Analysis of NSTX Upgrade OH Magnet and Center Stack (open access)

Analysis of NSTX Upgrade OH Magnet and Center Stack

The new ohmic heating (OH) coil and center stack for the National Spherical Torus Experiment (NSTX) upgrade are required to meet cooling and structural requirements for operation at the enhanced 1 Tesla toroidal field and 2 MA plasma current. The OH coil is designed to be cooled in the time between discharges by water flowing in the center of the coil conductor. We performed resistive heating and thermal hydraulic analyses to optimize coolant channel size to keep the coil temperature below 100 C and meet the required 20 minute cooling time. Coupled electromagnetic, thermal and structural FEA analyses were performed to determine if the OH coil meets the requirements of the structural design criteria. Structural response of the OH coil to its self-field and the field from other coils was analyzed. A model was developed to analyze the thermal and electromagnetic interaction of centerstack components such as the OH coil, TF inner legs and the Bellville washer preload mechanism. Torsional loads from the TF interaction with the OH and poloidal fields are transferred through the TF flag extensions via a torque transfer coupling to the rest of the tokamak structure. A 3D FEA analysis was performed to qualify this design. …
Date: November 30, 2010
Creator: A. Zolfaghari, P. Titus, J. Chrzanowski, A. Salehzadeh, F. Dahlgren
System: The UNT Digital Library
Search for a Heavy Neutral Particle Decaying Into an Electron and a Muon Using 1 Fb^-1 of ATLAS Data (open access)

Search for a Heavy Neutral Particle Decaying Into an Electron and a Muon Using 1 Fb^-1 of ATLAS Data

None
Date: May 30, 2013
Creator: Aad, Georges
System: The UNT Digital Library
Fermi LAT Observation of Diffuse Gamma-Rays Produced through Interactions Between Local Interstellar Matter and High Energy Cosmic Rays (open access)

Fermi LAT Observation of Diffuse Gamma-Rays Produced through Interactions Between Local Interstellar Matter and High Energy Cosmic Rays

Observations by the Large Area Telescope (LAT) on the Fermi mission of diffuse {gamma}-rays in a mid-latitude region in the third quadrant (Galactic longitude l from 200{sup o} to 260{sup o} and latitude |b| from 22{sup o} to 60{sup o}) are reported. The region contains no known large molecular cloud and most of the atomic hydrogen is within 1 kpc of the solar system. The contributions of {gamma}-ray point sources and inverse Compton scattering are estimated and subtracted. The residual {gamma}-ray intensity exhibits a linear correlation with the atomic gas column density in energy from 100 MeV to 10 GeV. The measured integrated {gamma}-ray emissivity is (1.63 {+-} 0.05) x 10{sup -26} photons s{sup -1}sr{sup -1} H-atom{sup -1} and (0.66 {+-} 0.02) x 10{sup -26} photons s{sup -1}sr{sup -1} H-atom{sup -1} above 100 MeV and above 300 MeV, respectively, with an additional systematic error of {approx}10%. The differential emissivity from 100 MeV to 10 GeV agrees with calculations based on cosmic ray spectra consistent with those directly measured, at the 10% level. The results obtained indicate that cosmic ray nuclei spectra within 1 kpc from the solar system in regions studied are close to the local interstellar spectra inferred from …
Date: March 30, 2012
Creator: Abdo, A. A.; /Naval Research Lab, Wash., D.C. /Federal City Coll.; Ackermann, M.; /Stanford U., HEPL /KIPAC, Menlo Park /Stanford U., Phys. Dept.; Ajello, M.; /Stanford U., HEPL /KIPAC, Menlo Park /Stanford U., Phys. Dept. et al.
System: The UNT Digital Library
Fermi Observations of GRB 090902B: A Distinct Spectral Component in the Prompt and Delayed Emission (open access)

Fermi Observations of GRB 090902B: A Distinct Spectral Component in the Prompt and Delayed Emission

None
Date: March 30, 2012
Creator: Abdo, A. A.; Ackermann, M.; Ajello, M.; Asano, K.; Atwood, W. B.; Axelsson, M. et al.
System: The UNT Digital Library
The First Fermi Large Area Telescope Catalog of Gamma-Ray Pulsars (open access)

