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Steady-state and Dynamic Probe Characteristics in a Low-density Plasma

Description: The problem with which this investigation is concerned is that of determining the steady-state and dynamic characteristics of the admittance of a metallic probe immersed in a laboratory plasma which has the low electron densities and low electron temperatures characteristic of the ionospheric plasma. The problem is separated into three related topics: the design and production of the laboratory plasma, the measurement of the steady-state properties of dc and very low frequency probe admittance, and the study of transient ion sheath effects on radio frequency probe admittance.
Date: December 1970
Creator: Bunting, William David
Partner: UNT Libraries

Compact Probe for Power Detection from the Narrow Side of the Waveguide

Description: Phased array antennas with high directivity have a variety of applications. One of their applications is in RF heating for magnetically confined plasma fusion research. Among these RF heating schemes, waveguide arrays with careful phase control on each waveguide can act as a phased array antenna to deliver megawatts of power for heating fusion plasmas in the lower-hybrid range of frequencies (1 GHz-10 GHz). In order to achieve compactness, it is common to stack reduced height waveguide together to form the waveguide array. As long as the delivered power does not cause arcing in the waveguide, the waveguide height can be quite small. Due to this confined space in a stack of reduced height waveguides, power detection of the incident and reflected wave in the reduced height waveguide is extremely difficult. A new compact probe, which employs current loops, to monitor the incident and reflected wave from the narrow side of the reduced height waveguide has been developed. Its theory and performance will be reported in this paper.
Date: May 7, 2004
Creator: Kung, C.C.; Bernabei, S.; Gumbas, J.; Greenough, N.; Fredd, E.; Wilson, J.R. et al.
Partner: UNT Libraries Government Documents Department

Universality of Unintegrated Gluon Distributions at small x

Description: We systematically study dijet production in various processes in the small-x limit and establish an effective kt-factorization for hard processes in a system with dilute probes scattering on a dense target. In the large-Nc limit, the unintegrated gluon distributions involved in different processes are shown to be related to two widely proposed ones: the Weizsacker-Williams gluon distribution and the dipole gluon distribution.
Date: January 4, 2011
Creator: Dominguez, Fabio; Marquet, Cyrille; Xiao, Bowen & Yuan, Feng
Partner: UNT Libraries Government Documents Department

Negative differential mobility of weakly driven particles in models of glass formers

Description: We study the response of probe particles to weak constant driving in kinetically constrained models of glassy systems, and show that the probe's response can be non-monotonic and give rise to negative differential mobility: increasing the applied force can reduce the probe's drift velocity in the force direction. Other significant non-linear effects are also demonstrated, such as the enhancement with increasing force of the probe's fluctuations away from the average path, a phenomenon known in other contexts as giant diffusivity. We show that these results can be explained analytically by a continuous-time random walk approximation where there is decoupling between persistence and exchange times for local displacements of the probe. This decoupling is due to dynamic heterogeneity in the glassy system, which also leads to bimodal distributions of probe particle displacements. We discuss the relevance of our results to experiments.
Date: April 1, 2008
Creator: Jack, Robert L.; Kelsey, David; Garrahan, Juan P. & Chandler, David
Partner: UNT Libraries Government Documents Department

Technical assessment of BY-1 12 liquid observation well (LOW) anomalous readings

Description: This document contains a technical assessment of the cause and disposition of Interstitial Liquid Level(ILL) readings taken in February 1997 on Hanford waste tank 241-BY-112 that were below specified limits. Some readings were determined to be spurious while other readings were below the limit because of normal data scatter. The data assessment did discover that a new ILL had formed below the currently established baseline because of the normal drainage of the interstitial liquid over time. A new baseline and limit will be established. Because the new ILL appears to be stable and consistent with post saltwell pumping behavior, and because there is no other evidence to the contrary, the tank is judged not to be leaking.
Date: March 11, 1997
Creator: Barnes, D. A. & Reed, R. W.
Partner: UNT Libraries Government Documents Department

