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Plasma Science, IEEE Transactions on

Issue 4 • Date Dec. 1981

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Displaying Results 1 - 25 of 28
  • Table of contents

    Publication Year: 1981 , Page(s): c1
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    Freely Available from IEEE
  • IEEE Transactions on Plasma Science

    Publication Year: 1981 , Page(s): c2
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  • Guest Editorial

    Publication Year: 1981 , Page(s): 129
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  • The Stellarator Concept

    Publication Year: 1981 , Page(s): 130 - 141
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    First Page of the Article
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  • The Stellarator Program

    Publication Year: 1981 , Page(s): 142 - 149
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    The worldwide development of stellarator research is reviewed briefly and informally. View full abstract»

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  • Status of stellarator experiments-1981

    Publication Year: 1981 , Page(s): 150 - 163
    Cited by:  Papers (1)
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    During the last years growing interest in stellarators as toroidal magnetic confinement devices becomes evident. In spite of many restrictions, e.g., small minor radius a ˜0.1 m, plasma parameters comparable to those in tokamaks have been achieved. The deleterious effect of the plasma current on stability, equilibrium, and transport could be clarified. The progress of heating by the use of neutral injection and RF, allows to substitute ohmic heating. In the currentless phase significant improvement of the confinement at reasonable parameters has been observed. The substantial reduction of low-frequency and MHD fluctuations seems related to a decreased electron heat conduction. View full abstract»

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  • UWTOR-M-a conceptual design study of a modular stellarator power reactor

    Publication Year: 1981 , Page(s): 163 - 172
    Cited by:  Patents (1)
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    A preliminary design of a 5500 MWth modular stellarator power reactor, UWTOR-M, is presented. Discrete twisted coils are used in an l = 3 configuration with maintainability as a prime consideration. The natural steliarator divertor is used for impurity control in conjunction with innovative high performance divertor targets. A unique blanket design is proposed which minimizes the overall tritium inventory in the reactor. Finally, a scheme for maintaining the first wall/blanket and other reactor components is discussed. View full abstract»

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  • A Summary of Containment Experiments on the PROTO-CLEO Stellarator, 1968-1974

    Publication Year: 1981 , Page(s): 172 - 180
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    This report collects together results on the containment of plasma injected into the PROTO-CLEO stellarator, some of which have been previously presented as conference papers. The importance of fluctuations on plasma containment is also discussed and an attempt made to arrive at momentum balance for the ions and electrons. It is concluded that although plasma can be contained for periods as long as expected on the basis of loss solely by collisions, it cannot be conclusively demonstrated that this is the sole mechanism of plasma loss, since evidence for the existence of the diffusion driven current cannot be found. View full abstract»

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  • Confinement, Additional Heating (NBI, LHH, ECH), and Current Drive of Stellarator Plasma in JIPP T-II

    Publication Year: 1981 , Page(s): 180 - 187
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    The confinement of ohmically heated stellarator plasma is studied experimentally. The energy confinement time ¿E increases with the total rotational transform angle ¿¿ in the case of ¿¿/2¿ < 0.25, that is, q¿(a) > 4, while ¿E decreases with ¿¿/2¿ > 0.3, that is, q¿(a) < 3-4, which is consistent with the Alcator scaling. When the rotational transform angle due to helical field ¿h/2¿ is larger than 0.14, no major disruptions are observed even for q¿(a) as low as 1.7 (¿h/2¿= 0.14, Ip ¿ 100 kA at Bt = 2.2 T), although strong MHD oscillations with low frequency (~1 kHz) appear when q¿(a) < 2. Tangential injections of neutral beams are carried out for additional heating of stellarator and tokamak plasmas. With co-injection, the increase in ion temperature ¿Ti at the center per injected power PN into the torus is 1.6 eV/kW in the stellarator and is 1.9 eV/kW in the tokamak configuration. In the case of counter-injection, ¿Ti/PNis 1.6 eV/kW in both configurations. Lower hybrid heating (LHH) with the frequency of 0.8 GHz is applied. In both cases of stellarator and tokamak, ion heating of 0.8 eV/kW is observed with input power up to 160-180 kW. Electron cyclotron heating (ECH) by use of klystrons with frequency of 35.5 GHz is carried out. Preliminary results show heating of bulk electrons with the heating efficiency of 1.6 eV/kW. Current drive in steliarator plasma by lower hybrid wave is observed in the case of low density plasma (n¿e ~5 × 1012 cm-3). View full abstract»

