Ischebeck, R.

Paper	Title	Page
MOPPH055	Low Thermal Emittance Measurements at the PSI-XFEL Low Emittance Gun Test Facility	110
	Y. Kim, Å. Andersson, M. Dach, R. Ganter, C. Gough, C. P. Hauri, R. Ischebeck, F. Le Pimpec, M. Paraliev, M. Pedrozzi, T. Schietinger, B. Steffen, A. F. Wrulich PSI, Villigen
	To check performance of a planned low emittance gun (LEG) for the PSI XFEL project, a 500 kV pulsed diode based gun test facility was constructed at PSI in 2007. The gun was specially designed to have an adjustable gap between the cathode and the anode, and to allow extensive high gradient tests. Since the electron temperature at the cathode determines the minimum achievable slice emittance, we concentrated our efforts to measure the thermal emittance of a diamond turned copper cathode and stainless steel ones. To minimize emittance growth due to space charge effects, a single bunch with a charge of about 0.6 pC was used to characterize the beam. Since the experimental setup does not include an RF cavity, there was no dilution effects due to the non-linearity of the RF field. After optimizing the pulser to get a stable operation at 40 MV/m with the copper cathode, we could get about 0.2 mm.mrad range thermal emittance for a laser spotsize at the cathode of about 0.330 mm (RMS). In this paper, we report on our realistic thermal emittance measurements with copper and stainless steel cathodes at the LEG facility, which are much smaller than measured results by other laboratories.
	Slides
TUPPH003	Tolerance Studies on the High Harmonic Laser Seeding at Flash	235
	V. Miltchev, A. Azima, J. Boedewadt, H. Delsim-Hashemi, M. Drescher, S. Khan, Th. Maltezopoulos, M. Mittenzwey, J. Rossbach, R. Tarkeshian, M. Wieland Uni HH, Hamburg S. Düsterer, J. Feldhaus, T. Laarmann, H. Schlarb DESY, Hamburg R. Ischebeck PSI, Villigen
	Currently, the Free-electron-LASer at Hamburg (FLASH) operates in the Self-Amplified Spontaneous Emission (SASE) mode, delivering to users photon beams with wavelengths between 6.5 nm and 40 nm. In order to improve the temporal coherence of the generated radiation, it is planned to externally seed FLASH with higher harmonics of an optical laser. The project aims at seeding in the 30-13 nm range with stability suitable for user operation. In this contribution the performance of the seeded FEL is studied in simulations. Emphasis is placed on the tolerances of the most critical parameters such as transverse offset and angle between the electron beam and the external seed, timing jitter, energy of the seed pulse and the influence of the electron optics.
TUPPH051	Conceptual Ideas for the Temporal Overlap of the Electron Beam and the Seed Laser for sFLASH	363
	R. Tarkeshian, J. Boedewadt, M. Drescher, J. Rossbach Uni HH, Hamburg R. Ischebeck PSI, Villigen H. Schlarb, S. Schreiber DESY, Hamburg
	sFLASH is a seeding FEL experiment at FLASH/DESY, to introduce a 30nm HHG-based XUV-beam laser to the electron bunches of FLASH at the entrance of a 10m variable-gap undulator. The temporal overlap between the electron beam and HHG is important for the FEL process. The installation of a 3rd harmonic cavity at FLASH will provide a long high current electron beam (at kA level) over ~600fs (FWHM) bunch duration. The duration of the HHG laser pulse will be about 30fs (FWHM).The desired overlap can be achieved in steps. One approach will be to synchronize the drive laser (Ti:Sapphire, 800nm) of HHG and the incoherent spontaneous synchrotron radiation of the undulator at a sub-picosecond precision. In a following step the overlap can be improved by scanning within the sub-picosecond uncertainty. The possibility of using a streak camera to detect both the 800nm laser and the spontaneous undulator radiation pulses without perturbing FLASH user operation is investigated. To match the power levels, the laser beam has to be attenuated by several orders in magnitude. The layout of the experiment and preliminary simulation results of generation and transport of both light pulses are presented.