250 Matching Results

Search Results

Advanced search parameters have been applied.

Atomic and molecular supernovae

Description: Atomic and molecular physics of supernovae is discussed with an emphasis on the importance of detailed treatments of the critical atomic and molecular processes with the best available atomic and molecular data. The observations of molecules in SN 1987A are interpreted through a combination of spectral and chemical modelings, leading to strong constraints on the mixing and nucleosynthesis of the supernova. The non-equilibrium chemistry is used to argue that carbon dust can form in the oxygen-rich clumps where the efficient molecular cooling makes the nucleation of dust grains possible. For Type Ia supernovae, the analyses of their nebular spectra lead to strong constraints on the supernova explosion models.
Date: December 1, 1997
Creator: Liu, W.
Partner: UNT Libraries Government Documents Department

A Continuously Sensitive Cloud Chamber

Description: A continuous cloud chamber would be a valuable asset to laboratory work in nuclear and atomic physics. For this reason the construction and investigation of a continuously sensitive diffusion cloud chamber has been undertaken. It is the purpose of this paper to report the design and operating characteristics of such a chamber.
Date: 1951
Creator: Hughes, James E.
Partner: UNT Libraries

PNC in hydrogen. different prospects using heliumlike ions.

Description: The motivation for parity experiments in simple atomic systems is that the atomic physics is known precisely so they directly test the weak interactions. We review the status of the parity experiments that have been done in atomic hydrogen and suggest some possibilities for experiments in helium like ions.
Date: September 25, 1998
Creator: Dunford, R. W.
Partner: UNT Libraries Government Documents Department

Initial Assessment of Electron and X-Ray Production and Charge Exchange in the NDCX-II Accelerator

Description: The purpose of this note is to provide initial assessments of some atomic physics effects for the accelerator section of NDCX-II. There are several effects we address: the production of electrons associated with loss of beam ions to the walls, the production of electrons associated with ionization of background gas, the possibly resultant production of X-rays when these electrons hit bounding surfaces, and charge exchange of beam ions on background gas. The results presented here are based on a number of caveats that will be stated below, which we will attempt to remove in the near future.
Date: February 18, 2010
Creator: COHEN, R.H.
Partner: UNT Libraries Government Documents Department

Research proposal on certain atomic physics measurements associated with the laser isotope separation method

Description: Research proposed in the following areas are briefly described: the measurement of photoionization cross sections near threshold for the excited states of uranium; measurement of the symmetric charge exchange cross section; and measurement of chemiionization cross sections for electronically excited uranium atoms.
Date: March 6, 1973
Creator: Dubrin, J. & Duewer, W.
Partner: UNT Libraries Government Documents Department

Argonne's atlas control system upgrade.

Description: The ATLAS facility (Argonne Tandem-Linac Accelerator System) is located at the Argonne National Laboratory. The facility is a tool used in nuclear and atomic physics research, which focuses primarily on heavy-ion physics. The accelerator as well as its control system are evolutionary in nature, and consequently, continue to advance. In 1998 the most recent project to upgrade the ATLAS control system was completed. This paper briefly reviews the upgrade, and summarizes the configuration and features of the resulting control system.
Date: September 27, 1999
Creator: Munson, F.; Quock, D.; Chapin, B. & Figueroa, J.
Partner: UNT Libraries Government Documents Department

Workshop on Molecule Assisted Recombination and Other Processes in Fusion Divertor Plasmas

Description: A brief proceedings of the two-day Workshop on Molecule Assisted Recombination and Other Processes in Fusion Divertor Plasmas, organized by the ORNL Controlled Fusion Atomic Data Center on September 8-9, 2000, is presented. The conclusions and recommendations of the workshop regarding the topics discussed and the collaboration of the U.S. fusion research and atomic physics communities are also summarized.
Date: November 9, 2000
Creator: Janev, R.K.
Partner: UNT Libraries Government Documents Department

Implementation of a high energy 4w probe beam on the Omega Laser

Description: An ultraviolet high-energy Thomson scattering probe beam has been implemented on the Omega laser facility at the University of Rochester. The new probe operates at a wavelength of 264nm, with a maximum energy of 260J in a pulselength of 1ns. The probe is focused with an F/6.7 lens to a minimum focal spot of 40{micro}m within a pointing tolerance of <50{micro}m. Data obtained from this probe beam has provided new diagnostic information on plasmas relevant for inertial confinement fusion and atomic physics studies.
Date: April 15, 2004
Creator: Mackinnon, A; Shiromizu, S; Antonini, G; Haney, K; Froula, D; Moody, J et al.
Partner: UNT Libraries Government Documents Department

Spectroscopy of Argon Excited in an Electron Beam Ion Trap

Description: Argon is one of the gases best investigated and most widely used in plasma discharge devices for a multitude of applications that range from wavelength reference standards to controlled fusion experiments. Reviewing atomic physics and spectroscopic problems in various ionization stages of Ar, the past use and future options of employing an electron beam ion trap (EBIT) for better and more complete Ar data in the x-ray, EUV and visible spectral ranges are discussed.
Date: April 18, 2005
Creator: Trabert, E
Partner: UNT Libraries Government Documents Department

Boson-fermion mixtures in two-color optical dipole traps.

