Extending EPOCH

Exactly how to extend EPOCH depends heavily upon what you intend to add. The simplest things to add are new diagnostics, but other places where changes are likely to be include:

• The field solver - Changing the field solver to add new laser-like boundaries, add spatial smoothing to remove noise, add high order field solvers etc.
• The particle pusher - Change the basic physical model of EPOCH by modifying the particle pusher.
• The boundary routines - Add new boundary conditions or modify existing boundary conditions.
• The laser boundary routines - Add new features to the laser boundaries in this routine.
• Physics packages - EPOCH includes many existing physics packages, but the list is not complete. For example, the user may wish to add support for nuclear or particle physics processes, or electron-ion recombination.
• The main driver (epochnd.F90) - This is the routine where the main calling sequence of EPOCH is setup, and totally new extensions to EPOCH should be placed in here.

Changing the field solver, the particle pusher or boundary routines is fairly easy to accomplish by reading the section of this manual that details the relevant code. The general sequence for writing an extension would be:

• Add any new global variables needed to shared_data.F90.
• Add the meat of your change to the code.
• Test the changes to your code. Make absolutely sure that you can turn your change to the code off.
• Add controls for your extension to the input deck reader.

Examples

The subpages here detail a few examples on how to make direct changes to the EPOCH source-code, without going through user-interaction interfaces. These include:

• Input deck - Instructions on creating a new input deck block.
• Maths parser - How to create a new function for the maths parser.
• New module - If you already have the source-code for a new module or physics package, this will tell you how to add it to the EPOCH PIC loop.