Several eV spike in target Te in deep detachment

[mikekryjak]

Electron temperature has a spike of a few eV at the final cell centre. This was visible in George Holt's simulations, Matt Khan's simulations and any other simulations I've seen in deep detachment. It doesn't seem to happen in attached simulations, or is masked by the high target temps. It is not caused by a heat source from three body recombination. It happens with both sheath_boundary (George's setup) and sheath_boundary_simple (Matt's setup). It looks like a kind of ringing overshoot.

This has been known for a while but I only just realised there hasn't been an issue for it.

It seems to be anomalous - a workaround is to use Te from before the final cell.

Here is the original plot from George:

[mikekryjak]

Possibly solved by this... need to test
#248