發展高磁場極短週期之超導聚頻磁鐵提升加速器光源亮度

Abstract

聚頻磁鐵是第三代先進加速器光源(同步輻射)最重要的出光設備，屬於插件磁鐵的一種；在加速器設施中，插件磁鐵是用來產生多樣化光譜特性，並增加同步輻射的光通量(photon flux)與光亮度(photon brilliance)，更能藉由該設備來產生各種極化光源。透過設計不同類型的插件磁鐵，可使同步輻射的光譜特性符合各式各樣的科學實驗與科技上的應用。插件磁鐵其一重要發展方向，是開發新結構、採用新材料來縮短週期長度並增強磁場強度，以提升光源的性能與發光效率。本研究即著重於此─嘗試利用各式超導材料開發新結構，例如:NbTi線材、YBCO線材、YBCO塊材等不同材料，來研製超導聚頻磁鐵。期盼採用新材料使磁列磁場強度有大幅度突破，極短週期磁列下能產生更高磁場，有利當前中能量的同步輻射光源，頻譜能達到更高的硬x光能量範圍且有較高光亮度；換言之，加速器便能採用較低的運作能量來產生高能量之光譜，加速器設施的造價即能隨運作能量調降而大幅降低。另一方面，本研究採用超導材料開發各種偏振光聚頻磁鐵，並利用圓偏振光只存在第一諧振光譜線的特性，提高發光效率。 本研究範圍將從光譜理論探討與改進、磁鐵概念設計與製作到磁場量測與分析。磁鐵研製規劃是先投入採用超導線材，利用超導電磁鐵結構製作聚頻磁鐵；其次採用高溫超導塊材進行極短週期聚頻磁鐵的研製，利用其擄獲強磁的特性達到目的，目前此材料應用是起步階段，是相當新穎的領域；為使用高溫超導塊材，必需搭配研發建造相對應之高磁場充磁磁鐵。光譜探討部分則提出算法與定義之改良並提升光譜計算精度；此外，針對自由電子雷射(FEL)的光亮度增強議題，則對兆瓦高功率光源(Terawatt XFEL)做光束橫向能量分布分析。

Insertion devices play important rule in synchrotron accelerator facility. By designing different kind of insertion devices (ID), the spectrum of the synchrotron radiation from the insertion deices can provide a variety of high brilliance and variable polarized photon spectrum. Therefore, the insertion devices can promote the synchrotron accelerator facility to provide a great diversity of synchrotron light for many kinds of application experiments. An important future development is to improve the brilliance and efficiency by developing undulator with new materials to increasing the magnetic flux density in an extremely short period, and this is the main purpose of this study. New technologies about superconducting materials, like the NbTi-wire, YBCO-wire and YBCO-bulk, having potential to produce higher magnetic field of an undulator, were considered. Hereinafter, the medium energy accelerator facility can have the enhanced brilliance and the improved energy of hard x-ray. In other words, the beam energy can be lower down, and the construction price of the accelerator facility hence decreases. On another aspect, developing various polarized high field undulator is also one main purpose of this study. It was considered to improve the efficiency by employing the property of circular polarized light. In this study, the improvement of theory of synchrotron radiation, superconducting magnet design, manufacture, measurement and analyzing were all mentioned. For the development of undulator: first, the development of superconducting elliptical polarized undulator was discussed; then, the YBCO-bulk material was introduced to make a stagger undulator, which is in a preliminary stage; a high field magnetizing system was constructed for the research of YBCO-bulk undulator. Meanwhile, some new points of view about spectrum were proposed based on the study work of the theory of synchrotron radiation. Besides, one issue about Terawatt (TW) X-ray free electron laser was also discussed by analyzing transverse photon beam distribution.