[en] Based on the idea of D. Gabor space charge lenses are under investigation to be a powerful focussing device for intense ion beams. A stable confined electron column is used to provide strong radially symmetric electrostatic focussing, e.g. for positively charged ion beams. The advantages of Gabor lenses are a mass independent focussing strength, space charge compensation of the ion beam and reduced magnetic or electric fields compared to conventional focussing devices. Collective phenomena of the electron cloud result in aberrations and emittance growth of the ion beam. The knowledge of the behaviour of the electron cloud prevents a decrease of the beam brilliance. Numerical models developed to describe the electron confinement and dynamics within a Gabor lens help to understand the interaction of the ion beam with the electron column and show the causes of non-neutral plasma instabilities. The diagnosis of the electron cloud properties helps to evaluate the numerical models and to investigate the influence of the ion beam on the confined non-neutral plasma. (author)

[en] Low energy beam transport (LEBT) for a heavy ion inertial fusion (HIDIF, I. Hofmann and G. Plass, Report of the European Study Group on Heavy Ion Driven Inertial Fusion for the Period 1995-1998) facility suffers from high space charge forces and high ion mass. Space charge compensation reduces the necessary focusing force of the lenses and the radius of the beam in the LEBT, and therefrom the emittance growth due to aberrations and self fields is reduced. Gabor lenses (D. Gabor, Nature 160 (1947)) providing a stable space charge cloud for focusing and combine strong cylinder symmetric focusing with partly space charge compensation and low emittance growth. A high tolerance against source noise and current fluctuations and reduced investment costs could be other possible advantages. The proof of principle has already been demonstrated (J.A. Palkovic, Measurements on a Gabor lens for Neutralizing and Focusing a 30 keV Proton beam, University of Wisconsin, Madison, 1989; J. Pozimski, P. Gross, R. Doelling and T. Weis, First experimental studies of a Gabor plasma-lens in Frankfurt, Proceedings of the 3rd EPAC Conference, Berlin, 1992). To broaden the experiences and to investigate the realisation of a LEBT concept for the HIDIF injector an experimental program using two Gabor lenses for independent variation of beam radius and envelope angel at RFQ injection was started. Therefrom the first experimental results using a double Gabor lens (DGPL) LEBT system for transporting an high perveance Xe⁺ beam are presented and the results of numerical simulations are shown

[en] Since the last 20 years, modern heuristic algorithms and machine learning have been increasingly used for several purposes in accelerator technology and physics. Since computing power has become less and less of a limiting factor, these tools have become part of the physicist community’s standard toolkit [1][2] [3] [4] [5]. This paper describes the construction of an algorithm that can be used to generate an optimised lattice design for transfer lines under the consideration of restrictions that usually limit design options in reality. The developed algorithm has been applied to the existing SIS18 to HADES transfer line in GSI. (paper)

No abstract available

[en] For the investigation of electron–ion interaction processes, a new transverse electron target is under development. It opens the perspective to new types of experiments with ions by applying the ‘crossed beam’ technique for free electrons to a storage ring. The new target is suited for the UHV requirements of a storage ring and realizes an open geometry giving access to the interaction region for photon and electron spectroscopy under large solid angles. It is based on a simple design using only electrostatic fields for the focus of the sheet beam. The adjustable electron energy ranges between several tens of eV and a few keV. The electron target is dedicated to the storage rings of the Facility for Antiproton and Ion Research. First measurements are planned at a test bench, and subsequent tests at the Frankfurt Low Energy Storage Ring are envisaged. (paper)

[en] Full text: Almost all of the heavy elements are produced via neutron-induced processes in a multitude of stellar production sites. The remaining minor part is produced via - and proton-induced reactions. The predictive power of the underlying stellar models is currently limited because they contain poorly constrained physics components such as convection, rotation or magnetic fields. An important tool determine such components is the comparison of observed with modeled abundance distributions based on improved nuclear physics input. The FRANZ facility at the Goethe University Frankfurt, which is currently under construction will provide unprecedented neutron fluxes and proton currents available for nuclear astrophysics. It will be possible to investigate proton- and neutron-induced reactions important for p-process nucleosynthesis. At the GSI close to Darmstadt radioactive isotopes can be investigated in inverse kinematics. This allows experiments such as proton-induced cross section measurements using a heavy ion storage ring or γ-induced reaction measurements using the Coulomb dissociation method. The future FAIR facility will allow similar experiments on short-lived nuclei, since orders of magnitude higher radioactive ion beams will be possible.

