Learning Forum

[Romil Audhkhasi]

Hello,

I have a very basic test simulation in which I am simulating free space with the TFSF source and calculating the absorption and scattering cross sections (see image 1). I know that results normalized to source power are not useful for TFSF sources but for this simple case, I looked at the fraction of source power absorbed and scattered by free space. I would expect both these quantities to be 0, as there are no absorbing or scattering structures in the setup. However,. I got a scattered power fraction close to 0.5 for all wavelengths in the 8 - 12 micron range. Apparently, for the scattering monitor box, all monitors except the top z monitor give a flux close to 0. This top monitor however has a flux close to -0.49 for all wavelengths (image 2). I would like to understand if I am misinterpreting the results.

[Guilin Sun]

You are right that for empty simulation without scatter, both absoprtion and scattering should be very small if not zero (due to discrete errors).

It seems your monitor maybe collated with the TFSF edge. Please make sure no monitor touches the TFSF grey region, and do the test again. If transmission is still large, please send more screencopies of the settings. 

YOu can enable the view grids to see where those monitors are located. 

Make sure the simulation is terminated after reaching autoshutiff min.

[Romil Audhkhasi]

Thank you. I was able to resolve this issue by making the scattering monitor box larger.