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Polarized advanced fuel reactors

Description: The d-/sup 3/He reaction has the same spin dependence as the d-t reaction. It produces no neutrons, so that if the d-d reactivity could be reduced, it would lead to a neutron-lean reactor. The current understanding of the possible suppression of the d-d reactivity by spin polarization is discussed. The question as to whether a suppression is possible is still unresolved. Other advanced fuel reactions are briefly discussed. 11 refs.
Date: July 1, 1987
Creator: Kulsrud, R.M.
Partner: UNT Libraries Government Documents Department

Stochastic acceleration by hydromagnetic turbulence

Description: A general theory for particle acceleration by weak hydromagnetic turbulence with a given spectrum of waves is described. Various limiting cases, corresponding to Fermi acceleration and magnetic pumping, are discussed and two numerical examples illustrating them are given. An attempt is made to show that the expression for the rate of Fermi acceleration is valid for finite amplitudes.
Date: March 1, 1979
Creator: Kulsrud, R.M.
Partner: UNT Libraries Government Documents Department

Course/workshop on muon catalyzed fusion and fusion with polarized nuclei

Description: There seems to be some real connection between the spin states of the d-t nuclei in the muon mesomolecule dt..mu.. and the resultant sticking probability. This paper discusses this connection. No new experimental results on spin polarization are reported, but illuminating ideas emerged as to the role spin polarized plasmas could play in inertial confinement fusion and magnetic fusion. In addition, realistic evaluations were made as to the possibility of producing and preserving spin polarized plasmas. 4 refs.
Date: August 1, 1987
Creator: Kulsrud, R.M.
Partner: UNT Libraries Government Documents Department

Application of polarized nuclei to fusion

Description: It is shown that the d-t fusion reaction can be modified by polarizing nuclear spins. The ways in which this improves reactor performance are mentioned and the feasibility of the process of spin polarization for magnetic fusion is discussed. 18 refs.
Date: July 1, 1987
Creator: Kulsrud, R.M.
Partner: UNT Libraries Government Documents Department

Propagation of cosmic rays through a plasma

Description: The theory of the coupling of energetic particles to a plasma by Alfven wave instabilities is described. The theory is applied to the problem of propagation of cosmic rays through the interstellar plasma and to the problem of trapping of cosmic rays in an expanding bubble of plasma produced by a supernova explosion.
Date: July 1, 1978
Creator: Kulsrud, R.M.
Partner: UNT Libraries Government Documents Department

Plasma in astrophysics

Description: Two examples of plasma phenomena of importance to astrophysics are reviewed. These are examples where astrophysical understanding hinges on further progress in plasma physics understanding. The two examples are magnetic reconnection and the collisionless interaction between a population of energetic particles and a cooler gas or plasma, in particular the interaction between galactic cosmic rays and the interstellar medium.
Date: October 1, 1982
Creator: Kulsrud, R.M.
Partner: UNT Libraries Government Documents Department

MHD description of plasma: handbook of plasma physics

Description: The basic sets of MHD equations for the description of a plasma in various limits are derived and their usefulness and limits of validity are discussed. These limits are: the one fluid collisional plasma, the two fluid collisional plasma, the Chew-Goldberger Low formulation of the guiding center limit of a collisionless plasma and the double-adiabatic limit. Conservation relations are derived from these sets and the mathematics of the concept of flux freezing is given. An example is given illustrating the differences between guiding center theory and double adiabatic theory.
Date: October 1, 1980
Creator: Kulsrud, R.M.
Partner: UNT Libraries Government Documents Department

A proposed method for reducing the sticking constant in muon catalyzed fusion

Description: We present a method of reducing the effective sticking coefficient involving reacceleration of the He..mu.. ion-by-ion cyclotron resonance. It is necessary to work with the target D--T in solid or liquid form, and the target has to be divided into many thin rods or pellets of order 100 microns in radius. The idea is to impose a magnetic field and a rotating electric field. A balance is achieved between drag in the rods or pellets and acceleration in the region between, so that the He..mu.. ion is held at a constant velocity until stripping occurs. Although stripping is greatly reduced, the idea is not practical as it stands because of the large alpha particle heat produced in the target. 2 refs., 3 figs., 2 tabs.
Date: August 1, 1988
Creator: Kulsrud, R.M.
Partner: UNT Libraries Government Documents Department

