A setup for soft proton irradiation of X-ray detectors for future astronomical space missions

Protons that are trapped in the Earth's magnetic field are one of the main threats to astronomical X-ray observatories. Soft protons, in the range from tens of keV up to a few MeV, impinging on silicon X-ray detectors can lead to a significant degradation of the detector performance. Especially in low earth orbits an enhancement of the soft proton flux has been found. A setup to irradiate detectors with soft protons has been constructed at the Van-de-Graaff accelerator of the Physikalisches Institut of the University of T\"ubingen. Key advantages are a high flux uniformity over a large area, to enable irradiations of large detectors, and a monitoring system for the applied fluence, the beam uniformity, and the spectrum, that allows testing of detector prototypes in early development phases, when readout electronics are not yet available. Two irradiation campaigns have been performed so far with this setup. The irradiated detectors are silicon drift detectors, designated for the use on-board the LOFT space mission. This paper gives a description of the experimental setup and the associated monitoring system.Comment: 20 pages, 10 figures, 4 table

Ketene acetal metallocene complexes : Crystal structure of (C 5 H 5) 2 Ti(Cl)OC(OCH 3)=C(CH 3) 2

Titanocene and zirconocene ketene acetal derivatives have been prepared by reaction of the respective metallocene dichloride with the lithium enolate of isobutyric acid methyl ester. The crystal structure of (C5H5)2Ti(Cl)OC(OCH3)=C(CH3) is reported

ansa-metallocene derivatives : XXIII. Aryl-substituted titanocene and zirconocene complexes with interannular tetramethylethano- or dimethylsilano-bridges. Crystal structures of representative examples

Titanocene and zirconocene complexes with a phenyl or 1-naphthyl substituent in one β-position of each C5-ring ligand and with an interannular tetramethylethano- or dimethylsilano-bridge have been prepared. Racemic complex isomers, which are formed together with varying amounts of their meso isomers, were separated from the latter and characterised by 1H NMR spectroscopy and X-ray crystallographic studies

ansa-metallocene derivatives : XXV. Synthesis, crystal structure and reactions of a tetramethylethano-bridged vanadocene dichloride, (CH₃)₄C₂(C₅H₄)₂VCl₂

The tetramethylethano-bridged vanadocene complex (CH3)4C2(C5H4)2VCl2 has been made in two ways: (i) from VCl3·3THF by reaction with (CH3)4C2(C5H4MgCl·2THF)2 in THF and subsequent oxidation with PCl3, and (ii) from VCl4·2THF by reaction with (CH3)4C2(C5H4Li)2 or with (CH3)4C2(C5H4MgCl·2THF)2 in a toluene/dimethoxyethane mixture. Its crystal structure is in accordance with expectations. Reduction of (CH3)4C2(C5H4)2VCl2 with tetrakis(dimethylamino)ethene in toluene or with LiAlH4 in THF yields the monochloride (CH3)4C2(C5H4)2VCl; from this VIII compound cationic complexes (CH3)4C2(C5H4)2VL2+ with L = CO or CNtBu are readily obtained by ligand exchange. 1H NMR signals of these diamagnetic complexes have been assigned to H atoms in α and β C5-ring positions by use of selective nuclear Overhauser effects. The ring-bridged VII complex (CH3)4C2(C5H4)2V could not be prepared. Cyclovoltammetry studies indicate that (in contrast to its unbridged counterpart (C5H5)2V) this VII complex decays within seconds after its formation by electrochemical reduction of its chloro derivatives