Wave function for harmonically confined electrons in time-dependent electric and magnetostatic fields.

Science.gov (United States)

Zhu, Hong-Ming; Chen, Jin-Wang; Pan, Xiao-Yin; Sahni, Viraht

2014-01-14

We derive via the interaction "representation" the many-body wave function for harmonically confined electrons in the presence of a magnetostatic field and perturbed by a spatially homogeneous time-dependent electric field-the Generalized Kohn Theorem (GKT) wave function. In the absence of the harmonic confinement - the uniform electron gas - the GKT wave function reduces to the Kohn Theorem wave function. Without the magnetostatic field, the GKT wave function is the Harmonic Potential Theorem wave function. We further prove the validity of the connection between the GKT wave function derived and the system in an accelerated frame of reference. Finally, we provide examples of the application of the GKT wave function.

Dynamics and reactivity of confined water

International Nuclear Information System (INIS)

Musat, R.

2008-01-01

In the context of new sustainable energy sources quest, the nuclear energy remains a key solution. However, with the development of nuclear technology, problems relating to nuclear waste disposal arise; thus, the radiolysis of water in confined media is extremely important with respect to matters related to long time storage of nuclear waste. Studies in model porous media would allow the projection of a confined water radiolysis simulator. A first step in this direction was made by studying the radiolysis of water confined in Vycor and CPG glasses; this study continues the trend set and investigates the effects of confinement in metal materials upon the water radiolysis allowing the understanding of metal - water radiation induced corrosion. A further/complete understanding of the radiolytic process under confinement requires knowledge of the effect of confinement upon the dynamics of confined molecules and on the evolution of the species produced upon ionizing radiation. In this respect, we have used the OH vibrator as a probe of the hydrogen bond network properties and thus investigated the dynamics of confined water using IR time resolved spectroscopy. The evolution of the hydrated electron under confinement was studied on a nano and picosecond time scale using UV pump - visible probe technique and single shot spectroscopy. (author) [fr

Mean first-passage times in confined media: from Markovian to non-Markovian processes

International Nuclear Information System (INIS)

Bénichou, O; Voituriez, R; Guérin, T

2015-01-01

We review recent theoretical works that enable the accurate evaluation of the mean first passage time (MFPT) of a random walker to a target in confinement for Markovian (memory-less) and non-Markovian walkers. For the Markovian problem, we present a general theory which allows one to accurately evaluate the MFPT and its extensions to related first-passage observables such as splitting probabilities and occupation times. We show that this analytical approach provides a universal scaling dependence of the MFPT on both the volume of the confining domain and the source–target distance in the case of general scale-invariant processes. This analysis is applicable to a broad range of stochastic processes characterized by length scale-invariant properties, and reveals the key role that can be played by the starting position of the random walker. We then present an extension to non-Markovian walks by taking the specific example of a tagged monomer of a polymer chain looking for a target in confinement. We show that the MFPT can be calculated accurately by computing the distribution of the positions of all the monomers in the chain at the instant of reaction. Such a theory can be used to derive asymptotic relations that generalize the scaling dependence with the volume and the initial distance to the target derived for Markovian walks. Finally, we present an application of this theory to the problem of the first contact time between the two ends of a polymer chain, and review the various theoretical approaches of this non- Markovian problem. (topical review)

Observation of scaling laws of ion confining potential versus thermal barrier depth and of axial particle confinement time in the tandem mirror GAMMA 10

International Nuclear Information System (INIS)

Cho, T.; Inutake, M.; Ishii, K.

1988-01-01

In the thermal barrier tandem mirror GAMMA 10, the scaling law governing the enhancement of the ion confining potential, φ c , resulting from thermal barrier formation, is obtained experimentally, and is consistently interpreted in terms of the weak and strong ECH theories set up by Cohen and co-workers. The scaling law on the axial particle confinement time, τ pparallel , related to this φ c formation, is also demonstrated in detail; it is in good agreement with the Pastukhov theory as modified by Cohen and co-workers. This scaling is verified at any radial position in the core plasma region and at any time through the various stages of a discharge; this indicates a scaling with drastic improvement of τ pparallel , due to the potential formation in the tandem mirror plasma. (author). 41 refs, 12 figs

Global energy confinement in TORE SUPRA

International Nuclear Information System (INIS)

Hoang, G.T.; Bizarro, J.P.; Genile, B. de; Hutter, Th.; Laurent, L.; Litaudon, X.; Moreau, D.; Peysson, Y.; Tonon, G.; Houtte, D. van

1992-01-01

The global energy confinement behaviour of mixed Ohmic/Lower Hybrid driven Tore Supra plasmas has been analysed at various densities. In contradiction with L-mode ITER scaling law, this analysis indicates that the global energy confinement time depends strongly on the plasma density and the isotopic dependence seems not to be observed. The thermal electron energy content of steady-state discharges is in good agreement with the offset linear Rebut-Lallia scaling law. During current ramp experiments, the global energy confinement time was found to depend on the internal self-inductance (li). Improved confinement has been obtained for a steady-state 0.8 MA plasma where the plasma current profile is peaked by LH waves (li ∼1.8). In this case, the global confinement time is found to be about 40% higher than the value predicted by the Rebut-Lallia scaling law. (author) 3 refs., 6 figs

Conference summary: Experiments in confinement and plasma-wall interaction and innovative confinement concept

International Nuclear Information System (INIS)

Ninomiya, H.

2005-01-01

This paper summarizes the results presented at the 20th IAEA Fusion Energy Conference 2004 in the sessions of confinement, plasma-wall interaction and innovative confinement concept. The highlights of the presentations are as follows. Long pulse operation with high beta and high bootstrap fraction much longer than the current diffusion time has been achieved. The discharge scenario optimization and its extrapolation towards ITER have progressed remarkably. Significant progress has been made in understanding of global confinement and transport physics. (author)

Time-dependent recovery from Hell film boiling: confined geometry case

International Nuclear Information System (INIS)

Filippov, Yu.P.; Sergeev, I.A.

1991-01-01

Experiment results for transient cooldown of a solid in saturated superfluid helium after heat load switch-off are reported. The fluid space restriction in the vicinity of a heater is a specific feature of the tested heat transfer configuration. In this case the recovery duration is found to be set as ≅70% by the stage of film boiling received by the end of heat generation, as ≅20% -by the value of bulk fluid temperature, as ≅15% - by the confinement degree. The sample orientation does not affect the recovery time directly. The investigation has been performed at the Particle Physics Laboratory, JINR

Ignition in net for different energy confinement time scalings

International Nuclear Information System (INIS)

Johner, J.; Prevot, F.

1988-06-01

A zero-dimensional profile dependent model is used to assess the feasibility of ignition in the extended version of NET. Five recent scalings for the energy confinement time (Goldston, Kaye All, Kaye Big, Shimomura-Odajima, Rebut-Lallia) are compared in the frame of two different scenarii, i.e., H-mode with a flat density profile or L-mode with a peaked density profile. For the flat density H-mode case, ignition is accessible with none of the scalings except Rebut-Lallia's. For the peaked density L-mode case, ignition is accessible with none of the scalings except Rebut-Lallia's. For the two Kaye's scalings, ignition is forbidden in H-mode even with the peaked density profile. For the Rebut-Lallia scaling, ignition is allowed in L-mode even with the flat density profile

Full-f gyrokinetic simulation over a confinement time

Energy Technology Data Exchange (ETDEWEB)

Idomura, Yasuhiro, E-mail: idomura.yasuhiro@jaea.go.jp [Japan Atomic Energy Agency, Kashiwanoha 5-1-5, Kashiwa, Chiba 277-8587 (Japan)

2014-02-15

A long time ion temperature gradient driven turbulence simulation over a confinement time is performed using the full-f gyrokinetic Eulerian code GT5D. The convergence of steady temperature and rotation profiles is examined, and it is shown that the profile relaxation can be significantly accelerated when the simulation is initialized with linearly unstable temperature profiles. In the steady state, the temperature profile and the ion heat diffusivity are self-consistently determined by the power balance condition, while the intrinsic rotation profile is sustained by complicated momentum transport processes without momentum input. The steady turbulent momentum transport is characterized by bursty non-diffusive fluxes, and the resulting turbulent residual stress is consistent with the profile shear stress theory [Y. Camenen et al., “Consequences of profile shearing on toroidal momentum transport,” Nucl. Fusion 51, 073039 (2011)] in which the residual stress depends not only on the profile shear and the radial electric field shear but also on the radial electric field itself. Based on the toroidal angular momentum conservation, it is found that in the steady null momentum transport state, the turbulent residual stress is cancelled by the neoclassical counterpart, which is greatly enhanced in the presence of turbulent fluctuations.

Impurity confinement and transport in high confinement regimes without edge localized modes on DIII-D

Energy Technology Data Exchange (ETDEWEB)

Grierson, B. A., E-mail: bgriers@pppl.gov; Nazikian, R. M.; Solomon, W. M. [Princeton Plasma Physics Laboratory, Princeton University, Princeton, New Jersey 08543 (United States); Burrell, K. H.; Garofalo, A. M.; Belli, E. A.; Staebler, G. M.; Evans, T. E.; Smith, S. P.; Chrobak, C. [General Atomics, P.O. Box 85608, San Diego, California 92186-5608 (United States); Fenstermacher, M. E. [Lawerence Livermore National Laboratory, P.O. Box 808, Livermore, California 94550 (United States); McKee, G. R. [Department of Engineering Physics, University of Wisconsin-Madison, Madison, Wisconsin 53796 (United States); Orlov, D. M. [Center for Energy Research, University of California San Diego, 9500 Gilman Dr., La Jolla, California 92093-0417 (United States); Chrystal, C. [University of California San Diego, 9500 Gilman Dr., La Jolla, California 92093-0417 (United States)

2015-05-15

Impurity transport in the DIII-D tokamak [J. L. Luxon, Nucl. Fusion 42, 614 (2002)] is investigated in stationary high confinement (H-mode) regimes without edge localized modes (ELMs). In plasmas maintained by resonant magnetic perturbation (RMP), ELM-suppression, and QH-mode, the confinement time of fluorine (Z = 9) is equivalent to that in ELMing discharges with 40 Hz ELMs. For selected discharges with impurity injection, the impurity particle confinement time compared to the energy confinement time is in the range of τ{sub p}/τ{sub e}≈2−3. In QH-mode operation, the impurity confinement time is shown to be smaller for intense, coherent magnetic, and density fluctuations of the edge harmonic oscillation than weaker fluctuations. Transport coefficients are derived from the time evolution of the impurity density profile and compared to neoclassical and turbulent transport models NEO and TGLF. Neoclassical transport of fluorine is found to be small compared to the experimental values. In the ELMing and RMP ELM-suppressed plasma, the impurity transport is affected by the presence of tearing modes. For radii larger than the mode radius, the TGLF diffusion coefficient is smaller than the experimental value by a factor of 2–3, while the convective velocity is within error estimates. Low levels of diffusion are observed for radii smaller than the tearing mode radius. In the QH-mode plasma investigated, the TGLF diffusion coefficient is higher inside of ρ=0.4 and lower outside of 0.4 than the experiment, and the TGLF convective velocity is more negative by a factor of approximately 1.7.

The confining trailing string

CERN Document Server

Kiritsis, E; Nitti, F

2014-01-01

We extend the holographic trailing string picture of a heavy quark to the case of a bulk geometry dual to a confining gauge theory. We compute the classical trailing confining string solution for a static as well as a uniformly moving quark. The trailing string is infinitely extended and approaches a confining horizon, situated at a critical value of the radial coordinate, along one of the space-time directions, breaking boundary rotational invariance. We compute the equations for the fluctuations around the classical solutions, which are used to obtain boundary force correlators controlling the Langevin dynamics of the quark. The imaginary part of the correlators has a non-trivial low-frequency limit, which gives rise to a viscous friction coefficient induced by the confining vacuum. The vacuum correlators are used to define finite-temperature dressed Langevin correlators with an appropriate high-frequency behavior.

From Pauli's birthday to 'Confinement Resonances' – a potted history of Quantum Confinement

International Nuclear Information System (INIS)

Connerade, J P

2013-01-01

Quantum Confinement is in some sense a new subject. International meetings dedicated to Quantum Confinement have occurred only recently in Mexico City (the first in 2010 and the second, in September 2011). However, at least in principle, the subject has existed since a very long time. Surprisingly perhaps, it lay dormant for many years, for want of suitable experimental examples. However, when one looks carefully at its origin, it turns out to have a long and distinguished history. In fact, the problem of quantum confinement raises a number of very interesting issues concerning boundary conditions in elementary quantum mechanics and how they should be applied to real problems. Some of these issues were missed in the earliest papers, but are implicit in the structure of quantum mechanics, and lead to the notion of Confinement Resonances, the existence of which was predicted theoretically more than ten years ago. Although, for several reasons, these resonances remained elusive for a very long time, they have now been observed experimentally, which puts the whole subject in much better shape and, together with the advent of metallofullerenes, has contributed to its revival.

Global confinement characteristics of Jet limiter plasmas

International Nuclear Information System (INIS)

Campbell, D.J.; Christiansen, J.P.; Cordey, J.G.; Thomas, P.R.; Thomsen, K.

1989-01-01

Data from a wide variety of plasma pulses on JET (aux. heating, current, field, minority species, plasma shape, etc) are analysed in order to assess the characteristics of global confinement. The scaling of confinement in ohmically and auxiliary heated discharges is examined. The ohmic confinement in the present new JET configuration (Belt Limiter) is essentially the same as previously. Confinement in auxiliary heated discharges shows presently a slight improvement since 1986. Both ohmic and non-ohmic data is used in a set of confinement time regression analyses and certain constraints derived from theory are imposed

Comments on experimental results of energy confinement of tokamak plasmas

International Nuclear Information System (INIS)

Chu, T.K.

1989-04-01

The results of energy-confinement experiments on steady-state tokamak plasmas are examined. For plasmas with auxiliary heating, an analysis based on the heat diffusion equation is used to define heat confinement time (the incremental energy confinement time). For ohmically sustained plasmas, experiments show that the onset of the saturation regime of energy confinement, marfeing, detachment, and disruption are marked by distinct values of the parameter /bar n//sub e///bar j/. The confinement results of the two types of experiments can be described by a single surface in 3-dimensional space spanned by the plasma energy, the heating power, and the plasma density: the incremental energy confinement time /tau//sub inc/ = ΔW/ΔP is the correct concept for describing results of heat confinement in a heating experiment; the commonly used energy confinement time defined by /tau//sub E/ = W/P is not. A further examination shows that the change of edge parameters, as characterized by the change of the effective collision frequency ν/sub e/*, governs the change of confinement properties. The totality of the results of tokamak experiments on energy confinement appears to support a hypothesis that energy transport is determined by the preservation of the pressure gradient scale length. 70 refs., 6 figs., 1 tab

Momentum confinement at low torque

Energy Technology Data Exchange (ETDEWEB)

Solomon, W M [Princeton Plasma Physics Laboratory, Princeton University, Princeton, NJ 08543 (United States); Burrell, K H [General Atomics, PO Box 85608, San Diego, CA 92186-5608 (United States); De Grassie, J S [General Atomics, PO Box 85608, San Diego, CA 92186-5608 (United States); Budny, R [Princeton Plasma Physics Laboratory, Princeton University, Princeton, NJ 08543 (United States); Groebner, R J [General Atomics, PO Box 85608, San Diego, CA 92186-5608 (United States); Kinsey, J E [General Atomics, PO Box 85608, San Diego, CA 92186-5608 (United States); Kramer, G J [Princeton Plasma Physics Laboratory, Princeton University, Princeton, NJ 08543 (United States); Luce, T C [General Atomics, PO Box 85608, San Diego, CA 92186-5608 (United States); Makowski, M A [Lawrence Livermore National Laboratory, Livermore, CA 94550 (United States); Mikkelsen, D [Princeton Plasma Physics Laboratory, Princeton University, Princeton, NJ 08543 (United States); Nazikian, R [Princeton Plasma Physics Laboratory, Princeton University, Princeton, NJ 08543 (United States); Petty, C C [General Atomics, PO Box 85608, San Diego, CA 92186-5608 (United States); Politzer, P A [General Atomics, PO Box 85608, San Diego, CA 92186-5608 (United States); Scott, S D [Princeton Plasma Physics Laboratory, Princeton University, Princeton, NJ 08543 (United States); Zeeland, M A Van [General Atomics, PO Box 85608, San Diego, CA 92186-5608 (United States); Zarnstorff, M C [Princeton Plasma Physics Laboratory, Princeton University, Princeton, NJ 08543 (United States)

2007-12-15

Momentum confinement was investigated on DIII-D as a function of applied neutral beam torque at constant normalized beta {beta}{sub N}, by varying the mix of co (parallel to the plasma current) and counter neutral beams. Under balanced neutral beam injection (i.e. zero total torque to the plasma), the plasma maintains a significant rotation in the co-direction. This 'intrinsic' rotation can be modeled as being due to an offset in the applied torque (i.e. an 'anomalous torque'). This anomalous torque appears to have a magnitude comparable to one co neutral beam source. The presence of such an anomalous torque source must be taken into account to obtain meaningful quantities describing momentum transport, such as the global momentum confinement time and local diffusivities. Studies of the mechanical angular momentum in ELMing H-mode plasmas with elevated q{sub min} show that the momentum confinement time improves as the torque is reduced. In hybrid plasmas, the opposite effect is observed, namely that momentum confinement improves at high torque/rotation. GLF23 modeling suggests that the role of E x B shearing is quite different between the two plasmas, which may help to explain the different dependence of the momentum confinement on torque.

A Review of Quantum Confinement

Science.gov (United States)

Connerade, Jean-Patrick

2009-12-01

A succinct history of the Confined Atom problem is presented. The hydrogen atom confined to the centre of an impenetrable sphere counts amongst the exactly soluble problems of physics, alongside much more noted exact solutions such as Black Body Radiation and the free Hydrogen atom in absence of any radiation field. It shares with them the disadvantage of being an idealisation, while at the same time encapsulating in a simple way particular aspects of physical reality. The problem was first formulated by Sommerfeld and Welker [1]—henceforth cited as SW—in connection with the behaviour of atoms at very high pressures, and the solution was published on the occasion of Pauli's 60th birthday celebration. At the time, it seemed that there was not much other connection with physical reality beyond a few simple aspects connected to the properties of atoms in solids, for which more appropriate models were soon developed. Thus, confined atoms attracted little attention until the advent of the metallofullerene, which provided the first example of a confined atom with properties quite closely related to those originally considered by SW. Since then, the problem has received much more attention, and many more new features of quantum confinement, quantum compression, the quantum Faraday cage, electronic reorganisation, cavity resonances, etc have been described, which are relevant to real systems. Also, a number of other situations have been uncovered experimentally to which quantum confinement is relevant. Thus, studies of the confined atom are now more numerous, and have been extended both in terms of the models used and the systems to which they can be applied. Connections to thermodynamics are explored through the properties of a confined two-level atom adapted from Einstein's celebrated model, and issues of dynamical screening of electromagnetic radiation by the confining shell are discussed in connection with the Faraday cage produced by a confining conducting shell

A Review of Quantum Confinement

International Nuclear Information System (INIS)

Connerade, Jean-Patrick

2009-01-01

A succinct history of the Confined Atom problem is presented. The hydrogen atom confined to the centre of an impenetrable sphere counts amongst the exactly soluble problems of physics, alongside much more noted exact solutions such as Black Body Radiation and the free Hydrogen atom in absence of any radiation field. It shares with them the disadvantage of being an idealisation, while at the same time encapsulating in a simple way particular aspects of physical reality. The problem was first formulated by Sommerfeld and Welker - henceforth cited as SW - in connection with the behaviour of atoms at very high pressures, and the solution was published on the occasion of Pauli's 60th birthday celebration. At the time, it seemed that there was not much other connection with physical reality beyond a few simple aspects connected to the properties of atoms in solids, for which more appropriate models were soon developed. Thus, confined atoms attracted little attention until the advent of the metallofullerene, which provided the first example of a confined atom with properties quite closely related to those originally considered by SW. Since then, the problem has received much more attention, and many more new features of quantum confinement, quantum compression, the quantum Faraday cage, electronic reorganisation, cavity resonances, etc have been described, which are relevant to real systems. Also, a number of other situations have been uncovered experimentally to which quantum confinement is relevant. Thus, studies of the confined atom are now more numerous, and have been extended both in terms of the models used and the systems to which they can be applied. Connections to thermodynamics are explored through the properties of a confined two-level atom adapted from Einstein's celebrated model, and issues of dynamical screening of electromagnetic radiation by the confining shell are discussed in connection with the Faraday cage produced by a confining conducting shell. The

Energy confinement in Doublet III with high-Z limiters

Energy Technology Data Exchange (ETDEWEB)

Marcus, F.B.; Adcock, S.J.; Baker, D.R.; Blau, F.P.; Brooks, N.H.; Chase, R.P.; DeBoo, J.C.; Ejima, S.; Fairbanks, E.S.; Fisher, R.K.

1980-02-01

This report describes the experimental measurements and data analysis techniques used to evaluate the energy confinement in noncircular plasmas produced in Doublet III. Major aspects of the confinement measurements and analysis techniques are summarized. Machine parameters, diagnostic systems and discharge parameters relavent to the confinement measurements are given. Magnetic analysis techniques used to determine the plasma shape are reviewed. Scaling of the on-axis values of electron temperature, confinement time and Z/sub eff/ with plasma density is presented. Comparison with scaling results from other circular tokamaks is discussed. Numerical and analytic techniques developed for calculating the plasma energy confinement time and self-consistent profiles of density, temperature, current, and flux in non-circular geometries are described. These techniques are applied to the data and used to determine the central and global electron energy confinement time for a typical doublet plasma. Additional aspects of the confinement such as the radial dependence of the electron thermal conductivity and the estimated ion temperature are explored with the aid of a non-circular transport simulation code. The results of the confinement measurements are summarized and discussed. A brief summary of the theoretically expected effects of noncircularity on plasma confinement is included for reference as Appendix I.

ATR confinement leakage determination

International Nuclear Information System (INIS)

Kuan, P.; Buescher, B.J.

1998-01-01

The air leakage rate from the Advanced Test Reactor (ATR) confinement is an important parameter in estimating hypothesized accidental releases of radiation to the environment. The leakage rate must be determined periodically to assure that the confinement has not degraded with time and such determination is one of the technical safety requirements of ATR operation. This paper reviews the methods of confinement leakage determination and presents an analysis of leakage determination under windy conditions, which can complicate the interpretation of the determined leakage rates. The paper also presents results of analyses of building air exchange under windy conditions. High wind can enhance air exchange and this could increase the release rates of radioisotopes following an accident

Plasma confinement in the TMX tandem mirror

International Nuclear Information System (INIS)

Hooper, E.B. Jr.; Allen, S.L.; Casper, T.A.

1981-01-01

Plasma confinement in the Tandem Mirror Experiment (TMX) is described. Axially confining potentials are shown to exist throughout the central 20-cm core of TMX. Axial electron-confinement time is up to 100 times that of single-cell mirror machines. Radial transport of ions is smaller than axial transport near the axis. It has two parts at large radii: nonambipolar, in rough agreement with predictions from resonant-neoclassical transport theory, and ambipolar, observed near the plasma edge under certain conditions, accompanied by a low-frequency, m = 1 instability or strong turbulence

Isotope effect on confinement in DT plasmas

International Nuclear Information System (INIS)

Fukuyama, A.; Itoh, K.; Itoh, S.; Yagi, M.; Azumi, M.

