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系統識別號 U0026-0812200914380364
論文名稱(中文) 太空電漿分析儀校準用之離子束系統
論文名稱(英文) Development of Ion Beam System for Calibration of Space Plasma Analyzers
校院名稱 成功大學
系所名稱(中) 物理學系碩博士班
系所名稱(英) Department of Physics
學年度 96
學期 2
出版年 97
研究生(中文) 彭康銘
研究生(英文) Kang-Ming Peng
電子信箱 albert_peng@pchome.com.tw
學號 l2695127
學位類別 碩士
語文別 英文
論文頁數 68頁
口試委員 口試委員-劉正彥
指導教授-陳秋榮
口試委員-河森榮一郎
中文關鍵字 粒子質量選擇器  電漿分析儀  法拉第杯陣列  離子束診測  離子源  離子束  校正 
英文關鍵字 Faraday Cup Array  ion beam diagnostic  Space Plasma Analyzers  Calibration system  Mass Analyzer  Ion Source  Ion Beam System 
學科別分類
中文摘要 成功大學電漿與太空科學中心太空儀器實驗室中的離子束系統是台灣第一座用於太空電漿分析儀器校正用之系統,系統中包含離子源、初級加速器、粒子質量選擇器、擴束器、加速器、飄移管、主腔體以及三軸旋轉台。此系統將提供5仟至13萬電子伏特的多種離子束以用於電漿粒子分析儀器之校正。此一離子束系統要求高度平行、均勻且具有良好的質量篩選。為了達到以上需求,已經完成以下工作:

1.設計離子源:
離子源以一個反射器及兩套電子槍組成,藉由電子撞擊中性氣體以產生離子。電子槍由一個電子發射燈絲,Wehnelt電極及屏極所組成。操控電極電壓可以調整電子束發散的角度。由電子軌跡以及離子自離子源擷取的數值模擬之中發現電子束發散的角度與離子束表現沒有相關性。所以,以自離子源擷取離子的均勻性與擷取效率作為考量的依據之後,對電子槍的結構最佳化作粒子軌跡的數值模擬。
2.設計正交的電場與磁場離子質量選擇器:
質量選擇器由一對90 度的圓柱型電極所組成,並對其施加互相垂直的電場與磁場。對不同的離子種類及能量施加最佳化選擇後的磁場及電場以取得所需的離子束質量選擇及通過效率。選擇以0.3 T的永久磁鐵篩選較重的粒子如:O+、N+,以0.05 T的磁鐵篩選較輕的粒子如:H+,He+。

3.建構離子束診測系統:
使用一維可移動的法拉第杯陣列取得離子束的二維的電流密度截面圖,用於回饋控制以及比較離子束與電漿粒子分析儀器量測的結果。此一法拉第杯陣列包含可達到2釐米空間解析度的64個法拉第杯。杯體使用不銹鋼材質以避免高能粒子與之反應,並且使用偏向電壓及高的深度與寬度比將離子撞擊產生的二次電子限制在杯中。

系統建構完成後開始之各項離子束的實驗,將能強化成功大學電漿與太空科學中心在台灣太空研究的能力。
英文摘要 An ion beam system for calibration of space plasma diagnostic instruments is being constructed for the first time in Taiwan. Beams of several ion species with energy range from 5 to 130 keV are provided by this system. The system consists of an ion source, a pre-accelerator, a mass analyzer, a beam expander, a main accelerator, a drift tube, a main chamber and a three-axis turntable.
To be highly parallel, uniformity and good mass resolution are required for the ion beam. In order to achieve this specification, the following studies have being done in this thesis:

1. Design of the ion source section:
The ion source section is composed of a repeller and 2 sets of electron guns. Ions are produced by electron bombardment on introduced neutral gas. The electron gun has a thermal electron emitter, a Wehnelt electrode and an anode. Adjusting voltage of the Wehnelt electrode can control spread angle of the electron beam emitted from the electron-gun. As a result of numerical calculation of trajectory of electrons and ions extracted from the ion source, I find no correlation between the electron beam profile and ion beam profile. Therefore, from point of view of extraction efficiency of ions from the ion source section, configuration of electron-gun is optimized using the numerical calculation of particle trajectory.

