JAI, Egham, Surrey
DESY, Hamburg
The PETRA-III Laser-wire, a Compton scattering beam size measurement system at DESY, uses an automated mirror to scan a Q-switched laser across the electron beam and is developed from the system previously operated at PETRA-II. This paper reports on recent upgrades of the optics, vacuum vessel and data acquisition. First beam profile measurements are also presented.
DESY, Hamburg
Uni HH, Hamburg
The free-electron laser user facility FLASH at DESY, Germany has been upgraded. The upgrade started in autumn 2009 after almost 2 years of a very successful second user period. The beam energy is increased to 1.2 GeV by installing a 7th superconducting accelerating module. The new module is a prototype for the European XFEL. Among many other upgrades, 3rd harmonic superconducting RF cavities are installed in the injector. The main purpose is to flatten and - to a certain extend - to shape the longitudinal electron beam phase space improving the dynamics behavior of the beam. The seeding experiment sFLASH is being commissioned, an important step forward to establish seeded FEL radiation for user experiments. After the ongoing commissioning, the 3rd user period will start this summer. In many aspects FLASH will be an FEL with a new quality of performance: a wavelength approaching the carbon edge and the water window, tunable pulse width, and with thousands of pulses per second. This report summarizes the recently finished upgrade of FLASH and reports on the results of the ongoing commissioning and the expected performance as a free electron laser user facility.
DESY, Hamburg
The free-electron laser facility FLASH at DESY, Germany finished its second user period scheduled from November 2007 to August 2009. More than 300 days have been devoted for user operation, a large part of beamtime has been allocated for machine studies for further developments, including beamtime for XFEL and ILC R&D. FLASH provides trains of fully coherent 10 to 50 femtosecond long laser pulses in the wavelength range from 40 nm to 6.8 nm. The SASE radiation contains also higher harmonics; several experiments have successfully used the third and fifth harmonics. The smallest wavelength used was 1.59 nm. We will give a summary of the experience from two years of user operation at FLASH.
DESY, Hamburg
INFN/LASA, Segrate (MI)
Caesium telluride photocathodes are used as laser driven electron sources at the Free-Electron-Laser Hamburg, FLASH, and will be used at the European XFEL. One concern of the operation of photocathodes in these user facilities is the degradation of the quantum efficiency during operation. After improving vacuum conditions and removing contaminants, the cathode life time increased from a couple of weeks to several months. In this contribution we report on long time operation of Cs2Te cathodes in terms of QE measurements and investigations on the homogeneity of the electron emission. Another concern of electron guns operated with long RF-pulses (0.8 ms at FLASH) is the generation of dark current either from the cathode or from the gun body. During the last years a constant high amount of dark current, emitted from the gun body itself, was observed at FLASH. Caused by that during the shut-down 2009/2010 the RF-gun at FLASH, operated more than five years, was replaced. The improved dark current situation with the new RF-gun is presented in terms of dark current measurements under different operational conditions.
DESY, Hamburg
Friedrich Schiller Universität, Jena
Uni HH, Hamburg
The performance of fourth generation light sources is of interest in many fields in nature science. Different seeding schemes for FELs are under investigation to improve timing stability, pulse shape and spectrum of the amplified XUV or X-ray pulses. One of the most promising schemes is direct seeding by high-harmonic generation (HHG) in gas. A seeded free electron laser with a tuneable wavelength range from 10 to 40nm and a bunch frequency of up to 100 kHz (1 MHz upgraded), as proposed for FLASH II (collaboration HZB/DESY), makes high demands on the HHG seed source concerning conversion efficiency and stability. However, the most challenging task is the conception of a laser system with a repetition rate of 100 kHz (1 MHz upgraded). The key parameters for this laser amplifier system are pulse energies of 1-2mJ and sub-10fs pulse duration. We report on the development status of the required laser system for the seed source and give an overview of first concepts for the HHG target setup which can comply with the requirements of a new seeded FEL at DESY.