The First Fermi Large Area Telescope Catalog of Gamma-Ray Pulsars

None
Date: March 30, 2012
Creator: Abdo, A. A.; Ackermann, M.; Ajello, M.; Atwood, W. B.; Axelsson, M.; Baldini, L. et al.
System: The UNT Digital Library
Fermi-LAT Discovery of Extended Gamma-Ray Emission in the Direction of Supernova Remnant W51C (open access)

Fermi-LAT Discovery of Extended Gamma-Ray Emission in the Direction of Supernova Remnant W51C

The discovery of bright gamma-ray emission coincident with supernova remnant (SNR) W51C is reported using the Large Area Telescope (LAT) onboard the Fermi Gamma-ray Space Telescope. W51C is a middle-aged remnant ({approx}10{sup 4} yr) with intense radio synchrotron emission in its shell and known to be interacting with a molecular cloud. The gamma-ray emission is spatially extended, broadly consistent with the radio and X-ray extent of SNR W51C. The energy spectrum in the 0.2-50 GeV band exhibits steepening toward high energies. The luminosity is greater than 1 x 10{sup 36} erg s{sup -1} given the distance constraint of D > 5.5 kpc, which makes this object one of the most luminous gamma-ray sources in our Galaxy. The observed gamma-rays can be explained reasonably by a combination of efficient acceleration of nuclear cosmic rays at supernova shocks and shock-cloud interactions. The decay of neutral p mesons produced in hadronic collisions provides a plausible explanation for the gamma-ray emission. The product of the average gas density and the total energy content of the accelerated protons amounts to {bar n}{sub H} W{sub p} {approx_equal} 5 x 10{sup 51} (D/6 kpc){sup 2} erg cm{sup -3}. Electron density constraints from the radio and X-ray bands …
Date: March 30, 2012
Creator: Abdo, A. A.; Ackermann, M.; Ajello, M.; Baldini, L.; Ballet, J.; Barbiellini, G. et al.
System: The UNT Digital Library
Pulsed Gamma-Rays From PSR J2021 3651 with the Fermi Large Area Telescope (open access)

Pulsed Gamma-Rays From PSR J2021 3651 with the Fermi Large Area Telescope

We report the detection of pulsed gamma-rays from the young, spin-powered radio pulsar PSR J2021+3651 using data acquired with the Large Area Telescope (LAT) on the Fermi Gamma-ray Space Telescope (formerly GLAST). The light curve consists of two narrow peaks of similar amplitude separated by 0.468 {+-} 0.002 in phase. The first peak lags the maximum of the 2 GHz radio pulse by 0.162 {+-} 0.004 {+-} 0.01 in phase. The integral gamma-ray photon flux above 100 MeV is (56 {+-} 3 {+-} 11) x 10{sup -8} cm{sup -2} s{sup -1}. The photon spectrum is well-described by an exponentially cut-off power law of the form dF/dE = kE{sup -{Gamma}}e{sup (-E/E{sub c})} where the energy E is expressed in GeV. The photon index is {Gamma} = 1.5 {+-} 0.1 {+-} 0.1 and the exponential cut-off is E{sub c} = 2.4 {+-} 0.3 {+-} 0.5 GeV. The first uncertainty is statistical and the second is systematic. The integral photon flux of the bridge is approximately 10% of the pulsed emission, and the upper limit on off-pulse gamma-ray emission from a putative pulsar wind nebula is < 10% of the pulsed emission at the 95% confidence level. Radio polarization measurements yield a rotation …
Date: November 30, 2011
Creator: Abdo, Aous A.; Ackermann, M.; Ajello, Marco; Atwood, William B.; Baldini, L.; Ballet, J. et al.
System: The UNT Digital Library
Expanded Content Envelope For The Model 9977 Packaging (open access)

