Nonthermal electron acceleration with 100 TW laser at National Central University

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研究生：	陳嘉衡 Chia-Heng Chen
論文名稱：	Nonthermal electron acceleration with 100 TW laser at National Central University 使用中央大學100兆瓦雷射進行非熱效應電子加速實驗
指導教授：	藏滿康浩 Yasuhiro Kuramitsu
口試委員:
學位類別：	碩士 Master
系所名稱：	理學院 - 物理學系 Department of Physics
論文出版年：	2015
畢業學年度：	103
語文別：	中文
論文頁數：	52
中文關鍵詞：	宇宙射線、尾波場加速、實驗室天文學
外文關鍵詞：	cosmic ray, wakefield acceleration, laboratory astrophysics
相關次數：	點閱：6 下載：0
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查詢本校圖書館目錄查詢臺灣博碩士論文知識加值系統勘誤回報

自宇宙射線被發現一個世紀以來，宇宙射線的來源就一直是一個未解的問題。對數座標下宇宙射線的能譜是$\gamma^{-2}$ 的冪次關係，並非在馬克士威- 波茲曼分佈。這說明並非熱碰撞造成宇宙射線加速。半世紀以來，物理學家提出了許多理論解釋宇宙射線加速機制，從Fermi acceleration、diffusive shock acceleration 到尾波場加速。

高功率雷射的發展，開啟了實驗室天文學。許多的物理參數難以透過地球上的觀測獲取，而利用高功率雷射可以在實驗室模擬天文學現象，量測天文觀測難以獲得的參數與觀察天文現象的演化過程。雷射電漿加速器也應用到尾波場，用以模擬宇宙射線尾波場加速機制。

我們建立了一個實驗平台去研究天文物理現象。從光學路徑的設計、光學元件的採購、電路架設、氣體管路架設、真空架設、輻射屏蔽，最後順利加速電子。電子能譜也觀測到非馬克士威- 波茲曼分佈。我們改良能譜儀的設計，準備進一步得到γ􀀀2 的電子能譜分佈。

Cosmic rays have been discovered over a century ago ; the origins of cosmic
rays are an unsolved problem. Cosmic ray spectrum is well represented by the power
law γ􀀀2, instead of Maxwell-Boltzmann distribution. Last 50 years, there have been
many different theories trying to explain mechanism of cosmic ray, such as Fermi
acceleration, diffusive shock acceleration and wakefield acceleration.
Development of high power laser enable us to start laboratory astrophysics.
Many key physical quantities are hard to directly measure in the universe. Now
we can simulate space/astrophysical phenomena in laboratories by measuring those
physical parameters. We have built experimental platform to research space/astrophysical
phenomena. As the first step, we perform model experiment of cosmic ray
acceleration due to wakefield excited by an intense laser. We observe non-Maxwell-
Boltzmann distribution of electron spectra. We also discuss improvement of the future
experiment in order to obtain γ􀀀2 electron spectrum.

Introduction 1
1 Cosmic rays . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1
2 Acceleration of cosmic rays . . . . . . . . . . . . . . . . . . . . . . . . 4
2.1 Fermi acceleration and Diffusive shock acceleration . . . . . . 4
2.2 Wakefield acceleration . . . . . . . . . . . . . . . . . . . . . . 4
3 Laboratory astrophysics . . . . . . . . . . . . . . . . . . . . . . . . . 7
Experimental method 9
1 100 TW and 20 TW laser facility . . . . . . . . . . . . . . . . . . . . 9
2 Setup and diagnostic system . . . . . . . . . . . . . . . . . . . . . . . 13
2.1 Off-axis parabolic mirror . . . . . . . . . . . . . . . . . . . . . 13
2.2 Mach-Zehnder interferometer . . . . . . . . . . . . . . . . . . 16
2.3 Relayed-imaging system . . . . . . . . . . . . . . . . . . . . . 19
2.4 Electron spectrometer . . . . . . . . . . . . . . . . . . . . . . 20
3 Radiation Shielding . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22
3.1 Mechanism of interaction between ionizing radiation and substances
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22
3.2 Design of ionizing radiation protection . . . . . . . . . . . . . 26
3.3 Fluka simulation results . . . . . . . . . . . . . . . . . . . . . 27
Result and data analyses 32
1 Laser conditions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 32
2 Electron spectrometer(ESM) . . . . . . . . . . . . . . . . . . . . . . . 32
2.1 Zero displacement . . . . . . . . . . . . . . . . . . . . . . . . 32
2.2 Calculation method of electron spectra . . . . . . . . . . . . . 34
2.3 Results of electron spectra . . . . . . . . . . . . . . . . . . . . 36
Disucussion 43
1 Peak energies of electron spectra . . . . . . . . . . . . . . . . . . . . 43
2 Improvements of experimental design . . . . . . . . . . . . . . . . . . 43
2.1 High dynamics range electron spectrometer (ESM) . . . . . . 44
2.2 Energy output of laser . . . . . . . . . . . . . . . . . . . . . . 44
2.3 Profile of amplified main pulse . . . . . . . . . . . . . . . . . 47
2.4 Plasma density . . . . . . . . . . . . . . . . . . . . . . . . . . 49
Summary 50
Bibliography 52
A Program to define zero displacement 55
B Program for electron spectra 57
                                

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