A monte carlo simulation of energy deposited in scinti safe plus 50 by a charged particle
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A Monte Carlo Simulation of Energy Deposited in Scinti-Safe Plus 50% by a Charged Particle. Maureen Sikes UNC-Pembroke Natasha McNair: UNC-Greensboro Advisor: Dr. Tom Dooling-UNCP.

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A monte carlo simulation of energy deposited in scinti safe plus 50 by a charged particle
A Monte Carlo Simulation of Energy Deposited in Scinti-Safe Plus 50% by a Charged Particle

  • Maureen SikesUNC-Pembroke

  • Natasha McNair: UNC-Greensboro

  • Advisor: Dr. Tom Dooling-UNCP


A Monte Carlo Simulation of Energy Deposited in Scinti-Safe Plus 50% by a Charged ParticleMaureen Sikes: UNCPNatasha McNair: UNC-GreensboroAdvisor: Dr. Tom Dooling-UNCPAbstract

  • In conjunction with an experimental study, a Monte Carlo program was created using FORTRAN to simulate the energy deposited in a liquid scintillator by a charged particle. The overall study examined whether light responses in an organic scintillating liquid were proportional to the amount of energy deposited in the scintillator by a charged particle. The study was carried out using common radiological sources as a preliminary step in the development of a radiological device to be used in response to a “dirty bomb” attack. This work was supported by the National Science Foundation's Research Experiences for Undergraduates program (CHE- 0353724).


What is a monte carlo
What is a Monte Carlo? Plus 50% by a Charged Particle

  • The Monte Carlo program is a software simulation of our experimental work, written in GNU Fortran

  • The simulation helps us to better understand our experimental data.

  • It can be used to develop new experimental models.

  • Programs have been developed to simulate the behavior of a beta particle emitted from either a Strontium-90 or Thallium-204 source

  • A program to simulate the behavior of gamma rays from a Cobalt-60 source is still in development


Event generation
Event Generation Plus 50% by a Charged Particle

  • First an event or simulated particle is created

  • Simulated beta particles are assigned several initial properties through the use of random number generators

  • The frequent use of random number generators in the program is why this type of program is called a “Monte Carlo”

  • Initial Particle Energy

    • First a particle must be assigned a random energy appropriate for the type of particle it is simulating

    • Use the radioisotope’s maximum energy along with the random number generator

    • Test the energy against the radioisotope’s beta decay spectrum to see if it’s a valid representation

    • For an Strontium-90 source, will the beta particle simulate a Strontium or Yttrium emission?


Strontium 90 beta spectrum
Strontium-90 Beta Spectrum Plus 50% by a Charged Particle


Yttrium 90 beta spectrum
Yttrium-90 Beta Spectrum Plus 50% by a Charged Particle


Thallium 204 beta spectrum
Thallium-204 Beta Spectrum Plus 50% by a Charged Particle


Cobalt 60 beta spectrum
Cobalt-60 Beta Spectrum Plus 50% by a Charged Particle


Initial properties
Initial Properties Plus 50% by a Charged Particle

  • Initial Position

    • The particle is randomly assigned an initial x and y position within the source disc

  • Random Angle

    • The particle is also randomly assigned an angle in three dimensions at which it leaves the source

  • Collimation

    • The Strontium-90 and Thallium-204 sources were both experimentally tested two ways: collimated and un-collimated

    • To simulated the physical restriction of collimation, an option was included in the angle generation section

    • When selected, the particle was assigned only a path straight out of the source


Particle tracking
Particle Tracking Plus 50% by a Charged Particle

  • Now that the simulated particle has been assigned all of its initial properties, it leaves the source and we follow it as it passes through the simulated materials

  • The program takes the particle through a series of materials corresponding to the actual materials used in the experimental setup

  • Stopping Power

    • Each material interacts differently with a charged particle

    • Stopping power is a measure of how much energy is lost per centimeter in a given material and is a function of the energy of the particle


Stopping Power Plus 50% by a Charged Particle Table for Plastic Polymethyl Methacralate (Lucite, Perspex, Plexiglass)(Beta Energy Spectrum)



