Re: Problem with very small stepsize caused by transportation process?

Help: Forums, postings and threads

Forums, postings and threads

Click on the Forum title, e.g. on the "Forums by Category" page, to read a sequence of postings to the Forum and its threads all in one page. If you are only interested in one thread or the thread following a specific posting, click the thread or the posting, which takes you to a smaller page, which contains only the part you are interested in and may be easier to navigate.

Layout of the posting thread(s)

The posting threads can be shown with/without the text of the postings ("Inline depth"). In addition the depth of the thread can be controlled ("Outline depth"). For both cases several values are provided, which can be toggled. Note that the displayed values are those, which can be chosen, they do not correspond to the actual display status of the thread(s).

Add message

Add a new posting thread to this Forum

Show subscribers

Click "Show subscribers" to get the List of all subscribers, who receive e-mail from postings to this Forum, if they have not explictly unsubscribed from a posting thread. This includes:

Subscribers to the forum
Explicit subscribers to the posting or any of its ancestors
The author of the posting (if he has not unsubscribed)
The authors of any ancestor posting (if they have not unsubscribed)

Some browsers display old pages from the cache

Some browsers (e.g. Firefox) display a page from the cache even though the page has been updated. As a result, one may not get the latest messages in the forum's outline or the logon ID of the previous session appears on the upper right corner. If one suspects that he or she does not get the latest content of a page, try clearing up the personal data from the browser's cache as the following:

Tools -> Clear Private Data -> Clear Private Data (from browser Firefox)

Tools -> Delete Private Data (from browser Opera)

then reflesh the current page to get the latest content.

Details on "Inline depth" and "Outline depth"

Threads and the follow-up messages are numbered. There is one line per posting, normally starting with the posting number. The URLs of a posting and its responses reflect the depth of the follow-up postings. Watch the URLs to see how this is done. Depending on the chosen display options, the thread-display may be incomplete; the number of messages at the next level is, however, displayed, e.g. "…3 message(s)". You may not see all contributors unless you choose "All".

Messages are "chained" if there are only replies at the first level, i.e. 1/1.html, 1/1/1.html etc. In case of "chained" messages the message number is replaced by the icon and there is no indentation.

Inline: Display the subject line only or also the text of the posting(s); for the choice "All" the "Outline" choices are switched off.

Argument Default value Alternative Comment

1 0 1 no text / full text of posting

2 1 All text for level 1 only / text for All postings

Argument	Default value	Alternative		Comment
1	0	1		no text / full text of posting
2	1	All		text for level 1 only / text for All postings

Outline: Choose the depth of the posting thread, successive toggle controls provide increasing detail.

Argument Default value Alternative Comment

1 2 1 2 levels / 1 level (original posting)

2 3 2 3 levels / 2 levels

3 3 All 3 levels / all levels (all postings)

Argument	Default value	Alternative	Comment
1	2	1	2 levels / 1 level (original posting)
2	3	2	3 levels / 2 levels
3	3	All	3 levels / all levels (all postings)

[ I started writing this before you last posting - but I have now read it.]

Your problem is unusual, and could suggest a difficulty in the Navigator or in your setup. My first suggestion would be to run overlap checking. Since you report doing this already, I will provide a different suggestion. [ However, if you can try to check for overlaps a second time, using a different method, it could help too. ]

Could you please see whether you can reproduce the problem when locating a point by yourself with just the Navigator.

From your output I see that the difficulty is at

 Position - x (mm)   :   -89.70796591921498  
 Position - y (mm)   :   -63.48666293803226 
 Position - z (mm)   :             -285.232

Can you call the Navigator at this point, (you can get its pointer from the G4TransportationManager), using LocateGlobalPointAndSetup ? I suggest to call it repeatedly and compare its output.

Then add the direction, which from your print out appears to be
 Momentum Direct - x :  -0.9805329125797901 
 Momentum Direct - y :   0.1807490143955495 
 Momentum Direct - z : -0.07671376110471373

From the values of the position, it is my guess that there is a boundary
exactly at this z value:
 Position - z (mm)   :             -285.232
Can you confirm whether the point is at a boundary of one of the
TrdLayer volumes at this point ?

If so, it would be very useful to create a custom sub-class of G4SteppingVerbose that prints out the copy number of the current TrdLayer (and potentially the parent volume's copy number as well.) This way we can check whether it is confused by bouncing between different copies at their interface.

After this, please try to call the Navigator's ComputeStep method yourself. If it returns zero, you are seeing the same problem.

I suggest to repeat
    Locate( point, direction, ...
    step= ComputeStep( point, direction, ...
    point += step * direction; 
a few more times (say 20 times in a loop) to confirm that the problem
is with Navigation, not the field.

The code for propagating in a magnetic field should take care for difficult cases, where it can be unclear what volume a track is actually crossing. In this case, though, it appears that it is the Navigator which is having difficulties.

I noted that you said that "" a particle should never really enter a "TrdLayer" volume explicitly because the daughter volume "TrdRadiator" in each "TrdModule" fills the upper part of the layer completely. ""

This seems to indicate that it is experiencing significant difficult at this level. What type of volume is a 'TrdModule'? A box, a tubs, or other ?? Also what is the TrdRadiator ?