56 Matching Results

Search Results

Advanced search parameters have been applied.

Heating efficiency of high-power perpendicular neutral-beam injection in PDX

Description: The heating efficiency of high power (up to 7.2 MW) near-perpendicular neutral beam injection in the PDX tokamak is comparable to that of tangential injection in PLT. Collisionless plasmas with central ion temperatures up to 6.5 keV and central electron temperatures greater than 2.5 keV have been obtained. The plasma pressure, including the contribution from the beam particles, increases with increasing beam power and does not appear to saturate, although the parametric dependence of the energy confinement time is different from that observed in ohmic discharges.
Date: March 1, 1982
Creator: Hawryluk, R.J.; Arunasalam, V. & Bell, M.
Partner: UNT Libraries Government Documents Department

Effect of current profile evolution on plasma-limiter interaction and the energy confinement time

Description: Experiments conducted on the PLT tokamak have shown that both plasma-limiter interaction and the gross energy confinement time are functions of the gas influx during the discharge. By suitably controlling the gas influx, it is possible to contract the current channel, decrease impurity radiation from the core of the discharge, and increase the gross energy confinement time, whether the aperture limiters were of tungsten, stainless steel or carbon.
Date: April 1, 1979
Creator: Hawryluk, R.J.; Bol, K. & Bretz, N.
Partner: UNT Libraries Government Documents Department

Results from deuterium-tritium tokamak confinement experiments

Description: Recent scientific and technical progress in magnetic fusion experiments has resulted in the achievement of plasma parameters (density and temperature) which enabled the production of significant bursts of fusion power from deuterium-tritium fuels and the first studies of the physics of burning plasmas. The key scientific issues in the reacting plasma core are plasma confinement, magnetohydrodynamic (MHD) stability, and the confinement and loss of energetic fusion products from the reacting fuel ions. Progress in the development of regimes of operation which have both good confinement and are MHD stable have enabled a broad study of burning plasma physics issues. A review of the technical and scientific results from the deuterium-tritium experiments on the Joint European Torus (JET) and the Tokamak Fusion Test Reactor (TFTR) is given with particular emphasis on alpha-particle physics issues.
Date: February 1, 1997
Creator: Hawryluk, R.J.
Partner: UNT Libraries Government Documents Department

Review of D-T Experiments Relevant to Burning Plasma Issues

Description: Progress in the performance of tokamak devices has enabled not only the production of significant bursts of fusion energy from deuterium-tritium (D-T) plasmas in the Tokamak Fusion Test Reactor (TFTR) and the Joint European Torus (JET) but, more importantly, the initial study of the physics of burning magnetically confined plasmas. The TFTR and JET, in conjunction with the worldwide fusion effort, have studied a broad range of topics including magnetohydrodynamic stability, transport, wave-particle interactions, the confinement of energetic particles, and plasma boundary interactions. The D-T experiments differ in three principal ways from previous experiments: isotope effects associated with the use of deuterium-tritium fuel, the presence of fusion-generated alpha particles, and technology issues associated with tritium handling and increased activation. The effect of deuterium-tritium fuel and the presence of alpha particles is reviewed and placed in the perspective of the much large r worldwide database using deuterium fuel and theoretical understanding. Both devices have contributed substantially to addressing the scientific and technical issues associated with burning plasmas. However, future burning plasma experiments will operate with larger ratios of alpha heating power to auxiliary power and will be able to access additional alpha-particle physics issues. The scientific opportunities for extending our understanding of burning plasmas beyond that provided by current experiments is described.
Date: December 21, 2001
Creator: Hawryluk, R.J.
Partner: UNT Libraries Government Documents Department

Inhibition of the current-driven ion wave instability by electron trapping in the FM-1 spherator

Description: An experimental analysis is made of the scattering of microwaves by the density fluctuations due to the current-driven ion wave instability in a toroidal plasma confinement device, the FM-1 spherator. It is found that the instability exists in the collisional regime and it is inhibited (i.e., quenched by two orders in magnitude) in the trapped-electron (i.e., banana) regime. The inhibition occurs when the electron collision frequency is about equal to the electron bounce frequency between mirror trapping. (auth)
Date: October 1, 1975
Creator: Arunasalam, V.; Okabayaski, M.; Hawryluk, R.J. & Suckewer, S.
Partner: UNT Libraries Government Documents Department

Low Z impurity transport in tokamaks. [Neoclassical transport theory]

