Ed Navarre - Design and Characterization of a Theta-Pinch Imploding Thin Film Plasma Source For Atomic Emission Spectrochemical Analysis

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      Publication Details (including relevant citation   information):

      Edward C. Navarre and Joel M. Goldberg, Applied Spectroscopy.   65, 26-35 (2011)

      Abstract:

      A new atomization device for direct atomic spectrochemical   analysis has been developed that uses the theta-pinch   configuration to generate a pulsed, high-energy-density plasma at   atmospheric pressure. Energy from a 20-kV, 6.05-μF capacitive   electrical discharge was inductively coupled to a sacrificial   aluminum thin film to produce a cylindrical plasma. Current   waveform analysis indicates an average power dissipation of 0.5   MW in the plasma. Electromagnetic modeling studies were used to   identify theta-pinch designs possessing characteristics favorable   to both plasma initiation and plasma heating. The discharge was   most robust when the induced current and rate of magnetic field   change were maximized. Minimizing the ratio of the coil's width   to its radius was also critical. Counter to intuition, a larger   diameter was found to be more successful. Spectroscopic studies   indicate that the discharge forms a heterogeneous plasma with a   dense, cylindrical plasma sheet confined by the walls of the   discharge tube surrounding a less energetic plasma in the center.   Al(II) emission in the outer plasma cylinder was temporally   aligned with the induced current whereas in the center it aligns   with the magnetic field. Ionization of support gas species (Ar,   He, and air) was not observed, although the identity of the gas   had a significant influence on the plasma reproducibility. The   optimized design utilized a 5.5-turn, 19-mm-diameter theta coil   with argon as the support gas. Sb(I) emission from an antimony   oxide solid powder sample deposited on the thin film was observed   primarily in the outer part of the plasma. Analyte emission shows   contributions from magnetic compression early in the discharge   and from the induced current late in the discharge. The discharge   produced analytically useful signals from solid antimony oxide   samples. Using spatially and temporally resolved detection, the   line-to-background ratio for Sb(I) was found to be greater than 4   for emission integrated from 55 to 120 μs.

      Address (URL): http://www.ingentaconnect.com/content/sas/sas/2011/00000065/00000001/art00009