F. Staufenbiel

Femtosecond dynamics: snapshots of the early ion-track evolution

The energy dissipation and femtosecond dynamics due to fast heavy ions in matter is critically reviewed with emphasis on possible mechanisms that lead to materials modifications. Starting from a discussion of the initial electronic energy-deposition processes, three basic mechanisms for the conversion of electronic into atomic energy are investigated by means of Auger-electron spectroscopy. Results for amorphous Si, amorphous C and polypropylene are presented and discussed. Experimental evidence for a highly charged track region as well as for hot electrons inside tracks is shown. As follows mainly from Auger-electron spectroscopy, there are strong indications for different track-production mechanisms in different

Si-Auger electrons from the center of nuclear tracks

Using a new ultra-high vacuum system we were able to measure ion-induced Auger electron spectra with high resolution for atomically clean amorphous Si surfaces. Measurements were performed with Ne 9þ and Ar 16þ ions at 5 MeV/u, Xe 15þ and Xe 31þ ions at 1.78 MeV/u as well as with incident electron at the two speeds, corresponding to 2.7 keV respectively 1.0 keV. The ion-induced spectra show peaks due to multiple ionization, indicating 7- or 8-fold ionization in the center of ion tracks for fast Xe ions. The Auger peaks are shifted and broadened with respect to the electron reference data. This is an indication for the nuclear-track potential and for hot electrons being present during the decay of the Auger states. 2002 Published by Elsevier Science B.V.

Electron beam diagnostics for a superconducting radio frequency photoelectron injector

A superconducting radio frequency (SRF) photoelectron injector is currently under construction by a collaboration of BESSY, DESY, FZD, and MBI. The project aims at the design and setup of a continuous-wave SRF injector including a diagnostics beamline for the ELBE free electron laser (FEL) and to address R&D issues on low emittance injectors for future light sources such as the BESSY FEL. Of critical importance for the injector performance is the control of the electron beam parameters. For this reason a compact diagnostics beamline is under development, serving a multitude of operation settings. In this paper the layout and the rationale of the diagnostics beamline are described. Furthermore detailed information on specific components is given, together with results from laboratory tests and data taking.

Rossendorf SRF‐Gun Cavity Characteristics

At the Forschungszentrum Dresden‐Rossendorf the development and the setup of the 2nd superconducting radio frequency photo electron injector (SRF‐Photo‐Gun) is finished. This new injector is placed next to the existing thermionic gun of the superconducting linear accelerator ELBE. A connection between the accelerator and the SRF‐Gun will provide improved beam parameters for the users at the second half of 2009. At the moment the commissioning is fully under way. We will report on important results concerning cavity commissioning like measurements of: Q vs. E, microphonics, Lorentz detuning, tuner parameters, pressure sensibility and in‐situ fundamental mode field distribution calculated from measured pass band.

The new superconducting RF photoinjector at the ELBE linac

Most of the proposed electron accelerator projects for future free electron lasers, energy recovery linacs, or 4th generation light sources require electron beams with an unprecedented combination of high-brightness, low emittance and high average current. For that reason existing electron injectors must be considerably improved or new injector concepts developed. One very promising approach represents the superconducting radio frequency photoinjector (SRF gun). This injector type combines the advantages of a conventional photoelectron injector with that of superconducting acceleration, i.e. the very low RF losses and simple continuous wave operation. A SRF gun was developed and installed at Forschungszentrum Dresden-Rossendorf for operation at the ELBE superconducting linear accelerator. In November 2007 the first beam was produced. First commissioning results have been collected. Besides an improvement of beam quality and parameter range the SRF gun serves as a test bench for further development, evaluation and optimization since it is the first injector of its type which is operating at an accelerator worldwide

Al-K-Auger energy spectra: Probing the electron dynamics in ion-solid interactions

K-Auger electron emission has been investigated for incident electrons and for different types of heavy ions interacting with mono-crystalline aluminum (100) targets at specific kinetic energies of 3 to 5 MeV/u. In an effort to gain a profound knowledge about the ionization and vacancy-decay dynamics for the K-shell in Al, spectra have been measured with different energy resolutions and angular distributions have been taken as well. Here we concentrate on the energy spectra — we identify the measured peak structures and we investigate different line intensities and mean target charge-states quantitatively, in comparison with theoretical results.