Hi Kai,

The Help File about NSDD can be found under The Optimize Tab (sequential ui mode) > Automatic Optimization Group > Merit Function Editor (automatic optimization group) > Optimization Operands by Category > Non-sequential Ray Tracing and Detector Operands.

In short, prior to calling any subsequent NSDD operand, you need a call to a NSDD which clears all detectors. Since all detectors need to be cleared, you also need to run a raytrace. In your Merit Function you should have:

1. NSDD to clear all detectors
2. NSTR to run a raytrace
3. NSDD to retrive detector values/metrics

I’ve shown an example in the screenshot below:

For the standard deviation you need to specify the Det#, 2 in my case, the Pix#, -4 as you mentioned, and the Data is 0 for flux, 1 for flux/area, 2 for flux/solid angle pixel, 3 for normalized flux, 4 for absorbed flux, and 5 for absorbed flux/area.

Does that make sense?

Take care,

David