RE: [fluka-discuss]: TOTAL FLUENCE

From: riya dey <riyadey_at_barc.gov.in>
Date: Fri, 29 Jun 2018 12:14:39 +0530

Dear Expert,

I changed the cloud media from air to vacuum. Still the total fluence is
different for different energy. Actually, with increasing energy the total
fluence in the detector is decreasing which is not expected if the photons
are propagating in vacuum.

For example, when energy = 0.1 MeV , total cumulative fluence (two way
scoring) = 3.33E-7 # per cmq per primary , while when energy = 1 MeV, total
fluence (two way scoring) = 5.03 E-8 # per cmq per primary.

Even with 1E+8 histories, although the statistical error is very less, still
the two values are different. The sample file is attached here.

-----Original Message-----
From: owner-fluka-discuss_at_mi.infn.it [mailto:owner-fluka-discuss_at_mi.infn.it]
On Behalf Of Francesco Cerutti
Sent: 28 June 2018 23:12
To: riya dey <riyadey_at_barc.gov.in>
Cc: FLUKA discussion <fluka-discuss_at_fluka.org>
Subject: Re: [fluka-discuss]: TOTAL FLUENCE


Dear Riya,

I'd share your expectation if your photons were travelling in vacuum, but
their interactions with your air hemisphere depend on their energy.

Also, make sure that the statistical error of your fluence values is
reasonably low.

As a side note, in your source routine, when typing any real number put it
in double precision (e.g., 1.0D0/3.0D0, or - in this specific case - the
available FLUKA parameter ONETHI).

Kind regards
Francesco

**************************************************
Francesco Cerutti
CERN-EN/STI
CH-1211 Geneva 23
Switzerland
tel. +41 22 7678962
fax +41 22 7668854

On Wed, 27 Jun 2018, riya dey wrote:

>
> Dear FLUKA Experts,
>
>  
>
> I was modelling a hemispherical cloud source ( radius = 10 m)  
> emitting photons isotropically. Below the cloud, a detector is placed
> at ( 0,0,200
> cm) with radius R= 200 cm. Now, using USRBDX surface crossing fluence
> rate is estimated in the detector. If we change the energy emitting
> from the source , lets say for 0.1 MeV , 0.5 MeV , 1 MeV , then
> although the fluence distribution with energy is different , the total
> no of particles crossing the detector surface should be nearly same.
> But total fluence from  FLUKA results are different for different energy.
>
>  
>
> What might be the reason for this ?
>
>  
>
> The input files for 0.1 MeV is attached here. The outputs (sum.lis)
> for 0.1 MeV and  0.5 MeV are :
>
>  
>
> Total fluence per cmq per primary for 0.1 MeV is =      3.59 E-7
> (one-way
> scoring)             ,  for 0.5 MeV is =  4.73 E-8 (one way scoring)
>
>  
>
>  
>
> With regards,
>
> Riya Dey
>
>
>



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Received on Fri Jun 29 2018 - 17:05:20 CEST

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