Characterization of cold model cavity of cryocooled C-band 2.6-cell RF gun at 20 K

8th International Particle Accelerator Conference

Tanaka, T.^1 ; Sakai, T.^1 ; Nogami, K.^1 ; Hayakawa, K.^1 ; Hayakawa, Y.^1 ; Nakao, K.^1 ; Takatsuka, K.^1 ; Fukuda, M.^2 ; Satoh, D.^2 ; Takatomi, T.^2 ; Terunuma, N.^2 ; Urakawa, J.^2 ; Yoshida, M.^2

Laboratory for Electron Beam Research and Application, Institute of Quantum Science, Nihon University, 7-24-1 Narashinodai, Funabashi, Japan^1

High Energy Accelerator Research Organization, 1-1 Oho, Tsukuba, Japan^2

关键词: Anomalous skin effect;    Cryogenic measurement;    Diffusion bonding technique;    Linear expansion coefficient;    Monochromatic x-rays;    RF characteristics;    Ultraprecision machining;    Unloaded quality factors;   

Others  :  https://iopscience.iop.org/article/10.1088/1742-6596/874/1/012026/pdf
DOI  :  10.1088/1742-6596/874/1/012026

来源: IOP

【 摘 要 】

A cryogenic C-band 2.6-cell photocathode RF electron gun has been studied at Nihon University in collaboration with KEK for future use in a compact electron-accelerator based monochromatic X-ray source. The cold model cavity with an input coupler was fabricated at KEK in 2016 by ultraprecision machining and diffusion bonding techniques. The RF characteristics of the cavity obtained at cryogenic measurements have been in agreement with the result of the CST Studio simulation. The unloaded quality factor of ∼73000 has been obtained at the cavity temperature of 20 K, which is 5.5 times higher than that at room temperature and consistent with the simulation taking into account the anomalous skin effect of the cavity surface resistance. The input coupling coefficient of approximately 20 at 20 K has well reproduced the design value. The shift in the accelerating n-mode resonant frequency due to the cavity temperature change from 296.65 to 20 K has been 19.02 MHz, being 0.12 MHz greater than the value based on the linear expansion coefficients for copper by NIST.