Rossbach, J.

Paper	Title	Page
MOYAGM01	Review of DESY FEL Activities	7
	J. Rossbach Uni HH, Hamburg J. Rossbach DESY, Hamburg
	A general overview will be given of DESY FEL activities. Overview of the technological upgrades and results of beam commissioning of the FLASH FEL. The talk will cover the latest results from FLASH at the shortest wavelengths. A description will be given of critical systems and performance. The status of the XFEL will be given, including integration of FLASH technology.
	Slides
MOPC029	Longitudinal Structure of Electron Bunches at the Micrometer Scale from Spectroscopy of Coherent Transition Radiation	130
	B. Schmidt, C. Behrens, S. Wesch DESY, Hamburg H. Delsim-Hashemi, J. Rossbach, P. Schmüser Uni HH, Hamburg
	At the free electron laser FLASH in Hamburg, a longitudinal bunch compression scheme is used resulting in a longitudinal current profile with a narrow leading spike. Part of this spike is responsible for producing high-intensity short FEL pulses via the SASE process. The width and the structure of the current spike, which are key parameters for the efficiency of the SASE process, are barely accessible to direct measurements in the time domain. Using an infrared multi-stage grating spectrometer, we have studied the spectral composition of coherent transition radiation from single electron bunches. The data show that the 'fundamental width' of the current spike is about 40 fs (fwhm) with prominent substructures down to the 10 fs scale. The intensity fluctuations of coherent radiation in the corresponding wavelength range are strongly correlated to the fluctuations of the FEL pulse energy. Extension of the method to the near infrared regime have revealed micro-structures with characteristic lengths from a few micrometers down to fractions of a micrometer. Their interrelation with the parameters of the electron beam and the compression system have been studied.
MOPC028	Experimental Layout of 30 nm High Harmonic Laser Seeding at FLASH	127
	H. Schlarb, S. Düsterer, J. Feldhaus, T. Laarmann DESY, Hamburg A. Azima, J. Boedewadt, H. Delsim-Hashemi, M. Drescher, S. Khan, Th. Maltezopoulos, V. Miltchev, M. Mittenzwey, J. Rossbach, R. Tarkeshian, M. Wieland Uni HH, Hamburg
	Since 2004, the free-electron laser FLASH at DESY has operated in the Self-Amplified Stimulated Emission mode, delivering to users photon beams with wavelengths between 6.5 nm and 40 nm. In 2009, DESY plans to install a 3.9 GHz RF acceleration section for the production of electron bunches with high peak currents (~kA), but ten times larger pulse durations (~250 fs) compared to the present configuration. The relaxed timing requirements of the new configuration make it possible to externally seed FLASH with high harmonics of an optical laser (sFLASH). The aim of the project is to study the technical feasibility of seeding an FEL at 30 nm with a stability suited for user operation. sFLASH will use 10 m of gap-tunable undulators installed in front of the fixed gap SASE-undulator. A chicane behind the seeding undulators will allow to extract the output radiation for a careful characterisation and for first pump-probe experiments with a resolution in the 10 fs range by combining FEL and seed laser pulses.
MOPC140	Status of the Multipurpose Fully Superconducting ECR Ion Source	400
	G. Ciavola, L. Celona, S. Gammino, F. Maimone, D. Mascali INFN/LNS, Catania H. A. Koivisto JYFL, Jyvaskyla R. Lang, J. Maeder, J. Rossbach, P. Spaedtke, K. Tinschert GSI, Darmstadt
	The MSECRIS source has been designed with the aim to exceed the highest currents of highly charged heavy ions available up to now. It is based on a minimum B trap made of a hexapole and three solenoids. The design magnetic field is 2.7 T for the hexapole and 4.5 T for the mirror field, in order to permit to operate not only at 28 GHz but also at higher frequency, thus increasing the plasma density and finally the beam current. Such high level of magnetic field is a challenge because of the forces arising on the superconducting coils and it largely exceeds the highest magnetic field available for existing ECRIS. A description of the source and of its preliminary results will be given. The source has been built in the frame of the European collaboration EURONS/JRA07-ISIBHI and it is now installed at the EIS testbench of GSI.
