The Dynamic Stark Effect: Exploiting Virtual Atomic States to Measure Electric Fields in Plasmas
presented by Dr. Elijah H. Martin, Oak Ridge National Laboratory
Wednesday, Jan. 25, 7:30 - 8:30pm, Woods Labs 216
In order for fusion to become a viable source of power, prototype systems must be advanced to reactor-like specifications. The physical mechanisms of wave heating and current drive processes in the bulk hot plasma of thermonuclear reactors are generally well identified; however, the wave-plasma interaction in the cold plasma edge is not yet fully understood. Non-perturbative diagnostics are required due to the large energy flux traversing the space associated with the corresponding RF antennas/launchers. An active spectroscopic technique to measure the electric field driving wave-plasma interactions, density fluctuations, and other key parameters, based on Doppler-free saturation spectroscopy (DFSS), is currently being pursued to advance fusion science. DFSS yields measurements with extreme spectral resolution, but in order to accurately extract the electric and magnetic field vectors from the spectra, state-of-the-art quantum mechanical modeling is required. I will discuss the physics associated with the model developed at Oak Ridge National Laboratory over the last decade. In particular, the dynamic Stark effect will be highlighted and differentiated from the well known static equivalent. Experimental data obtained using both polarized passive optical emission and DFSS will be presented.
Elijah H. Martin graduated from NC State University in 2007 with a B.S. degree in physics and nuclear engineering, and in 2008 began graduate studies at NCSU under the direction of Dr. Steven Shannon. He conducted his doctoral research in the Fusion and Materials for Nuclear Systems Division at Oak Ridge National Laboratory (ORNL) in collaboration with Dr. John Caughman. Elijah graduated in 2014 with a Ph.D. degree in nuclear engineering and accepted a Fusion Energy Postdoctoral Research Fellowship at ORNL. In 2016 Dr. Martin became a staff scientist at ORNL. His research is geared towards advancing heating and current drive methods in the thermonuclear reactor through the measurement of time-periodic electric fields by means of advanced spectroscopic techniques.