BFEL自发辐射和受激辐射的光学诊断

OPTICAL DIAGNOSTICS FOR BF EL ExPERIMENTS

实验给出北京自由电子激光自发辐射与受激辐射实验的光学诊断结果，并简要介绍了ＢＦＥＬ红外谱仪系统的数据处理方式。利用光学诊断结果对电子束时间谱分析的新方法也进行了讨论，并对其可行性做了分析。

AbstractAn impo rtant aspect of testing the quality of e-beam,wiggler, optical resonator,beamtransport line, and the alignment system in FEL is the reliability to perform optical diagnosticsfor both spontaneous Emission and lasing spectrum. The BFEL IR-spectrometer system is de-signed for this purpose,and its features correspond to the parameters of BFEL accelerator,wiggler,etc..A set of focusing mirrors both before and after the slit of the monochrometer wasdeliberately arranged to allow both the total intensity measurement and the spectrum analysis tobe carried out simultaneously,shown in Fig.1.Because the hostility environments of the experimental area,all the optical diagnostical systemhave to be controlled remotely by a central nllcrocomputer,and thediagnostic process should be fin-ished in a possible short time. These are also required by the unperfectly quality and unstabilityofebeam at the very beginning of Spontaneous Emission experiments.With the data bank I(λ,t)～λ,t,besides the peak data spectrum,shown in Fig.2,the timecutting spectrum I,shown in Fig.3.,reflects the e-be.mquality in macropulse,andlasing starts 2μt after the e-beam set up.In regard to t=t_i, the spectrum I,and the relation of the peak wavelengthintensity I,to time, the e-beam stability in macropulse could be obtained,shown in Fig.4.It is a useful reference for e-beam optimizing.The time resolution energy spectrumy in macropulse is acquired throughdata bank, as in(1),shown in Fig.5.Its reliability depends on the exit trigger and the spec-trum scanning interval.The bandwidth of the Spontaneous Emission spectrum is caused by the homogeneous andinhomogeneous broadening,as in(4 )～(8),and has an effective influenee on the small signalgain G,as in(3).The adjustment of e-beam could obtain an optimized Spontaneous Emissionspectrum. The limiting bandwidth of FEL driven by RF LINAC is often referred to as theFourier-transform-of-electron-pulse limited,as in(9)and corresponds well with the experi-mental result.