Expanded Content Envelope For The Model 9977 Packaging

An Addendum was written to the Model 9977 Safety Analysis Report for Packaging adding a new content consisting of DOE-STD-3013 stabilized plutonium dioxide materials to the authorized Model 9977 contents. The new Plutonium Oxide Content (PuO{sub 2}) Envelope will support the Department of Energy shipment of materials between Los Alamos National Laboratory and Savannah River Site facilities. The new content extended the current content envelope boundaries for radioactive material mass and for decay heat load and required a revision to the 9977 Certificate of Compliance prior to shipment. The Addendum documented how the new contents/configurations do not compromise the safety basis presented in the 9977 SARP Revision 2. The changes from the certified package baseline and the changes to the package required to safely transport this material is discussed.
Date: July 30, 2013
Creator: Abramczyk, G. A.; Loftin, B. M.; Nathan, S. J. & Bellamy, J. S.
System: The UNT Digital Library
A Beam Driven Plasma-Wakefield Linear Collider: From Higgs Factory to Multi-TeV (open access)

A Beam Driven Plasma-Wakefield Linear Collider: From Higgs Factory to Multi-TeV

None
Date: September 30, 2013
Creator: Adli, E.; Delahaye, J. P.; Gessner, S. J.; Hogan, M. J.; Raubenheimer, T.; An, W. et al.
System: The UNT Digital Library
Efficient and Scalable Retrieval Techniques for Global File Properties (open access)

Efficient and Scalable Retrieval Techniques for Global File Properties

None
Date: April 30, 2012
Creator: Ahn, D H; Brim, M; de Supinski, B R; Gamblin, T; Lee, G L; LeGendre, M P et al.
System: The UNT Digital Library
Advanced Compton scattering light source R&D at LLNL (open access)

Advanced Compton scattering light source R&D at LLNL

None
Date: July 30, 2010
Creator: Albert, F.; Anderson, S. G.; Anderson, G.; Bayramian, A.; Betts, S. M.; Chu, T. S. et al.
System: The UNT Digital Library
Novel Reconstruction Technique for New Physics Processes With Initial State Radiation (open access)

Novel Reconstruction Technique for New Physics Processes With Initial State Radiation

None
Date: November 30, 2011
Creator: Alwall, Johan; Hiramatsu, Kenji; Nojiri, Mihoko M. & Shimizu, Yasuhiro
System: The UNT Digital Library
Rugby Hohlraum Campaign on the National Ignition (open access)

Rugby Hohlraum Campaign on the National Ignition

None
Date: August 30, 2013
Creator: Amendt, P
System: The UNT Digital Library
A Plasma Lens for Magnetron Sputtering (open access)

A Plasma Lens for Magnetron Sputtering

A plasma lens, consisting of a solenoid and potential-defining ring electrodes, has been placed between a magnetron and substrates to be coated. Photography reveals qualitative information on excitation, ionization, and the transport of plasma to the substrate.
Date: November 30, 2010
Creator: Anders, Andre & Brown, Jeff
System: The UNT Digital Library
Dense Metal Plasma in a Solenoid for Ion Beam Neutralization (open access)

Dense Metal Plasma in a Solenoid for Ion Beam Neutralization

Space-charge neutralization is required to compress and focus a pulsed, high-current ion beam on a target for warm dense matter physics or heavy ion fusion experiments. We described approaches to produce dense plasma in and near the final focusing solenoid through which the ion beam travels, thereby providing an opportunity for the beam to acquire the necessary space-charge compensating electrons. Among the options are plasma injection from pulsed vacuum arc sources located outside the solenoid, and using a high current (> 4 kA) pulsed vacuum arc plasma from a ring cathode near the edge of the solenoid. The plasma distribution is characterized by photographic means, by an array of movable Langmuir probes, by a small single probe, and by evaluating Stark broadening of the Balmer H beta spectral line. In the main approach described here, the plasma is produced at several cathode spots distributed azimuthally on the ring cathode. It is shown that the plasma is essentially hollow, as determined by the structure of the magnetic field, though the plasma density exceeds 1014 cm-3 in practically all zones of the solenoid volume if the ring electrode is placed a few centimeters off the center of the solenoid. The plasma is …
Date: October 30, 2010
Creator: Anders, Andre; Kauffeldt, Marina; Oks, Efim M. & Roy, Prabir K.
System: The UNT Digital Library
Hollow Plasma in a Solenoid (open access)

