Bulletin of the American Physical Society
2006 APS April Meeting
Saturday–Tuesday, April 22–25, 2006; Dallas, TX
Session W15: Poster Session IV: Post-deadline Posters |
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Room: Hyatt Regency Dallas Marsalis Hall B, 10:30am-2:00pm |
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W15.00001: Search for Ultra High Energy Neutrinos with AMANDA-II Lisa Gerhardt AMANDA-II is a large volume neutrino telescope, designed to measure the energetic neutrino flux from astrophysical sources. A search for neutrinos exceeding 1 PeV has been performed using data collected by AMANDA-II in 2000. At these energies, the Earth is opaque to neutrinos. This, combined with the limited overburden above the detector, concentrates the expected signal at the horizon. A method of separating signal from the background of high energy downward going air showers has been developed and the results are discussed. [Preview Abstract] |
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W15.00002: Neutrino Search and Performance of AMANDA-II using Transient Waveform Recorders Andrea Silvestri AMANDA-II data acquisition electronics was upgraded in January 2003 to readout the complete waveform from the buried PMTs using Transient Waveform Recorders (TWR). We perform the same atmospheric neutrino analysis on data collected in 2003 by the TWR and standard AMANDA data acquisition system. Good agreement in event rate and angular distribution verify the baseline performance of the TWR system. A search of the northern hemisphere for localized neutrino event clusters is also performed, no statistical significant excess has been observed. [Preview Abstract] |
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W15.00003: Report on the search for binary black holes inspiral in S3 and S4 LIGO data Thomas Cokelaer We report on the search for gravitational waves emitted by non-spinning binary black hole inspirals in data taken during the third and fourth LIGO science runs (S3 and S4). We give an overview of the data taken during these sciences runs as well as the target waveforms that we are searching for in this analysis. We briefly describe how the data is filtered and emphasize the difficulties of the search. We report on the status of these searches and prospects for similar searches over the next few years. [Preview Abstract] |
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W15.00004: Search for Gravitational Waves associated with the SGR1806-20 hyperflare using the Hanford LIGO detectors Luca Matone On Dec.27th, 2004, SGR1806-20 emitted a record flare; at the time of the event the Hanford (WA) H1 LIGO detector was in operation. We present the status of the search for gravitational-wave emission associated with this extraordinary event. [Preview Abstract] |
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W15.00005: Galaxy mass distributions without dark matter or modified Newtonian mechanics Kenneth Nicholson Given the galaxy dimensions (including thickness) and rotation profile, a method is arranged to find the mass and density distribution in the defined envelope that will cause that rotation profile with near-exact speed matches. Newton's law is unchanged. Surface-light intensity or dark matter are not needed. Errors in previous methods are discussed. Thickness is considered important and some useful thickness distributions are shown that account for an exponential ``atmosphere.'' Equation development and proof of equations are shown for the forward problem (rotation profile from mass distribution). Also it is shown that the acceleration at the rim of a constant-SMD flat disk is nearly 3 times that of a sphere of the same mass and radius. With the reverse problem (mass distribution from rotation profile) results for several galaxies are presented in dimensionless plots allowing easy comparisons. Total mass results for galaxies are about 2/3 those found using dark-matter spheres. [Preview Abstract] |
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W15.00006: Impact of Gravitational Variations on Aging Shantilal Goradia Einstein's 1919 removal of the cosmological constant as a consequence of his analysis suggests a synonymy between gravitation and nuclear force, which is complimentary and supplementary to my suggestion of the synonymy between nuclear force and gravitation supporting the inflationary universe in version 2 of http://www.arXiv.org/physics/0210040 and vice versa. In version 1 of the same article, I am going a step deeper to suggest that all coupling constants are increasing with time consistent with Dirac's LNH and an observation that the universal constant of gravity is decreasing with time. The variations of coupling constants must inevitably impact the binding energy of organic particles resulting in an impact on the chemical energy output of the power plants of biological cells (DNA of Mitochondria). The web site http://home.comcast.net/$\sim $neardeath/science/001{\_}pages/28.htm'' suggests a link between such energy outputs and aging. If the changes in the chemical energy output can be compensated by some means, it may be possible to reverse the aging process. This makes it important to establish weather the universal constant of gravity is changing as once reported. Gravity cannot be discounted as weak as done in the past, because the coupling constants it generates are not weak, nor fixed. [Preview Abstract] |
