A high sensitivity two-color interferometer for pulsed power plasmas

A high sensitivity, high bandwidth, two-color interferometer (1064 and 532 nm) has been tested on the Hawk pulsed power generator at the Naval Research Laboratory. The phase resolution is 10−5 waves with a rise time of 3 ns, a new capability for diagnosing plasmas, and neutrals in pulsed power experiments. The two-color feature is used to distinguish phase shifts from free (plasma) electrons and bound (neutral and ion) electrons. Simultaneous electron and neutral density measurements were demonstrated in a plasma opening switch (POS) experiment. The ability to measure small phase shifts with fast rise time were demonstrated in a plasma filled diode experiment. The high sensitivity and vibration isolation enable neutral gas distribution measurements from supersonic nozzles used in plasma radiation source experiments. Examples of these measurements and future applications are described.