add more details in the interrupt examle

doc/pages/interrupting-simulations.rst

@@ -1,9 +1,20 @@
 Interrupting simulations on runtime
 ------------------------------------------------
 
-.. toctree::
+CRPropa simulations can be interrupted on runtime with the `SIGTERM` or `SIGINT` signals. 
+If the user defines an output for the interruption (called `InterruptAction`) all candidates which are currently in the simulation will be passed to this output. 
+In the error stream the user will see a message denoting the number of candidates which have not been started yet. 
+If the simulation was run with a `candidateVector` as source, the indices of the candidates which have not been started yet will be printed or written to the file.
+For a simulation with a source interface, a restart with the missing number of candidates will be sufficient to continue the simulation.
 
+.. toctree:: 
+   :caption: Using a candidateVector as source
+   :maxdepth: 0
    example_notebooks/interrupting_simulations/interrupt_candidateVector.ipynb
+
+.. toctree:: 
+   :caption: Using a source interface
+   :maxdepth: 0
    example_notebooks/interrupting_simulations/interrupt_source.ipynb