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Waveguide and loop coupling to fast MHD toroidal eigenmodes

Description: Heating of plasmas by wave techniques requires an effective method of coupling rf energy to the plasma. In cavities the presence of weakly damped eigenmodes will enhance the loading of antennas when the wave frequency equals an eigenmode frequency. This report considers two methods of coupling to fast MHD eigenmodes in a toroidal cavity: one is by a waveguide mounted perpendicular to the vacuum vessel wall; and the other by a loop placed within the cavity. (auth)
Date: December 1, 1975
Creator: Paoloni, F.J.
Partner: UNT Libraries Government Documents Department

Fusion reactivities and neutron source characteristics of beam-driven toroidal reactors with both D and T injection

Description: The reactor performance is considered for intensely beam-driven tokamak plasmas with 50:50 D-T composition maintained by neutral-beam injection of both D and T, together with plasma recycling. The D and T are injected with equal intensity and velocity. This mode of operation is most appropriate for high-duty- factor, high-power-density operation, in the absence of pellet injection. The isotropic velocity distributions of energetic D and T ions (for multi-angle injection) are calculated from a simple slowing-down model, but include a tail above the injection velocity. The neutron source characteristics are determined from fusion reactivities calculated for beam-target, hot-ion, and thermonuclear reactions. For conditions where Q approximates 1, beam-target reactions are dominant, although reactions among the hot ions contribute substantially to P/sub fusion/ when n/sub hot//n /sub e/ greater than or equal to 0.2. (auth)
Date: January 1, 1976
Creator: Jassby, D.L. & Towner, H.H.
Partner: UNT Libraries Government Documents Department

High frequency parametric wave phenomena and plasma heating: a review

Description: A survey of parametric instabilities in plasma, and associated particle heating, is presented. A brief summary of linear theory is given. The physical mechanism of decay instability, the purely growing mode (oscillating two-stream instability) and soliton and density cavity formation is presented. Effects of density gradients are discussed. Possible nonlinear saturation mechanisms are pointed out. Experimental evidence for the existence of parametric instabilities in both unmagnetized and magnetized plasmas is reviewed in some detail. Experimental observation of plasma heating associated with the presence of parametric instabilities is demonstrated by a number of examples. Possible application of these phenomena to heating of pellets by lasers and heating of magnetically confined fusion plasmas by high power microwave sources is discussed. (auth)
Date: November 1, 1975
Creator: Porkolab, M.
Partner: UNT Libraries Government Documents Department

Self-consistent microwave plasma heating rates

Description: Under conditions within a hot overdense plasma corona where the field frequency is much less than the electron plasma frequency and the field period is much less than the hydrodynamic expansion time it is shown that electron field reversal heating can exceed the combined classical heating rates due to inverse bremsstrahlung (skin effect) and field pressure (PdV) by a factor approximately v/ sub e//2v/sub i/ (half the ratio of electron and ion thermal velocities). In particular this rate can exceed the inertial expansion cooling rate at a collisionless corona density of approximately 1 percent solid core density and could be realized experimentally at core temperatures approximately 3--5 keV and microwave field intensities approximately 1 MG. (auth)
Date: October 1, 1975
Creator: Ensley, D.L. & White, R.H.
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

Preliminary study of suprathermal alpha particle heating

Description: Some of the consequences of the suprathermal orbits on particle confinement and heating are examined. The guiding-center approximation along with the conservation equations of energy, magnetic moment, and canonical angular momentum were used in the analysis. An example calculation is presented. (MOW)
Date: January 1, 1975
Creator: Miley, G.H.; Petrie, T.W.; Rao, M.P. & Hively, L.H.
Partner: UNT Libraries Government Documents Department

Suppression of heavy impurities in the ST Tokamak

Description: Two different discharges in the ST Tokamak are described: A discharge dominated by high-Z (iron) impurity (Case A), and one dominated by low-Z (oxygen) impurity (Case B). The oxygen-dominated discharge shows higher electron temperature and longer containment time than the iron-dominated discharge. Suppression of Fe and Mo impurities has been achieved by pulsing in air for a few hundred shots. (auth)
Date: December 1, 1975
Creator: Meservey, E.; Bretz, N.; Dimock, D. & Hinnov, E.
Partner: UNT Libraries Government Documents Department

