The Effects of Structural Deformation on the Characteristic of the Electromagnetic of the Superconducting Radio-Frequency Cavity

• Main Authors: KUO, HUNG-YI, 郭泓毅
• Other Authors: Meng-Kao Yeh
• Format: Others
• Language: zh-TW
• Published: 2013
• Online Access: http://ndltd.ncl.edu.tw/handle/62572449948051076468

碩士 === 國立清華大學 === 動力機械工程學系 === 101 === This thesis examines the structure deformation and electromagnetic resonance characteristic of a superconducting radio frequency (SRF) cavity. This SRF cavity is a shell-liked structure; it not only deforms but also shifts the electromagnetic resonance frequencies while being externally loaded. The finite element software ANSYS is used for numerical simulation; a single-model process links the structural deformation and its relative high-frequency electromagnetic computations and thus improves both the efficiency and accuracy. Proper boundary conditions and material properties are assigned to the model, while external loading such as surface pressure, longitudinal displacement and temperature difference were applied on the model for structural deformation computing only. Characteristics of the electromagnetic field, especially the fundamental resonance mode, of the deformed cavity with various thickness, external loading conditions, and mechanical properties, are discussed. Convergence test on the resonance frequency of the unloaded SRF cavity was firstly performed to determine the suitable element density, then various virtual Young’s modulus which are assigned to the interior vacuum space of the cavity with particular thickness and Young’s modulus but under either surface pressure or longitudinal compression to determine the upper bound of the virtual Young’s modulus by examine its convergence on both the maximum von Mises stress and the resonance frequency. With fixed mesh and virtual Young’s modulus, the effects of mechanical properties including Young’s modulus, Poisson ratio, and coefficient of thermal expansion, on the drift of electromagnetic resonance frequency under various external loading were systematically studied. In practical, the SRF cavity is formed from a uniform plate but turn out its final thickness varies along the cavity wall due to uneven stretching during machining. Therefore, it is essential to establish a complete matrix on the effects of uniform thickness on the structure deformation and consequent frequency drift of the SRF cavity, so that an equivalent thickness of a real cavity could be estimated after measuring its resonance frequency shift for the cavity under various external loads. And then the equivalent thickness could be used to predict further physical behavior of the real cavity by numerical simulations.