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The kinetics of the Fe/Fe2+ electrode have previously been explained on the basis of either a consecutive or a catalytic charge transfer mechanism including adsorbed intermediates. In order to obtain more exact kinetic information, pulse and frequency response measurements on polycrystalline Fe in acidic sulfate solutions at T=298°K have been carried out. The stationary current density‐potential curves already allow a preselection of the proposed reaction models. Dynamic parameters were calculated from the measured electrode impedance. It is shown that the existing reaction models do not agree with the measured impedance behavior. However, the experimental results can be explained assuming a potential‐dependent relaxation of the surface combined with a catalyzed dissolution mechanism. The mechanism of the iron electrode in the active, transition, and prepassive ranges can be described by the reaction schemeFe⇌)(normalFeOHads⇌][Fe*)(normalFeOHads→normalFeOH++)(normalFeOHads⇃↾⇃↾normalFe2+⋅aq.⇃↾][normalFeOH2ads⇌}{Fe*][normalFeOH2ads→normalFeOH++)(normalFeOHads

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A high resolution, fast neutron, time-of-flight spectrometer used for neutron energies between about several hundred kiloelectron volts and 30 .MeV is described. A 1 nsec neutron pulse occurring with a repetition rate of 20 kc is obtained with a novel "bunching deflection" system operating on the internal beam of the fixed energy Karlsruhe isochronous cyclotron. By the timing of the neutrons over a 57 m f1ight path aresolution of 0.025 nsec/ni at optimum was obtained. Detector counts are accumulated in a 2X8000 channel time analyzer system with 1 nsec channel width. A planned f1ight path of 180 m and an increase of the repetition rate from 20 kc at present to 200 kc is expected to provide further improvements of the spectrometer.

Worldwide about one million patients require treatment of stenosed coronary arteries annually. Often a tubular stainless steel mesh (stent) is implanted to mechanically support the injured vessel. Restenosis, an abundant complication (20%–30%) can be prevented, if the vessel is treated with ionizing radiation. Stents can deliver radiation if they are made radioactive. The radio isotope P32 is well suited when ion implanted. Radioactive ions sources require high efficiency to keep the radioactive inventory small. Reliability, ease of operation, and maintenance are mandatory. A small emittance is important to minimize losses during mass separation and beam transport. A 2.45 GHz ECR source was developed for the implantation of P32. The source consists of two coils for the axial and a permanent hexapole for the radial confinement. The microwaves are fed in radially by a loop connected to a silver plated brass tube surrounding the plasma chamber. The plasma chamber is made from Pyrex. Neutron activated phosphorus, containing 30 ppm P32, is introduced from the rear end on a rod. As support gas D2 is used. By this P+32 can be separated from (31PD)+. The extraction is done in two steps: 60 kV–30 kV–ground. Mass separation is accomplished by a double focusing 90° magnet (radius 500 mm). During four years of operation about 1000 radioactive stents per year have been provided for animal experiments and clinical trials. Only one maintenance to exchange the extraction system due to degradation of high voltage stability was required so far.