DTS-100G — a versatile heterogeneous MPSoC board for cryogenic sensor readout

Heterogeneous devices such as the Multi-Processor System-on-Chip (MPSoC) from Xilinx are extremely valuable in custom instrumentation systems. This contribution presents the joint development of a heterogeneous MPSoC board called DTS-100G by DESY and KIT. The board is built around a Xilinx Zynq Ultrascale+ chip offering all available high-speed transceivers using QSFP28, 28 Gbps FireFly, FMC, and FMC+ interfaces. The board is not designed for a particular application, but can be used as a generic DAQ platform for a variety of physics experiments. The DTS-100G board was successfully developed, built and commissioned. ECHo-100k is the first experiment which will employ the board. This contribution shows the system architecture and explains how the DTS-100G board is a crucial component in the DAQ chain

The zonal currents and transports at 35°W in the tropical Atlantic

The total of 13 existing cross-equatorial shipboard current profiling sections taken during the WOCE period between 1990 and 2002 along 35°W are used to determine the mean meridional structure of the zonal top-to-bottom circulation between the Brazilian coast, near 5°S, and 5°N and to estimate mean transports of the individual identified shallow, intermediate and deep current branches. One of the results is that, on the equator, a mean westward Equatorial Intermediate Current below the Equatorial Undercurrent exists

The MBE growth and optimization of high performance terahertz frequency quantum cascade lasers

The technique of molecular beam epitaxy has recently been used to demonstrate the growth of terahertz frequency GaAs/AlGaAs quantum cascade lasers (QCL) with Watt-level optical output powers. In this paper, we discuss the critical importance of achieving accurate layer thicknesses and alloy compositions during growth, and demonstrate that precise growth control as well as run-to-run growth reproducibility is possible. We also discuss the importance of minimizing background doping level in maximizing QCL performance. By selecting high-performance active region designs, and optimizing the injection doping level and device fabrication, we demonstrate total optical (two-facet) output powers as high as 1.56 W

The shallow and deep western boundary circulation of the South Atlantic at 5-11°S

Repeated shipboard observation sections across the boundary flow off northeastern Brazil as well as acoustic Doppler current profiler (ADCP) and current-meter records from a moored boundary array deployed during 2000–04 near 11°S are analyzed here for both the northward warm water flow by the North Brazil Undercurrent (NBUC) above approximately 1100 m and the southward flow of North Atlantic Deep Water (NADW) underneath. At 5°S, the mean from nine sections yields an NBUC transport of 26.5 ± 3.7 Sv (Sv ≡ 106 m3 s−1) along the boundary; at 11°S the mean NBUC transport from five sections is 25.4 ± 7.4 Sv, confirming that the NBUC is already well developed at 11°S. At both latitudes a persistent offshore southward recirculation between 200- and 1100-m depth reduces the net northward warm water flow through the 5°S section (west of 31.5°W) to 22.1 ± 5.3 Sv and through the 11°S section to 21.7 ± 4.1 Sv (west of 32.0°W). The 4-yr-long NBUC transport time series from 11°S yields a seasonal cycle of 2.5 Sv amplitude with its northward maximum in July. Interannual NBUC transport variations are small, varying only by ±1.2 Sv during the four years, with no detectable trend. The southward flow of NADW within the deep western boundary current at 5°S is 25.5 ± 8.3 Sv with an offshore northward recirculation, yielding a nine-section mean of 20.3 ± 10.1 Sv west of 31.5°W. For Antarctic Bottom Water, a net northward flow of 4.4 ± 3.0 Sv is determined at 5°S. For the 11°S section, the moored array data show a pronounced energy maximum at 60–70-day period in the NADW depth range, which was identified in related work as deep eddies translating southward along the boundary. Based on a kinematic eddy model fit to the first half of the moored time series, the mean NADW transfer by the deep eddies at 11°S was estimated to be about 17 Sv. Given the large interannual variability of the deep near-boundary transport time series, which ranged from 14 to 24 Sv, the 11°S mean was considered to be not distinguishable from the mean at 5°

