No abstract available

No abstract available

No abstract available

No abstract available

No abstract available

[en] A laser interferometer for precise angle measurements has been developed for the crystal spectrometer of the University of Fribourg. The angular range is +-20⁰. The apparatus has been tested with five γ-ray transitions in the decay of ¹⁶⁹Yb. The angular precision is shown to vary between 5 and 29 msec of arc in the tested range of +-10⁰. The relative precision obtained for the 307 keV transition is 0.24 ppm. (Auth.)

[en] Under some simplifying assumptions regarding the diffraction pattern, the line profile of a reflex due to a monochromatic line observed with a curved crystal spectrometer in an extended source and crystal geometry is studied by analytical and numerical methods. It is shown how some parameters produce line asymmetries and shifts of the reflex center of gravity. The magnitude of the corrections which need to be applied for the calibration of γ-ray energies is determined. (Auth.)

[en] In order to increase the irradiation capacity of the reactor, an additional pneumatic transfer system is planned. It consists of four rabbit tubes, which are installed in the original beam port R 3, and it allows the irradiation of four capsules ('rabbits') simultaneously. Two of these tubes are provided for standard irradiations. This so-called 'slow rabbit system' is operated in a closed circuit with CO₂, as propellant gas in order to avoid release of AR-41. A forced convection cooling circuit enables the long-time irradiation of samples up to 50 g of weight without exceeding temperatures above 80 deg. C. The other two tubes are considered for a fast rabbit system, which is operated with compressed nitrogen (8 atm) as propellant. Since the loading station is situated near the reactor shield, a time of flight below 200 ms is obtained, so that investigations of very short-lived isotopes are possible. (author)

[en] A probabilistic fracture mechanics (PFM) model that is specific to the Accelerator Production of Tritium (APT) helium tubes was developed. The model performs Monte Carlo analyses of potential failure modes caused by cyclic stresses generated by beam trips and de-pressurizations from normal operation, coupled with material aging due to irradiation. Dominant failure probabilities are due to crack through-growth while brittle fracture and ductile tearing have lower probability. Failure mechanisms of global plastic collapse and buckling or crack initiation mechanisms of fatigue or local fracture (upon loss of ductility) have negligible probability. For the population of (7,311) tubes in the APT blanket, the worst-case, annual probability of one tube failing is 3 percent. The probability of 2 or more failures is substantially lower; therefore, unavailability impacts are driven by single failure. The average annual loss of production (unavailability) is below about 0.2 percent. Helium outflow and water inflow rates were characterized for the failures. (authors)

[en] Spectra of positive pions from the process n + p → π⁺ + n + n have been measured for incident neutron energies from 470 MeV to 590 MeV and for laboratory angles up to 20sup(O). The rather broad pion energy spectra and the pronounced anisotropy of the differential cross sections both indicate an appreciable non-resonant, isoscalar (T = 0) contribution to the pion production. (orig.)