Measurement of the K S mean lifetime from π+π− and π0π0 decays using K L decays to determine the acceptance

A precision measurement of the K _S mean lifetime has been performed by comparing, in the same experimental setup, the distributions of two-pion decays of neutral kaons produced by high energy proton-beryllium interactions in two targets at a relative distance variable between 112 and 160 m. The value obtained combining the results from π⁺π^? and π⁰π⁰ decays is τ_s = (0.8971 ± 0.0021) 10^?10 s.     

Stochastic radiotherapy appointment scheduling

Central European Journal of Operations Research - When scheduling the starting times for treatment appointments of patients in hospitals or outpatient clinics such as radiotherapy centers,...     

Multiple trapping sites for potassium atoms in argon matrices

Argon crystals were dopes with 0.2 ppm of ⁴¹K through the nuclear reaction ⁴⁰Ar(n, β^-)⁴¹K. The X-band electron spin resonance spectrum of ⁴¹K was observed. The recorded spectra clearly show the existence of different trapping sites for potassium in argon. Zero-field hyperfine splittings and g-values of potassium on these sites are determined.     

Versuche zur Synthese des Cytisins. Dehydrierung von Tetrahydro-cytisin zu Cytisin

Zusammenfassung Die Dehydrierung von Tetrahydro-cytisin zu Cytisin mit Palladium verläuft glatt, wenn man die Iminogruppe durch Acetylierung schützt. Durch Erhitzen des N-Acetyl-tetrahydrocytisins mit Pd-Mohr bei 280° erhält man so in guter Ausbeute N-Acetyl-cytisin und daraus durch Abspaltung der Acetyl-gruppe mit Salzsäure das Cytisin.     

High-dose reactor irradiation of iron at 4.6 K: Dose and recovery curves of electrical resistivity

The increase of residual resistivity ?_o of iron during reactor irradiation at 4.6 K has been studied up to a fast neutron dose as high as 1.07 × 10¹⁹ n/cm². The outstanding result is a negative curvature of the differentiated dose curve which probably has to do with the ferromagnetic nature of Fe. Isochronal annealing showed pronounced stages I and II but only little recovery between 300 and 400 K (formerly called stage III).     

High magnetic field effects on shallow and deep impurities in semiconductors

It is shown that high magnetic fields provide an efficient means to distinguish strongly localized impurity states from shallow, effective-mass-like states, irrespective of the binding energies of these states. The ground and excited states of a simple model Hamiltonian for shallow and deep impurities are analyzed for arbitrary magnetic field strengths.     

Imaging and quality assessment of high-harmonic focal spots

We present a direct method of studying the focusability of an intense, short-pulse extreme-ultraviolet (XUV) beam obtained by high-harmonic generation. We perform near-field imaging of the focal spot of five high-harmonic orders strongly focused by a broadband toroidal mirror. To visualize the focal spot directly, we image the fluorescence induced by an XUV beam on a cerium-doped YAG crystal on a visible CCD camera. We can thus measure the harmonic spot size on a single image, together with the Strehl ratio, to evaluate the quality of focusing. Such techniques should become instrumental in optimizing the focusing conditions and reaching intensities required for exploring attosecond nonlinear optics in the XUV range.     

Measurement of stored energy of KCl after 4·6°K reactor irradiation

Five KCl single crystals were irradiated at 4·6°K in the core of the Munich Nuclear Reactor for periods of 100 sec, 10 min, 1 hr or 10 hr, respectively. After irradiation the stored energy of the samples was measured in a differential-heat-flow calorimeter at two different heating rates: 0·29 and 1·1°K/min. At 0·29°K/min peaks of stored energy release were resolved at 21°K, near 27·5°K, at 32·5°K, at 42·5°K and near 50°K. An attempt was made to evaluate the corresponding activation energies using two different methods (see Table 1 in the text). The annealing stages at 21 and 32·5°K correspond to first order kinetics. The annealing stages at 42·5 and near 50°K are not of first order. A similar experiment was performed on KBr single crystals and is reported in the preceding paper. The results are compared with annealing studies on low temperature X-irradiated KCl and KBr crystals. From both our experiments it follows that also during reactor irradiation at 4·6°K ionization mechanisms of defect production should be responsible for the four observed low temperature recovery peaks; only defect recovery at higher temperatures may be at least partially explained by recombination of collision produced defects, i.e. the typical neutron irradiation effect as it takes place in metals.