LBNL, Berkeley, California
UCB, Berkeley, California
ANL, Argonne
A concept for a tunable soft x-ray free electron laser (FEL) oscillator is proposed and studied numerically. It is based on the idea of echo enabled harmonic generation [1] and takes advantage of the oscillator’s ability to start up from spontaneous emission, thereby eliminating the need for optical lasers. In the proposed concept, harmonic tunability is accomplished through beam manipulations using magnetic chicanes and a tunable radiator while two FEL oscillators remain at a fixed frequency. An additional advantage of the proposed technique is the possibility to utilize multilayer x-ray mirrors with a high backward reflectivity of the order of 70%, allowing the initial beam manipulation to be accomplished at a short wavelength, close to the final soft x-ray output. The high repetition rate soft x-ray output is expected to have longitudinal coherence and a narrow bandwidth.
[1] G. Stupakov, PRL, 2009
ANL, Argonne
X-ray free electron lasers (FELs) are well suited to pursue a long-standing goal of studying matter in a transient state that is far from equilibrium. This state often determines the functions of materials and, thus, holds a key to understanding how to control them. The natural time scale for most of the dynamic processes involving atoms is of the order of 100 femtoseconds, and existing x-ray FELs have already surpassed this mark. The natural time scale for dynamic processes driven by electrons is of the order of 100 attoseconds, and this is the next Rubicon for FELs. In this talk I will review the state of the art in generation of femtosecond x-ray pulses using FELs and will discuss a number of new ideas en route to sub-femtosecond x-ray pulses.
LBNL, Berkeley, California
UCB, Berkeley, California
ANL, Argonne
The Next Generation Light Source (NGLS) is a design concept, under development at LBNL, for a 10‐beamline soft x‐ray FEL array powered by a 2.4 GeV superconducting linear accelerator, operating with a 1 MHz bunch repetition rate. The CW superconducting linear accelerator is supplied by a high-brightness, high-repetition-rate photocathode electron gun. Beam is distributed from the linac to the array of independently configurable FEL beamlines with nominal bunch rates up to 100 kHz, with even pulse spacing. Individual FELs may be configured for EEHG, HGHG, SASE, or oscillator mode of operation, and will produce high peak and average brightness x-rays with a flexible pulse format ranging from sub-femtoseconds to hundreds of femtoseconds.
ELETTRA, Basovizza
University of Nova Gorica, Nova Gorica
LBNL, Berkeley, California
Two machine configurations of the electron beam dynamics in the FERMI@elettra linac have been investigated, namely the one-stage and the two-stage electron bunch compression. One of the merits of the one-stage compression is that of minimizing the impact of the microbunching instability on the slice energy spread and peak current fluctuations at the end of the linac. Special attention is given to the manipulation of the longitudinal phase space, which is strongly influenced by the linac structural wake fields. The electron bunch with a ramping peak current is used in order to obtain, at the end of the linac, an electron bunch characterized by a flat peak current profile and a flat energy distribution. Effects of various jitters on electron bunch energy, arrival time and peak current are compared and relevant tolerances are obtained.