Experiments with merged electron and ion beams at the Heidelberg Test Storage Ring (TSR) are described. The experimental conditions of radiative and dielectronic recombination measurements are discussed. Results are presented for the radiative recombination rates of bare C and Cl nuclei, and for the dielectronic recombination of H-like, He-like, and Li-like ions up to charge 26.

State-resolved cross sections for the dielectronic recombination of hydrogenlike oxygen ions with free electrons have been measured for the first time using the electron cooling device in the heavy-ion Test Storage Ring in Heidelberg. Energies and cross sections for individual terms of the configuration 2l2l' were determined. Two-electron resonances 2lnl' with n\ensuremath{\ge}3 contribute 90% to the total dielectronic-recombination cross section. Energies and cross sections are in reasonable agreement with available calculations.

An overview of atomic physics experiments at the heavy ion Test Storage Ring (TSR) is given. Highly charged ions up to fully stripped silicon have been stored at energies between 4 and 12 MeV/u. The enhancement of the beam intensity by stacking, the beam lifetime, and electron cooling of these ion beams are discussed. Radiative and state‐selective dielectronic recombination rates of hydrogen‐like oxygen ions with free electrons from the electron cooler were measured. Beam noise spectra are being investigated with regard to collective effects caused by the Coulomb interaction in the cold ion beams. Resonance fluorescence from stored single‐charged ions was observed using tunable narrow‐band lasers. First indications of laser cooling in a storage ring were seen.

The production of antihydrogen by merging beams of antiprotons and positrons is described. Both beams, kept in storage devices, are continuously recirculated. Antihydrogen is formed by radiative recombination of positrons and antiprotons. Production rates of a few thousand per second are expected. The semi-relativistic atomic beam of antihydrogen would have a divergence of less than 1 mrad and a beam diameter of a few millimeter. The possibilities to increase these rates by induced recomtination are discussed. The scheme of antihydrogen production in overlapping beams is compared to other approaches.

The Heidelberg heavy ion test storage ring TSR started operation in May 1988. The lifetimes of the ion beams observed in the first experiments can be explained by interactions with the residual gas. Multiple Coulomb scattering, single Coulomb scattering, electron capture and electron stripping are the relevant processes. Electron cooling of ions as heavy as O8+ has been observed for the first time. With increasing particle number, the longitudinal Schottky noise spectrum becomes dominated by collective waves for cooled beams, allowing a determination of velocities of sound. After correcting for these coherent distortions fo the Schottky spectrum, the longitudinal beam temperature could be extracted. The observed longitudinal equilibrium beam temperatures increase strongly with the charge of the ions. For a cooled C6+ beam, temperatures a factor of 120 higher were measured compared to a proton beam with the same particle number. The shrinking of the beam diameter due to electron cooling was observed with detectors which measured the profile of charge-changed ions behind a bending magnet. A strong laser-induced fluorescence was detected when storing metastable 7Li+ ions in the ring. Via the Doppler effect a very accurate measurement of the ion velocity profile could be performed. First attempts to observe laser cooling failed, probably due to heating effects from intrabeam scattering and a coupling between longitudinal and transversal motion in the beam. Several experiments under preparation are outlined.

Thomson scattering of laser light was applied to a relativistic cooling electron beam. High-power laser pulses were necessary because of the very low scattering cross section. A spectrometer of high resolution and large background suppression factor in combination with time-gated photon counting served for signal detection. Analysis of Doppler shift and broadening of the backscattered light provided the determination of the electron beam energy with a precision of 2 × 10-3, and an upper limit of the longitudinal energy spread of 10-3 eV. A ratio of longitudinal to transverse electron temperature of 10-2 was found, indicating a flattened velocity distribution as is expected from the acceleration of the electrons.

First results are presented from an experiment scattering laser light from a relativistic electron beam. The 5 cm diameter continuous electron beam of 28 keV kinetic energy and 2.6 A current presents an electron gas of a density of 8×107 cm−3, from which 20 ns pulses of laser light (490 nm) were scattered at a repetition rate of 15 Hz and an average power of 20 mJ per pulse. The Doppler-shifted wavelength of photons backscattered under 180° was analysed with a Fabry-Perot interferometer. This technique provides, for the first time, a non-destructive measurement of the velocity distribution in an electron beam radially resolved in space. The results presented here comprise the direct measurement of the absolute electron energy and the degree of space-charge compensation in the electron beam. The determination of an upper bound of 10−2 for the ratio of longitudinal to transverse electron temperature implies the first direct measurement of a flattened velocity distribution.

The method of Thomson scattering frequently used as a diagnostic tool for plasmas /1/ and in few cases for very dense electron beams /2,3,4/, was applied for the first time to a much less dense cooling electron beam. The measurements performed at the electron cooling device for LEAR (Low Energy Antiproton Ring) at CERN demonstrate that it is feasible to determine the absolute energy and the longitudinal velocity distribution (temperature) of an electron beam with a density of less than 108 cm-3.

Storage of nanosecond megawatt dye laser pulses in a folded, confocal Fabry-Perot resonator of 4.5 m length is described. A p-polarized pulse enters the resonator through a polarizing beam splitter placed at the folding angle, passes an activated electro-optic Q-switch thereby experiencing a rotation to s-polarization, and is reflected from a cavity mirror. The second Q-switch transit leaves the s-polarization unaffected, since the activating voltage is set to zero immediately after the first passage. The pulse is now reflected by the beam splitter, hits the other resonator mirror and then travels back and forth in the cavity. The configuration can be used particularly to overlap a laser pulse repeatedly with a particle beam propagating in the cavity, at a constant crossing angle or parallel. By this means, the duty cycle for light-matter interaction can be increased considerably.

108 adult patients and 34 children with chronic active hepatitis (CAH) are divided in four groups on the basis of presence and absence of hepatitis B surface antigen (HBsAg) and autoantibodies (AutoAb). There are significant differences in the numeric distribution among the four groups and the sex distribution between adult patients and children, but no differences in the frequencies of the HLA antigens tested. An increased frequency of HLA-B8 (and HLA-A1) compared with normal controls and the other groups is only found in autoimmune types of CAH, characterized as HBsAg-negative, AutoAb-positive CAH. HBsAg-negative, AutoAb-negative forms of CAH are called cyptogenic CAH and these are most likely non-hepatitis B virus induced types of CAH. In these and hepatitis B virus induced forms of CAH no significant deviation of any HLA antigen tested could be found.