2. Design of ExB ion mass/energy selection section:
The mass analyzer is a pair of 90 degree cylindrical electrodes, to which a crossed electric field and magnetic field is applied. Optimum magnetic fields and electric fields applied to the electrodes for cases of several ion species were determined so that the mass resolution and transmission of ion beam flux have sufficient specification for our requirements. We chose a 3,000 Gauss permanent magnet for selecting heavier ions like O+ or N+, and 500 Gauss magnet for lighter ions such as H+ or He+.

3.Construction of ion beam diagnostic instruments:
To read current density profile for feedback control and compare the ion beam to the result from plasma particle analyzers, a movable 1-D Faraday Cup array is employed. The array is composed of 64 faraday cups with spatial resolution of 2 mm. The cups use stainless steel to avoid high energy ions to react with the material of cups. With help of negative bias voltage and high aspect ratio the faraday cups can trap the secondary electrons produced by ions bombard the wall inside the cups.

We will be able to start beam experiment in near future after assembling of the system finished. NCKU will strengthen ability of Taiwan’s space science research.
論文目次 摘要 III
Abstract V
誌謝 VII
Table of Contents VIII
List of Figures X
List of Tables XIV
Chapter 1 Introduction 1
1.1 Phenomena of space plasmas 1
1.2 Importance of particle analyzers calibration 5
1.3 Objective 6
Chapter 2 Calibration System 8
2.1 Ion source 9
2.2 Pre-accelerator 10
2.3 Mass analyzer 10
2.4 Beam expander 10
2.5 Main acceleration and drift tube 11
2.6 Ion beam diagnostics system 12
2.7 Main chamber and turntable 12
Chapter 3 Ion Source Design 13
3.1 Principle 13
3.2 Simulation Setup 18
3.3 Simulation Method 20
3.4 Result 21
3.5 Summary of Ion Source Design 34
Chapter 4 Ion Mass Selection 36
4.1 Principle 37
4.2 Configuration of mass analyzer 38
4.3 Simulation method 39
4.4 Simulation result of mass analyzer 41
4.5 Summary of ion mass selection 47
Chapter 5 Ion Acceleration 48
5.1 Ion Beam Expand 48
5.2 Ion Main Acceleration 50
Chapter 6 Development of Ion Beam Diagnostics System 52
6.1 principle of Faraday Cup 53
6.2 Design 56
6.2.1 Material 56
6.2.2 Bias voltage 57
6.2.3 Aspect ratio 59
6.2.4 Data Acquisition and Control System 60
6.2.5 Sensitivity 61
6.3 Summary of design of Faraday Cup Array 61
Chapter 7 Summary 63
Reference 66
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[2] Martin WÜEST, Time-of-Flight Ion Composition Measurement Technique for Space Plasmas, Measurement Techniques in Space Plasmas: Particles, American Geophysical Union, 1998

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[4] Margaret G. Kivelson and Christopher T. Russell, Introduction to space physics, CAMBRIDGE UNIVERSITY PRESS, 1995

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[12] H. C. Straub, P. Renault, B. G. Lindsay, K. A. Smith, and R. F. Stebbings, Absolute partial cross sections for electron-impact ionization of H2, N2, and O2 from threshold to 1000 eV, Phy. Rev. A vol 54, SEPTEMBER 1996

[13] G. K Parks, Physics of space plasmas: An Introduction, Addison-Wesley, Redwood City, 1991

[14] C. E. Sosolik, A. C. Lavery, E. B. Dahl, and B. H. Cooper, A technique for accurate measurements of ion beam current density using a Faraday cup, Rev. Sci. Instrum. vol 71, NUMBER 9 SEPTEMBER 2000

[15] Robert B. Darling, Adi A. Scheidemann, K. N. Bhat, and T.-C. Chen, Micromachined Faraday Cup Array Using Deep Reactive Ion Etching, Sensors and Actuators A, 2001

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[19] S. G. Walton, J. C. Tucek, and R. L. Champion, Yicheng Wang, Low energy, ion-induced electron and ion emission from stainless steel, JOURNAL OF APPLIED PHYSICS, vol 85, 1832 , 1 FEBRUARY 1999.
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