Totally trapped particle leaks out into forbidden region

[David Dickinson]

In digging into issue #236/#235 and PR #767 I decided to look at the distribution function for the totally trapped particle in the “global minima not resolved” equilibrium of issue #236. This shows that for isign = 2 the pitch angle identified as totally trapped at the theta=0 local minimum is only non-zero at theta=0, whilst the isign=1 case this is not true and we instead find two theta grid points are non-zero. This is true for both PR #767 (circles) and current next (crosses):

isign = 1:

isign = 2:

The value at theta=0 appears to be single valued (as it should be).

[David Dickinson]

In practice I’m not sure that I’d expect this to have any real impact on the results as the integration weights should be zero in the forbidden region, but it may suggest something is not quite working as intended.

[David Dickinson]

Fix totally trapped treatment in forbidden region when ensuring single valued

See issue #237

→ <<cset 0c518137c404>>

[David Dickinson]

This only appears to be an issue when the totally trapped particle is not at the global minimum.