LDRD Final Report for 01-ERD-100 FLIRT: A Magnetic Field Topology Diagnostic for Spheromaks and Other Self-Organized Magnetically Confined Plasmas

Tangled magnetic field lines are common in laboratory and space plasmas, but determining the geometrical structure of magnetic fields in the presence of plasma is a difficult and still unresolved problem. To address this open question we developed and tested a new technique for measuring the magnetic field-line topology in magnetically confined plasmas. Our field-line tracing diagnostic (FLIRT) uses a high-power, short-pulse laser to launch a burst of energetic ({approx}100 keV) electrons from a target passing through the plasma. These electrons then generally follow magnetic-field lines until they strike a solid surface, where a burst of x-rays is produced. The field-line connection length can be determined from the time delay between the laser pulse and the burst of x-rays. The topology of the field lines can be inferred by measuring the connection length as a function of initial target location inside the plasma. Measuring the spatial distribution of x-ray production provides further information on the field topology, including the effects of magnetic field fluctuations and stochasticity. The goals of this experiment were to test the appropriate x-ray detectors; measure the background x-ray emission in a spheromak plasma; measure the energetic electron production by a short-pulse, high-power laser; make preliminary measurementsmore » of the edge field line topology in the Sustained Spheromak Physics Experiment (SSPX), and perform analytic studies of electron production. These results are reported in detail in three publications listed. A brief summary is given.« less