Re: Problem in choosing the right USRDBX fluence/current flag

From: Stefan Roesler <>
Date: Thu, 7 Jan 2010 18:52:53 +0100

Dear Tsviki,

If you would like advice on your specific problem please post the input,
any user routine, as well as the used cross section data.

Thus, I can only make the following, more general comments:

- It would be more appropriate to score fluence with USRTRACK inside the
  region in which you score with RESNUCLE. Depending on the tickness of
  your target, the incident fluence gets attenuated, the spectral shape
  changes and secondaries are produced which may create also nuclides.

- Use exactly the same cross sections as used in or predicted by FLUKA if
  you aim for identical results.

- If fluence from USRTRACK is folded offline with the same cross sections
  as used in or predicted by FLUKA, and assuming that nuclide production
  is approximately homogeneous in the target volume, you will get the same
  numbers as with RESNUCLE. This has been done before several times.

- Assuming normal incidence on the boundary, fluence and currect scoring
  must give the same spectrum. I can only tell you more why it doesn't in
  your case if I see the input.

Best regards

On Thu, 7 Jan 2010, Tsviki Hirsh wrote:

> 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

Stefan Roesler
CH-1211 Geneva 23
Phone:  +41-22-7679891
Fax:    +41-22-7669639
Received on Thu Jan 07 2010 - 22:07:54 CET

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