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Question Re: Sensitive Detector and daughter volumes 

Keywords: hits daughter volumes touchable history handle sensitive detector daughters
Forum: Hits, Digitization and Pileup
Re: Question Sensitive Detector and daughter volumes (I Cornelius)
Re: None Re: Sensitive Detector and daughter volumes (Makoto Asai)
Date: 05 Nov, 2005
From: Blair Smith <>

Perhaps contrary to Makoto's old reply to this question I was just 
told by another G4 user that sensitivity does propagate to daughters, 
in the following sense:

If I set my "logicBox" volume as a SD and this volume has a duaghter 
"logicCal" say, then whenever a particles enters a physical placement 
of the parent, say "physBox" then ProcessHits() get's called 
with a touchable history pointing to the "physBox", but then when the 
inner boundary is crossed and the particle enters the "physCal" region
then ProcessHits() gets called again this time with the touchable 
history handle points to "physCal". See the ASCII diagram below.  
So one can indeed tell when a hit occurs in a daughter region of 
your logical volume.  The daughter is not "sensitive" as Makoto Asai 
mentioned, but the user I conferred with told me that sensitivity is 
not an issue because the daughter will get picked up by the touchable 
history handle when particle collide inside the daughter.

  world           _______________      |
                 |   physBox    |      |
                 |  __________  |      |
       p -->     |  |physCal |  |      |
                 |  ----------  |      |
                 |              |      |
                 |--------------|      |

Now neither I nor the user I spoke to is an expert, and I am only 
beginning to write my G4EventAction class to see if my readout does
indeed correctly pick up all daughter volumes that are hit. So it 
remains to be seen whether or not I have interpreted Makoto's answer 
correctly, but my concern was that at first blush it seemed like 
a slightly misleading answer, or perhaps I am completely 
misinterpreting both the anser and the question by Cornelius?

In any case, the problem I am trying to address is how to 
use ProcessHits() efficiently.  I want some readout for 
an entire enveloping volume that is not electronically sensitive in 
the real world laboratory, but in simulations ai want to know 
the energy deposited in the entire structure (say for heating and 
count efficieny tallying analysis), in addition to  the electronic
regions that would register hits in the lab device that I'm modeling.

So rather than have execessive classes to maintain I wanted a single 
pair of G4VHit and G4SensitiveDetector classes to handle both 
types of regions.   I can perform different readout depending 
on the type of volume that gets hit in EndOfEventAction() and it
does not bother me if the same hit collection members get stored 
for both regions, even though some of the information will be 

As some have suggested I my be better off writing at least two G4VHit 
classes, one for the electrically sensitive regions and one for the 
surrounding structures?  But in either case I should be able to 
identify what daughter volumes get hit using the touchable history 
handle is that correct? 

It's of some concern because my surrounduing structure will contain 
daughter volumes that are also electrically sensitive.  I do not want
to store hits to electrically sensitive regions twice though, so it's 
important that I add hits in a non-redundant way in the two 

If any experts see a problem or issue with this proposed strategy 
then I'd love to hear from them.


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