Cold fusion catalyzed by muons and electrons

Description: Two alternative methods have been suggested to produce fusion power at low temperature. The first, muon catalyzed fusion or MCF, uses muons to spontaneously catalyze fusion through the muon mesomolecule formation. Unfortunately, this method fails to generate enough fusion energy to supply the muons, by a factor of about ten. The physics of MCF is discussed, and a possible approach to increasing the number of MCF fusions generated by each muon is mentioned. The second method, which has become known as Cold Fusion,'' involves catalysis by electrons in electrolytic cells. The physics of this process, if it exists, is more mysterious than MCF. However, it now appears to be an artifact, the claims for its reality resting largely on experimental errors occurring in rather delicate experiments. However, a very low level of such fusion claimed by Jones may be real. Experiments in cold fusion will also be discussed.
Date: October 1, 1990
Creator: Kulsrud, R.M.
Partner: UNT Libraries Government Documents Department

Stability in straight stellarators

Description: The stability of the straight stellarator against localized interchange modes is investigated employing the Mercier-Greene-Johnson criterion. Critical values of ..beta.. are obtained both numerically and analytically. The conclusion is that for classical helical stellarators the average limiting ..beta..'s are quite low of order three to four percent.
Date: July 1, 1981
Creator: Kulsrud, R.M. & Yoshikawa, S.
Partner: UNT Libraries Government Documents Department

Convective equilibrium and mixing-length theory for stellarator reactors

Description: In high ..beta.. stellarator and tokamak reactors, the plasma pressure gradient in some regions of the plasma may exceed the critical pressure gradient set by ballooning instabilities. In these regions, convective cells break out to enhance the transport. As a result, the pressure gradient can rise only slightly above the critical gradient and the plasma is in another state of equilibrium - ''convective equilibrium'' - in these regions. Although the convective transport cannot be calculated precisely, it is shown that the density and temperature profiles in the convective region can still be estimated. A simple mixing-length theory, similar to that used for convection in stellar interiors, is introduced in this paper to provide a qualitative description of the convective cells and to show that the convective transport is highly efficient. A numerical example for obtaining the density and temperature profiles in a stellarator reactor is given.
Date: September 1, 1985
Creator: Ho, D.D.M. & Kulsrud, R.M.
Partner: UNT Libraries Government Documents Department

Thermonuclear inverse magnetic pumping power cycle for stellarator reactors

Description: A novel power cycle for direct conversion of alpha-particle energy into electricity is proposed for an ignited plasma in a stellarator reactor. The plasma column is alternately compressed and expanded in minor radius by periodic variation of the toroidal magnetic field strength. As a result of the way a stellarator is expected to work, the plasma pressure during expansion is greater than the corresponding pressure during compression. Therefore, negative work is done on the plasma during a complete cycle. This work manifests itself as a back-voltage in the toroidal field coils, and direct electrical energy is obtained from this voltage. For a typical reactor, the average power obtained from this cycle (with a minor radius compression factor on the order of 50%) can be as much as 50% of the electrical power obtained from the thermonuclear neutrons without compressing the plasma. Thus, if it is feasible to vary the toroidal field strength, the power cycle provides an alternative scheme of energy conversion for a deuterium-tritium fueled reactor. The cycle may become an important method of energy conversion for advanced neutron-lean fueled reactors. By operating two or more reactors in tandem, the cycle can be made self-sustaining.
Date: September 1, 1985
Creator: Ho, D.D.M. & Kulsrud, R.M.
Partner: UNT Libraries Government Documents Department

Ion transport in stellarators

Description: Stellarator ion transport in the low-collisionality regime with a radial electric field is calculated by a systematic expansion of the drift-Boltzmann equation. The shape of the helical well is taken into account in this calculation. It is found that the barely trapped ions with three to four times the thermal energy give the dominant contribution to the diffusion. Expressions for the ion particle and energy fluxes are derived.
Date: September 1, 1985
Creator: Ho, D.D.M. & Kulsrud, R.M.
Partner: UNT Libraries Government Documents Department

