Vertical offset for collimators

[MDP]

Dear all,

I have a problem with some collimators in my simulations. At the positions of two (out of 3) collimators the beam has a vertical offset of 2 cm and, although the parameter DY was set to 2 cm as well, all particles get lost at this collimator.

I checked the beam position using: sddsprintout –col=DY –col=ElementNames filename.cen
And the collimator position using: sddsprintout -col=ElementName -col=ElementParameter -col=ParameterValue f2_extraction_rb.par

And the results confirmed that both the beam and the collimator hast 2 cm vertical offset.
If I open the collimator in vertical plane to a radius of 22 cm no particles get lost any more.

Do you understand the reason for the losses?

Thank you in advance!
Best regards, Matthias

[michael_borland]

Matthias,

There seems to be a bug for the ECOL element if the length is non-zero. Three workarounds are possible:

* Use RCOL, if possible.

* Use a pair of ECOL elements separated by a drift space that is equal to the desired ECOL length.

* Instead of misaligning the ECOL element using the DY parameter, bracket the ECOL by two MALIGN elements, as in
dyn: malign,dy=-0.02
dyp: malign,dy=0.02
col: ecol,...
bl: line=(dyn,col,dyp)

--Michael

[MDP]

Hi Michael,

thanks for your help!
I use now ECOL elements with zero length and spaces in between (as you recommended) and it works fine.

Regards, Matthias