This component marks the beginning of the region in trace in which pseudo-neutrons
are to be propagated. Pseudo-neutrons are neutrons which are generated by the function
compute_func from before and after SCATTER neutron states which have been logged by
a set of Scatter_logger/Scatter_logger_stop components.
N.B. This component should be immediately preceeded by an Arm. Any components between this one
and a subsequent Scatter_log_iterator_stop component will be visited by the set of pseudo-neutrons
as if they were regular neutrons in the classical McStas-manner.
Parameters in boldface are required;
the others are optional.