Uni HH, Hamburg
PSI, Villigen
Westdeutsches Protonentherapiezentrum, Essen
DESY, Hamburg
sFLASH is a seeded FEL experiment at DESY, which uses a 38nm high harmonic gain (HHG)-based XUV-beam laser in tandem with FLASH electron bunches at the entrance of a 10m variable-gap undulator. The temporal overlap between the electron and HHG beams is critical to the seeding process. Use of a 3rd harmonic accelerating module provides a high current electron beam (at the kA level) with ~ 600fs FWHM bunch duration. The length of the HHG laser pulse will be ~30fs FWHM. The desired overlap is achieved in steps. First is the synchronization of the HHG drive laser (Ti: Sapphire, 800nm) and the incoherent spontaneous radiation from an upstream undulator. Next, the IFEL-modulated electron bunch will pass through a dispersive section, producing a density modulation in the beam. This in turn yields emission of coherent radiation from a downstream undulator or transition radiation screen when the longitudinal overlap of the two beams is achieved. The coherently enhanced light emitted will be then spectrally analyzed. The experimental layout, simulation results of generation and transport of both light pulses, and preliminary measurements are presented.
DESY, Hamburg
Helmholtz-Zentrum Berlin für Materialien und Energie GmbH, Elektronen-Speicherring BESSY II, Berlin
Uni HH, Hamburg
FLASH has been a user facility since 2005, delivering radiation in the wavelength range between 7 and 47 nm using the SASE principle. In order to increase user beam time and improve the radiation properties delivered to users, a major extension of the user facility called FLASH II has been proposed by DESY in collaboration with the HZB, which is a seeded FEL over the parameter range of FLASH. As logical continuation, the HHG development program started with sFLASH, will result in direct seeding. Because in the foreseeable future there will probably not be HHG seed lasers available at high repetition rates down to wavelengths of 4 nm, a cascaded HGHG scheme will be used to produce short wavelengths. After a first design report, the project now enters its preparation phase until the decision for funding will be taken. During this time, the FLASH beam parameters after the present upgrade 2009/2010 will be characterized and the present design will be re-evaluated and adjusted. In addition, complete start-to-end simulations will complete the simulations which have been performed so far, including a complete design of the extraction area.
DESY Zeuthen, Zeuthen
DESY, Hamburg
STFC/DL/ASTeC, Daresbury, Warrington, Cheshire
Helmholtz-Zentrum Berlin für Materialien und Energie GmbH, Berlin
Uni HH, Hamburg
The PITZ facility is established for the development and testing of electron sources for FELs like FLASH and the European XFEL. The facility has been upgraded during the shutdown starting in summer 2007 to extend the capability of the facility to produce and characterize low emittance electron beams. The upgraded setup mainly includes a photo cathode L-band RF gun with solenoid magnets for space charge compensation, a post acceleration booster cavity and several diagnostic systems. The diagnostic systems consist of charge and beam profile monitors, emittance measurement systems and spectrometers with related diagnostics in dispersive arms after the gun and the booster cavities. RF gun operation with an accelerating gradient of 60 MV/m at the cathode is realized with this setup. A new photo cathode laser system with broader spectral bandwidth was installed for optimizing the temporal distribution of the laser pulses regarding to electron beam properties. Experimental results with this setup demonstrated very high electron beam quality as required for the photoinjector source of the European XFEL. In this contribution, the PITZ facility setup in year 2008-2009 will be presented.
*for the PITZ Collaboration
DESY Zeuthen, Zeuthen
INRNE, Sofia
DESY, Hamburg
YerPhI, Yerevan
JINR, Dubna, Moscow Region
UCLA, Los Angeles, California
Helmholtz-Zentrum Berlin für Materialien und Energie GmbH, Berlin
MEPhI, Moscow
NSC/KIPT, Kharkov
MBI, Berlin
At the Photo Injector Test facility at DESY, Zeuthen site (PITZ), high brightness electron sources for linac based Free Electron Lasers (FELs), like FLASH and the European XFEL are developed and characterized. The electrons are generated via the photoeffect at a cesium telluride (Cs2Te) cathode and are accelerated by a 1.6-cell L-band RF-gun cavity with an accelerating gradient at the cathode of about 60 MV/m. The profile of the cathode laser pulse has been optimized yielding small emittances using laser pulse shaping methods. The transverse projected emittance is measured by a single slit scan technique. The measurement program in the last run period at PITZ concentrated on emittance measurements for the nominal 1 nC beam and emittance optimization for lower bunch charges. The recent results show that normalized projected emittances of about 1 mm-mrad for 1 nC charge and below 0.5 mm-mrad for 250 pC bunch charges can be realized at PITZ. The facility setup and measurement results including the uncertainty of the measured values will be reported and discussed in this contribution.