Abstract
The longitudinal shape, i.e., the current profile, of an electron bunch determines the transformer ratio in a collinear wakefield accelerator and thus methods are sought to control the longitudinal bunch shape. The emittance exchange (EEX) appears to be promising for creating a precisely controlled longitudinal bunch shapes. The longitudinal shape is perturbed by two sources: higher-order terms in the beam line optics and collective effects and these perturbations can lead to a significant drop of the transformer ratio. In this paper, we analytically and numerically investigate the perturbation to an ideal triangular longitudinal bunch shape and propose methods to minimize it.
Highlights
Methods for shaping the profile of an electron bunch in transverse phase space have long been available to the accelerator designer
While we focus on the collinear wakefield accelerator, since it directly bears on our research program, most of the results in this paper are relevant to applications requiring precise longitudinal bunch shapes
To motivate the analysis in the rest of this paper, we briefly compare the quality of the triangular current profile generated in the ideal case [Eq (8)] with the realistic emittance exchange (EEX) beam line based on GPT simulations that includes finite emittance, thickness of transverse deflecting cavity (TDC), higher-order optics, space charge (SC), and 1D coherent synchrotron radiation (CSR) [17]
Summary
Methods for shaping the profile of an electron bunch in transverse phase space have long been available to the accelerator designer. We use the particle tracking simulation code GPT [9] to numerically examine the efficacy of our LBS beam line (the mask þ EEX method) in generating triangular longitudinal bunch shapes for generating a high transformer ratio in the collinear wakefield accelerator application. [Notice that Fig. 1 includes a fundamental mode accelerating cavity (FMC) to eliminate the so-called “thick lens effect” of the transverse deflecting cavity (TDC) [12] It is ignored but is included in the figure since it will be used in later sections of the paper.] We define Xm 1⁄4 ðxm; x0m; zm; δmÞT to be the 4D particle coordinates along the beam line (Fig. 1). The momentum exchange occurs in the first section of the beam line (DL1 þ TDC) and the position exchange occurs in the second (TDC þ DL2) and the entire beam line is needed to complete the total exchange
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