1994-03-01

Isotope effect on the energy confinement time is discussed for the DT plasma. The transport theory which is based on the ballooning mode turbulence is applied. When the DT plasma is produced under the condition of β p >1, the energy confinement time of DT plasma (50% mixture) is expected to be about 1.2 times better than the D plasma with the same operation condition. (author)

Vortex Ring Dynamics in Radially Confined Domains

Science.gov (United States)

Stewart, Kelley; Niebel, Casandra; Jung, Sunghwan; Vlachos, Pavlos

2010-11-01

Vortex ring dynamics have been studied extensively in semi-infinite quiescent volumes. However, very little is known about vortex-ring formation in wall-bounded domains where vortex wall interaction will affect both the vortex ring pinch-off and propagation velocity. This study addresses this limitation and studies vortex formation in radially confined domains to analyze the affect of vortex-ring wall interaction on the formation and propagation of the vortex ring. Vortex rings were produced using a pneumatically driven piston cylinder arrangement and were ejected into a long cylindrical tube which defined the confined downstream domain. A range of confinement domains were studied with varying confinement diameters Velocity field measurements were performed using planar Time Resolved Digital Particle Image Velocimetry (TRDPIV) and were processed using an in-house developed cross-correlation PIV algorithm. The experimental analysis was used to facilitate the development of a theoretical model to predict the variations in vortex ring circulation over time within confined domains.

Comparative measurement of the neutral density and particle confinement time in EBT

International Nuclear Information System (INIS)

Glowienka, J.C.; Richards, R.K.

1985-11-01

The neutral density and particle confinement time in the ELMO Bumpy Torus-Scale Experiment (EBT-S) have been determined by two different techniques. These involve a spectroscopic measurement of molecular and atomic hydrogen emissions and a time-decay measurement of a fast-ion population using a diagnostic neutral beam. The results from both diagnostics exhibit identical trends for either estimate, although the absolute values differ by a factor of 2 to 3. The observed variations with fill gas pressure and microwave power from either technique are consistent with measurements of electron density and temperature. In this paper, the measurement techniques are discussed, and the results are compared in the context of consistency with independently observed plasma behavior. 6 refs., 7 figs

Advanced real-time control systems for magnetically confined fusion plasmas

International Nuclear Information System (INIS)

Goncalves, B.; Sousa, J.; Fernandes, H.; Rodrigues, A.P.; Carvalho, B.B.; Neto, A.; Varandas, C.A.F.

2008-01-01

Real-time control of magnetically confined plasmas is a critical issue for the safety, operation and high performance scientific exploitation of the experimental devices on regimes beyond the current operation frontiers. The number of parameters and the data volumes used for the plasma properties identification scale normally not only with the machine size but also with the technology improvements, leading to a great complexity of the plant system. A strong computational power and fast communication infrastructure are needed to handle in real-time this information, allowing just-in-time decisions to achieve the fusion critical plasma conditions. These advanced control systems require a tiered infrastructure including the hardware layer, the signal-processing middleware, real-time timing and data transport, the real-time operating system tools and drivers, the framework for code development, simulation, deployment and experiment parameterization and the human real-time plasma condition monitoring and management. This approach is being implemented at CFN by offering a vertical solution for the forthcoming challenges, including ITER, the first experimental fusion reactor. A given set of tools and systems are described on this paper, namely: (i) an ATCA based hardware multiple-input-multiple-output (MIMO) platform, PCI and PCIe acquisition and control modules; (ii) FPGA and DSP parallelized signal processing algorithms; (iii) a signal data and event distribution system over a 2.5/10Gb optical network with sub-microsecond latencies; (iv) RTAI and Linux drivers; and (v) the FireSignal, FusionTalk, SDAS FireCalc application tools. (author)

Surface motion and confinement potential for a microwave confined corona

International Nuclear Information System (INIS)

Ensley, D.L.

1979-07-01

Approximate time dependent solutions for surface velocities and potentials are given for a plane polarized microwave field confining a hot, over-dense plasma corona. Steady state solutions to Poissons' equation can be applied to the time dependent case, provided transit time effects are included. The product of ion pressure and potential wave (surface) velocity gives an average heating rate approx. 7/32 NKT 0 V/sub theta/ directly to the ions

Combined confinement system applied to tokamaks

International Nuclear Information System (INIS)

Ohkawa, Tihiro

1986-01-01

From particle orbit point of view, a tokamak is a combined confinement configuration where a closed toroidal volume is surrounded by an open confinement system like a magnetic mirror. By eliminating a cold halo plasma, the energy loss from the plasma becomes convective. The H-mode in diverted tokamaks is an example. Because of the favorable scaling of the energy confinement time with temperature, the performance of the tokamak may be significantly improved by taking advantage of this effect. (author)

Fivefold confinement time increase in the Madison Symmetric Torus using inductive poloidal current drive

International Nuclear Information System (INIS)

Stoneking, M.R.; Lanier, N.E.; Prager, S.C.; Sarff, J.S.; Sinitsyn, D.

1997-01-01

Current profile control is employed in the Madison Symmetric Torus [R. N. Dexter et al., Fusion Technol. 19, 131 (1991)] reversed field pinch to reduce the magnetic fluctuations responsible for anomalous transport. An inductive poloidal electric-field pulse is applied in the sense to flatten the parallel current profile, reducing the dynamo fluctuation amplitude required to sustain the equilibrium. This technique demonstrates a substantial reduction in fluctuation amplitude (as much as 50%), and improvement in energy confinement (from 1 to 5 ms); a record low fluctuation (0.8%) and record high temperature (615 eV) for this device were observed simultaneously during current drive experiments. Plasma beta increases by 50% and the Ohmic input power is three times lower. Particle confinement improves and plasma impurity contamination is reduced. The results of the transient current drive experiments provide motivation for continuing development of steady-state current profile control strategies for the reversed field pinch. copyright 1997 American Institute of Physics

Momentum Confinement at Low Torque

International Nuclear Information System (INIS)

Solomon, W.M.; Burrell, K.H.; deGrassie, J.S.; Budny, R.; Groebner, R.J.; Heidbrink, W.W.; Kinsey, J.E.; Kramer, G.J.; Makowski, M.A.; Mikkelsen, D.; Nazikian, R.; Petty, C.C.; Politzer, P.A.; Scott, S.D.; Van Zeeland, M.A.; Zarnstorff, M.C.

2007-01-01

Momentum confinement was investigated on DIII-D as a function of applied neutral beam torque at constant normalized β N , by varying the mix of co (parallel to the plasma current) and counter neutral beams. Under balanced neutral beam injection (i.e. zero total torque to the plasma), the plasma maintains a significant rotation in the co-direction. This 'intrinsic' rotation can be modeled as being due to an offset in the applied torque (i.e. an 'anomalous torque'). This anomalous torque appears to have a magnitude comparable to one co-neutral beam source. The presence of such an anomalous torque source must be taken into account to obtain meaningful quantities describing momentum transport, such as the global momentum confinement time and local diffusivities. Studies of the mechanical angular momentum in ELMing H-mode plasmas with elevated q min show that the momentum confinement time improves as the torque is reduced. In hybrid plasmas, the opposite effect is observed, namely that momentum confinement improves at high torque/rotation. The relative importance of E x B shearing between the two is modeled using GLF23 and may suggest a possible explanation.

The Physics Basis of ITER Confinement

International Nuclear Information System (INIS)

Wagner, F.

2009-01-01

ITER will be the first fusion reactor and the 50 year old dream of fusion scientists will become reality. The quality of magnetic confinement will decide about the success of ITER, directly in the form of the confinement time and indirectly because it decides about the plasma parameters and the fluxes, which cross the separatrix and have to be handled externally by technical means. This lecture portrays some of the basic principles which govern plasma confinement, uses dimensionless scaling to set the limits for the predictions for ITER, an approach which also shows the limitations of the predictions, and describes briefly the major characteristics and physics behind the H-mode--the preferred confinement regime of ITER.

Critical quench dynamics in confined systems.

Science.gov (United States)

Collura, Mario; Karevski, Dragi

2010-05-21

We analyze the coherent quantum evolution of a many-particle system after slowly sweeping a power-law confining potential. The amplitude of the confining potential is varied in time along a power-law ramp such that the many-particle system finally reaches or crosses a critical point. Under this protocol we derive general scaling laws for the density of excitations created during the nonadiabatic sweep of the confining potential. It is found that the mean excitation density follows an algebraic law as a function of the sweeping rate with an exponent that depends on the space-time properties of the potential. We confirm our scaling laws by first order adiabatic calculation and exact results on the Ising quantum chain with a varying transverse field.

Energy confinement in JT-60 lower hybrid current driven plasmas

International Nuclear Information System (INIS)

Ushigusa, K.; Imai, T.; Naito, O.; Ikeda, Y.; Tsuji, S.; Uehara, K.

1990-01-01

The energy confinement in high power lower hybrid current driven (LHCD) plasmas has been studied in the JT-60 tokamak. At a plasma current of 1 MA, the diamagnetically estimated energy confinement time in LHCD plasmas has almost the same value as the confinement time in ohmically heated plasmas at n-bar e ∼ 1.0x10 19 m -3 . The confinement time of high power LHCD plasmas (P LH E varies as to P LH α n e β I p 0 with α + β ∼ -0.3. (author). Letter-to-the-editor. 12 refs, 5 figs

Measurement of suprathermal electron confinement by cyclotron transmission

International Nuclear Information System (INIS)

Kirkwood, R.; Hutchinson, I.H.; Luckhardt, S.C.; Porkolab, M.; Squire, J.P.

1990-01-01

The confinement time of suprathermal electrons is determined experimentally from the distribution function determined via wave transmission measurements. Measurements of the lowest moment of the distribution perpendicular to the B field as a function of the parallel electron momentum as well as the global input power allow the suprathermal electron confinement time (τ se ) to be calculated during lower-hybrid and inductive current drive. Finite particle confinement is found to be the dominant energy loss term for the suprathermals and improves with plasma current and density

Characteristics of confining ohm-heated plasma in TRIAM-IM

International Nuclear Information System (INIS)

Hatae, Takaki; Yamagajyo, Takashi; Kawasaki, Shoji; Jotaki, Eriko; Fujita, Takaaki; Nakamura, Kazuo; Nakamura, Yukio; Ito, Satoshi

1994-01-01

In the initial experiment after the increase of the power of ohm heating power source for the superconducting strong magnetic field tokamak, TRIAM-IM, the measurement of the electron temperature distribution, ion temperature distribution and beam average electron density of ohm-heated plasma was carried out. By analyzing the experimental results, the dependence of the accumulated energy obtained from the temperature distribution and the time of energy confinement of beam average electron density became clear. Especially the time of energy confinement increased in proportion to the increase of beam average electron density when it is 6.5 x 10 12 /m 2 , and it was found that the time of energy confinement conforms to the Neo-Alcator proportional law. Moreover, by solving the heat transport equation for ions, the radial distribution of thermal diffusion coefficient for ions was calculated, and compared with that obtained by the new classic theory. As the result, it was found that the TRIAM-IM has ion confinement characteristics equivalent to those of other medium tokamaks. The experiment of producing ohm-heated plasma, the fitting of electron temperature and ion temperature, the density dependence of temperature, accumulated energy and the time of energy confinement, the time of energy confinement and the Neo-Alcator proportional law, the energy balance of ions and so on are reported. (K.I.)

Generating equilateral random polygons in confinement

International Nuclear Information System (INIS)

Diao, Y; Ernst, C; Montemayor, A; Ziegler, U

2011-01-01

One challenging problem in biology is to understand the mechanism of DNA packing in a confined volume such as a cell. It is known that confined circular DNA is often knotted and hence the topology of the extracted (and relaxed) circular DNA can be used as a probe of the DNA packing mechanism. However, in order to properly estimate the topological properties of the confined circular DNA structures using mathematical models, it is necessary to generate large ensembles of simulated closed chains (i.e. polygons) of equal edge lengths that are confined in a volume such as a sphere of certain fixed radius. Finding efficient algorithms that properly sample the space of such confined equilateral random polygons is a difficult problem. In this paper, we propose a method that generates confined equilateral random polygons based on their probability distribution. This method requires the creation of a large database initially. However, once the database has been created, a confined equilateral random polygon of length n can be generated in linear time in terms of n. The errors introduced by the method can be controlled and reduced by the refinement of the database. Furthermore, our numerical simulations indicate that these errors are unbiased and tend to cancel each other in a long polygon. (paper)

Energy confinement scaling from the international stellarator database

Energy Technology Data Exchange (ETDEWEB)

Stroth, U [Max-Planck-Institut fuer Plasmaphysik, Garching (Germany); Murakami, M; Dory, R A; Yamada, H; Okamura, S; Sano, F; Obiki, T

1995-09-01

An international stellarator database on global energy confinement is presented comprising data from the ATF, CHS and Heliotron E heliotron/torsatrons and the W7-A and W7-AS shearless stellarators. Regression expressions for the energy confinement time are given for the individual devices and the combined dataset. A comparison with tokamak L mode confinement is discussed on the basis of various scaling expressions. In order to make this database available to interested colleagues, the structure of the database and the parameter list are explained in detail. More recent confinement results incorporating data from enhanced confinement regimes such as H mode are reported elsewhere. (author).

Scaling laws for trace impurity confinement: a variational approach

International Nuclear Information System (INIS)

Thyagaraja, A.; Haas, F.A.

1990-01-01

A variational approach is outlined for the deduction of impurity confinement scaling laws. Given the forms of the diffusive and convective components to the impurity particle flux, we present a variational principle for the impurity confinement time in terms of the diffusion time scale and the convection parameter, which is a non-dimensional measure of the size of the convective flux relative to the diffusive flux. These results are very general and apply irrespective of whether the transport fluxes are of theoretical or empirical origin. The impurity confinement time scales exponentially with the convection parameter in cases of practical interest. (orig.)

Alternate fusion -- continuous inertial confinement

International Nuclear Information System (INIS)

Barnes, D.C.; Turner, L.; Nebel, R.A.

1993-01-01

The authors argue that alternate approaches to large tokamak confinement are appropriate for fusion applications if: (1) They do not require magnetic confinement of a much higher quality than demonstrated in tokamaks; (2) Their physics basis may be succinctly stated and experimentally tested; (3) They offer near-term applications to important technical problems; and (4) Their cost to proof-of-principle is low enough to be consistent with current budget realities. An approach satisfying all of these criteria is presented. Fusion systems based on continuous inertial confinement are described. In these approaches, the inertia of a nonequilibrium plasma is used to produce local concentrations of plasma density in space and/or time. One implementation (inertial electrostatic confinement) which has been investigated both experimentally and theoretically uses a system of electrostatic grids to accelerate plasma ions toward a spherical focus. This system produced a steady 2 x 10 10 D-T neutrons/second with an overall fusion gain of 10 -5 in a sphere of about 9 cm radius. Recent theoretical developments show how to raise the fusion gain to order unity or greater by replacing the internal grids by a combination of applied magnetic and electrostatic fields. In these approaches, useful thermonuclear conditions may be produced in a system as small as a few mm radius. Confinement is that of a nonneutralized plasma. A pure electron plasma with a radial beam velocity distribution is absolutely confined by an applied Penning trap field. Spherical convergence of the confined electrons forms a deep virtual cathode near r = 0, in which thermonuclear ions are absolutely confined at useful densities. The authors have examined the equilibrium, stability, and classical relaxation of such systems, and obtained many positive physics results. Equilibria exist for both pure electron and partially charge-neutralized systems with arbitrarily high core-plasma densities

Study of neutral particle behavior and particle confinement in JT-60U

International Nuclear Information System (INIS)

Takenaga, Hidenobu; Shimizu, Katsuhiro; Asakura, Nobuyuki; Shimada, Michiya; Kikuchi, Mitsuru; Tsuji-Iio, Shunji; Uchino, Kiichiro; Muraoka, Katsunori.

1995-07-01

In order to understand the particle confinement properties in JT-60U, the particle confinement time was estimated through analyses of the neutral particle behavior. First, the neutral particle transport simulation code DEGAS using a Monte-Carlo technique was combined with the simple divertor code for calculating the edge plasma parameters, and was developed to calculate under the experimental conditions in JT-60U. Then, the charged particle source in the main plasma due to the ionization of the neutral particles was evaluated from the analyses of the neutral particle penetration to the main plasma based on results of the simulation code and measurements of D α emission intensities. Finally, the particle confinement time was estimated from the analysis of particle balance. The analyses were performed systematically for the L-mode plasma and H-mode plasma of JT-60U, and a data base of the particle confinement time was obtained. The dependence of the particle confinement time on the plasma parameters and the relationship between the properties of the particle confinement and the energy confinement were examined. (author)

Analytical Solution for Time-drawdown Response to Constant Pumping from a Homogeneous, Confined Horizontal Aquifer with Unidirectional Flow

Science.gov (United States)

Parrish, K. E.; Zhang, J.; Teasdale, E.

2007-12-01

An exact analytical solution to the ordinary one-dimensional partial differential equation is derived for transient groundwater flow in a homogeneous, confined, horizontal aquifer using Laplace transformation. The theoretical analysis is based on the assumption that the aquifer is homogeneous and one-dimensional (horizontal); confined between impermeable formations on top and bottom; and of infinite horizontal extent and constant thickness. It is also assumed that there is only a single pumping well penetrating the entire aquifer; flow is everywhere horizontal within the aquifer to the well; the well is pumping with a constant discharge rate; the well diameter is infinitesimally small; and the hydraulic head is uniform throughout the aquifer before pumping. Similar to the Theis solution, this solution is suited to determine transmissivity and storativity for a two- dimensional, vertically confined aquifer, such as a long vertically fractured zone of high permeability within low permeable rocks or a long, high-permeability trench inside a low-permeability porous media. In addition, it can be used to analyze time-drawdown responses to pumping and injection in similar settings. The solution can also be used to approximate the groundwater flow for unconfined conditions if (1) the variation of transmissivity is negligible (groundwater table variation is small in comparison to the saturated thickness); and (2) the unsaturated flow is negligible. The errors associated with the use of the solution to unconfined conditions depend on the accuracies of the above two assumptions. The solution can also be used to assess the impacts of recharge from a seasonal river or irrigation canal on the groundwater system by assuming uniform, time- constant recharge along the river or canal. This paper presents the details for derivation of the analytical solution. The analytical solution is compared to numerical simulation results with example cases. Its accuracy is also assessed and

Effect of crowding and confinement on first-passage times: A model study

Science.gov (United States)

Antoine, C.; Talbot, J.

2016-06-01

We study the "color dynamics" of a hard-disk fluid confined in an annulus, as well as the corresponding hard-sphere system in three dimensions, using event-driven simulation in order to explore the effect of confinement and self-crowding on the search for targets. We compute the mean first-passage times (MFPTs) of red particles transiting from the outer to the inner boundary as well as those of blue particles passing from the inner to the outer boundary for different packing fractions and geometries. In the steady state the reaction rate, defined as the rate of collision of red particles with the inner boundary, is inversely proportional to the sum of the MFPTs. The reaction rate is wall mediated (ballistic) at low densities and diffusion controlled at higher densities and displays a maximum at intermediate densities. At moderate to high densities, the presence of layering has a strong influence on the search process. The numerical results for the reaction rate and MFPTs are compared with a ballistic model at low densities and a Smoluchowski approach with uniform diffusivities at higher densities. We discuss the reasons for the limited validity of the theoretical approaches. The maximum in the reaction rate is qualitatively well rendered by a Bosanquet-like approach that interpolates between the two regimes. Finally, we compute the position-dependent diffusivity from the MFPTs and observe that it is out of phase with the radial density.

Robust scaling laws for energy confinement time, including radiated fraction, in Tokamaks

Science.gov (United States)

Murari, A.; Peluso, E.; Gaudio, P.; Gelfusa, M.

2017-12-01

In recent years, the limitations of scalings in power-law form that are obtained from traditional log regression have become increasingly evident in many fields of research. Given the wide gap in operational space between present-day and next-generation devices, robustness of the obtained models in guaranteeing reasonable extrapolability is a major issue. In this paper, a new technique, called symbolic regression, is reviewed, refined, and applied to the ITPA database for extracting scaling laws of the energy-confinement time at different radiated fraction levels. The main advantage of this new methodology is its ability to determine the most appropriate mathematical form of the scaling laws to model the available databases without the restriction of their having to be power laws. In a completely new development, this technique is combined with the concept of geodesic distance on Gaussian manifolds so as to take into account the error bars in the measurements and provide more reliable models. Robust scaling laws, including radiated fractions as regressor, have been found; they are not in power-law form, and are significantly better than the traditional scalings. These scaling laws, including radiated fractions, extrapolate quite differently to ITER, and therefore they require serious consideration. On the other hand, given the limitations of the existing databases, dedicated experimental investigations will have to be carried out to fully understand the impact of radiated fractions on the confinement in metallic machines and in the next generation of devices.

Remarks on saturation of energy confinement in high density regime on LHD

International Nuclear Information System (INIS)

Yamada, Hiroshi; Morita, Shigeru; Murakami, Sadayoshi

2003-01-01

A study on energy confinement times in currentless helical plasmas has indicated a preferable density dependence like τ E ∝ n-bar e 0.5-0.6 . However, saturation of energy confinement time has been often observed during the density ramping-up phase by gas puffing in NBI heated plasmas in LHD. The power balance analysis indicates that the thermal diffusivity is improved by the increase in local density while the global energy confinement time loses the dependence on the density. The flat or hollow density profile, which is distinguished in the density-ramping phase, promotes a broad heat power deposition. This change explains the apparent contradiction between the density dependence of the thermal diffusivity and the global energy confinement time. This result suggests that central heating can maintain a favorable density dependence of the energy confinement time in the high density regime. (author)

Confinement of multiply charged ions in an ECRH mirror plasma

International Nuclear Information System (INIS)

Petty, C.C.

1989-06-01

This thesis is an experimental study of multiply charged ions in the Constance B mirror experiment. By measuring the ion densities, end loss fluxes and ion temperatures, the parallel confinement times for the first five charge states of oxygen and neon plasmas are determined. The parallel ion confinement times increase with charge state and peak on axis, both indications of an ion-confining potential dip created by the hot electrons. The radial profile of ion end loss is usually hollow due to large ion radial transport (τ paralleli ∼ τ perpendiculari ), with the peak fluxes occurring at the edge of the electron cyclotron resonance zone. Several attempts are made to increase the end loss of selected ion species. Using minority ICRH, the end loss flux of resonant ions increases by 20% in cases when radial transport induced by ICRH is not too severe. A large antenna voltage can also extinguish the plasma. By adding helium to an oxygen plasma, the end loss of O 6+ increases by 80% due to decreased ion radial transport. An ion model is developed to predict the ion densities, end loss fluxes and confinement times in the plasma center using the ion particle balance equations, the quasineutrality condition and theoretical confinement time formulas. The model generally agrees with the experimental data for oxygen and neon plasmas to within experimental error. Under certain conditions spatial diffusion appears to determine the parallel ion confinement time of the highest charge states. For oxygen plasmas during ICRH, the measured parallel confinement time of the resonant ions is much shorter than their theoretical value, probably due to rf diffusion of the ions into the loss cone. 58 refs., 101 figs., 16 tabs

Global energy confinement in JT-60 neutral beam heated L-mode discharges

International Nuclear Information System (INIS)

Naito, O.; Hosogane, N.; Tsuji, S.; Ushigusa, K.; Yoshida, H.

