本研究藉由有限單元計算軟體ANSYS針對1.5 GHz共振腔的主腔體進行結構與電磁場的耦合分析，基於以光速通過腔體軸心的帶電粒子之加速效應，發現雙腔體1.5 GHz共振腔的兩個主腔體之間的連接部分長度對其電磁場特性有顯著影響；在多種考慮之下，該連接部分最終優化設計為12 mm。由於次低頻TM010電磁場共振模態可提供帶電粒子最有效的加速度，因此所有的優化和研究皆以此模態為主。經過網格細化的收斂分析後，採用特定網格計算在各種條件下雙腔體共振腔的次低頻TM010電磁場的共振頻率。隨著溫度從300 K降至 2 K，銅腔體的電磁場共振頻率增加0.361％，鈮腔體的共振頻率則因熱收縮較低僅增加0.172％。此外，考慮腔體結構的彈塑性行為，以增量計算進行調頻。當共振腔受到101.3 kPa的外部壓力，即為一大氣壓的內外壓差下，當小圓管(SBP)端固定不動時，大圓管（LBP）端的軸向位移為 -0.18318 mm，而電磁場共振頻率從1.507005695 GHz減少至1.506709303 GHz。隨著LBP端面的軸向拉伸位移量逐漸增加至超過2mm時，彈塑性行為首先發生在大圓管與主腔體之間的連接處曲面部分。進行調頻的標準計算程序為依序施加軸向位移UZ、再反向施加軸向位移-2Uz、最終釋放所有負載；此時共振腔的殘餘形變會使其次低頻TM010電磁場的共振頻率改變，且共振頻率變化量與LBP端的殘餘軸向位移量為線性變化。

Length of the connection section between the main cavity structures of a 2-cell 1.5 GHz radio-frequency cavity has a significant effect on its electromagnetic characteristics. With the structure-electromagnetism coupled analysis by finite element code ANSYS, this connection section is herein optimized to a length of 12 mm based on its accelerating effects on charged particles passing through the cavity axis with light speed. It is firstly investigated that the second TM010-like mode provides most effective acceleration and thus all the optimization and following studies are mostly focused on this mode. With the fine mesh, which is verified by the convergence test, resonance frequencies of the second TM010-like mode of this 2-cell cavity at various conditions are computed. As the temperature decreasing from 300 K to 2 K, this resonance frequency of the copper cavity increases 0.361%, while that of the niobium cavity increases only 0.172% due to its lower thermal contraction. Also investigated is the frequency-tuning process by considering elastoplastic behavior of the cavity structure with incremental computations. The longitudinal displacement of the LBP (Large Beam Pipe) end is -0.18318 mm when the cavity is initially applied with an external pressure of 101.3 kPa, i. e., 1 atm, whereas the resonance frequency changes from 1.507005695 GHz to 1.506709303 GHz. Then the longitudinal displacement of the end surface of LBP is incrementally increased to find that the elastoplastic behavior firstly happens at the curved section between LBP and main cavity structure when the applied longitudinal displacement beyond 2 mm. A load cycle is completed by sequentially applying a longitudinal displacement UZ, a negative displacement -2Uz, and finally releasing all the loads. Residual deformations on the cavity are thus generated and correspondingly change its resonance frequency of the second TM010-like mode. It is found the frequency shift varies linearly to the residual longitudinal displacement of the LBP end.

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