1,320 research outputs found
Antenna pattern shaping, sensing, and steering study Final report
Design of steerable satellite antenna with beam pattern sensing syste
A stationary impulse-radar system for autonomous deployment in cold and temperate environments
L. Mingo acknowledges the SR&ED Tax Incentive Program of the CRA for offsetting some R&D costs of the sIPR. G. Flowers and D. Bigelow are grateful to NSERC, CFI, CSA, NSTP, PCSP and SFU for funding, Kluane First Nation, Yukon Government and Parks Canada for access to Yukon field sites and S. Williams, L. Goodwin, A. Pulwicki, J. Crompton,F. Beaud and Canadian astronaut D. Saint-Jacques for support and field assistance. C. Schoof and C. Rada provided time-lapse imagery and 2017 water-pressure data. A. Crawford and D. Mueller acknowledge funding from NSERC, Transport Canada, PKC/NSTP and the Garfield Weston Foundation, as well as support from Arctic Net, the CCGS Amundsen crew and pilots O. Talbot, A. Roy and G Carpentier.Stationary ice-penetrating radar (sIPR) systems can be used to monitor temporal changes in electromagnetically sensitive properties of glaciers and ice sheets. We describe a system intended for autonomous operation in remote glacial environments, and document its performance during deployments in cold and temperate settings. The design is patterned after an existing impulse radar system, with the addition of a fibre-optic link and timing module to control transmitter pulses, a micro-UPS (uninterruptable power supply) to prevent uncontrolled system shutdown and a customized satellite telemetry scheme. Various implementations of the sIPR were deployed on the Kaskawulsh Glacier near an ice-marginal lake in Yukon, Canada, for 44–77 days in summers 2014, 2015 and 2017. Pronounced perturbations to englacial radiostratigraphy were observed commensurate with lake filling and drainage, and are interpreted as changes in englacial water storage. Another sIPR was deployed in 2015–2016 on ice island PII-A-1-f, which originated from the Petermann Glacier in northwest Greenland. This system operated autonomously for almost a year during which changes in thickness of the ice column were clearly detected.Publisher PDFPeer reviewe
Solvent extraction studies of coprocessing flowsheets: Results from Campaign 6 of the Solvent Extraction Test Facility (SETF)
A series of five solvent extraction tests were made in the Solvent Extraction Test Facility (SETF) during Campaign 6. Each test used a coprocessing flowsheet that included coextraction-coscrubbing of the heavy metals followed by partial partitioning of the uranium and plutonium into separate uranium and uranium-plutonium products. The separation of the uranium and plutonium was aided by the addition of HNO{sub 2} to the organic backscrub stream. Two of these tests compared the performance of the traditional Purex solvent, tri-n-butyl phosphate (TBP), with a potential replacement, tri-2-ethylhexyl phosphate (TEHP). The remaining three tests were made with a chemically-degraded TBP solvent to compare the effectiveness of two solvent cleanup methods - treatment with silica gel or scrubbing with sodium carbonate and water
Solvent extraction studies of coprocessing flowsheets: results from Campaign 5 of the Solvent Extraction Test Facility (SETF)
In Campaign 5, fast breeder reactor (FBR) fuel [average burnup {similar_to}2.6 TJ/kg ({similar_to}30,000 MWd/t)] was processed for the first time. Operations in a single extraction cycle with 30% TBP-NPH were satisfactory with low heavy-metal losses (< 0.02%) and high decontamination factors (DFs > 1000) for all fission products except {sup 95}Zr, which exhibited moderate DFs (180 and 750, respectively, in two runs). The use of a split scrub stream (0.5 M and 3 M HNO{sub 3}) vs a single scrub stream (3 M HNO{sub 3}) resulted in the higher DF. An extractant backscrubbing stream was not needed to produce partially partitioned uranium-plutonium products containing 30 to 35% plutonium when processing the core FBR fuel (22% Pu). The necessary enrichment factor ({similar_to}1.5) was attained by maintaining the temperature at 25 to 30{sup 0}C in partial partitioning and adjusting the relative flow rates of the aqueous and organic phases. The plutonium recovery in the two runs ({similar_to}400 g) was purified by anion exchange and converted to PuO{sub 2} for fuel refabrication studies. 8 references, 7 figures, 6 tables
Observation of anomalous spin-state segregation in a trapped ultra-cold vapor
We observe counter-intuitive spin segregation in an inhomogeneous sample of
ultra-cold, non-condensed Rubidium atoms in a magnetic trap. We use spatially
selective microwave spectroscopy to verify a model that accounts for the
differential forces on two internal spin states. In any simple understanding of
the cloud dynamics, the forces are far too small to account for the dramatic
transient spin polarizations observed. The underlying mechanism remains to be
elucidated.Comment: 5 pages, 3 figure
From nonwetting to prewetting: the asymptotic behavior of 4He drops on alkali substrates
