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Photon Count calculation

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acdaigneault edited this page Aug 23, 2021 · 16 revisions

In this example, photon counts calculation for a single radioactive particle that emits gamma-ray has been performed. We perform the calculations for a set of given positions inside a cylindrical tank using a Monte-Carlo technique. The Monte-Carlo calculation generates the estimated counts with respect to a detector for each particle’s position inside the vessel. The geometry of the vessel and the detector is illustrated below:

Parameter file

In the subsection “rpt parameters”, we define a set of positions inside the reactor. Common parameters for the RPT simulation are described as follows :

  • particle positions file : Filename of the text file with a set of positions inside the reactor
    Options : Any text file with .particle extension with the required header : particle_positions_x particle_positions_y particle_positions_z
  • verbosity : Enable to show photon counts numbers results in realtime in terminal
    Options : enable or quite
  • export counts : Enable to export photon counts numbers in a file
    Options : true or false
  • counts file : Filename of export counts file (.csv or .dat)
    Options : Any text file with .csv or .dat extension
  • monte carlo iteration : Defines the number of traced gamma-rays from each particle position to the detector within the defined solid angle
    Options : Any positive integer
  • random number seed : Seed number for the random number generator, using a particular number allows to run the same series of numbers
    Options : Any positive integer
  • reactor radius : Radius of the reactor vessel (cylinder only)
    Options : Any positive float
  • peak-to-total ratio : The proportion of the events appearing in the full energy peak to the total number of events (model parameter)
    Options : Any positive float
  • sampling time : Sampling time of detector(s) (model parameter)
    Options : Any positive float
  • dead time : Dead time of the detector per accepted pulse (model parameter)
    Options : Any positive float
  • activity : Activity of the tracer (model parameter)
    Options : Any positive float
  • gamma-rays emitted : Number of gamma-rays emitted by each disintegration (model parameter)
    Options : Any positive float
  • attenuation coefficient reactor : Total linear attenuation coefficient of the medium, reactor wall and air (model parameter)
    Options : Any positive float
  • attenuation coefficient detector : Total linear attenuation coefficient of the detector (model parameter)
    Options : Any positive float
# --------------------------------------------------
# RPT Monte Carlo technique
#---------------------------------------------------
subsection rpt parameters
    set particle positions file          = positions.particle
    set verbosity                        = verbose
    set export counts                    = true
    set counts file                      = counts.csv
    set monte carlo iteration            = 100000
    set random number seed               = 0
    set reactor radius       		 = 0.1
    set peak-to-total ratio  		 = 0.4
    set sampling time        		 = 1
    set dead time       		 = 1e-5
    set activity  			 = 2e6
    set gamma-rays emitted        	 = 2
    set attenuation coefficient reactor  = 10
    set attenuation coefficient detector = 21.477
end

In the subsection “detector parameters”, we specify the file that contains the position of the detector face center and the position of a point inside the detector on its axis. In this example, the detector face center position is [0.15, 0, 0.08] and [0.17, 0, 0.08] is another point on the detector’s axis. The parameters for detectors are described as follows :

  • detector positions file : Filename of the text file with positions of detector(s)
    Options : Any text file with .detector extension with the required header : face_positions_x face_positions_y face_positions_z middle_positions_x middle_positions_y middle_positions_z
  • radius : Radius of detector(s) (all detectors must have the same dimensions)
    Options : Any positive float
  • length : Length of detector(s) (all detectors must have the same dimensions)
    Options : Any positive float
#---------------------------------------------------
# Detector parameters
#---------------------------------------------------
    set detector positions file          = positions.detector
    set radius       			 = 0.0381 
    set length                           = 0.0762
end

Results

The plots below visualize the received photon counts by the detector from different positions inside the cylinder. The algorithm of RPT works based on a precise phenomenological model which relates the spatial coordinate of the radioactive particle and the number of photon counts received by the detector. The following plots are the top view (x-y plane) and front view (x-z plane) of the vessel. As it is shown, if the particle is placed in an area closer to the detector, the detector senses a higher amount of gamma-rays intensity compared to the areas further from the detector’s face.

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