1990-01-01

The global energy confinement characteristics of neutral beam heated JT-60 discharges are presented. There is a difference in the dependence of the energy confinement time on the plasma current between limiter and divertor discharges. For limiter discharges, the energy confinement increases with plasma current up to 3.2 MA, whereas for divertor discharges this improvement saturates when the safety factor drops below 3, independent of the location of the X-point. The JT-60 L-mode results indicate that the deterioration in energy confinement for q < 3, which is also found in H-mode regimes of other devices, may be a universal characteristic of divertor discharges. Regarding the scaling with plasma size, it is shown that the global/incremental confinement time increases with plasma minor radius. For sufficiently large plasmas, however, the global/incremental confinement time is no longer a function of minor radius. (author). 13 refs, 14 figs

Hermitian relativity, chromodynamics and confinement

International Nuclear Information System (INIS)

Treder, H.J.

1983-01-01

The extension of the Riemann metrics of General Relativity to the complex domain (substitution of the symmetry conditions for the fundamental tensor, the affinity and the Ricci curvature by the conditions of hermicity) leads to a 'Generalized Theory of Gravity' (Einstein) describing the Newton-Einstein gravodynamics combined with the chromodynamics of quarks. The interaction of gravodynamics and chromodynamics implied by the Einstein-Schroedinger field equations of the hermitian relativity theory enforces the 'confinement'. The 'confinement' prevents the gravitational potential from divergence which would result in the lack of a Riemann space-time metric

Confinement studies of ohmically heated plasmas in TFTR

International Nuclear Information System (INIS)

Efthimion, P.C.; Bretz, N.L.; Bell, M.G.

1985-03-01

Systematic scans of density in large deuterium plasmas (a = 0.83 m) at several values of plasma current and toroidal magnetic field strength indicate that the total energy confinement time, tau/sub E/, is proportional to the line-average density anti n/sub e/ and the limiter q. Confinement times of approx. 0.3 s have been observed for anti n/sub e/ = 2.8 x 10 19 m -3 . Plasma size scaling experiments with plasmas of minor radii a = 0.83, 0.69, 0.55, and 0.41 m at constant limiter q reveal a confinement dependence on minor radius. The major-radius dependence of tau/sub E/, based on a comparison between TFTR and PLT results, is consistent with R 2 scaling. From the power balance, the thermal diffusivity chi/sub e/ is found to be significantly less than the INTOR value. In the a = 0.41 m plasmas, saturation of confinement is due to neoclassical ion conduction (chi/sub i/ neoclassical >> chi/sub e/)

Investigation of impurity confinement in lower hybrid wave heated plasma on EAST tokamak

Science.gov (United States)

Xu, Z.; Wu, Z. W.; Zhang, L.; Gao, W.; Ye, Y.; Chen, K. Y.; Yuan, Y.; Zhang, W.; Yang, X. D.; Chen, Y. J.; Zhang, P. F.; Huang, J.; Wu, C. R.; Morita, S.; Oishi, T.; Zhang, J. Z.; Duan, Y. M.; Zang, Q.; Ding, S. Y.; Liu, H. Q.; Chen, J. L.; Hu, L. Q.; Xu, G. S.; Guo, H. Y.; the EAST Team

2018-01-01

The transient perturbation method with metallic impurities such as iron (Fe, Z  =  26) and copper (Cu, Z  =  29) induced in plasma-material interaction (PMI) procedure is used to investigate the impurity confinement characters in lower hybrid wave (LHW) heated EAST sawtooth-free plasma. The dependence of metallic impurities confinement time on plasma parameters (e.g. plasma current, toroidal magnetic field, electron density and heating power) are investigated in ohmic and LHW heated plasma. It is shown that LHW heating plays an important role in the reduction of the impurity confinement time in L-mode discharges on EAST. The impurity confinement time scaling is given as 42IP0.32Bt0.2\\overline{n}e0.43Ptotal-0.4~ on EAST, which is close to the observed scaling on Tore Supra and JET. Furthermore, the LHW heated high-enhanced-recycling (HER) H-mode discharges with ~25 kHz edge coherent modes (ECM), which have lower impurity confinement time and higher energy confinement time, provide promising candidates for high performance and steady state operation on EAST.

Improved plasma confinement by modulated toroidal current on HT-7 superconducting tokamak

International Nuclear Information System (INIS)

Mao Jianshan; Zhao Junyu; Shen Biao; Luo Jiarong

2004-01-01

The improved confinement phase was observed during modulating toroidal current on the Hefei superconducting Tokamak-7 (HT-7). This improved plasma confinement phase is characterized by suppressing magnetohydrodynamic (MHD) instabilities effectively, thus increased the central line averaged electron density and the central electron temperature about 33%, out-put steeper density profiles, and reduced hydrogen radiation from the edge as well. The global energy confinement time was increased by 27%-45%; The impurity radiation was reduced by modulation of plasma toroidal current; particle confinement time was increased about two times; a stronger radial negative electric field formed inside the limiter. The radial electric field during modulating current was calculated and disscused. (authors)

Fusion, magnetic confinement

International Nuclear Information System (INIS)

Berk, H.L.

1992-01-01

An overview is presented of the principles of magnetic confinement of plasmas for the purpose of achieving controlled fusion conditions. Sec. 1 discusses the different nuclear fusion reactions which can be exploited in prospective fusion reactors and explains why special technologies need to be developed for the supply of tritium or 3 He, the probable fuels. In Sec. 2 the Lawson condition, a criterion that is a measure of the quality of confinement relative to achieving fusion conditions, is explained. In Sec. 3 fluid equations are used to describe plasma confinement. Specific confinement configurations are considered. In Sec. 4 the orbits of particle sin magneti and electric fields are discussed. In Sec. 5 stability considerations are discussed. It is noted that confinement systems usually need to satisfy stability constraints imposed by ideal magnetohydrodynamic (MHD) theory. The paper culminates with a summary of experimental progress in magnetic confinement. Present experiments in tokamaks have reached the point that the conditions necessary to achieve fusion are being satisfied

Dynamics of water confined in clay minerals

International Nuclear Information System (INIS)

Le Caer, S.; Pommeret, S.; Renault, J.Ph.; Lima, M.; Righini, R.; Gosset, D.; Simeone, D.; Bergaya, F.

2012-01-01

Ultrafast infrared spectroscopy of the O-D stretching mode of dilute HOD in H 2 O probes the local environment and the hydrogen bond network of confined water. The dynamics of water molecules confined in the interlayer space of montmorillonites (Mt) and in interaction with two types of cations (Li + and Ca 2+ ) but also with the negatively charged siloxane surface are studied. The results evidence that the OD vibrational dynamics is significantly slowed down in confined media: it goes from 1.7 ps in neat water to 2.6 Ps in the case of Li + cations with two water pseudo-layers (2.2-2.3 ps in the case of Ca 2+ cations) and to 4.7 ps in the case of Li + cations with one water pseudo-layer. No significant difference between the two cations is noticed. In this 2D confined geometry (the interlayer space being about 0.6 nm for two water pseudo-layers), the relaxation time constants obtained are comparable to the ones measured in analogous concentrated salt solutions. Nevertheless, and in strong opposition to the observations performed in the liquid phase, anisotropy experiments evidence the absence of rotational motions on a 5 ps time scale, proving that the hydrogen bond network in the interlayer space of the clay mineral is locked at this time scale. (authors)

Classical impurity ion confinement in a toroidal magnetized fusion plasma.

Science.gov (United States)

Kumar, S T A; Den Hartog, D J; Caspary, K J; Magee, R M; Mirnov, V V; Chapman, B E; Craig, D; Fiksel, G; Sarff, J S

2012-03-23

High-resolution measurements of impurity ion dynamics provide first-time evidence of classical ion confinement in a toroidal, magnetically confined plasma. The density profile evolution of fully stripped carbon is measured in MST reversed-field pinch plasmas with reduced magnetic turbulence to assess Coulomb-collisional transport without the neoclassical enhancement from particle drift effects. The impurity density profile evolves to a hollow shape, consistent with the temperature screening mechanism of classical transport. Corroborating methane pellet injection experiments expose the sensitivity of the impurity particle confinement time to the residual magnetic fluctuation amplitude.

High-confinement NBI discharges in the W7-AS stellarator

International Nuclear Information System (INIS)

Stroth, U.; Baldzuhn, J.; Geiger, J.; Geist, T.; Giannone, L.; Hartfuss, H.-J.; Hirsch, M.; Jaenicke, R.; Kick, M.; Koponen, J.P.; Kuehner, G.; Penningsfeld, F.-P.; Wagner, F.

1998-01-01

In W7-AS, the longest energy confinement times were achieved in neutral beam injection heated (NBI-heated) discharges under low wall-recycling conditions. Low recycling is needed to control the density at line-averaged values of n-bar e approx. 10 20 m -3 . Under these conditions, confinement was improved by a factor of two above the common scaling estimate. The reduction of radial transport is concentrated into a layer at about two-thirds of the plasma radius. In this region steep pressure gradients and a strong gradient in the radial electric field develop. Specific for the discharges is the slow transition to improved confinement, lasting up to three energy confinement times. Since the measured electric field is consistent with the neoclassical ambipolar field, this high-confinement mode could be an example where sheared plasma flow as created by the neoclassical radial electric field leads to a suppression of anomalous transport. (author)

High-confinement NBI discharges in the W7-AS stellarator

Energy Technology Data Exchange (ETDEWEB)

Stroth, U; Baldzuhn, J; Geiger, J; Geist, T; Giannone, L.; Hartfuss, H -J; Hirsch, M; Jaenicke, R; Kick, M; Koponen, J P; Kuehner, G; Penningsfeld, F -P; Wagner, F [Max-Planck-Institut fuer Plasmaphysik, EURATOM Association, D-85748 Garching (Germany)

1998-08-01

In W7-AS, the longest energy confinement times were achieved in neutral beam injection heated (NBI-heated) discharges under low wall-recycling conditions. Low recycling is needed to control the density at line-averaged values of n-bar{sub e} approx. 10{sup 20}m{sup -3}. Under these conditions, confinement was improved by a factor of two above the common scaling estimate. The reduction of radial transport is concentrated into a layer at about two-thirds of the plasma radius. In this region steep pressure gradients and a strong gradient in the radial electric field develop. Specific for the discharges is the slow transition to improved confinement, lasting up to three energy confinement times. Since the measured electric field is consistent with the neoclassical ambipolar field, this high-confinement mode could be an example where sheared plasma flow as created by the neoclassical radial electric field leads to a suppression of anomalous transport. (author)

Investigation of the Energy Confinement in Ohmic and LHCD Plasmas in HT-7

International Nuclear Information System (INIS)

Zhang Xiaoqing; Wan Baonian; Shen Biao; Hu Xiwei; Qian Jinping; Fan Hengyu; Ding Yonghua

2006-01-01

Investigation of the energy confinement in ohmic and lower hybrid current drive (LHCD) plasmas in HT-7 has been performed. In ohmic discharges at low densities the global energy confinement time τ E increases almost linearly with the density, saturates at a critical density (2.5 x 10 13 /cm 3 for HT-7) and is nearly constant at higher densities. The energy confinement time is in good agreement with the Neo-Alcator scaling law at different densities and currents. In the LHCD plasmas the global energy confinement time similar to that of the L-mode discharges has been observed to be in good agreement with the low confinement mode (L mode) scaling law of ITER89-P in higher electron density and plasma current

Bifurcated equilibria in centrifugally confined plasma

International Nuclear Information System (INIS)

Shamim, I.; Teodorescu, C.; Guzdar, P. N.; Hassam, A. B.; Clary, R.; Ellis, R.; Lunsford, R.

2008-01-01

A bifurcation theory and associated computational model are developed to account for abrupt transitions observed recently on the Maryland Centrifugal eXperiment (MCX) [R. F. Ellis et al. Phys. Plasmas 8, 2057 (2001)], a supersonically rotating magnetized plasma that relies on centrifugal forces to prevent thermal expansion of plasma along the magnetic field. The observed transitions are from a well-confined, high-rotation state (HR-mode) to a lower-rotation, lesser-confined state (O-mode). A two-dimensional time-dependent magnetohydrodynamics code is used to simulate the dynamical equilibrium states of the MCX configuration. In addition to the expected viscous drag on the core plasma rotation, a momentum loss term is added that models the friction of plasma on the enhanced level of neutrals expected in the vicinity of the insulators at the throats of the magnetic mirror geometry. At small values of the external rotation drive, the plasma is not well-centrifugally confined and hence experiences the drag from near the insulators. Beyond a critical value of the external drive, the system makes an abrupt transition to a well-centrifugally confined state in which the plasma has pulled away from the end insulator plates; more effective centrifugal confinement lowers the plasma mass near the insulators allowing runaway increases in the rotation speed. The well-confined steady state is reached when the external drive is balanced by only the viscosity of the core plasma. A clear hysteresis phenomenon is shown.

The effect of ELMs on energy confinement in JET

International Nuclear Information System (INIS)

Zhang, W.; Tubbing, B.J.D.; Ward, D.J.

1998-01-01

The effect of ELMs on energy confinement in JET has been analysed. ELMs are characterized using D α emission which is decomposed into two components, a baseline level with superimposed pulses due to the ELMs. The analysis of the experimental data shows that the D α baseline, which reflects the neutral pressure at the plasma edge, is an important parameter in determining the energy confinement deterioration. The origin of the D α baseline is either from the neutralization of plasma particles which are expelled by the ELM pulses, or from external gas puffing. An ELM severity parameter, taking into account both the D α baseline and the ELM pulses, is defined. The energy confinement time normalized to the energy confinement time of ELM free phase, τ B /τ H , decreases linearly as the ELM severity increases. The results are independent of divertor configurations. (author)

Improved GAMMA 10 tandem mirror confinement in high density plasma

International Nuclear Information System (INIS)

Yatsu, K.; Cho, T.; Higaki, H.; Hirata, M.; Hojo, H.; Ichimura, M.; Ishii, K.; Ishimoto, Y.; Itakura, A.; Katanuma, I.; Kohagura, J.; Minami, R.; Nakashima, Y.; Numakura, T.; Saito, T.; Saosaki, S.; Takemura, Y.; Tatematsu, Y.; Yoshida, M.; Yoshikawa, M.

2003-01-01

GAMMA 10 experiments have advanced in high density experiments after the last IAEA fusion energy conference in 2000 where we reported the production of the high density plasma through use of ion cyclotron range of frequency heating at a high harmonic frequency and neutral beam injection in the anchor cells. However, the diamagnetic signal of the plasma decreased when electron cyclotron resonance heating was applied for the potential formation. Recently a high density plasma has been obtained without degradation of the diamagnetic signal and with much improved reproducibility than before. The high density plasma was attained through adjustment of the spacing of the conducting plates installed in the anchor transition regions. The potential confinement of the plasma has been extensively studied. Dependences of the ion confinement time, ion-energy confinement time and plasma confining potential on plasma density were obtained for the first time in the high density region up to a density of 4x10 18 m -3 . (author)

Perspectives on confinement in helical systems

International Nuclear Information System (INIS)

Itoh, Kimitaka; Itoh, Sanae

1989-01-01

A review on recent experimental results and theoretical models on anomalous transport and density limit in toroidal helical devices is presented. Importance of transport problems is discussed. Experiments on Heliotron-E, Wendelstein-VIIA and new devices, i.e., ATF, Wendelstein-VIIAS and CHS, are reviewed and an overview on confinement property is given. From recent experimental results one sees that there are anomalous transport, which increases with temperature, and density limit, and that they limit the energy confinement time as well as the attainable beta value. The confinement characteristics of the scrape off layer plasma and loss cone loss are discussed, and perspectives on the high temperature plasma are given. These anomalous transport and density limit will be difficult obstacles in realizing a reactor grade plasma in helical systems. It is an urgent task to draw a realistic picture of the confinement based on the present data base. The relevant knowledge now would be critically essential for the successful development of the research in 1990's. (author) 102 refs

Fluctuations and confinement in ATF

International Nuclear Information System (INIS)

Isler, R.C.; Harris, J.H.; Murakami, M.

1993-01-01

In the period immediately prior to the suspension of ATF operation in November, 1991, a great deal of emphasis was palced on investigations of the fundamental mechanisms controlling confinement in this device. At that time, measurements of the density fluctuations throughout the plasma volume indicated the existence of theoretically predicted dissipative trapped electron and resistive interchange instabilities. These identifications were supported by results of dynamic configuration scans of the magnetic fields during which the extent of the magnetic well, shear, and fraction of confined trapped particles were changed continuously. Interpretation of the data from these experiments has been an ongoing exercise. Most recently, analysis of discharges employing strong gas puffing to change density gradients and fluctuation levels have strengthened the view that dissipative trapped electron modes may be present but do not play a significant direct role in energy transport. The present paper summarizes the current understanding concerning the identification of instabilities and their relationship to confinement in ATF

Energy confinement of tokamak plasma with consideration of bootstrap current effect

International Nuclear Information System (INIS)

Yuan Ying; Gao Qingdi

1992-01-01

Based on the η i -mode induced anomalous transport model of Lee et al., the energy confinement of tokamak plasmas with auxiliary heating is investigated with consideration of bootstrap current effect. The results indicate that energy confinement time increases with plasma current and tokamak major radius, and decreases with heating power, toroidal field and minor radius. This is in reasonable agreement with the Kaye-Goldston empirical scaling law. Bootstrap current always leads to an improvement of energy confinement and the contraction of inversion radius. When γ, the ratio between bootstrap current and total plasma current, is small, the part of energy confinement time contributed from bootstrap current will be about γ/2

Confinement models for gluons

International Nuclear Information System (INIS)

Khadkikar, S.B.; Vinodkumar, P.C.

1987-04-01

Confinement model for gluons using a 'colour super current' is formulated. An attempt has been made to derive a suitable dielectric function corresponding to the current confinement model. A simple inhomogeneous dielectric confinement model for gluons is studied for comparison. The model Hamiltonians are second quantized and the glueball states are constructed. The spurious motion of the centre of confinement is accounted for. The results of the current confinement scheme are found to be in good agreement with the experimental candidates for glueballs. (author). 16 refs, 3 tabs

Comments on confinement criteria

International Nuclear Information System (INIS)

Kurak, V.; Schroer, B.; Swieca, J.A.

1977-01-01

For a QED 2 model with SU(n) flavour, the nature of the physical states space is more subtle than one expects on the basis of the loop criterion for confinement. One may have colour confinement without confinement of the fundamental flavour representation. Attempts to formulate confinement criteria in which the quark fields play a more fundamental role are discussed [pt

Holographic repulsion and confinement in gauge theory

Science.gov (United States)

Husain, Viqar; Kothawala, Dawood

2013-02-01

We show that for asymptotically anti-de Sitter (AdS) backgrounds with negative energy, such as the AdS soliton and regulated negative-mass AdS-Schwarzshild metrics, the Wilson loop expectation value in the AdS/CFT conjecture exhibits a Coulomb to confinement transition. We also show that the quark-antiquark (q \\bar{q}) potential can be interpreted as affine time along null geodesics on the minimal string worldsheet and that its intrinsic curvature provides a signature of transition to confinement phase. Our results suggest a generic (holographic) relationship between confinement in gauge theory and repulsive gravity, which in turn is connected with singularity avoidance in quantum gravity. Communicated by P R L V Moniz

Comparison of confinement in resistive-shell reversed-field pinch devices with two different magnetic shell penetration times

International Nuclear Information System (INIS)

Gravestijn, R M; Drake, J R; Hedqvist, A; Rachlew, E

2004-01-01

A loop voltage is required to sustain the reversed-field pinch (RFP) equilibrium. The configuration is characterized by redistribution of magnetic helicity but with the condition that the total helicity is maintained constant. The magnetic field shell penetration time, τ s , has a critical role in the stability and performance of the RFP. Confinement in the EXTRAP device has been studied with two values of τ s , first (EXTRAP-T2) with tau s of the order of the typical relaxation cycle timescale and then (EXTRAP-T2R) with τ s much longer than the relaxation cycle timescale, but still much shorter than the pulse length. Plasma parameters show significant improvements in confinement in EXTRAP-T2R. The typical loop voltage required to sustain comparable electron poloidal beta values is a factor of 3 lower in the EXTRAP-T2R device. The improvement is attributed to reduced magnetic turbulence

Field reversal experiments (FRX). [Equilibrium, confinement, and stability

Energy Technology Data Exchange (ETDEWEB)

Linford, R.K.; Armstrong, W.T.; Platts, D.A.; Sherwood, E.G.

1978-01-01

The equilibrium, confinement, and stability properties of the reversed-field configuration (RFC) are being studied in two theta-pinch facilities. The RFC is an elongated toroidal plasma confined in a purely poloidal field geometry. The open field lines of the linear theta pinch support the closed-field RFC much like the vertical field centers the toroidal plasma in a tokamak. Depending on stability and confinement properties, the RFC might be used to greatly reduce the axial losses in linear fusion devices such as mirrors, theta pinches, and liners. The FRX systems produce RFC's with a major radius R = 2-6 cm, minor radius a approximately 2 cm, and a total length l approximately 35 cm. The observed temperatures are T/sub e/ approximately 100 eV and T/sub i/ = 150-350 eV with a peak density n approximately 2 x 10/sup 15/ cm/sup -3/. After the plasma reaches equilibrium, the RFC remains stable for up to 30 ..mu..s followed by the rapid growth of the rotational m = 2 instability, which terminates the confinement. During the stable equilibrium, the particle and energy confinement times are more than 10 times longer than in an open-field system. The behavior of the m = 2 mode qualitatively agrees with the theoretically predicted instability for rotational velocities exceeding some critical value.

Cluster Analysis of the International Stellarator Confinement Database

International Nuclear Information System (INIS)

Kus, A.; Dinklage, A.; Preuss, R.; Ascasibar, E.; Harris, J. H.; Okamura, S.; Yamada, H.; Sano, F.; Stroth, U.; Talmadge, J.

2008-01-01

Heterogeneous structure of collected data is one of the problems that occur during derivation of scalings for energy confinement time, and whose analysis tourns out to be wide and complicated matter. The International Stellarator Confinement Database [1], shortly ISCDB, comprises in its latest version 21 a total of 3647 observations from 8 experimental devices, 2067 therefrom beeing so far completed for upcoming analyses. For confinement scaling studies 1933 observation were chosen as the standard dataset. Here we describe a statistical method of cluster analysis for identification of possible cohesive substructures in ISDCB and present some preliminary results

Analysis of a global energy confinement database for JET ohmic plasmas

International Nuclear Information System (INIS)

Bracco, G.; Thomsen, K.

1997-01-01

A database containing global energy confinement data for JET ohmic plasmas in the campaigns from 1984 to 1992 has been established. An analysis is presented of this database and the results are compared with data from other tokamaks, such as the Axially Symmetric Divertor Experiment (ASDEX), Frascati Tokamak Upgrade (FTU) and Tore Supra. The trends of JET ohmic confinement appear to be similar to those observed on other tokamaks: a linear dependence of the global energy confinement time on density is observed up to a density value where a saturation is attained; this density value defines the border between the linear and the saturated ohmic confinement regimes; this border is shifted towards higher density values if the q value of the discharge is decreased; the global confinement time in the saturated ohmic regime increases less than linearly with the value of the magnetic field. (author). 20 refs, 13 figs, 4 tabs

Waste-acceptance criteria for greater confinement disposal

International Nuclear Information System (INIS)

Gilbert, T.L.; Meshkov, N.K.