Description: Low Z impurity transport in tokamaks was simulated with a one-dimensional impurity transport model including both neoclassical and anomalous transport. The neoclassical fluxes are due to collisions between the background plasma and impurity ions as well as collisions between the various ionization states. The evaluation of the neoclassical fluxes takes into account the different collisionality regimes of the background plasma and the impurity ions. A limiter scrapeoff model is used to define the boundary conditions for the impurity ions in the plasma periphery. In order to account for the spectroscopic measurements of power radiated by the lower ionization states, fluxes due to anomalous transport are included. The sensitivity of the results to uncertainties in rate coefficients and plasma parameters in the periphery are investigated. The implications of the transport model for spectroscopic evaluation of impurity concentrations, impurity fluxes, and radiated power from line emission measurements are discussed.
Date: October 1, 1978
Creator: Hawryluk, R.J.; Suckewer, S. & Hirshman, S.P.
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

Results from D-T Experiments on TFTR and Implications for Achieving an Ignited Plasma

Description: Progress in the performance of tokamak devices has enabled not only the production of significant bursts of fusion energy from deuterium-tritium plasmas in the Tokamak Fusion Test Reactor (TFTR) and the Joint European Torus (JET) but, more importantly, the initial study of the physics of burning magnetically confined plasmas. As a result of the worldwide research on tokamaks, the scientific and technical issues for achieving an ignited plasma are better understood and the remaining questions more clearly defined. The principal research topics which have been studied on TFTR are transport, magnetohydrodynamic stability, and energetic particle confinement. The integration of separate solutions to problems in each of these research areas has also been of major interest. Although significant advances, such as the reduction of turbulent transport by means of internal transport barriers, identification of the theoretically predicted bootstrap current, and the study of the confinement of energetic fusion alpha-particles have been made, interesting and important scientific and technical issues remain for achieving a magnetic fusion energy reactor. In this paper, the implications of the TFTR experiments for overcoming these remaining issues will be discussed.
Date: July 14, 1998
Creator: Hawryluk, R.J. and the TFTR Group
Partner: UNT Libraries Government Documents Department

Results from D-T experiments on TFTR and implications for achieving an ignited plasma

Description: Progress in the performance of tokamak devices has enable not only the production of significant bursts of fusion energy from deuterium-tritium plasmas in the Tokamak Fusion Test Reactor (TFTR) and the Joint European Torus (JET) but, more importantly, the initial study of the physics of burning magnetically confined plasmas. As a result of the worldwide research on tokamaks, the scientific and technical issues for achieving an ignited plasma are better understood and the remaining questions more clearly defined. The principal research topics which have been studied on TFTR are transport, magnetohydrodynamic stability, and energetic particle confinement. The integration of separate solutions to problems in each of these research areas has also been of major interest. Although significant advances, such as the reduction of turbulent transport by means of internal transport barriers, identification of the theoretically predicted bootstrap current, and the study of the confinement of energetic fusion alpha-particles have been made, interesting and important scientific and technical issues remain. In this paper, the implications for the TFTR experiments for overcoming these remaining issues will be discussed.
Date: July 1, 1998
Creator: Hawryluk, R.J.; Blanchard, W. & Batha, S.
Partner: UNT Libraries Government Documents Department

Gas injection in PLT: experimental overview

Description: Cold gas injection serves both the obvious role of a particle source at the surface of the plasma and a more subtle role as one element in the process by which the relative impurity concentration and the MHD activity of a discharge are determined. Evidence offered by PLT experiments in support of these two widely recognized roles is considered.
Date: January 1, 1977
Creator: Schmidt, G.L.; Bretz, N.I.; Hawryluk, R.J.; Hosea, J.C. & Johnson, D.W.
Partner: UNT Libraries Government Documents Department

Effects of low Z impurities during the startup phase of a large tokamak

Description: The requirements placed on a tokamak ohmic heating system (i.e. loop voltage) to initiate the plasma become more severe as the size increases because of the current density decrease. During the startup phase even small concentrations of low Z impurities can affect the plasma energy balance very substantially and have very important effects on the evolution of the discharge. The startup phase has been studied using a simple zero dimensional computer code. Because the dominant energy loss mechanisms during startup, radiation, and ionization are a volume effect, the zero dimensional code was adequate to treat this phase. The results of this study which have been applied to TFTR indicate that the plasma evolution is a sensitive function of the applied loop voltage, impurity concentration, initial filling pressure and the manner in which gas is fed into the discharge. (auth)
Date: January 1, 1976
Creator: Hawryluk, R. J. & Schmidt, J. A.
Partner: UNT Libraries Government Documents Department

