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On Thu, 17 Jul 2003, Lei wrote: > *** Discussion title: Event and Track Management > Email replies to PublicHyperNews@slac.stanford.edu must include: > In-Reply-To: <"/eventtrackmanage/93"@geant4-hn.slac.stanford.edu> > Subject: ...change this to be about your reply. > > Hello, > > I am a first-time user of Geant4. Now I have finished the installation > and begin to build up my first simulation model: simulation of CT scan. > This model is pretty simple. I am using water cylinder as the phantom > and a lead detector to get the projection data. The lead detector is set > as the sensitive detector and the world volume is a big box containing > air, phantom and detector. At present, I have got the projection data, > but need to separate them into primary and scatter, hence, get the > primary-to-scatter ratio. I have hard time in finding a way to do it, > although I know there are many. Acturally, I think I haven't quite > understood several concepts of Geant4. Here are my questions and > confusions. > > 1. What's the difference between Track and Step? My Understanding is > that they contain different info of the interaction of the object and > particle but they are generated at the same time in the Geant4 process. > Is this correct? What kind of user-defined action should be set in > "XXXXSteppingAction" and what in "XXXXTrackingAction"? Which one will be > called first by the G4EventManager during one event process? > Both classes are used for tracking: G4Track includes extended description of a particle, simulation is performed step by step, which is reflected in G4Step. The purpose of actions described in the manual and in the comments to the interfaces. > 2. In the user guide, it says the XXXXStackingAction will push the > generated tracks into different stacks, so simulation will be done > accordingly. Does it mean after every track is generated, it will will > be classified by StackingAction? What time will the tracks be poped by > the G4EventManager (or somewhat else)? Those tracks in fWaiting stack > will be pushed into fUrgent when fUrgent is empty. What time will > fUrgent be empty? After the event is finished or one step is finished? > When event is finished all stacks expept "suspended" are empty. > 3. What is the rule of Track ID number? If the Track ID is 0, does it > mean the particle is primary definitely? According to my on hand > simulation results, it seems not true...So, what info can I use to > identify the primary particle in my CT simulation model? > For primary particle ParentID = 0 VI
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