CERN, Geneva
Ankara University, Faculty of Engineering, Tandogan, Ankara
PSI, Villigen
JAI, Oxford
INFN/LNF, Frascati (Roma)
In CLIC very tight tolerances exist for the phase and amplitude stability of the main and drive beam. In this paper we present the status of the CLIC beam phase and amplitude stabilisation concept. We specify the resulting tolerances for the beam and technical equipment and compare to first measurements.
SINAP, Shanghai
TUB, Beijing
A compact hard X-ray FEL facility is on plan now at Shanghai Institute of Applied Physics (SINAP). This facility will be located close to Shanghai Synchrotron Radiation Facility(SSRF) which is a 3rd generation light source in China, in order to control the overall length less than 650m, this facility asks a compact linac with high gradient accelerating structure. C-band (5712MHz) accelerating structure is a compromised and good option for this compact facility. R&D of a C-band (5712MHz) high gradient traveling-wave accelerating structure has been in progress at Shanghai Institute of Applied Physics (SINAP). The structure is consisted of 53 regular disk-loaded cells and two waveguide couplers, and its length is about one meter. This paper introduces the study of the accelerating structure design method, its experimental model and the preliminary results of the RF cold test of the model structure.
PSI, Villigen
SLAC, Menlo Park, California
Currently an X-band traveling wave accelerator structure is fabricated in a collaboration between CERN, PSI and Sincrotrone Trieste (ST). PSI and ST will use it in their respective FEL projects, CERN will test break down limits and rates for high gradients. A special feature of this structure are two integrated wake field monitors monitoring the beam to structure alignment. The design used an uncoupled model for the fundamental mode, assuming the overall behavior to be the superposition of the individual components. For the wake field monitors, an equivalent circuit was used. This approach has been proven to produce valid structure designs. None the less it cannot approach the quality of a numerical electromagnetic simulation of the full structure, which is ideal for a validation capturing the differences between design models and the real cavity as e.g. internal reflections inside the structure or higher order dispersive terms altering the response of the wake field monitor. Using SLAC's family of massive parallel codes ACE-3P, first results are presented for the fundamental mode and the first transverse mode. They are compared with earlier simulations using simplified models.
I-Tech, Solkan
Control of bunch arrival time, energy and trajectory of particle beams in linear accelerators is mandatory to reach performance goals and is carried out using different sub-systems. For optimal control and especially for accelerators aiming at the highest level of performance, for example FELs, these systems should be considered as a whole and work together. At Instrumentation Technologies such systems have been developed and tested on the field. Precise control of amplitude and phase of the accelerating felds is performed with the Libera LLRF, a digital RF stabilization system that is couple to Libera SYNC a very low jiiter master oscillator distribution system. The Libera Brilliance Single Pass system provides high resolution position information that allows accurate control of trajectories through critical machine sections such as bunch compression modules and FEL modulators and radiators. These systems are described in detail in the paper with examples from field measurements.
ELETTRA, Basovizza
This talk will report the present status of the worlwide FEL projects under construction including FELs at Fermi Elettra, SPRing8 and Frascati SPARC
PSI, Villigen
The X-ray FEL facilities in an advanced stage of planning worldwide can be grouped in two categories. Those with normal conducting driver linacs aiming to bring the XFEL technology, after the impressive feasibility prove at LCLS, to regional user communities at affordable cost, and those with superconducting driver linacs capable to serve several photon hungry users simultaneously. The talk will review the rationales, technical choices and status of the main proposals and discuss some key R&D issues.
Uni HH, Hamburg
DESY, Hamburg
PSI, Villigen
DELTA, Dortmund
The free-electron laser facility FLASH at DESY (Hamburg) was upgraded during a five-month shutdown in winter 2009. Part of this upgrade was the installation of a direct seeding experiment in the XUV spectral range. Beside all components for transport and diagnostics of the photon beam in and out of the accelerator environment, a new 10 m long variable-gap undulator was installed upstream of the existing FLASH undulator system. The seed pulses are generated within a noble-gas jet by focusing 40 fs long Ti:Sa laser pulses into it resulting a comb of higher harmonics. In the first phase of the experiment the 21st harmonic of the 800 nm drive laser will be used to seed the FEL process. The commissioning of the experiment has started in April and the first results are expected after the FLASH commissioning period mid of summer 2010. The experimental setup and the commissioning procedures as well as first result will be presented.
Fermilab, Batavia
DESY, Hamburg
A Third Hamonic/3.9 GHz superconducting RF module was recently installed in the FLASH facility at DESY. Ultra short bunches with high peak current are required to efficiently create high brilliance coherent light and these can be produced by means of a 2-stage transverse magnetic chicane bunch compression scheme coupled with off-crest acceleration. The long bunch tails and reduced peak current which result from the nonlinearities of the RF since wave can be eliminated by the addition of a 3rd harmonic RF system. Such a system can also allow for the creation of uniform intensity bunches of adjustable length necessary for seeded operation. We present here a summary of commissioning and early operating experience of the newly-installed device.
