small intro to sample stacking

docs/index.rst

@@ -10,6 +10,7 @@ User Guide
 .. toctree::
    :titlesonly:
 
+   /user/multiple_samples
    /user/conda_environments
    /user/reduce
    /releases

docs/user/multiple_samples.rst

@@ -0,0 +1,22 @@
+.. multiple_samples
+
+Multiple Samples in a single Run
+================================
+
+The Magnetism Reflectometer can stack several (usually 2, rarely 3) samples on top of each other.
+The beam is wide enough to cover all the samples.
+To measure reflectivity, the beam is very narrow in the other direction (so it’s like a thin ribbon).
+Because we are sensitive to tiny angles,
+the reflection from each sample will appear in different sports on the detector.
+With one sample, there will be one spot on the detector.
+With two, there will be two if (1) the samples are not exactly parallel
+(in which case it will still look like one spot) and
+(2) the samples are parallel enough so that both spots are on the detector
+(otherwise one of the spots may be outside the detector surface.
+
+.. figure:: ./media/two_samples_stacked.png
+   :alt: Reflectometry from two samples stacked.
+   :align: center
+   :width: 900
+
+   Reflectometry from two samples stacked.

docs/user/reduce.rst

@@ -3,7 +3,6 @@
 Reduction
 =========
 
-
 Manual Reduction
 ----------------
 Terminal command `reduce_REF_M` is available on the conda environments `mr_reduction-qa` and `mr_reduction`.