Pulse compressors have been widely used to generate very high peak RF power in exchange for the reduction in the RF pulse length for linear accelerators. As compared to a traditional SLAC Energy Doubler(SLED), a spherical pulse compressor is more compact while maintaining a high energy gain. A C-band spherical pulse compressor is studied in this paper, which consists of a dual-mode polarized coupler for producing two orthogonal TE11 modes simultaneously, as well as a resonant cavity working at TE113 mode for storing energy. Through optimizations, an average energy gain of 4.7 with a coupling factor of 6.6 can be achieved for such a spherical pulse compressor. The RF design of this pulse compressor has been finalized, the fabrication and measurement of prototype can be expected in the next step.

Numerical optimizations on couplers of the traveling wave accelerating structures usually require lots of calculation resources. This paper proposes a new technique for matching couplers to an accelerating structure in a more efficient way. It combines conventional Kroll method with improved Kyhl method, thereby simplifying the tuning and simulation process. We will present the detailed design of a constant-gradient C-band accelerating structure based on this new method.

As compared to conventional travelling-wave (TW) structures, parallel-coupled accelerating structures eliminate the requirement for the coupling between cells, providing greater flexibility in optimizing the shape of cells. Each cell is independently fed by a periodic feeding network for this structure. In this case, it has a significantly short filling time which allows for ultrashort pulse length, thereby increasing the achievable gradient. In this paper, a design of an X-band parallel-coupled TW structure is presented in detail.

As compared to conventional travelling-wave (TW) structures, parallel-coupled accelerating structures eliminate the requirement for the coupling between cells, providing greater flexibility in optimizing the shape of cells. Each cell is independently fed by a periodic feeding network for this structure. In this case, it has a significantly short filling time which allows for ultrashort pulse length, thereby increasing the achievable gradient. In this paper, a design of an X-band parallel-coupled TW structure is presented in detail.

Pulse compressors have been widely used to generate very high peak RF power in exchange for a reduction in the RF pulse length for linear accelerators. A C-band spherical pulse compressor is numerically studied for the linac of Super Tau-Charm Facility in this paper. Utilizing a dual-mode coupler for producing two orthogonal polarized TE11 modes, TE114 mode is chose for storing energy in resonant cavity enabling a Q0 over 1.3×105. By modulating the coupling factor to 8.6, an optimum average power gain of 4.8 can be achieved in the case of combing with a 3π/4 travelling wave accelerator. This paper concludes the optimum RF parameters of the pulse compressor, as well as the geometry tolerance is given for the next step machining.

Numerical optimizations on couplers of the traveling wave accelerating structures usually require lots of calculation resources. This paper proposes a new technique for matching couplers to an accelerating structure in a more efficient way. It combines conventional Kroll method with improved Kyhl method, thereby simplifying the tuning and simulation process. We will present the detailed design of a constant-gradient C-band accelerating structure based on this new method.

A 500 MHz normal-conducting (NC) cavity is being developed for Super Tau-Charm Main Rings which have a current of 2 A and a synchronous radiation energy loss of 410 keV per turn. This NC cavity operates in a higher order mode of TM020. Through optimizations, it results in a high quality factor and a low R/Q. This feature is beneficial to reduce the required detuning frequency so that the coupled bunch instabilities (CBIs) driven by the ac-celerating mode are greatly suppressed. It employs ferrite absorbers inside coaxial slots located at the node of the TM020 mode to heavily damp all of dangerous parasitic modes except from the TM020 mode.

Hefei Advanced Light Facility (HALF) injector comprises 40 S-band 3-meter traveling wave accelerating structures, capable of delivering electrons of full energy 2.2 GeV into the storage ring. To mitigate the emission degradation caused by dipole and quadrupole fields in the coupler cavity, the coupler design incorporates a racetrack and a short-circuit waveguide to eliminate this impact. This article presents an introduction to design of the traveling wave structure and the results of cold and high-power testing. We performed tuning and preliminary measurements on accelerating structure, resulting in meeting the single-cell phase deviation and accumulated phase deviation requirements of the project objectives while maintaining good measurement consistency.

Transverse deflection structures (TDS) have been widely used as diagnostic devices to characterize longitudinal properties of electron bunches in a linear accelerator. However, the conventional TDS can only measure either the horizontal or the vertical slice envelopes of electron bunches. In order to give full control of the angles of the transverse streaking field inside of the TDS to characterize the projections of the beam distribution on different transverse axes, we numerically investigate an X-band TDS with variable polarization in this paper. Through variable streaking direction, the orientation of the streaking field of the TDS is adjusted to an arbitrary azimuthal angle. This helps facilitate the development of next-generation TDS for the characterization of electron bunches, such as slice emittance measurement on different planes.

A superconducting (SC) 1.5 GHz (3rd harmonic) cavity is being developed for lengthening bunch and improving beam lifetime in the Hefei Advanced Light Facility (HALF) storage ring. This SC cavity is excited by an electron beam with 350 mA current, 1 nC charge, and ~6.7 ps length. This contribution presents optimizations on such a SC harmonic cavity in detail. Through optimizations it has a low R/Q < 45 Ω, which has potential to achieve a good bunch lengthening. It utilizes a large-radius beam pipe which traps the fundamental (1.5 GHz, TM010) mode, but allows all other cavity monopole and dipole higher-order-modes (HOMs) to travel into a room-temperature RF absorber. All of harmful HOMs are strong-ly damped using a pair of silicon carbide (SiC) rings. In addition, preliminary thermal analysis on the SiC rings is also described in this contribution