[fluka-discuss]: RE: Tracks in usdraw

From: Anton Lechner <Anton.Lechner_at_cern.ch>
Date: Thu, 25 Sep 2014 16:46:54 +0000

Dear Helga,

Actually, X/Y/ZTRACK are arrays with indices ranging from 0 to NTRACK, where NTRACK indicates the number of track segments. X/Y/ZTRACK(0) gives you the starting point coordinates, and X/Y/ZTRACK(NTRACK) the end point coordinates, while the entries in between give you the coordinates of intermediate points. In many cases you will get NTRACK=1, ie. there is only one track segment, however if you track for example a charged particle in a magnetic field, you can get intermediate points. Also note that in this case, one has to add up the length of sub-segments to get the entire (curved) track length.

You can access all the elements of X/Y/ZTRACK as described above in the main MGDRAW entry (i.e. at the beginning of the routine). However, the USDRAW entry in MGDRAW is only called after point-like interactions (e.g. delta-ray production, inelastic nuclear collisions etc.) and the TRACKR common is re-initialized before the call to USDRAW. Hence, you don't have anymore the starting point available in TRACKR (actually, X/Y/ZTRACK(0) now contains the end point). Since USDRAW is called only after point-like interactions, do you really need information about step starting point inside USDRAW?

Cheers, Anton

From: owner-fluka-discuss_at_mi.infn.it [owner-fluka-discuss_at_mi.infn.it] on behalf of Helga Holmestad [helga.holmestad_at_cern.ch]
Sent: 25 September 2014 14:22
To: fluka-discuss_at_fluka.org
Subject: [fluka-discuss]: Tracks in usdraw

Dear fluka experts

I am trying to write my own implementation of usdraw in mgdraw.f. For each track I would like to find the start and endpoint. I think that the relevant variables are xtrack,ytrack and ztrack in the common block TRACKR. But this is only the endpoint of the track. How can I get both the start and end point.

Kind regards,
Received on Thu Sep 25 2014 - 20:09:52 CEST

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