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Question Scoring Parallel World Problem2 

Forum: Biasing and Scoring
Date: 14 Jun, 2010
From: Ibrahim <Ibrahim>

Hi,

In my first program I used Gd2O2S detector (Gd2O2S scintillator screen) for X-ray Imaging purpose. It works well. I divided Gd2O2S detector into 1024 x 1024 pixels and I irradiated it with a beam of X-ray and I could image any object. For instance, a box made of Al. But in this case of X-ray imaging, I used the direct detection of X-ray (direct X-ray Imaging. That mean no optical photons are generated inside the scintillator are therefore they are not taken into account. My Simulation setup is the following:

Gd2O2S detector whose dimension is: 20.48 x 20.48 x 0.03 cm3 20.48 cm is the width and length of the detector and 0.03 cm it the thickness of the Gd2O2S screen.

Please, have a look on the image1 attached herewith to see the simulation setup. Gd2O2S detector is yellow and the object to be imaged is a blue box.

In this program, I used the scoring parallel word in order to overlay Gd2O2S detector and then collect the energy deposition in each pixel of the detector. This was my first program and it works well!

But now, I would like to detect indirectly the X-ray (idirect X-ray Imaging) which interact with Gd2O2S detector. That mean I have to deal with the optical photons generated in Gd2O2S detector and interact in Silicon. This is my new simulation setup: I have different volumes and they arranged from the top to the bottom in the following way as in the image2:

A box1 made of Aluminum (white box) A box2 made of Air (Blue box) A box3 made of Gd2O2S (yellow box) A box4 made of Silicon (Orange) A box5 made of copper (Cyan) A box6 made of Pb (Green)

Box1, box3, box5 and box6 are just the detector shielding.

Please see the attached image2 to easily visualize this simulation setup. The incident X-ray will interact in the Gd2O2S scintillator and then optical photons will be created. The so generated optical photons will also interact in the Silicon detector.

Now, this is my question:

I divided the silicon detector into pixels and I used scoring parallel word to overlay the silicon detector and collect the energy deposition in each pixel of the silicon detector. But the energy deposition which I got is ZERO in all pixels of Silicon detector! Does anybody know where is the problem?

I highly appreciate your cooperation and help and many thanks in advance.

Kind regards

Ibrahym

   Attachment:
      http://hypernews.slac.stanford.edu/HyperNews/geant4/get/AUX/2010/06/14/04.01-8063-07.14-45654-image1.eps
      http://hypernews.slac.stanford.edu/HyperNews/geant4/get/AUX/2010/06/14/04.01-96137-07.14-69208-image2.eps

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