New Methodology For Use in Rotating Field Nuclear MagneticResonance

Description: High-resolution NMR spectra of samples with anisotropicbroadening are simplified to their isotropic spectra by fast rotation ofthe sample at the magic angle 54.7 circ. This dissertation concerns thedevelopment of novel Nuclear Magnetic Resonance (NMR) methodologies basedwhich would rotate the magnetic field instead of the sample, rotatingfield NMR. It provides an over of the NMR concepts, procedures, andexperiments needed to understand the methodologies that will be used forrotating field NMR. A simple two-dimensional shimming method based onharmonic corrector rings which can provide arbitrary multiple ordershimming corrections were developed for rotating field systems, but couldbe used in shimming other systems as well. Those results demonstrate, forexample, that quadrupolar order shimming improves the linewidth by up toan order of magnitude. An additional order of magnitude reduction is inprinciple achievable by utilizing this shimming method for z-gradientcorrection and higher order xy gradients. A specialized pulse sequencefor the rotating field NMR experiment is under development. The pulsesequence allows for spinning away from the magic angle and spinningslower than the anisotropic broadening. This pulse sequence is acombination of the projected magic angle spinning (p-MAS) and magic angleturning (MAT) pulse sequences. This will be useful to rotating field NMRbecause there are limits on how fast a field can be spun and spin at themagic angle is difficult. One of the goals of this project is forrotating field NMR to be used on biological systems. The p-MAS pulsesequence was successfully tested on bovine tissue samples which suggeststhat it will be a viable methodology to use in a rotating field set up. Aside experiment on steering magnetic particle by MRI gradients was alsocarried out. Some movement was seen in these experiment, but for totalcontrol over steering further experiments would need to bedone.
Date: May 18, 2007
Creator: Jachmann, Rebecca C.
Partner: UNT Libraries Government Documents Department

High-resolution magnetic imaging and investigations of thin-film magnetism with spin-polarized electron, ion and atom probes. Progress report, November 1, 1994--October 31, 1995

Description: This is a progress report for the period 1 November, 1994 to 31 October, 1995. Research during this grant year includes: (1) Completion of the Spin-Polarized Electron Energy Loss Spectroscopy (SPEELS) research program. (2) Design of an improved and much more intense metastable atom source that can also be converted to a Rydberg atom beam, for continuing studies utilizing Spin-Polarized Metastable (Atom) Deexcitation Spectroscopy (SPMDS), and to initiate new investigations of interactions of Rydberg atoms with surfaces. (3) Development of a spin-polarized He{sup +} ion source for studies of ion-surface interaction dynamics and epitaxially grown magnetic films utilizing Spin-Polarized Ion Neutralization Spectroscopy (SPINS).
Date: April 1, 1995
Creator: Walters, G.K. & Dunning, F.B.
Partner: UNT Libraries Government Documents Department

Diagnostic Setup for Characterization of Near-Anode Processes in Hall Thrusters

Description: A diagnostic setup for characterization of near-anode processes in Hall-current plasma thrusters consisting of biased and emissive electrostatic probes, high-precision positioning system and low-noise electronic circuitry was developed and tested. Experimental results show that radial probe insertion does not cause perturbations to the discharge and therefore can be used for accurate near-anode measurements.
Date: September 8, 2003
Creator: Dorf, L.; Raitses, Y. & Fisch, N.J.
Partner: UNT Libraries Government Documents Department

Dependence of secondary electron image contrast of periodic objects upon probe diameter

Description: The effect of probe diameter upon secondary electron image contrast of periodic objects has been studied systematically. Interest in the topic arose following the observation of out-of-focus SEM images of conventional mesh support grids, where the basic periodicity was visible even with probe diameters many times the periodic spacing. The instrument used was a JEM-120CX/ASID operated in the SEM mode at low magnification with the objective lens off and other lenses in the free-control mode. The probe diameter at the specimen position was controlled by the continuously variable second condenser lens current. The first intermediate lens was focussed at the specimen position, thus allowing a determination of the probe diameter from the magnified shadow image, which could be photographed using the conventional TEM camera. The specimen used was a copper bar grid with spacings approx. = 125 ..mu..m.
Date: January 1, 1979
Creator: Bentley, J & Carpenter, R W
Partner: UNT Libraries Government Documents Department

