DESY, Hamburg
JINR, Dubna, Moscow Region
The driving engine of the Free Electron Laser in Hamburg (FLASH) is an L-band superconducting accelerator. It is designed to operate in a pulsed mode with 800 μs pulse duration and repetition rate of 10 Hz. Maximum accelerated current over macropulse is about 10 mA, and with the energy of electrons of 1 GeV average output power is about 72 kW. Expected power of the FEL radiation generated by FLASH is about 40 W. We show that FLASH technology holds great potential for increasing average power of the linear accelerator and increase of the transformation efficiency of the electron kinetic energy to the light. Thus, it will be possible to construct FLASH-like free electron laser operating at the wavelength of 13.5 nanometer with an average power in a kilowatt range. Such a source meets the requirements to the light source for the next generation lithography (NGL).
DESY, Hamburg
In this paper we exploit a formalism to describe Edge Radiation, which relies on Fourier Optics techniques, described in another contribution to this conference. First, we apply our method to develop an analytical model to describe Edge Radiation in the presence of a vacuum chamber. Such model is based on the solution of the field equation with a tensor Green's function technique. In particular, explicit calculations for a circular vacuum chamber are reported. Second, we consider the use of Edge Radiation as a tool for electron beam diagnostics. We discuss coherent Edge Radiation, extraction of Edge Radiation by a mirror, and other issues becoming important at high electron energy and long radiation wavelength. Based on this work we also study the impact of Edge Radiation on XFEL setups and we discuss recent results.
DESY, Hamburg
Electron bunch imagers based on incoherent OTR constitute the main device presently available for the characterization of ultrashort electron bunches in the transverse direction. One difficulty to obtain high-resolution images is related with the very peculiar particle-spread function of OTR radiation, which has a large width compared to the usual point-spread function of a point-like source. In this contribution we explore the possibility of using coherent OTR instead of incoherent OTR radiation, by integrating an ORS setup with a high-resolution coherent optical transition radiation imager. Electron bunches are modulated at optical wavelengths in the ORS setup. When these electron bunches pass through a metal foil target, coherent radiation pulses of tens MW power are generated. It is thereafter possible to exploit the large number of available coherent photons. In particular we manipulate the particle spread function of the system, so that the imaging problem can be reduced to the usual (coherent or incoherent) imaging theory for point-like radiators.
DESY, Hamburg
We describe a novel technique to characterize ultrashort electron bunches in X-ray Free-Electron Lasers. Namely, we propose to use coherent Optical Transition Radiation to measure three-dimensional (3D) electron density distributions. Our method relies on the combination of two known diagnostics setups, an Optical Replica Synthesizer (ORS) and an Optical Transition Radiation (OTR) imager. Electron bunches are modulated at optical wavelengths in the ORS setup. When these electron bunches pass through a metal foil target, coherent radiation pulses of tens MW power are generated. It is thereafter possible to exploit advantages of coherent imaging techniques, such as diffractive imaging, Fourier holography and their combinations. The proposed method opens up the possibility of real-time, wavelength-limited, single-shot 3D imaging of an ultrashort electron bunch.
DESY, Hamburg
We propose a new scheme for two-color operation of an FEL where an electron bunch generates an X-ray pulse and a long wavelength (VUV to infrared) radiation pulse. The scheme is very simple, cheap and robust, and therefore can be easily realized in facilities like FLASH, European XFEL, LCLS, and SCSS.
DESY, Hamburg
FEL process leads to energy loss by electrons and increase of the energy spread. Further use of the electron beam for generation of the FEL radiation is possible, but only for longer wavelength. This technical solution is implemented in the design of the European XFEL. Two undulators, SASE1 and SASE3 are installed in a raw. SASE 1 is designed to operate at fixed photon wavelength of 0.1 nm. The SASE 3 undulator has been placed behind SASE1, and will produce radiation in the wavelength range of 0.4 - 1.6 nm. Degradation of the electron beam quality after SASE1 is not completely negligible, and its influence on SASE3 performance is the subject of the present study.
DESY, Hamburg
This report deals with an update of parameters of a soft x-ray SASE FEL (SASE3) at the European XFEL. Two scenario of SASE3 operation are considered: nominal mode of operation (fixed energy of 17.5 GeV, and operating wavelength range 04 - 1.6 nm), and long wavelength mode of operation (fixed energy of 8.75 GeV, and operating wavelength range 1.6 - 6.4 nm). Perspectives for obtaining ultimate intensity of the radiation is discussed as well.
DESY, Hamburg
We formulate a complete theory of Edge Radiation based on a novel method relying on Fourier Optics techniques. Special attention is paid in discussing the validity of approximations upon which the theory is built. Our study makes consistent use of both similarity techniques and comparisons with numerical results from simulation. We discuss both near and far zone. Physical understanding of many asymptotes is discussed. As an example of application we discuss the case of Transition Undulator Radiation, which can be conveniently treated with our formalism. This work forms the theoretical basis for understanding the impact of Edge radiation on XFEL setups, which is discussed in another contribution to this conference.
FYSIKUM, AlbaNova, Stockholm University, Stockholm
Uppsala University, Uppsala
Uni HH, Hamburg
DELTA, Dortmund
DESY, Hamburg
Helmholtz-Zentrum Berlin für Materialien und Energie GmbH, Berlin
We present results from the new electron bunch diagnostic tool, Optical Replica Synthesizer [1] (ORS), installed at FLASH. The ORS produces an optical replica of the electron bunch profile, which is analyzed with a Grenouille, a device based on the Frequency Resolved Optical Gating (FROG) technique. This optical replica is generated by inducing a microbunching in the electron bunch and letting it pass through an undulator, called a radiator. The radiator emits coherently at the wavelength of microbunching, 772 nm. In order to create the microbunching a laser pulse is spatially and temporally overlapped with the electron bunch in another undulator, placed before the radiator. This introduces an electron energy modulation which is transformed into a density modulation in a chicane before the microbunched electron bunch is sent into the radiator. We observed an optical replica pulse of approximately 5 microJ corresponding to an electron bunch-spike of about 150 fs FWHM when the accelerators were set at optimal FEL conditions. We also showed that the ORS can run parasitically while maintaining SASE by steering the electron beam around the outcoupling mirror for the radiation.
[1] E. Saldin, E. Schneidmiller, M. Yurkov, “A simple method for the determination of the structure of ultrashort relativistic electron bunches,” Nucl. Inst. and Methods A 539 (2005) 499.