臺灣博碩士論文加值系統

同步輻射光對許多研究領域而言是極重要的光源，因此產生同步輻射光的電子束在加速器中運行時的穩定性便是一項重要課題。其中電子束的縱向不穩定現象和高頻腔參數的設定有關，並且高頻腔的參數會影響電子束長度，因此電子束長度可作為設定高頻腔運轉參數的參考依據。本論文為以電子束的感應電磁波信號，以頻譜分析的方法來測量電子束長度。我們所採用的方法是利用射束位置偵測器(BPM)，擷取電子束運行時在儲存環真空腔壁上的感應電流，傳輸至頻譜分析儀觀察，並選取電子束靜態模次(monopole mode)的頻譜內容作分析，藉由在兩個不同電流在不同頻率的強度比值相比較，並以其中可近似為自然電子束長度(natural bunch length)的低電流電子束長度作為參考基準，得到高電流時的電子束長度。由於本論文的主要目的為發展一個測量電子束長度的方法，因此先從電子束運動較為單純的單電子束（single bunch）條件下進行測量，並將其結果和高解析度streak camera的測量結果相比較，發現在電子束沒有明顯增加的時候，兩種方法測量結果差距在streak camera測量解析度範圍之內，因此確認此方法的可信度。至於在多電子束（multi-bunch）較複雜的運動情形，則留待後人討論對於理論模型的修正再行測量。

Synchrotron radiation became a very excellent light source for most of research areas nowadays. Thus, the stability of electron beam that emits synchrotron radiation while passing through the bending magnet is a very important issue. Since the bunch length of electron beam provides us the useful information for the tuning of the rf cavities, which have significant influence on the stability of electron beam, thus the main goal of this thesis is to provide a method for bunch length measurement. Our approach is to monitor the induced electron beam spectrum extracted by beam position monitor (BPM) at spectrum analyzer. By selecting a low-current bunch, which is assumed to have a gaussian profile with the theoretically predicted length (natural bunch length), as reference and measuring the ratio of spectrum-envelop between selected frequency and reference frequency, we can calculate the length of single bunch with progressively larger current. Since the measured results are fit with the results measured by streak camera within the systematic resolution. Thus, we can clam that the method of using the beam spectrum is valid at single bunch length measurement. However, the usage of this method for measuring bunch length at multiple-bunch situation, the longitudinal beam dynamics must be well studied and this will be left for further studies.

中文摘要………………………………………………………………………………5
英文摘要………………………………………………………………………………6
圖目錄…………………………………………………………………………………7
表目錄…………………………………………………………………………………9
第一章 簡介………………………………………………………………………..10
1.1 研究背景…………………………………………………….…………...10
1.2 研究方法…………………………………………………….…………...11
1.3 論文大綱…………………………………………………….…………...11
第二章 同步輻射簡介……………………………………………………………..12
2.1 同步輻射光簡介…………………………………………….…………...12
2.1.1 起源………………………………………………………………12
2.1.2 特性………………………………………………………………12
2.2 同步輻射研究中心(SRRC)簡介…...……………………….…………...15
第三章 電子束縱向動力學簡介……………………………………………..……..18
3.1 縱向聚焦(Longitudinal Focusing)….……………………….…………...18
3.2 同步振動(Synchrotron Oscillation)……………………………………...21
3.3 自然電子束長度(Natural Bunch Length)………………….………….…23
第四章 頻譜分析法………………………………………………………………..25
4.1 實驗原理…………………………………………………….…………...25
4.1.1 感應電流…………………………………………………………25
4.1.2 感應電流頻譜……………………………………………………26
4.2 實驗方法…………………………………………………….…………...32
4.3 實驗硬體設置……………………………………………….…………...35
4.3.1 系統架構…………………………………………………………35
4.3.2 重要儀器簡介……………………………………………………37
第五章 加速器實驗之測量結果與分析…………………………………………..39
5.1 加速器實驗測量結果……………………………………….…………...39
5.2 討論與分析………………………………………………….…………...43
5.3 結論………………………………………………………….…………...47
5.3.1 頻譜分析法之檢討………………………………………………47
5.3.2 未來展望…………………………………………………………47
參考文獻……………………………………………………………………………..49

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