Problem in choosing the right USRDBX fluence/current flag

Dear list,

We have simulated a production of an isotope from ISOLDE fast spallation
neutron source.
The activation was calculated using three methods,
1) Getting the neutron fluence spectrum with USRDBX and then integrate
with the cross section.
2) Getting the neutron current spectrum with USRDBX and then integrate
with the cross section.
3) Doing the "full simulation" using RESNUCLE.

The target is a simple cylinder positioned inside the neutron flux.

The problem is that we are getting different results using each one of the
methods, even though we have used an identical cross section in the calculations.
The production numbers were (all scaled down):
1) 4.8 using fluence
2) 2.4 using current
3) 2.8 from RESNUCLEI

Which of the above is the correct? What is the reason for the differences?

Thank you,
Best Regards,
Tsviki Hirsh
Weizmann Ins. of Science, Israel
Received on Thu Jan 07 2010 - 15:21:11 CET