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51.
M. T. Sellers D. G. Kelly E. C. Corcoran 《Journal of Radioanalytical and Nuclear Chemistry》2012,291(2):281-285
An automated delayed neutron counting (DNC) system has been developed at the Royal Military College of Canada (RMC) to enhance
nuclear forensics capabilities pertaining to special nuclear material analysis. The system utilises the SLOWPOKE-2 Facility
at RMC as a neutron source and 3He detectors. System control and data acquisition occur through a LabVIEW platform. The time dependent count rate of the delayed
neutron production has been examined for 235U, using certified reference materials. Experimental validation according to ISO 17025 protocols suggests typical errors and
precision of −3.6 and 3.1%, respectively, and a detection limit of 0.26 μg 235U. 相似文献
52.
M. T. Sellers E. C. Corcoran D. G. Kelly 《Journal of Radioanalytical and Nuclear Chemistry》2013,295(2):1221-1228
The Royal Military College of Canada (RMCC) has commissioned a Delayed Neutron Counting (DNC) system for the analysis of special nuclear materials. A significant, time-dependent neutron background with an initial maximum count rate, more than 50 times that of the time-independent background, was characterised during the validation of this system. This time-dependent background was found to be dependent on the presence of the polyethylene (PE) vials used to transport the fissile samples, yet was not an activation product of vial impurities. The magnitude of the time-dependent background was found to be irradiation site specific and independent of the mass of PE. The capability of RMCC’s DNC system to analyze the neutron count rates in time intervals <1 s facilitated a more detailed data analysis than that obtained in previous DNC systems recording cumulative neutron counts. An analysis of the time-dependent background behaviour suggested that an equivalent of 120 ng of 235U contamination was present on each irradiated vial. However, Inductively Coupled Plasma—Mass Spectroscopy measurements of material leached from the outer vial surfaces after their irradiations found only trace amounts of uranium, 0.118 ± 0.048 ng of 235U derived from natural uranium. These quantities are insufficient to account for the time-independent background, and in fact could not be discriminated from the noise associated with time-independent background. It is suggested that delayed neutron emitters are deposited in the vial surface following fission recoil, leaving the main body of uranium within the irradiation site. This hypothesis is supported by the physical cleaning of the site with materials soaked in distilled water and HNO3, which lowered the background from a nominal 235U mass equivalent of 120 to 50 ng per vial. 相似文献
53.
Emily B. Corcoran Jonathan P. McMullen François Lévesque Michael K. Wismer John R. Naber 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2020,132(29):12062-12066
With the development of new photocatalytic methods over recent decades, the translation of these chemical reactions to industrial-production scales using continuous-flow reactors has become a topic of increasing interest. In this context, we describe our studies toward elucidating an empirically derived parameter for scaling photocatalytic reactions in flow. By evaluating the performance of a photocatalytic C−N cross-coupling reaction across multiple reactor sizes and geometries, it was demonstrated that expressing product yield as a function of the absorbed photon equivalents provides a predictive, empirical scaling parameter. Through the use of this scaling factor and characterization of the photonic flux within each reactor, the cross-coupling was scaled successfully from the milligram scale in batch to a multi-kilogram reaction in flow. 相似文献
54.
Sethian J.D. Pawley C.J. Obenschain S.P. Gerber K.A. Serlin V. Sullivan C.A. Lehecka T. Webster W.D. McGeoch M.W. Smith I.D. Corcoran P.A. Altes R.G. 《IEEE transactions on plasma science. IEEE Nuclear and Plasma Sciences Society》1997,25(2):221-228
Nike is a recently completed multikilojoule krypton-fluoride (KrF) laser that has been built to study the physics of direct-drive inertial confinement fusion. The two final amplifiers of the Nike laser are both electron-beam-pumped systems. This paper describes these two amplifiers, with an emphasis on the pulsed power. The smaller of the two has a 20×20 cm aperture, and produces an output laser beam energy in excess of 100 J. This 20 cm Amplifier uses a single 12 kJ Marx generator to inject two 300 kV, 75 kA, 140 ns flat-top electron beams into opposite sides of the laser cell. The larger amplifier in Nike has a 60×60 cm aperture, and amplifies the laser beam up to 5 W. This 60 cm amplifier has two independent electron beam systems. Each system has a 170 kT Marx generator that produces a 670 kV, 540 kA, 240 ns Bat-top electron beam. Both amplifiers are complete, fully integrated into the laser, meet the Nike system requirements, and are used routinely for laser-target experiments 相似文献
55.
