BUNCH DIAGNOSTICS WITH COHERENT INFRARED UNDULATOR RADIATION AT FLASH

The Free-Electron-Laser in Hamburg (FLASH) at DESY has been complemented by an electromagnetic infrared undulator as a new tool for analysing the longitudinal profile of the short electron bunches characteristic for FLASH using coherent diagnostic techniques. This undulator has a maximum K-Value of 44 corresponding to a maximum wavelength of 200µm at an electron energy of 500 MeV. For the characterization of the emitted radiation and for the analysis of correlations between machine or undulator parameters and undulator spectra, an experimental set-up has been developed and installed in the FLASH Experimental Hall containing a dispersive spectrometer as a main instru-ment. The spectrometer is designed for THz spectra using reflective blazed gratings as dispersive elements and a pyroelectric detector. The final goal is the reconstruction of the longitudinal bunch shape by tuning the undulator through the wavelength range of the electromagnetic device and measuring the intensity of the infrared radiation.