Re: [fluka-discuss]: following particle in every step (NTRACK vs NTRUCK)

From: Georgios Dedes <>
Date: Fri, 20 Jun 2014 18:23:57 +0200

Hi Vittorio and rest of FLUKAers,

thanks for the reply. As you recommended, I took another look into a
minimally modified mgdraw, trying to understand what I get. I attach the

In line 70, I basically merged some of the output that was active in the
default mgdraw.
In line 295 (usdraw), I dump the same info as in line 70.

So my conclusions/questions so far (I attach the file coming from MGDRAW
and USDRAW):

- using the index 0 for the XTRACK, YTRACK, ZTRACK gives me the starting
location of the step while if I use 1 they give the end point of each
step (which alternate of course, the end of the previous step is the
start of the next one). So far so good.

- in the mgdraw_Output I seem to be getting all the steps (I can see the
primary having a starting step location exactly where the source is
created), while in the usdraw_Output only a subset of them. As mentioned
in the online manual, usrdraw is called after each particle interaction.
Are the missing entries (as compared to the mgdraw_Output) due to
continuous energy loss for which the usrdraw is not called?

- as far as it concerns NTRACK, in the default mgdraw writing to the
mgdraw_Output, NTRACK is always 1. When I access the same info from the
usdraw it's always 0 for the primary protons and 1 for the few electrons
I got (I used only 2 protons of 1GeV). So I still don't understand
NTRACK. It is definitely not incrementing for each particle step, but it
is also 0 when accessed from usdraw. Any idea why?

- a last question, which was actually the source of all my troubles. How
can I get from the mgdraw, which follows every particle through every
step, the position of generation of secondaries? Initially I thought
that I could use the NTRACK, which I wrongly thought that it would
increment in every step, along a particle trajectory

Thanks for the feedback,


Dr. Georgios DEDES
Ludwig-Maximilians-Universit√§t M√ľnchen (LMU)
Medical Physics Chair (LS Parodi)
Am Coulombwall 1
85748 Garching
Tel:+49 (0) 89 289-14022
Fax:+49 (0) 89 289-14072

On 06/18/2014 11:11 PM, Vittorio Boccone wrote:
> Hi George,
> mgdraw is a very powerful tool, but I see you already know what are
> the different ingredients.
> If you miss the successive steps I guess you activate it using the
> wrong WHAT(3) in the USERDUMP card, or your threshold are too high and
> the particles are "absorbed" in loco.
> I would suggest you to play around with the default mgdraw.f and maybe
> to post your code. It's a bit complicate to tell you what is wrong if
> I can't see what you do.
> I would leave NTRUCK aside for the time being.
> Best
> On Wed, Jun 18, 2014 at 3:12 PM, <
> <>> wrote:
> Dear FLUKAers,
> I'm trying to develop a short user routine (in mgdraw) for custom
> scoring and I got the following questions:
> - Shooting 100MeV protons in a water target and printing the
> mostly what I expected to see when following my particle step by
> step along its trajectory. Nevertheless, the NTRACK (and the
> MTRACK as well), seems to be always 0. If the meaning of of the
> track segment is what I thought, shouldn't it be incrementing
> along the trajectory?
> - Then I see that there is also the variable NTRUCK, which
> represents the number of step points. When I print this in mgdraw,
> it's also always 0 for my primary protons. So same question as
> above. In addition, I am not sure that I understand the difference
> between the track segment (~NTRACK) and the step (~NTRACK)
> - What I ultimately had in mind was to follow the particle in
> every step and -for example- store the newly generated secondary
> particle position (the starting point of the first track segment
> or step)
> Obviously I am missing something important here, so I would be
> grateful if you can help me on this or point me to some reference
> that clarifies it.
> Thanks in advance,
> George

Received on Fri Jun 20 2014 - 20:14:54 CEST

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