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Gordon, D.

Publications and source records attributed to Gordon, D..

At least 19 records
All sourcesNASA NTRSDOE OSTI
DOE OSTI2024

Benchmarking of hydrodynamic plasma waveguides for multi-GeV laser-driven electron acceleration

Hydrodynamic plasma waveguides initiated by optical field ionization have recently become a key component of multi-GeV laser wakefield accelerators. Here, we present the most complete and accurate experimental and simulation-based characterization to date, applicable to current multi-GeV experiments and future 100 GeV-scale laser plasma accelerators. Crucial to the simulations is the correct modeling of intense Bessel beam interaction with meter-scale gas targets, the results of which are used as initial conditions for hydrodynamic simulations. The simulations are in good agreement with our experiments measuring evolving plasma and neutral hydrogen density profiles using two-color short pulse interferometry, enabling realistic determination of the guided mode structure for application to laser-driven plasma accelerator design. Published by the American Physical Society 2024

Physics↗
NASA NTRS2015

Comparison of Realizations of the Terrestrial Reference Frame

IGN and DGFI both generated realizations of the terrestrial reference frame under the auspices of the IERS from combination of the same space geodetic data. We compared the IGN and DGFI TRFs with a GSFC CALC/SOLVE TRF. WRMS position and velocity differences for the 40 most frequently observed sites were 2-3 mm and 0.3-0.4 mm/year. There was a scale difference of 0.39/0.09 ppb between the IGN/DGFI realizations and the GSFC solution. When we fixed positions and velocities to either the IGN or DGFI values in CALC/SOLVE solutions, the resulting EOP estimates were not significantly different from the estimates from a standard TRF solution.

Comparison↗
NASA NTRS2010

Theory and Realization of Global Terrestrial Reference Systems

Comparison of realizations of the terrestrial reference frame. IGN and DGFI both generated realizations of the terrestrial reference frame under the auspices of the IERS from combination of the same space geodetic data. We examined both results for VLBI sites using the full geodetic VLBI data set with respect to site positions and velocities and time series of station positions, baselines and Earth orientation parameters. One of the difficulties encountered was matching episodic breaks and periods of non-linear motion of the two realizations with the VLBI models. Our analysis and conclusions will be discussed.

Ma, C.↗
NASA NTRS2003

Astrometry at 24 and 43 GHz

We describe the goals and initial results of a collaboration formed to survey extragalactic objects at radio frequencies of 24 and 43 GHz This survey is for extending the International Celestial Reference Frame (ICRF) that is the current coordinate system for astrometry and wh ich is the angular inertial frame of deep space navigation. In princ iple, the extension should lead to a more stable reference frame. We report upon our initial three 24-hour observing sessions involving about 100 radio sources at the VLBA.

astrometry↗