The Particle Sources element contains all particle sources of the simulation. All particle sources contain the same options, but are differentiated based on the specification type. Multiple particle sources may be used in a single simulation.
point A point source can specify the x,y and z coordinates of the point. All particles will emit from this point. The point is visualized by a sphere. The radius of this sphere is controlled by the representationRadius property, it has no effect on the simulation.
surface A surface source will emit particles inwards from the surface specified. At this time spheres and boxes are available, with cylindrical sources to be added shortly.
volume A volume source will emit particles in the volume of the surface, at this time sphere and box sources are available, with cylindrical sources to be added shortly.
plane A plane source will emit particles from the 2D plane specified. The available types of planes are.
- xy plane This is a rectangular plane on the xy axis.
- offset The z coordinate of the plane.
- xMin The lower x coordinate of the plane.
- xMax The upper x coordinate of the plane.
- yMin The lower y coordinate of the plane.
- yMax The upper y coordinate of the plane.
- xz plane This is a rectangular plane on the xz axis.
- offset The y coordinate of the plane.
- xMin The lower x coordinate of the plane.
- xMax The upper x coordinate of the plane.
- zMin The lower z coordinate of the plane.
- zMax The upper z coordinate of the plane.
- yz plane This is a rectangular plane on the yz axis.
- offset The x coordinate of the plane.
- yMin The lower y coordinate of the plane.
- yMax The upper y coordinate of the plane.
- zMin The lower z coordinate of the plane.
- zMax The upper z coordinate of the plane.
- xy ellipsis An ellipsis (or circle) on the xy plane
- rX The x-radius of the ellipsis.
- rY The y-radius of the ellipsis.
- x The center of the ellipsis on the x axis.
- y The center of the ellipsis on the y axis.
- z The center of the ellipsis on the z axis.
- xz ellipsis An ellipsis (or circle) on the xz plane
- rX The x-radius of the ellipsis.
- rZ The z-radius of the ellipsis.
- x The center of the ellipsis on the x axis.
- y The center of the ellipsis on the y axis.
- z The center of the ellipsis on the z axis.
- yz ellipsis An ellipsis (or circle) on the yz plane
- rY The y-radius of the ellipsis.
- rZ The z-radius of the ellipsis.
- x The center of the ellipsis on the x axis.
- y The center of the ellipsis on the y axis.
- z The center of the ellipsis on the z axis.
number of particles per event This is the number of particles to emit for each event.
particle type The type of particle to emit. The available particles are:
- electron
- proton
- neutron
- positron
- alpha
- gamma
- ion
- atomic number Atomic number of the ion.
- nucleon number Number of nucleons in the ion.
- charge Charge of the ion.
- nuclear excitation Excitation of the ion.
Angular Dist The type of angular distribution of the particle source.
Omnidirectional With an omnidirectional angular distribution the fluence for each direction is proportional to the cosine of the angle between the source direction and local noraml of the surface.
- min theta The minimum angle, 0 degrees corresponds to the -Z axis.
- max theta The maximum angle, 180 degrees corresponds to the +Z axis.
If Computed Normalization is selected, and the source is not a point, the angular distribution factor is calculated as \(\frac{1}{4}*(\sin^{2}(max theta) - \sin^{2}(min theta)\)
If the source is a point, the angular distribution factor is \(\frac{1}{2}*(\cos(min theta) - \cos(max theta)\)
Isotropic If emitting from a rectangular slab or plane, the final distribution of particles will not in fact be isotropic as the angle of emission will impact the resulting fluence.
- min theta The minimum angle, 0 degrees corresponds to the -Z axis.
- max theta The maximum angle, 180 degrees corresponds to the +Z axis.
If Computed Normalization is selected, the angular distribution factor is 1.0
Beam1D A beam1D source will feature a uniform dispersion angle around the beam. The beam angular distribution is only available with planar sources.
- dispersion angle The dispersion angle of the beam.
- beam direction Either positive or negative, this will send the particles on the corresponding axial direction.
If Computed Normalization is selected, the angular distribution factor is 1.0
focused Particles will be focused on the particular point specified in the simulation space. This is a useful setting for debugging simulaitons
focus point x X coordinate to focus on.
focus point y Y coordinate to focus on.
focus point z Z coordinate to focus on.
If a focused angular distribution is used, Computed Normalization cannot be used.
