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Question Why did my Method not Work 

Forum: Fast Simulation, Transportation & Others
Date: 10 Feb, 2017
From: Sahra <Sahra>

Hi, this is mostly a question of why my particular technique in finding area cross-sections and attenuation coefficients of materials in Geant4 did not work.

I currently understand that Extended Example 'TestEm13' is the main example provided by Geant4 to enable you to find the cross-section/attenuation coefficients of different materials, which was my original project, and now understand how to use that.

However, before i came across this example, i had come up with a particular method of finding the initial and transmitted gamma photon intensities through lead, by placing a slice of lead in a envelope, a particle gun on the edge of the envelope so that it shoots perpendicular to the slice of lead, and a box_mesh/scorer on the other side of the lead.

I set my own initial intensity of gamma photons, say 10,000, and the scorer/box_mesh which i implemented via commands, would 'count' or 'score the gammas that made it through the lead, onto the scorer/box_mesh.

The scorer would only count gamma photons making it on to the scorer via. 'FlatSurfaceCurrent' which is a method to count particles injecting the surface of the scorer without taking into account the angle at which the photon hits it.

I get good values in an external text file i created like, 9064/10,000 particles were counted, but when i start building up data of thickness of lead (which i change manually in between events and then re-build the application again) against the decreasing number of photons detected, i get an attenuation coefficient value that is not equal to the actual value I am meant to get.

What have i done wrong or understood wrong? - My envelope and world volumes are both as close to vacuum as you can get. - My detector is the Geant4 default lead material of varying thickness. - My scorer is a simple box mesh, divided into 50 by 50 bins i.e. (50,50,0).

I really wish to understand how to use Geant4 to a really good level, so I would appreciate any and all feedback on this, thank you for helping.


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1 None: Re: Why did my Method not Work   (michel maire - 10 Feb, 2017)
(_ None: Re: Why did my Method not Work   (Sahra - 13 Feb, 2017)
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