SLAC, Menlo Park, California
It is well known that harmonic generation in HGHG amplifies the shot noise in the beam. In this work, we introduce a framework for theoretical description of the noise dynamics in such a device consisting from un undulator-modulator and a chicane. We propose to consider the interaction of particles in the modulator-undulator through the radiation field as a source which modifies the noise level in the beam. The coherent part of this interaction is responsible for the FEL process while the random part introduces correlations in the particle's positions and modifies the noise properties of the beam. We develop a 1D version of the method and apply it to the HGHG seeding mechanism.
SLAC, Menlo Park, California
It is generally accepted that harmonic-generation seeding in FELs amplifies the noise in the beam and enhances the spontaneous component of the FEL radiation. In this paper we analyze the noise dynamics caused by particle interaction in the undulators of the EEHG seeding mechanism. We develop a 1D model of the noise evolution through the system and calculate the amplification factor as a function of frequency. Our results are applied to a typical soft x-ray EEHG FEL.
SLAC, Menlo Park, California
The success of LCLS has opened up a new era of x-ray sciences. An upgrade to LCLS is currently being planned to enhance its capabilities. In this paper we study the feasibility of using the echo-enabled harmonic generation (EEHG) technique to generate narrow bandwidth soft x-ray radiation in the proposed LCLS-II soft x-ray beam line. We focus on the conceptual design, the technical implementation and the expected performances of the echo-seeding scheme. We will also show how the echo-seeding scheme allows one to generate two color x-ray pulses with the higher energy photons leading the lower energy ones as is favored by the x-ray pump-probe experiments.
SLAC, Menlo Park, California
EPFL, Lausanne
ECHO-7 is a proof-of-principle echo-enabled harmonic generation FEL experiment in the Next Linear Collider Test Accelerator (NLCTA) at SLAC. The experiment aims to generate coherent radiation at 318 nm and 227 nm, which are the 5th and 7th harmonic of the infrared seed laser. In this paper we present the experimental results from the commissioning run of the completed experimental setup which started in April 2010.
