Design and development of radio frequency output window for circular electron–positron collider klystron

Abstract

This paper presents the first phase of design, analysis, and simulation for the klystron coaxial radio frequency (RF) output window. This study is motivated by 800 kW continuous wave (CW), 650 MHz klystrons for the future plan of circular electron-positron collider (CEPC) project. The RF window which is used in the klystron output section has a function to separate the klystron from the inner vacuum side to the outside, and high RF power propagates through the window with small power dissipation. Therefore, the window is a key component for the high power klystron. However, it is vulnerable to the high thermal stress and multipacting, so this paper presents the window design and analysis for these problems. The microwave design has been performed by using the computer simulation technology (CST) microwave studio and the return loss of the window has been established to be less than −90 dB. The multipacting simulation of the window has been carried out using MultiPac and CST particles studio. Through the multipacting analysis, it is shown that with thin coating of TiN, the multipacting effect has been suppressed effectively on the ceramic surface. The thermal analysis is carried out using ANSYS code and the temperature of alumina ceramic is lower than 310 K with water cooling. The design result successfully meets the requirement of the CEPC 650 MHz klystron. The manufacturing and high power test plan are also described in this paper.

High power test of the power coupler for 325 MHz superconducting cavities with standing waves

“…The signal measured in the test cavity is stronger than the signal measured in the power coupler. Electron emission from the test cavity is stronger than from the RF window of the power coupler because the test cavity was made of aluminum and had a higher SEY (Secondary Electron Yield) than those of OFHC (Oxygen-Free High-Conductivity Copper) and TiN coating on the RF window [11,12]. When the vacuum trip occurred, the signal from the test cavity and the FPC1 was deformed very fast, and the vacuum interlock worked.…”