Hollow Plasma in a Solenoid

A ring cathode for a pulsed, high-current, multi-spot cathodic arc discharge was placed inside a pulsed magnetic solenoid. Photography is used to evaluate the plasma distribution. The plasma appears hollow for cathode positions close the center of the solenoid, and it is guided closer to the axis when the cathode is away from the center.
Date: November 30, 2010
Creator: Anders, Andre; Kauffeldt, Marina; Oks, Efim M. & Roy, Prabir K.
System: The UNT Digital Library
LIFE: The Case for Early Commercialization of Fusion Energy (open access)

LIFE: The Case for Early Commercialization of Fusion Energy

This paper presents the case for early commercialization of laser inertial fusion energy (LIFE). Results taken from systems modeling of the US electrical generating enterprise quantify the benefits of fusion energy in terms of carbon emission, nuclear waste and plutonium production avoidance. Sensitivity of benefits-gained to timing of market-entry is presented. These results show the importance of achieving market entry in the 2030 time frame. Economic modeling results show that fusion energy can be competitive with other low-carbon energy sources. The paper concludes with a description of the LIFE commercialization path. It proposes constructing a demonstration facility capable of continuous fusion operations within 10 to 15 years. This facility will qualify the processes and materials needed for a commercial fusion power plant.
Date: November 30, 2010
Creator: Anklam, Thomas; Simon, Aaron J.; Powers, Sarah & Meier, Wayne R.
System: The UNT Digital Library
The Capsule-Fill-Tube-Assembly Mapping System (open access)

The Capsule-Fill-Tube-Assembly Mapping System

None
Date: July 30, 2012
Creator: Antipa, N. A.
System: The UNT Digital Library
Prospects for achieving high dynamic compression with low energy (open access)

Prospects for achieving high dynamic compression with low energy

None
Date: July 30, 2012
Creator: Armstrong, M. R.; Bastea, S.; Crowhurst, J.; Howard, W.; Zaug, J. & Goncharov, A.
System: The UNT Digital Library
Measurement of |Vcb| and the Form-Factor Slope in Bbar -> Dlnu Decays in Events Tagged by a Fully Reconstructed B Meson (open access)

Measurement of |Vcb| and the Form-Factor Slope in Bbar -> Dlnu Decays in Events Tagged by a Fully Reconstructed B Meson

We present a measurement of the Cabibbo-Kobayashi-Maskawa matrix element |V{sub cb}| and the form-factor slope {rho}{sup 2} in {bar B} {yields} D{ell}{sup -} {bar {nu}}{sub {ell}} decays based on 460 million B{bar B} events recorded at the {Gamma}(4S) resonance with the BABAR detector. {bar B} {yields} D{ell}{sup -} {bar {nu}}{sub {ell}} decays are selected in events in which a hadronic decay of the second B meson is fully reconstructed. We measure the differential decay rate and determine G(1)|V{sub cb}| = (43.0 {+-} 1.9 {+-} 1.4) x 10{sup -3} and {rho}{sup 2} = 1.20 {+-}0.09 {+-} 0.04, where G(1) is the hadronic form factor at the point of zero recoil. We also determine the exclusive branching fractions and find {Beta}(B{sup -} {yields} D{sup 0} {ell}{sup -}{bar {nu}}{sub {ell}}) = (2.31 {+-} 0.08 {+-} 0.09)% and {Beta}(B{sup 0} {yields} D{sup +} {ell}{sup -} {bar {nu}}{sub {ell}}) = (2.23 {+-} 0.11 {+-} 0.11)%.
Date: June 30, 2011
Creator: Aubert, Bernard; Karyotakis, Y.; Lees, J. P.; Poireau, V.; Prencipe, E.; Prudent, X. et al.
System: The UNT Digital Library
Measurements of Charged Current Lepton Universality and |Vus| using Tau Lepton Decays to e- v v, __- v v, pi- v and K- v (open access)

Measurements of Charged Current Lepton Universality and |Vus| using Tau Lepton Decays to e- v v, __- v v, pi- v and K- v