TiO2 Nanoparticles as a Soft X-ray Molecular Probe

Description: With the emergence of soft x-ray techniques for imaging cells, there is a pressing need to develop protein localization probes that can be unambiguously identified within the region of x-ray spectrum used for imaging. TiO2 nanocrystal colloids, which have a strong absorption cross-section within the "water-window" region of x-rays, areideally suited as soft x-ray microscopy probes. To demonstrate their efficacy, TiO2-streptavidin nanoconjugates were prepared and subsequently labeled microtubules polymerized from biotinylated tubulin. The microtubules were imaged using scanning transmission x-ray microscopy (STXM), and the TiO2 nanoparticle tags were specifically identified using x-ray absorption near edge spectroscopy (XANES). These experiments demonstrate that TiO2 nanoparticles are potential probes for protein localization analyses using soft x-ray microscopy.
Date: June 30, 2007
Creator: Larabell, Carolyn; Ashcroft, Jared M.; Gu, Weiwei; Zhang, Tierui; Hughes, Steven M.; Hartman, Keith B. et al.
Partner: UNT Libraries Government Documents Department

Physical Limitations on the Measurement of Transient Fields in Air and in Dissipative Media Using Electric and Magnetic Probes

Description: The properties of electric and magnetic probes for the measurement of transient electromagnetic fields in air and in dissipative media are discussed briefly, It is shown that the effective height of an electrically small loop is independent of the ambient medium. This is also virtually true for a thin electrically short dipole (or monopole). If the open-circuit voltage of a magnetic probe can be measured accurately, it is possible (in principle) to reconstruct the time history of the incident magnetic field, even if the loop is immersed in dissipative media of unknown characteristics. The time function of the open-circuit voltage of an electric probe is essentially a replica of the time history of the incident electric field. In some schemes, the probes are lumped impedance loaded, and the voltage drop across the load impedances is measured. The source impedances of the probes are then involved in the equivalent circuits of the receiving antennas, and the leading terms in the expressions for these impedances depend on the properties of the environment. If an electrically short monopole is base-loaded by a capacitor divider, the voltage wave appearing across any capacitor is a faithful reproduction of the time sequence of the incident electric field provided the measurement is made in air or other dielectric. (auth)
Date: November 1, 1963
Creator: Harrison, C. W., Jr.
Partner: UNT Libraries Government Documents Department

Investigations of Probe Induced Perturbations in a Hall Thruster

Description: An electrostatic probe used to measure spatial plasma parameters in a Hall thruster generates perturbations of the plasma. These perturbations are examined by varying the probe material, penetration distance, residence time, and the nominal thruster conditions. The study leads us to recommendations for probe design and thruster operating conditions to reduce discharge perturbations, including metal shielding of the probe insulator and operation of the thruster at lower densities.
Date: August 12, 2002
Creator: Staack, D.; Raitses, Y. & Fisch, N.J.
Partner: UNT Libraries Government Documents Department

External and Internal Guest Binding of a Highly Charged Supramolecular Host in Water: Deconvoluting the Very Different Thermodynamics

Description: NMR, UV-vis and isothermal titration calorimetry (ITC) measurements probe different aspects of competing host-guest equilibria as simple alkylammonium guest molecules interact with both the exterior (ion-association) and interior (encapsulation) of the [Ga{sub 4}L{sub 6}]{sup 12-} supramolecular assembly in water. Data obtained by each independent technique measure different components of the host-guest equilibria and only when analyzed together does a complete picture of the solution thermodynamics emerge. Striking differences between the internal and external guest binding are found. External binding is enthalpy driven and mainly due to attractive interactions between the guests and the exterior surface of the assembly while encapsulation is entropy driven as a result of desolvation and release of solvent molecules from the host cavity.
Date: July 22, 2009
Creator: Sgarlata, Carmelo; Mugridge, Jeffrey; Pluth, Michael; Tiedemann,, Bryan; Zito, Valeria; Arena, Giuseppe et al.
Partner: UNT Libraries Government Documents Department

Wide-field surveys from the SNAP mission

Description: The Supernova/Acceleration Probe (SNAP) is a proposed space-borne observatory that will survey the sky with a wide-field optical/NIR imager. The images produced by SNAP will have an unprecedented combination of depth, solid-angle, angular resolution, and temporal sampling. Two 7.5 square-degree fields will be observed every four days over 16 months to a magnitude depth of AB = 27.7 in each of nine filters. Co-adding images over all epochs will give an AB = 30.3 per filter. A 300 square-degree field will be surveyed with no repeat visits to AB = 28 per filter. The nine filters span 3500-17000 {angstrom}. Although the survey strategy is tailored for supernova and weak gravitational lensing observations, the resulting data supports a broad range of auxiliary science programs.
Date: July 23, 2002
Creator: agkim@lbl.gov
Partner: UNT Libraries Government Documents Department


