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Notes: Abstract: The time course of changes in the tissue impedance and the levels of extracellular transmitter and non-transmitter amino acids was studied in the striatum and hippocampus of the unanesthetized rat after cardiac arrest. Electrodes were implanted for the continuous measurement of tissue impedance so that a measure of the volume of extracellular space was provided. Alternatively, bilateral dialysis probes were used for monitoring levels of extracellular amino acids in subsequent 30-s samples using an automated precolumn derivatization technique for reversed-phase HPLC analysis and fluorimetric detection. The impedance started to rise ∼1.2 min following cardiac arrest, increased rapidly during the first 5 min, and increased almost linearly thereafter. After 15 min, a decrease of ∼50% in the extracellular space was calculated. The impedance rose more steeply in the striatum than in the hippocampus. The extracellular levels of taurine, which increased 〉300% within 5 min after cardiac arrest, most closely resembled the time course of the change in impedance. Glutamate and aspartate levels did not increase until 5 min after circulatory arrest, and at 15 min they had risen to a level of 465 and 265% for the striatum and 298 and 140% for the hippocampus of the resting release, respectively. The release of γ-aminobutyric acid (GABA) was multiphasic and did not resemble that of any of the other—putative—transmitter amino acids. Fifteen minutes after cardiac arrest, the levels of GABA were 617 and 774% of the resting release in the striatum and hippocampus, respectively. Glycine and ala-nine efflux substantially increased (232 and 151% in striatum and 141 and 154% in hippocampus, respectively) 15 min postmortem, whereas the glutamine level was slightly increased and levels of asparagine, histidine, threonine, ethanolamine, serine, arginine, and tyrosine were inconsistently higher in the two brain regions. At this time, the extracellular levels of glutamate, GABA, and aspartate were only slightly lower, as expected from the tissue levels and from levels of the other amino acids, an observation indicating that all the amino acids may diffuse through postmortem brain tissue to a nearly similar extent. This study provides evidence that extracellular levels of taurine reflect changes in distribution of electrolytes (and in membrane potentials), that the postmortem release of transmitter amino acids is multiphasic with a delay of at least 1 min, that postmortem shrinkage in extracellular volume cannot account for the increase in the content of transmitter amino acids in the dialysate, and that the massive overflow of glutamate, aspartate, GABA, and taurine seen during ischemia is the result of both release and the failure of uptake. Possible implications of the present findings for excitotoxic damage of the brain are discussed.

Notes: We present measurements on multichannel acceleration of intense, low-energy ion beams with a multiple electrostatic quadrupole array linear accelerator. The beam properties are investigated for different transverse and longitudinal focusing strengths, which can be adjusted independently in the accelerator. A maximum He+ ion current of four times 2 mA has been accelerated from 40 to 115 keV with an acceleration efficiency of 50%. Measurements and computer simulations suggest that the current is limited by transverse fields and by mismatch and misalignment of the beams, whereas longitudinal fields are of minor importance. The energy spread in the bunches is roughly three times the gap voltage.

Notes: A volume source, based on the high efficiency ion source (HIEFS), is being developed for D+ production in steady state operation. The source will be optimized for the extraction of atomic deuterium ions with high current densities. It was found that a maximum deuterium ion beam current density of 210 mA/cm2 can be achieved with a D+ fraction above 90%. At an extraction voltage of 35 kV and with an aperture radius of 4 mm, the source delivers 61 mA D+. After a description of the source and the experimental setup, the results of detailed studies of the beam composition in dependence of the plasma parameters are presented. © 1996 American Institute of Physics.

Notes: Slit-grid emittance measurement devices usually do not scan the beam continously but in fixed linear (x) and angular (x') steps. Thus in an emittance measurement performed with a slit-grid system, the beam is represented by a number of phase space boxes with a constant area or volume determined by the linear and angular resolution. Considering the emittance as the area in the two-dimensional subspace (x,x') covered by the beam, the quantization error and its dependence on the resolution (linear and angular) as well as the influence of the beam parameters is discussed. Measuring the very low emittance of the high efficiency source (HIEFS) proved that the quantization error can be unacceptably high ((very-much-greater-than)100%). With an optimized measuring device, the normalized emittance came down from 10−1 to 3.6×10−3 π mm mrad. Finally, a typical misleading result of an emittance measurement, caused by the quantization error, is presented.

Notes: For the European spallation source, a volume source based on the high efficiency source is being developed. The source will be optimized to produce high current densities in pulsed operation. A pulse generator delivering 1–1.5 ms pulses was installed. Furthermore, cesium was supplied to the plasma generator from an external oven. The cesium injection was optimized for a low e/H− ratio and a high current. We obtained a current density of 70 mA/cm2. This way, with an aperture radius of 4.25 mm, an H− current of 40 mA was extracted at an extraction voltage of 22 kV. After a description of the source and the experimental setup, measurements of the beam current density and the e/H− ratio will be presented in this article. © 1998 American Institute of Physics.

Notes: For the International Fusion Materials Irradiation Facility (IFMIF) scenario, a 140 mA deuterium beam in continuous wave (cw) mode with an atomic yield of above 85% is required. The normalized root-mean-square emittance should be less than 0.2 π mm mrad at the entrance of a RFQ. As part of a conceptual design for IFMIF, a new ion source has been developed and is tested at the Institut für Angewandte Physik in Frankfurt. The ion source is of the volume type with a tungsten cathode driving the discharge. Both cw and pulsed mode are possible and were studied. First experiments were carried out with deuterium. 80 mA deuterons with a D+ fraction of above 90% were extracted [A. Maser et al., Rev. Sci. Instrum. 67, 1054 (1996)]. In order to avoid neutron generation by the d–d reaction, hydrogen was used instead of deuterium later on. As far as the ion source and plasma production processes are concerned, the use of hydrogen instead of deuterium is equivalent because of their similar atomic shells. Recently, a 200 mA proton beam at 55 kV was extracted in cw mode (according to Child–Langmuir, 200 mA H+ corresponds to 140 mA D+) with a H+ fraction of 93%. This article will give a detailed description of the ion source and the essential experimental results. Especially, the influence of important physical parameters (such as discharge current and strength of the filter field) on the H+ fraction was studied. By using different kinds of auxiliary gases, the influence on the H+ fraction and the noise level were investigated, too. © 2000 American Institute of Physics.

Notes: A new version of the high efficiency source is being developed for the European Spallation Source. The goal of these experiments is to produce a nearly pure H− ion beam with a low electron to H− ratio and high current (70 mA). To achieve this, the discharge chamber is divided into two parts of different plasma parameters by means of a filter magnetic field. Furthermore, the plasma chamber is aligned unsymmetrically with respect to the z axis of the extractor. We obtained a current density of 10 mA/cm2 for an arc power as small as 1 kW. In preliminary experiments, a beam of 10 mA was extracted at an extraction voltage of 8 kV (1.8% impurities). Measurements of the beam current density, electron to H− ratio, and the ion composition for a wide range of discharge conditions will be presented in this article. © 1996 American Institute of Physics.

Notes: An ion beam facility for high-intensity beams of highly charged ions in the energy range between 1 and 200 keV/u has been funded and will be installed in 1992 at the Institut für Kernphysik, Frankfurt am Main, Germany. The facility is based on a 14.6 GHz ECR ion source and a variable-energy RFQ as postaccelerator. The facility is intended for atomic-physics and materials research.