68 research outputs found
Frequency-domain multiplexing of SNSPDs with tunable superconducting resonators
This work culminates in a demonstration of an alternative Frequency Domain
Multiplexing (FDM) scheme for Superconducting Nanowire Single-Photon Detectors
(SNSPDs) using the Kinetic inductance Parametric UP-converter (KPUP) made out
of NbTiN. There are multiple multiplexing architectures for SNSPDs that are
already in use, but FDM could prove superior in applications where the
operational bias currents are very low, especially for mid- and far-infrared
SNSPDs. Previous FDM schemes integrated the SNSPD within the resonator, while
in this work we use an external resonator, which gives more flexibility to
optimize the SNSPD architecture. The KPUP is a DC-biased superconducting
resonator in which a nanowire is used as its inductive element to enable
sensitivity to current perturbations. When coupled to an SNSPD, the KPUP can be
used to read out current pulses on the few A scale. The KPUP is made out
of NbTiN, which has high non-linear kinetic inductance for increased
sensitivity at higher current bias and high operating temperature. Meanwhile,
the SNSPD is made from WSi, which is a popular material for broadband SNSPDs.
To read out the KPUP and SNSPD array, a software-defined radio platform and a
graphics processing unit are used. Frequency Domain Multiplexed SNSPDs have
applications in astronomy, remote sensing, exoplanet science, dark matter
detection, and quantum sensing
Momentum Distribution in Nuclear Matter and Finite Nuclei
A simple method is presented to evaluate the effects of short-range
correlations on the momentum distribution of nucleons in nuclear matter within
the framework of the Green's function approach. The method provides a very
efficient representation of the single-particle Green's function for a
correlated system. The reliability of this method is established by comparing
its results to those obtained in more elaborate calculations. The sensitivity
of the momentum distribution on the nucleon-nucleon interaction and the nuclear
density is studied. The momentum distributions of nucleons in finite nuclei are
derived from those in nuclear matter using a local-density approximation. These
results are compared to those obtained directly for light nuclei like .Comment: 17 pages REVTeX, 10 figures ps files adde
Momentum distribution in nuclear matter and finite nuclei
A simple method is presented to evaluate the effects of short-range correlations on the momentum distribution of nucleons in nuclear matter within the framework of the Greens function approach. The method provides a very efficient representation of the single-particle Greens function for a correlated system. The reliability of this method is established by comparing its results to those obtained in more elaborate calculations. The sensitivity of the momentum distribution on the nucleon-nucleon interaction and the nuclear density is studied. The momentum distributions of nucleons in finite nuclei are derived from those in nuclear matter using a local-density approximation. These results are compared to those obtained directly for light nuclei like 16O
Collaborative exercise on the use of FISH chromosome painting for retrospective biodosimetry of Mayak nuclear-industrial personnel.
PURPOSE: To investigate within the framework of a multilaboratory study the suitability of FISH chromosome painting to measure so-called stable translocations in peripheral lymphocytes of Mayak nuclear-industrial workers (from the Southern Urals) and their use for retrospective biodosimetry. MATERIALS AND METHODS: Chromosime analyses were carried out from 69 workers who had received protracted occupational radiation exposures (0.012-6.065 Gy) up to approximately 40 years before blood sampling. Twenty-one unexposed people living in the same area were controls. A multicolour FISH-painting protocol with the target chromosomes 1, 4 and 8 simultaneously with a pancentromeric probe was used to score potentially transmissible chromosome-type aberrations (reciprocal translocations 2B and related 'one-way' patterns I-III according to the S&S classification). RESULTS: Individual biodosimetry estimates were obtained in terms of these potentially long-term surviving aberration types based on the linear component of a low dose-rate gamma-ray calibration curve produced using identical staining and scoring protocols. For comparison, the workers personal and total background doses were converted to red bone marrow doses. The estimated doses were mainly lower than would be predicted by the calibration curve, particularly at accumulated higher dose levels. CONCLUSIONS: Owing to the limited life-time of circulating T-lymphocytes, the long-term persistence of translocations in vivo requires the assumption of a clonal repopulation of these naturally senescing cells from the haemopoietic stem cell compartments. Obviously such a replacement cannot be fully achieved, leading to a temporal decline even of the yield of transmissible aberrations types. Assuming further a highly selective capacity of stem cells against any type of chromosomal damage and the fact that one must rely on partial genome findings, the potential of FISH chromosome painting for retrospective dose reconstruction is probably limited to a decade or so after high-level protracted radiation exposure
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