Initial conditioning of the TFTR vacuum vessel

Description: We report on the initial conditioning of the Tokamak Fusion Test Reactor (TFTR) vacuum vessel prior to the initiation of first plasma discharges, and during subsequent operation with high power ohmically-heated plasmas. Following evacuation of the 86 m/sup 3/ vessel with the 10/sup 4/ 1/s high vacuum pumping system, the vessel was conditioned by a 15 A dc glow discharge in H/sub 2/ at a pressure of 5 mTorr. Rapid-pulse discharge cleaning was used subsequently to preferentially condition the graphite plasma limiters. The effectiveness of the discharge cleaning was monitored by measuring the exhaust rates of the primary discharge products (CO/C/sub 2/H/sub 4/, CH/sub 4/, and H/sub 2/O). After 175 hours of glow discharge treatment, the equivalent of 50 monolayers of C and O was removed from the vessel, and the partial pressures of impurity gases were reduced to the range of 10/sup -9/-10/sup -10/ Torr.
Date: January 1, 1984
Creator: Dylla, H. F.; Blanchard, W. R.; Krawchuk, R. B.; Hawryluk, R. J. & Owens, D. K.
Partner: UNT Libraries Government Documents Department

Confinement and heating of a deuterium-tritium plasma

Description: The Tokamak Fusion Test Reactor (TFTR) has performed initial high-power experiments with the plasma fueled by deuterium and tritium to nominally equal densities. Compared to pure deuterium plasmas, the energy stored in the electron and ions increased by {approximately}20%. These increases indicate improvements in confinement associated with the use of tritium and possibly heating of electrons by {alpha}-particles.
Date: March 1, 1994
Creator: Hawryluk, R. J.; Adler, H. & Alling, P.
Partner: UNT Libraries Government Documents Department

Observation of magnetic islands in the FM-1 spherator

Description: Time independent spatially periodic variations in the density and floating potential have been observed in the FM-1 spherator. On the exterior of the plasma/ sup ..delta..n//n and/ sup ..delta..phi//phi are found to be as much as 0.3. Experimental evidence indicates these variations are due to magnetic islands created by small field errors produced by the levitated ring. Calculations of the expected island size agree well with observations.
Date: June 1, 1976
Creator: Davis, S. L.; Hawryluk, R. J. & Schmidt, J. A.
Partner: UNT Libraries Government Documents Department

Observation of inverted population levels in the FM-1 Spherator

Description: Inversions in the populations of excited levels in hydrogen and HeII were observed in the FM-1 Spherator. The inversion increases strongly as the ratio of the decay time of the electron temperature to the decay time of the electron density was decreased. Time dependent numerical calculations of the populations were in good agreement with the experimental measurements. More general calculations for high Z hydrogen-like ions are discussed.
Date: April 1, 1976
Creator: Suckewer, S.; Hawryluk, R. J.; Okabayashi, M. & Schmidt, J. A.
Partner: UNT Libraries Government Documents Department

Current penetration in the PLT tokamak

Description: Current penetration in the PLT tokamak is modeled by a one dimensional magnetic field diffusion code assuming neoclassical resistivity. The code uses the measured temperature and density profiles as well as current and voltage measurements to evaluate Z/sub eff/. Under certain conditions, the resulting calculations of Z/sub eff/ during the startup phase have been considerably larger than the Z/sub eff/ determined spectroscopically indicating the presence of an enhanced current penetration mechanism. Furthermore, these calculations indicate that the gross energy confinement time is substantially less during the startup phase than in the quasi-steady state.
Date: January 1, 1980
Creator: Hawryluk, R.J.; Bretz, N.; Dimock, D.; Hinnov, E.; Johnson, D.; Monticello, D. et al.
Partner: UNT Libraries Government Documents Department

Observations of changes in residual gas and surface composition with discharge cleaning in PLT

