Secondly I used another coil, this is a single coil on a single bobbin, it measures:
no ferrite: 3.8mH bottom ferrite only: 11mH Both ferrite halfs: 110mH
So, assuming the series resistance of this coil's circuit is 10Ω (including R1 and R _{DS(ON)} of Q1), then the time constants (L/R) of these LR circuits will be, respectively: 380μs for the 3.8mH inductance 1.1ms for the 11mH inductance 11ms for the 110mH inductance These are the times needed for the current to reach 63% of the V/R limit  which is 3A if a 10Ω circuit is supplied with 30V. You are however pulsing it with only 10μs, so during that time, the current through the coil will only reach: 2.6% of 3A (or 78mA) for the 3.8mH inductance 0.9% of 3A (or 27mA) for the 11mH inductance 0.09% of 3A (or 3mA) for the 110mH inductance Thus, it is not surprising that you are not seeing a clear current ramp at this pulse width and time scale. To see it well, the pulse width has to match the time constant L/R ...at least approximately.
