[en] A description is given of a bent-crystal spectrometer for pionic X-rays. The instrument is of the modified DuMond type and makes use of a combined π-production-X-ray target. It is situated in a 20 μA, 590 MeV proton beam at SIN. Combination of high mechanical precesion and a laser interferometer system makes it possible to measure wavelength ratios with a precision of 1-2 parts per million. (orig.)

[en] The Nucleon Area (NA) at the Paul-Scherrer-Institut (PSI) was built as a multi-purpose facility for experiments with polarized or unpolarized protons or neutrons. For both kinds of nucleons the available energy ranges from about 100 MeV up to a maximum of 590 MeV. This article presents technical details of the layout of the nucleon beams and areas, the experimental arrangements, and the equipment employed. An experimental program on neutron-proton scattering is presently carried out using the NA facility at PSI. We put special emphasis on the polarized neutron beam and its use to measure the neutron-proton elastic scattering. (orig.)

[en] We describe the design, construction and performance of the PIBETA detector built for the precise measurement of the branching ratio of pion beta decay, π⁺→π⁰e⁺ν_e, at the Paul Scherrer Institute. The central part of the detector is a 240-module spherical pure CsI calorimeter covering ∼3π sr solid angle. The calorimeter is supplemented with an active collimator/beam degrader system, an active segmented plastic target, a pair of low-mass cylindrical wire chambers and a 20-element cylindrical plastic scintillator hodoscope. The whole detector system is housed inside a temperature-controlled lead brick enclosure, which in turn is lined with cosmic muon plastic veto counters. Commissioning and calibration data were taken during two 3-month beam periods in 1999/2000 with π⁺ stopping rates between 1.3·10³ π⁺/s and 1.3·10⁶ π⁺/s. We examine the timing, energy and angular detector resolution for photons, positrons and protons in the energy range of 5-150 MeV, as well as the response of the detector to cosmic muons. We illustrate the detector signatures for the assorted rare pion and muon decays and their associated backgrounds

[en] We have examined the suitability of lead (Pb)/tin (Sn) alloys with atomic ratios between 4:1 and 12:1 for use as a spallation target material for the PSI spallation ultracold neutron source. The measured corrosion rate with distilled water, R_c<6x10^-5cm/year, is more than a factor of 80, less than for normal Pb; this corrosion rate is satisfactory. Microscopic investigations of the surface after the exposure to water revealed no visual changes. Small angle neutron scattering showed that the alloy is mechanically stable under thermal cycling. An experimental simulation of a water-cooled spallation neutron target made of Pb/Sn pebbles with a filling factor of 60% was investigated; the pulsed proton beam was simulated using hot and cold water in the target 'cooling' circuit. With realistic operational parameters for the cooling circuit, serious deformation of the PbSn pebbles occurred which finally blocked the cooling circuit. The Pb/Sn alloys solve the corrosion problem but its mechanical properties are inadequate leading to too short a lifetime to be practical in the PSI spallation source