Problem 2211

Summary:	Cannot reproduce published thermal neutron on Gd IC e- spectrum with v.10.4.0+
Product:	Geant4	Reporter:	Jan Christoph Terasa <christoph>
Component:	processes/hadronic/models/de_excitation/photon_evaporation	Assignee:	dennis.herbert.wright
Status:	RESOLVED FIXED
Severity:	normal	CC:	christoph
Priority:	P4
Version:	10.4
Hardware:	All
OS:	All
Attachments:	file containing plots, reference figure and code.

Description Jan Christoph Terasa 2019-12-21 02:17:54 CET

Created attachment 598 [details]
file containing plots, reference figure and code.

Hi,

I have tried to reproduce the spectrum from IC e- when shooting neutrons with 25 meV at a Gd slab, as found in https://doi.org/10.1007/s10967-014-3083-4. With Geant4 v10.3.2 it worked with G4USE_ONLY_PHOTONEVAPORATION=1, but with v10.4.0 and newer I am no longer able to reproduce the spectrum.

I attached plots for the different versions, as well as the reference figure from the paper. I also included the source code I run. As can be see, only v10.3.2 can reproduce the measurement shown in the attached PNG file.

Am I missing to enable/disable some more options since v10.4.0? Is this known? Or is this a bug in v10.4.0+?


kind regards,
Christoph

Comment 1 dennis.herbert.wright 2020-01-22 22:40:28 CET

Looking through the code, it appears that the environment variable G4NEUTRONHP_USE_ONLY_PHOTONEVAPORATION must be set to 1 

It looks like this is now the only way to invoke the photon evaporation code, so try setting this before you run your application.
   
I cannot find any occurrence of G4USE_ONLY_PHOTONEVAPORATION in the latest Geant4 versions; it may have been removed in 10.4 but I can find no documentation for that.