超導共振腔體中央直線段長度對電磁場特性之影響

Length Effect of Central Straight Section on the Electromagnetic Characteristics of Superconducting Radio-frequency Cavity

呂旼儒(Ming-Ru Lu)

指導教授 ： 葉孟考

國立清華大學/工學院/動力機械工程學系/碩士(2014年)

摘要

本文主要是對超導共振腔體進行結構變形與高頻電磁場分析，根據不同模擬方式得到之結果進行探討。使用商用有限單元分析軟體ANSYS建立超導共振腔之模型來進行分析，由於分析時所需之基頻共振模態為TM010之軸對稱形式，所以只建立結構之四分之一模型，搭配適當之邊界條件並設定單元之相關電磁常數即可代表全模型之模擬結果。於使用HF120單元進行模擬時，討論選擇此單元之一階或是二階模式對超導共振腔體之高頻電磁場分析結果造成之影響，分別就共振頻率之收斂性與腔體表面磁場之分布進行探討。文中進行實驗驗證，實驗時使用之腔體以銅製作，分別探討實驗腔體受到軸向位移、溫度變化、軸向負載、外部壓力差時腔體之共振頻率變化量是否與模擬相等。文中也將討論改變腔體中心直線段長度對於腔體共振頻率之影響，並分別討論腔體未變形時與腔體受到內外壓力差產生之結構變形與受到溫度變化時之共振頻率之改變 。

關鍵字

超導共振腔體 ； 共振頻率 ； 表面磁場 ； 結構變形

並列摘要

This study investigates the structure deformation and high-frequency electromagnetic characteristics of a superconducting radio frequency (SRF) cavity. The numerical model is established by the commercial finite element software ANSYS. Since the fundamental resonance mode of this SRF cavity is axially symmetric, called the TM010 mode, one quarter of the full structure with proper boundary conditions is modeled. Two options of HF120 element, the first order and the second order elements are used to investigate the difference and it is concluded that second-order options shall be adopted for this study. The simulation results are verified with experimental tests on a copper cavity. The resonance frequency drifts of this cavity under various situations, such as axial displacements, temperature change, axial loading and external pressure are all measured to compare with the simulation results. The effects of length of the central straight section on deformation and resonance frequency of the 1.5 GHz cavity are also evaluated.

並列關鍵字

SRF cavity ； Resonance frequency ； Surface magnetic field ； Structural deformation

參考文獻

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