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Coherence Properties of Individual Femtosecond Pulses of an X-Ray Free-Electron Laser

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Coherence Properties of Individual Femtosecond Pulses of an X-Ray Free-Electron Laser

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  1. I. A. Vartanyants,1,2,* A. Singer,1 A. P. Mancuso,1,† O. M. Yefanov,1 A. Sakdinawat,3 Y. Liu,3 E. Bang,3 G. J. Williams,4G. Cadenazzi,5 B. Abbey,5 H. Sinn,6 D. Attwood,3 K. A. Nugent,5 E. Weckert,1 T. Wang,4 D. Zhu,4 B. Wu,4 C. Graves,4A. Scherz,4 J. J. Turner,4 W. F. Schlotter,4 M. Messerschmidt,4 J. Lu¨ning,7 Y. Acremann,8 P. Heimann,9 D. C. Mancini,10V. Joshi,10 J. Krzywinski,4 R. Soufli,11 M. Fernandez-Perea,11 S. Hau-Riege,11 A. G. Peele,12 Y. Feng,4 O. Krupin,4,6S. Moeller,4 and W. Wurth13 報告者:賴柏丞 指導老師:梁君致老師 Coherence Properties of Individual Femtosecond Pulses of an X-Ray Free-Electron Laser

  2. 1.自由電子雷射介紹 2.簡介 3.儀器架設 4.實驗內容(實驗數據) 5.結論 大綱

  3. 自由電子雷射所產生雷射束的光學性質與傳統 雷射器一樣,具有高度相干、高能量的特點, 其不同點在於其特殊的光源產生機制。 自由電子雷射(FSR)

  4. 高能階E2上的電子,在頻率為ν的輻射場作用下,高能階E2上的電子,在頻率為ν的輻射場作用下, 躍遷至低能階E1並輻射一個能量為光子

  5. 加速電子 ↓ 波盪器(undulator) ↓ 放出photon

  6. 波盪器(Undulator):兩排南北極相間的永久磁 鐵形成的磁場呈現週期性的變換方向,當電子 通過這一系列的週期性磁場,它的軌跡在垂直 於磁場的平面上會有著相同週期性的擺動。

  7. 根據電磁學的理論:當電子以接近光的速度飛 行時,若受到磁場的作用而發生偏轉,則因相對論效 應沿著偏轉的切線方向,放射出薄片狀、極強的電磁 波,這就是同步輻射光。

  8. LCLS

  9. 簡介

  10. 相干性:為了產生顯著的干涉現象,波所需具 備的性質 波與波之間的的相干性可以用相干度(degree of coherence)來衡量

  11. 實驗裝置 780 eV(λ =1.6nm) horizontal 5.7 ± 0.4 μ m(FWHM) vertical 17.3 ± 2.4 μ m(FWHM) Pinhole separations 2~15 μ m

  12. Kirkpatrick-Baez mirrors 可彎曲 垂直焦距 =1.5m,水平焦距 =2m

  13. 單色儀 → 從出射狹縫出來的光為單色光

  14. 實驗內容

  15. 複相干度 0 < <1

  16. 11 μ m

  17. Temporal coherence

  18. 交叉譜密度(CSD)

  19. 78 ±8%→TEM00 mode

  20. 測量完LCLS所產生x ray雷射所得到的結果為 在780 eV光子能量下 1.橫向相干度= 56 % 2. 78% total power → TEM00 mode 3.時間相干性 = 0.55 fs 總結

  21. http://zh.wikipedia.org/wiki/%E7%9B%B8%E5%B9%B2%E6%80%A7 http://www.phys.ncku.edu.tw/optics/book_2/b2_11_2002_incomplete.pdf http://en.wikipedia.org/wiki/Spectral_density#Cross-spectral_density http://www.nwsni.edu.cn/jcb/wulishiyanzhongxin/page/xiazai/jiaochen/pdf/gzdsy.pdf 參考資料

  22. THE END

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