1987-01-01

A methodology for establishing waste-acceptance criteria based on quantitative performance factors that characterize the confinement capabilities of a waste disposal site and facility has been developed. The methodology starts from the basic objective of protecting public health and safety by providing assurance that disposal of the waste will not result in a radiation dose to any member of the general public, in either the short or long term, in excess of an established basic dose limit. The method is based on an explicit, straight-forward, and quantitative relationship among individual risk, confinement capabilities, and waste characteristics. A key aspect of the methodology is introduction of a confinement factor that characterizes the overall confinement capability of a particular facility and can be used for quantitative assessments of the performance of different disposal sites and facilities, as well as for establishing site-specific waste acceptance criteria. Confinement factors are derived by means of site-specific pathway analyses. They make possible a direct and simple conversion of a basic dose limit into waste-acceptance criteria, specified as concentration limits on radionuclides in the waste streams and expressed in quantitative form as a function of parameters that characterize the site, facility design, waste containers, and waste form. Waste acceptance criteria can be represented visually as activity/time plots for various waste streams. These plots show the concentrations of radionuclides in a waste stream as a function of time and permit a visual, quantitative assessment of long-term performance, relative risks from different radionuclides in the waste stream, and contributions from ingrowth. 13 references, 7 figures

Waste-acceptance criteria for greater-confinement disposal

International Nuclear Information System (INIS)

Gilbert, T.L.; Meshkov, N.K.

1986-01-01

A methodology for establishing waste-acceptance criteria based on quantitative performance factors that characterize the confinement capabilities of a waste-disposal site and facility has been developed. The methodology starts from the basic objective of protecting public health and safety by providing assurance that dispsoal of the waste will not result in a radiation dose to any member of the general public, in either the short or long term, in excess of an established basic dose limit. The method is based on an explicit, straightforward, and quantitative relationship among individual risk, confinement capabilities, and waste characteristics. A key aspect of the methodology is the introduction of a confinement factor that characterizes the overall confinement capability of a particular facility and can be used for quantitative assessments of the performance of different disposal sites and facilities, as well as for establishing site-specific waste-acceptance criteria. Confinement factors are derived by means of site-specific pathway analyses. They make possible a direct and simple conversion of a basic dose limit into waste-acceptance criteria, specified as concentration limits on radionuclides in the waste streams and expressed in quantitative form as a function of parameters that characterize the site, facility design, waste containers, and waste form. Waste-acceptance criteria can be represented visually as activity/time plots for various waste streams. These plots show the concentrations of radionuclides in a waste stream as a function of time and permit a visual, quantitative assessment of long-term performance, relative risks from different radionuclides in the waste stream, and contributions from ingrowth. 13 refs

Generating equilateral random polygons in confinement II

International Nuclear Information System (INIS)

Diao, Y; Ernst, C; Montemayor, A; Ziegler, U

2012-01-01

In this paper we continue an earlier study (Diao et al 2011 J. Phys. A: Math. Theor. 44 405202) on the generation algorithms of random equilateral polygons confined in a sphere. Here, the equilateral random polygons are rooted at the center of the confining sphere and the confining sphere behaves like an absorbing boundary. One way to generate such a random polygon is the accept/reject method in which an unconditioned equilateral random polygon rooted at origin is generated. The polygon is accepted if it is within the confining sphere, otherwise it is rejected and the process is repeated. The algorithm proposed in this paper offers an alternative to the accept/reject method, yielding a faster generation process when the confining sphere is small. In order to use this algorithm effectively, a large, reusable data set needs to be pre-computed only once. We derive the theoretical distribution of the given random polygon model and demonstrate, with strong numerical evidence, that our implementation of the algorithm follows this distribution. A run time analysis and a numerical error estimate are given at the end of the paper. (paper)

Gluon confinement

International Nuclear Information System (INIS)

Novello, M.; Lorenci, V.A. de; Elbaz, E.

1997-02-01

In this paper we present a new model for a gauge field theory such that self-interacting spin-one particles can be confined in a compact domain. The necessary conditions to produce the confining potential appear already in the properties of the eikonal structure generated by the particular choice of the dynamics. (author)

Building solids inside nano-space: from confined amorphous through confined solvate to confined 'metastable' polymorph.

Science.gov (United States)

Nartowski, K P; Tedder, J; Braun, D E; Fábián, L; Khimyak, Y Z

2015-10-14

The nanocrystallisation of complex molecules inside mesoporous hosts and control over the resulting structure is a significant challenge. To date the largest organic molecule crystallised inside the nano-pores is a known pharmaceutical intermediate - ROY (259.3 g mol(-1)). In this work we demonstrate smart manipulation of the phase of a larger confined pharmaceutical - indomethacin (IMC, 357.8 g mol(-1)), a substance with known conformational flexibility and complex polymorphic behaviour. We show the detailed structural analysis and the control of solid state transformations of encapsulated molecules inside the pores of mesoscopic cellular foam (MCF, pore size ca. 29 nm) and controlled pore glass (CPG, pore size ca. 55 nm). Starting from confined amorphous IMC we drive crystallisation into a confined methanol solvate, which upon vacuum drying leads to the stabilised rare form V of IMC inside the MCF host. In contrast to the pure form, encapsulated form V does not transform into a more stable polymorph upon heating. The size of the constraining pores and the drug concentration within the pores determine whether the amorphous state of the drug is stabilised or it recrystallises into confined nanocrystals. The work presents, in a critical manner, an application of complementary techniques (DSC, PXRD, solid-state NMR, N2 adsorption) to confirm unambiguously the phase transitions under confinement and offers a comprehensive strategy towards the formation and control of nano-crystalline encapsulated organic solids.

Impact of confinement physics on reactor design and economics

International Nuclear Information System (INIS)

DeFreece, D.A.; Campbell, R.B.; Waganer, L.M.

1977-01-01

A variety of confinement laws were employed in a transient, zero dimensional plasma code, which was coupled to the TOCOMO systems code. The purpose was to determine the impact of the confinement laws on reactor design, power costs and changes in the utility interface. A satisfactory reactor and power plant has been defined for the large majority of combinations of confinement law, power plant size and plasma shape. Trapped ion mode (TIM) has been the easiest to work with, since the plasma is thermally stable with a good power density and minimal alpha particle build up. Neoclassical and pseudoclassical along with TEMII result in satisfactory reactor performance, but require active feedback control (by injecting impurities) to prevent plasma temperature excursions. These laws also require some form and degree of confinement time spoiling to allow long burn times, otherwise, alpha particles build up to an unacceptable level. TEM I results in thermal equilibrium at 5 keV and must be driven to provide a reactor quality plasma. The continuous injected power required for a 4300 MW thermal reactor is 540 MW. This added to the other circulating loads results in a net power output of 600 MWe at a very high relative cost. Daughney (empirical) confinement results in a satisfactory, competitive reactor

Scalings of energy confinement and density limit in stellarator/heliotron

International Nuclear Information System (INIS)

Sudo, S.; Takeiri, Y.; Zushi, H.; Sano, F.; Itoh, K.; Kondo, K.; Iiyoshi, A.

1989-04-01

Empirical scaling of energy confinement observed experimentally in stellarator/heliotron (Heliotron E, Wendelstein 7A, L2, Heliotron DR) under the condition that plasmas are heated by ECH and/or NbI is proposed. Empirical scaling of density limit obtainable under the optimum condition is proposed. These scalings are compared with those of tokamaks. The energy confinement scaling has similar power dependence as 'L mode scaling' of tokamaks. The density limit scaling seems also to indicate the upper limit of achievable density in many tokamaks. Combining the energy confinement time and the density limit scaling a transport-limited beta value is also deduced. Thus, from the viewpoint of designing a machine, there should be some compromise in determing magnetic field strength on plasma axis, average minor radius and major radius, because their dependence on confinement time and transport-limited beta value is contradicting. (J.P.N.)

Sustainment of high confinement in JT-60U reversed shear plasmas

International Nuclear Information System (INIS)

Fujita, T.; Kamada, Y.; Ide, S.; Takeji, S.; Sakamoto, Y.; Isayama, A.; Suzuki, T.; Oikawa, T.; Fukuda, T.

2001-01-01

confinement is achieved owing to strong internal transport barriers (ITBs), are reported. In a high current plasma with an L-mode edge, deuterium-tritium-equivalent fusion power gain, Q DT eq =0.5 was sustained for 0.8 s (∼ energy confinement time) by adjusting plasma beta precisely using feedback control of stored energy. In a high triangularity plasma with an ELMy H-mode edge, the shrinkage of reversed shear region was suppressed and quasi steady sustainment of high confinement was achieved by raising the poloidal beta and enhancing the bootstrap current peaked at the ITB layer. High bootstrap current fraction (∼80%) was obtained in a high q regime (q 95 ∼9), which leaded to full non-inductive current drive condition. The normalized beta (β N ) of ∼ 2 and H-factor of H 89 ∼3.5 (HH 98y2 ∼2.2) were sustained for 2.7 s (∼ 6 times energy confinement time). (author)

Application of quasi-elastic neutron scattering to dynamics study of confined water

International Nuclear Information System (INIS)

Li Hua; Zhang Lili; Yi Zhou

2014-01-01

Background: Quasi-elastic neutron scattering (QENS) is an important experiment for dynamics study of confined water. It is significant to study the dynamics of confined water in cement paste. Purpose: In this paper, we have two aims. One is to present a reviewer of QENS study on dynamics of confined water in cement paste in recent years. The other is to illustrate the QENS application to the study on dynamics of confined water based on cement paste. Method: Relaxing cage model (RCM) is specially introduced for the analyses of QENS spectra. Results: Based on RCM, several parameters for describing the dynamics of confined water in cement paste, can be obtained from the analyses of QENS spectra: a fraction of mobile 'glassy' water molecules embedded in amorphous gel region surrounding the hydration products, 1-p, the capture time of confined water molecule in some place-τ 0 , the average translational relaxation time-<τ>, the self-diffusion coefficient-D, and a phenomenological shape parameter describing the uniform of amorphous in cement paste-β. Conclusion: All these provide a practical method for QENS study on dynamics of confined water in cement paste. (authors)

Studies into laser ignition of confined pyrotechnics

Energy Technology Data Exchange (ETDEWEB)

Ahmad, S.R.; Russell, D.A. [Centre for Applied Laser Spectroscopy, DASSR, Defence Academy, Cranfield University, Shrivenham, Swindon (United Kingdom)

2008-10-15

Ignition tests were carried out on three different pyrotechnics using laser energy from the multimode output from an Ar-Ion laser (av) at 500 nm and a near-IR diode laser pigtailed to a fibre optic cable and operating at 808 nm. The pyrotechnics investigated were: G20 black powder, SR44 and SR371C. The confined ignition tests were conducted in a specially designed ignition chamber. Pyrotechnics were ignited by a free space beam entering the chamber through an industrial sapphire window in the case of the Ar-ion laser. For the NIR diode laser, fibre was ducted through a block into direct contact with the pyrotechnic. The Ar-Ion laser was chosen as this was found to ignite all three pyrotechnics in the unconfined condition. It also allowed for a direct comparison of confined/unconfined results to be made. The threshold laser flux densities to initiate reproducible ignitions at this wavelength were found to be between {proportional_to}12.7 and {proportional_to}0.16 kW cm{sup -2}. Plotted on the ignition maps are the laser flux densities versus the start of ignition times for the three confined pyrotechnics. It was found from these maps that the times for confined ignition were substantially lower than those obtained for unconfined ignition under similar experimental conditions. For the NIR diode laser flux densities varied between {proportional_to}6.8 and {proportional_to}0.2 kW cm{sup -2}. The minimum ignition times for the NIR diode laser for SR371C ({proportional_to}11.2 ms) and G20 ({proportional_to}17.1 ms) were faster than those achieved by the use of the Ar-ion laser. However, the minimum ignition time was shorter ({proportional_to}11.7 ms) with the Ar-ion laser for SR44. (Abstract Copyright [2008], Wiley Periodicals, Inc.)

Interaction between confined phonons and photons in periodic silicon resonators

Science.gov (United States)

Iskandar, A.; Gwiazda, A.; Younes, J.; Kazan, M.; Bruyant, A.; Tabbal, M.; Lerondel, G.

2018-03-01

In this paper, we demonstrate that phonons and photons of different momenta can be confined and interact with each other within the same nanostructure. The interaction between confined phonons and confined photons in silicon resonator arrays is observed by means of Raman scattering. The Raman spectra from large arrays of dielectric silicon resonators exhibited Raman enhancement accompanied with a downshift and broadening. The analysis of the Raman intensity and line shape using finite-difference time-domain simulations and a spatial correlation model demonstrated an interaction between photons confined in the resonators and phonons confined in highly defective regions prompted by the structuring process. It was shown that the Raman enhancement is due to collective lattice resonance inducing field confinement in the resonators, while the spectra downshift and broadening are signatures of the relaxation of the phonon wave vector due to phonon confinement in defective regions located in the surface layer of the Si resonators. We found that as the resonators increase in height and their shape becomes cylindrical, the amplitude of their coherent oscillation increases and hence their ability to confine the incoming electric field increases.

Ergodicity breaking, ageing, and confinement in generalized diffusion processes with position and time dependent diffusivity

International Nuclear Information System (INIS)

Cherstvy, Andrey G; Metzler, Ralf

2015-01-01

We study generalized anomalous diffusion processes whose diffusion coefficient D(x, t) ∼ D 0 |x| α t β depends on both the position x of the test particle and the process time t. This process thus combines the features of scaled Brownian motion and heterogeneous diffusion parent processes. We compute the ensemble and time averaged mean squared displacements of this generalized diffusion process. The scaling exponent of the ensemble averaged mean squared displacement is shown to be the product of the critical exponents of the parent processes, and describes both subdiffusive and superdiffusive systems. We quantify the amplitude fluctuations of the time averaged mean squared displacement as function of the length of the time series and the lag time. In particular, we observe a weak ergodicity breaking of this generalized diffusion process: even in the long time limit the ensemble and time averaged mean squared displacements are strictly disparate. When we start to observe this process some time after its initiation we observe distinct features of ageing. We derive a universal ageing factor for the time averaged mean squared displacement containing all information on the ageing time and the measurement time. External confinement is shown to alter the magnitudes and statistics of the ensemble and time averaged mean squared displacements. (paper)

Confinement of Reinforced-Concrete Columns with Non-Code Compliant Confining Reinforcement plus Supplemental Pen-Binder

Directory of Open Access Journals (Sweden)

Anang Kristianto

2012-11-01

Full Text Available One of the important requirements for earthquake resistant building related to confinement is the use of seismic hooks in the hoop or confining reinforcement of reinforced-concrete column elements. However, installation of a confining reinforcement with a 135-degree hook is not easy. Therefore, in practice, many construction workers apply a confining reinforcement with a 90-degreehook (non-code compliant. Based on research and records of recent earthquakes in Indonesia, the use of a non-code compliant confining reinforcement for concrete columns produces structures with poor seismic performance. This paper presents a study that introduces an additional element that is expected to improve the effectiveness of concrete columns confined with a non-code compliant confining reinforcement. The additional element, named a pen-binder, is used to keep the non-code compliant confining reinforcement in place. The effectiveness of this element under pure axial concentric loading was investigatedcomprehensively.The specimens tested in this study were 18 concrete columns,with a cross-section of 170 mm x 170 mm and a height of 480 mm. The main test variables were the material type of the pen-binder, the angle of the hook, and the confining reinforcement configuration.The test results indicate that adding pen-binders can effectively improve the strength and ductility of the column specimens confined with a non-code compliant confining reinforcement

Plasma confinement

CERN Document Server

Hazeltine, R D

2003-01-01

Detailed and authoritative, this volume examines the essential physics underlying international research in magnetic confinement fusion. It offers readable, thorough accounts of the fundamental concepts behind methods of confining plasma at or near thermonuclear conditions. Designed for a one- or two-semester graduate-level course in plasma physics, it also represents a valuable reference for professional physicists in controlled fusion and related disciplines.

Quark confinement

International Nuclear Information System (INIS)

Joos, H.

1976-07-01

The main topics of these lectures are: phenomenological approach to quark confinement, standard Lagrangian of hadrondynamics, Lagrangian field theory and quark confinement, classical soliton solutions in a simple model, quantization of extended systems, colour charge screening and quantization on a lattice and remarks on applications. A survey of the scientific publications listed according to the topics until 26 March 1976 is supplemented. (BJ) [de

Two-dimensionally confined topological edge states in photonic crystals

International Nuclear Information System (INIS)

Barik, Sabyasachi; Miyake, Hirokazu; DeGottardi, Wade; Waks, Edo; Hafezi, Mohammad

2016-01-01

We present an all-dielectric photonic crystal structure that supports two-dimensionally confined helical topological edge states. The topological properties of the system are controlled by the crystal parameters. An interface between two regions of differing band topologies gives rise to topological edge states confined in a dielectric slab that propagate around sharp corners without backscattering. Three-dimensional finite-difference time-domain calculations show these edges to be confined in the out-of-plane direction by total internal reflection. Such nanoscale photonic crystal architectures could enable strong interactions between photonic edge states and quantum emitters. (paper)

Enhancement of confinement in tokamaks

International Nuclear Information System (INIS)

Furth, H.P.

1986-05-01

A plausible interpretation of the experimental evidence is that energy confinement in tokamaks is governed by two separate considerations: (1) the need for resistive MHD kink-stability, which limits the permissible range of current profiles - and therefore normally also the range of temperature profiles; and (2) the presence of strongly anomalous microscopic energy transport near the plasma edge, which calibrates the amplitude of the global temperature profile, thus determining the energy confinement time tau/sub E/. Correspondingly, there are two main paths towards the enhancement of tokamak confinement: (1) Configurational optimization, to increase the MHD-stable energy content of the plasma core, can evidently be pursued by varying the cross-sectional shape of the plasma and/or finding stable radial profiles with central q-values substantially below unity - but crossing from ''first'' to ''second'' stability within the peak-pressure region would have the greatest ultimate potential. (2) Suppression of edge turbulence, so as to improve the heat insulation in the outer plasma shell, can be pursued by various local stabilizing techniques, such as use of a poloidal divertor. The present confinement model and initial TFTR pellet-injection results suggest that the introduction of a super-high-density region within the plasma core should be particularly valuable for enhancing ntau/subE/. In D-T operation, a centrally peaked plasma pressure profile could possibly lend itself to alpha-particle-driven entry into the second-stability regime

Multiple-mirror plasma confinement

International Nuclear Information System (INIS)

Lichtenberg, A.J.; Lieberman, M.A.; Logan, B.G.

1975-01-01

A large enhancement of the confinement time can be achieved in a straight system of multiple mirrors over an equal length uniform magnetic field. The scaling is diffusive rather than that of flow, thereby scaling the square of the system length rather than linear with system length. Probably the most economic mode of operation for a reactor occurs when lambda/M is approximately l/sub c/, where lambda is the mean free path, M the mirror ratio, and l/sub c/ the length between mirrors; but where the scale length of the mirror field l/sub m/ is much less than lambda. The axial confinement time has been calculated theoretically and numerically for all important parameter regimes, and confirmed experimentally. A typical reactor calculation gives Q/sub E/ = 2 for a 400 meter system with 3000 MW(e) output. The main concern of a multiple-mirror system is stability. Linked quadrupoles can achieve average minimum-B stabilization of flute modes, and experiments have demonstrated this stabilization. Localized instabilities at finite β and enhanced diffusion resulting from the distorted flux surfaces and possibly from turbulent higher order modes still remain to be investigated

Chernobyl new safe confinement

International Nuclear Information System (INIS)

Dodd, L.

2011-01-01

The author presents the new safe confinement that will be commissioned at Unit 4 of the Chernobyl NPP in 2015. The confinement will ensure that Chernobyl Unit 4 will be placed in an environmentally safe condition for at least next 100 years. The article highlights the current work status, future perspectives and the feasibility of confinement concept [ru

Wet scrubber technology for tritium confinement at ITER

Energy Technology Data Exchange (ETDEWEB)

Perevezentsev, A.N., E-mail: alexander.perevezentsev@iter.org [ITER Organization, CS 90 046, 13067 St Paul lez Durance Cedex (France); Andreev, B.M.; Rozenkevich, M.B.; Pak, Yu.S.; Ovcharov, A.V.; Marunich, S.A. [Mendeleev University of Chemical Technology, 125047 Miusskaya Sq. 9, Moscow (Russian Federation)

2010-12-15

Operation of the ITER machine with tritium plasma requires tritium confinement systems to protect workers and the environment. Tritium confinement at ITER is based on multistage approach. The final stage provides tritium confinement in building sectors and consists of building's walls as physical barriers and control of sub-atmospheric pressure in those volumes as a dynamic barrier. The dynamic part of the confinement function shall be provided by safety important components that are available all the time when required. Detritiation of air prior to its release to the environment is based on catalytic conversion of tritium containing gaseous species to water vapour followed by their isotopic exchange with liquid water in scrubber column of packed bed type. Wet scrubber technology has been selected because of its advantages over conventional air detritiation technique based on gas drying by water adsorption. The most important design target of system availability was very difficult to meet with conventional water adsorption driers. This paper presents results of experimental trial for validation of wet scrubber technology application in the ITER tritium confinement system and process evaluation using developed simulation computer code.

Confined aquifer vulnerability induced by a pumping well in a leakage area

Directory of Open Access Journals (Sweden)

X. Meng

2015-05-01

Full Text Available Due to the pollution of shallow groundwater and the rapid development of society and economy which consume more freshwater, the exploitation of confined groundwater is steadily increasing in north China. Therefore, the rapid decline of the confined groundwater head increases the risk of confined aquifer pollution by leaky recharge from shallow aquifers. In this paper, a quantitative method for assessing confined aquifer vulnerability to contamination due to pumping has been developed. This method is based on the shallow and confined groundwater flow model and the advection and dispersion in the aquitard, including sorption. The cumulative time for the pollutant concentration at the top boundary of confined aquifer exceeding the maximum allowable level is defined as the confined aquifer vulnerability index, which can be obtained by numerically solving the solute transport equation. A hypothetical example is chosen as a case study to illustrate the whole process. The results indicate that the proposed method is a practical and reasonable assessment method of confined aquifer vulnerability.

Energy confinement in the torsatron URAGAN-3M during the rf-heating mode

International Nuclear Information System (INIS)

Pashnev, V.K.; Burchenko, P.Ya.; Lozin, A.V. and others

2008-01-01

Energy confinement time of plasma in torsatron U-3M was measured both during quasi-stationary study of RF-discharge and after RF-power cut-off. Power absorbed by plasma in the confinement region was estimated. A mechanism which explain the plasma density behavior in the confinement region is proposed

Confinement and related transport in Extrap geometry

International Nuclear Information System (INIS)

Tendler, M.

1983-01-01

The properties of the plasma dynamic equilibrium are investigated for the Extrap magnetic confinement geometry. The temperatures achieved so far in the high-#betta# pinches are much lower than the predicted values. Here, it is shown that the particle containment in Extrap may be improved as compared to the other pinches due to the electrostatic confinement. An analytic solution for the profiles of the plasma parameters are found under the assumption that the energy is lost primarily in the radial direction by heat conduction and convection. An estimate of the radial particle confinement time is given, showing favourable scaling with plasma density and temperature. The conventional assumption of a uniform current density is shown to be unjustified in the case of an inhomogeneous electron temperature. An analytical expression is found for the pinch radius at different mechanisms of the heat transport. (orig.)

