Digging in the Data—oscillations and x-raysApril 4, 2014
The months that FF-1 is not running have given the LPP research team time to look more deeply at the hundreds of gigabytes of data that the experiments have been generating. One puzzle LPP Electrical Engineer Fred van Roessel looked at was the rapid oscillation in current and voltage that occurs when the machine fires and right after the pinch (see graph). These are almost always seen in plasma focus devices but have not had a satisfactory explanation. Van Roessel wrote programs to analyze the oscillations, concluding that they were due to current sloshing back and forth along the transmission plates that connect the capacitors to the electrodes. This hypothesis implied that the peak voltage the device generates during the pinch is proportional to the total drop in current at the same time. Sure enough, the data for the past year showed that the ratio of the voltage spike at the time of the pinch relative to the drop in current during the pinch is constant at 72 milliohms with a standard deviation of only 16%.
This result is important because it allows us to predict that the maximum possible voltage spike is 200 kV, well below the 1 MV estimated strength of the main Mylar insulators. It is even further below the 5 MV strength of the ceramic insulator that separates the electrodes.