[Gate-users] Simulate energy spectrum of 22Na source measured with LYSO

[Pedro Correia]

Dear Gaters

I’m trying to simulate the energy spectrum of a 22Na radiation source measured by a LYSO scintillator. 


The typical approach should be the use of the digitizer, with all the parameters of the LYSO defined in the Materials.xml, wright?
However, for my application I want to evaluate the optical losses of my system, that uses a dual ended readout system for each LYSO scintillator, i.e. a PMT reads each polished end of the LYSO, while the other four lateral surfaces are teflon wrapped. 

I’ve tried to use the optical photons produced by each interaction inside the LYSO, with an yield of ~28000 photons/MeV:
	- At the two ends, I defined two perfect_apd surfaces, in which all the incident photons are detected
	- Until now, I’ve considered 100% efficiency in the photon detection
	
After the simulation, I used the opticaladder module of the digitizer in each of the two PMTs. I finally get two energy spectrums histograms in my Root file (each for each PMT detector). I sum the two spectruns, in coincidence, so I was expecting to observe the 22Na source after that, but nothing similar to that appears in the spectrum.

Can someone tell me if this approach is possible (obtain the source spectrum simulating the optical photons detections)? In affirmative case, the problem should be in my code. Otherwise I need to try a different thing. 


Best regards, 

Pedro Correia, PhD student, 
University of Aveiro, Portugal