Electron Energy Confinement for HHFW Heating and Current Drive Phasing on NSTX

International Nuclear Information System (INIS)

Hosea, J.C.; Bernabei, S.; Biewer, T.; LeBlanc, B.; Phillips, C.K.; Wilson, J.R.; Stutman, D.; Ryan, P.; Swain, D.W.

2005-01-01

Thomson scattering laser pulses are synchronized relative to modulated HHFW power to permit evaluation of the electron energy confinement time during and following HHFW pulses for both heating and current drive antenna phasing. Profile changes resulting from instabilities require that the total electron stored energy, evaluated by integrating the midplane electron pressure P(sub)e(R) over the magnetic surfaces prescribed by EFIT analysis, be used to derive the electron energy confinement time. Core confinement is reduced during a sawtooth instability but, although the electron energy is distributed outward by the sawtooth, the bulk electron energy confinement time is essentially unaffected. The radial deposition of energy into the electrons is noticeably more peaked for current drive phasing (longer wavelength excitation) relative to that for heating phasing (shorter wavelength excitation) as is expected theoretically. However, the power delivered to the core plasma is reduced consider ably for the current drive phasing, indicating that surface/peripheral damping processes play a more important role for this case

Singularity confinement for maps with the Laurent property

International Nuclear Information System (INIS)

Hone, A.N.W.

2007-01-01

The singularity confinement test is very useful for isolating integrable cases of discrete-time dynamical systems, but it does not provide a sufficient criterion for integrability. Quite recently a new property of the bilinear equations appearing in discrete soliton theory has been noticed: The iterates of such equations are Laurent polynomials in the initial data. A large class of non-integrable mappings of the plane are presented which both possess this Laurent property and have confined singularities

Dynamics in geometrical confinement

CERN Document Server

Kremer, Friedrich

2014-01-01

This book describes the dynamics of low molecular weight and polymeric molecules when they are constrained under conditions of geometrical confinement. It covers geometrical confinement in different dimensionalities: (i) in nanometer thin layers or self supporting films (1-dimensional confinement) (ii) in pores or tubes with nanometric diameters (2-dimensional confinement) (iii) as micelles embedded in matrices (3-dimensional) or as nanodroplets.The dynamics under such conditions have been a much discussed and central topic in the focus of intense worldwide research activities within the last two decades. The present book discusses how the resulting molecular mobility is influenced by the subtle counterbalance between surface effects (typically slowing down molecular dynamics through attractive guest/host interactions) and confinement effects (typically increasing the mobility). It also explains how these influences can be modified and tuned, e.g. through appropriate surface coatings, film thicknesses or pore...

Tokamak confinement scaling laws

International Nuclear Information System (INIS)

Connor, J.

1998-01-01

The scaling of energy confinement with engineering parameters, such as plasma current and major radius, is important for establishing the size of an ignited fusion device. Tokamaks exhibit a variety of modes of operation with different confinement properties. At present there is no adequate first principles theory to predict tokamak energy confinement and the empirical scaling method is the preferred approach to designing next step tokamaks. This paper reviews a number of robust theoretical concepts, such as dimensional analysis and stability boundaries, which provide a framework for characterising and understanding tokamak confinement and, therefore, generate more confidence in using empirical laws for extrapolation to future devices. (author)

The confinement problem

International Nuclear Information System (INIS)

Seiler, E.

1985-01-01

Confinement of quarks is sometimes taken as some kind of dogma in the contemporary theory of strong interactions - quantum chromo-dynamics (QCD). Scientists should not be content with that. What is meant by ''permanent confinement'' should be formulated more precisely to see whether the theory has this property or not. The author looks at some possible interpretations of ''confinement'' and their shortcomings and then turns to the most widely used rather pragmatic definition based on the somewhat unphysical notion of infinitely heavy external sources. He describes what is known about the problem and tries to bring into focus some aspects that are insufficiently understood in his opinion

Comparison of particle confinement in the high confinement mode plasmas with the edge localized mode of the Japan Atomic Energy Research Institute Tokamak-60 Upgrade and the DIII-D tokamak

International Nuclear Information System (INIS)

Takenaga, H.; Mahdavi, M.A.; Baker, D.R.

2001-01-01

Particle confinement was compared for the high confinement mode plasmas with the edge localized mode in the Japan Atomic Energy Research Institute Tokamak-60 Upgrade (JT-60U) [S. Ishida, JT-60 Team, Nucl. Fusion 39, 1211 (1999)] and the DIII-D tokamak [J. L. Luxon et al., Plasma Physics and Controlled Nuclear Fusion Research 1986 (International Atomic Energy Agency, Vienna, 1987), Vol. 1, p. 159] considering separate confinement times for particles supplied by neutral beam injection (NBI) (center fueling) and by recycling and gas-puffing (edge fueling). Similar dependence on the NBI power was obtained in JT-60U and DIII-D. The particle confinement time for center fueling in DIII-D was smaller by a factor of 4 in the low density discharges and by a factor of 1.8 in the high density discharges than JT-60U scaling, respectively, suggesting the stronger dependence on the density in DIII-D. The particle confinement time for edge fueling in DIII-D was comparable with JT-60U scaling in the low density discharges. However, it decreased to a much smaller value in the high density discharges

Status of global energy confinement studies

International Nuclear Information System (INIS)

Kaye, S.M.; Bell, M.G.; DeBoo, J.C.; Waltz, R.; Greenwald, M.; Sigmar, D.

1990-02-01

Empirical scaling expressions, reflecting the parametric dependence of the L-mode energy confinement time, have been used not only as benchmarks for tokamak operation and theories of energy transport, but for predicting the performance of proposed tokamak devices. Several scaling expressions based on data from small-and medium-sized devices have done well in predicting performance in larger devices, although great uncertainty exists in extrapolating yet farther, into the ignition regime. Several approaches exist for developing higher confidence scaling expressions. These include reducing the statistical uncertainty by identifying and filling in gaps in the present database, making use of more sophisticated statistical techniques, and developing scalings for confinement regimes within which future devices will operate. Confidence in the scaling expressions will be increased still if the expressions can be more directly tied to transport physics theory. This can be done through the use of dimensionless parameters, better describing the edge and core confinement regimes separately, and by incorporating transport models directly into the scaling expressions. 50 refs., 5 figs., 3 tabs

High efficiency confinement mode by electron cyclotron heating

International Nuclear Information System (INIS)

Funahashi, Akimasa

1987-01-01

In the medium size nuclear fusion experiment facility JFT-2M in the Japan Atomic Energy Research Institute, the research on the high efficiency plasma confinement mode has been advanced, and in the experiment in June, 1987, the formation of a high efficiency confinement mode was successfully controlled by electron cyclotron heating, for the first time in the world. This result further advanced the control of the formation of a high efficiency plasma confinement mode and the elucidation of the physical mechanism of that mode, and promoted the research and development of the plasma heating by electron cyclotron heating. In this paper, the recent results of the research on a high efficiency confinement mode at the JFT-2M are reported, and the role of the JFT-2M and the experiment on the improvement of core plasma performance are outlined. Now the plasma temperature exceeding 100 million deg C has been attained in large tokamaks, and in medium size facilities, the various measures for improving confinement performance are to be brought forth and their scientific basis is elucidated to assist large facilities. The JFT-2M started the operation in April, 1983, and has accumulated the results smoothly since then. (Kako, I.)

Effects of electrode polarization and particle deposition profile on TJ-I plasma confinement

International Nuclear Information System (INIS)

Zurro, B.; Tabares, F.; Pardo, C.; Tafalla, D.; Cal, E. de la; Garcia-Castaner, B.; Pedrosa, M.A.; Sanchez, J.; Rodriguez-Yunta, A.

1991-01-01

The role of self-created radial electric field on particle confinement in TJ-I plasmas was addressed using plasma rotation data in conjunction with particle confinement times measured by laser ablation. In this paper following the pioneer work of Taylor, we have started to study the influence of a polarized electrode inserted into the plasma on particle confinement and plasma rotation in this ohmically heated tokamak. To have a supportive frame of reference, the confinement time of background particles and their transport into plasma without electrode, has been studied by measuring with space-time resolution the H α emission on varying plasma conditions. These experiments have been carried out in ohmically heated discharges of the TJ-I tokamak (R 0 =30 cm, a=10 cm) which was operated with plasma currents between 20 and 45 kA and a toroidal field ranging from 0.8 to 1.5 T. In this paper, firstly the experimental plasma and specific diagnostics are described, secondly, the parametric dependence of the particle confinement time and radial transport of background plasma is presented and finally, the influence of polarizing an inserted electrode on a particular discharge is given and discussed in the context of other polarization experiments. (author) 7 refs., 4 figs

Thermal barrier confinement experiments in TMX-U tandem mirror. Revision 1

International Nuclear Information System (INIS)

Simonen, T.C.; Allen, S.L.; Baldwin, D.E.

1984-01-01

In our recent experiments on the TMX-U thermal-barrier device, we achieved the end plugging of axial ion losses up to a central cell density of n/sub c/ = 6 x 10 12 cm -3 . During lower density experiments, we measured the axial potential profile characteristic of a thermal barrier and found an ion-confining potential greater than 1.5 kV and a potential depression of 0.45 kV in the barrier region. The average beta of hot end plug electrons has reached 15% and of hot central cell ions has reached 6%. In addition, we heated deuterium ions in the central cell with ICRF to an average perpendicular energy of 2 keV. During strong end plugging at low density (7 x 10 11 cm -3 ), the axial ion confinement time tau/sub parallel to/ reached 50 to 100 ms while the nonambiopolar radial ion confinement time tau/sub perpendicular to/ was 14 ms - independent of end plugging. Electrically floating end walls doubled the radial ion confinement time. At higher densities and lower potentials, tau/sub parallel to/ was 6 to 12 ms and tau/sub perpendicular to/ exceeded 100 ms

A Tragedy of Democracy: Japanese Confinement in North America

Directory of Open Access Journals (Sweden)

Greg Robinson

2010-03-01

Full Text Available

The confinement of some 120,000 Japanese Americans during World War II, often called the Japanese American internment, has been described as the worst official civil rights violation of modern U. S. history. Greg Robinson not only offers a bold new understanding of these events but also studies them within a larger time frame and from a transnational perspective. Drawing on newly discovered material, Robinson provides a backstory of confinement that reveals for the first time the extent of the American government's surveillance of Japanese communities in the years leading up to war and the construction of what officials termed "concentration camps" for enemy aliens. He also considers the aftermath of confinement, including the place of Japanese Americans in postwar civil rights struggles, the long movement by former camp inmates for redress, and the continuing role of the camps as touchstones for nationwide commemoration and debate. Most remarkably, A Tragedy of Democracy is the first book to analyze official policy toward West Coast Japanese Americans within a North American context. Robinson studies confinement on the mainland alongside events in wartime Hawaii, where fears of Japanese Americans justified Army dictatorship, suspension of the Constitution, and the imposition of military tribunals. He similarly reads the treatment of Japanese Americans against Canada's confinement of 22,000 citizens and residents of Japanese ancestry from British Columbia. A Tragedy of Democracy recounts the expulsion of almost 5,000 Japanese from Mexico's Pacific Coast and the poignant story of the Japanese Latin Americans who were kidnapped from their homes and interned in the United States. Approaching Japanese confinement as a continental and international phenomenon, Robinson offers a truly kaleidoscopic understanding of its genesis and outcomes.

A Tragedy of Democracy: Japanese Confinement in North America

Directory of Open Access Journals (Sweden)

Greg Robinson

2010-03-01

Full Text Available The confinement of some 120,000 Japanese Americans during World War II, often called the Japanese American internment, has been described as the worst official civil rights violation of modern U. S. history. Greg Robinson not only offers a bold new understanding of these events but also studies them within a larger time frame and from a transnational perspective. Drawing on newly discovered material, Robinson provides a backstory of confinement that reveals for the first time the extent of the American government's surveillance of Japanese communities in the years leading up to war and the construction of what officials termed "concentration camps" for enemy aliens. He also considers the aftermath of confinement, including the place of Japanese Americans in postwar civil rights struggles, the long movement by former camp inmates for redress, and the continuing role of the camps as touchstones for nationwide commemoration and debate. Most remarkably, A Tragedy of Democracy is the first book to analyze official policy toward West Coast Japanese Americans within a North American context. Robinson studies confinement on the mainland alongside events in wartime Hawaii, where fears of Japanese Americans justified Army dictatorship, suspension of the Constitution, and the imposition of military tribunals. He similarly reads the treatment of Japanese Americans against Canada's confinement of 22,000 citizens and residents of Japanese ancestry from British Columbia. A Tragedy of Democracy recounts the expulsion of almost 5,000 Japanese from Mexico's Pacific Coast and the poignant story of the Japanese Latin Americans who were kidnapped from their homes and interned in the United States. Approaching Japanese confinement as a continental and international phenomenon, Robinson offers a truly kaleidoscopic understanding of its genesis and outcomes.

Pattern replication by confined dewetting

NARCIS (Netherlands)

Harkema, S.; Schäffer, E.; Morariu, M.D.; Steiner, U

2003-01-01

The dewetting of a polymer film in a confined geometry was employed in a pattern-replication process. The instability of dewetting films is pinned by a structured confining surface, thereby replicating its topographic pattern. Depending on the surface energy of the confining surface, two different

Stochastic calculus of protein filament formation under spatial confinement

Science.gov (United States)

Michaels, Thomas C. T.; Dear, Alexander J.; Knowles, Tuomas P. J.

2018-05-01

The growth of filamentous aggregates from precursor proteins is a process of central importance to both normal and aberrant biology, for instance as the driver of devastating human disorders such as Alzheimer's and Parkinson's diseases. The conventional theoretical framework for describing this class of phenomena in bulk is based upon the mean-field limit of the law of mass action, which implicitly assumes deterministic dynamics. However, protein filament formation processes under spatial confinement, such as in microdroplets or in the cellular environment, show intrinsic variability due to the molecular noise associated with small-volume effects. To account for this effect, in this paper we introduce a stochastic differential equation approach for investigating protein filament formation processes under spatial confinement. Using this framework, we study the statistical properties of stochastic aggregation curves, as well as the distribution of reaction lag-times. Moreover, we establish the gradual breakdown of the correlation between lag-time and normalized growth rate under spatial confinement. Our results establish the key role of spatial confinement in determining the onset of stochasticity in protein filament formation and offer a formalism for studying protein aggregation kinetics in small volumes in terms of the kinetic parameters describing the aggregation dynamics in bulk.

Improved confinement in L-mode JET plasmas

International Nuclear Information System (INIS)

Jones, T.T.C.; Balet, B.; Bhatnagar, V.; Bures, M.; Campbell, D.J.; Christiansen, J.P.; Cordey, J.G.; Core, W.F.; Corti, S.; Costley, A.E.; Cottrell, G.A.; Edwards, A.; Ehrenberg, J.; Jacquinot, J.; Lallia, P.; Lomas, P.J.; Lowry, C.; Malacarne, M.; Muir, D.G.; Nave, M.F.; Nielsen, P.; Sack, C.; Sadler, G.; Start, D.F.H.; Taroni, A.; Thomas, P.R.; Thomsen, K.

1989-01-01

The JET confinement data show considerable variations of stored plasma energy W (thermal + fast ions) at fixed input power P, plasma current I, toroidal field B and plasma configuration C. The data on confinement properties, e.g. the confinement time τ E or its incremental value τ E (inc), derived from variations of P at fixed I, B, C thus exhibit scatter which makes the scaling of τ E with P, I, B, C difficult to establish. The effects from sawteeth, from variations in the power deposition profiles and from plasma edge physics on confinement do not depend on P, I, B, C in any simple way which would permit a deduced scaling law to be identified with a single (or more) physics loss mechanism(s). In this paper we examine the response of confinement to variations in plasma configuration at fixed I and B (3 MA and 3 T). Results from global and local transport analysis are discussed in sections 2 and 3; section 4 describes the role of fast ions produced by ICRF and NBI heating. High confinement in the L-mode regime at increased plasma currents up to 6 MA is also studied, in particular the effects from sawteeth on stored energy W. Such effects increase with current and presently only predictive transport studies (section 5) can estimate what may be achieved at high current without sawteeth effects. The predictive studies also assess the benefits which may arise from an increase of the neutral beam energy at high plasma currents (section 6). The conclusions are based on extensive study of data from JET pulses with up to 14 MW of ICRH, 21 MW of NBI and 6 MW of ohmic power. None of the pulses included in the study show the sudden reduction of D α emission characteristic of the L to H mode transition of confinement. 7 refs., 4 figs

Confinement in TPE-RX reversed field pinch

International Nuclear Information System (INIS)

Yagi, Y.; Bolzonella, T.; Canton, A.

2001-01-01

Characteristics of the confinement properties of a reversed field pinch (RFP), the TPE-RX (R/a=1.72/0.45 m, R and a are major and minor radii), are presented for the plasma current, I p of 0.2-0.4 MA. TPE-RX has been operational since 1998, and I p =0.5 MA and duration time of up to 0.1 s have been obtained separately. It is found that I p /N (=12x10 -14 Am, N is the line density) is higher than those of other RFPs and poloidal beta, β p , and energy confinement time, τ E , are 5-10% and 0.5-1 ms, respectively, which are comparable with those of other RFPs of comparable sizes (RFX and MST). Pulsed poloidal current drive has recently been tested and the result has shown a twofold improvement of β p and τ E . The improvement is discussed in terms of the dynamic trajectories in the F-Θ plane, where F and Θ are reversal and pinch parameters, respectively. The global confinement properties are compared between the locked and non-locked discharges, which yields a better understanding of the mode-locking phenomena in RFP plasmas. (author)

Confinement studies of neutral beam heated discharges in TFTR

Energy Technology Data Exchange (ETDEWEB)

Murakami, M.; Arunasalam, V.; Bell, J.D.; Stauffer, F.; Bell, M.G.; Bitte, M.; Blanchard, W.R.; Boody, F.; Britz, N.

1985-11-01

The TFTR tokamak has reached its original machine design specifications (I/sub p/ = 2.5 MA and B/sub T/ = 5.2T). Recently, the D/sup 0/ neutral beam heating power has been increased to 6.3 MW. By operating at low plasma current (I/sub p/ approx. = 0.8 MA) and low density anti n/sub e/ approx. = 1 x 10/sup 19/m/sup -3/), high ion temperatures (9 +- keV) and rotation speeds (7 x 10/sup 5/ m/s) have been achieved during injection. At the opposite extreme, pellet injection into high current plasmas has been used to increase the line-average density to 8 x 10/sup 19/m/sup -3/ and the central density to 1.6 x 10/sup 20/m/sup -3// This wide range of operating conditions has enabled us to conduct scaling studies of the global energy confinement time in both ohmically and beam heated discharges as well as more detailed transport studies of the profile dependence. In ohmic discharges, the energy confinement time is observed to scale linearly with density only up to anti n/sub e/ approx. 4.5 x 10/sup 19/m/sup -3/ and then to increase more gradually, achieving a maximum value of approx. 0.45 s. In beam heated discharges, the energy confinement time is observed to decrease with beam power and to increase with plasma current. With P/sub b/ = 5.6 MW, anti n/sub e/ = 4.7 x 10/sup 19/m/sup -3/, I/sub p/ = 2.2 MA and B/sub T = 4.7T, the gross energy confinement time is 0.22 s and T/sub i/(0) = 4.8 keV. Despite shallow penetration of D/sup 0/ beams (at the beam energy less than or equal to 80 keV with low species yield), tau/sub E/(a) values are as large as those for H/sup 0/ injection, but central confinement times are substantially greater. This is a consequence of the insensitivity of the temperature and safety factor profile shapes to the heating profile. The radial variation of tau/sub E/ is even more pronounced with D/sup 0/ injection into high density pellet-injected plasmas. 25 refs.

The ''Kinetic Stabilizer'': A Simpler Tandem Mirror Confinement?

International Nuclear Information System (INIS)

Post, R.F.

2000-01-01

In the search for better approaches to magnetic fusion it is important to keep in mind the lessons learned in the 50 years that fusion plasma confinement has been studied. One of the lessons learned is that ''closed'' and ''open'' fusion devices differ fundamentally with respect to an important property of their confinement, as follows: Without known exception closed systems such as the tokamak, the stellarator, or the reversed-field pinch, have been found to have their confinement times limited by non-classical, i.e., turbulence-related, processes, leading to the requirement that such systems must be scaled-up in dimensions to sizes much larger than would be the case in the absence of turbulence. By contrast, from the earliest days of fusion research, it has been demonstrated that open magnetic systems of the mirror variety can achieve confinement times close to that associated with classical, i.e., collisional, processes. While these good results have been obtained in both axially symmetric fields and in non-axisymmetric fields, the clearest cases have been those in which the confining fields are solenoidal and axially symmetric. These observations, i.e., of confinement not enhanced by turbulence, can be traced theoretically to such factors as the absence of parallel currents in the plasma, and to the constraints on particle drifts imposed by the adiabatic invariants governing particle confinement in axisymmetric open systems. In the past the MHD instability of axially symmetric open systems has been seen as a barrier to their use. However, theory predicts MHD-stable confinement is achievable if sufficient plasma is present in the ''good curvature'' regions outside the mirrors. This theory has been confirmed by experiments on the Gas Dynamic Trap mirror-based experiment at Novosibirsk, In this paper a new way of exploiting this stabilizing principle, involving creating a localized ''stabilizer plasma'' outside a mirror, will be discussed. To create this plasma

A diamond detector for inertial confinement fusion X-ray bang-time measurements at the National Ignition Facility

Energy Technology Data Exchange (ETDEWEB)

MacPhee, A G; Brown, C; Burns, S; Celeste, J; Glenzer, S H; Hey, D; Jones, O S; Landen, O; Mackinnon, A J; Meezan, N; Parker, J; Edgell, D; Glebov, V Y; Kilkenny, J; Kimbrough, J

2010-11-09

An instrument has been developed to measure X-ray bang-time for inertial confinement fusion capsules; the time interval between the start of the laser pulse and peak X-ray emission from the fuel core. The instrument comprises chemical vapor deposited polycrystalline diamond photoconductive X-ray detectors with highly ordered pyrolytic graphite X-ray monochromator crystals at the input. Capsule bang-time can be measured in the presence of relatively high thermal and hard X-ray background components due to the selective band pass of the crystals combined with direct and indirect X-ray shielding of the detector elements. A five channel system is being commissioned at the National Ignition Facility at Lawrence Livermore National Laboratory for implosion optimization measurements as part of the National Ignition Campaign. Characteristics of the instrument have been measured demonstrating that X-ray bang-time can be measured with {+-} 30ps precision, characterizing the soft X-ray drive to +/- 1eV or 1.5%.

An experiment to test centrifugal confinement for fusion

International Nuclear Information System (INIS)

Ellis, R.F.; Hassam, A.B.; Messer, S.; Osborn, B.R.