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W15.00007: Simultaneous Detection and Classification of Acoustic Emissions in Integrated Diagnostics with Yield in Aluminum Devendra Parmar Acoustic emission (AE) experiments were conducted on a strained aluminum (10 cm x 9 cm x 0.25 cm) specimen. Studies were conducted with the goal to characterize AE associated with material yield developed due to high loading and to correlate the course of the yield with AE signals. The American Association of State Highway and Transport Officials (AASHTO) listed aluminum as one of the structural components of highway brides$^{1 }$with unit weight of 2800 kg.m$^{-3}$. The specimen, mounted on the load frame, was held on each end by the wedge grips and was electromechanically tested in a tension mode at rates of extension of 0.0333 mm/s and 0.0666 mm/s. Load was applied to the test frame via moving cross heads. A load transducer (load cell) mounted in series with the specimen measured the applied load by converting it into an electrical signal. Results are analyzed using defect zone model in which location of the defect is determined from the measurement of the arrival time of the signal at two different sensors placed at strategically around the source of emission from the test object. The sensor that detects the signal first is identified to be in the defect zone. $^{1}$AASHTO LRFD Bridge Design Specifications, 1994. [Preview Abstract] |
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W15.00008: Color screening in Quark-Gluon plasma at low and high temperatures Olaf Kaczmarek, Frithjof Karsch, Peter Petreczky, Felix Zantow Using quark antiquark free energies we define different length scales which describe the screening length in hot QCD. We find that these length scales drop rapidly in the vicinity of the phase transition and indicate distances which are about twice as large than the inverse Debye mass found in earlier studies. On the one hand our results show no or only little differences when changing from quenched to $2$-flavor QCD. On the other hand our analysis supports recent findings that indicate that $J/\Psi$ will show significant medium modifications only at temperatures well above $T_c$. [Preview Abstract] |
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W15.00009: The WARP program for Direct WIMP Dark Matter Search. Results from the operation of a 2.3 liter detector prototype in Gran Sasso Cristiano Galbiati The WARP detector is characterized by a unique technology for the identification of nuclear recoils, eventually induced by WIMPs' interactions with argon. The detection technique takes advantage of a double discrimination between argon recoils and gamma or beta induced background, providing a discrimination power against betas potentially in excess of one event over 10$^{8}$. The 100 liter (140 kg) detector, presently under construction and to be commissioned during the second half of 2006, will be also equipped with an active shield for identification and rejection of neutron induced recoils. A 2.3 liter volume prototype (3 kg active mass, 1.8 kg fiducial mass) is installed in Gran Sasso since May 2004 and was run underground in several operating conditions: with and without gamma shielding, with and without neutron shielding. Our measurements confirm the discrimination power indicated above. I will present results on the characterization of the background. I will also present results of a run for direct search of WIMP Dark Matter, with the complete neutron and gamma shielding, in which a total exposure of about 80 kg$\cdot $day was accumulated. [Preview Abstract] |
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W15.00010: Generating Scale-invaraint Power Spectrum in String Gas Cosmology Ali Nayeri, Robert Brandenberger, Cumrun Vafa We study the generation of cosmological perturbations during the Hagedorn phase of string gas cosmology. Using tools of string thermodynamics we provide indications that it may be possible to obtain a nearly scale- invariant spectrum of cosmological fluctuations on scales which are of cosmological interest today. In our cosmological scenario, the early Hagedorn phase of string gas cosmology goes over smoothly into the radiation-dominated phase of standard cosmology, without having a period of cosmological inflation. Furthermore, we find that string thermodynamics implies that the fluctuations are Gaussian, and that the spectrum of tensor perturbations will exhibit a scale-invariant spectrum as well. We contrast the predictions of string gas cosmology in the Hagedorn phase with that of scalar field driven inflation, and comment on the possibility of observationally distinguishing between the two scenarios in future experiments. [Preview Abstract] |
