Current drive fractions do not add to 1

[jonmaddock]

In GitLab by @mkovari on May 18, 2023, 11:53

This code falsifies the current drive fractions so they do not add to 1. No error message appears in the output file.

            #  Plasma driven current fraction (Bootstrap + Diamagnetic
            #  + Pfirsch-Schlüter) constrained to be less than
            #  or equal to the total fraction of the plasma current
            #  produced by non-inductive means (which also includes
            #  the current drive proportion)
            physics_module.err243 = 0
            if current_drive_variables.plasipf > physics_variables.fvsbrnni:
                current_drive_variables.plasipf = min(
                    current_drive_variables.plasipf, physics_variables.fvsbrnni
                )
                physics_module.err243 = 1

@stuartmuldrew ?

[jonmaddock]

In GitLab by @kj5248 on May 18, 2023, 12:00

Bootstrap_fraction______________________________________________________ (bootipf)_____________________ 7.0000E-01
Diamagnetic_fraction____________________________________________________ (diaipf)______________________ 0.0000E+00
Pfirsch-Schlueter_fraction______________________________________________ (psipf)_______________________ 0.0000E+00
Auxiliary_current_drive_fraction________________________________________ (faccd)_______________________ 0.0000E+00
Inductive_fraction______________________________________________________ (facoh)_______________________ 3.0550E-01
Total___________________________________________________________________ (plasipf+faccd+facoh)_________ 1.0000E+00
Fraction_of_the_plasma_current_produced_by_non-inductive_means__________ (fvsbrnni)____________________ 6.9450E-01 ITV

[jonmaddock]

In GitLab by @stuartmuldrew on May 18, 2023, 16:53

I'm confused in the above example as there is no heating and current drive. I think this goes back to the odd way PROCESS has handled the bootstrap current limit, where it enforces the maximum by overwriting the value rather than modifying the plasma solution.

[chris-ashe]

Related issue #3273

[j-a-foster]

@chris-ashe and I have looked at this and it seems that the current fractions are decoupled in how they're calculated and relate to one another. The non-inductive current fraction is an iteration variable but I can't see what constrains its value? This then sets the plasma driven current but as that is bootipf + diaipf + psipf, it doesn't then report the fractions correctly summing to 1 as bootipf is the only value reported, not plasipf.

Also, the inductive fraction has no relation to the CS whatsoever, it's simply: 1 - non-inductive fraction