2001-01-01

The basic idea of centrifugal confinement is to use centrifugal forces from supersonic rotation to augment conventional magnetic confinement. Optimizing this 'knob' results in a fusion device that features four advantages: steady state, no disruptions, superior cross-field confinement, and a simpler coil configuration. The idea rests on two prongs: first, centrifugal forces can confine plasmas to desired regions of shaped magnetic fields; second, the accompanying large velocity shear can stabilize even magnetohydrodynamic (MHD) instabilities. A third feature is that the velocity shear also viscously heats the plasma; no auxiliary heating is necessary to reach fusion temperatures. Regarding transport, the velocity shear can also quell microturbulence, leading to fully classical confinement, as there are no neoclassical effects. Classical parallel electron transport then sets the confinement time. These losses are minimized by a large Pastukhov factor resulting from the deep centrifugal potential well: at Mach 4-5, the Lawson criterion is accessible. One key issue is whether velocity shear will be sufficient by itself to stabilize MHD interchanges. Numerical simulations indicate that laminar equilibria can be obtained at Mach numbers of 4-5 but that the progression toward laminarity with increasing Mach number is accompanied by residual convection from the interchanges. The central goal of the Maryland Centrifugal Torus (MCT) [R. F. Ellis et al., Bull. Am. Phys. Soc. 44, 48 (1998)] is to obtain MHD stability from velocity shear. As an assist to accessing laminarity, MCT will incorporate two unique features: plasma elongation and toroidal magnetic field. The former raises velocity shear efficiency, and modest magnetic shear should suppress residual convection

Microviscosity of supercooled water confined within aminopropyl-modified mesoporous silica as studied by time-resolved fluorescence spectroscopy.

Science.gov (United States)

Yamaguchi, Akira; Namekawa, Manato; Itoh, Tetsuji; Teramae, Norio

2012-01-01

The fluorescence dynamics of rhodamine B (RhB) immobilized on the pore surface of aminopropyl (AP)-modified mesoporous silica (diameter of the silica framework, 3.1 nm) was examined at temperatures between 293 and 193 K to study the microviscosity of supercooled water confined inside the pores. The mesoporous silica specimen with a dense AP layer (2.1 molecules nm(-2)) was prepared, and RhB isothiocyanate was covalently bound to part of the surface AP groups. The fluorescence lifetime of the surface RhB increased with decreasing temperature from 293 to 223 K, indicating that freezing of the confined water did not occur in this temperature range. The microviscosity of the supercooled confined water was evaluated from an analysis of the lifetime data based on a frequency-dependent friction model.

Investigation of energy confinement during ICRF heating on EAST

Science.gov (United States)

Yang, Y. Q.; Zhang, X. J.; Zhao, Y. P.; Qin, C. M.; Cheng, Y.; Mao, Y. Z.; Yang, H.; Yuan, S.; Wang, L.; Ju, S. Q.; Chen, G.; Zhang, J. H.; Wang, J. H.; Chen, Z.; Wan, B. N.; Gong, X. Z.; Qian, J. P.; Zhang, T.; Li, J. G.; Song, Y. T.; Lin, Y.; Taylor, G.; Hosea, J. C.; Perkins, R. J.; Wukitch, S.; Noterdaeme, J. M.; Kumazawa, R.; Seki, T.; Saito, K.; Kasahara, H.

2017-09-01

A summary is given on recent experiments in L-mode with ion cyclotron resonance heating (ICRH) of hydrogen minority in deuterium plasmas on EAST. Experiments show a degradation of confinement with increasing power. Furthermore, the energy confinement time increases with plasma current and magnetic field, whereas it is insensitive to line averaged density. Minority heating has been found to be efficient, and parameters were optimized to maximize its efficiency. ICRH in lower hybrid waves heated plasma was also investigated.

Unconfined versus confined speleogenetic settings: variations of solution porosity.

Directory of Open Access Journals (Sweden)

Klimchouk Alexander

2006-01-01

Full Text Available Speleogenesis in confined settings generates cave morphologies that differ much from those formed in unconfined settings. Cavesdeveloped in unconfined settings are characterised by broadly dendritic patterns of channels due to highly competing development.In contrast, caves originated under confined conditions tend to form two- or three-dimensional mazes with densely packed conduits.This paper illustrates variations of solution (channel porosity resulted from speleogenesis in unconfined and confined settings by theanalysis of morphometric parameters of typical cave patterns. Two samples of typical cave systems formed in the respective settingsare compared. The sample that represents unconfined speleogenesis consists of solely limestone caves, whereas gypsum cavesof this type tend to be less dendritic and more linear. The sample that represents confined speleogenesis consists of both limestoneand gypsum maze caves. The comparison shows considerable differences in average values of some parameters between thesettings. Passage network density (the ratio of the cave length to the area of the cave field, km/km2 is one order of magnitudegreater in confined settings than in unconfined (average 167.3 km/km2 versus 16.6 km/km2. Similarly, an order of magnitudedifference is observed in cave porosity (a fraction of the volume of a cave block, occupied by mapped cavities; 5.0 % versus 0.4 %.This illustrates that storage in maturely karstified confined aquifers is generally much greater than in unconfined. The average areal coverage (a fraction of the area of the cave field occupied by passages in a plan view is about 5 times greater in confined settingsthan in unconfined (29.7 % versus 6.4 %. This indicates that conduit permeability in confined aquifers is appreciably easier to targetwith drilling than the widely spaced conduits in unconfined aquifers.

Effects of a vertical magnetic field on particle confinement in a magnetized plasma torus.

Science.gov (United States)

Müller, S H; Fasoli, A; Labit, B; McGrath, M; Podestà, M; Poli, F M

2004-10-15

The particle confinement in a magnetized plasma torus with superimposed vertical magnetic field is modeled and measured experimentally. The formation of an equilibrium characterized by a parallel plasma current canceling out the grad B and curvature drifts is described using a two-fluid model. Characteristic response frequencies and relaxation rates are calculated. The predictions for the particle confinement time as a function of the vertical magnetic field are verified in a systematic experimental study on the TORPEX device, including the existence of an optimal vertical field and the anticorrelation between confinement time and density.

Photoluminescence dynamics of weakly confined excitons in GaAs thin films

International Nuclear Information System (INIS)

Kanno, Atsushi; Katouf, Redouane; Kojima, Osamu; Ishi-Hayase, Junko; Sasaki, Masahide; Tsuchiya, Masahiro; Isu, Toshiro

2008-01-01

We investigate the dynamics of weakly confined excitons in GaAs thin films measured by time-resolved photoluminescence (PL) technique. When excitation energy was above the resonant energy of the exciton, a long PL rise time of about 200 ps was observed. It is considered that an exciton formation process from excited continuum energy states to discrete energy states of the exciton in the thin film causes the slow PL rise. The observed PL decay time constant was about 14 ns due to high quality fabricated samples. The observed population dynamics can be surely ascribed to the specific features of weakly confined excitons

Applications of a general random-walk theory for confined diffusion.

Science.gov (United States)

Calvo-Muñoz, Elisa M; Selvan, Myvizhi Esai; Xiong, Ruichang; Ojha, Madhusudan; Keffer, David J; Nicholson, Donald M; Egami, Takeshi

2011-01-01

A general random walk theory for diffusion in the presence of nanoscale confinement is developed and applied. The random-walk theory contains two parameters describing confinement: a cage size and a cage-to-cage hopping probability. The theory captures the correct nonlinear dependence of the mean square displacement (MSD) on observation time for intermediate times. Because of its simplicity, the theory also requires modest computational requirements and is thus able to simulate systems with very low diffusivities for sufficiently long time to reach the infinite-time-limit regime where the Einstein relation can be used to extract the self-diffusivity. The theory is applied to three practical cases in which the degree of order in confinement varies. The three systems include diffusion of (i) polyatomic molecules in metal organic frameworks, (ii) water in proton exchange membranes, and (iii) liquid and glassy iron. For all three cases, the comparison between theory and the results of molecular dynamics (MD) simulations indicates that the theory can describe the observed diffusion behavior with a small fraction of the computational expense. The confined-random-walk theory fit to the MSDs of very short MD simulations is capable of accurately reproducing the MSDs of much longer MD simulations. Furthermore, the values of the parameter for cage size correspond to the physical dimensions of the systems and the cage-to-cage hopping probability corresponds to the activation barrier for diffusion, indicating that the two parameters in the theory are not simply fitted values but correspond to real properties of the physical system.

Role of density modulation in the spatially resolved dynamics of strongly confined liquids.

Science.gov (United States)

Saw, Shibu; Dasgupta, Chandan

2016-08-07

Confinement by walls usually produces a strong modulation in the density of dense liquids near the walls. Using molecular dynamics simulations, we examine the effects of the density modulation on the spatially resolved dynamics of a liquid confined between two parallel walls, using a resolution of a fraction of the interparticle distance in the liquid. The local dynamics is quantified by the relaxation time associated with the temporal autocorrelation function of the local density. We find that this local relaxation time varies in phase with the density modulation. The amplitude of the spatial modulation of the relaxation time can be quite large, depending on the characteristics of the wall and thermodynamic parameters of the liquid. To disentangle the effects of confinement and density modulation on the spatially resolved dynamics, we compare the dynamics of a confined liquid with that of an unconfined one in which a similar density modulation is induced by an external potential. We find several differences indicating that density modulation alone cannot account for all the features seen in the spatially resolved dynamics of confined liquids. We also examine how the dynamics near a wall depends on the separation between the two walls and show that the features seen in our simulations persist in the limit of large wall separation.

Energy confinement of high-density tokamaks

NARCIS (Netherlands)

Schüller, F.C.; Schram, D.C.; Coppi, B.; Sadowski, W.

1977-01-01

Neoclassical ion heat conduction is the major energy loss mechanism in the center of an ohmically heated high-d. tokamak discharge (n>3 * 1020 m-3). This fixes the mutual dependence of plasma quantities on the axis and leads to scaling laws for the poloidal b and energy confinement time, given the

Definition of a critical confining zone using surface geophysical methods

International Nuclear Information System (INIS)

Eddy-Dilek, C.A.; Looney, B.B.; Hoekstra, P.; Harthill, N.; Blohm, M.; Phillips, D.R.

1997-01-01

Definition of the hydrologic framework in layered sediments of fluvial and deltaic origin is a difficult challenge for environmental characterization and remediation programs due to the lithologic and stratigraphic heterogeneities inherent in these settings. The authors set out to use complementary geophysical surveys to determine the nature and extent of a deep confining unit at the Savannah River Site, South Carolina. Time Domain Electromagnetic (TDEM) soundings were used to define the electrical conductance of the clayey confining unit (aquitard), and shear-wave reflection seismic was used to define the stratigraphic framework. Based on correlations with borehole geophysical logs and sieve data, the shear-wave seismic proved capable of defining relatively fine layering in the coastal plain sediments, the upper and lower surfaces of a critical confining unit, and erosional features on the surface of the confining unit. The TDEM surveys defined the presence or absence of the clay facies of the confining unit. Moreover, by constraining the interpretation of the TDEM data with the thickness of the confining unit derived from the seismic data, the authors mapped the extent of the unit, showing where the clay is thicker, where it probably was never deposited, and where it was eroded by downcutting channels. These results have significant implications on the design and optimization of remedial systems

H-mode confinement properties close to the power threshold in ASDEX Upgrade

International Nuclear Information System (INIS)

Ryter, F; Fuchs, J; Schneider, W; Sips, A; Staebler, A; Stober, J

2008-01-01

Confinement properties close to the H-mode power threshold are studied in the ASDEX Upgrade tokamak. The results show that good confinement can be obtained close to the threshold with Type-I ELMs. The existence of Type-I ELMs does not necessarily require the heating power to be higher than the H-Mode power threshold, but it requires collisionality to be low enough. At higher collisionality Type-III ELMs replace the Type-I ELMs and confinement time is reduced by about 20%

Theoretical quantification of shock-timing sensitivities for direct-drive inertial confinement fusion implosions on OMEGA

Science.gov (United States)

Cao, D.; Boehly, T. R.; Gregor, M. C.; Polsin, D. N.; Davis, A. K.; Radha, P. B.; Regan, S. P.; Goncharov, V. N.

2018-05-01

Using temporally shaped laser pulses, multiple shocks can be launched in direct-drive inertial confinement fusion implosion experiments to set the shell on a desired isentrope or adiabat. The velocity of the first shock and the times at which subsequent shocks catch up to it are measured through the velocity interferometry system for any reflector diagnostic [T. R. Boehly et al., Phys. Plasmas 18, 092706 (2011)] on OMEGA [T. R. Boehly et al., Opt. Commun. 133, 495 (1997)]. Simulations reproduce these velocity and shock-merger time measurements when using laser pulses designed for setting mid-adiabat (α ˜ 3) implosions, but agreement degrades for lower-adiabat (α ˜ 1) designs. Simulation results indicate that the shock timing discrepancy is most sensitive to details of the density and temperature profiles in the coronal plasma, which influences the laser energy coupled into the target, and only marginally sensitive to the target offset and beam power imbalance. To aid in verifying the coronal profile's influence, a new technique under development to infer coronal profiles using x-ray self-emission imaging [A. K. Davis et al., Bull. Am. Phys. Soc. 61, BAPS.2016.DPP.NO8.7 (2016)] can be applied to the pulse shapes used in shock-timing experiments.

High-Energy Electron Confinement in a Magnetic Cusp Configuration

Directory of Open Access Journals (Sweden)

Jaeyoung Park

2015-06-01

Full Text Available We report experimental results validating the concept that plasma confinement is enhanced in a magnetic cusp configuration when β (plasma pressure/magnetic field pressure is of order unity. This enhancement is required for a fusion power reactor based on cusp confinement to be feasible. The magnetic cusp configuration possesses a critical advantage: the plasma is stable to large scale perturbations. However, early work indicated that plasma loss rates in a reactor based on a cusp configuration were too large for net power production. Grad and others theorized that at high β a sharp boundary would form between the plasma and the magnetic field, leading to substantially smaller loss rates. While not able to confirm the details of Grad’s work, the current experiment does validate, for the first time, the conjecture that confinement is substantially improved at high β. This represents critical progress toward an understanding of the plasma dynamics in a high-β cusp system. We hope that these results will stimulate a renewed interest in the cusp configuration as a fusion confinement candidate. In addition, the enhanced high-energy electron confinement resolves a key impediment to progress of the Polywell fusion concept, which combines a high-β cusp configuration with electrostatic fusion for a compact, power-producing nuclear fusion reactor.

Parametric scaling studies of energy-confinement time for neutral-beam-heated Heliotron-E plasmas

International Nuclear Information System (INIS)

Sano, F.; Takeiri, Y.; Hanatani, K.

1989-02-01

Kinetic analysis of the global energy confinement time for neutral-beam-heated Heliotron-E plasmas has been performed with the 1-D, time-independent transport analysis code, PROCTR-Mod. Beam-power scans were performed by firing various number of hydrogen neutral beams, while density scans were performed by puffing gas and/or pellet fueling under the metallic or carbonized wall conditions. The wall carbonization facilitated the density increase due to the enhanced particle recycling on the walls, and also enabled long-pulse, quasi-stationary, currentless ECH + NBI operation with reduced heavy-impurity contamination. The data analysis shows that the favorable density dependence partially offsets the unfavorable power dependence, and that the anomalous electron transport loss becomes dominant in the over-all energy balance as the beam power and plasma density are increased. An alternative scaling law is also presented which is to fit τ E G [ms] by an 'offset-linear' law. The latter scaling is found to provide a better fit to the presented data sets in spite of its simple form. The parametric scaling of the local electron thermal diffusivity, χ e , is also discussed on the basis of the kinetic analysis. (J.P.N.)

The isotope dependence of confinement in ASDEX. Pt. 2

International Nuclear Information System (INIS)

Wagner, F.; Bessenrodt-Weberpals, M.; Giannone, L.; Kallenbach, A.; McCormick, K.; Soeldner, F.X.; Stroth, U.

1990-01-01

In this paper the authors continue the report on the study of the dependence of plasma parameters on the ion mass A i . Both under ohmic and beam heating conditions a strong sensitivity of the central electron temperature, the electron and total energy content, the energy confinement time, and sawtooth repetition time are observed. The previously observed strong sensitivity of the edge density on A i is a secondary effect. The observation of an A i dependence both in lower hybrid heated discharges but also in the momentum confinement with NI demonstrates that the ion mass affects both electron and ion transport. Transport analysis indicates that the effective heat diffusivity is lower in deuterium for all radii. (orig.)

Confinement at large-N

International Nuclear Information System (INIS)

Klinkhamer, F.R.

1985-06-01

Recent numerical results indicate that QCD in the limit of an infinite number (N) of colors also has confinement and moreover that it looks rather similar to normal QCD with N = 3 colors. This imposes severe restrictions on what the mechanism of confinement can be

Stable confinement of toroidal electron plasma in an internal conductor device Prototype-Ring Trap

International Nuclear Information System (INIS)

Saitoh, H.; Yoshida, Z.; Watanabe, S.

2005-01-01

A pure electron plasma has been produced in an internal conductor device Prototype-Ring Trap (Proto-RT). The temporal evolution of the electron plasma was investigated by the measurement of electrostatic fluctuations. Stable confinement was realized when the potential profile adjusted to match the magnetic surfaces. The confinement time varies as a function of the magnetic field strength and the neutral gas pressure, and is comparable to the diffusion time of electrons determined by the classical collisions with neutral gas. Although the addition of a toroidal magnetic field stabilized the electrostatic fluctuation of the plasma, the effects of the magnetic shear shortened the stable confinement time, possibly because of the obstacles of coil support structures

Confined Tube Crimp Using Portable Hand Tools

Energy Technology Data Exchange (ETDEWEB)

Reynolds, Joseph James [Los Alamos National Laboratory; Pereyra, R. A. [LANL Retired; Archuleta, Jeffrey Christopher [Los Alamos National Laboratory; Martinez, Isaac P. [Los Alamos National Laboratory; Nelson, A. M. [MST-16 Summer Student (2007); Allen, Ronald Scott [Los Alamos National Laboratory; Page, R. L. [LANL Retired; Freer, Jerry Eugene [Los Alamos National Laboratory; Dozhier, Nathan Gus [Los Alamos National Laboratory

2016-04-04

The Lawrence Radiation Laboratory developed handheld tools that crimp a 1/16 inch OD tube, forming a leak tight seal1 (see Figure 1). The leak tight seal forms by confining the 1/16 inch OD tubing inside a die while applying crimp pressure. Under confined pressure, the tube walls weld at the crimp. The purpose of this study was to determine conditions for fabricating a leak tight tube weld. The equipment was used on a trial-and-error basis, changing the conditions after each attempt until successful welds were fabricated. To better confine the tube, the die faces were polished. Polishing removed a few thousandths of an inch from the die face, resulting in a tighter grip on the tubing wall. Using detergent in an ultrasonic bath, the tubing was cleaned. Also, the time under crimp pressure was increased to 30 seconds. With these modifications, acceptable cold welds were fabricated. After setting the conditions for an acceptable cold weld, the tube was TIG welded across the crimped face.

Holographic (de)confinement transitions in cosmological backgrounds

International Nuclear Information System (INIS)

Erdmenger, Johanna; Ghoroku, Kazuo; Meyer, Rene

2011-01-01

For type IIB supergravity with a running axio-dilaton, we construct bulk solutions which admit a cosmological background metric of Friedmann-Robertson-Walker type. These solutions include both a dark radiation term in the bulk as well as a four-dimensional (boundary) cosmological constant, while gravity at the boundary remains nondynamical. We holographically calculate the stress-energy tensor, showing that it consists of two contributions: The first one, generated by the dark radiation term, leads to the thermal fluid of N=4 SYM theory, while the second, the conformal anomaly, originates from the boundary cosmological constant. Conservation of the boundary stress-tensor implies that the boundary cosmological constant is time-independent, such that there is no exchange between the two stress-tensor contributions. We then study (de)confinement by evaluating the Wilson loop in these backgrounds. While the dark radiation term favors deconfinement, a negative cosmological constant drives the system into a confined phase. When both contributions are present, we find an oscillating universe with negative cosmological constant which undergoes periodic (de)confinement transitions as the scale of three-space expands and recontracts.

Block copolymer morphologies confined by square-shaped particle: Hard and soft confinement

International Nuclear Information System (INIS)

Zhang Qiyi; Yang Wenyan; Hu Kaiyan

2016-01-01

The self-assembly of diblock copolymers confined around one square-shaped particle is studied systematically within two-dimensional self-consistent field theory (SCFT). In this model, we assume that the thin block copolymer film is confined in the vicinity of a square-shaped particle by a homopolymer melt, which is equivalent to the poor solvents. Multiple sequences of square-shaped particle-induced copolymer aggregates with different shapes and self-assembled internal morphologies are predicted as functions of the particle size, the structural portion of the copolymer, and the volume fraction of the copolymer. A rich variety of aggregates are found with complex internal self-assembled morphologies including complex structures of the vesicle, with one or several inverted micelle surrounded by the outer monolayer with the particle confined in the core. These results demonstrate that the assemblies of diblock copolymers formed around the square-shaped particle in poor solvents are of immediate interest to the assembly of copolymer and the morphology of biomembrane in the confined environment, as well as to the transitions of vesicles to micelles. (paper)

Inward transport of a toroidally confined plasma subject to strong radial electric fields

Science.gov (United States)

Roth, J. R.; Krawczonek, W. M.; Powers, E. J.; Hong, J.; Kim, Y.

1977-01-01

The paper aims at showing that the density and confinement time of a toroidal plasma can be enhanced by radial electric fields far stronger than the ambipolar values, and that, if such electric fields point into the plasma, radially inward transport can result. The investigation deals with low-frequency fluctuation-induced transport using digitally implemented spectral analysis techniques and with the role of strong applied radial electric fields and weak vertical magnetic fields on plasma density and particle confinement times in a Bumpy Torus geometry. Results indicate that application of sufficiently strong radially inward electric fields results in radially inward fluctuation-induced transport into the toroidal electrostatic potential well; this inward transport gives rise to higher average electron densities and longer particle confinement times in the toroidal plasma.

Proceedings of JSPS-CAS Core University Program seminar on production and steady state confinement of high performance plasmas in magnetic confinement systems

International Nuclear Information System (INIS)

Wan Baonian; Toi, Kazuo

2005-09-01

The JSPS-CAS Core University Program (CUP) seminar on 'Production and steady-state confinement of high performance plasmas in magnetic confinement systems' was held from 27 July to 29 July 2005 in Institute of Plasma Physics, the Chinese Academy of Sciences, Hefei, China. This seminar was organized in the framework of CUP in the field of plasma and nuclear fusion. About 50 persons including 20 Japanese attendees attended this seminar. Long time sustainment of high confinement and high beta plasmas is crucial for realization of an advanced nuclear fusion reactor. This seminar was motivated to summarize the results of CUP obtained in four years activities of CUP, and to extract crucial issues to be resolved near future, which must drive near and mid- term collaborations in the framework of CUP. The 32 of presented papers are indexed individually. (J.P.N.)

Confinement and diffusion in tokamaks

International Nuclear Information System (INIS)

McWilliams, R.

