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.