The OPAL Discussion Forum

["Adelmann Andreas (PSI)" <andreas.adelmann AT psi.ch>]

Dear Dragos, the collimator aperture can not be changed w.r.t. the local reference frame.

I think you would need to estimate before running the simulation. Certainly one can

implement such a collimator model. If this is very important I can make a feature request

for you.

 

Cheers A

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Dr. sc. math. Andreas (Andy) Adelmann
Head a.i. Labor for Scientific Computing and Modelling 
Paul Scherrer Institut OHSA/ CH-5232 Villigen PSI
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On 12 Sep 2020, at 19:16, Dragos Constantin <dragos.constantin AT varian.com> wrote:

Hi All,

I have defined an ECOLLIMATOR like this:

BCOL: ECOLLIMATOR, L = 1, Z =0, X = 0, Y = 0, XSIZE = 0.002, YSIZE = 0.002, OUTFN = "BCOL";

so I have a circular aperture of 2mm radius. During the simulation the reference particle deviates from the central axis because of fields asymmetries. 

Is it possible that the circular aperture is defined with respect to the reference particle local reference frame instead of the laboratory reference frame?

It looks like the particles are no longer tracked if they are more than 2mm distance from the reference particle. I have attached two pictures that show the macroparticles bunch and the collimator wall from 2 different orrientations. On the 'cross section' view you can clearly see the circular aperture acting on the bunch but its position is obviously displaced to the right.

Thanks,

Dragos

<aperture_1.png><aperture_2.png>