A method to correct differential nonlinearities in subranging analog-to-digital converters used for digital gamma-ray spectroscopy

The influence on $\gamma$-ray spectra of differential nonlinearities (DNL) in subranging, pipelined analog-to-digital converts (ADCs) used for digital $\gamma$-ray spectroscopy was investigated. The influence of the DNL error on the $\gamma$-ray spectra, depending on the input count-rate and the dynamic range has been investigated systematically. It turned out, that the DNL becomes more significant in $\gamma$-ray spectra with larger dynamic range of the spectroscopy system. An event-by-event offline correction algorithm was developed and tested extensively. This correction algorithm works especially well for high dynamic ranges

An advanced preamplifier for highly segmented germanium detectors

We present a fast low-noise hybrid charge-sensitive preamplifier for germanium position-sensitive gamma-ray detectors. In conjunction with a bulky 36-fold segmented detector it provided an excellent resolution of 1.71/1.77 keV fwhm on the 1.17/1.33 MeV 60Co lines. The preamplifier rise time, as measured at the test bench, is as fast as 7.5 ns, with a detector capacitance of 21 pF and with a 5 m 50 ohm twisted-pair cable connected at its output. The dynamic range of the preamplifier input stage is as large as 92 dB, ranging from 0.275 fC to 9.9 pC, i.e., from 5 keV to 180 MeV in terms of photon energy. On signals larger than 2 MeV a fast reset (about 10 MeV/us) is enforced to reduce the system dead time. An estimate of the amplitude of such large signals is derived from the reset time, still obtaining a high resolution. Using this technique we achieved an energy resolution of 0.3% at 16.7 MeV

Extending the dynamic range of nuclear pulse spectrometers

Using an innovative time-varying front-end electronics in conjunction with a bulky coaxial high-purity germanium detector, we were able to extend the range of the radionuclide spectra well beyond the analog to digital converter (ADC) saturation point. The electronics automatically conditions the signal for digital-filtering optimization if it is in the ADC voltage range and for time-over-threshold analysis if it exceeds the ADC range. A high spectroscopic resolution has been achieved in both operation ranges. An unprecedented wide energy range from 5 keV to 150 MeV of equivalent energy, or 90 dB, has been obtained using a single acquisition chain, while maintaining a high-energy resolution in the whole spectrum. For example, with an ADC range of 3 MeV a resolution has been obtained of 1.3/2.2 keV full width at half maximum on the 122/1332 keV gamma-ray lines of Co-57 and Co-60, and of <0.4% in the time-over-threshold region, or for energy deposits beyond 3 MeV. (C) 2008 American Institute of Physics

Search for proton emission of the isomeric 10+ state in 54 Ni

9 pags., 7 figs., 1 tab.Several experiments were conducted at the 10 MV Van-de-Graaff tandem accelerator at the Institute of Nuclear Physics, Cologne, to detect proton emission from the isomeric 6457-keV 10 state in Ni. Excitation functions for two fusion–evaporation reactions were measured to maximise the population of the rare two-neutron evaporation channel from a Ni compound nucleus. The search for delayed proton emission was based on the Si (Si , 2 n)Ni reaction at a beam energy of 70 MeV. For this reaction, a cross-section limit for the population of the 10 state in Ni and its proton-decay branch was determined to be σ< 22 nb.Open Access funding provided by Projekt DEAL. We would like to thank the accelerator staff at the University of Cologne for the efforts to deliver heavy-ion beams of excellent quality, as well as the Swedish Research Council (contract VR 2008-4240 and VR 2016- 3969) for financial support

Load carrying capacity of a heterogeneous surface bearing

It has been shown before that liquids can slip at a solid boundary, which prompted the idea that parallel-surfaces bearings can be achieved just by alternating slip and non-slip regions in the direction of fluid flow. The amount of slip at the wall depends on the surface tension at the liquid–solid interface, which in turn depends on the chemical state of the surface and its roughness. In the present study a heterogeneous surface was obtained by coating half of a circular glass disc with a coating repellant to glycerol. A rotating glass disc was placed at a known/calibrated distance and the gap was filled with glycerol. With the mobile surface moving from the direction of slip to non-slip region it can be theoretically shown that a pressure build up can be achieved. The pressure gradient in the two regions is constant, similar to that in a Rayleigh step bearing, with the maximum pressure at the separation line. The heterogeneous disc was placed on a holder supported by a load cell thus the force generated by this pressure increase can be measured accurately. Tests were carried out at different sliding speeds and gaps and the load carried was measured and subsequently compared with theoretical calculations. This allowed the slip coefficient to be evaluated

Integrative omics identifies conserved and pathogen-specific responses of sepsis-causing bacteria

Even in the setting of optimal resuscitation in high-income countries severe sepsis and septic shock have a mortality of 20–40%, with antibiotic resistance dramatically increasing this mortality risk. To develop a reference dataset enabling the identification of common bacterial targets for therapeutic intervention, we applied a standardized genomic, transcriptomic, proteomic and metabolomic technological framework to multiple clinical isolates of four sepsis-causing pathogens: Escherichia coli, Klebsiella pneumoniae species complex, Staphylococcus aureus and Streptococcus pyogenes. Exposure to human serum generated a sepsis molecular signature containing global increases in fatty acid and lipid biosynthesis and metabolism, consistent with cell envelope remodelling and nutrient adaptation for osmoprotection. In addition, acquisition of cholesterol was identified across the bacterial species. This detailed reference dataset has been established as an open resource to support discovery and translational research

Design and optimization of low-noise wide-bandwidth charge preamplifiers for high purity germanium detectors

Design criteria for low-noise wide-bandwidth charge-sensitive preamplifiers for highly-segmented HPGe detectors are presented. The attention is focused on the optimization of the preamplifier noise, long-term gain stability, and bandwidth. The charge-sensitive preamplifiers of AGATA, i.e., the Advanced GAmma Tracking Array detector for next generation nuclear physics experiments, have been designed, realized and optimized using the proposed techniques. The circuit, in conjunction with the detector, provided an Equivalent Noise Charge of 101 electrons r.m.s., a rise time of similar to 8.3 ns, no appreciable line shift in long term acquisitions, a dynamic range of as much as 92 dB. An analytical study of the circuit is made. Computer simulations and experimental results are shown and critically discussed

A Time-over-Threshold technique for wide dynamic range gamma-ray spectroscopy with the AGATA detector

Wide-range energy measurements have been carried out with an encapsulated 36-fold segmented germanium detector of AGATA (Advanced GAmma-ray Tracking Array). An unprecedented equivalent energy range of 5 keV to 180 MeV, or similar to 90 dB, has been obtained using a single acquisition chain, while maintaining a high energy resolution in the whole spectrum. For energies larger than 3 MeV the pulse-height is obtained with a Time-over-Threshold (ToT) technique. The measured resolution in all the tested range from 3 to 50 MeV is of <0.4%. The ToT technique has been demonstrated using a Am-241 + Be source with Ni target generating high-energy gamma photons by neutron capture reactions. A remarkable resolution of 0.21% has been obtained on the Ni spectrum line at the energy of 8.998 MeV