10 research outputs found
Design, Commissioning and Performance of the PIBETA Detector at PSI
We describe the design, construction and performance of the PIBETA detector
built for the precise measurement of the branching ratio of pion beta decay,
pi+ -> pi0 e+ nu, at the Paul Scherrer Institute. The central part of the
detector is a 240-module spherical pure CsI calorimeter covering 3*pi 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 three-month beam periods in
1999/2000 with pi+ stopping rates between 1.3*E3 pi+/s and 1.3*E6 pi+/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.Comment: 117 pages, 48 Postscript figures, 5 tables, Elsevier LaTeX, submitted
to Nucl. Instrum. Meth.
Udoteacean green algae from the paleozoic of graz/Austria (Barrandei Limestone, Eifelian)
Coral-rich bioconstructions in the Viséan (late Mississippian) of Southern Wales (Gower Peninsula, UK)
Heliolitid corals and their competitors: a case study from the Wellin patch reefs, Middle Devonian, Belgium
peer reviewedWellin patch reefs are small Upper Eifelian build?ups within the fine?grained argillaceous limestone of the Hanonet Formation. Whereas the reefs themselves are not well exposed, their fossil assemblage is accessible in the hills near the town of Wellin, approximately 40xA0km SE of Dinant in Belgium. It is especially rich in massive stromatoporoids, heliolitids and other tabulate corals. They exhibit predominantly domical and bulbous morphologies. This paper focuses primarily on the palaeoautoecology of the heliolitid corals and their relationships with other organisms. Cases of mutual overgrowth between heliolitids, other corals and stromatoporids suggest a high degree of competition for space on the reefs, possibly related to the scarcity of hard substrates. Coral and stromatoporoid growth forms, as well as the prevalence of micritic matrix, point to a relatively low energy environment. However, abundant growth interruption surfaces, sediment intercalations and rejuvenations of corals suggest episodically increased hydrodynamic regime and sediment supply. It is inferred that the patch reefs developed in a relatively shallow environment, where the reefal assemblage was regularly affected by storms. Heliolitids exhibited high sediment tolerance and relied on passive sediment removal for survival. They also could regenerate effectively and commonly overgrew their epibionts, after the colony’s growth was hampered by the sediment. This is recorded in extremely abundant growth interruption surfaces, which allow the analysis of the impact of sediment influxes on the heliolitid corals. ? 2021 Lethaia Foundation. Published by John Wiley & Sons Lt