Detectors¶

Detectors are used to collect the weights of photon packets that escape the sample or to collect the weight of photon packets that are specularly reflected when launching with the selected source. The the two detector locations can be populated and passed to the Monte Carlo simulator through the xopto.mccyl.mcdetector.base.Detectors. All the detector types that can be used in the Monte Carlo simulator are implemented by subclassing xopto.mccyl.mcdetector.base.Detector. The xopto.mccyl.mcdetector module includes two different detectors:

xopto.mccyl.mcdetector.total.Total implements a detector that collects the weight of photon packets into a single accumulator.
xopto.mccyl.mcsdetector.fiz.FiZ implements a 2D detector that collects the photon packets according to their polar angle $\varphi$ and $z$ location when leaving the sample and entering the surrounding medium`.

The individual detectors are conveniently imported into the xopto.mccyl.mc and xopto.mccyl.mcdetector modules.

FiZ¶

The following example shows how to create a FiZ detector that collects photon packets with polar angle $\varphi$ from -180° to 180° (1° step) and $z$ coordinate from -1 to 1 mm (10 μm step). Distribution of accumulators along the two axis is defined by Axis.

from xopto.mccyl import mc
import numpy as np

det = mc.mcdetector.FiZ(
  fi=mc.mcdetector.Axis(np.pi, np.pi, 360),
  z=mc.mcdetector.Axis(-1.0e-3, 1.0e-3, 200)
)

Note

The valid range of polar angle $\varphi$ is from $-\pi$ (-180°) to $\pi$ (180°). The first and last accumulator along the polar $\varphi$ and $z$ axis also collect the weight of all the photon packets that exceed the lower and upper bounds of the range.

Total¶

To collect the weights of photon packets that leave the sample into a single accumulator, use the xopto.mccyl.mcdetector.total.Total detector. Note that parameters cosmin and direction can be optionally used to limit the acceptance cone of the detector.

from xopto.mccyl import mc

det = mc.mcdetector.Total()

Use in Monte Carlo simulator¶

To use the detectors in Monte Carlo simulations, we need to populate an instance of xopto.mccyl.mcdetector.base.Detectors, that can independently set the detectors at the outer sample surface and the detector for photon packets that are specularly reflected at the medium-sample boundary when launched. Note that it is not required to populate the two detectors (outer and specular) as illustrated in this example.

from xopto.mccyl import mc

outer = mc.mcdetector.FiZ(
  fi=mc.mcdetector.Axis(-np.pi, np.pi, 360),
  z=mc.mcdetector.Axis(-1.0e-3, 1.0e-3, 200)
)
specular = mc.mcdetector.Total()

detectors = mc.mcdetector.Detectors(outer=outer, specular=specular)

After completing the Monte Carlo simulations, the returned instance of Detectors can be used to access the collected reflectance (also used for transmittance) or the accumulated raw weight of the photon packets.

Note

The reflectance / transmittance is computed as the raw weight in the accumulator divided by the number of launched photon packets and if applicable also divided by the surface area of the accumulator (weight/m ²).

outer_reflectance = detectors.outer.reflectance
outer weight = detectors.outer.raw

specular_reflectance = detectors.specular.reflectance
specular_raw weight = detectors.specular.raw