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  • OHTE: A Helical Pinch with Pitch Reversal

    Publication Year: 1981 , Page(s): 187 - 198
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    The OHTE configuration is obtained by surrounding a reversed field pinch (RFP) with a stellarator-like helical winding whose pitch is chosen to enhance field line pitch reversal. The helical coil current needed to form a separatrix boundary is calculated analytically for a simple plasma model, which gives results in close agreement with a numerical two-dimensional (2-D) MHD equilibrium code. Basic properties of the field line transform, which is predominantly in the axial or toroidal direction, are investigated. The 2-D equilibrium code is used to investigate the effects of current profiles and high beta, and the OHTE is compared with the RFP. These calculations show that the helical winding can significantly enlarge the parameter space for interchangestable finite-ß equilibria with pitch reversal while avoiding axial current reversal. View full abstract»

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  • Experimental and Theoretical Studies on Filling a Stel a Rator with Laser-Produced Plasma

    Publication Year: 1981 , Page(s): 199 - 211
    Cited by:  Papers (1)
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    Experiments have been performed on filling a stellarator with a noncurrent-carrying laser-produced plasma. Simultaneous plasma production by means of pulsed laser beams at four separate positions on the toroidal magnetic axis has been found to drastically enhance the trapping efficiency of produced plasma by stellarator field, to as high as 50 percent in contrast with about 10 percent in the case of plasma production at one position. This figure of 50 percent could be further improved to nearly 75 percent by spatially isotropic plasma productions which could not be realized in the present experiments owing to technical restrictions on the stellarator employed. The enhancement of trapping efficiency may be attributed to the reduction of toroidal plasma drift due to rotational transform coming into effect earlier in the multiposition production case. Some approximate theoretical analyses and considerations on toroidal drift motion of laser-produced plasma stream within stellarator field have also been presented, and the theoretical prediction on these analyses appears to be consistent with experimental results obtained. View full abstract»

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  • The Interchangeable Module Stellarator

    Publication Year: 1981 , Page(s): 212 - 220
    Cited by:  Papers (3)  |  Patents (1)
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    The Interchangeable Module Stellarator (IMS) is a new toroidal stellarator-type device under design and construction at the University of Wisconsin Torsatron/Stellarator Laboratory. A new design strategy for constructing stellarator magnetic fields from discrete modular coils has been developed, utilizing orthogonal toroidal coordinates. Application of this method has resulted in a modular coil system (IMS), whose magnetic structure closely approximates that of the Proto-Cleo Q = 3 7-field period device (i. e., rotational transform, shear, flux volume, etc.). View full abstract»

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  • Theoretical Optimization of Stellarators

    Publication Year: 1981 , Page(s): 221 - 228
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    Net current free toroidal ("stellarator") confinement is studied with a combination of several methods: a complete set of analytical vacuum fields for finding favorable vacuum field configurations; three-dimensional MHD codes for finite-ß, equilibrium computations; the expansion of a general toroidal equilibrium around its magnetic axis as guideline for the computational search in configurational space and for finite-ß, MHD stability; Monte Carlo simulations for particle containment; continuous modular coil systems generating the configurations considered. Results are: vacuum field configurations with sizeable Q = 0, 1, 2, 3 helical fields, substantial twist number (¿ 1/2), significant reduction of the parallel current density, and vacuum magnetic well exist for a toroidal aspect ratio of 15-20 and can be generated by modular coils whose excursions from meridional planes are small compared to the toroidal period length. In these configurations, the finite-ß toroidal shift is strongly reduced, so that a larger ß value (factor 2-4) than in the equivalent Q = 2 stellarator can be achieved. Stability calculations do not exclude the possibility of stable equilibria of this kind with (ß) ¿ 0.05-0.1; transport calculations without electrical field show improvement-as compared to the Q = 2 stellarator-in the collisional and plateau regimes. View full abstract»

