The high β operating regime of spherical tokamaks (ST), such as in NSTX and MAST, make them attractive fusion devices. To attain the high β’s, there is a need to heat and to drive currents in ST plasmas. While ST plasmas are overdense to conventional electron cyclotron (EC) waves, electron Bernstein waves (EBW) offer an attractive possibility both for heating and for driving plasma currents. We...

We present electron density and temperature measurements from an active region observed above the limb with the Solar Ultraviolet Measurements of Emitted Radiation spectrometer on the Solar and Heliospheric Observatory. Density-sensitive line ratios from Si viii and S x indicate densities greater than 10 cm as high 3 as 200 (or 145 Mm) above the limb. At these heights, static, uniformly heated ...

We study the ionization dynamics in intense laser-droplet interaction using three-dimensional, relativistic particle-in-cell simulations. Of particular interest is the laser intensity and frequency regime for which initially transparent, wavelength-sized targets are not homogeneously ionized. Instead, the charge distribution changes both in space and in time on a subcycle scale. One may call th...

CO2 laser-plasma interaction provides a unique parameter space for particle acceleration in a gas jet plasma taking place at a critical plasma density ncr ~ 10 cm and even at higher densities (3~10 ncr) of 10μm radiation. Here we report the latest results of our study of electron acceleration in a wide range of plasma densities 1~10 ncr using a multi-TW CO2 laser system at the UCLA Neptune Labo...

In the present paper, the possibility of generation of thin dense relativistic electron layers is shown using the analytical and numerical modeling of laser pulse interaction with ultra-thin layers. It was shown that the maximum electron energy can be gained by optimal tuning between the target width, intensity and laser pulse duration. The optimal parameters were obtained from a self-consisten...

The theory of electromagnetically induced transparency ~EIT! in a plasma @S. E. Harris, Phys. Rev. Lett. 77, 5357 ~1996!# is examined in the context of a bounded system. It is found via particle simulations that an overdense plasma slab reflects short pulses even in the presence of an EIT passband. However, a two-frequency laser, or ‘‘beatwave,’’ will cascade into a Stokes satellite with a freq...

Blackbody levels of emission in the electron cyclotron range of frequencies have been observed from an overdense (vpe;3vce) Madison Symmetric Torus @Dexter et al., Fusion Technol. 19, 131 ~1991!# reversed field pinch plasma, a result of electrostatic electron Bernstein waves emitted from the core and mode converted into electromagnetic waves at the extreme plasma edge. Comparison of the measure...