H. Wahl

Energy loss of heavy ions in a dense hydrogen plasma

The energy loss of heavy ions with an energy of 1.4 MeV/u in a hydrogen plasma has been measured. A 20 cm longz-pinch has been used as plasma target. Our data show a strong enhancement of the stopping power of the plasma compared to that of a cold gas with equal density. The results completely confirm the predictions of the standard stopping power model.

Shockwave-driven, non-ideal plasmas for interaction experiments with heavy-ion beams

Plasma targets for measuring energy loss and charge-state distribution of heavy ions in non-ideal plasmas have been developed. Ar plasmas with Γ-parameters 0.55–1.5 could be realized and the interaction with several ion species studied. Here, the results for 5.9 MeV/u C ions are presented. The energy loss in plasma was reproduced in different experiments.

Overview of warm-dense-matter experiments with intense heavy ion beams at gsi-darmstadt

This paper presents an overview of the warm-dense-matter physics experiments with intense heavy ion beams that has been carried out at the Gesellschaft fur Schwerionenforschung (GSI), Darmstadt, Germany. These experiments are a joint effort of GSI-Darmstadt, TU-Darmstadt, ITEP-Moscow, IPCP-Chernogolvka and LBNL-Berkeley. In the performed experiments, electron-cooled beam of 238U73+ ions with initial ion energy of 350 AMeV has been used. The intense, up to 2.5 - 109 ions/bunch, ion pulses have been compressed to 110 ns (FWHM) and focused at the target to a spot down to 150 mum diameter. The beam intensity and the pulse shape have been measured by current transformers installed in front of the target chamber whereas the upper limit for the focal spot size has been determined by recording beam-induced emission of argon gas at ionic spectral lines. It was shown that using intense heavy ion beam that is presently available at GSI and employing the HIHEX beam-target design concept, it is possible to investigate basic thermodynamic and transport properties of HED metal states in the two-phase liquid-gas region and near the critical point.

Transport experiments of a 2.2 GeV gold ion beam in a plasma channel at the GSI-UNILAC facility

Charged particle beam transport in plasma channels is a well-established technique for electron and proton beams in the 1 MeV particle energy range. Experiments with heavy ion beams were started at the GSI-UNILAC accelerator facility to explore the applicability of this transport mode to heavy ion beam driven inertial confinement fusion. These experiments investigate the ion optics of a laser-initiated discharges. With the help of a TEA-CO/sub 2/ laser a discharge is initiated in low pressure (5 to 20 mbar) ammonia gas. A capacitor bank (1.33-8 /spl mu/F), charged up to 20 kV, is then triggered and a straight plasma channel is produced along the laser path. The current can be increase up to 45 kA. Fast shutter photography was used to study the stability of the channel. Magnetic field measurements were performed with dB/dt loops. The influence of the magnetic probe on the discharge was checked using an interferometer set-up. A 2.2 GeV gold ion beam was used to probe the ion optical properties of the channel.

Interaction of heavy ions with hot ionized matter

The energy loss of heavy ions in a hydrogen plasma has been measured in an energy range from 1.4 to 6 MeV/u. A z-pinch has been used as a plasma target with a maximum free electron density of 1.5×1019 cm−3. Our data show a strong enhancement of the stopping power of the plasma compared to that of a cold gas with equal density. Charge state analysis of the ions also show a higher charge state of the ions in the plasma target, relative to the cold hydrogen gas targets. A plasma lens effect of the high power z-pinch discharge was observed in our experiments.