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29 results on '"McPhate, J. B."'

1. Soft X-ray MCP/Timepix Photon Counting Detectors for Synchrotron and FEL Applications

Author

Tremsin, A. S., primary, Vallerga, J. V., additional, Curtis, T., additional, Tercero, D., additional, McPhate, J. B., additional, Siegmund, O., additional, Raffanti, R., additional, Roy, S., additional, Chuang, Y.-D., additional, Morley, S., additional, McCarter, M., additional, Saleheen, A., additional, Turner, J., additional, Dakovski, G., additional, Schoenlein, R., additional, and Hansson, C., additional

Published
2023
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3. Imaging Photon Counting Detectors for High Time Resolution Astronomy

Author

Siegmund, O. H. W., Vallerga, J. V., Welsh, B., Tremsin, A. S., McPhate, J. B., Burton, W. B., editor, Bertola, F., editor, Cassinelli, J. P., editor, Cesarsky, C. J., editor, Ehrenfreund, P., editor, Engvold, O., editor, Heck, A., editor, Van Den Heuvel, E.P.J., editor, Kaspi, V. M., editor, Kuijpers, J.M.E., editor, Van Der Laan, H., editor, Murdin, P. G., editor, Pacini, F., editor, Radhakrishnan, V., editor, Somov, B. V., editor, Sunyaev, R. A., editor, Phelan, Don, editor, Ryan, Oliver, editor, and Shearer, Andrew, editor

Published
2008
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4. Initial Observations by the GOLD Mission

Author

Eastes, R. W., primary, McClintock, W. E., additional, Burns, A. G., additional, Anderson, D. N., additional, Andersson, L., additional, Aryal, S., additional, Budzien, S. A., additional, Cai, X., additional, Codrescu, M. V., additional, Correira, J. T., additional, Daniell, R. E., additional, Dymond, K. F., additional, England, S. L., additional, Eparvier, F. G., additional, Evans, J. S., additional, Foroosh, H., additional, Gan, Q., additional, Greer, K. R., additional, Karan, D. K., additional, Krywonos, A., additional, Laskar, F. I., additional, Lumpe, J. D., additional, Martinis, C. R., additional, McPhate, J. B., additional, Oberheide, J., additional, Siegmund, O. H., additional, Solomon, S. C., additional, Veibel, V., additional, and Woods, T. N., additional

Published
2020
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5. Initial Observations by the GOLD Mission

Author

Eastes, R. W., McClintock, William E., Burns, A. G., Anderson, D. N., Andersson, L., Aryal, S., Budzien, S. A., Cai, X., Codrescu, M., Correira, J. T., Daniell, R. E., Dymond, K. F., England, Scott L., Eparvier, F. G., Evans, J. S., Foroosh, H., Gan, Q., Greer, K. R., Karan, D. K., Krywonos, A., Laskar, F., I, Lumpe, J. D., Martinis, C. R., McPhate, J. B., Oberheide, J., Siegmund, O. H., Solomon, S. C., Veibel, V., Woods, T. N., Eastes, R. W., McClintock, William E., Burns, A. G., Anderson, D. N., Andersson, L., Aryal, S., Budzien, S. A., Cai, X., Codrescu, M., Correira, J. T., Daniell, R. E., Dymond, K. F., England, Scott L., Eparvier, F. G., Evans, J. S., Foroosh, H., Gan, Q., Greer, K. R., Karan, D. K., Krywonos, A., Laskar, F., I, Lumpe, J. D., Martinis, C. R., McPhate, J. B., Oberheide, J., Siegmund, O. H., Solomon, S. C., Veibel, V., and Woods, T. N.

Abstract

The NASA Global-scale Observations of the Limb and Disk (GOLD) mission has flown an ultraviolet-imaging spectrograph on SES-14, a communications satellite in geostationary orbit at 47.5 degrees W longitude. That instrument observes the Earth's far ultraviolet (FUV) airglow at similar to 134-162 nm using two identical channels. The observations performed include limb scans, stellar occultations, and images of the sunlit and nightside disk from 6:10 to 00:40 universal time each day. Initial analyses reveal interesting and unexpected results as well as the potential for further studies of the Earth's thermosphere-ionosphere system and its responses to solar-geomagnetic forcing and atmospheric dynamics. Thermospheric composition ratios for major constituents, O and N-2, temperatures near 160 km, and exospheric temperatures are retrieved from the daytime observations. Molecular oxygen (O-2) densities are measured using stellar occultations. At night, emission from radiative recombination in the ionosphericFregion is used to quantify ionospheric density variations in the equatorial ionization anomaly (EIA). Regions of depletedFregion electron density are frequently evident, even during the current solar minimum. These depletions are caused by the "plasma fountain effect" and are associated with the instabilities, scintillations, or "spreadF" seen in other types of observations, and GOLD makes unique observations for their study. Plain Language Summary The NASA Global-scale Observations of the Limb and Disk (GOLD) mission has flown a dual-channel, ultraviolet-imaging spectrograph on SES-14, a communications satellite in geostationary orbit at 47.5 degrees W longitude. That instrument observes the Earth's far ultraviolet (FUV) airglow at similar to 134-162 nm. The observations performed include images of the Earth's sunlit and nightside disk, limb scans, and stellar occultations, from 6:10 to 00:40 universal time each day. Initial analyses reveal interesting and unexpected

Published
2020

7. Detection of CO Cameron band emission in comet P/Hartley 2 (1991 XV) with the Hubble Space Telescope

Author

Weaver, H. A, Feldman, P. D, Mcphate, J. B, A'Hearn, M. F, Arpigny, C, and Smith, T. E