Description: An X-ray Active Matrix Pixel Sensor (XAMPS) is being developed for recording data for the X-ray Pump Probe experiment at the Linac Coherent Light Source (LCLS). Special attention has to be paid to some technological challenges that this design presents. New processes were developed and refined to address problems encountered during previous productions of XAMPS. The development of these critical steps and corresponding tests results are reported here.
Date: October 29, 2007
Creator: CARINI,G.A.; CHEN, W.; LI, Z.; REHAK, P. & SIDDONS, D.P.
Partner: UNT Libraries Government Documents Department

Towards sub-10 nm resolution zone plates using the overlaynanofabrication processes

Description: Soft x-ray zone plate microscopy has proven to be a valuable imaging technique for nanoscale studies. It complements nano-analytic techniques such as electron and scanning probe microscopies. One of its key features is high spatial resolution. We developed an overlay nanofabrication process which allows zone plates of sub-20 nm zone widths to be fabricated. Zone plates of 15 nm outer zones were successfully realized using this process, and sub-15 nm resolution was achieved with these zone plates. We extend the overlay process to fabricating zone plates of 12 nm outer zones, which is expected to achieve 10 nm resolution. In addition, we have identified a pathway to realizing sub-10 nm resolution, high efficiency zone plates with tilted zones using the overlay process.
Date: January 23, 2008
Creator: Chao, Weilun; Anderson, Erik H.; Fischer, Peter & Kim, Dong-Hyun
Partner: UNT Libraries Government Documents Department

Temperature, Humidity, Wind and Pressure Sensors (THWAPS) Handbook

Description: The temperature, humidity, wind, and pressure system (THWAPS) provide surface reference values of these measurements for balloon-borne sounding system (SONDE) launches. The THWAPS is located adjacent to the SONDE launch site at the Southern Great Plains (SGP) Central Facility. The THWAPS system is a combination of calibration-quality instruments intended to provide accurate measurements of meteorological conditions near the surface. Although the primary use of the system is to provide accurate surface reference values of temperature, pressure, relative humidity (RH), and wind velocity for comparison with radiosonde readings, the system includes a data logger to record time series of the measured variables.
Date: January 17, 2011
Creator: Ritsche, MT
Partner: UNT Libraries Government Documents Department

3Q120 Low Gradient Behaviour-Companion Report

Description: Three 3Q120 magnets--representative of those in the AP 1 line--have been measured with a harmonics probe at MDTF at both low (0-48 A) and high (to >= 400 A). The intent of the measurements was to learn their behavior at the low gradients necessary to transport 8 Gev antiprotons back through the AP 1 line for injection into the Main Ring. This paper describes some aspects of the measurements that were not included in the main paper, in order to keep the size of the main report reasonably small. It includes as Appendix I a chronology of the measurements made and significant changes made to the measurement apparatus and analysis programs.
Date: October 1, 1985
Creator: Wehmann, A.
Partner: UNT Libraries Government Documents Department

Femtosecond isomerization dynamics in the ethylene cation measured in an EUV-pump NIR-probe configuration

Description: Dynamics in the excited ethylene cation C{sub 2}H{sub 4}{sup +} lead to isomerization to the ethylidene configuration (HC-CH{sub 3}){sup +}, which is predicted to be a transient configuration for electronic relaxation. With an intense femtosecond EUV (extreme ultraviolet) pump pulse to populate the excited state, and an NIR (near infrared) probe pulse to produce the fragments CH{sup +} and CH{sub 3}{sup +} (which provides a direct signature of ethylidene), we measure optimum fragment yields at a probe delay of 80 fs. Also, an H{sub 2}-stretch transient configuration, yielding H{sub 2}{sup +} upon probing, is found to succeed the ethylidene configuration. We find that a simple single- or double-decay model does not match the data, and we present a modified model (introduction of an isomerization delay of 50 {+-} 25 fs) that does provide agreement.
Date: March 17, 2009
Creator: van Tilborg, Jeroen; Allison, Tom; Wright, Travis; Hertlein, Marc; Falcone, Roger; Liu, Yanwei et al.
Partner: UNT Libraries Government Documents Department


