X-ray diagnostics for the Levitated Dipole Experiment

Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Nuclear Engineering, 2004.Includes bibliographical references (p. 77-79).Initial plasma experiments in the Levitated Dipole Experiment focus on producing hot electron, high beta plasmas using a supported dipole configuration. Plasmas are created using multifrequency ECRH and it is therefore expected that most of the plasma energy will be stored in the fast electrons, Te > 100 keV. As a consequence, x-ray flux from bremsstrahlung emission is expected to be easily detectable. The energy spectrum of the x-ray emission below 740 keV is measured by a four channel pulse height analyzer using cadmium zinc telluride detectors. In addition, a single sodium iodide detector, which views energies up to 3 MeV, measures the intensity of the hot electron population. The electron temperature may be inferred from the x-ray energy. X-ray measurements are essential in diagnosing the effectiveness of various ECRH configurations. The design and installation of the pulse height analyzer are discussed in addition to the preliminary results from first plasma experiments.by Jennifer L. Ellsworth.S.M