Plasma containment in a toroidal bicusp (tormac)

Description: The stable confinement of a fully ionized, high-beta plasma in a toroidal bicusp (Tormac) is discussed. The bicusp geometry is described along with ''shaker'' heating by magnetoacoustic waves propagating orthogonal to the internal toroidal magnetic field. (MOW)
Date: August 1, 1975
Creator: Levine, M.A.; Brown, I.G. & Gallagher, C.C.
Partner: UNT Libraries Government Documents Department

Some physics considerations for TEPR designs

Description: A simplified version of the Oak Ridge Tokamak Transport Code is used to assess the implications of confinement scaling, impurity trapping of neutral beam particles and plasma currents driven by neutral injection. The ORNL, ANL and GAC experimental power reactor reference designs are considered. (auth)
Date: January 1, 1975
Creator: Hogan, J.T.; Rome, J.A.; McAlees, D.G. & Attenberger, S.E.
Partner: UNT Libraries Government Documents Department

Laser light absorption with density profile modifications

Description: Two-dimensional computer simulations studied plasma heating by electron plasma waves. The results emphasize the importance of nonlinear steepening of the density profile near the critical density. A typical simulation result is presented in order to illustrate these profile modifications. It is shown that large dc magnetic field generation is an inherent property of the absorption of obliquely-incident light. (MOW)
Date: December 1, 1974
Creator: Kruer, W.; Valeo, E.; Estabrook, K.; Langdon, B. & Lasinski, B.
Partner: UNT Libraries Government Documents Department

Impurity transport in a quiescent tokamak plasma

Description: Short bursts of aluminum were injected into the Adiabatic Toroidal Compressor (ATC) Tokamak, and measured the time evolution of the radial distributions of highly ionized states of aluminum. The results are compared with a computer code describing neoclassical impurity diffusion and good agreement is found. (auth)
Date: October 1, 1975
Creator: Cohen, S.A.; Cecchi, J.L. & Marmar, E.S.
Partner: UNT Libraries Government Documents Department

Monte Carlo simulation of neutral beam injection into fusion reactors

Description: Motivations and techniques for the Monte Carlo computer simulation of energetic neutral beam injection for fusion reactors are described. The versatility of this approach allows a significantly more sophisticated treatment of charge transfer collision phenomena and consequent effects on engineering design than available from prior work. Exemplary results for a mirror Fusion Engineering Research Facility (FERF) are discussed. (auth)
Date: September 15, 1975
Creator: Miller, R.L.
Partner: UNT Libraries Government Documents Department

R.F. heating near the lower hybrid frequency in the FM-1 spherator

Description: Plasma heating experiments at frequencies near the lower hybrid frequency have been carried out at modest powers (.05 to 4kW). The antenna structure operating at 68 MHz was comprised of two plates driven out of phase on the exterior of the plasma. High electron heating efficiency (greater than 40 percent) in both helium and argon plasmas was observed with only a weak density dependence. At low densities (n/sub e/ less than or equal to 1 x 10$sup 11$ cm$sup -3$), the heating was uniform across the plasma while at higher densities the heating was preferentially on the exterior portion of the plasma. The heating of the exterior of the plasma was found not to correspond to absorption at the lower hybrid resonance layer. The electron heating efficiency was found to be a weak function of rf power when the incident rf power was varied from 1 to 15 times the experimentally observed threshold power for parametric instabilities. Ion temperatures were determined by measuring the Doppler broadening of an Argon ion line using a Fabry-Perot interferometer. Low efficiency main body ion heating (1 to 3 percent) was observed. (auth)
Date: December 1, 1975
Creator: Hawryluk, R.J.; Davis, S.L. & Schmidt, J.A.
Partner: UNT Libraries Government Documents Department