Energy Spectrum The energy spectrum of the particle source. Options are
MonoEnergetic
- energy Energy of the source.
- units Units of the energy source specified.
- fluence Used in normalization calculations if Computed Normalization is selected.
If using computed normalization, the energy normalization factor will take the form \(\frac{gradient}{2}max^{2}+intercept*max-\frac{gradient}{2}min^{2}+intercept*min\)
Linear The linear distribution takes the form y = coefficient * energy + intercept
- min Minimum energy.
- max Maximum energy.
- units Units of the energy source.
- intercept Intercept of the linear curve.
- coefficient Coefficient of the linear function
If using computed normalization, the energy normalization factor will take the form \(\frac{coefficient}{2}max^{2}+intercept*max-\frac{coefficient}{2}min^{2}+intercept*min\)
Power Law The power law distribution takes the form y = coefficient * energy ^ alpha
- min Minimum energy.
- max Maximum energy.
- units Units of the energy source.
- alpha The exponential of the energy distribution.
- coefficient The source strength multiplier.
If using computed normalization, the energy normalization factor will take the form \(\frac{coefficient}{(alpha + 1)} * max^{alpha + 1} - \frac{coefficient}{(alpha + 1)} * min^{alpha + 1}\)
Exponential The exponential distribution takes the form \(y = coefficient * e ^(\frac{energy}{eZero})\)
- min Minimum energy.
- max Maximum energy.
- units Units of the energy source.
- coefficient The source strength multiplier.
- eZero Base value of the exponential.
If using computed normalization, the energy normalization factor will take the form \(-coefficient*eZero*e^{\frac{-Emax}{eZero}} + coefficient*eZero*e^{\frac{-Emin}{eZero}}\)
2 Column File The 2 column file needs to be arranged in order of Energy|Differential Fluence increasing from row to row.
- file name Name of the file.
- interpolation type Interpolation between points of the file.
- linear
- logarithmic
- cubic spline
- exponential
If using computed normalization, the energy normalization factor is the difference between the max and min integral flux, which is automatically calculated and applied.
Gaussian This gives a guassian energy distribution, and does not allow for a computed normalization to be used.
- energy center Center of the gaussian distribution.
- sigma The standard deviation of the gaussian distribution.
- units The units of the energy center.
Weighted A weighted energy spectrum requires usage of a two column file in which the first column is Particle Energy (MeV) and second is the weighting of particles at that energy level.
- file name Name of the file.
- interpolation type Interpolation between points of the file.
- linear
If using computed normalization, the integral flux of the source spectrum is automatically calculated and applied to the simulation.
Unique to RSim is the ability to specify a geometric biased source. This is only available when using a surface spherical source, and without normalization. The concept of geometric biasing is to increase the number of particles, while cutting the weight of the particles each time a particle passes through a predefined sphere. This allows for the simulation of many particles to hit a target while keeping the number of particles in the simulation lower. A probability can also be assigned to the odds of this event occuring
If a particle exits a bias sphere, there is a 50% chance it is either removed from the simulation, or doubled in weight.
The first layer is set to be 95% of the radius of the source surface. The last layer is specified as shown below. All layers between these two will be set automatically to have an equal decrease in radius, with centers as set by the bias sphere.
- number of bias layers Number of biasing layers to use, must be at least 2
- bias probability The probability a particle will be multiplied by the bias factor, with its weight reduced accordingly, effectively modifying the bias factor. This is typically set to one but may be modified in the event over-biasing is observed, which is characterized by an unphysical spike in simulation results.
- bias factor Normal corresponds to two particles being created for each particle that passes through a layer, Extreme 3, and Debug 4. It is highly reccomended to leave on the normal setting.
- bias sphere This corresponds to the location and size of the innermost bias layer.
- x x coordinate of the innermost layer center
- y y coordinate of the innermost layer center
- z z coordinate of the innermost layer center
- radius radius of the innermost layer
Where surfaceArea is the surface area of the source, and Nparticles is the number of particles emitted by the source.
- No Normalization If selected the source will not have any external factors multiplied over it’s result.
- Computed Normalization If computed normalization is used, the normalization factors are calculated as described in the energy spectrum and angular distribution.
- Manual Normalization With manual normalization the normalization factor is calculated directly by the energy normalization factor and angular normalization factor, with no regard for source surface area or number of particles in the simulation.