Ice platelets below Weddell Sea landfast sea ice

Basal melt of ice shelves may lead to an accumulation of disc-shaped ice platelets underneath nearby sea ice, to form a sub-ice platelet layer. Here we present the seasonal cycle of sea ice attached to the Ekström Ice Shelf, Antarctica, and the underlying platelet layer in 2012. Ice platelets emerged from the cavity and interacted with the fast-ice cover of Atka Bay as early as June. Episodic accumulations throughout winter and spring led to an average platelet-layer thickness of 4m by December 2012, with local maxima of up to 10 m. The additional buoyancy partly prevented surface flooding and snow-ice formation, despite a thick snow cover. Subsequent thinning of the platelet layer from December onwards was associated with an inflow of warm surface water. The combination of model studies with observed fast-ice thickness revealed an average ice-volume fraction in the platelet layer of 0.25+-0.1. We found that nearly half of the combined solid sea-ice and ice-platelet volume in this area is generated by heat transfer to the ocean rather than to the atmosphere. The total ice-platelet volume underlying Atka Bay fast ice was equivalent to more than one-fifth of the annual basal melt volume under the Ekström Ice Shelf

Oxygen tongues and zonal currents in the equatorial Atlantic

Equatorial zonal currents and associated oxygen distributions are studied using shipboard hydrographic data, trajectories from isopycnic floats drifting at about 300 m depth, and velocity time series from the upper 1100 m obtained at two equatorial moorings located at 35°W and 23°W. Mean profiles of zonal velocity measured by moored acoustic Doppler current profilers yielded a westward flowing Equatorial Intermediate Current (EIC) below the Equatorial Undercurrent (EUC) at both locations. The EIC consists of two westward current cores at about 250 and 450 m. The upper core of the EIC deepens by about 30 m from 23°W, where it has a mean velocity of 6 ± 2 cm s−1, to 35°W, where the mean is 5 ± 3 cm s−1. The lower core of the EIC is about twice as strong with 12 ± 1 cm s−1 at 23°W and 9 ± 2 cm s−1 at 35°W. The flow below the EUC is characterized by substantial interannual variability. From May to December 2005 a strong, zonally coherent eastward jet occurred at 300 to 350 m depth, found to be an expression of shallow stacked jets superimposed on the mean EIC. Shipboard hydrographic observations in June–July 2006 revealed the existence of a high‐oxygen tongue that can be traced from 35°W to 10°W in the depth range of the eastward jet prevailing during the preceding year. On the basis of an advection‐diffusion balance, it is suggested that the oxygen decrease from 35°W to 10°W within the oxygen tongue is mainly balanced by lateral eddy diffusivity and oxygen consumption, with diapycnal turbulent diffusivity playing only a minor role

Tendencies, variability and persistence of sea surface temperature anomalies

Quantifying global trends and variability in sea surface temperature (SST) is of fundamental importance to understanding changes in the Earth’s climate. One approach to observing SST is via remote sensing. Here we use a 37-year gap-filled, daily-mean analysis of satellite SSTs to quantify SST trends, variability and persistence between 1981-2018. The global mean warming trend is 0.08 K per decade globally, with 95 % of local trends being between -0.1 K and +0.35 K. Excluding perennial sea-ice regions, the mean warming trend is 0.11 K per decade. After removing the long-term trend we calculate the SST power spectra over different time periods. The maximum variance in the SST power spectra in the equatorial Pacific is 1.9 K2 on 1-5 year timescales, dominated by ENSO processes. In western boundary currents characterised by an intense mesoscale activity, SST power on sub-annual timescales dominates, with a maximum variance of 4.9 K2. Persistence timescales tend to be shorter in the summer hemisphere due to the shallower mixed layer. The median short-term persistence length is 11-14 days, found over 71-79 % of the global ocean area, with seasonal variations. The mean global correlation between monthly SST anomalies with a three-month time-lag is 0.35, with statistically significant correlations over 54.0 % of the global oceans, and notably in the northern and equatorial Pacific, and the sub-polar gyre south of Greenland. At six months, the mean global SST anomaly correlation falls to 0.18. The satellite data record enables the detailed characterisation of temporal changes in SST over almost four decades