Description: The 1.6 cell S-band photoinjector cavity has been in operation at the DUVFEL at BNL for the past year. Initial beam measurements indicated a higher than expected emittance and beam divergence at the exit of the gun. field imbalance in the two cells was suspected, but lack of field probes in the cavity prohibited direct confirmation. A detailed SUPERFISH model was constructed of the cavity assembly. Field balance as a function of cathode plate and tuner position was determined using the model. A series of calibrated measurements of both the cavity RF properties and the delivered RF power was undertaken. Electron beam properties were also measured as function of cavity tune. Significant improvements in beam quality were achieved. The simulations and measurements are presented.
Date: June 18, 2001
Partner: UNT Libraries Government Documents Department

Ultrabright Laser-based MeV-class Light Source

Description: We report first light from a novel, new source of 10-ps 0.776-MeV gamma-ray pulses known as T-REX (Thomson-Radiated Extreme X-rays). The MeV-class radiation produced by TREX is unique in the world with respect to its brightness, spectral purity, tunability, pulse duration and laser-like beam character. With T-REX, one can use photons to efficiently probe and excite the isotope-dependent resonant structure of atomic nucleus. This ability will be enabling to an entirely new class of isotope-specific, high resolution imaging and detection capabilities.
Date: April 2, 2008
Creator: Albert, F; Anderson, G; Anderson, S; Bayramian, A; Berry, B; Betts, S et al.
Partner: UNT Libraries Government Documents Department

High-heat flux testing of an interceptive device for an intense proton beam

Description: An interceptive device referred to here as a scraper has been designed and tested for use in a diagnostic device [1]. The scraper will be used to probe a proton beam in order to detect the formation of beam halo [2]. Probing the proton beam exposes the scraper to high heat fluxes on the order of 610 kW/cm{sup 2}. The high-heat flux exposure is cyclic since the beam is probed while in pulsed mode. In order to test the design repetitive high-heat flux testing has been performed on a prototype design of the scraper. This paper describes the design, analysis, and testing of the scraper.
Date: April 1, 2001
Creator: Valdiviez, R. (Robert); Martinez, F. A. (Felix A.); Rendon, Armando M.; Nguyen, D. C. (Dinh C.); Earley, L. M. (Lawrence M.) & La Fave, R. P. (Richard P.)
Partner: UNT Libraries Government Documents Department


Description: A test program using 241-AN-102 waste simulants and metallic secondary reference electrodes similar to those used on the 241-AN-102 MPCMS was performed to characterize the relationship between temperature and secondary reference electrode open-circuit corrosion potential. This program showed that the secondary reference electrodes can be used to make tank and tank steel corrosion potential measurements, but that a correction factor of approximately 2 mV per degree Celsius of temperature difference must be applied, where temperature difference is defined as the difference between tank temperature at the time of measurement and 30 C, the average tank temperature during the first several months of 241-AN-102 MPCMS operation (when the corrosion potentials of the secondary reference electrodes were being recorded relative to the primary reference electrodes).
Date: September 30, 2008
Partner: UNT Libraries Government Documents Department

A comparison of DNA damage probes in two HMEC lines with X-irradiation

Description: In this study, we investigated {gamma}H2AX{sup ser139} and 53BP1{sup ser25}, DNA damage pathway markers, to observe responses to radiation insult. Two Human Mammary Epithelial Cell (HMEC) lines were utilized to research the role of immortalization in DNA damage marker expression, HMEC HMT-3522 (S1) with an infinite lifespan, and a subtype of HMEC 184 (184V) with a finite lifespan. Cells were irradiated with 50 cGy X-rays, fixed with 4% paraformaldehyde after 1 hour repair at 37 C, and processed through immunofluorescence. Cells were visualized with a fluorescent microscope and images were digitally captured using Image-Pro Plus software. The 184V irradiated cells exhibited a more positive punctate response within the nucleus for both DNA damage markers compared to the S1 irradiated cells. We will expand the dose and time course in future studies to augment the preliminary data from this research. It is important to understand whether the process of transformation to immortalization compromises the DNA damage sensor and repair process proteins of HMECs in order to understand what is 'normal' and to evaluate the usefulness of cell lines as experimental models.
Date: January 19, 2007
Creator: Wisnewski, Christy L.; Bjornstad, Kathleen A.; Rosen, ChristoperJ.; Chang, Polly Y. & Blakely, Eleanor A.
Partner: UNT Libraries Government Documents Department