Your wave is perfect. What you see on the Yellow Trace is Current Ramp Up ( Storage ) and Ramp Down ( Decay ):
The reason you're seeing this, is because your Current Sensing Resistors are on the other side of your Input.
So you're seeing your Input as well as your Output. To resolve this and only see Output.
You can see Current Sensing Resistor R1 will not see the Input Current, only Output Current. This will give you the same Yellow Trace Waveform. Other than this, your Wave forms are perfect!
CD, you should be extremely proud of yourself! As you said, a lot is already learned. And the most important part!
Yes you're correct, your Coils have become a Battery! The Interactions between them are now Supplying Current in Excess of what was supplied to them! This is am amazing fact, something that 99% of Physicists could not explain!
Food for Thought:
We have Injected a Magnetic Field into a Core Material, this has Cost us the Magnetising Current only, we have Zero Input to Output Coupling, therefore our Input is not affected at all by Loading our Output.
However, as the Magnetic Field dissipates in the Core, Inductive Collapse, then this changing Magnetic Field in Time ( t ), constitutes as a Source of Changing Magnetic Field for Electromagnetic Induction. The same Rules apply in the Equation for Electromagnetic Induction.
This is something Floyd Sweet talked about, stating:
The number of turns per coil is determined by Faraday's law as quantized by Neumann. Stranded wire is used for ease of winding.
It is worth noting, the VTA had sufficient Cross Sectional Area and Turns ( 240 ) to support this statement!
We need to be open minded here, however. There are lots of ways to increase the E.M.F, some much easier than others. One being a very sharp Spike, from a Spark Gap or similar device.
I did say some months back how important these experiments were, and now you have done them I bet you would also say the same?
Great work CD! All readers can learn from your excellent work. Also it is completely necessary to do the Experiments as you simply can not fully understand by reading alone.
P.S: Please Note, I have moved my reply's to Partnered Output Coils - Discussion, I do not wish to fill CD's Thread with content that should be elsewhere.