Re: [fluka-discuss]: [fluka-discuss] neutron fluence spectrum

From: Angel <>
Date: Mon, 17 Dec 2018 15:45:03 +0200

Hello George,

Thank you very much for your kind reply! I am probably missing something
since I get different results by using the two cards. Is this due to poor
statistics or my misunderstanding on how to use the cards? I have attached
my .inp file. In order to compare the outputs of the two cards I compare
the results outputted, respectively, in bins 32 and 33.

Best regards,

> Hello Angel,
> You can use either in this case. The difference is that USRBDX scores
> double differential (energy and angle) particle distributions across a
> boundary surface which gives
> results per cm2, per GeV, per steradian, per primary, while USRTRACK
> calculates differential fluence as a function of energy by scoring
> track-length in a given region and gives results per cm2, per GeV, per
> primary. The scoring lecture from FLUKA beginners courses provides summary
> descriptions of the two
> One thing to keep in mind when scoring low energy (<20 MeV) neutron
> spectra: the transport of low energy neutrons in FLUKA is performed
> through a multigroup treatment, for which the neutron energy is not
> exactly defined but belongs to one of the 260 predefined intervals of the
> cross section library. Because of this, whether you use USRBDX or USRTRACK
> to score energy spectrum, energy binning is forced to match the 260 energy
> intervals regardless of what was requested by the user.
> For very helpful information regarding scoring neutron spectra I would
> also recommend reading the replies to the following thread:
> Best regards,
> George
> ----- Original Message -----
> From: "Angel" <>
> To: "FLUKA Discussion List" <>
> Sent: Saturday, December 8, 2018 6:17:31 PM
> Subject: [fluka-discuss]: [fluka-discuss] neutron fluence spectrum
> Dear FLUKA experts and users,
> I need to obtain the neutron fluence spectrum at different depths inside a
> concrete wall. The manual points that I can use the USRBDX or USRTRACK
> card for the purpose. What is the difference between the two cards? Using
> the first one I can choose to score the neutron fluence on a surface
> passing in both directions or just in one. The second gives me neutron
> fluence in a given volume. Which one would you advise me to use? Are these
> cards the right ones to use?
> Best regards,
> Angel


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Received on Mon Dec 17 2018 - 16:25:04 CET

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