The current performance of all three AMS systems in operation at ETH Zurich, the 6MV HVEC EN-Tandem facility “TANDEM”, the 0.5MV NEC Pelletron “TANDY”, and the 0.2MV system “MICADAS” is summarized. ...Radionuclides routinely measured with these AMS systems include 10Be, 14C, 26Al, 36Cl, 41Ca, 129I and the actinides. The reference materials used for the normalization of the AMS measurements at the ETH Zurich AMS facilities are presented. This paper therefore is a comprehensive status report of all three AMS systems currently operated by the Laboratory of Ion Beam Physics (LIP) at ETH Zurich and documents their performance and operation parameters.
Stone tools stratified in alluvium and loess at Korolevo, western Ukraine, have been studied by several research groups
since the discovery of the site in the 1970s. Although Korolevo's importance to ...the European Palaeolithic is widely acknowledged, age constraints on the lowermost lithic artefacts have yet to be determined conclusively. Here, using two methods of burial dating with cosmogenic nuclides
, we report ages of 1.42 ± 0.10 million years and 1.42 ± 0.28 million years for the sedimentary unit that contains Mode-1-type lithic artefacts. Korolevo represents, to our knowledge, the earliest securely dated hominin presence in Europe, and bridges the spatial and temporal gap between the Caucasus (around 1.85-1.78 million years ago)
and southwestern Europe (around 1.2-1.1 million years ago)
. Our findings advance the hypothesis that Europe was colonized from the east, and our analysis of habitat suitability
suggests that early hominins exploited warm interglacial periods to disperse into higher latitudes and relatively continental sites-such as Korolevo-well before the Middle Pleistocene Transition.
Abstract
Isotopic ratios of radioactive releases into the environment are useful signatures for contamination source assessment. Uranium is known to behave conservatively in sea water so that a ratio ...of uranium trace isotopes may serve as a superior oceanographic tracer. Here we present data on the atomic
$$^{233}$$
233
U/
$$^{236}$$
236
U ratio analyzed in representative environmental samples finding ratios of (0.1–3.7)
$$\cdot$$
⋅
10
$$^{-2}$$
−
2
. The ratios detected in compartments of the environment affected by releases of nuclear power production or by weapons fallout differ by one order of magnitude. Significant amounts of
$$^{233}$$
233
U were only released in nuclear weapons fallout, either produced by fast neutron reactions or directly by
$$^{233}$$
233
U-fueled devices. This makes the
$$^{233}$$
233
U/
$$^{236}$$
236
U ratio a promising new fingerprint for radioactive emissions. Our findings indicate a higher release of
$$^{233}$$
233
U by nuclear weapons tests before the maximum of global fallout in 1963, setting constraints on the design of the nuclear weapons employed.
The potential of He stripping in heavy ion AMS Vockenhuber, C.; Alfimov, V.; Christl, M. ...
Nuclear instruments & methods in physics research. Section B, Beam interactions with materials and atoms,
January 2013, 2013-01-00, 20130101, Letnik:
294
Journal Article
Recenzirano
The use of helium as a stripper gas for Accelerator Mass Spectrometry (AMS) measurements of heavy ions is presented. At ion stripping energies of about 500keV and below we observe a significant ...increase of the mean charge state when using helium instead of other gases. Moreover, scattering losses are reduced with helium because of its lower mass compared to other commonly used stripper gases. Thus, highly efficient AMS measurements for 41Ca, 129I and 236U with transmissions through the accelerator in the range of 40–50% are now possible.
Search for beta-delayed proton emission from 11Be Riisager, K.; Borge, M. J. G.; Briz, J. A. ...
The European physical journal. A, Hadrons and nuclei,
2020/3, Letnik:
56, Številka:
3
Journal Article
Recenzirano
We report on an attempt to reproduce the observation of
β
-
-delayed proton emission from
11
Be through detection of the final state nucleus
10
Be with accelerator mass spectrometry. Twelve samples ...were collected at the ISOLDE facility at CERN at different separator settings, allowing tests of different sources of contamination to be carried out. The observed amounts of
10
Be per collected
11
Be rule out several contamination sources, but do not agree internally. Formation of BeH molecular ions in the ion source may explain our data, in which case an upper limit of the
β
p branching ratio of
2.2
×
10
-
6
can be derived.
Over-the-air (OTA) performance evaluation for wireless devices require electromagnetic field measurements in the far-field (FF). This is typically achieved by using one or multiple test probes to ...scan a sphere encompassing the device under test (DUT), which can be either set to transmit (Tx) or receive (Rx). Measurement data are usually collected in magnitude-only and near-field to FF transformations cannot be straightforwardly applied in a majority of test cases. In the case of large DUT, the active antenna in the device may not be located at the center of the measurement coordinate system, due to mechanical positioner or anechoic chamber constraints. Such an offset is known to introduce significant errors on assessed radiated quantities, which are mostly due to variations in the path length and the angular position of the apparent phase center of the Tx/Rx structure, with respect to the probe boresight direction. This article proposes a novel solution to this problem and introduces an algorithm to compensate errors from known antenna displacements within the coordinate system. This compensation applies to both OTA Tx and Rx cases. The accuracy of the identified solution is demonstrated through simulated and experimental results, using setups operating at 5G NR millimeter-wave frequencies.
In this study the first comprehensive dataset of 236U in the North Atlantic Ocean is presented. 236U/238U ratios and 236U concentrations are determined in about 70 seawater samples collected from 9 ...depth profiles along a transect through the Northwest Atlantic Ocean during the first two legs of the GEOTRACES cruise GA02 in 2010. The cruise track was designed to follow the path of the North Atlantic Deep Water (NADW) from its formation region to the deep parts of the western Atlantic Ocean basins. Our results show that there is a strong North to South and surface to deep ocean gradient spanning a broad range of 236U/238U, from (44±15)×10−12 to (1477±91)×10−12 that correlates well with the distribution of water masses in this region. All measured ratios are above the theoretical pre-anthropogenic levels of 10−13 to 10−14, showing that the whole transect is dominated by anthropogenic 236U. Based on the calculated 236U inventories the 236U inputs of global fallout and direct releases from nuclear reprocessing plants could be constrained to a range from 1000 to 1400kg and from 115 to 250kg of 236U, from the two sources, respectively. Our results show that the 236U/238U atomic ratio can be used as a marker of North Atlantic water masses: with high ratios (>1000×10−12) characterizing northern water masses (LSW and DSOW); and lowest ratios (50–400×10−12) corresponding to the increasing influence of AABW and AAIW.
93Zr (t1/2=1.6Ma) is mostly produced by the main s-process in low-to-intermediate mass AGB stars. Large uncertainty exists in the current 92Zr(n,γ)93Zr Maxwellian Average cross section. This could ...have significant impact on nucleosynthesis calculations. Large amounts of 93Zr are also produced in nuclear reactors and pose long-term environmental radioactivity. Hence, measurement of 93Zr by the AMS is important for both fields above. We report here on progress in the development of AMS method to measure 93Zr. Compared with 98MeV beam energy, Zr/Nb isobar position separation was improved using 155.2MeV beam energy and Gas-Filled Magnet. Energy loss measurement with increased beam energy inside the detector indicates that higher beam energy can improve isobar energy loss separation. A chemical procedure to reduce the Nb content in Zr samples has been developed and tested. It reduces the 93Nb content by a factor of 1000.
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