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  • Modular Coils: A Promising Toroidal Coil System

    Publication Year: 1981 , Page(s): 228 - 233
    Cited by:  Patents (1)
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    The concept of modular coils originated from a need to find reactor-relevant stellarator windings. Considerations of 1) basic principles of modular coils, 2) types of coils, 3) types of configurations (general, helically symmetric, helically asymmetric, with magnetic well, with magnetic hill), 4) types of rotational transform profile, and 5) structure and origin of ripples are given. These results show that modular coils can offer a wide range of vacuum magnetic field configurations, some of which cannot be obtained with the classical stellarator or torsatron coil configuration. View full abstract»

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  • A Modular Stellarator Divertor

    Publication Year: 1981 , Page(s): 234 - 239
    Cited by:  Papers (2)
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    Modular stellarators, like continuous-helix steliarators, are characterized by a magnetic limiter and built-in divertor. We have found this divertor to be modular in nature. The magnetic structure of the divertor has been studied numerically for several different configurations. The divertor consists of a number of small localized flux bundles which resemble bundle divertors distributed over the torus. The impact of the divertor system on experimental design and a conceptual reactor study has been investigated in some detail. View full abstract»

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  • Finite β stellarators

    Publication Year: 1981 , Page(s): 239 - 243
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    A fully three-dimensional computer code based on an ideal magnetohydrodynamic model has been used to find stellarator configurations with finite critical values of the plasma parameter β. It is established that the WISTOR-U torsatron designed at the University of Wisconsin and the Heliotron E experiment constructed at Kyoto University have average β limits near 5 percent. View full abstract»

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  • Interchange-Ballooning Mode in l = 2 Helical Systems

    Publication Year: 1981 , Page(s): 243 - 247
    Cited by:  Papers (1)
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    A high shear toroidal helical system such as Heliotron E gives a limiting beta comparable to tokamaks, by examining stability against interchange-ballooning modes with a low toroidal mode number. The limiting beta depends on equilibrium pressure profiles and a high beta value is found for the pressure having a flat profile in the central region and a large pressure gradient at the high shear peripheral region of the plasma column. View full abstract»

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  • Simultaneous Operation of Electric Arcs from the Same Supply

    Publication Year: 1981 , Page(s): 248 - 254
    Cited by:  Patents (3)
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    A simple technique is described which enables two arcs to be operated from a single dc power supply over a wide range of operating conditions. The conditions for stabilizing coalesced arcs have been analyzed as an unbalanced bridge circuit and solved using a computer. The results indicated that the part of the arc adjacent to the electrode to which the stabilizing resistance was connected was stable and that the part of the arc adjacent to the other electrode was unstable when single individual stabilizing resistors were used for each arc. If the stabilizing resistance was shared equally on both sides of the arc both parts were stable and large volume discharges were produced. The technique may be extended to more than two arcs and the results may be applicable to arc processes used for welding, enabling simultaneous operation of several welding arcs from a common supply, surface deposition, plasma processes used for metallurgical reduction and chemical synthesis, and for the stimulation of laser excitation in gas lasers where increased efficiencies and higher powers may be obtained. View full abstract»

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  • Numerical Simulation of a Planar Vacuum Arc

    Publication Year: 1981 , Page(s): 254 - 258
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    A two-dimensional numerical simulation of a planar vacuum arc has been used to determinie the effect of the self-consistent magnetic fields on the arc plasma density, temperature, and heat flow. The results are consistent with experimentally observed discharges in which a linear pinch occurs. View full abstract»

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  • Vacuum Arc Behavior in a Transverse Magnetic Field

