I am running a simulation to obtain the bremsstrahlung spectrum produced by primary electrons injected into a target with solar atmosphere compositon. In order to obtain the spectrum for an ionized medium, I tried to set the value of the ionization potential in the MATERIAL-PROP card as the energy of an elementary plasmon (E = h vp = 0.00037 eV, assuming an electron number density ne = 10^14 electrons/cm3) instead of the average ionization potential for the neutral medium (I = 21.77 eV, as shown in the Fluka output file). However, the run just stopped giving the error message “STOP NONSENSE GAS”. Is there a way to circumvent this problem?
Thank you for your answer. I read the post you suggested, but still cannot figure how to resolve the issue. I am uploading the .inp and .flair files. I would be grateful for any further help.
this seems like a very interesting problem; however, the extreme environment you are describing cannot be simulated by a general-purpose code like FLUKA, as the physics involved deviates significantly from that used in the interactions of electrons with gases.
The reason you are seeing the error “STOP NONSENSE GAS” is that one of the models FLUKA uses (Sternheimer-Peierls model for diaelectric polarzation effects on ionization losses) requires the calculation of the ratio of the average ionization potential to the plasmon energy. The average ionization potential is assumed to be much larger than the plasmon energy for the model to be applicable. However, the electron density you have used to derive the plasmon energy (1e14 giving you 3.7e-4 eV) which you are then setting as the average ionization potential is different from the electron density one gets by looking at the material density you specified in the simulation. From the density in your input of 3.19e-5 g cm-3, I get an electron density of around 2e19 electrons/cm3, with a correspondingly higher plasmon energy (~0.2 eV). So the mean ionization field you set is far smaller than the the plasmon enegy calculated by FLUKA using the density you specified, and this inconsistency causes the error you are seeing down the line.
To reiterate, however, the problem you are encountering is due to the fact that FLUKA is trying to apply physics models that are not applicable in the regime of ionisation you are trying to simulate. I would suggest looking for a specialized code for this type of application.
Thank you, I remain at your disposal in case of any follow ups.
Thank you very much for your reply. It really helped to better understand the issue.
I tried to run the simulation by setting the ionization potential to 0.2 eV, but it didn’t work either. Running simulations with increasing values of the ionization potential I found that the minimum value to avoid the STOP NONSENSE GAS error is 3.7 eV.
Anyway, I am working on a solution using the FLUKA routine usrmed.f to multiply the weights of the electrons as they slow-down in the target by the ratio DEDXN/DEDXI, where DEDXI is the energy loss rate for an ionized medium and DEDXN is the energy loss rate for a neutral medium.