Different EP charging results from SPIS 6.0.4 and 6.1.0 and different cathode models

The issue is already reported in the GitLab under spis/num#4 (https://code.spis.org/spis/num/-/issues/4) but copied here for broader audience:

We are simulating an EP thruster plume (SPT100) together with a spacecraft (EP tutorial case from the SPIS trainings) with SPIS 6.0.4 and 6.1.0 and experience the following problem: The exactly same settings lead to different charging results between the two versions. See some examples here: Running the EP tutorial case in SPIS 6.1.0 leads to lower charging than in SPIS 6.0.4 (simulation was performed without any High Voltage device as the HV function was anyway broken in 6.0.4):


Running the EP tutorial case and removing the environmental plasma including all secondary emission as well as erosion leads to nearly complete loss of surface charging in both SPIS 6.0.4 and 6.1.0:


Running the EP tutorial case in SPIS 6.0.4 and changing the cathode model from adiabatic to SPT100 leads to complete change of the S/C charging (positive S/C charging instead of negative):


For this assessment, we used the EP tutorial case from the SPIS trainings (with the original global parameters from the tutorial case and just the surface groups redefined for the version 6.1.0). See here an image of the S/C model of the tutorial case:


Can this observed behavior result from a wrong simulation setting? Otherwise, it seems to hint for bugs in the 6.0.4 and 6.1.0 version. This issue might be related to the issue #3.

Thanks a lot for your support!

@sarrailh @sebhess did you get the time to have a look at this issue?
This is going to be critical for us too, we need to know which SPIS version we need to use in the coming months.