    Publication Year: 1981 , Page(s): 259 - 264
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    Experimental measurements in a vacuum interrupter have shown that the application of a transverse magnetic field results in substantial increases in arc voltage. Photographic studies of the arc column indicate that strong magnetic fields reduce the effective anode area and may lead to severe arc constriction. View full abstract»

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  • Two-Temperature Modeling of the Anode Contraction Region of High-Intensity Arcs

    Publication Year: 1981 , Page(s): 265 - 274
    Cited by:  Papers (1)
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    In this paper, an analytical model for a two-temperature plasma (Te > Tg) is established which is suitable for dealing with arcflow interactions induced by the arc itself. This model is applied to the anode contraction region of high-intensity argon arcs taking the interaction of anode and cathode jets close to the anode into account. The complete set of conservation equations describing the mass, charge, momentum, and energy transport of a two-temperature plasma with temperature-dependent transport properties is solved numerically by an interative finite-difference method using appropriate boundary conditions. Results for an atmospheric-pressure argon arc indicate that the temperature discrepancy between electrons and heavy particles is very pronounced in the arc fringes and in the regions close to the anode, while the departure from kinetic equilibrium becomes insignificant in regions in which the temperature exceeds 12 000 K (i.e., in the arc core). The computed temperature fields of the heavy particles in the anode contraction region resemble the observed arc appearance which clearly shows the interaction of anode and cathode jets in front of the anode. View full abstract»

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  • One-Dimensional Transport Code Modeling of the Divertor-Limiter Region in Tokamaks

    Publication Year: 1981 , Page(s): 274 - 282
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    A model of the divertor-limiter scrapeoff region has been incorporated into the BALDUR one-dimensional tokamak transport code. Simulations of the proposed Toroidal Fusion Test Reactor (TFTR), and Poloidal Divertor (PDX) experiments and existing Alcator-A tokamak experiments have been carried out for ohmic and neutral beam heated cases. In particular, we have studied how the edge conditions and energy-loss mechanisms in PDX depend upon plasma density, and compared our results with analytic estimates. The sensitivity of the results to changes in the transport coefficients and scrapeoff model is discussed with particular reference to the power loading on the TFTR limiter. View full abstract»

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  • Correlation of Radiation with Operating Parameters during PLT Neutral Injection

    Publication Year: 1981 , Page(s): 283 - 285
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    Changes in impurity radiation during injection of neutral beams into the Princeton Large Torus (PLT) tokamak have been studied using both a soft X-ray detector and a scanning bolometer. The direction of injection with respect to the plasma current is found to be the most consistently significant factor. Injection counter to the plasma current gives rise to more central radiation than either injection parallel to the current or simultaneous injection parallel and antiparallel to the current. In addition, injection into ungettered discharges increases the soft X-ray impurity radiation more than does injection into gettered discharges. At least for coinjection, the change in soft X-ray impurity radiation tends to be less at higher preinjection electron densities than at lower ones. View full abstract»

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  • Resonance Amplification of Ion-Acoustic Solitons in a Plasma-Beam System

    Publication Year: 1981 , Page(s): 286 - 289
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    The interaction of an ion-acoustic soliton with an ion beam in nonisothermal plasma is considered by using a model equation for the wave together with the path integral method for beam particles. The results show that the soliton amplitude reaches a value corresponding to the synchronism between the wave and the beam. Under some conditions, the process begins from a quasi-hydrodynamic stage which, however, is always followed by a kinetic stage associated with thfe appearance of resonance and reflected particles, the latter stage leading to much more effective amplification. View full abstract»

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  • Anode Spot Formation in Vacuum Arcs

    Publication Year: 1981 , Page(s): 290 - 291
    Cited by:  Papers (4)
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    Experiments on the transition of vacuum arcs from the diffuse mode into the constricted mode were carried out using both optoelectronic equipment and streak photography with time resolution in the range of microseconds. The transition occurs in a time range from 50 to 800 ¿s and appears to be a continuous process. View full abstract»

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IEEE Transactions on Plasma Sciences focuses on plasma science and engineering, including: magnetofluid dynamics and thermionics; plasma dynamics; gaseous electronics and arc technology.

 

 

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