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W15.00011: Global Guiding-Center Particle Simulation of minority ICRH heated Plasmas in a Tokamak Jae-Min Kwon, C.S. Chang, S. Ku, D. McCune, C.K. Phillips A global numerical simulation of RF heating of a multi-species kinetic plasma has been performed using a particle-in-cell guiding center code in tokamak geometry. The resonant minority ion species interacts with a prescribed rf wave and with the main ions, collisionally exchanging momentum and energy. The majority ions interact with each other collisionally (conserving momentum and energy) and with the minority ions. Generation of a global radial electric field and plasma rotation are evaluated self-consistently with the rf interaction and Coulomb collisions. It is found that the RF-driven radial transport can induce radial electric field and rotation profiles that significantly exceed the conventional neoclassical level for moderate RF-power. High field side heating produces a significantly greater flow shear than central and low field side heating in these simulations. Finite orbit excursion effects play an important role in producing these results. Detailed analysis of the observed phenomena using the time evolution of ion distribution functions will be presented. Coupling with a wave code and application of the technology to the NUBEAM Monte Carlo code will also be discussed. [Preview Abstract] |
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W15.00012: Prospects for Measuring Neutrino-Nucleus Coherent Scattering at a Stopped-Pion Neutrino Source Kate Scholberg Coherent neutral current neutrino-nucleus elastic scattering has never been observed. Although the cross-section is very high, nuclear recoil energies are very small. However, detection of the process may be within the reach of the new generation of low-threshold detectors. A promising prospect for the first detection of this process is an experiment at a high flux stopped-pion neutrino source such as the SNS. I will present some preliminary rate calculations and discuss sensitivity of such a measurement to new physics. [Preview Abstract] |
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W15.00013: Properties of the Generalized Kodama States Andrew Randono The original incarnation of the Kodama/Chern-Simons State of canonical quantum gravity employs a restriction of the phase space to self-dual connections thereby fixing the Immirzi parameter at the unit imaginary, $\gamma=i$. We recently proposed a generalization of the state for arbitrary values of the Immirzi parameter and gave strong evidence to suggest that the generalized state is also a solution to the Hamiltonian constraint of canonical quantum gravity. We suggested that for real values of $\gamma$, the generalized state is CPT invariant, delta-function normalizable, and invariant under large gauge transformations. Follow-up investigations have revealed that the state can be written as the exponent of the second Chern class minus the Euler charactersitic, pulled back to a 3-dimensional spacelike boundary, thereby yielding an intrinsically 4-dimensional definition and an intimate connection with known topological field theories. Furthermore, the state has a simple semi-classical interpretation as the WKB state corresponding to spacetimes with constant 4-curvature. There is an infinite family of such spacetimes each characterized by the equivalence class of 3-curvatures modulo gauge transformations and diffeomorphisms, $R$. To each of these classical spacetime configurations there exists a generalized Kodama state $|\psi_R>$. A formal argument shows that these states are expected to be orthogonal with respect to a natural inner product: $<\psi_R'| \psi_R>=\delta (R'-R) $. [Preview Abstract] |
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W15.00014: Event Shapes at the Tevatron Lester Pinera, Andrey Korytov, Alexander Pronko We present a complementary set of ``Indirectly Global Event Shapes'' proposed for study at hadron colliders. These observables are designed to reconcile the seemingly conflicting theoretical requirement of ``globalness'' with the realities of the hadron collider environment--namely, the limited detector coverage in the forward region. Of particular interest is the study of event shape distributions as a means of understanding non-perturbative hadronization effects. Specifically, these are considered within the Dokshitzer-Marchesini-Weber (DMW) analytical model of power corrections. We present a preliminary account of two observables, the central transverse thrust and thrust minor, as measured using the CDF detector at the Tevatron. [Preview Abstract] |
