XMM Users' Handbook

   
RSim - The RGS Simulator

RSim consists of two major parts, RGASim and RFCSim. The former simulates the physical properties of the RGAs, the latter those of the RFCs.

RGASim represents the continuation of the ray tracing that is performed by MSim. Multiple reflections are allowed, so that every ray that enters RGASim either leaves the module or is absorbed. Those rays leaving the RGAs in the direction of the RFCs are picked up by RFCSim and projected on the 9 CCD surfaces.

The features currently contained in RGASim are:

• 3-D model of the grating array

• Grating positioning and alignment errors

• Exact geometry of the actual grating arrays

• Changing line density spacing of grooves as a function of the x coordinate

• Random errors in line density variation

• Grating efficiency model

• Multiple reflections in between grating plates

• A physical model for scattering by micro-roughness of the gratings

• Positioning of the whole RGA relative to other subsystems

• Gaps between the CCDs

Rays can be produced in individual spectral orders in order to speed up the calculations.