[en] Space charge lenses provide strong cylinder symmetric focusing for low-energy high-perveance particle beams using a stable space charge cloud. They need drastically reduced magnetic and electrostatic field strength compared with conventional systems and are superior for a degree of lens filling above 17%. They can theoretically provide linear transformation in phase space and reduce beam aberrations and space charge forces. The density distribution of the enclosed space charge is given by the transverse and longitudinal enclosures of the cloud. By the use of self-consistent simulations of the space charge cloud, the focusing properties of space charge lenses in the presented design can be forecasted with sufficient quality. The presented simulations show that the theoretical values can be reached locally. The results of our investigations on the beam transport in a high-current test injector equipped with space charge lenses, including emittance measurements, will be presented and discussed. They show that significant improvements of lens operation have been reached by the reduction of the residual gas pressure and a careful design of the external fields using numerical simulation techniques to calculate the local density distributions. Comparisons of the experimental results with the beam transport simulations show good agreement concerning both focusing strength and linearity of phase space transformation. For the lens design used, the observed degree of lens filling is at least 38% of the theoretical value and more than twice the threshold value

[en] For high power proton accelerators like SNS, ESS or the planned neutrino factory (CERN), negative ions are preferred because they offer charge exchange injection into the accumulation rings (non Liouvillian stacking). The low energy beam emittance is a key parameter in order to avoid emittance growth and particle losses in the high-energy sections. Conventional destructive emittance measurement methods like slit-harp systems are restricted for high power ion beams by the interaction of the ion beam with e.g. slit or harp. Therefore a non-destructive emittance measurement has several technical and physical advantages. To study the transport of high perveance beams of negative ions, a Low Energy Beam Transport (LEBT) section is under construction. The study of non destructive emittance measurement devices is one major subject of the test bench. For negative ions - especially H-ions - photodetachment can be applied for a non-destructive emittance measurement instrument (PD-EMI). The paper will present the status of that emittance diagnostic and of the test bench

[en] The transport of intense ion beams is affected by the collective behavior of this kind of multi-particle and multi-species system. The space charge expressed by the generalized perveance dominates the dynamical process of thermalisation, which leads to emittance growth. To prevent changes of intrinsic beam properties and to reduce the intensity dependent focusing forces, space charge compensation seems to be an adequate solution. In the case of positively charged ion beams, electrons produced by residual gas ionization and secondary electrons provide the space charge compensation. The influence of the compensation particles on the beam transport and the local degree of space charge compensation is given by different beam properties as well as the ion beam optics. Especially for highly charged ion beams, space charge compensation in combination with poor vacuum conditions leads to recombination processes and therefore increased beam losses. Strategies for providing a compensation-electron reservoir at very low residual gas pressures will be discussed

[en] A magnetic Low-Energy Beam-Transport line for negatively-charged hydrogen ions was set up in Frankfurt, Germany. In order to study the space-charge compensation process several conventional beam diagnostic principles were already established. But to prevent compensated ion beams from distortions caused by conventional measurement devices, non-destructive methods are to be developed: Investigations were carried out to determine the emittance of the ion beam based on laser driven photon detachment of the H--electron using a non-destructive method. This method is capable of determining the transverse phase space distribution with high time resolution and a large number of phase space points. Additional non-destructive diagnostic tools are installed to study the temporal development of the compensation process. For time resolved measurements an optical device using CCD-cameras for beam profile measurements, a Residual Gas Energy Analyzer, and an Electron Energy Analyzer for beam potential measurements were installed. The working principles of the measurement devices as well as the whole test bench and planned activities are described