Description: Hydrogen discharge cleaning of the PLT vacuum vessel has been studied by mass spectroscopy of desorbed gases and surface analysis of exposed samples. Several modes of vessel conditioning have been studied to date: (1) a high power discharge cleaning (PDC) mode, with a peak power density to the vessel wall P/sub s/ approximately 0.6 w/cm/sup 2/ and a peak electron temperature T/sub e/ approximately 100 ev; (2) low power (Taylor-type) discharge cleaning (TDC) with P/sub s/ approximately 0.05 w/cm/sup 2/ and T/sub e/ equal to or less than 5 eV. The predominant residual gases produced during PDC are CH/sub 4/ (1-5 x 10/sup -6/ torr) and CO (1-10 x 10/sup -7/ torr), whereas TDC produced primarily H/sub 2/O (1-2 x 10/sup -6/ torr) and CH/sub 4/ (1-10 x 10/sup -7/ torr). In situ surface analysis of hydrocarbon-covered stainless steel has shown significant decreases in carbon coverage occurring after 10/sup 3/-10/sup 4/ pulses of either cleaning mode. Observed changes in oxygen coverage are more difficult to interpret because of the presence of the nascent oxide layer on the stainless steel substrates.
Date: October 1, 1978
Creator: Dylla, H.F.; Bol, K.; Cohen, S.A.; Hawryluk, R.J.; Meservey, E.B. & Rossnagel, S.M.
Partner: UNT Libraries Government Documents Department

New techniques for calculating heat and particle source rates due to neutral-beam injection in axisymmetric tokamaks

Description: A set of numerical techniques are described for calculating heat and particle source rates due to neutral beam injection in axisymmetric tokamaks. While these techniques consume a substantial amount of computer time, they take into account a number of significant, and normally neglected, effects. Examples of these effects are reionization of escaping charge exchanged beam particles, finite fast ion orbit excursions, beam deposition through collisions of beam neutrals with circulating beam ions, and the transport of thermal neutrals in the plasma due to charge changing collisions with beam ions.
Date: February 1, 1981
Creator: Goldston, R.J.; McCune, D.C.; Towner, H.H.; Davis, S.L.; Hawryluk, R.J. & Schmidt, G.L.
Partner: UNT Libraries Government Documents Department

Energy loss rates of energetic ions injected into the FM-1 spherator

Description: Energy loss rates of energetic ions were studied during neutral beam injection experiments on the FM-1 spherator. Under typical experimental conditions, the injected beam ions slowed-down on the plasma electrons resulting in electron heating. The measured slowing-down rate was found to be in agreement with classical predictions.
Date: October 1, 1976
Creator: Davis, S. L.; Arunasalam, V.; Hawryluk, R. J.; Okabayashi, M.; Schmidt, G. L.; Schmidt, J. A. et al.
Partner: UNT Libraries Government Documents Department

Carbon influx flow rate in an ohmically heated plasma in the FM-1 spherator

Description: The flow rate of neutral carbon atoms during the initial startup phase of an ohmically heated plasma in the FM-1 spherator was determined from the spatially resolved measurements of the carbon line radiation and independent measurements of spatial distribution of plasma density and electron temperature. This was accomplished by comparing the measured carbon line intensity with a numerical solution of time-dependent coupled differential rate equations for several carbon ionization states. The empirical flow rate of carbon atoms into the discharge, GAMMA/sub flow/(t), was found to be GAMMA/sub flow/(t) approximately equal to n/sub e/(t)/ tau/sub flow/, where tau/sub flow/ was 30-100 msec depending upon discharge conditions.
Date: May 1, 1976
Creator: Ando, K.; Okabayashi, M.; Suckewer, S.; Arunasalam, V.; Hawryluk, R. J. & Wilson, J.
Partner: UNT Libraries Government Documents Department

First-wall and limiter conditioning in TFTR

Description: A progress report on the experimental studies of vacuum vessel conditioning during the first year of TFTR operation is presented. A previous paper described the efforts expended to condition the TFTR vessel prior to and during the initial plasma start-up experiments. During the start-up phase, discharge cleaning was performed with the vessel at room temperature. For the second phase of TFTR operations, which was directed towards the optimization of ohmically heated plasmas, the vacuum vessel could be heated to 150/sup 0/C. The internal configuration of the TFTR vessel was more complex during the second phase with the addition of a TiC/C moveable limiter array, Inconel bellows cover plates, and ZrAl getter pumps. A quantitative comparison is given on the effectiveness of vessel bakeout, glow discharge cleaning, and pulse discharge cleaning in terms of the total quantity of removed carbon and oxygen, residual gas base pressures and the resulting plasma impurity levels as measured by visible, uv, and soft x-ray spectroscopy. The initial experience with hydrogen isotope changeover in TFTR is presented including the results of the attempt to hasten the changeover time by using a glow discharge to precondition the vessel with the new isotope.
Date: October 1, 1984
Creator: Dylla, H.F.; Blanchard, W.R.; Hawryluk, R.J.; Hill, K.W.; Krawchuk, R.B.; Mueller, D. et al.
Partner: UNT Libraries Government Documents Department