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Keywords: hits nested SD volumes daughter sensitive detector volumes
Forum: Hits, Digitization and Pileup
Re: Question daughter volumes not sensitive but should be pointed to? (Blair Smith)
Date: 08 Nov, 2005
From: Makoto Asai <Makoto Asai>

Let me confirm again that a SD pointer do NOT propagate to the daughter
volumes. This restriction came from the case where absorber layers 
(they are not sensitive) are dipped in liquid Argon calorimeter (liquid
Argon is sensitive to collect all energy deposition in it).

On the other hand, it is perfectly allowed to set the same SD object
to both the mother and the daughter volumes. In this case, ProcessHits()
method of your SD will be invoked with a G4Step which has a touchable
recording all the geometry hierarchy from the immediate PV (level 0) to
the top (world volume).  

Please note that it is always the case that a SD object assigned to 
the immediate PV (level 0) is invoked, and any SD objects that might be
assigned to (grand)mother volumes are not invoked. In other words, there 
can NOT be any daughter volume below level 0 for touchable that is 
provided along ProcessHits() method.

> It is still true that when a daughter volume's boundary
> is crossed the SD calls ProcessHits() for the parent volume.  I see 
> that in the log output. But within ProcessHits() it seems I loose
> the information about any daughter volumes, unless I inspect by 
> looking at the hit position and infer the deepest volume at 
> that point by brute force inspection.

Here I do not understand what you meant. Even if a step is limited by
the daughter volume's bounday, the step belongs to that daughter
volume and thus the SD associated to the daughter volume is invoked.
 
> I will instead probably take 
> the easy route of simply making all the daughter volumes sensitive
> as needed, creating and maintaining of course more hit collections, 
> which is a slight pain but not too burdensome.

As I wrote above, you can assign the same SD object to both mother
and daughter volumes. Then you have only one hits collection.

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1 Note: Re: daughter volumes not sensitive but should be pointed to?   (Blair Smith - 08 Nov, 2005)
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