Neoclassical transport in stellarators

Description: The stellarator neoclassical transport due to particles trapped in local helical wells is calculated in the low-collisionality regime using a systematic expansion. The behavior of electron transport is found to be the same over a wide range of energies, but the behavior of ion transport for low energy ions is found to be different than that for high energy ions. Furthermore, the electron fluxes do not vary with the change in the radial ambipolar electric field nearly as much as do the ion fluxes. Thus, the particle diffusion is controlled by the electrons. A nonradial ambipolar electric field is induced by ion drift. This electric field enhances the transport by about 15 to 20%. A convenient graphical method that allows one to determine the magnitude of the radial ambipolar field for machines with different parameters is presented. Numerical examples show that electron energy confinement time is comparable to the ion energy confinement time for all the different size stellarators studied. Although the neoclassical losses are large, it is shown that ignition can be achieved in a reasonably sized stellarator reactor. Finally, from the standpoint of reactor economics, the confinement scaling law shows that in order to increase n tau, it is better to increase the aspect ratio than the overall dimensions of the reactor.
Date: September 1, 1985
Creator: Ho, D.D.M. & Kulsrud, R.M.
Partner: UNT Libraries Government Documents Department

Forced magnetic reconnection

Description: By studying a simple model problem, we examine the time evolution of magnetic field islands which are induced by perturbing the boundary surrounding an incompressible plasma with a resonant surface inside. We find that for sufficiently small boundary perturbations, the reconnection and island formation process occurs on the tearing mode time scale defined by Furth, Killeen, and Rosenbluth. For larger perturbations the time scale is that defined by Rutherford. The resulting asymptotic equilibrium is such that surface currents in the resonant region vanish. A detailed analytical picture of this reconnection process is presented.
Date: November 1, 1984
Creator: Hahm, T.S. & Kulsrud, R.M.
Partner: UNT Libraries Government Documents Department

Hydromagnetic waves in high. beta. plasmas

Description: The wave propagation and damping properties in a collisionless thermal plasma for which ..beta.., the ratio of the plasma pressure to the magnetic pressure, is much greater than unity are determined. We achieve this by solving the full collisionless dispersion relation as an expansion in 1/..beta... To do this we develop a set of iteration methods which converge to this solution. We illustrate these results with two applications, the trapping of cosmic rays in supernovae remnants and the collisionless damping of hydromagnetic turbulence.
Date: February 1, 1979
Creator: Foote, E.A. & Kulsrud, R.M.
Partner: UNT Libraries Government Documents Department

Collisional depolarization in arbitrary magnetic fields

Description: The effect of arbitrary magnetic confinement geometry on the spin polarization of magnetically confined plasmas is investigated. The plasma is assumed to be in equilibrium so that the dominant depolarization mechanism is decorrelation of the spin-precession phase and the gyrophase by collisions.
Date: August 1, 1985
Creator: Cowley, S.C. & Kulsrud, R.M.
Partner: UNT Libraries Government Documents Department

Model for magnetic reconnection

Description: A forced reconnection problem was modeled by two infinite wires that are embedded in a plasma which carry parallel currents. They are brought together at a specified rate. The distance between the wires is taken as 2a(1-e/sup ..omega..t/). For small displacements, the hydromagnetic equations can be linearized and solved asymptotically. For larger displacements, the plasma behavior can be estimated by use of scaling arguments. We determine a local velocity of magnetic reconnection and show that it is essentially equal to the maximum possible reconnection velocity (that of the corresponding vacuum case) up to the time when this velocity approaches the local Alfven speed. We compare the details of our solution with the Sweet-Parker and Petschek reconnection theories.
Date: March 1, 1978
Creator: Adler, E.A. & Kulsrud, R.M.
Partner: UNT Libraries Government Documents Department

