合肥储存环相干谐波自由电子激光研究方法的改进

 根据简单的计算模型,导出辐射能量谱形状因子和相干谐波辐射表达式,用此表达式讨论了不对称光学速调管的相干谐波辐射;对于合肥储存环相干谐波自由电子激光,提出了一个不对称光学速调管相干谐波辐射的研究方案,并且作了详细的计算,结果表明在较高的电子束能量下,调整光学速调管和外激光参数,使辐射段波荡器的辐射基波与外激光的二次谐波共振,进行相干谐波产生实验,能获得10⁹量级相干加强因子。     

相干谐波辐射的测量方法和系统

 研究了光学速调管自发辐射谱,其调制率已达0.80,即将进行相干谐波辐射实验。介绍了相干谐波辐射实验的主要考虑因素、相干增强因子的测量方法和测量系统以及种子激光与电子束的准直和同步。     

双光束相干控制产生多次谐波的实验验证

利用两束相干度可改变的飞秒脉冲光对产生的五次谐波的强度特性进行了研究，发现谐波信号的强度随相干程度的增大而增加，谐波信号的最大值相对于相干零点(双光束相干度最大处)是非对称的，从而证明了合成的激光脉冲波形变化对谐波信号的影响.同时对谐波的受激放大理论进行了初步的实验探索和展望. 关键词： 五次谐波 波形变化 相干 受激放大     

用非对称光学速调管的相干谐波自由电子激光

使光学速调管第二段波动器的磁场参数与光场的高次谐波共振，与对称光学速调管情况相比，可使产生的相干谐波辐射强度提高。对三次谐波，强度提高为对称情况的２．６倍。     

光学相干层析系统相干传递函数研究

在弱物体近似下从成像系统角度对光学相干层析测量技术进行了理论研究。分析了该技术测量样品纵深结构时图像的形成机理。结果表明它相当于一复振幅线性平移不变系统，从而可用相干传递函数描述系统性能，所得相干传递函数表明系统具有低通特性，半峰值带宽△ｋ＝２△λ／λ＾２。由于物体频谱整体平移了１／λ，测量的是纵向结构的高频信息。本文的工作为定量分析光学相干层析对未知结构的测量结果及进一步提高空间分辨率提供了理论     

光学速调管相干辐射的数值模拟

 利用实测磁场值对光学速调管的相干辐射进行了数值模拟，计算了基波、三次谐波的谱宽和相干增强因子，提出了优化的激光功率和光学速调管特征参数Nd值。     

FEL光学速调管的升级性能分析

通过三维磁场的有限元计算，给出了自由电子激光（FEL）研究用光学速调管升级后的磁参数。国家同步辐射实验室合肥光源（HLS）电子储存环能量可以日常运行在200～800 MeV间，为了与电子储存环能量匹配，并在较高束电子能量下进行实验和得到较多的相干辐射光子，光学速调管从原来的对称结构升级成非对称结构，用于HLS储存环谐波产生FEL实验。给出了升级后非对称光学速调管的几组匹配磁参数，用于在HLS储存环注入能量和可以运行的最高能量下进行谐波FEL实验。初步计算表明，HLS 储存环电子束性能优越，能散很低，FEL实验用最高能散仅为2.05×10-4，相应FEL辐射的能散修正因子在0.96以上，可以忽略不计。     

任意偏振双色相干场高次谐波

系统地研究了任意偏振双色相干场高次谐波，结果表明单个圆偏振光不能产生高次谐波，在适当的条件下，某些谐波可以部分或完全消失，而某些谐波可以得到加强，产生更高次谐波高转换效率的条件是双色线偏振场的结合。     

相干谐波储存环自由电子激光

相干谐波自由电子激光不用光学谐振腔及反射镜,可望工作在紫外和真空紫外光波段,是第四代同步辐射光源的可能途径之一。由于对束流品质要求很高,相干谐波自由电子激光首先是以储存环作为驱动器而发展起来的。由于光阴极微波电子枪的发展和直线加速器技术的进步,目前,已开始有直线加速器驱动的高增益相干谐波自由电子激光的建议。文章介绍了相干谐波储存环自由电子激光的原理、现状及展望。     

加深光学速调管自发辐射谱调制的研究

相干谐波储存环自由电子激光的相干增强因子正比于光学速调管自发辐射谱调制率的平方,加深光学速调管自发辐射谱的调制是相干谐波储存环自由电子激光研究的重要一环.介绍在中国科学技术大学800MeV电子储存环上所进行的加深光学速调管自发辐射谱调制的研究工作,调制率已从0.236提高到了0.80,为相干谐波产生实验奠定了基础.     

