The Cerenkov wake excited by a particle beam or a short laser pulse in a perpendicularly magnetized plasma is analyzed. The wake couples to electromagnetic radiation of approximate frequency v p at the plasma/vacuum boundary. The radiation amplitude is v c ͞v p times the amplitude of the wake excited in the plasma (for a sharp boundary). Particle-in-cell simulations verify the scaling laws. Since plasma wakes as high as a few GeV͞m are produced in current experiments, the potential for a high-power (i.e., GW) coherent microwave to THz radiation source exists. [S0031-9007(97)

We propose a layout estimation method for multi-layered ink using a measurement of the line spread function (LSF) and machine learning. The three-dimensional printing market for general consumers focuses on the reproduction of realistic appearance. In particular, for the reproduction of human skin, it is important to control translucency by adopting a multilayer structure. Traditionally, layer design has depended on the experience of designers. We, therefore, developed an efficient layout estimation to provide arbitrary skin color and translucency. In our method, we create multi-layered color patches of human skin and measure the LSF as a metric of translucency, and we employ a neural network trained with the data to estimate the layout. As an evaluation, we measured the LSF from the computer-graphics-created skin and fabricate skin using the estimated layout; evaluation with root-mean-square error showed that we can obtain color and translucency that are close to the target.

No abstract

In the plasma beat wave acceleration scheme, the ponderomotive force of a two-frequency laser pulse resonantly drives a large amplitude (E es ≈3 GV/m) relativistic electrostatic plasma wave. The electro-static (es) wave does not couple to the vacuum modes and its energy is dissipated in the plasma. With a static magnetic field B 0 z applied perpendicularly to the laser beam propagation axis x, the two-frequency laser pulse couples to the L branch of the XO mode of the magnetized plasma through Cerenkov radiation. The electromagnetic component (em) of the XO mode couples to the vacuum mode. The plasma wave is not affected by the transverse magnetic field, and measuring the characteristic of the emitted radiation thus provides an in-situ diagnostic for the beat-wave-excited accelerating structure (amplitude, phase, and damping for example). Additionally, the mechanism of interest is a possible source for a gigawatt terahertz radiation source.

No abstract