We investigate the spreading of 4He droplets on alkali surfaces at zero
temperature, within the frame of Finite Range Density Functional theory. The
equilibrium configurations of several 4He_N clusters and their asymptotic trend
with increasing particle number N, which can be traced to the wetting behavior
of the quantum fluid, are examined for nanoscopic droplets. We discuss the size
effects, inferring that the asymptotic properties of large droplets correspond
to those of the prewetting film
Transverse Fresnel-Fizeau drag effects in strongly dispersive media
A light beam normally incident upon an uniformly moving dielectric medium is
in general subject to bendings due to a transverse Fresnel-Fizeau light drag
effect. In conventional dielectrics, the magnitude of this bending effect is
very small and hard to detect. Yet, it can be dramatically enhanced in strongly
dispersive media where slow group velocities in the m/s range have been
recently observed taking advantage of the electromagnetically induced
transparency (EIT) effect. In addition to the usual downstream drag that takes
place for positive group velocities, we predict a significant anomalous
upstream drag to occur for small and negative group velocities. Furthermore,
for sufficiently fast speeds of the medium, higher order dispersion terms are
found to play an important role and to be responsible for peculiar effects such
as light propagation along curved paths and the restoration of the spatial
coherence of an incident noisy beam. The physics underlying this new class of
slow-light effects is thoroughly discussed
Calculation of the interspecies s-wave scattering length in an ultracold Na-Rb vapor
We report the calculation of the interspecies scattering length for the
sodium-rubidium (Na-Rb) system. We present improved hybrid potentials for the
singlet and triplet ground states of the NaRb
molecule, and calculate the singlet and triplet scattering lengths and
for the isotopomers NaRb and NaRb. Using
these values, we assess the prospects for producing a stable two-species
Bose-Einstein condensate in the Na-Rb system.Comment: v2: report correct units in Table captions, fix error in conclusions
for NaRb TBEC. Otherwise, more concise presentation, typos
fixed. 6 pages, 1 figur
Solvent extraction studies of coprocessing flowsheets: results from campaigns 3 and 4 of the Solvent-Extraction Test Facility (SETF)
Experiments on tri-n-butyl phosphate solvent extraction of uranium and plutonium at full activity levels (Campaigns 3 and 4) were conducted in the Solvent Extraction Test Facility (SETF), located in one of the heavily shielded cells of the Transuranium Processing Plant. The primary objectives were: (1) to demonstrate and evaluate the first two cycles of the Hot Engineering Facility flowsheets (codecontamination and partial partitioning), and (2) to investigate and evaluate the use of HNO{sub 2} as the reductant for tetravalent plutonium during reductive stripping operations. Secondary objectives were to determine the solvent extraction behavior of feed solutions prepared by dissolving fuel from a boiling water reactor (BWR) and to improve the solvent extraction feed clarification
Solvent extraction studies with intermediate-burnup Fast Flux Test Facility fuel in the Solvent Extraction Test Facility
In Campaign 8, two batches of irradiated fuel from the Fast Flux Test Facility (FFTF) were processed, using 30% TBP-NPH, in the Solvent Extraction Test Facility (SETF). The burnups were about 36 and 55 MWd/kg with 1.3- and 1-year cooling times, respectively. The latter fuel had the highest burnup and shortest cooling time of any fuel ever handled in the SETF. No major problems were noted during the operation of the mixer-settlers, and low uranium and plutonium losses (<0.02%) were achieved. Zirconium and ruthenium decontamination factors (DFs) were improved by increasing the number of scrub stages and increasing the peak solvent loading in the coextraction-coscrub bank. The use of an in-line photometer to measure the uranium and plutonium concentrations in a process stream permitted high solvent loadings of heavy metals to be achieved in the extraction bank while maintaining low losses to the aqueous raffinate. The investigation of two flowsheet options for making separate uranium and plutonium products (organic backscrub and selective uranium extraction) that was started in Campaign 7 was continued. High-quality products were again obtained (uranium and plutonium DFs of {similar_to}0{sup 4}). Plutonium reoxidation was still extensive even though hydrazine was added to the aqueous strip for the organic backscrub flowsheet. Two different plutonium oxalate precipitation procedures [Pu(III) and Pu(IV)] were used in the preparation of the plutonium oxide products; this was done so that the fuel fabrication characteristics of the oxide from the two procedures could be compared. A total of {similar_to}50 g of plutonium was recovered and shipped to the fuel refabrication program
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