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.

pointA 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 therepresentationRadiusproperty, it has no effect on the simulation.

surfaceA 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.

volumeA 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.

planeA plane source will emit particles from the 2D plane specified. The available types of planes are.

xy planeThis is a rectangular plane on the xy axis.

offsetThe z coordinate of the plane.xMinThe lower x coordinate of the plane.xMaxThe upper x coordinate of the plane.yMinThe lower y coordinate of the plane.yMaxThe upper y coordinate of the plane.xz planeThis is a rectangular plane on the xz axis.

offsetThe y coordinate of the plane.xMinThe lower x coordinate of the plane.xMaxThe upper x coordinate of the plane.zMinThe lower z coordinate of the plane.zMaxThe upper z coordinate of the plane.yz planeThis is a rectangular plane on the yz axis.

offsetThe x coordinate of the plane.yMinThe lower y coordinate of the plane.yMaxThe upper y coordinate of the plane.zMinThe lower z coordinate of the plane.zMaxThe upper z coordinate of the plane.xy ellipsisAn ellipsis (or circle) on the xy plane

rXThe x-radius of the ellipsis.rYThe y-radius of the ellipsis.xThe center of the ellipsis on the x axis.yThe center of the ellipsis on the y axis.zThe center of the ellipsis on the z axis.xz ellipsisAn ellipsis (or circle) on the xz plane

rXThe x-radius of the ellipsis.rZThe z-radius of the ellipsis.xThe center of the ellipsis on the x axis.yThe center of the ellipsis on the y axis.zThe center of the ellipsis on the z axis.yz ellipsisAn ellipsis (or circle) on the yz plane

rYThe y-radius of the ellipsis.rZThe z-radius of the ellipsis.xThe center of the ellipsis on the x axis.yThe center of the ellipsis on the y axis.zThe center of the ellipsis on the z axis.

number of particles per eventThis is the number of particles to emit for each event.

particle typeThe type of particle to emit. The available particles are:

electronprotonneutronpositronalphagammaion

atomic numberAtomic number of the ion.nucleon numberNumber of nucleons in the ion.chargeCharge of the ion.nuclear excitationExcitation of the ion.

Angular DistThe type of angular distribution of the particle source.

OmnidirectionalWith an omnidirectional angular distribution the fluence for each direction is proportional to thecosineof the angle between the source direction and local noraml of the surface.

min thetaThe minimum angle, 0 degrees corresponds to the -Z axis.max thetaThe 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 \(\frac{1}{2}*(\cos(min theta) - \cos(max theta)\)

IsotropicIf 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 thetaThe minimum angle, 0 degrees corresponds to the -Z axis.max thetaThe maximum angle, 180 degrees corresponds to the +Z axis.If Computed Normalization is selected, the angular distribution factor is 1.0

Beam1DA beam1D source will feature a uniform dispersion angle around the beam. The beam angular distribution is only available with planar sources.

dispersion angleThe dispersion angle of the beam.beam directionEither 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

focusedParticles will be focused on the particular point specified in the simulation space. This is a useful setting for debugging simulaitons

focus point xX coordinate to focus on.

focus point yY coordinate to focus on.

focus point zZ coordinate to focus on.If a focused angular distribution is used, Computed Normalization cannot be used.

Energy SpectrumThe energy spectrum of the particle source. Options are

MonoEnergetic

energyEnergy of the source.unitsUnits of the energy source specified.fluenceUsed in normalization calculations ifComputed Normalizationis selected.If using computed normalization, the energy normalization factor will take the form \(\frac{gradient}{2}max^{2}+intercept*max-\frac{gradient}{2}min^{2}+intercept*min\)

LinearThe linear distribution takes the form y = coefficient * energy + intercept

minMinimum energy.maxMaximum energy.unitsUnits of the energy source.interceptIntercept of the linear curve.coefficientCoefficient of the linear functionIf 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 LawThe power law distribution takes the form y = coefficient * energy ^ alpha

minMinimum energy.maxMaximum energy.unitsUnits of the energy source.alphaThe exponential of the energy distribution.coefficientThe source strength multiplier.If using computed normalization, the energy normalization factor will take the form \(\frac{coefficient}{(alpha + 1)} * max^{alpha + 1} - \frac{coefficient}{(alpha + 1)} * min^{alpha + 1}\)

ExponentialThe exponential distribution takes the form \(y = coefficient * e ^(\frac{energy}{eZero})\)

minMinimum energy.maxMaximum energy.unitsUnits of the energy source.coefficientThe source strength multiplier.eZeroBase 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 FileThe 2 column file needs to be arranged in order of Energy|Differential Fluence increasing from row to row.

file nameName of the file.interpolation typeInterpolation between points of the file.

linearlogarithmiccubic splineexponentialIf using computed normalization, the energy normalization factor is the difference between the max and min integral flux, which is automatically calculated and applied.

GaussianThis gives a guassian energy distribution, and does not allow for a computed normalization to be used.

energy centerCenter of the gaussian distribution.sigmaThe standard deviation of the gaussian distribution.unitsThe units of the energy center.

WeightedA 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 nameName of the file.interpolation typeInterpolation between points of the file.

linearIf 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 layersNumber of biasing layers to use, must be at least 2bias probabilityThe 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 factorNormal 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 sphereThis corresponds to the location and size of the innermost bias layer.

xx coordinate of the innermost layer centeryy coordinate of the innermost layer centerzz coordinate of the innermost layer centerradiusradius of the innermost layer

- With a Computed Normalization the normalization factors are calculated based on the parameters described above, and then multiplying the final tally results by surfaceArea/Nparticles * (energyNormalizationFactor * angularNormalizationFactor)
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 itâ€™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.