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(a) Longitudinal and (b) transverse cross section views of the PIC simulation model of the structure with axisymmetric elliptical central cell sidewall in CST. 1, the 1.0 mm wide sidewall strip section assigned with SEE properties; 2, the sources of electrons where the peak electric field is located.
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A 17 GHz single cell, standing wave, copper accelerator structure with an axisymmetric elliptical central cell sidewall was tested for internal and downstream dark current as a function of gradient up to 93 MV/m. The elliptical sidewall was predicted to suppress the internal dark current and the lower order multipactor modes as compared with a prev...
Context in source publication
Context 1
... verify the calculation results from our in-house code, a series of CST PIC simulations were carried out using the E structure model and the setup shown in Fig. 5, similar to that reported for the straight sidewall structure (S structure) in [5]. On the elliptical sidewall, a strip section with a width of 1.0 mm was assigned with secondary electron emission properties (Vaughan's model). Sampling the internal dark current generated by SEE using such a strip is accurate, since the azimuthal motion ...
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Citations
... Research on RF breakdown in short-pulse SWFA is complementary to previous and ongoing breakdown studies in the high-gradient community, where extensive research has been conducted to understand the various breakdown mechanisms. Different approaches have been investigated to mitigate the RF breakdown risk, such as cryogenic operation [34], curved surface to reduce internal multipacting current [35], and multipacting suppression by external magnetic field [36]. ...
Structure wakefield acceleration (SWFA) is one of the most promising AAC schemes in several recent strategic reports, including DOE's 2016 AAC Roadmap, report on the Advanced and Novel Accelerators for High Energy Physics Roadmap (ANAR), and report on Accelerator and Beam Physics Research Goals and Opportunities. SWFA aims to raise the gradient beyond the limits of conventional radiofrequency (RF) accelerator technology, and thus the RF to beam energy efficiency, by reducing RF breakdowns from confining the microwave energy in a short (on the order of about 10 ns) and intense pulse excited by a drive beam. We envision that the following research topics, within the scope of AF7, are of great interest in the next decade: advanced wakefield structures, terahertz and sub-terahertz (THz) structures, and RF breakdown physics. Research on SWFA in the above directions would directly contribute to long-term large-scale applications, including AAC-based linear colliders and compact light sources. There is also potentially a strong synergy between SWFA and other AAC concepts, when structures are combined with plasmas into hybrid AAC schemes. Research on novel structures is at the core of advancing SWFA, and is critical to future AAC-based linear colliders; at the same, it has a strong synergy with other directions, such as cavity designs, high-power microwave systems and sources, and compact light sources.
