Survey of plasma diagnostic techniques applicable to radiographic diodes

Plasmas are ubiquitous in the high-power electron beam diodes used for radiographic applications. In rod pinch and immersed B/sub z/ diodes they are found adjacent to the cathode and anode electrodes, and are suspected of affecting the diodes' impedance characteristics as well as the radiographic spot size. In paraxial diodes, preionized plasmas or beam-formed plasmas are also found in the gas focusing section. A common feature of the plasmas adjacent to the electrodes is that their densities can range from 10/sup I2/-10/sup 17/ cm/sup -3/, and their velocity is on the order of I0/sup 7/ cm/s. Researchers from the Naval Research Laboratory have developed a high-sensitivity two-color interferometer that is presently being tested on Gamble Il for future use on the Sandia RITS accelerator operating with a B/sub z/ diode. This diagnostic is capable of resolving a line-integrated electron density of 2x10/sup 12/ cm/sup -2/, a density that might be capable of even observing the electron beam directly. This paper will present an overview of laser-based and spectroscopic diagnostics that could be used to measure plasmas found in radiographic diodes with spatial and temporal resolutions on the order of 1-5 mm and 5 ns, respectively. Plans for the use of this diagnostic on a preionized plasma cell of a paraxial diode on the Sandia RITS experiment will be discussed.