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W15.00015: Nonlinear Evolution of the Tearing Mode Nuno Loureiro, Steve Cowley, William Dorland, Malcolm Haines, Alexander Schekochihin We present recent numerical results on the nonlinear evolution of the strongly and weakly driven resistive tearing mode. Slab geometry is adopted and the equations of reduced-MHD (RMHD) are used. A high-resolution numerical scan of the parameter space $(\Delta',\eta)$ shows that, in general, the tearing mode evolves through five stages: exponential growth, algebraic growth (Rutherford stage), $X$-point collapse followed by current-sheet exponential reconnection (Sweet--Parker stage), tearing instability of the current sheet (generation of secondary islands), and saturation. The $X$-point collapse occurs at a critical island width that scales as $Wc\sim 1/\Delta'$. During the collapse, reconnection proceeds with a rate $\propto\eta^{1/2}$. The resulting current sheet becomes unstable if it has a length-to-width ratio that exceeds a certain critical value. Secondary islands are then formed, the evolution of which occurs in a self-similar way to the original perturbation. At low $\Delta'$, the saturation amplitude is shown to be in good agreement with recent analytic theories. At large $\Delta'$ we show that the saturated amplitude depends on the existence of a previous collapse. [Preview Abstract] |
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W15.00016: Challenges and Issues of Radiation Damage Tools for Space Missions Ram Tripathi, John Wilson NASA has a new vision for space exploration in the 21st Century encompassing a broad range of human and robotic missions including missions to Moon, Mars and beyond. Exposure from the hazards of severe space radiation in deep space long duration missions is `the show stopper.' Thus, protection from the hazards of severe space radiation is of paramount importance for the new vision. Accurate risk assessments critically depend on the accuracy of the input information about the interaction of ions with materials, electronics and tissues. A huge amount of essential experimental information for all the ions in space, across the periodic table, for a wide range of energies of several (up to a Trillion) orders of magnitude are needed for the radiation protection engineering for space missions that is simply not available (due to the high costs) and probably never will be. In addition, the accuracy of the input information and database is very critical and of paramount importance for space exposure assessments particularly in view the agency's vision for deep space exploration. The vital role and importance of nuclear physics, related challenges and issues, for space missions will be discussed, and a few examples will be presented for space missions. [Preview Abstract] |
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W15.00017: Implementation and Effects of Fluctuations in Heavy Ion Reactions Malgorzata Zielinska-Pfabe, Alexis Knaub, Selamnesh Nida, Virgil Baran, Maria Colonna, Massimo Di Toro, Hermann Wolter Collisions between heavy ions have been studied within the semi-classical mean field formalism (BUU/BNV). The effects of the neglected higher order terms were included as a fluctuation of the distribution function. Two methods of implementing these fluctuations were considered. In the first method, one assumes a local thermal equilibrium and determines the variances of the density distribution. The density fluctuations are introduced randomly, according to these variances. In a second approach, a gauged numerical noise serves as an origin of fluctuations. The way in which the mean field evolves the fluctuations, depends on the stability of the system. A test particle method was used to solve the BUU equation. The calculations were performed for the Sn+Sn collisions at 50 MeV per nucleon at the impact parameters of 2 and 6 fm. Several obserables were considered: charge distribution of the observed fragments, charge asymmetry of the fragments, their kinetic energy and velocities, light particle yields, and time evolution of the number of prodced fragments. The two methods of introducing fluctuations lead to quite similar results. There are, however, minor differences in the dynamical evolution of some of the observables. [Preview Abstract] |
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W15.00018: Magnetic Islands Stabilization by Plasma Compressibility Effects in a Tokamak A.I. Smolyakov, X. Garbet, M. Ottaviani It is shown that the stability of rotating magnetic islands in a tokamak plasmas is affected by plasma compressibility related to the geodesic curvature in inhomogeneous magnetic field. A robust stabilizing contribution has been found to the Rutherford evolution equation. It is suggested that this mechanism is responsible for the instability threshold for neoclassical tearing modes. [Preview Abstract] |
