[mcxtrace-users] [Warning Possible spam] Re: Off-axis parabolic mirror Component

[Peter Kjær Willendrup]

Hi again,

Sorry, I forgot to mention that the attachment in the last mail is intended for McXtrace 3.x, here I attach a corresponding instrument for 1.7.

Best,
Peter



On 7 Jun 2022, at 10.56, Peter Kjær Willendrup <pkwi at fysik.dtu.dk<mailto:pkwi at fysik.dtu.dk>> wrote:

Hi Jordan,


I believe nothing should in principle prevent using Mirror_parabolic in an off-axis geometry:

The mirror takes incoming photons from (close to) arbitrary incoming directions, propagate them to the mirror geometry and reflect them according to photon properties and the mirror geometry.

For properly understanding the mirror parametrisation / coordinate system, I suggest starting from the example instrument Test_mirror_parabolic.instr found in your McXtrace installation (File->New From Template->Tests->Test_mirror_parabolic). Then try doing a few Trace runs (i.e. visualising the instrument geometry), perhaps varying the mirror geometry (i.e. essentially a/b and xwidth/zdepth) - find an example attached where you may vary a, b, xwidth and zdepth without recompilation.

The mirror implements a paraboloid geometry with:

* extent mainly in x / z dimensions (i.e. at 0 curvatures it lies flat “on the ground”)
* adding curvature, this curves the mirror “up” with respect to “the ground”

In the attached example a rotation has been applied on the x-axis, meaning that now the mirror instead “stands”. Further, I have exaggerated the dimensions and curvature to more easily see what is going on.


Best and hope this helps,
Peter




On 6 Jun 2022, at 15.28, Jordan Cox <jmcox at mit.edu<mailto:jmcox at mit.edu>> wrote:

Hello All,

I am getting started with McXtrace, and trying to build an instrument which is collimated using an off-axis parabolic (Göbel) mirror. I assume that the Mirror_parabolic component in McXtrace is not off-axis, so my thought was to simulate a Gö​bel mirror by placing the source at the mirror's focal point and making the mirror sufficiently large so as to be the full parent paraboloid of the off-axis mirror. However, I am having some difficulties understanding the relative coordinate system of the parabolic mirror component which is making it tough to determine if this idea will even work. Could someone provide some insights into the Mirror_parabolic component, it's geometry, and it's orientation? Or does anyone know a better way to construct a Gö​bel mirror?

Any advice would be greatly appreciated!

Best,

Jordan​


-------------------------------------
Jordan M. Cox, Ph.D. (he|him|his)
X-ray Research Specialist

Materials Research Laboratory
Massachusetts Institute of Technology
77 Massachusetts Ave.
Building 13-4027
Cambridge, MA 02139​

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