本文對雙腔型共振腔體外型進行設計，也對設計後之腔體給予軸向位移，進行彈塑性結構變形之分析。先針對1.5 GHz單腔體分析，了解TM010-like電磁場共振模態之特性，並以此為基礎對雙腔體共振腔主結構之直線段長度、連接段長度、加速電壓比值、耦合係數、大小圓管長度與並聯阻抗和品質因數之比值(R/Q)進行調整。文中運用有限單元軟體ANSYS建立模型，在合理邊界條件下建立1/4模型，分析之電磁場為TM010-like之對稱模態形式。研究發現，在直線段長度為17.167 mm且連接段為7.5 mm時，具有最佳的加速電壓比值，而大小圓管長度增加的影響甚低，並聯阻抗與品質因數之比值(R/Q)已達到設定之要求。
文中也以銅材料參數進行模擬，給予大圓管端軸向位移，探討在彈塑性行為下之應力分布與電磁場共振頻率之變化，並研究改變厚度對於雙腔體共振腔之電磁場共振頻率之影響。本文亦探討彈塑性行為對於結構振動模態之影響，可知在受到軸向拉伸4 mm時，前三模態之結構自然頻率值下降25 %，受軸向壓縮4 mm之前三自然模態頻率值下降55 %。本文同時討論鈮材料拉伸曲線使用雙線性曲線擬合與多線性曲線擬合兩種材料模型對於電磁場共振頻率之影響，發現採用多線性曲線擬合可得較高之殘留位移量與頻率飄移量，兩者差異分別為4.64 %與6.12 %。CPU計算時間較採用雙線性曲線擬合的時間多出2倍。

In order to design a 2-cell radio-frequency (RF) cavity, the characteristics of TM010-like mode based on 1-cell 1.5 GHz RF cavity is studied first. There are two TM010-like modes for 2-cell 1.5 GHz RF cavity, π/2-mode and π-mode, respectively. The lengths of the straight sections of main cavity structure and of the connecting pipe are both optimized to reach higher ratio of integrated accelerating voltage for copper cavity. Both of coupling factor (k) and field flatness (FF) are considered as the design basis, whereas, the ratio of shunt impedance to quality factor (R/Q) is also calculated. The 1/4 numerical models are built by the finite element code ANSYS since the TM010-like resonance mode is symmetric. The straight section length of the cavity equator is optimized to be 17.167 mm, whereas the connecting pipe 7.5 mm herein.
The frequency shift of π-mode after pre-tuning process for copper RF cavity is verified with elastoplastic modeling, and the distribution of effective stress at various thickness changed is obtained.
The natural frequency of 2-cell copper cavity during elastoplastic process are obtained. The first three natural frequencies decreases 25 % and 55 % as the cavity stretched and squeezed to 4 mm, respectively. Niobium RF cavity is analyzed with the elastoplastic stress-strain curve fitted by both bilinear curve and multilinear curves. It is found that the RF cavity with multilinear curve fitting has 4.64 % larger residual deformation and 6.12 % higher frequency shift for π-mode than the results obtained from the analysis model with bilinear curve fitting. The CPU computation time of multilinear curve fitting is doubled when compared with that having a bilinear one.

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