An analytic treatment for a model of superclustering in the universe

Description: Recently, Weinberg, Ostriker, and Dekel (WOD) have proposed a model of many spherical explosions which reproduces the large scale structure of the universe quite well. Because of the success of the model, we have developed an analytic treatment which gives the cluster-cluster correlation function and the cluster mass distribution in terms of the distribution of radii of the spherical voids. We also derive an expression for the distribution in terms of the cluster mass distribution. Thus, the cluster-cluster correlation function is given in terms of the cluster mass distribution function. The numerical results of WOD agree quite well with the predictions from the observed mass distribution. We give the cluster-cluster correlation function for several model distributions of radii. This formulation should be useful for future comparisons of observation and the model of WOD. 4 refs., 5 figs.
Date: January 1, 1989
Creator: Kulsrud, R.M. & Cowley, S.C.
Partner: UNT Libraries Government Documents Department

Convective cells and transport in toroidal plasmas

Description: The properties of convective cells and the diffusion resulting from such cells are significantly influenced by an inhomogeneity in the extermal confining magnetic field, such as that in toroidal plasmas. The convective diffusion in the presence of a field inhomogeneity is estimated. For a thermal background, this diffusion is shown to be substantially smaller than classical collisional diffusion. For a model nonthermal background, the diffusion is estimated, for typical parameters, to be at most of the order of collisional diffusion. The model background employed is based on spectra observed in numerical simulations of drift-wave-driven convective cells.
Date: December 1, 1978
Creator: Hassam, A.B. & Kulsrud, R.M.
Partner: UNT Libraries Government Documents Department

Time evolution of mass flows in a collisional tokamak

Description: The time evolution, due to dissipative processes, of an initial pattern of poloidal and toroidal mass flows in a tokamak is considered. The calculation is applicable to a collisional, low ..beta.., axisymmetric tokamak of arbitrary minor cross section. Time rates of change of poloidal flows which are subsonic but larger than the diamagnetic speed are given according to the magnitude of the flow and the collisionality of the plasma. Over most of parameter space for typical tokamaks, the poloidal rotation is strongly damped by magnetic pumping at the rate (l/qR)/sup 2/..nu../sub ii/, where l is the mean free path, qR the ''connection length,'' and ..nu../sub ii/ the ion-ion collision frequency. At higher speeds, even stronger damping is effected by electron thermal conduction. The toroidal rotation is determined largely by the conservation of toroidal angular momentum. A heuristic explanation of the damping due to magnetic pumping is given.
Date: April 1, 1978
Creator: Hassam, A.B. & Kulsrud, R.M.
Partner: UNT Libraries Government Documents Department

Stability of colliding ion beams

Description: We determine conditions for stability of two identical colliding ion beams in the presence of neutralizing electrons, but no background ions. Such a situation is envisioned for the Counterstreaming Ion Torus. The ion beams are taken to be Maxwellian in their frames of reference. The approximation of electrostatic and electromagnetic modes is made. The stability of the electrostatic modes depends on the relation between the ion electron temperature ratio and the relative beam velocities. The stability of the electromagnetic mode depends on the relation between the ion plasma ..beta.. and the relative beam velocities.
Date: November 1, 1980
Creator: Foote, E.A. & Kulsrud, R.M.
Partner: UNT Libraries Government Documents Department

Linear stability of tearing modes

Description: This paper examines the stability of tearing modes in a sheared slab when the width of the tearing layer is much smaller than the ion Larmor radius. The ion response is nonlocal, and the quasineutrality retains its full integal form. An expansion procedure is introduced to solve the quasineutrality equation in powers of the width of the tearing layer over the ion Larmor radius. The expansion procedure is applied to the collisionless and semi-collisional tearing modes. The first order terms in the expansion we find to be strongly stabilizing. The physics of the mode and of the stabilization is discussed. Tearing modes are observed in experiments even though the slab theory predicts stability. It is proposed that these modes grow from an equilibrium with islands at the rational surfaces. If the equilibrium islands are wider than the ion Larmor radius, the mode is unstable when ..delta..' is positive.
Date: May 1, 1986
Creator: Cowley, S.C.; Kulsrud, R.M. & Hahm, T.S.
Partner: UNT Libraries Government Documents Department