The cross section of the reaction 197Au(n,γ ) was measured with the time-of-flight technique at the n TOF
(neutron time-of-flight) facility in the unresolved resonance region between 5 and 400 keV ...using a pair of C6D6
(where D denotes 2H) liquid scintillators for the detection of prompt capture γ rays. The results with a total
uncertainty of 3.9%–6.7% for a resolution of 20 bins per energy decade show fair agreement with the Evaluated
Nuclear Data File Version B-VII.0 (ENDF/B-VII.0), which contains the standard evaluation. The Maxwellianaveraged
cross section (MACS) at 30 keV is in excellent agreement with the one according to the ENDF/B-VII.0
evaluation and 4.7% higher than the MACS measured independently by activation technique. Structures in the
cross section, which had also been reported earlier, have been interpreted as being due to clusters of resonances.
The neutron capture cross sections of the Zr isotopes have important implications in nuclear astrophysics and
for reactor design. The small cross section of the neutron magic nucleus 90Zr, which ...accounts for more than 50%
of natural zirconium represents one of the key isotopes for the stellar s-process, because it acts as a bottleneck
in the neutron capture chain between the Fe seed and the heavier isotopes. The same element, Zr, also is an
important component of the structural materials used in traditional and advanced nuclear reactors. The (n, ¿ )
cross section has been measured at CERN, using the n TOF spallation neutron source. In total, 45 resonances
could be resolved in the neutron energy range below 70 keV, 10 being observed for the first time thanks to the
high resolution and low backgrounds at n TOF. On average, the ¿ widths obtained in resonance analyses with
the R-matrix code SAMMY were 15% smaller than reported previously. By these results, the accuracy of the
Maxwellian averaged cross section for s-process calculations has been improved by more than a factor of 2.
Aims. This paper describes the Heterodyne Instrument for the Far-Infrared (HIFI) that was launched onboard ESA's Herschel Space Observatory in May 2009. Methods. The instrument is a set of 7 ...heterodyne receivers that are electronically tuneable, covering 480–1250 GHz with SIS mixers and the 1410–1910 GHz range with hot electron bolometer (HEB) mixers. The local oscillator (LO) subsystem comprises a Ka-band synthesizer followed by 14 chains of frequency multipliers and 2 chains for each frequency band. A pair of auto-correlators and a pair of acousto-optical spectrometers process the two IF signals from the dual-polarization, single-pixel front-ends to provide instantaneous frequency coverage of 2 × 4 GHz, with a set of resolutions (125 kHz to 1 MHz) that are better than 0.1 km s-1. Results. After a successful qualification and a pre-launch TB/TV test program, the flight instrument is now in-orbit and completed successfully the commissioning and performance verification phase. The in-orbit performance of the receivers matches the pre-launch sensitivities. We also report on the in-orbit performance of the receivers and some first results of HIFI's operations.
A series of neutron capture cross section measurements of interest to nuclear astrophysics
have been recently performed at n TOF, the neutron spallation source operating
at CERN. The low repetition ...frequency of the proton beam driver, the extremely high
instantaneous neutron flux, and the low background conditions in the experimental area
are optimal for capture cross section measurements on low-mass or radioactive samples.
An overview of the measurements performed during the two experimental campaigns in
2002 and 2003 is presented with special emphasis on the measurement of the capture cross
sections of the Os isotopes relevant for the cosmochronology based on the Re/Os clock.
Peer Reviewed
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