Description: We propose the use of a combined optical dipole trap to achieve Fermi degeneracy by sympathetic cooling with a different bosonic species. Two far-detuned pairs of laser beams focused on the atomic clouds are used to confine the two atomic species with different trapping strengths. We show that a deep Fermi degeneracy regime can be potentially achieved earlier than Bose-Einstein condensation, as discussed in the favorable situation of a {sup 6}L i-{sup 23}Na mixture. This opens up the possibility of experimentally investigating a mixture of superfluid Fermi and normal Bose gases.
Date: January 1, 2002
Creator: Onofrio, R. (Roberto) & Presilla, Carlo
Partner: UNT Libraries Government Documents Department

When superfluids are a drag

Description: The article considers the dramatic phenomenon of seemingly frictionless flow of slow-moving superfluids. Specifically the question of whether an object in a superfluid flow experiences any drag force is addressed. A brief account is given of the history of this problem and it is argued that recent advances in ultracold atomic physics can shed much new light on this problem. The article presents the commonly held notion that sufficiently slow-moving superfluids can flow without drag and also discusses research suggesting that scattering quantum fluctuations might cause drag in a superfluid moving at any speed.
Date: January 1, 2008
Creator: Roberts, David C
Partner: UNT Libraries Government Documents Department

Detailed Hydrodynamic and X-Ray Spectroscopic Analysis of a Laser-Produced Rapidly-Expanding Aluminum Plasma

Description: We present a detailed analysis of K-shell emission from laser-produced rapidly-expanding aluminum plasmas. This work forms part of a series of experiments performed at the Vulcan laser facility of the Rutherford Appleton Laboratory, UK. 1-D planar expansion was obtained by over-illuminating Al-microdot targets supported on CH plastic foils. The small size of the Al-plasma ensured high spatial and frequency resolution of the spectra, obtained with a single crystal spectrometer, two vertical dispersion variant double crystal spectrometers, and a vertical dispersion variant Johann Spectrometer. The hydrodynamic properties of the plasma were measured independently by spatially and temporally resolved Thomson scattering, utilizing a 4{omega} probe beam. This enabled sub- and super- critical densities to be probed relative to the 1{omega} heater beams. The deduced plasma hydrodynamic conditions are compared with those generated from the 1-D hydro-code Medusa, and the significant differences found in the electron temperature discussed. Synthetic spectra generated from the detailed term collisional radiative non-LTE atomic physics code Fly are compared with the experimental spectra for the measured hydrodynamic parameters, and for those taken from Medusa. Excellent agreement is only found for both the H- and He-like Al series when careful account is taken of the temporal evolution of the electron temperature.
Date: April 3, 2001
Creator: Chambers, D M; Glenzer, S H; Hawreliak, J; Wolfrum, E; Gouveia, A; Lee, R W et al.
Partner: UNT Libraries Government Documents Department

Committee on Atomic, Molecular, and Optical Sciences (CAMOS). Technical progress report, [February 1, 1991--January 31, 1992]

Description: The Committee on Atomic, Molecular, and Optical Sciences is a standing committee under the auspices of the Board on Physics and Astronomy, Commission on Physical Sciences, Mathematics, and Applications of the National Academy of Sciences -- National Research Council. The atomic, molecular, and optical (AMO) sciences represent a broad and diverse field in which much of the research is carried out by small groups. These groups generally have not operated in concert with each other and, prior to the establishment of CAMOS, there was no single committee or organization that accepted the responsibility of monitoring the continuing development and assessing the general public health of the field as a whole. CAMOS has accepted this responsibility and currently provides a focus for the AMO community that is unique and essential. The membership of CAMOS is drawn from research laboratories in universities, industry, and government. Areas of expertise on the committee include atomic physics, molecular science, and optics. A special effort has been made to include a balanced representation from the three subfields. (A roster is attached.) CAMOS has conducted a number of studies related to the health of atomic and molecular science and is well prepared to response to requests for studies on specific issues. This report brief reviews the committee work of progress.
Date: March 1, 1992
Partner: UNT Libraries Government Documents Department