Graded-Z shield example

This example shows how to evaluate a graded-Z shield for the use with a Compton
telescope.

Medium-energy Compton telescopes start to have a reasonable efficiency and
angular resolution above ~200 keV. However, in the space environment you have
the majority of background events below that energy. In those cases it may be
advantageous to block the low-energy photons with a graded-Z shield. However, an
optimization is required, since the shield cannot only be optimized for
blocking low energy X- and gamma rays, but also should not allow for too many
Compton, Rayleigh and pair-interactions in the shield, and it should not
activate due to long term exposure to the space radiation environment.

The example first simulates a graded-Z shield with 0.25 mm tin, 0.5 Cu and 0.5
mm Al.
The evaluation program then plots the transmission curve (number of photons
where the primary or secondary particles pass through the shield) as well as the
number of Compton interactions in the shield, where the first plot shows all
Compton interactions, and the second plot the number of Compton interactions in
the shield where the scattered gamma ray or any other secondary passes through
the shield.

To run the example, do the following:
cosima GradedZShield.source
make -f ${MEGALIB}/resource/standalone/Makefile.StandAlone PRG=GradedZShield only
GradedZShield -f GradedZShield.inc1.id1.sim -g GradedZShield.geo.setup

Please ignore all warnings about not present trigger criteria.


