Physical limit on the ramp-down time

For a pulsed machine, the duration of starting and stopping the pulse is significant. While numerous Issues have addressed the ramp-up time, the ramp-down time can also be important. This preprint addresses this issue:
On the timescales of controlled termination of tokamak plasmas,
S Van Mulders, O Sauter

While Boozer and Fitzpatrick have been engaged in a slanging match about this (refs 8 and 9), Van Mulders and Sauter seem to have done a real calculation. (I don't claim to have read the paper.) Their conclusion is actually rather favorable.

Proposed solution

We could use this formula to determine the ramp-down time, which will contribute to the total time duration for which no power is produced.

We just need to know $l_{i3}$. This is calculated, but see #1878 for a lengthy discussion.