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W15.00019: A search for Signatures of Dark Matter with AMS-01 Sa Xiao, Gray Rybka, Gianpaolo Carosi, Peter Fisher, Feng Zhou Weakly Interacting Massive Particles (WIMPs) are one of the possible candidates of cold dark matter. A general feature of many of these WIMP candidates, such as the supersymmetric neutralino, is that they are Majorana particles (equal to their own antiparticle) and can annihilate to stable standard model particles such as electrons, protons, etc. These annihilation products can give rise to anomalous features in the otherwise smooth charged cosmic ray spectra. We search for such features in the charge Z=-1 spectra (electrons and antiprotons) of AMS-01. We use DarkSUSY to predict the annihilation channels given certain suppersymmetric models and then use PYTHIA to determine the spectra of the decay products (electrons and antiprotons). We then use the galactic propagation software GALPROP to determine the spectra after propagation given various plausible propagation models, and study the uncertainty in our final dark matter annihilation search induced by propagation effect. [Preview Abstract] |
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W15.00020: Status of the XENON Direct Dark Matter Detection Experiment Richard Hasty The XENON collaboration is developing a dark matter detector using liquid xenon (LXe) as the target medium for detecting Weakly Interacting Massive Particles (WIMPs). The goal of the collaboration is to operate an array of LXe time projection chambers (TPCs) with 1000 times greater sensitivity to WIMPs than current direct dark matter detection experiments. Recent measurements by members of the XENON collaboration demonstrate the promise of the LXe TPC approach, particularly measurements of the scintillation efficiency and charge extraction from nuclear recoils in LXe. The collaboration is currently installing a 10 kg fiducial volume prototype in the Gran Sasso National Laboratory in Italy for low background operation. [Preview Abstract] |
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W15.00021: Study of Avalanche Photodiodes as photosensors for liquid xenon scintillation light Peter Shagin, Roman Gomez, Uwe Oberlack, Richard Farrell , Mickel McClish, Pricilla Cushman, Brian Sherwood We report on measurements with large area Avalanche Photodiodes (APD) as photodetectors for the ultraviolet scintillation light of liquid xenon (LXe). The APD, fabricated by Radiation Monitoring Devices Inc., was mounted inside the LXe detector, and scintillation light produced by Po-210 alpha particles was measured for a wide range of voltages and temperatures between 167 K and 178 K. The dark current of the cooled APDs is much reduced, and a maximum stable gain of 5600 was achieved. Based on a Monte Carlo simulation for the scintillation light collection, the quantum efficiency of the APD was estimated to be 34\% at 175 nm. We performed quantum efficiency scans of the APD at UV and optical wavelengths at room temperature to evaluate the uniformity of the response. The high quantum efficiency and gain of the APD, together with its compactness, relatively large area ($\sim 1$~cm$^2$), and the favorable ratio of active to passive sensor area, make it an interesting alternative to PMTs for UV photon sensing in LXe detectors, especially for experiments requiring a high light yield. Possible applications include positron emission tomography, neutralino dark matter search, or Compton Telescopes for gamma-ray astronomy. [Preview Abstract] |
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W15.00022: Broadband generation produced in Raman-active crystals by two- and three-color femtosecond laser pulses Miaochan Zhi, Dmitry Pestov, Xi Wang, Robert Murawski, Alexei Sokolov We observe broadband generation by non-collinearly focusing two- or three-color ultrashort laser pulses into Raman-active crystals.~ The generated spectrum extends from infrared to ultraviolet, and consists of discrete spatially-separated Raman sidebands. Up to 20 sidebands are observed when two-color fs-laser pulses interact with PbWO4 crystal.~ Similar generation is observed in diamond.~ By applying the third probe beam, about 50 sidebands are generated through the Raman-resonant four wave mixing.~ By looking at the coherent Stokes and anti-Stokes signal with delayed probe pulse, we can see that multiple Raman levels are excited by the short (50 fs) pulses used.~ Combining the multiple generated sidebands may prove to be a way to synthesize subfemtosecond pulses. [Preview Abstract] |
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W15.00023: Delta Radiative Decay in the MiniBooNE Experiment Laura Gladstone The MiniBooNE experiment at Fermilab is a $\nu_\mu \rightarrow \nu_e$ oscillation search. A signal event (an electron and excited neucleon from a neutrino which oscillated) is expected only a few hundered times thoughout the neutrino run. The rare radiative decay of the delta resonance occurs with similar frequency. It is similarly identified by an electromagnetic signal, in this case from photon conversion, and an excited nucleon. [Preview Abstract] |
