X Ray Image Query: Documentation New Introduction
@@ -9,12 +9,26 @@ X Ray Image Query
.. contents:: :local:
-The X Ray Image Query generates a simulated radiograph by tracing rays through a volume using an absorbtivity and emissivity variable.
-The absorbtivity and emissivity variables must be zone-centered and can be either scalar variables or array variables.
-If using an array variable, the query will generate an image per array variable component.
+Introduction
+~~~~~~~~~~~~
+
+The X Ray Image Query computes the attenuation and self-emission for radiation passing through an object.
+The xray query can be used for EUV radiation and, in some cases, for optical light.
+The attenuation is used when simulating a radiograph (an xray of a broken bone is a radiograph).
+If the object is hot enough, it emits xrays and the self-emission is of interest.
+
+The query tracks rays through a grid of zone-centered opacities (absorbtivities) and emissivities.
+The absorbtivity and emissivity variables must be zone-centered and can be either scalar variables (special case) or array variables.
+The opacity and emissivity in each zone is a function of radiation energy and rays are tracked for all energies.
+The rays are regularly spaced in the image plane and the query generates an image per radiation energy.
+
+The inputs to the query are usually generated by a computer simulation of the temporal evolution of an object.
+The simulation records the opacity and emissivity at a set of times.
+The images produced by the query can be convolved with the spatial, spectral, and temporal response of an (xray) detector in a post-processing step.
+The simulated data can be compared with data recorded during an experiment to see if the simulation is accurate.
The query operates on 2D R-Z meshes and 3D meshes.
-In the case of 2D R-Z meshes, the mesh is revolved around the Z axis.
+In the case of 2D R-Z meshes, the mesh is revolved around the Z-axis and the rays are tracked in 3 dimensions.
The query performs the following integration as it traces the rays through the volume.
@@ -44,10 +58,14 @@ If the ``divide_emis_by_absorb`` is set, then the following integration is perfo
:start-after: begin absorbtivity-normalized integration
:end-before: end absorbtivity-normalized integration
-When making a simulated radiograph, either the emissivity variable must contain non-zero values or a background intensity will need to be specified using either *background_intensity* or *background_intensities*.
-See :ref:`Standard Arguments` for more information.
-If neither of these is the case, you will get an all white image.
-A non-zero emissivity variable would correspond to an object emitting radiation and a non-zero background intensity would correspond to constant backlit radiation, such as when X-raying an object.
+When the goal of the query is to generate a radiograph, the user supplies a background intensity (using either *background_intensity* or *background_intensities*; see :ref:`Standard Arguments`) and sets the emissivity arrays to zero.
+The self-emission image produced by the query is then a radiograph.
+
+When the goal of the query is to generate a self-emission image, the emissivities should be non-zero and a background intensity should not be supplied.
+
+Sometimes the goal of an experiment is to generate a radiograph, but the object is hot enough that self-emission might "wash out" the radiograph.
+In this case, the emissivities should be non-zero and the background intensity should be supplied.
+The background intensity can then be adjusted until the radiograph is not washed out.
Query Arguments
~~~~~~~~~~~~~~~
