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With regard to the development of new accelerator technologies for high-intensity ion beams and more efficient acceleration, the transfer of radiation ions to higher charged states is a prerequisite for many experiments. However, the recent stripping technologies such as film and gas stripper for heavy ion beams with the desired intensities required great effort or are not suitable. The contribution presents the current state of plasma strippers with fully ionized hydrogen with simultaneously high particle densities in the range of some 10¹⁷ cm⁻³ for FAIR. To achieve this high particle density, an inductive discharge plasma is ignited within a stripper cell parallel to the axis of the ion beam and compressed towards the beam axis. The advantage over conventional ion strippers is about 1000 times smaller recombination rate for electrons*. This significantly increases the equilibrium charge state of ions. At the same time, the relative fraction of ions on the maximum of charge state distribution increases up to 25%**. This should create good conditions for the use of plasma strippers at FAIR., Proceedings of the 10th Int. Particle Accelerator Conf., IPAC2019, Melbourne, Australia

This contribution is about our recent studies of collision and compression of plasma sheaths, generated by coaxial plasma accelerators. One application is the development of a pulsed ion source producing high ion currents, coming along with high electron densities. The experiment is built up of an energy storage with up to 1,35kJ with a 2% Hydrogen in Helium gas mixture as working gas. The small fraction of Hydrogen is necessary to use the linear Stark-broadening of the H-line to determine the electron density, which is in the range up to 10¹⁵cm⁻³. By the collision of two plasma sheaths in an angle of 180°, the electron density has been increased by a factor of 2.5 compared to the single plasma sheath. As an alternative, the compression of the plasma by funnel geometries has been studied. As has been found, the achieved electron densities are more than a magnitude higher, compared to the values of the plasma collision. Thus, the H-line is broadened too high to be used. Alternatively, the broadening of a copper line by the quadratic Stark-effect has been calibrated and used to determine those high electron densities of about 10¹⁸cm⁻³., Proceedings of the 9th Int. Particle Accelerator Conf., IPAC2018, Vancouver, BC, Canada

This contribution shows the progress in the development of a plasma window at the institute for applied physics at Goethe University Frankfurt. A plasma window* is a membrane free transition between two regions of different pressure, enabling beam transmission from a rough vacuum area (~1 mbar) to a higher pressure (up to 1 bar) region on short length scales. In comparison to differential pumping stages a length reduction by a factor of up to 100 is achievable, while the absence of a solid membrane yields prolonged operation time. The sealing effect is based on the high temperature arc discharge sustained in a cooled copper channel between the pressure regimes. Due to a bulk temperature around 10,000K** the viscosity of the gas is dramatically increased, leading to a slower gas flow, enabling a higher pressure gradient. This contribution will present first results regarding the pressure gradient in dependence of the discharge current and the aperture. Until now, a pressure factor around 100 has been established for well over 50 min. This contribution goes along with the one from Mr. A. Michel, he focuses on the spectroscopic analysis of the arc plasma., Proceedings of the 9th Int. Particle Accelerator Conf., IPAC2018, Vancouver, BC, Canada

The planed Facility for Ion Research (FAIR) is a new international accelerator laboratory at the GSI in Darm-stadt, Germany. The main topic at this facility is aimed to heavy ion research. The FAIR project in comparison to the existing facility GSI extends the research area by raising the energy of ion beams. After creation of the ion beam at the ion source the state charge is low. Therefor the demand for acceleration of the beam to the highest possible energy is a highly ionized charge state of the beam. For beam stripping to get higher charge state, the traditional tools are gas stripper and foil stripper [1, 2]. Hence Plasma is suggested to be a stripper medium. In Frankfurt are different kinds of Pinch Plasmas under investigation for Stripper. The constricting effect on the plasma or conductor is produced by the magnetic field pressure resulting from the current or by the Lorentz force produced by the current flowing in its own magnetic field. In addition to separate the high pressure discharge cham-ber of the accelerator a plasma window will be used [3]. This contribution gives an overview of the plasma proper-ties and shows first results of different beam times at the GSI., Proceedings of the 7th Int. Particle Accelerator Conf., IPAC2016, Busan, Korea

The basic physics of nonrelativistic and electromagnetic ion stopping in hot and ionized plasma targets is thoroughly updated. Corresponding projectile-target interactions involve enhanced projectile ionization and coupling with target free electrons leading to significantly larger energy losses in hot targets when contrasted to their cold homologues. Standard stoppping formalism is framed around the most economical extrapolation of high velocity stopping in cold matter. Further elaborations pay attention to target electron coupling and nonlinearities due to enhanced projectile charge state, as well. Scaling rules are then used to optimize the enhanced stopping of MeV/amu ions in plasmas with electron linear densities nel ~ 10 18 -10 20 cm -2 . The synchronous firing of dense and strongly ionized plasmas with the time structure of bunched and energetic multicharged ion beam then allow to probe, for the first time, the long searched enhanced plasma stopping and projectile charge at target exit. Laser ablated plasmas (SPQR1) and dense linear plasma columns (SPQR2) show up as targets of choice in providing accurate and on line measurements of plasma parameters. Corresponding stopping results are of a central significance in asserting the validity of intense ion beam scenarios for driving thermonuclear pellets. Other applications of note feature thorium induced fission, novel ion sources and specific material processing through low energy ion beams. Last but not least, the given ion beam-plasma target interaction physics is likely to pave a way to the production and diagnostics of warm dense matter (WDM).

Contribution to Proceedings, Proc. of PATRAS08; DESY-PROC-2008-02; ISSN 1435-8077

Three researchers working in the new field of astroparticle physics argue the case for making the data from astroparticle experiments public.