How particles travel
How Particles Travel (Beta Energy Spectrum)

  • Particles travel through the materials one “step” at a time from their initial position

  • For our simulations we defined a “step” to be 0.01cm

  • After every “step” the particle’s current position, energy and applied conditions are reevaluated by the program


Material selection and energy tracking
Material Selection and Energy Tracking (Beta Energy Spectrum)

  • One of the factors recalculated after every step is how far the particle has traveled from the source

  • This distance is used to tell the program which material the particle is passing through

  • For example, the plastic material covering the source is defined to be from 0.0 cm to 0.05 cm away from the source

  • After the particle has passed 0.05cm, it has moved on to the next material, Teflon

  • After the material to be applied for a step is selected, the particle’s energy is put into the stopping power function for that material

  • This calculates the stopping power to be applied in this step

  • The stopping power value is used to calculate the mean energy loss for the step


Energy spreading
Energy Spreading (Beta Energy Spectrum)

  • When a charged particle actually passes through a material, the large number of collisions it incurs causes statistical variations

  • This results in the actual energy loss not simply being the mean energy loss expected

  • The energy loss is better illustrated as distribution of energy, not a direct shift

  • This distribution is generally Gaussian in form, so it can be calculated and a correction factor applied

  • After the energy spreading is applied, the corrected energy loss for the step is subtracted to get the energy of the particle in its next step


Sr 90 without spreading
Sr-90 without Spreading (Beta Energy Spectrum)


Sr 90 with spreading
Sr-90 with Spreading (Beta Energy Spectrum)


Sr 90 experimental data
Sr-90 Experimental Data (Beta Energy Spectrum)


When to stop tracking
When to Stop Tracking (Beta Energy Spectrum)

  • The particle has left the equipment

  • The particle’s energy is too small

  • When this occurs the program starts over with the creation of a new particle


Conclusions
Conclusions (Beta Energy Spectrum)

  • Once the particle reaches the scintillating material the energy lost by the particle is tallied

  • For each step (0.01cm) in the scintillating material some of the particle’s energy is deposited into the material

  • This deposited energy is added to the energy from the previous steps

  • The total energy deposited in the scintillating material is proportional to the light generated experimentally

  • The program is run for 500,000 events, where each event represents one particle simulation

  • This sufficiently reproduces the general shape of experimental energy distributions

  • Therefore the program has strong predictive power


Results Sr-90 Collimated (Beta Energy Spectrum)

Noise Corrected Graphs Monte Carlo Graphs

Crun 01a – 2.5 cm of Scintillator Mrun 01a – 2.5 cm of Scintillator

Crun01b – 2.0 cm of Scintillator Mrun01b – 2.0 cm of Scintillator


Results Sr-90 Un-collimated (Beta Energy Spectrum)

Noise Corrected Graphs Monte Carlo Graphs

Crun02a – 2.5 cm of Scintillator Mrun02a – 2.5 cm of Scintillator

Crun02b – 2.0 cm of Scintillator Mrun02b – 2.0 cm of Scintillator


Results Tl-204 Collimated (Beta Energy Spectrum)

Noise Corrected Graphs Monte Carlo Graphs

Crun03a – 2.5 cm of Scintillator Mrun03a – 2.5 cm of Scintillator

Crun03b – 2.0 cm of Scintillator Mrun03b – 2.0 cm ofScintillator


Results (Beta Energy Spectrum)Tl-204 Un-collimated

Noise Corrected Graphs Monte Carlo Graphs

Crun04a – 2.5cm of Scintillator Mrun04a – 2.5cm of Scintillator

Crun04b – 2.0 cm of Scintillator Mrun04b – 2.0 cm of Scintillator


Acknowledgements
Acknowledgements (Beta Energy Spectrum)

National Science Foundation

Research Experience for Undergraduates

Program

At the University of North Carolina at Pembroke

Summer 2004

Funding made possible in part by grant

#CHE-0353724 from the National Science Foundation’s “Research Experience for Undergraduates” program


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