以密度斜坡達成在電漿波導式雷射電漿波電子加速器中注入電子之研究

在厘米等級的雷射電漿波電子加速器，已經被證實可以將電子加速至十億電子伏特，並且發散角小穩定性高的電子脈衝，這顯示了下個階段十兆電子伏特的對撞機與桌上型超快脈衝光源的波長範圍可從兆赫茲到伽瑪光有很大的潛力，這些需要高品質和高穩定的電子束，都在雷射驅動電漿波中巧妙的控制注入與加速過程所決定，在此我們證實經由在電漿波導管中注入橫向破碎波誘發密度下降斜坡，產生能量集中的電子束。在這計畫中電漿波導管是利用圓錐透鏡-前置短脈衝-加熱長脈衝所構成，再加上橫向的加熱長脈衝通過刀口在電漿波導管中產生縱向密度的變化，搭配干涉儀的觀察這個技術讓我們可以自由的控制位置、密度斜坡的斜率，發現產生高能量近似單能電子束只發生在當橫向加熱長脈衝製造下降斜坡時，而且密度斜坡在不同位置機率上也會改變，密度斜坡和高的主脈衝能量仍然維持存在的情況下成功將主脈衝灌入波導管中，產生的電子能量集中度小於一個百分比，可調整的密度斜坡讓我們清楚了解斜坡注入的過程和改善電子束品質，有了製作三維電漿密度結構、綜合電子的注入、加速器的技術，單一電漿波導管中產生X光自由電子雷射是可能被實現的。

關鍵字

密度斜波注入電子；雷射電漿波電子加速器；電子加速器

並列摘要

Laser wakefield electron accelerator has been demonstrated to have the capability of generating GeV-energy, low-emittance, high-stability electron pulses in centimeter scale length. It has shown great potential to become the key technology for next-generation TeV collider and various table-top ultrashort-pulse photon sources of wavelength ranging from THz to gamma-ray. These applications require an electron beam with high quality and stability, both of which are determined by finely controlled injection and acceleration processes in a laser-driven plasma wave. Here we report demonstration of production of a low-energy-spread electron beam via injection by longitudinal wave-breaking induced in a density down ramp in a plasma waveguide. In this scheme, the plasma waveguide is generated by using the axicon-ignitor-heater scheme, and an additional transverse heater pulse passing through a knife edge is used to produce longitudinal density variation in the plasma waveguide. This technique allows us to freely control the position and slope of the density ramp and to observe them with probing interferometry. It was observed that generation of a high-energy quasi-monoenergetic electron beam occurs only when the transverse heater pulse produces a density down ramp, and the probability of production varies with the position of density ramp. Good guiding of the pump laser pump was still maintained under the condition of presence of density ramps and high pump-pulse energy. The energy spread of the produced electron beam can be as low as 1%. The tunability of the density ramp allows us to clarify the ramp injection process and to optimize the quality of the electron beam. With this technique of fabrication of three-dimensional plasma density structure, integration of electron injector, accelerator, and x-ray free-electron laser in a single plasma waveguide may be achieved.

並列關鍵字

Plasma-waveguide ； Laser Wakefield Accelerator ； ramp injection

參考文獻

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[3] D. Strickland and G. Mourou “Compression of amplified chirped optical pulses. Opt. Commun.,56,219 (1985).

[4] E. Esarey, P.Sprangle, J.Kral, and A.Ting. “Overview of plasma-based accelerator concepts.” IEEE Trans. Plasma Sci., 24,252 (1993).

[5] K.Y. Kim,I. Alexeev, and H. M. Milchberg.”Single-shot super continuum spectral interferometry”. Appl. Phys. Lett 81, 4124 (2002).

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以密度斜坡達成在電漿波導式雷射電漿波電子加速器中注入電子之研究

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