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Forum: Processes Involving Optical Photons
Re: Question Scintillation rise time (Martin Goettlich)
Date: 03 Nov, 2009
From: Gumplinger Peter <Gumplinger Peter>

Dear Martin,

> Is this crystal property implemented?

No, G4Scintillation only calculates an (exponential) 'time delay' and assumes an instantaneous rise time. And while the routine is set up to sample from a slow and a fast decay time simulataneously it doesn't account for a physical finite rise time. The code simply reads:

deltaTime = deltaTime - ScintillationTime * log( G4UniformRand() );

where deltaTime is first set to a random point/time along the step segment from where the scintillation photon is assumed to have originated.

> If not how may I do it?

I answer this with a question. How would you sample from a convolution of a finite rise-time with a finite decay time, e.g. a more realistic time distribution? If you know the code it takes to do that then the mechanism of introducing a rise-time in the material properties table is completely analogous to, for example, the "SLOWTIMECONSTANT". The G4MaterialPropertiesTable class is completely flexible in this. It simply associates a constant with a (any) character string. In your DetectorConstruction you assign the rise/decay time, for example:

G4MaterialPropertiesTable* myMPT = new G4MaterialPropertiesTable();

myMPT->AddConstProperty("SLOWTIMECONSTANT",10.*ns);

myMPT->AddConstProperty("RISETIMECONSTANT",0.5*ns);

and in G4Scintillation.cc (you need to modify the actual G4 source) you add code to retrieve this constant:

G4MaterialPropertiesTable* aMaterialPropertiesTable =

                                     aMaterial->GetMaterialPropertiesTable();

G4double ScintillationRiseTime = aMaterialPropertiesTable->

                                     GetConstProperty("RISETIMECONSTANT");

And you'd then have to replace the single line:

 ScintillationTime * log( G4UniformRand() );

with your more complicated sampling logic.

Let me know which approach to sampling from a more realistic time profile, with a rise and decay constant, you are taking. I am open to improvements of the G4 distribution.

Best regards, Peter

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1 None: Re: Scintillation rise time   (Martin Goettlich - 05 Feb, 2010)
(_ Feedback: Re: Scintillation rise time   (Michael - 12 Oct, 2010)
(_ Idea: Re: Scintillation rise time   (Michael - 13 Oct, 2010)
(_ None: Re: Scintillation rise time   (Michael - 15 Oct, 2010)
1 Warning: Re: Scintillation rise time   (Martin Goettlich - 29 Oct, 2010)
1 Feedback: Re: Scintillation rise time   (Michael - 29 Oct, 2010)
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2 Question: Re: Scintillation rise time   (Qiang - 10 Mar, 2016)
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