115 research outputs found
Studies on charge production from Cs2Te photocathodes in the PITZ L-band normal conducting radio frequency photo injector
This paper discusses the behavior of electron bunch charge produced in an
L-band normal conducting radio frequency cavity (RF gun) from Cs2Te
photocathodes illuminated with ps-long UV laser pulses when the laser
transverse distribution consists of a flat-top core with Gaussian-like decaying
halo. The produced charge shows a linear dependence at low laser pulse energies
as expected in the quantum efficiency limited emission regime, while its
dependence on laser pulse energy is observed to be much weaker for higher
values, due to space charge limited emission. However, direct plug-in of
experimental parameters into the space charge tracking code ASTRA yields lower
output charge in the space charge limited regime compared to measured values.
The rate of increase of the produced charge at high laser pulse energies close
to the space charge limited emission regime seems to be proportional to the
amount of halo present in the radial laser profile since the charge from the
core has saturated already. By utilizing core + halo particle distributions
based on measured radial laser profiles, ASTRA simulations and semi-analytical
emission models reproduce the behavior of the measured charge for a wide range
of RF gun and laser operational parameters within the measurement
uncertainties.Comment: 15 pages, 16 figures, 2 table
Report on Gun Conditioning Activities at PITZ in 2013
Recently three RF guns were prepared at the Photo Injector Test Facility at DESY, location Zeuthen PITZ for their subsequent operation at FLASH and the European XFEL. The gun 3.1 is a previous cavity design and is currently installed and operated at FLASH, the other two guns 4.3 and 4.4 were of the current cavity design and are dedicated to serve for the start up of the European XFEL photo injector. All three cavities had been dry ice cleaned prior their conditioning and hence showed low dark current levels. The lowest dark current level as low as 60 amp; 956;A at 65MV m field amplitude has been observed for the gun 3.1. This paper reports in details about the conditioning process of the most recent gun 4.4. It informs about experience gained at PITZ during establishing of the RF conditioning procedure and provides a comparison with the other gun cavities in terms of the dark currents. It also summarizes the major setup upgrades, which have affected the conditioning processes of the cavitie
AN OPTION OF HIGH CHARGE OPERATION FOR THE EUROPEAN XFEL
Abstract The 1.3 GHz superconducting accelerator developed in the framework of TESLA and the European XFEL project holds the potential to accelerate high charge electron beams. This feature has been successfully demonstrated during the first run of the free electron laser at the TESLA Test Facility with lasing driven by electron bunches with a charge of up to 4 nC. Currently DESY and the European XFEL GmbH perform revision of the baseline parameters for the electron beam. In this report we discuss a potential option of operation of the European XFEL driven by high charge (1 nC to 3 nC) electron beams. We present the results of the production and characterization of high charge electron bunches. Experiments have been performed at PITZ and demonstrated good properties of the electron beam in terms of emittance. Simulations of the radiation properties of SASE FELs show that application of high charge electron beams will open up the possibility to generate radiation pulse energies up to the few hundred milli-Joule level
Simulations related to the electron bunches created from the specific temporal laser shapes for the plasma acceleration experiments at PITZ.
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