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Plasma Heating by Transit-Time Magnetic Pumping in Single-Transit Systems

Description: Report discussing the heating of a plasma which passes through a series of magnetic pumping cells by applying the second-order theory of transit-time heating developed by Berger and Newcomb. From abstract: "Transit-time magnetic pumping in single-transit systems seems to be a feasible method of increasing plasma energy by amounts of the order of a factor of 10."
Date: September 1956
Creator: Hall, Laurence S.; Gardner, Andrew L. & Edwards, Donald A.
Partner: UNT Libraries Government Documents Department

Power and phase monitoring system for the lower hybrid phased array heating system on ATC machine

Description: A four waveguide phased array slow wave structure has been constructed to couple microwave energy into plasma in the ATC Tokamac at Princeton. Theory has indicated that the coupling of power into the plasma column is a strong function of the imposed fourier spectrum at the antenna aperture. To optimize heating, and to verify theoretical results, a precision amplitude and phase monitoring system has been designed and constructed. The system data output is routed to an IBM 1800 computer where the fourier spectrum in n/sub parallel/ space is computed for discrete increments of time during an RF pulse. Computer output data is used to update the adjustment of transmission line parameters in between pulses. (auth)
Date: January 1, 1975
Creator: Reed, B.W.
Partner: UNT Libraries Government Documents Department

200 kW, 800 MHz transmitter system for lower hybrid heating

Description: This paper describes a new rf heating system which has just been completed and is now operational on the ATC machine. The system utilizes four UHF TV klystrons to generate at least 200 kW of power at a frequency of 800 MHz. Pulse widths can be varied from 20 $mu$sec up to 20 msec. A radar type floating deck modulator along with photo-optical transmitting and receiving devices have been incorporated into the system to provide the pulse fidelity and versatility which characterizes this equipment. Modular construction was emphasized in the design, when possible, to reduce maintenance and down time in the advent of component falilure. Hybrid combining techniques are utilized in order to provide two 100 kW feeds into the machine. (auth)
Date: January 1, 1975
Creator: Deitz, A.
Partner: UNT Libraries Government Documents Department

Development of a 2 MW CW Waterload for Electron Cyclotron Heating Systems

Description: Calabazas Creek Research, Inc. developed a load capable of continuously dissipating 2 MW of RF power from gyrotrons. The input uses HE11 corrugated waveguide and a rotating launcher to uniformly disperse the power over the lossy surfaces in the load. This builds on experience with a previous load designed to dissipate 1 MW of continuous RF power. The 2 MW load uses more advanced RF dispersion to double the capability in the same size device as the 1 MW load. The new load reduces reflected power from the load to significantly less than 1 %. This eliminates requirements for a preload to capture reflected power. The program updated control electronics that provides all required interlocks for operation and measurement of peak and average power. The program developed two version of the load. The initial version used primarily anodized aluminum to reduce weight and cost. The second version used copper and stainless steel to meet specifications for the ITER reactor currently under construction in France. Tests of the new load at the Japanese Atomic Energy Agency confirmed operation of the load to a power level of 1 MW, which is the highest power currently available for testing the load. Additional tests will be performed at General Atomics in spring 2013. The U.S. ITER organization will test the copper/stainless steel version of the load in December 2012 or early in 2013. Both loads are currently being marketed worldwide.
Date: November 9, 2012
Creator: R. Lawrence,Ives; Mizuhara, Maxwell; Collins, George; Neilson, Jeffrey & Borchard, Philipp
Partner: UNT Libraries Government Documents Department

Advanced Model for SBS of a Randomized Laser Beam and Application to Polarization Smoothing Experiments with Preformed Underdense Plasmas

Description: An advanced statistical model is presented, which describes the SBS of a randomized laser beam interacting with an underdense, expanding plasma. The model accounts for the self-focusing of speckles and for its influence on the speckles SBS reflectivity in the regime where the effect of plasma heating is important. Plasma heating has an important effect on speckle self-focusing and it decreases the SBS threshold and also decreases the SBS reflectivity. The model exhibit a good agreement with the measured SBS levels at the LULI multi-beam facility for a broad range of the laser and plasma parameters and both types of beam smoothing--RPP and PS. Both the model and the experiments confirm that the PS technique allows to control the SBS level more efficiently than RPP.
Date: June 30, 2000
Creator: Labaune, C.; Depierreux, S.; Baldis, H. A.; Huller, S; Myatt, J. & Pesme, D.
Partner: UNT Libraries Government Documents Department

Updated DIII-D experimental plan for FY-1989

Description: The program proposed here is designed to support and build toward the long-term plan put forward during 1987 for the DIII-D facility. This plan has as its ultimate goal developing sufficient understanding and predictive capability to enable the demonstration of a high beta plasma with non-inductively driven toroidal current. The early stages of this plan call for the optimization of the plasma configuration for good confinement at high beta while simultaneously developing the need rf power systems for current drive, profile control, and heating.
Date: August 1, 1989
Creator: Luxon, J.L.
Partner: UNT Libraries Government Documents Department

