But, I am going to be honest here. I doubt you have over-unity.
If you do take the time to conduct an efficiency calculation experiment, you will see that the LED lamp is not using its rated 50Watts.
You could rectify and filter the the energy you are picking up wireless'ly with a full-wave-bridge-rectifier, then smooth the power with some high capacitance filter caps (5000uF or more), then measure the current across a dummy load with a know resistance, a large dummy load resistor would work.. The use Ohms law to figure the wattage being used... Plug your plamsa ball into a wall-wort watt meter ($20 wall-mart)... Compare your power in VS power out... It really is that easy.
And (again, just my opinion) if I had to bet my left nut, I would bet against any Over-Unity phenomenon happening... but the truth be told, no one will know until a proper test is run.
Again, cool demonstration.. I want to buy a Plasma-Ball now.