Wave generation and heating near ion cyclotron frequency in the ST Tokamak

Description: The results of the recent, high power ICRH experiments performed on the ST Tokamak are reported. It was demonstrated that both the fast and slow waves could be generated in toroidal geometry, and heating of the plasma ions at power levels up to 1 MW was observed both at the ion cyclotron frequency ($omega$/sub ci/) and its second harmonic (2$omega$/sub ci/). Measurements by a charge exchange neutral detector directed tangentially to the plasma torus revealed that at 2$omega$/sub ci/ the ion energy within the bulk of the ion distribution function (''parallel body temperature'') could be increased from about 100 eV up to 200 eV with efficiencies ranging from 8 to 45 percent. Efficiency at $omega$/ sub ci/ in raising the parallel temperature was less than at 2$omega$/sub ci/. Charge exchange neutral detection perpendicular to the plasma column showed that both at $omega$/sub ci/ and 2$omega$/sub ci/ the ''perpendicular body temperature'' was enhanced very rapidly by a factor of up to 3. Also, buildup of a high energy ''tail'' in the ion energy distribution was observed. Power transfer to the ions seemed extremely efficient. (auth)
Date: October 1, 1975
Creator: Takahashi, H.
Partner: UNT Libraries Government Documents Department

Small-scale density fluctuations in the adiabatic toroidal compressor

Description: A new class of density fluctuations has been observed in the ATC tokamak by using spectral analysis of scattered microwaves. The observed frequency spectrum is consistent with that of drift waves with amplitudes that are maximum in the wavelength range 0.5 to 1.0 cm where finite ion Larmor radius effects are important for plasma stability. The total density fluctuation is n tilde/sub e/ greater than or equal to 5 x 10$sup -3$ anti n/sub e/. It is estimated that these fluctuations could account for a large fraction of the electron energy losses of the ATC discharge. (auth)
Date: February 1, 1976
Creator: Mazzucato, E.
Partner: UNT Libraries Government Documents Department

Radio frequency plasma heating in large tokamak systems near the lower hybrid resonance

Description: The frequency range, power, efficiency, and pulse length of a high power rf system are discussed as they might be applied to the TFTR Tokamak facility as well as on a full scale reactor. Comparisons are made of the size, power output, and costs to obtain microwave power sufficient to satisfy the physics requirements. A new microwave feed concept is discussed which will improve the coupling of the microwave energy into the plasma. The unique advantages of waveguide feed systems is apparent when one considers the practical problems associated with coupling supplementary heating energy into a reactor. (auth)
Date: January 1, 1975
Creator: Deitz, A. & Hooke, W.M.
Partner: UNT Libraries Government Documents Department

Studies of charged particle distributions in an electrostatic confinement system. Progress report, 1 November 1971--31 January 1976

Description: Microwave cavity techniques were used to measure electron density in a spherical, inertial-electrostatic confinement device using six ion guns. The density was roughly proportional to ion current (1 to 17 mA) and decreased somewhat with increasing ion energy (10 to 37 keV). With D$sub 2$ pressure decrease from 10 to 3 mTorr, n/sub e/ decreased faster than linearly and below approximately 3 mTorr decreased linearly with pressure down to the lowest pressure of 0.4 mTorr. At 1 mTorr and 10 mA, measurements (with poor spatial resolution) were consistent with 10$sup 10$ total electrons and a central n/sub e/ of 10$sup 9$ electrons/cm$sup 3$. Neutron flux (at 50 keV) was about one sixth that of Hirsch (J. Appl. Phys. 38, 4522 (1967)). Six- vs. three-gun operation showed a small enhancement of both n/sub e/ and neutron flux that may indicate some particle trapping.
Date: January 1, 1976
Creator: Gardner, A.L.
Partner: UNT Libraries Government Documents Department

Experimental determination of DT ion temperatures in laser fusion targets

Description: Using the time-of-flight technique, energy distribution measurements were made of the fusion produced $alpha$ particles emitted from laser implosions of DT gas contained in glass microshells. The number of nuclear reactions was determined by an absolute measurement of both the number of $alpha$ particles and the number of neutrons. From the FWHM of the $alpha$ particle energy distributions, upper limits of the plasmas ion temperature have been inferred. By applying corrections for the broadening of the distribution due to the fuel and the pusher, ion temperatures of 2-3 keV have been calculated. These measurements constitute significant evidence that the implosions produced thermonuclear burn of the DT fuel. (auth)
Date: October 1, 1975
Creator: Ahlstrom, H.G.; Slivinsky, V.W.; Tirsell, K.G.; Storm, E.K.; Glaros, S.S. & Campbell, D.
Partner: UNT Libraries Government Documents Department