Slow liner fusion

Description: {open_quotes}Slow{close_quotes} liner fusion ({approximately}10 ms compression time) implosions are nondestructive and make repetitive ({approximately} 1 Hz) pulsed liner fusion reactors possible. This paper summarizes a General Atomics physics-based fusion reactor study that showed slow liner feasibility, even with conservative open-line axial magnetic field confinement and Bohm radial transport.
Date: August 1, 1997
Creator: Shaffer, M.J.
Partner: UNT Libraries Government Documents Department

Reactive gas plasma specimen processing for use in microanalysis and imaging in analytical electron microscopy

Description: It has long been the bane of analytical electron microscopy (AEM) that the use of focused probes during microanalysis of specimens increases the local rate of hydrocarbon contamination. This is most succinctly observed by the formation of contamination deposits during focused probe work typical of AEM studies. While serving to indicate the location of the electron probe, the contamination obliterates the area of the specimen being analyzed and adversely affects all quantitative microanalysis methodologies. A variety of methods including: UV, electron beam flooding, heating and/or cooling can decrease the rate of contamination, however, none of these methods directly attack the source of specimen borne contamination. Research has shown that reactive gas plasmas may be used to clean both the specimen and stage for AEM, in this study the authors report on quantitative measurements of the reduction in contamination rates in an AEM as a function of operating conditions and plasma gases.
Date: January 1997
Creator: Zaluzec, N. J.; Kestel, B. J. & Henriks, D.
Partner: UNT Libraries Government Documents Department

Cold Electronstatic Ion Cyclotron Waves for Preionization and IBW Launching in LHD

Description: A folded waveguide with E|| polarization is being installed on LHD device. The main purpose of the folded waveguide is to pre-ionize and create good target plasmas. The present manuscript proposes a launching of IBW via CESICW (Cold Electrostatic Ion Cyclotron Wave) for heating the core of LHD with the folded waveguide. The core heating can be accomplished by adding a minority hydrogen ion species in a helium majority plasma facilitating the mode-transformation of CESICW into IBW at the ion-ion hybrid resonance.
Date: April 1, 1999
Creator: Ono, Masayuki
Partner: UNT Libraries Government Documents Department

Collisionless electron heating in inductively coupled discharges

Description: A kinetic theory of collisionless electron heating is developed for inductively coupled discharges with a finite height L. The novel effect associated with the finite-length system is the resonance between the bounce motion of the electrons and the wave frequency, leading to enhanced heating. The theory is in agreement with results of particle simulations.
Date: July 1, 1996
Creator: Shaing, K.C. & Aydemir, A.Y.
Partner: UNT Libraries Government Documents Department

National Spherical Torus Experiment (NSTX)

Description: The main aim of National Spherical Torus Experiment (NSTX) is to establish the fusion physics principles of the innovative spherical torus (ST) concept. Physics outcome of the NSTX research program is relevant to near-term applications such as the Volume Neutron Source (VNS) and burning plasmas, and future applications such as the pilot and power plants. The NSTX device began plasma operations in February 1999 and the plasma current was successfully ramped up to the design value of 1 million amperes (MA) on December 14, 1999. The CHI (Coaxial Helicity Injection) and HHFW (High Harmonic Fast Wave) experiments have also started. Stable CHI discharges of up to 133 kA and 130-msec duration have been produced using 20 kA of injected current. Using eight antennas connected to two transmitters, up to 2 MW of HHFW power was successfully coupled to the plasma. The Neutral-beam Injection (NBI) heating system and associated NBI-based diagnostics such as the Charge-exchange Recombination Spectrometer (CHERS) will be operational in October 2000.
Date: April 22, 2000
Creator: Ono, Masayuki
Partner: UNT Libraries Government Documents Department

Physics results from the National Spherical Torus Experiment

Description: The National Spherical Torus Experiment (NSTX) at the Princeton Plasma Physics Laboratory is designed for studying toroidal plasma confinement at very low aspect-ratio, A=R/a = 0.85m/0.68m {approximately} 1.25, with cross-section elongation up to 2.2 and triangularity up to 0.5, for plasma currents up to 1 MA and vacuum toroidal magnetic fields up to 0.6 T on axis. Conducting plates are installed close to the plasma on the outboard side to stabilize kink modes. This should permit operation with toroidal-{beta} approaching 40%. The plasmas will be heated by up to 6 MW High-Harmonic Fast Waves (HHFW) at a frequency 30 MHz and by 5 MW of 80 keV deuterium Neutral Beam Injection. Inductive plasma startup can be supplemented by the process of Coaxial Helicity Injection (CHI).
Date: June 13, 2000
Creator: Bell, M.G.
Partner: UNT Libraries Government Documents Department