1988-01-01

The effect of electric field fluctuations on confinement and diffusion in tokamak is discussed. Based on the experimentally determined cross-field turbolent diffusion coefficient, D∼3.7*cT e /eB(δn i /n i ) rms which is also derived by a simple theory, the cross-field diffusion time, tp=a 2 /D, is calculated and compared to experimental results from 51 tokamak for standard Ohmic operation

Preliminary study of energy confinement data with a statistical analysis system in HL-2A tokamak

International Nuclear Information System (INIS)

Xu Yuan; Cui Zhengying; Ji Xiaoquan; Dong Chunfeng; Yang Qingwei; O J W F Kardaun

2010-01-01

Taking advantage of the HL-2A experimental data,an energy confinement database facing ITERL DB2.0 version has been originally established. As for this database,a world widely used statistical analysis system (SAS) has been adopted for the first time to analyze and evaluate the confinement data from HL-2A and the research on scaling laws of energy confinement time corresponding to plasma density is developed, some preliminary results having been achieved. Finally, through comparing with both ITER scaling law and previous ASDEX database, the investigation about L-mode confinement quality on HL-2A and influence of temperature on Spitzer resistivity will be discussed. (authors)

Thermalization and confinement in strongly coupled gauge theories

Directory of Open Access Journals (Sweden)

Ishii Takaaki

2016-01-01

Full Text Available Quantum field theories of strongly interacting matter sometimes have a useful holographic description in terms of the variables of a gravitational theory in higher dimensions. This duality maps time dependent physics in the gauge theory to time dependent solutions of the Einstein equations in the gravity theory. In order to better understand the process by which “real world” theories such as QCD behave out of thermodynamic equilibrium, we study time dependent perturbations to states in a model of a confining, strongly coupled gauge theory via holography. Operationally, this involves solving a set of non-linear Einstein equations supplemented with specific time dependent boundary conditions. The resulting solutions allow one to comment on the timescale by which the perturbed states thermalize, as well as to quantify the properties of the final state as a function of the perturbation parameters. We comment on the influence of the dual gauge theory’s confinement scale on these results, as well as the appearance of a previously anticipated universal scaling regime in the “abrupt quench” limit.

Spatial confinement governs orientational order in patchy particles

Science.gov (United States)

Iwashita, Yasutaka; Kimura, Yasuyuki

2016-06-01

Orientational order in condensed matter plays a key role in determining material properties such as ferromagnetism, viscoelasticity or birefringence. We studied purely orientational ordering in closely-packed one-patch colloidal particles confined between flat substrates, where the particles can only rotate and are ordered via the sticky interaction between the patches. For the first time, we experimentally realized a rich variety of mesoscopic patterns through orientational ordering of colloids by controlling patch size and confinement thickness. The combination of experiment and numerical simulation reveals the decisive role of confinement: An ordered state(s) is selected from the (meta)stable options in bulk when it is commensurate with the system geometry and boundary conditions; otherwise, frustration induces a unique order. Our study offers a new means of systematic control over mesoscopic structures via orientational ordering in patchy particles. The system would also possess unique functionalities through the rotational response of the particles to external stimuli.

Elmo bumpy square plasma confinement device

Science.gov (United States)

Owen, L.W.

1985-01-01

The invention is an Elmo bumpy type plasma confinement device having a polygonal configuration of closed magnet field lines for improved plasma confinement. In the preferred embodiment, the device is of a square configuration which is referred to as an Elmo bumpy square (EBS). The EBS is formed by four linear magnetic mirror sections each comprising a plurality of axisymmetric assemblies connected in series and linked by 90/sup 0/ sections of a high magnetic field toroidal solenoid type field generating coils. These coils provide corner confinement with a minimum of radial dispersion of the confined plasma to minimize the detrimental effects of the toroidal curvature of the magnetic field. Each corner is formed by a plurality of circular or elliptical coils aligned about the corner radius to provide maximum continuity in the closing of the magnetic field lines about the square configuration confining the plasma within a vacuum vessel located within the various coils forming the square configuration confinement geometry.

Long-time impurity confinement as a precursor to disruptions in ohmically heated tokamaks

International Nuclear Information System (INIS)

Isler, R.C.; Rowan, W.L.

1988-01-01

It has been observed in several tokamaks that the confinement of test impurities increases dramatically when operating near density limits. The characteristics of the working gas transport coefficients also change character under these conditions. These changes appear to be caused by a suppression of the anomalous transport mechanisms. This series of vugraphs investigates the role of these changes in initiating disruptions

Anomalous Ground State of the Electrons in Nano-confined Water

Science.gov (United States)

2016-06-13

Anomalous ground state of the electrons in nano -confined water G. F. Reiter1*, Aniruddha Deb2*, Y. Sakurai3, M. Itou3, V. G. Krishnan4, S. J...electronic ground state of nano -confined water must be responsible for these anomalies but has so far not been investigated. We show here for the first time...using x-ray Compton scattering and a computational model, that the ground state configuration of the valence electrons in a particular nano

Evolution of particle clouds around ablating pellets in magnetically confined hot plasmas

International Nuclear Information System (INIS)

Lengyel, L.L.

1991-08-01

Cryogenic hydrogen isotope pellets are being currently used for introducing fuel particles into the palsma interior in magnetic confinement fusion experiments. The spatial and time evolution of the initially low-temperature high-density particle clouds forming around such pellets are considered here, with particular attention being given to such physical processes as heating of the cloud by the energy fluxes carried by incident plasma particles, gasdynamic expansion with j vectorxB vector - produced deceleration in the transverse direction, finite-rate ionization and recombination processes, and magnetic field convection and diffusion. While the dynamic processes associated with the ionization and radial confinement processes are characterized by the relatively short Alfven time scale (μs range), the subsequent phase of axial expansion is associated with a notably larger hadrodynamic time scale defined by the heat input and gasdynamic expansion rates (ms range). Data stemming from experimental measurements in toroidal confinement machines are compared with results of model calculations. Some similarities with space plasmas are briefly discussed. (orig.)

Generating equilateral random polygons in confinement III

International Nuclear Information System (INIS)

Diao, Y; Ernst, C; Montemayor, A; Ziegler, U

2012-01-01

In this paper we continue our earlier studies (Diao et al 2011 J. Phys. A: Math. Theor. 44 405202, Diao et al J. Phys. A: Math. Theor. 45 275203) on the generation methods of random equilateral polygons confined in a sphere. The first half of this paper is concerned with the generation of confined equilateral random walks. We show that if the selection of a vertex is uniform subject to the position of its previous vertex and the confining condition, then the distributions of the vertices are not uniform, although there exists a distribution such that if the initial vertex is selected following this distribution, then all vertices of the random walk follow this same distribution. Thus in order to generate a confined equilateral random walk, the selection of a vertex cannot be uniform subject to the position of its previous vertex and the confining condition. We provide a simple algorithm capable of generating confined equilateral random walks whose vertex distribution is almost uniform in the confinement sphere. In the second half of this paper we show that any process generating confined equilateral random walks can be turned into a process generating confined equilateral random polygons with the property that the vertex distribution of the polygons approaches the vertex distribution of the walks as the polygons get longer and longer. In our earlier studies, the starting point of the confined polygon is fixed at the center of the sphere. The new approach here allows us to move the starting point of the confined polygon off the center of the sphere. (paper)

Nonlinear quenches of power-law confining traps in quantum critical systems

International Nuclear Information System (INIS)

Collura, Mario; Karevski, Dragi

2011-01-01

We describe the coherent quantum evolution of a quantum many-body system with a time-dependent power-law confining potential. The amplitude of the inhomogeneous potential is driven in time along a nonlinear ramp which crosses a critical point. Using Kibble-Zurek-like scaling arguments we derive general scaling laws for the density of excitations and energy excess generated during the nonlinear sweep of the confining potential. It is shown that, with respect to the sweeping rate, the densities follow algebraic laws with exponents that depend on the space-time properties of the potential and on the scaling dimensions of the densities. We support our scaling predictions with both analytical and numerical results on the Ising quantum chain with an inhomogeneous transverse field varying in time.

Phenomenology and theory of confinement

International Nuclear Information System (INIS)

Pervushin, V.N.

1987-01-01

Phenomenological and theoretical arguments of the separation of the hadronization dynamics from confinement and the idea of the ''kinematic'' confinement are discussed. The recent theory contains results which point out that the Wilson criterion and the confinement potentials are not sufficient for explaining the phenomenological confinement in the sense of zero color amplitudes or Green functions. However, these potentials well explain the hadron spectrum and spontaneous breaking of chiral symmetry, i.e., the hadronization dynamics. The ''kinematic'' confinement can be explained by the topological degeneration of all color-particle physical states in QCD. This degeneration arises if the theory is quantized by explicitly solving the gauge and dynamic constraints: all color states are defined up to gauge(phase) factors describing the map of the three-dimensional space onto SU(3) c -group (π 3 (SU(3) c =Z). The total probability of the color particle generation is equal to zero due to the destructive interference of these phase factors. As a result, in QCD there remains only a hadron sector used in the phenomenology

On confinement and duality

Energy Technology Data Exchange (ETDEWEB)

Strassler, M J [University of Pennsylvania, Philadelphia, PA (United States)

2002-05-15

Confinement in four-dimensional gauge theories is considered from several points of view. General features are discussed, and the mechanism of confinement is investigated. Dualities between field theories, and duality between field theory and string theory, are both put to use. In these lectures I have given an overview of some of the key ideas underlying confinement as a property of field theory, and now, of string theory as well. This is a tiny fraction of what field theory (and now string theory) is capable of, and we are still uncovering new features on a monthly basis. In fact, most field theories do not have confinement, for reasons entirely different from those of QCD. Many become nontrivial conformal field theories at low energy. Others become composite, weakly-coupled gauge theories. Dualities of many stripes are found everywhere. Ordinary dimensional analysis in string theory is totally wrong in the regime where it looks like weakly-coupled field theory, and ordinary dimensional analysis in field theory is totally wrong in the regime where it looks like weakly-coupled supergravity.

Role of Lie algebra for confinement in non-abelian gauge field scheme

International Nuclear Information System (INIS)

Fukushima, K.; Sato, H.

2014-01-01

This article reports an explicit function form for confining classical Yang-Mills vector potentials and quantum fluctuations around the classical field. The classical vector potential, which is composed of a confining localized function and an unlocalized function, satisfies the classical Yang-Mills equation. The confining localized function contributes to the Wilson loop, while the unlocalized function makes no contribution to this loop. The confining linear potential between a heavy fermion and antifermion is due to (1) the Lie algebra and (2) the form of the confining localized function which has opposite signs at the positions of the particle and antiparticle along the Wilson loop in the time direction. Some classical confining parts of vector potentials also change sign on inversion of the coordinates of the axis perpendicular to the axis joining the two particles. The localized parts of the vector potentials are squeezed around the axis connecting the two particles, and the string tension of the confining linear potential is derived. Quantum fluctuations are formulated using a field expression in terms of local basis functions in real spacetime. The quantum path integral gives the Coulomb potential between the two particles in addition to the linear potential due to the classical fields

Phase transitions and quark confinement

International Nuclear Information System (INIS)

Polyakov, A.M.; Gava, E.

1978-02-01

The publication collects six lectures on the following themes: quantum field theory and classical statistical mechanics, continuous symmetries, lattice gauge theories, the nature of confinement, a criterion for confinement and non-abelian Yang-Mills theories

Generating random walks and polygons with stiffness in confinement

International Nuclear Information System (INIS)

Diao, Y; Ernst, C; Saarinen, S; Ziegler, U

2015-01-01

The purpose of this paper is to explore ways to generate random walks and polygons in confinement with a bias toward stiffness. Here the stiffness refers to the curvature angle between two consecutive edges along the random walk or polygon. The stiffer the walk (polygon), the smaller this angle on average. Thus random walks and polygons with an elevated stiffness have lower than expected curvatures. The authors introduced and studied several generation algorithms with a stiffness parameter s>0 that regulates the expected curvature angle at a given vertex in which the random walks and polygons are generated one edge at a time using conditional probability density functions. Our generating algorithms also allow the generation of unconfined random walks and polygons with any desired mean curvature angle. In the case of random walks and polygons confined in a sphere of fixed radius, we observe that, as expected, stiff random walks or polygons are more likely to be close to the confinement boundary. The methods developed here require that the random walks and random polygons be rooted at the center of the confinement sphere. (paper)

Surface-Activated Coupling Reactions Confined on a Surface.

Science.gov (United States)

Dong, Lei; Liu, Pei Nian; Lin, Nian

2015-10-20

Chemical reactions may take place in a pure phase of gas or liquid or at the interface of two phases (gas-solid or liquid-solid). Recently, the emerging field of "surface-confined coupling reactions" has attracted intensive attention. In this process, reactants, intermediates, and products of a coupling reaction are adsorbed on a solid-vacuum or a solid-liquid interface. The solid surface restricts all reaction steps on the interface, in other words, the reaction takes place within a lower-dimensional, for example, two-dimensional, space. Surface atoms that are fixed in the surface and adatoms that move on the surface often activate the surface-confined coupling reactions. The synergy of surface morphology and activity allow some reactions that are inefficient or prohibited in the gas or liquid phase to proceed efficiently when the reactions are confined on a surface. Over the past decade, dozens of well-known "textbook" coupling reactions have been shown to proceed as surface-confined coupling reactions. In most cases, the surface-confined coupling reactions were discovered by trial and error, and the reaction pathways are largely unknown. It is thus highly desirable to unravel the mechanisms, mechanisms of surface activation in particular, of the surface-confined coupling reactions. Because the reactions take place on surfaces, advanced surface science techniques can be applied to study the surface-confined coupling reactions. Among them, scanning tunneling microscopy (STM) and X-ray photoelectron spectroscopy (XPS) are the two most extensively used experimental tools. The former resolves submolecular structures of individual reactants, intermediates, and products in real space, while the latter monitors the chemical states during the reactions in real time. Combination of the two methods provides unprecedented spatial and temporal information on the reaction pathways. The experimental findings are complemented by theoretical modeling. In particular, density

Confined Space Evaluation Student Manual, #19613

Energy Technology Data Exchange (ETDEWEB)

Wilmot, David Ezekiel [Los Alamos National Laboratory

2016-08-29

Many workplaces contain spaces that are considered to be “confined” because their configuration hinders the activities of employees who must enter into, work in, and exit from them. In general, the permit-required confined spaces (PRCSs) Occupational Safety and Health Administration (OSHA) standard requires that Los Alamos National Laboratory (LANL) evaluate the workplace to determine if any spaces are PRCSs. The standard specifies strict procedures for the evaluation and atmospheric testing of a space before and during an entry by workers. The OSHA PRCS standard provides for alternative (less stringent than full-permit) entry procedures in cases where the only hazard in a space is atmospheric and the hazard can be controlled by forced air. At LANL, all confined spaces or potential confined spaces on LANL-owned or -operated property must be identified and evaluated by a confined space evaluator accompanied by a knowledgeable person. This course provides the information needed by confined space evaluators to make judgements about whether a space is a confined space, and if so, whether the space will require a permit for entry.

Sufficient condition for confinement of static quarks by a vortex condensation mechanism

International Nuclear Information System (INIS)

Mack, G.; Petkova, V.B.

1978-11-01

We derive a sufficient condition for confinement of static quarks by a vortex condensation mechanism. It admits vortices that are thick at all times at the cost of constraining them to a finite volume Λi whose complement is not simply connected. The confining potential V(L) is estimated in terms of the change of free energy of a system enclosed in Λi which is induced by a change in vorticity (= singular gauge transformation applied to boundary conditions on deltaΛi). For Abelian gauge theories in 3 dimensions the confining Coulomb potential is reproduced as a lower bound. (orig.) [de

Confinement properties of 2D porous molecular networks on metal surfaces

International Nuclear Information System (INIS)

Müller, Kathrin; Enache, Mihaela; Stöhr, Meike

2016-01-01

Quantum effects that arise from confinement of electronic states have been extensively studied for the surface states of noble metals. Utilizing small artificial structures for confinement allows tailoring of the surface properties and offers unique opportunities for applications. So far, examples of surface state confinement include thin films, artificial nanoscale structures, vacancy and adatom islands, self-assembled 1D chains, vicinal surfaces, quantum dots and quantum corrals. In this review we summarize recent achievements in changing the electronic structure of surfaces by adsorption of nanoporous networks whose design principles are based on the concepts of supramolecular chemistry. Already in 1993, it was shown that quantum corrals made from Fe atoms on a Cu(1 1 1) surface using single atom manipulation with a scanning tunnelling microscope confine the Shockley surface state. However, since the atom manipulation technique for the construction of corral structures is a relatively time consuming process, the fabrication of periodic two-dimensional (2D) corral structures is practically impossible. On the other side, by using molecular self-assembly extended 2D porous structures can be achieved in a parallel process, i.e. all pores are formed at the same time. The molecular building blocks are usually held together by non-covalent interactions like hydrogen bonding, metal coordination or dipolar coupling. Due to the reversibility of the bond formation defect-free and long-range ordered networks can be achieved. However, recently also examples of porous networks formed by covalent coupling on the surface have been reported. By the choice of the molecular building blocks, the dimensions of the network (pore size and pore to pore distance) can be controlled. In this way, the confinement properties of the individual pores can be tuned. In addition, the effect of the confined state on the hosting properties of the pores will be discussed in this review article

IL 14: Radiolysis of water confined in nano-porous materials

International Nuclear Information System (INIS)

Renault, J.P.; Pommeret, S.; Musat, R.; Le Caer, S.; Alam, M.; Mialocq, J.C.

2010-01-01

Radiolysis of water in nano-porous media has raised a lot of interest and involved research in the recent years, with respect to concerns arising from the storage of nuclear waste. In the civil nuclear industry, storing for a long time nuclear wastes requires safety evaluations in order to test the durability of the materials involved. Among these materials, concrete and clays are a complex heterogeneous material that traps important quantities of interstitial water. Irradiation that arises from the nuclear wastes stored in these materials may lead to the radiolysis of the interstitial water, and the formation of radiolytic products, such as H 2 , O 2 or H 2 O 2 that may cause the breaking or the corrosion of the confining matrix. This communication will describe the possible impacts of confinement on the radiolysis of water. We will especially discuss the current knowledge about the evolution of radiolytic yields of primary species (hydroxyl radical, dihydrogen, aqueous electron) as a function of the degree of confinement and of the nature of the confining material. SEM picture of a nano-porous gold sample used to study the radiolysis of confined water The yield enhancement observed in many cases revealed original energy and charge transfer phenomena that we tried to decipher. (authors)

Analytical results for the time-dependent current density distribution of expanding ultracold gases after a sudden change of the confining potential

Science.gov (United States)

Boumaza, R.; Bencheikh, K.

2017-12-01

Using the so-called operator product expansion to lowest order, we extend the work in Campbell et al (2015 Phys. Rev. Lett 114 125302) by deriving a simple analytical expression for the long-time asymptotic one-body reduced density matrix during free expansion for a one-dimensional system of bosons with large atom number interacting through a repulsive delta potential initially confined by a potential well. This density matrix allows direct access to the momentum distribution and also to the mass current density. For initially confining power-law potentials we give explicit expressions, in the limits of very weak and very strong interaction, for the current density distributions during the free expansion. In the second part of the work we consider the expansion of ultracold gas from a confining harmonic trap to another harmonic trap with a different frequency. For the case of a quantum impenetrable gas of bosons (a Tonks-Girardeau gas) with a given atom number, we present an exact analytical expression for the mass current distribution (mass transport) after release from one harmonic trap to another harmonic trap. It is shown that, for a harmonically quenched Tonks-Girardeau gas, the current distribution is a suitable collective observable and under the weak quench regime, it exhibits oscillations at the same frequencies as those recently predicted for the peak momentum distribution in the breathing mode. The analysis is extended to other possible quenched systems.

Advanced energy systems: 2XIIB: heating and containing magnetically confined plasmas

International Nuclear Information System (INIS)

Coensgen, F.H.

1975-01-01

Recent experiments on the 2XIIB mirror machine have produced encouraging results: a buildup of hot ion densities to 4 x 10 13 cm -3 , ion temperatures of 13 keV (the highest ever observed in a major fusion experiment), and a confinement time exceeding 5 ms. Two major factors in these achievements were the injection of twelve 20-keV neutral beams to increase plasma temperature and the introduction of warm streaming plasma to suppress microinstabilities. With them, near-classical confinement of a hot plasma was demonstrated. We are now doubling the injected neutral beam energy to see if plasma stability and energy scaling of plasma confinement persist at higher ion temperatures

Confinement scaling and ignition in tokamaks

International Nuclear Information System (INIS)

Perkins, F.W.; Sun, Y.C.

1985-10-01

A drift wave turbulence model is used to compute the scaling and magnitude of central electron temperature and confinement time of tokamak plasmas. The results are in accord with experiment. Application to ignition experiments shows that high density (1 to 2) . 10 15 cm -3 , high field, B/sub T/ > 10 T, but low temperature T approx. 6 keV constitute the optimum path to ignition

Confinement of nonneutral spheroidal plasmas in multi-ring electrode traps

International Nuclear Information System (INIS)

Mohri, Akihiro; Yuyama, Tetsumori; Michishita, Toshinori; Higaki, Hiroyuki; Tanaka, Hitoshi; Yamazawa, Yohei; Aoyagi, Masayuki

1998-01-01

A nonneutral spheroidal plasma can be settled in a rigid rotor equilibrium inside a closed conducting cell independently of induced image charges on the cell wall if the electrostatic potential distribution on the wall surface is set equal to the sum of the external hyperbolic potential (r 2 -2z 2 ) and the self-potential produced by the plasma. A confinement system equipped with a train of properly biased ring electrodes can approximately generate any axisymmetric potential, including the above field. Experiments on confinement of electron spheroids in such a system showed that the confinement time became the longest when the condition to diminish the image charge effects was satisfied. The observed frequency of the centre-of-mass harmonic oscillation of the plasma in this configuration was in good agreement with the estimated one. (author)

Atom-atom scattering under cylindrical harmonic confinement: Numerical and analytic studies of the confinement induced resonance

International Nuclear Information System (INIS)

Bergeman, T.; Moore, M.G.; Olshanii, M.

2003-01-01

It was recently predicted [Phys. Rev. Lett. 81, 938 (1998)10.1103/PhysRevLett.81.938] that atom-atom scattering under transverse harmonic confinement is subject to a 'confinement-induced resonance' where the effective one-dimensional coupling strength diverges at a particular ratio of the confinement and scattering lengths. As the initial prediction made use of the zero-range pseudopotential approximation, we now report numerical results for finite-range interaction potentials that corroborate this resonance. In addition, we now present a physical interpretation of this effect as a novel type of Feshbach resonance in which the transverse modes of the confining potential assume the roles of 'open' and 'closed' scattering channels

Topological superfluids confined in a regular nano-scale slab geometry

Energy Technology Data Exchange (ETDEWEB)

Saunders, John; Bennett, Robert; Levitin, Lev; Casey, Andrew; Cowan, Brian [Department of Physics, Royal Holloway University of London, Egham, Surrey, TW20 0EX (United Kingdom); Parpia, Jeevak [Department of Physics, Cornell University, Ithaca, NY 14853 (United States); Drung, Dietmar; Schurig, Thomas [Physikalisch-Technische Bundesanstalt, Abbestrasse 2-12, D-19587, Berlin (Germany)

2012-07-01

Superfluid 3He confined in a regular nano-fabricated slab geometry provides a model system for the investigation of surface and thin film effects in a p-wave superfluid. We have fabricated and cooled such samples to well below 1 mK for the first time, and investigated their NMR response, exploiting a SQUID NMR spectrometer of exquisite sensitivity. We have used NMR on a 650 nm thick superfluid slab to identify the profound effect of confinement on the relative stability of the A and B phases and to make quantitative measurements of the suppression and surface induced distortion of the order parameter. In these systems the effective confinement length scale (slab thickness/superfluid coherence length) is the new tuning parameter. Increasing confinement should stabilize new p-wave superfluid states of matter, such as the quasi-2D gapped A phase or the planar phase. Nanofluidic samples of superfluid 3He promise a route to explore topological superfluids and their surface, edge and defect-bound excitations under well controlled conditions.