SLAC, Menlo Park, California
With the growing demand for FEL light sources, cost issues are being revaluated. To make the machines more compact, higher-frequency room-temperature linacs are being considered, in particular, ones using C-band (5.7 GHz) rf technology where 40 MV/m gradients are possible. In this paper, we show that an X-band (11.4 GHz) linac using the technology developed for NLC/GLC can provide an even lower cost solution. In particular, stable operation is possible at gradients of 100 MV/m for single bunch operation, and 70 MV/m for multibunch operation. The concern of course is whether the stronger wakefields will lead to unacceptable emittance dilution. However, we show that the small emittances produced in a 250 MeV, low bunch charge, LCLS-like S-band injector and bunch compressor can be preserved in a multi-GeV X-band linac with reasonable alignment tolerances.
ELETTRA, Basovizza
FERMI@Elettra is a soft X-ray, fourth generation light source facility in the last phase of its construction stage at the Elettra Laboratory in Trieste, Italy. It will be based on a seeded FEL, driven by the existing normal conducting linac that is presently expected to operate at 1.5 GeV. Two differet FEL lines will produce very short coherent photon pulses (25-200 fs) in the UV snd soft X-ray region (100-4 nm). FEL1 will cover 100-20 nm, FEL2 20-4 nm. Here a possibility to extend the FERMI spectral range capability down to the water window (1.0-2.0 nm) is presented. The suggested upgrading foresees the increase of the linac energy up to 2.4-2.5 GeV, leaving untouched the existing undulator chains and the overall length of the accelerator.
DESY, Hamburg
The European XFEL is a 4th generation synchrotron radiation source, under construction in Hamburg. Based on different Free-Electron-Laser and spontaneous sources, driven by a 17.5 GeV superconducting accelerator, this international facility will provide several user stations with photons simultaneously. Due to superconducting technology high average as well as peak brilliance can be delivered. Flexible bunch pattern are possible for optimum tuning to the experiments demands. This paper will present the current status of the electron beam diagnostics. An overview of the entire system will be given, as well as details on the development of the main systems like BPM, charge and transmission diagnostics, beam size and beam loss monitor systems will be presented. Furthermore, results of first measurements with XFEL prototypes in FLASH will be shown.
SLAC, Menlo Park, California
LLNL, Livermore, California
ANL, Argonne
The LCLS FEL began user operations in September 2009, with photon energies from 800eV to 2 KeV and pulse energies above 2 mJ. Both long pulse (50-200 femtosecond FWHM) and short pulse (<10 femtosecond FWHM at 150 uJ) pulses were delivered at user request. In addition the FEL was operated at fundamental photon energies up to 10 KeV in preparation for hard X-ray experiments. FEL operating parameters, performance and reliability results will be presented, in addition to plans for upgrades to the facility.
UMAN, Manchester
DESY, Hamburg
Rostock University, Faculty of Computer Science and Electrical Engineering, Rostock
Third harmonic superconducting cavities have been designed and fabricated by FNAL to minimise the energy spread along bunches in the FLASH facility at DESY. A module, consisting of four nine-cell 3.9 GHz cavities, has been installed in FLASH. The first measurement with beam excitation is presented, and the comparisons to transmission measurement without beam and simulations are made. Higher order modes (HOMs) are able to propagate to adjacent cavities through attached beam tubes. Modes from 1.3 GHz cavities in the module nearby also propagate into this module.
*Work supported by European Commission under the FP7 Research Infrastructures grant agreement No.227579.
ISIR, Osaka
Tohoku University, Research Center for Electron Photon Science, Sendai
We are conducting FEL experiments with the L band electron linac at Osaka University. The linac is equipped with a thermionic electron gun and the three-stage sub-harmonic buncher(SHB) system. In FEL experiments an 8μs long electron pulse is injected from the gun and the SHB system is turned on for generating a multi-bunch electron beam of an 8μs duration with 2nC charge per bunch and 9.2 ns intervals between bunches. It repeatedly amplifies light pulses stored in the optical resonator of the FEL. The roundtrip time of the light pulses is 37 ns, so that four light pulses are stored in the resonator. The FEL gain becomes higher at least in proportion to the peak current in the bunch or charge per bunch. The present charge value is limited by the high beam loading in the acceleration tube of the linac, exceeding a half of the input RF power. If the bunch intervals can be extended to 37 ns, the charge per punch can be made four times higher for the same beam loading, resulting in significant increase of the FEL gain. To generate such an electron beam, we are developing the electron gun system with a high-repetition-rate grid-pulser. We will report the outline of the study.