TEMPORAL MEASUREMENT OF PLASMA-DENSITY VARIATIONS ABOVE A SEMICONDUCTOR BRIDGE (SCB)

The plasma density variations above a semiconductor bridge (SCB) devic e employing a capacitor discharge firing set have been measured in vac uum (less than or equal to 10(-5) torr). A novel diagnostic technique using a microwave resonator probe was used to measure the resultant pl asma density variations as a function of time. This method is superior to Langmuir probes in this application because Langmuir probe measure ments are affected by sheath effects, small bridge area, and unknown f raction of multiple ions. Our experimental results indicate that the p lasma density is observed to increase to a peak value of 5.5x10(11) cm (-3) and decay exponentially with time, which is consistent with diffu sion dominating the plasma transport. The time needed for reaching the peak plasma density is about 1.6 mu s, which is the duration of the l ate time discharge of an SCB device.