MCNP: Can I input the X-Ray tube voltage in MCNP source specification?

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SUMMARY

The discussion clarifies that the X-Ray tube voltage cannot be directly input into MCNP source specifications. Instead, the energy of the photon source is specified, with a 100kV X-ray tube simulated using electrons of energy 0.1 MeV (SDEF ERG= in MeV). The current (mA) influences the number of particles generated per second but does not affect the energy per particle. The simulation results are per source particle, and adjustments for real-world applications are made post-simulation to derive flux or dose rate.

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  • Understanding of MCNP (Monte Carlo N-Particle Transport Code) version 6.2 or later
  • Knowledge of photon and electron energy specifications in MeV
  • Familiarity with concepts of electric potential and kinetic energy
  • Basic grasp of particle intensity and current measurement in mA
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Anisur Rahman
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TL;DR
Source Specification
Can I input the X-Ray tube voltage in MCNP source specification?
 
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Anisur Rahman said:
TL;DR Summary: Source Specification

Can I input the X-Ray tube voltage in MCNP source specification?
One would put in energy or energy spectrum for a photon source. I am not aware that voltage for an X-ray tube is an input.
 
An electron falling through a potential difference of 1V gains 1eV of kinetic energy.

So an X-ray tube powered at 100kV would be simulated with a beam of electrons of energy 0.1 MeV (SDEF ERG= are in MeV) directed at a target.
 
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Alex A said:
An electron falling through a potential difference of 1V gains 1eV of kinetic energy.

So an X-ray tube powered at 100kV would be simulated with a beam of electrons of energy 0.1 MeV (SDEF ERG= are in MeV) directed at a target.
Even if the current value (mA) differs?
 
mariem said:
Even if the current value (mA) differs?
The current determines the number of particles (mA/e) per sec, were e is the unit charge.

The accelerating potential determines the energy per particle.

The total energy/sec or power would be the number of particles/sec * energy/particle, and the total energy or dose deposited would be related to the integral over time of the (particles/sec * energy/particle).
 
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Yes, as @Astronuc says the intensity is the other part of the problem. Almost all answers output by MCNP are per source particle. So no one would attempt to simulate one mA-second (a milli coulomb) of electrons. Enough particles are simulated to get a statistically useful answer and then the results which are per source particle are multiplied by the real world source activity to get flux or dose rate answers, or the total number of real world particles to get dose.

It also means that if you are simulating a 1mA tube and a 10mA tube (the same tube at the same voltage) that only one simulation needs to be done because these situations are the same. Only the maths done afterwards differs.
 
Where can I input the electron source intensity in MCNP? How many particles will I have for an X-ray tube set at an intensity of 10 mA?
 
Do you understand coulombs, do you understand unit charge (the charge on an electron)?
 

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