ANL, Argonne
We review the development of pulse shaping techniques for high brightness beam generation. A scheme of generating a uniform ellipsoidal laser pulse for s is discussed. The scheme is based on the chromatic aberration of a dispersive lens. Fourier optics simulation reveals the interplay of group velocity delay and dispersion in the scheme, as well as diffractions. Particle tracking simulation shows that the beam generated by such a laser pulse approaches the performance of that by an ideal ellipsoidal laser pulse and represents a significant improvement from the traditionally proposed cylindrical beam geometry. The scheme is tested in an 800-nm, optical proof-of-principle experiment at lower peak power with excellent agreement between the measurement and simulation.
DESY, Hamburg
Superconducting drive linacs for FEL facilities offer long rf-pulses which can accelerate thousands of electron bunches. Individual bunches are distributed to several beam lines for quasi-simultaneous operation of different user stations. We will present various schemes that fulfill this task and take the fast beam distribution of the European XFEL as an example for design choices. The main challenge is the preservation of the excellent electron beam quality, transversely and longitudinally, which leads to demanding hardware requirements to ensure beam stability and advanced electron optics to prevent emittance degradation due to self-fields.
RIKEN/SPring-8, Hyogo
JASRI/SPring-8, Hyogo-ken
An 8-GeV C-band (5712 MHz) accelerator is employed as a main accelerator for XFEL/SPring-8. Since a C-band accelerating structure generates a high accelerating gradient of higher than 35 MV/m, the total length of the accelerator fits within 400 m, including the injector and three bunch compressors. We use 64 C-band rf units, which consist of 128 accelerating structures, 64 rf pulse compressors and waveguide components, 64 klystrons and modulators, etc. Mass-production of the C-band rf components has been done by several Japanese manufacturers. The components reliability has been improved during the production, and all the components finally have excellent quality. The production quality was also confirmed by a high power rf test. We achieved the accelerating gradient of 40 MV/m without any problem. Since XFEL realizes high bunch compression with precise control of the energy chirp, the rf should be quite stable. We developed a high precision high voltage charger combined with a low-noise klystron modulator. The pulse-to-pulse stability of the PFN voltage was less than 0.01%. Installation of the components started in August 2009 and was now almost completed on schedule.
DESY Zeuthen, Zeuthen
DESY, Hamburg
UCLA, Los Angeles, California
HZB, Berlin
The major objectives of the Photo-Injector Test Facility at DESY in Zeuthen, PITZ, are research and development of high brightness electron sources suitable to drive FELs like FLASH and the European XFEL. In the 2008/2009 run period the facility has been operated with a new photo-cathode laser system and a dry-ice cleaned RF gun cavity. Characterization of the transverse phase space of the electron source has been performed in details using a single slit scan technique with a dedicated Emittance Measurement System. In preparation for the forthcoming run, a number of quadrupole magnets have been installed and tomography reconstruction with data from quadrupole scans with two magnets has been carried out in semi-parallel manner to the slit scans. This contribution summarizes the experience from the phase-space tomography reconstruction with nominal beam conditions. Advantages and drawbacks of the measurement procedure and the analysis are superimposed and results are compared to ones obtained with the slit scans.