TUPC030	Transverse Electron Beam Size Effect on the Bunch Profile Determination with Coherent Radiation Diagnostics	1113
	O. Grimm, H. Delsim-Hashemi, J. Rossbach Uni HH, Hamburg V. Balandin, N. Golubeva DESY, Hamburg
	Longitudinal diagnostics of electron bunches can be done by measurement of coherent radiation (e.g., in the form of transition radiation) and subsequent extraction of the form factor. By measuring short wavelengths, fine structures in the bunch can be resolved. However, the form factor depends on the three-dimensional charge density distribution, and the usual practice of considering only a one-dimensional line charge in interpreting the radiation spectra is questionable, as the finite transverse extend of the electron bunch can reduce the form factor magnitude at short wavelengths. An experimental study of this issue using a two stage single shot spectrometer has been carried out at the FLASH free-electron laser at DESY, Hamburg. The coherent transition radiation spectra for two beam optics settings were recorded and compared. In one setting the transverse beam size at the transition radiation target screen has been blown up by a factor of about 3.5 compared to the second setting. The ratio of these two spectra shows a suppression of radiation intensity at short wavelengths, as expected from a theoretical calculation. In this paper the result of this study is presented.
TUPC031	Longitudinal Beam Diagnostics Application of Synchrotron Radiation at FLASH	1116
	O. Grimm, J. Rossbach Uni HH, Hamburg C. Behrens, B. Schmidt DESY, Hamburg
	For the operation of the FLASH free electron laser at DESY, Hamburg, tools to measure the longitudinal charge distribution and especially its stability over time are important for efficient machine running. Several techniques using both coherent far-infrared and incoherent visible synchrotron radiation from the two bunch compressor chicanes are summarized and compared in this paper. The experimental setups used are a Martin-Puplett interferometer with both a room-temperature pyroelectric and a liquid-Helium cooled bolometer as detector, a streak camera to directly measure the time profile, the analysis of intensity fluctuations of the optical synchrotron radiation measured (with a photomultiplier) through a narrow filter, a single shot grating spectrometer covering the spectral range from 5 μm to 150 μm. Data from the various and complementary experimental methods will be presented and compared.
TUPC110	Bunch Diagnostics with Coherent Infrared Undulator Radiation at FLASH	1320
	A. Willner, H. Delsim-Hashemi, O. Grimm, J. Rossbach Uni HH, Hamburg B. Schmidt DESY, Hamburg
	The operation of the FLASH free electron laser at DESY, Hamburg, requires a high electron beam quality, one important parameter being the longitudinal charge distribution. As a new tool for investigations using coherent radiation techniques, FLASH has been equipped with an electromagnetic undulator. The device is tunable up to a maximum K-Value of 44, corresponding to 200 um wavelength at an electron energy of 500 MeV. The emitted radiation has been characterized in a first measurement campaign using a dispersive spectrometer based on reflective blazed gratings and a pyroelectric detector, operated in a Nitrogen-purged atmosphere. This paper will summarize the measurements and the results obtained from a longitudinal diagnostics analysis.
TUPP076	Longitudinal and Transverse Impedances of XFEL Kicker Vacuum Chamber	1712
	A. V. Tsakanian, J. Rossbach Uni HH, Hamburg M. Ivanyan CANDLE, Yerevan
	In European XFEL project beam delivery system the kicker magnet vacuum chamber design is composed of the ceramic pipe coated with Titanium Stabilized High Gradient Steel. In this paper the results of the study for the longitudinal and transverse impedances for such a laminated vacuum chamber are presented. The field matching technique is used to calculate the vacuum chamber impedances. The loss and kick factors are given.