Advanced Concepts and Future Directions
Tech 12: Injection, Extraction, and Transport

Paper	Title	Page
MOP159	Ionization-Induced Trapping in Laser-Plasma Accelerators and Synchrotron Radiation from the Betatron Oscillation	394
	M. Chen, E. Esarey, C.G.R. Geddes, W. Leemans, C.B. Schroeder LBNL, Berkeley, California, USA D.L. Bruhwiler, E. Cormier-Michel Tech-X, Boulder, Colorado, USA
	Funding: This work is supported by the U.S. DOE Office of High Energy Physics under Contract No. DE-AC02-05CH11231, and NNSA, NA-22, and used the computational resources of NERSC. Ionization injection into a laser wakefield accelerator is studied by multi-dimensional particle-in-cell (PIC) simulations. To obtain low energy spread beams we use a short region of gas mixture (H+N) near the start of the stage to trap electrons, while the remainder of the stage uses pure H and is injection-free. Effects of gas mix parameters, including concentration and length of the mixture region, on the final electron injection number and beam quality are studied. Two dimensional PIC simulations show the injected electron beam has filament structures in the plane perpendicular to the laser polarization direction in early time and this structure disappears later due to the betatron oscillation of the electrons in the wakefield. Synchrotron radiation from the accelerated electrons is calculated by a post processing code - Virtual Detector for Synchrotron Radiation (VDSR).