Using 467 fb{sup -1} of e{sup +}e{sup -} annihilation data collected with the BABAR detector, they measure {Beta}({tau}{sup -} {yields} {mu}{sup -}{bar {nu}}{sub {mu}}{nu}{sub {tau}})/{Beta}({tau}{sup -} {yields} e{sup -} {bar {nu}}{sub e}{nu}{sub {tau}}) = (0.9796 {+-} 0.0016 {+-} 0.0036), {Beta}({tau}{sup -} {yields} {pi}{sup -} {nu}{sub {tau}})/{Beta}({tau}{sup -} {yields} e{sup -}{bar {nu}}{sub e}{nu}{sub {tau}}) = (0.5945 {+-} 0.0014 {+-} 0.0061), and {Beta}({tau}{sup -} {yields} K{sup -}{nu}{sub {tau}})/{Beta}({tau}{sup -} {yields} e{sup -}{bar {nu}}{sub e}{nu}{sub {tau}}) = (0.03882 {+-} 0.00032 {+-} 0.00057), where the uncertainties are statistical and systematic, respectively. From these precision {tau} measurements, they test the Standard Model assumption of {mu}-e and {tau}-{mu} charge current lepton universality and provide determinations of |V{sub us}| experimentally independent of the decay of a kaon.
Date: June 30, 2011
Creator: Aubert, Bernard; Karyotakis, Y.; Lees, J. P.; Poireau, V.; Prencipe, E.; Prudent, X. et al.
System: The UNT Digital Library
2010 Thin Film & Small Scale Mechanical Behavior Gordon Research Conference (open access)

2010 Thin Film & Small Scale Mechanical Behavior Gordon Research Conference

Over the past decades, it has been well established that the mechanical behavior of materials changes when they are confined geometrically at least in one dimension to small scale. It is the aim of the 2010 Gordon Conference on 'Thin Film and Small Scale Mechanical Behavior' to discuss cutting-edge research on elastic, plastic and time-dependent deformation as well as degradation mechanisms like fracture, fatigue and wear at small scales. As in the past, the conference will benefit from contributions from fundamental studies of physical mechanisms linked to material science and engineering reaching towards application in modern applications ranging from optical and microelectronic devices and nano- or micro-electrical mechanical systems to devices for energy production and storage. The conference will feature entirely new testing methodologies and in situ measurements as well as recent progress in atomistic and micromechanical modeling. Particularly, emerging topics in the area of energy conversion and storage, such as material for batteries will be highlighted. The study of small-scale mechanical phenomena in systems related to energy production, conversion or storage offer an enticing opportunity to materials scientists, who can provide new insight and investigate these phenomena with methods that have not previously been exploited.
Date: July 30, 2010
Creator: Balk, Dr. Thomas
System: The UNT Digital Library
Threshold Studies of the Microwave Instability in Electron Storage Rings (open access)

Threshold Studies of the Microwave Instability in Electron Storage Rings

We use a Vlasov-Fokker-Planck program and a linearized Vlasov solver to study the microwave instability threshold of impedance models: (1) a Q = 1 resonator and (2) shielded coherent synchrotron radiation (CSR), and find the results of the two programs agree well. For shielded CSR we show that only two dimensionless parameters, the shielding parameter {Pi} and the strength parameter S{sub csr}, are needed to describe the system. We further show that there is a strong instability associated with CSR, and that the threshold, to good approximation, is given by (S{sub csr})th = 0.5 + 0.12{Pi}. In particular, this means that shielding has little effect in stabilizing the beam for {Pi} {approx}< 2; for larger {Pi} it is effective, with threshold current depending on shielding aperture as h{sup -3/2}. We, in addition, find another instability in the vicinity of {Pi} = 0.7 with a lower threshold, (S{sub csr}){sub th} {approx} 0.2. We find that the threshold to this instability depends strongly on damping time, (S{sub csr}){sub th} {approx} {tau}{sub p}{sup -1/2}, and that the tune spread at threshold is small - both hallmarks of a weak instability.
Date: July 30, 2010
Creator: Bane, K. L. F.; Cai, Y. & Stupakov, G.
System: The UNT Digital Library
The Benefits of Stress: Resolution of the Lifshitz Singularity (open access)

The Benefits of Stress: Resolution of the Lifshitz Singularity

None
Date: October 30, 2013
Creator: Bao, Ning; Dong, Xi; Harrison, Sarah & Silverstein, Eva
System: The UNT Digital Library