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W15.00024: Multimode Analysis of SHG Signal from Complex Biological Systems: Parameterization of Regional and Global Features Using Nearest-Neighbor Analysis and Wavelet Transforms Karen Reiser, MD, Clayton Bratton We have developed a novel computational approach for quantifying structural disorder in biomolecular lattices with nonlinear susceptibility based on analysis of polarization-modulated second harmonic signal. Transient, regional disorder at the level of molecular organization is identified using a novel signal processing algorithm sufficiently compact for near real-time analysis with a desktop computer. Global disorder within the biostructure is assessed using a two-dimensional wavelet transform of the magnitude and phase of the second harmonic signal. Selection of coefficients and the specific wavelet family~~is based on topological considerations. Experimental results suggest our signal processing method represents a robust, scaleable tool that allows us to detect both regional and global alterations in signal characteristics of biostructures with a high degree of discrimination. [Preview Abstract] |
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W15.00025: Plasma Cleaning Gold Nanorods to Make Better Biosensors Peter Scully, Jason Hafner This study seeks to improve the efficacy of gold nanorods for use as biosensors.~ Noble metal particles have optical properties that differ from the bulk medium, in particular, they exhibit strong absorbance of light at certain wavelengths.~ The wavelength at which this occurs depends upon the dielectric properties of both the particles and the medium.~ This opens up the possibility of using these nanoparticles as biological sensors.~ The binding of molecules in the vicinity of a noble metal nanoparticle causes a change in the medium dielectric which can be detected by a peak shift in the absorption spectrum of the particles.~ We believe the mPEG-SH, a stabilizing agent, is lowering the sensitivity of the dielectric dependence and that by removing the mPEG-SH, sensitivity can be increased. [Preview Abstract] |
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W15.00026: Large Lepton EDM from Heavy Right Handed (Majorana) Neutrinos Saifuddin Rayyan CP violation in the leptonic sector has not been observed yet. Very strong constraints come from the current limits on the electric dipole moment (EDM) of the electron (and muon). In the recent model proposed by Takeuchi and others to explain the NuTeV anomaly, TeV Heavy Right Handed Neutrinos (HRHN's) mix heavily with the standard model neutrinos in a specific sea-saw like texture. Among the phenomenological consequences of this model is the possibility of a large CP violation in the leptonic sector. The Majorana nature of the (HRHN) results in new (two loop) diagrams leading to non-zero CP violation. The large mixing of the HRHN's can result in a huge enhancement to the value of CP violation and lepton EDM produced by these diagrams. The result of the calculation of the diagrams will be presented. The value of the predicted EDM will be discussed for different ranges of parameters and the most recent limits on the electron and muon EDM will be used to constrain the model. [Preview Abstract] |
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W15.00027: Simulations of Edge Localized Modes and Pellet Injection Ravi Samtaney We present preliminary results of 3D adaptive mesh refinement (AMR) simulations of edge localized modes (ELMs) and pellet injection, both of which are critical for ITER. It is widely accepted that the most like fueling technique for ITER will be via pellet injection; and that the high confinement mode (H-mode) operation of ITER will be accompanied by ELMs. The two application discussed above are related because pellets have been utilized to control the ELM frequency. Furthermore it is known that pellets can be associated with transitions from the low confinement mode to H-mode, as well as the occurrence of neoclassical tearing modes. In this presentation, we discuss the planned development of an AMR code which will be utilized for pellet injection and the simulations of ELMs. Both phenomena entail extremely fine resolution in the regions of interest, which necessitates the use of AMR meshing technologies. For ELM simulations, a semi-implicit approach is developed to model the vacuum region as a high-resistivity low-temperature plasma. The pellet injection problem poses interesting numerical challenges which stem from the large density gradients in the vicinity of the pellet, the large disparity between the pellet and device size, and the non-local electron heat transport. Generalized upwinding techniques are employed to deal with sharp gradients while the electron heat transport is modeled by a semi-analytical kinetic treatment [1]. Preliminary simulation results of both pellet injection and ELMs will be presented along with a discussion of the planned future work in this areas. [1] R. Ishizaki et al. Phys. Plasmas, 11:4064--4080, 2004. [Preview Abstract] |
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