How to specify sources of particles near the target plates?

[wphu]

In hermes-2 manual, chapter 9: simulation startup procedure, at the first step, "Start without any neutrals (neutral model = 0), specifying sources of particles near the target plates."

Could you tell me how to setup in BOUT.inp to specify sources of particles near the target plates?

Thank you.

[bendudson]

Sources of particles (and power) can be set using the input options. For particles:

[Ne]
source = 1e3 * (y - pi)^2

uses a normalised y coordinate which is uniform in Y index and goes from 0 to 2*pi. The above expression would make a source which is constant in X, but was peaked at the lower and upper Y boundaries. Higher (even) powers could be used to make the source more peaked at the targets.

This is ok in simple geometries like cylinders or slabs, but gets much harder in X-point geometry. The poloidal angle (and so y) are multi-valued, and there's currently no way in the input file to distinguish between them.

In a tokamak geometry the easiest thing to do is to specify a source of particles in the core plasma, for example:

[Ne]
source = 1e3 * exp(-(x / 0.2)^2)  

where x in the input file is uniform in radial grid index, and goes from 0 to 1.

If you want a custom source in X-point geometry, probably the only solution for now is to modify the code and create an input file. The input source is read into the code here: https://github.com/bendudson/hermes-2/blob/master/hermes-2.cxx#L456
Rather than reading from the options (BOUT.inp), you could read from the input grid

GRID_LOAD(NeSource);

then in the input grid file save an array of the source you would like.

[wphu]

So, I need NeSource arrary stored in the input grid file(.nc file), One way that I can think of is that: I write a python script; open the origin input grid file; setup NeSource array which is higher near the target plates; write the NeSource array to the input grid file; run simulation with the new input grid file after adding "GRID_LOAD(NeSource);" to hermes-2.cxx.
Do you think it is the right way?