MHD stability studies in reversed shear plasmas in TFTR

Description: MHD phenomena in reversed shear plasmas in TFTR are described during each of the three phases of the evolution of these discharges: the current ramp, high power neutral beam heating and after the beam power has been reduced. Theoretical analysis of discharges which disrupted in the high-{beta} phase indicates that the {beta} - limit is set by the ideal n = 1 infernal/kink mode. The mode structure of the disruption precursor reconstructed from the electron temperature data compares favorably with the predicted displacement vector from the ideal MHD model. In contrast, disruptions during the early and late phases are due to resistive instabilities, double tearing modes coupled to high-m edge modes. The resistive interchange mode, predicted to be unstable in reversed shear plasmas, is not seen in the experiment. Neo-classical tearing mode theory is shown to describe the non-disruptive MHD phenomena. A nonlinear resistive MHD simulation reproduces off-axis sawtooth-like crashes during the post-beam phase. The dependence of the {beta}-limit on the pressure peakedness and q{sub min} is discussed, showing a path to stable higher-{beta} regimes.
Date: December 31, 1996
Creator: Manickam, J.; Fredrickson, E. & Chang, Z.
Partner: UNT Libraries Government Documents Department

Observation of modes at frequencies near the second Alfven gap in TFTR

Description: Modes have been observed near the frequency of the second Alfven gap during off-axis H-minority heating experiments in the circular cross-section Tokamak Fusion Test Reactor. The observation of these modes is surprising in that the second gap, which is generally opened with ellipticity, is expected to be small, of order (r/R){sup 2}. A model is proposed in which the second gap is opened by the fast ion beta, which is shown to be able to introduce mode coupling, much as toroidal effects introduce mode coupling for Toroidal Alfven Eigenmodes (TAE). The modes are seen with and without accompanying TAE mode activity.
Date: April 26, 2000
Creator: Fredrickson, E.; Van Dam, J.W.; Budny, R.V.; Darrow, D.; Fu, G.Y.; Hosea, J. et al.
Partner: UNT Libraries Government Documents Department

First results on fast wave current drive in advanced tokamak discharges in DIII-D

Description: Initial experiments have been performed on the DIII-D tokamak on coupling, direct electron heating, and current drive by fast waves in advanced tokamak discharges. These experiments showed efficient central heating and current drive in agreement with theory in magnitude and profile. Extrapolating these results to temperature characteristic of a power plant (25 keV) gives current drive efficiency of about 0.3 MA/m{sup 2}.
Date: July 1, 1995
Creator: Prater, R.; Cary, W.P. & Baity, F.W.
Partner: UNT Libraries Government Documents Department

Extrapolation of the Dutch 1 MW tunable free electron maser to a 5 MW ECRH source

Description: A Free Electron Maser (FEM) is now under construction at the FOM Institute (Rijnhuizen) Netherlands with the goal of producing 1 MW long pulse to CW microwave output in the range 130 GHz to 250 GHz with wall plug efficiencies of 50% (Verhoeven, et al EC-9 Conference). An extrapolated version of this device is proposed which by scaling up the beam current, would produce microwave power levels of up to 5 MW CW in order to reduce the cost per watt and increase the power per module, thus providing the fusion community with a practical ECRH source.
Date: April 1, 1995
Creator: Caplan, M.; Nelson, S.; Kamin, G.; Antonsen, T. Levush, B.; Urbanus, W. & Tulupov, A.
Partner: UNT Libraries Government Documents Department

Magnetic confinement experiment. I: Tokamaks

Description: Reports were presented at this conference of important advances in all the key areas of experimental tokamak physics: Core Plasma Physics, Divertor and Edge Physics, Heating and Current Drive, and Tokamak Concept Optimization. In the area of Core Plasma Physics, the biggest news was certainly the production of 9.2 MW of fusion power in the Tokamak Fusion Test Reactor, and the observation of unexpectedly favorable performance in DT plasmas. There were also very important advances in the performance of ELM-free H- (and VH-) mode plasmas and in quasi-steady-state ELM`y operation in JT-60U, JET, and DIII-D. In all three devices ELM-free H-modes achieved nT{tau}`s {approximately} 2.5x greater than ELM`ing H-modes, but had not been sustained in quasi-steady-state. Important progress has been made on the understanding of the physical mechanism of the H-mode in DIII-D, and on the operating range in density for the H-mode in Compass and other devices.
Date: August 1, 1995
Creator: Goldston, R.J.
Partner: UNT Libraries Government Documents Department

Enhanced Electron Attachment to Highly-Excited States of Molecules: Implications for Plasma Processing Discharges

Description: Recent studies show that large negative ion densities exist in plasma processing discharges, including those of weakly electronegative gases such as SiH{sub 4} and CF{sub 4}. Also, there is strong evidence that the negative ions could be the precursors for particulate formation in processing discharges. Even though it is now well established that large concentrations of negative ions exist in processing discharges, and that they play a crucial role in such discharges, the source of such high negative ion densities has not been clarified. In particular, gases like SiH{sub 4} and CH{sub 4}, which are commonly used in processing discharges, attach electrons only weakly in their ground electronic states (see the references). Due to the lack of an alternative mechanism, the origin of large negative ion densities in such weakly electronegative gases has been frequently attributed to electron attachment to radicals (molecular fragments) or other byproducts produced in the discharge. This hypothesis had not been tested in direct electron attachment measurements.
Date: June 29, 1998
Creator: Datskos, P.G.; Ding, W.; McCorkle, D.L. & Pinnaduwage, L.A.
Partner: UNT Libraries Government Documents Department