Laser scanning, corresponding to time-dependent deflections of laser beam across a field of interest, can provide relatively high illumination intensity of small particles, thereby allowing implementation of high image-density particle image velocimetry (PIV). Scanning techniques employing a rotating (multi-faceted) mirror, an oscillating mirror, and an acousto-optic deflector are addressed. Issues of illumination intensity and exposure, rate of scan of the laser beam, and retrace time of the scanning beam are assessed. Representative classes of unsteady separated flows investigated with laser-scanning PIV are described. 相似文献
56.
A. Bordner C. E. Kuehn M. Arenton H. Chen M. Corcoran L. Cormell R. Ditzler M. Dris A. R. Erwin T. Fields J. Fleischman M. Harrison M. A. Hasan K. Johns A. Kanofsky W. Kononenko H. Miettinen C. Naudet K. S. Nelson J. Rice J. Roberts B. Robinson W. Selove G. Theodosiou M. Thompson B. Yost 《Zeitschrift fur Physik C Particles and Fields》1996,72(2):249-254
An experiment performed at Fermilab used double-arm calorimeter triggers to study di-jet production by 400 GeV protons and 200 GeVπ ? mesons incident on liquid hydrogen. The observed ratio of positive to negative leading particles in the jets was compared forpp andπp production using a tree level parton scattering model. The results are moderately sensitive to the form of the pion gluon distribution function and yieldx g(x)?(1?x)2.75±0.40±0.75. 相似文献
57.
Corcoran B Pelusi MD Monat C Li J O'Faolain L Krauss TF Eggleton BJ 《Optics letters》2011,36(9):1728-1730
We demonstrate all-optical demultiplexing of a high-bandwidth, time-division multiplexed 160 Gbit/s signal to 10 Gbit/s channels, exploiting slow light enhanced four-wave mixing in a dispersion engineered, 96 μm long planar photonic crystal waveguide. We report error-free (bit error rate<10??) operation of all 16 demultiplexed channels, with a power penalty of 2.2-2.4 dB, highlighting the potential of these structures as a platform for ultracompact all-optical nonlinear processes. 相似文献
58.
Martin's perturbation theory result [2] for the dipole moment of three identical spherical atoms at large separations is shown to simplify: There are two contributions to this three-atom dipole and the strength of each factors into a product of the dipole polarizability of one atom and a two-atom average of dipole and quadrupole matrix elements. The simplified results are used to obtain an improved evaluation of the three-atom dipole of three He atoms, employing extensive pseudo-spectral representations of the dipole and quadrupole excitations. 相似文献
59.
Thomas BN Lindemann CM Corcoran RC Cotant CL Kirsch JE Persichini PJ 《Journal of the American Chemical Society》2002,124(7):1227-1233
We describe a new chiral tubule-forming lipid in which the C-O-P phosphoryl linkage of the archetypal tubule-forming molecule, 1,2-bis(10,12-tricosadiynoyl)-sn-glycero-3-phosphocholine, "DC(8,9)PC", is replaced by a C-P linkage. Tubule formation with this phosphonate analogue proceeds under the same mild conditions as with DC(8,9)PC and produces similar yields, but synchrotron small-angle X-ray scattering, atomic force microscopy, and optical microscopy show the new tubules to have diameters 1.94 times as great, to be significantly shorter, and to be thinner-walled. A significant portion of the enantiomerically pure chiral phosphonate precipitate is in the form of stable open helices, and these helices are divided almost evenly between left- and right-handed members. 相似文献
60.
Alavi-Harati A Alexopoulos T Arenton M Arisaka K Averitte S Barbosa RF Barker AR Barrio M Bellantoni L Bellavance A Belz J Ben-David R Bergman DR Blucher E Bock GJ Bown C Bright S Cheu E Childress S Coleman R Corcoran MD Corti G Cox B Crisler MB Erwin AR Ford R Glazov A Golossanov A Graham G Graham J Hagan K Halkiadakis E Hamm J Hanagaki K Hidaka S Hsiung YB Jejer V Jensen DA Kessler R Kobrak HG LaDue J Lath A Ledovskoy A McBride PL Mikelsons P Monnier E Nakaya T Nelson KS Nguyen H O'Dell V 《Physical review letters》2001,87(13):132001
We present the first measurement of the form factor ratios g(1)/f(1) (direct axial vector to vector), g(2)/f(1) (second class current), and f(2)/f(1) (weak magnetism) for the decay Xi(0)-->Sigma(+)e(-)nu macro(e) using the KTeV (E799) beam line and detector at Fermilab. From the Sigma(+) polarization measured with the decay Sigma(+)-->p pi(0) and the e(-)-nu; correlation, we measure g(1)/f(1) to be 1.32+/-(0.21)(0.17)(stat)+/-0.05(syst), assuming the SU(3)(f) (flavor) values for g(2)/f(1) and f(2)/f(1). Our results are all consistent with exact SU(3)(f) symmetry. 相似文献