Effects of the transversely nonuniform plasma density in a blowout regime of a plasma wakefield accelerator.

We present an analytical study on the effects of the transverse plasma gradient in the blowout regime of a plasma wakefield accelerator. The analysis departs from a simple ballistic model of plasma electrons and allows us to derive a complete analytic solution for the pseudopotential and, consequently, for the wakefield. We demonstrate that the transverse plasma gradient modifies the bubble shape and affects the wakefield; namely, the dipole plasma gradient results in a dipole component of the wakefield.

Suppression of Deflecting Forces in Planar-Symmetric Dielectric Wakefield Accelerating Structures with Elliptical Bunches.

Wakefield based accelerators capable of accelerating gradients 2 orders of magnitude higher than present accelerators offer a path to compact high energy physics instruments and light sources. However, for high gradient accelerators, beam instabilities driven by commensurately high transverse wakefields limit beam quality. Previously, it has been theoretically shown that transverse wakefields can be reduced by elliptically shaping the transverse sizes of beams in dielectric structures with planar symmetry.

Observation of High Transformer Ratio of Shaped Bunch Generated by an Emittance-Exchange Beam Line.

Collinear wakefield acceleration has been long established as a method capable of generating ultrahigh acceleration gradients. Because of the success on this front, recently, more efforts have shifted towards developing methods to raise the transformer ratio (TR). This figure of merit is defined as the ratio of the peak acceleration field behind the drive bunch to the peak deceleration field inside the drive bunch.

Electron emission projection imager.

A new projection type imaging system is presented. The system can directly image the field emission site distribution on a cathode surface by making use of anode screens in the standard parallel plate configuration. The lateral spatial resolution of the imager is on the order of 1-10 μm.