Subjects
Astrophysics
Abstract

Ultraviolet (UV) spectra of comet P/Hartley 2 (1991 XV) taken with the Faint Object Spectrograph (FOS) on the Hubble Space Telescope (HST) in 1991 September reveal several bands of the Cameron system of CO (a 3 Pi-X 1 Sigma). These band are most likely due to 'prompt' emission from CO2 and, thus, provide a direct tracer of the CO2 abundance in the nucleus. Photodissociative excitation of CO2 is probably the largest contributor to the Cameron band emission, but significant contributions from electron impact excitation of CO, electron impact dissociation of CO2, and dissociative recombination of CO2(+), are also possible. Using our estimate that photodissociative excitation is responsible for approximately 60% of the total excitation of the Cameron system, we derive Q(sub CO2) approximately 2.6 x 10(exp 27) molecules/s, which implies CO2/H20 approximately 4%. If all of the Cameron band emission is due to photodissociative excitation, then CO2/H2O = 7 +/- 2%. For the largest possible contributions from the other excitation mechanisms considered, the CO2 abundance could be as a small as aproximately 2-3%. We did not detect CO Fourth Positive Group emission in our data and derive an upper limit of CO/H2O less than or equal to 1% (3 sigma) for CO coming directly from the nucleus. Comparison of the relative CO2 and CO abundances in P/Hartley 2 to those in P/Halley (CO2/H2O approximately 3%-4%, CO/H20 approximately 4% for the nucleus source) indicates that selective devolatilization of the nucleus may have occurred for P/Hartley 2. A relatively large CO2/CO ratio (i.e., approximately greater than 1) seems to be a common property of cometary nuclei. Since gas phase chemistry, in either the solar nebula or the interstellar medium (ISM), appears incapable of producing large relative CO2 abundances, the CO2 in cometary nuclei is probably produced either by UV and/or cosmic ray irradiation of ISM grains prior to the formation of the Solar System, or by condensation fractionation in the solar nebula.

Published
1994
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10. Imaging of dynamic magnetic fields with spin-polarized neutron beams

Author

Tremsin, A. S., Kardjilov, N., Strobl, M., Manke, I., Dawson, M., McPhate, J. B., Vallerga, J. V., Siegmund, O. H. W., Feller, W. B., Tremsin, A. S., Kardjilov, N., Strobl, M., Manke, I., Dawson, M., McPhate, J. B., Vallerga, J. V., Siegmund, O. H. W., and Feller, W. B.

Published
2015

22. Advances in microchannel plates and photocathodes for ultraviolet photon counting detectors

Author

Siegmund, O. H. W., primary, Fujiwara, K., additional, Hemphill, R., additional, Jelinsky, S. R., additional, McPhate, J. B., additional, Tremsin, A. S., additional, Vallerga, J. V., additional, Frisch, H. J., additional, Elam, J., additional, Mane, A., additional, Bennis, D. C., additional, Craven, C. A., additional, Deterando, M. A., additional, Escolas, J. R., additional, Minot, M. J., additional, and Renaud, J. M., additional

Published
2011
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27. High-Resolution Strain Mapping Through Time-of-Flight Neutron Transmission Diffraction with a Microchannel Plate Neutron Counting Detector.

Author

Tremsin, A. S., McPhate, J. B., Steuwer, A., Kockelmann, W., M Paradowska, A., Kelleher, J. F., Vallerga, J. V., Siegmund, O. H. W., and Feller, W. B.

Subjects
*NEUTRONS, *NEUTRON counters, *OPTICAL diffraction, *NEUTRON radiography, *PULSED neutron techniques
Abstract

Conventional neutron radiography can be strongly enhanced by obtaining Bragg-edge information spatially correlated with the attenuation coefficient. This can now be achieved through time-of-flight techniques at pulsed neutron sources, utilising a neutron counting detector with high-spatial and high-temporal resolution. In these measurements, the positions of Bragg edges can in principle be obtained for each 55 × 55 μm2 pixel of the radiographic image. The combination of both Bragg-edge and attenuation information enables high spatial resolution studies to be carried out on material composition, phase transitions, texture variations, as well as residual strain mapping. In this article, we present the results of high-resolution strain maps of a ferritic steel cantilever sample measured at different loads by both transmission and conventional diffraction modes, as well as strains in an austenitic steel compact-tension (CT) crack sample. The proof of principle experiments performed on the ENGIN-X beamline on a bent cantilever arrangement resulting in a uni-axial stress field verified that the strain values measured in diffraction and transmission mode are in good agreement. The characteristics of the transmission mode detector as well as the measured strain maps and future possibilities of this technology are discussed. [ABSTRACT FROM AUTHOR]

Published
2012
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29. Narcissistic Ghosts in Rowland-Mounted, Concave Gratings with nu = 0 degrees : a Cautionary Note.

Author

McCandliss SR, McPhate JB, and Feldman PD

Abstract

Narcissistic ghost lines in a Rowland-grating spectrograph have been identified as arising from the reimaging of bright spectral features, which are incident on the face of a detector photocathode [Cesium iodide (CsI) on a microchannel plate], back onto the detector by the grating in zero order. The mean of the wavelength of the diffracted light and the apparent wavelength of the ghost allows the angle of the grating normal with respect to the input beam (alpha) to be determined. Measurements of ghost intensity as a function of wavelength are presented and are found to range between 7 x 10(-4) and 7 x 10(-3) of the parent line. We find that the sum of the CsI photocathode reflectivity and quantum efficiency <1/2, showing the bulk of the light incident upon the detector, is neither reflected nor detected. We caution that any Rowland circle spectrograph with a detector normal nearly aligned with the grating normal and with a sufficiently reflective detector face (or surrounding mounting structure) will suffer from these narcissistic ghosts.

Published
1998
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