Time-resolved spectrographic techniques were used to obtain the profiles of A II lines emitted from a laboratory plasma. For the dense, low-temperature plasma studied, most of the broadening of the observed lines results from interactions of the emitter with free charges in the surrounding plasma. The plasma was created by discharging a previously- charged lumped-parameter delay line through a specially- constructed vessel containing an argon-hydrogen mixture. By means of a rotating-mirror shutter, light from the discharge was admitted to the spectrograph during a time interval when the intensity of the A II lines was constant to within about 10%. This time interval was chosen after monitoring the time dependence of the intensity of several A II lines with a monochromator-photomultiplier combination. A calibration spectrum was also obtained with a seven-step neutral density wedge in order to determine the response of the photographic emulsion. Of the twenty-four measureable A II lines recorded, fourteen yielded profiles which could be treated by a Voigt analysis. In this way the profiles could be corrected for the effects of instrumental and Doppler broadening. The electron number density was determined from the widths of the lines in multiplet 6 of the A II spectrum, previously measured by other workers. The results indicate considerable disagreement with the original theory of line broadening as developed by Griem and his co-workers. The half-widths of the lines reported here are up to 4.0 times wider than predicted theoretically. The line shapes appear to be Voigt functions, rather than the predicted Lorentzian profiles. The measurements are in good agreement with those of other workers, where comparisons could be made. Measurements of some of the lines reported here do not appear to have been published elsewhere. / Science, Faculty of / Physics and Astronomy, Department of / Graduate

The development of low noise electronic equipment has facilitated the observation of ionic conduction pulses under alpha bombardment in liquid helium I and II, and a substantial extension of previous observations in liquid argon. Electron mobility in argon had been measured in fields between 2 kV/cm. and 200 kV/cm., the high field values agreeing with the order of magnitude previously reported. The scattering cross section for electrons is found to be of the order one hundredth that observed in gaseous argon. The low mobility of positive ions in liquid argon, observed for the first time, also shows that the liquid does not behave as a dense gas. Mobilities for both positive and negative ions in liquid helum I and II have been measured, also for the first time. The positive ions have low mobilities of the order of the positive ion mobility in argon, but the anomalously low mobility of the negative ions has not been explained. Ionic recombination, investigated in these liquids through direct current and pulse amplitude methods, is not described by the existing theory. Considerations are given which invalidates the model on which this theory is based, and an alternative model is suggested. / Science, Faculty of / Physics and Astronomy, Department of / Graduate

Lifetime techniques have been used to measure the direct annihilation rate in Argon gas as a function of temperature. In order to accomplish this, a pressure chamber capable of holding 10 amagats of gas at 300°C was designed and constructed. The temperature of the Argon gas was varied between 140°K and 480°K. The results were collected at specific temperatures for gas densities of 8.0 and 10.2 amagats. The direct annihilation rate was found to be a decreasing function of temperature meaning it is a decreasing function of velocity. The direct annihilation rate decreased by 30% over the range investigated. Various functions in temperature were fitted to the results by the least squares technique. The shoulder width-density product was found to be constant with temperature indicating that the shoulder annihilations take place at velocities significantly greater than thermal velocities. The statistics on the ortho-positronium lifetime were not sufficiently good to see a temperature variation of this component. A comparison of an electric result with these results gave a position - Argon atom scattering rate of 9.0xl0¹¹secˉ¹amˉ¹. This was assuming that the scattering rate was independent of velocity. / Science, Faculty of / Physics and Astronomy, Department of / Graduate

Relative transition probabilities were measured for several transitions in the visible ArII spectrum. An argon-nitrogen pulsed arc of duration 90 μsec, with electron densities of 2.3 x 10¹⁷ cm⁻³ and electron temperature of 2.6 ev, was used as a source of radiation. Measurements were performed with photographic diagnostics and a rotating-mirror shutter system. The fourteen values of relative transition probabilities obtained agreed reasonably well with previous measurements. / Science, Faculty of / Physics and Astronomy, Department of / Graduate

Thesis (Ph. D.)--Washington State University, December 2009. / Title from PDF title page (viewed on Feb. 8, 2010). "Department of Physics and Astronomy." Includes bibliographical references.

Thesis (M.S.)--Ohio State University. / Includes bibliographical references (leaves 60-62). Available online via OhioLINK's ETD Center

The interest in the detection of radioargon isotopes--³⁷Ar, ³⁹Ar, and ⁴²Ar--is increasing important for on-site inspections within the Comprehensive Nuclear-Test-Ban Treaty verification regime. In an underground nuclear explosion ³⁷Ar is produced by ⁴⁰Ca(n,[alpha])³⁷Ar reaction in surrounding soil and rock. With a half-life of 35 days, ³⁷Ar provides a signal useful for confirming the location of an underground nuclear event. The development of detector systems is underway. This work produced radioargon isotopes by three methods for the development and testing of radioargon detection systems. The irradiation of argon gas at natural enrichment in the 3L facility within the Mark II TRIGA reactor facility at The University of Texas at Austin provides a source of ³⁷Ar for the calibration of the ULBPC in development at PNNL. The ⁴¹Ar activity is measured by the gamma activity using an HPGe detector after the sample is removed from the core. Using the ⁴¹Ar/³⁷Ar production ratio and the ⁴¹Ar activity, the amount of ³⁷Ar created is calculated. The ⁴¹Ar decays quickly (half-life of 109.34 minutes) leaving a radioactive sample of high purity ³⁷Ar and only trace levels of ³⁹Ar. The second method was the irradiation of a calcium-containing compound. This option is not the best match for the TRIGA reactor type due to the thermal neutron flux. Therefore, the use of the Cd-lined 3L irradiation canister minimized the thermal activation of impurities while still allowing the majority of the ⁴⁰Ca(n,[alpha])³⁷Ar reactions occur. The third and last irradiation technique was a large volume, in-core gas facility developed at The University of Texas at Austin MARK II TRIGA reactor to produce a sample of ⁴²Ar with an activity above 1 mBq. The method requires a large volume, 1.4 L, of natural argon gas (99.6003% ⁴⁰Ar) at about 1 atm and three-12 hour irradiation periods. The production of ⁴²Ar requires a double capture to be produced from the stable 40Ar isotope. This method produced 940 kBq of ³⁹Ar, 3.08 MBq ³⁷Ar, 114 GBq ⁴¹Ar, and 0.311 Bq ⁴²Ar at the end of the final irradiation period. / text

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