Harmonic operation of high gain harmonic generation free electron laser

In high gain harmonic generation (HGHG) free electron laser (FEL), with the right choice of parameters of the modulator undulator, the dispersive section and the seed laser, one may make the spatial bunching of the electron beam density distribution correspond to one of the harmonic frequencies of the radiator radiation, instead of the fundamental frequency of the radiator radiation in conventional HGHG, thus the radiator undulator is in harmonic operation (HO) mode. In this paper, we investigate HO of HGHG FEL. Theoretical analyses with universal method are derived and numerical simulations in ultraviolet and deep ultraviolet spectral regions are given. It shows that the power of the 3rd harmonic radiation in the HO of HGHG may be as high as 18.5% of the fundamental power level. Thus HO of HGHG FEL may obtain short wavelength by using lower beam energy.     

CHG-SRFEL光学速调管磁极间隙全闭环控制系统

 描述了CHG-SRFEL光学速调管磁极间隙全闭环控制系统的原理，给出了系统硬件结构和软件设计。可独立或同步调节光学速调管调制段、色散段及辐射段磁极间隙的大小，分辨率达到20μm，精度达到5μm。通过改进系统位置监测设备，可进一步提高分辨率及精度。系统已经在光学速调管磁场测量、垫补中使用，具有精度高、安全性高、操作方便等特点。     

Harmonic operation of high gain harmonic generation free electron laser

In high gain harmonic generation (HGHG) free electron laser (FEL), with the right choice of parameters of the modulator undulator, the dispersive section and the seed laser, one may make the spatial bunching of the electron beam density distribution correspond to one of the harmonic frequencies of the radiator radiation, instead of the fundamental frequency of the radiator radiation in conventional HGHG, thus the radiator undulator is in harmonic operation (HO) mode. In this paper, we investigate HO of HGHG FEL.Theoretical analyses with universal method are derived and numerical simulations in ultraviolet and deep ultraviolet spectral regions are given. It shows that the power of the 3rd harmonic radiation in the HO of HGHG may be as high as 18.5% of the fundamental power level. Thus HO of HGHG FEL may obtain short wavelength by using lower beam energy.     

Proposal for an x-ray free electron laser oscillator with intermediate energy electron beam

Harmonic lasing of low-gain free electron laser oscillators has been experimentally demonstrated in the terahertz and infrared regions. Recently, the low-gain oscillator has been reconsidered as a promising candidate for hard x-ray free electron lasers, through the use of high reflectivity, high-resolution x-ray crystals. In this Letter, it is proposed to utilize a crystal-based cavity resonant at a higher harmonic of the undulator radiation, together with phase shifting, to enable harmonic lasing of the x-ray free electron laser oscillator, and hence allow the generation of hard x-ray radiation at a reduced electron beam energy. Results show that fully coherent free electron laser radiation with megawatt peak power, in the spectral region of 10-25 keV, can be generated with a 3.5 GeV electron beam.     

Spectral modulation of higher harmonic spontaneous emission from an optical klystron

Higher harmonics of spontaneous emission from an optical klystron have been observed. The modulation factor of the spontaneous emission spectrum for the higher harmonics can be described by considering the observation system. When the dispersive gap of the optical klystron was fixed, the microstructure interval of the spontaneous emission spectrum at a certain resonant wavelength became narrower as the order of the higher harmonic became larger. Some unique characteristics of the higher harmonics have been clarified, and these studies are likely to contribute to the development of free‐electron lasers using higher harmonics of an optical klystron in the shorter‐wavelengths region.     

A proposed method to characterize high harmonic microbunching in EEHG operation of SDUV-FEL

The echo-enabled harmonic generation(EEHG)scheme offers remarkable efficiency for generatinghigh harmonic microbunching with a relatively small energy modulation.A proof of principle experiment of the EEHG scheme has been proposed at the Shanghai deep ultraviolet(SDUV)free electron laser(FEL)facility,where the 4th harmonic of the seed laser is amplified in the 9 m long radiator.To explore the advantages of the EEHG scheme,in this paper,a method of measuring the coherent high harmonic radiation of the radiator is proposed to investigate the electron beam microbunching corresponding to the 10th-20th harmonics of the seed laser.The principle of the proposed method,comparisons with existing methods and the simulation results are presented and discussed.     

增强谐波辐射的一种新途径

提出用ＭＯＰＡ构型来增强谐波辐射。通过这个构型，人们可以用低能量电子束获得多种短波长和高功率相干光源。