Problem 1006

Summary: Behavior of NeutronInelastic changed since Gean4.8.2p01
Product: Geant4 Reporter: Gonchar Maxim <gonchar>
Component: processes/hadronicAssignee: dennis.herbert.wright
Status: RESOLVED FIXED    
Severity: normal    
Priority: P5    
Version: 9.1   
Hardware: PC   
OS: Linux   
Attachments: example application
script for comparison

Description Gonchar Maxim 2008-03-17 11:39:38 CET 
Geant versions:
4.8.2p01
4.9.0
4.9.1
4.9.1p01

OS:Linux Debian/testing.

Behavior of NeutronInelastic changed since Geant4.8.2p01. On an older versions (4.9.*) it gives another result.

The example application is attached (it needs ROOT installed). It simulates neutron propagation in cube, filled with oxygen. It simply saves delta Energy for neutron on each step and plot histogram for energy loss due to inelastic scattering. 

The effect is seen only when initial neutron energy is more than 20 MeV (21 in example). Energy loss per step distribution have a large peak on low energy for g4.8.2p01, when g4.9* doesn't have it.

Step-by-step:
- Compile example with G4.8.2 and with G4.9.1.
- Run them separately with test.mac (be sure that initial energy is 21 MeV)
- Compare result files with root macros compare.C
- Look at energy loss per step distribution.

I'm not sure if it is an error, but I can not find anything about it in Release Notes.

Thank you.

regards, Maxim Gonchar.
Comment 1 Gonchar Maxim 2008-03-17 11:41:28 CET 
Created attachment 21 [details]
example application
Comment 2 Gonchar Maxim 2008-04-02 10:25:18 CEST 
Created attachment 25 [details]
script for comparison

Script that compares output of example application.
Sorry, I forgot to attach it.
Comment 3 dennis.herbert.wright 2011-03-07 16:48:44 CET 
The correct behavior is that there should not be a large peak at low energy.
This problem was actually fixed in Geant4 9.0, according to the 9.0 Release Notes.  Please see under  
Hadronic Physics
  Bug fixes in LEP models.