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

From: Vittorio Boccone <>
Date: Fri, 20 Jun 2014 23:49:59 +0200

Here's the trick...
I though I wrote it in my previous email but I didn't. My fault.

NTRACK tells you how many segments you have during this step. If you have
no magnetic field where you change the track segmentation by splitting up
segments this should be always 1 at the end of the step and 0 at the
beginning. NTRACK is therefore used as an index of the track position (and
dir. cosines) arrays. Personally I think I never used it.

You find a lot of information for tracking and following the particles in

To do what you say, you don't need to write anything in FLUKA but you need
to analyze/post-process correctly your event. I used Icode toghether with
some of the TRACKR variables to recontruct the history of the event.


On Fri, Jun 20, 2014 at 6:23 PM, Georgios Dedes <> wrote:

> 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
> routine.
> 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,
> George
> 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 JTRACK,
>> 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 Sat Jun 21 2014 - 01:10:19 CEST

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