> “space” that is added between the individual elements, extending the 
> overall geometry to almost twice the length. Could this be a mistake 
> on my part in my input files, etc., or is there something in the code 
> that by default forces this type of behavior? For instance, in a 
> situation where elements are too close together, are they forced to have 
> some minimal distance between them, etc.?
> 
> I guess the first question should be, does OPAL allow for the 
> capability to model a whole geometry as separate, yet connected RFCavity 
> elements?
> 
> Any help in this would be greatly appreciated.
> 
> Thanks!

Attachment: LINAC1DFull.in
Description: LINAC1DFull.in

Attachment: LINAC1D.in
Description: LINAC1D.in

Attachment: ExpectedvsOPAL.jpg
Description: ExpectedvsOPAL.jpg