RE: fluence spectra

Dear Leena,

I'm afraid you did not fully get the spirit of the helpful Mario's
suggestion. Unfortunately your USRTRACK setup is conceptually nonsense and
your geometry is affected by a few mistakes.

Starting from the geometry:
- you include in the AR2 region, as additional zones, the volumes inside
the cylinders B17, B15, and B11, which are then defined as independent
regions (HO1, HO2, and HO3, respectively).
- you forget to remove from the same AR2 region the bodies from T2 to T6,
which then define, according to the Mario's advice, the regions TR2 to TR6
representing the target segments (by the way, when you define these
segments, there is no point in subtracting every time the other five
cylinders from the selected one, since they do not overlap; furthermore,
it would be better to introduce just one infinite cylinder of radius 4cm
and cut the different segments through XYP planes).
- you forget to remove from the same AR2 region the B9 body, coinciding
with the KPT region.
- in the VO3 region, "| B7" should be intended as "- B7", but can even be
fully skipped since the subtraction is already performed by "-B6".

As for your scoring structure:
the idea of Mario was to get proton spectra as a function of depth in
water, that is one 1-fluence spectrum for each target segment at
increasing depth.
So you applied the USRTRACK detector to your six regions TR1-TR6, so far
so good. But you asked for *one* energy bin, whereas 1-fluence spectrum
means differential fluence as a function of particle (proton) energy and
cannot be made by one point only. Moreover, instead of looking always over
the relevant range (let's say 0-65MeV; then of course the actual upper
limit goes down for the deeper segments, since the protons are slowed
down), you select only a portion of this range, spanning an interval at
larger energies for increasing depth (?! of course you will never get
60MeV protons in the last segment).

Finally, what you get in the output file through the SCORE card is the
number of inelastic collisions (per beam particle) undergone by protons in
every region. This is somehow related to the proton fluence in every
region (through the interaction cross section, which however is a function
of proton energy) but still is not differential information.

For the 2-fluence spectra you mentioned in your first message, if the
meant second quantity is the proton angle, you can apply the USRBDX
detector at the different segment boundaries.

All the best

Francesco

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

On Wed, 28 Jul 2010, L.Al-Sulaiti_at_surrey.ac.uk wrote:

> Hello Mario
>
> Thank you very much, this was helpful.
> I have divided my water target volume into 6 regions for 6 USRTRACKs each
> with one energy bin. However, I could not load them in FLAIR. Instead, I
> have uesd the standard output file (events by region scoring) to observe the
> results. Unfortunatley I have found firist region result only while the
> others were zero. Please refer to the attached input file and tell me where
> the error is.
> I have also tried to divide the initial proton energy to 1/6 for each
> USRTRACK. Please let me know if this was correct. Also would you please tell
> me if there is away to see the output result in FLAIR since I have to do it
> for so many regions.
>
> Thanks once again and best regards
> Leena
> ________________________________________
> From: owner-fluka-discuss_at_mi.infn.it [owner-fluka-discuss_at_mi.infn.it] On Behalf Of Santana, Mario [msantana_at_slac.stanford.edu]
> Sent: 23 July 2010 04:07
> To: Al-Sulaiti L Ms (PG/R - Physics)
> Cc: fluka-discuss_at_fluka.org
> Subject: Re: fluence spectra
>
> Laena,
>
> In your input file you are scoring PROTON fluence in a R-PHI mesh centered
> at x=0, of radius 4 and depth (z) 3.2 cm. The fluence is the density
> of track-lengths for your protons, so the units are
> cm/cm^3=cm^2. Now, of course FLUKA expresses the results per primary
> particle. So 1/cm^2/starting_proton. You need to multiply the result by the
> number of protons per second that you shoot into your target.
>
> If you want to have the spectra of your fluence then use USERTRACK. In that
> case you will obtain the differential spectra dfluence/dE (units are
> 1/cm^2/GeV/starting_proton) for the energy grid (linear or logarithmic) that you request, but you will not be able to simultaneously sort the results in a
> 3-D grid (like with USRBIN). Instead, you will have to request your spectra
> for the PROTONS that cross a given region of your geometry. I suggest that
> you split your volume in several disk regions and that you use several
> USERTRACK cards associated with those regions. Then you could load all those
> in FLAIR (or gnuplot) to see how your spectrum changes with the depth.
>
> In case of further doubt I suggest you to read this:
> http://www.fluka.org/fluka.php?id=n_onl&sub?
> http://www.fluka.org/fluka.php?id=n_onl&sub?
>
> Mario
>
Received on Sun Aug 01 2010 - 12:44:59 CEST