Confinement effects and mechanistic aspects for montmorillonite nanopores.

Science.gov (United States)

Li, Xiong; Zhu, Chang; Jia, Zengqiang; Yang, Gang

2018-08-01

Owing to the ubiquity, critical importance and special properties, confined microenvironments have recently triggered overwhelming interest. In this work, all-atom molecular dynamics simulations have been conducted to address the confinement effects and ion-specific effects for electrolyte solutions within montmorillonite nanopores, where the pore widths vary with a wide range. The adsorption number, structure, dynamics and stability of inner- and outer-sphere metal ions are affected by the change of pore widths (confinement effects), while the extents are significantly dependent on the type of adsorbed species. The type of adsorbed species is, however, not altered by the magnitude of confinement effects, and confinement effects are similar for different electrolyte concentrations. Ion-specific effects are pronounced for all magnitudes of confinement effects (from non- to strong confined conditions), and Hofmeister sequences of outer-sphere species are closely associated with the magnitude of confinement effects while those of inner-sphere species remain consistent. In addition, mechanistic aspects of confinement have been posed using the electrical double layer theories, and the results can be generalized to other confined systems that are ubiquitous in biology, chemistry, geology and nanotechnology. Copyright © 2018 Elsevier Inc. All rights reserved.

Ignition and burn in inertially confined magnetized fuel

International Nuclear Information System (INIS)

Kirkpatrick, R.C.; Lindemuth, I.R.

1991-01-01

At the third International Conference on Emerging Nuclear Energy Systems, we presented computational results which suggested that ''breakeven'' experiments in inertial confinement fusion (ICF) may be possible with existing driver technology. We recently used the ICF simulation code LASNEX to calculate the performance of an idealized magnetized fuel target. The parameter space in which magnetized fuel operates is remote from that of both ''conventional'' ICF and magnetic confinement fusion devices. In particular, the plasma has a very high β and is wall confined, not magnetically confined. The role of the field is to reduce the electron thermal conductivity and to partially trap the DT alphas. The plasma is contained in a pusher which is imploded to compress and adiabatically heat the plasma from an initial condition of preheat and pre-magnetization to the conditions necessary for fusion ignition. The initial density must be quite low by ICF standards in order to insure that the electron thermal conductivity is suppressed and to minimize the generation of radiation from the plasma. Because the energy loss terms are effectively suppressed, the implosion may proceed at a relatively slow rate of about 1 to 3 cm/μs. Also, the need for low density fuel dictates a much larger target, so that magnetized fuel can use drivers with much lower power and power density. Therefore, magnetized fuel allows the use of efficient drivers that are not suitable for laser or particle beam fusion due to insufficient focus or too long pulse length. The ignition and burn of magnetized fuel involves very different dominant physical processes than does ''conventional'' ICF. The fusion time scale becomes comparable to the hydrodynamic time scale, but other processes that limit the burn in unmagnetized fuel are of no consequence. The idealized low gain magnetized fuel target presented here is large and requires a very low implosion velocity. 11 refs

Holographic collisions in confining theories

International Nuclear Information System (INIS)

Cardoso, Vitor; Emparan, Roberto; Mateos, David; Pani, Paolo; Rocha, Jorge V.

2014-01-01

We study the gravitational dual of a high-energy collision in a confining gauge theory. We consider a linearized approach in which two point particles traveling in an AdS-soliton background suddenly collide to form an object at rest (presumably a black hole for large enough center-of-mass energies). The resulting radiation exhibits the features expected in a theory with a mass gap: late-time power law tails of the form t −3/2 , the failure of Huygens’ principle and distortion of the wave pattern as it propagates. The energy spectrum is exponentially suppressed for frequencies smaller than the gauge theory mass gap. Consequently, we observe no memory effect in the gravitational waveforms. At larger frequencies the spectrum has an upward-stairway structure, which corresponds to the excitation of the tower of massive states in the confining gauge theory. We discuss the importance of phenomenological cutoffs to regularize the divergent spectrum, and the aspects of the full non-linear collision that are expected to be captured by our approach

MRT Lattice Boltzmann schemes for confined suspension flows

NARCIS (Netherlands)

Sman, van der R.G.M.

2010-01-01

We introduce a novel multiple-relaxation time (modified MRT) Lattice Boltzmann scheme for simulation of confined suspension flow. Via careful tuning of the free eigenvalues of the collision operator we can substantially reduce the error in the so-called hydrodynamic radius. Its performance has been

Ion confinement and transport in a toroidal plasma with externally imposed radial electric fields

Science.gov (United States)

Roth, J. R.; Krawczonek, W. M.; Powers, E. J.; Kim, Y. C.; Hong, H. Y.

1979-01-01

Strong electric fields were imposed along the minor radius of the toroidal plasma by biasing it with electrodes maintained at kilovolt potentials. Coherent, low-frequency disturbances characteristic of various magnetohydrodynamic instabilities were absent in the high-density, well-confined regime. High, direct-current radial electric fields with magnitudes up to 135 volts per centimeter penetrated inward to at least one-half the plasma radius. When the electric field pointed radially toward, the ion transport was inward against a strong local density gradient; and the plasma density and confinement time were significantly enhanced. The radial transport along the electric field appeared to be consistent with fluctuation-induced transport. With negative electrode polarity the particle confinement was consistent with a balance of two processes: a radial infusion of ions, in those sectors of the plasma not containing electrodes, that resulted from the radially inward fields; and ion losses to the electrodes, each of the which acted as a sink and drew ions out of the plasma. A simple model of particle confinement was proposed in which the particle confinement time is proportional to the plasma volume. The scaling predicted by this model was consistent with experimental measurements.

Potential formation and confinement in high density plasma on the GAMMA 10 tandem mirror

International Nuclear Information System (INIS)

Yatsu, K.

2002-01-01

After the attainment of doubling of the density due to the potential confinement, GAMMA 10 experiments have been directed to realization of a high density plasma and also to study dependence of the confining potential and confinement time on the plasma density. These problems are important to understand the physics of potential formation in tandem mirrors and also for the development of a tandem mirror reactor. We reported high density plasma production by using an ion cyclotron range of frequency heating at a high harmonic frequency in the last IAEA Conference. However, the diamagnetic signal of the high density plasma decreased when electron cyclotron resonance heating (ECRH) was applied due to some instabilities. Recently, the high density plasma production was much improved by adjusting the spacing of the conducting plates installed in the anchor transition regions, which enabled us to produce a high density plasma without degradation of the diamagnetic signal with ECRH and also to study the density dependence. In this paper we report production of a high density plasma and dependence of the confining potential and the confinement time on the density. (author)

Ductility of reinforced concrete columns confined with stapled strips

International Nuclear Information System (INIS)

Tahir, M.F.; Khan, Q.U.Z.; Shabbir, F.; Sharif, M.B.; Ijaz, N.

2015-01-01

Response of three 150x150x450mm short reinforced concrete (RC) columns confined with different types of confining steel was investigated. Standard stirrups, strips and stapled strips, each having same cross-sectional area, were employed as confining steel around four comer column bars. Experimental work was aimed at probing into the affect of stapled strip confinement on post elastic behavior and ductility level under cyclic axial load. Ductility ratios, strength enhancement factor and core concrete strengths were compared to study the affect of confinement. Results indicate that strength enhancement in RC columns due to strip and stapled strip confinement was not remarkable as compared to stirrup confined column. It was found that as compared to stirrup confined column, stapled strip confinement enhanced the ductility of RC column by 183% and observed axial capacity of stapled strip confined columns was 41 % higher than the strip confined columns. (author)

The Enskog Equation for Confined Elastic Hard Spheres

Science.gov (United States)

Maynar, P.; García de Soria, M. I.; Brey, J. Javier

2018-03-01

A kinetic equation for a system of elastic hard spheres or disks confined by a hard wall of arbitrary shape is derived. It is a generalization of the modified Enskog equation in which the effects of the confinement are taken into account and it is supposed to be valid up to moderate densities. From the equation, balance equations for the hydrodynamic fields are derived, identifying the collisional transfer contributions to the pressure tensor and heat flux. A Lyapunov functional, H[f], is identified. For any solution of the kinetic equation, H decays monotonically in time until the system reaches the inhomogeneous equilibrium distribution, that is a Maxwellian distribution with a density field consistent with equilibrium statistical mechanics.

An introduction to the confinement problem

International Nuclear Information System (INIS)

Greensite, Jeff

2011-01-01

This book addresses the confinement problem, which quite generally deals with the behavior of non-abelian gauge theories, and the force which is mediated by gauge fields, at large distances.The word ''confinement'' in the context of hadronic physics originally referred to the fact that quarks and gluons appear to be trapped inside mesons and baryons, from which they cannot escape. There are other, and possibly deeper meanings that can be attached to the term, and these will be explored in this book. Although the confinement problem is far from solved, much is now known about the general features of the confining force, and there are a number of very well motivated theories of confinement which are under active investigation. This volume gives a both pedagogical and concise introduction and overview of the main ideas in this field, their attractive features, and, as appropriate, their shortcomings. (orig.)

Structure in a confined smectic liquid crystal with competing surface and sample elasticities

International Nuclear Information System (INIS)

Idziak, S.H.; Koltover, I.; Israelachvili, J.N.; Safinya, C.R.

1996-01-01

We report on studies using the x-ray surface forces apparatus (XSFA) to compare the structure of a liquid crystal confined between hard surfaces and, for the first time, between soft surfaces that can deform due to the stresses imposed by the confined fluid. We find that the alignment of smectic domains in confined films depends critically on both the shape and compliance of the confining walls or surfaces: open-quote open-quote Soft surfaces close-quote close-quote exhibit a critical gap thickness of 3.4 μm for the liquid crystal studied at which maximum alignment occurs, while open-quote open-quote hard surfaces close-quote close-quote do not exhibit gap-dependent alignment. copyright 1996 The American Physical Society

Confinement dynamics in the reversed field pinch

International Nuclear Information System (INIS)

Schoenberg, K.F.

1988-01-01

The study of basic transport and confinement dynamics is central to the development of the reversed field pinch (RFP) as a confinement concept. Thus, the goal of RFP research is to understand the connection between processes that sustain the RFP configuration and related transport/confinement properties. Recently, new insights into confinement have emerged from a detailed investigation of RFP electron and ion physics. These insights derive from the recognition that both magnetohydrodynamic (MHD) and electron kinetic effects play an important and strongly coupled role in RFP sustainment and confinement dynamics. In this paper, we summarize the results of these studies on the ZT-40M experiment. 8 refs

Improved confinement mode induced by the MARFE on the HT-7 superconducting tokamak

International Nuclear Information System (INIS)

Gao, X.; Zhao, Y.P.; Luo, J.R.; Jie, Y.X.; Gong, X.Z.; Wan, B.N.; Li, J.G.; Yin, F.X.; Kuang, G.L.; Zhang, X.D.; Zhang, S.Y.; Qiu, N.; Liu, X.N.; Zhao, J.Y.; Yang, Y.; Bao, Y.; Lin, B.L.; Wu, Z.W.; Li, Y.D.; Xu, Y.H.; Yang, K.; Wang, G.X.; Ye, W.W.; Chen, L.; Shi, Y.J.; Song, M.; Zhang, X.M.; Qin, P.J.; Gu, X.M.; Cui, N.Z.; Fan, H.Y.; Liu, S.X.; Chen, Y.F.; Hu, L.Q.; Hu, J.S.; Xia, C.Y.; Ruan, H.L.; Tong, X.D.; Mao, J.S.; Xie, J.K.; Wan, Y.X.

1999-01-01

In the HT-7 superconducting tokamak, the onset of a multifaceted asymmetric radiation from the edge (MARFE) usually occurs in the early ohmic discharges of each experimental campaign before wall conditioning. The occurrence and location of a MARFE is identified by different diagnostic systems. An improved confinement mode plasma which was induced by the MARFE is observed, and the global particle confinement time increases 1.9 times. The relaxation time between the MARFE event trigger and the L-H transition is about 1.4 ms, the following L-H transition time is 1.9 ms, and the improved confinement mode phase is maintained for about 40 ms. The MARFE cools the plasma edge, and the electron density profile is observed to become more narrow and peaked. The occurrence of a MARFE is strongly correlated with Z eff but not with the density, and it always occurs at Z eff = 3-8 ohmic discharges. In the case of a good wall condition (Z eff = 1-2), the onset of MARFEs has not been observed before reaching the Greenwald density limit. (author)

A comprehensive alpha-heating model for inertial confinement fusion

Science.gov (United States)

Christopherson, A. R.; Betti, R.; Bose, A.; Howard, J.; Woo, K. M.; Campbell, E. M.; Sanz, J.; Spears, B. K.

2018-01-01

A comprehensive model is developed to study alpha-heating in inertially confined plasmas. It describes the time evolution of a central low-density hot spot confined by a compressible shell, heated by fusion alphas, and cooled by radiation and thermal losses. The model includes the deceleration, stagnation, and burn phases of inertial confinement fusion implosions, and is valid for sub-ignited targets with ≤10 × amplification of the fusion yield from alpha-heating. The results of radiation-hydrodynamic simulations are used to derive realistic initial conditions and dimensionless parameters for the model. It is found that most of the alpha energy (˜90%) produced before bang time is deposited within the hot spot mass, while a small fraction (˜10%) drives mass ablation off the inner shell surface and its energy is recycled back into the hot spot. Of the bremsstrahlung radiation emission, ˜40% is deposited in the hot spot, ˜40% is recycled back in the hot spot by ablation off the shell, and ˜20% leaves the hot spot. We show here that the hot spot, shocked shell, and outer shell trajectories from this analytical model are in good agreement with simulations. A detailed discussion of the effect of alpha-heating on the hydrodynamics is also presented.

Configuration control for the confinement improvement in Heliotron J

Energy Technology Data Exchange (ETDEWEB)

Mizuuchi, T.; Sano, F.; Kondo, K.; Nagasaki, K.; Okada, H.; Kobayashi, S.; Torii, Y.; Yamamoto, S.; Hanatani, K.; Nakamura, Y.; Kaneko, M.; Arimoto, H.; Motojima, G.; Fujikawa, S.; Kitagawa, H.; Nakamura, H.; Tsuji, T.; Uno, M.; Yabutani, H.; Watanabe, S.; Matsuoka, S.; Nosaku, M.; Watanabe, N.; Ijiri, Y.; Senju, T.; Yaguchi, K.; Sakamoto, K.; Toshi, K.; Shibano, M.; Murakami, S.; Suzuki, Y.; Yokoyama, M.

2005-07-01

In the helical-axis heliotron configuration, bumpiness of the Fourier components in Boozer coordinates is introduced as a third knob to control the neo-classical transport. Effects of the bumpiness control on the plasma performance (non-inductive currents, fast ions behavior and global energy confinement) have been investigated in Heliotron J by selecting three configurations with different bumpiness (B04/B00 = 0.01, 0.06 and 0.15 at ? 2/3), almost the same edge rotational transform and plasma volume. The dependence of non-inductive toroidal currents is qualitatively consistent with the neoclassical prediction for the bootstrap current. The high bumpiness configuration seems to be preferable for the confinement of fast ions. However, the longer global energy confinement time is observed not in the highest bumpiness configuration (B04/B00 = 0.15) but in the configuration with the minimum effective ripple modulation amplitude, where B04/B00 is 0.06. (Author)

Multi-Quanta Spin-Locking Nuclear Magnetic Resonance Relaxation Measurements: An Analysis of the Long-Time Dynamical Properties of Ions and Water Molecules Confined within Dense Clay Sediments

Directory of Open Access Journals (Sweden)

Patrice Porion

2017-11-01

Full Text Available Solid/liquid interfaces are exploited in various industrial applications because confinement strongly modifies the physico-chemical properties of bulk fluids. In that context, investigating the dynamical properties of confined fluids is crucial to identify and better understand the key factors responsible for their behavior and to optimize their structural and dynamical properties. For that purpose, we have developed multi-quanta spin-locking nuclear magnetic resonance relaxometry of quadrupolar nuclei in order to fill the gap between the time-scales accessible by classical procedures (like dielectric relaxation, inelastic and quasi-elastic neutron scattering and obtain otherwise unattainable dynamical information. This work focuses on the use of quadrupolar nuclei (like 2H, 7Li and 133Cs, because quadrupolar isotopes are the most abundant NMR probes in the periodic table. Clay sediments are the confining media selected for this study because they are ubiquitous materials implied in numerous industrial applications (ionic exchange, pollutant absorption, drilling, waste storing, cracking and heterogeneous catalysis.

Confinement-induced resonances in anharmonic waveguides

Energy Technology Data Exchange (ETDEWEB)

Peng Shiguo [Department of Physics, Tsinghua University, Beijing 100084 (China); Centre for Atom Optics and Ultrafast Spectroscopy, Swinburne University of Technology, Melbourne 3122 (Australia); Hu Hui; Liu Xiaji; Drummond, Peter D. [Centre for Atom Optics and Ultrafast Spectroscopy, Swinburne University of Technology, Melbourne 3122 (Australia)

2011-10-15

We develop the theory of anharmonic confinement-induced resonances (ACIRs). These are caused by anharmonic excitation of the transverse motion of the center of mass (c.m.) of two bound atoms in a waveguide. As the transverse confinement becomes anisotropic, we find that the c.m. resonant solutions split for a quasi-one-dimensional (1D) system, in agreement with recent experiments. This is not found in harmonic confinement theories. A new resonance appears for repulsive couplings (a{sub 3D}>0) for a quasi-two-dimensional (2D) system, which is also not seen with harmonic confinement. After inclusion of anharmonic energy corrections within perturbation theory, we find that these ACIRs agree extremely well with anomalous 1D and 2D confinement-induced resonance positions observed in recent experiments. Multiple even- and odd-order transverse ACIRs are identified in experimental data, including up to N=4 transverse c.m. quantum numbers.

Elastic scattering of positronium: Application of the confined variational method

KAUST Repository

Zhang, Junyi

2012-08-01

We demonstrate for the first time that the phase shift in elastic positronium-atom scattering can be precisely determined by the confined variational method, in spite of the fact that the Hamiltonian includes an unphysical confining potential acting on the center of mass of the positron and one of the atomic electrons. As an example, we study the S-wave elastic scattering for the positronium-hydrogen scattering system, where the existing 4% discrepancy between the Kohn variational calculation and the R-matrix calculation is resolved. © Copyright EPLA, 2012.

Elastic scattering of positronium: Application of the confined variational method

KAUST Repository

Zhang, Junyi; Yan, Zong-Chao; Schwingenschlö gl, Udo

2012-01-01

We demonstrate for the first time that the phase shift in elastic positronium-atom scattering can be precisely determined by the confined variational method, in spite of the fact that the Hamiltonian includes an unphysical confining potential acting on the center of mass of the positron and one of the atomic electrons. As an example, we study the S-wave elastic scattering for the positronium-hydrogen scattering system, where the existing 4% discrepancy between the Kohn variational calculation and the R-matrix calculation is resolved. © Copyright EPLA, 2012.

High-β, improved confinement reversed-field pinch plasmas at high density

International Nuclear Information System (INIS)

Wyman, M. D.; Chapman, B. E.; Ahn, J. W.; Almagri, A. F.; Anderson, J. K.; Den Hartog, D. J.; Ebrahimi, F.; Ennis, D. A.; Fiksel, G.; Gangadhara, S.; Goetz, J. A.; O'Connell, R.; Oliva, S. P.; Prager, S. C.; Reusch, J. A.; Sarff, J. S.; Stephens, H. D.; Bonomo, F.; Franz, P.; Brower, D. L.

2008-01-01

In Madison Symmetric Torus [Dexter et al., Fusion Technol. 19, 131 (1991)] discharges where improved confinement is brought about by modification of the current profile, pellet injection has quadrupled the density, reaching n e =4x10 19 m -3 . Without pellet injection, the achievable density in improved confinement discharges had been limited by edge-resonant tearing instability. With pellet injection, the total beta has been increased to 26%, and the energy confinement time is comparable to that at low density. Pressure-driven local interchange and global tearing are predicted to be linearly unstable. Interchange has not yet been observed experimentally, but there is possible evidence of pressure-driven tearing, an instability usually driven by the current gradient in the reversed-field pinch

Confinement of antihydrogen for 1000 seconds

CERN Document Server

Andresen, G B; Baquero-Ruiz, M; Bertsche, W; Butler, E; Cesar, C L; Deller, A; Eriksson, S; Fajans, J; Friesen, T; Fujiwara, M C; Gill, D R; Gutierrez, A; Hangst, J S; Hardy, W N; Hayano, R S; Hayden, M E; Humphries, A J; Hydomako, R; Jonsell, S; Kemp, S; Kurchaninov, L; Madsen, N; Menary, S; Nolan, P; Olchanski, K; Olin, A; Pusa, P; Rasmussen, C Ø; Robicheaux, F; Sarid, E; Silveira, D M; So, C; Storey, J W; Thompson, R I; van der Werf, D P; Wurtele, J S; Yamazaki, Y

2011-01-01

Atoms made of a particle and an antiparticle are unstable, usually surviving less than a microsecond. Antihydrogen, made entirely of antiparticles, is believed to be stable, and it is this longevity that holds the promise of precision studies of matter-antimatter symmetry. We have recently demonstrated trapping of antihydrogen atoms by releasing them after a confinement time of 172 ms. A critical question for future studies is: how long can anti-atoms be trapped? Here we report the observation of anti-atom confinement for 1000 s, extending our earlier results by nearly four orders of magnitude. Our calculations indicate that most of the trapped anti-atoms reach the ground state. Further, we report the first measurement of the energy distribution of trapped antihydrogen which, coupled with detailed comparisons with simulations, provides a key tool for the systematic investigation of trapping dynamics. These advances open up a range of experimental possibilities, including precision studies of CPT symmetry and ...

Effects of ECRH power and safety factor on laser blow-off injected impurity confinement in TCV

International Nuclear Information System (INIS)

Scavino, E; Bakos, J; Weisen, H

2004-01-01

Evidence from injection into the TCV device of laser ablated, non-recycling silicon impurities shows that the transport of impurities confinement can be remarkably different from that of energy. The ratio of impurity to energy confinement times ranges from near unity in Ohmic discharges to 5 in the presence of high power ECCD. In Ohmic discharges in deuterium, above a threshold of density and of safety factor near q 95 = 4.5, the impurity confinement time increases abruptly by a factor of 2 and is sometimes accompanied by indefinite retention of non-recycling impurities within the sawtooth mixing radius

On the implications of confinement

International Nuclear Information System (INIS)

Roberts, C.D.

1992-01-01

In this paper, the authors consider some implications of confinement starting from the basic observation that cross-sections for the production of colored asymptotic states, such as free quarks and gluons, from color singlet initial states must be zero if QCD is to be confining. The authors discuss two pictures of confinement: the failure of the cluster decomposition property and the absence of a pole at timelike momenta in the propagator of a confined particle. The authors use QCD-based models as a framework to relate the failure of the cluster decomposition property to other ideas, such as the role of a nonzero gluon condensate. The authors' primary interest is to address the question of the absence of a mass pole through a study of model Schwinger-Dyson equations. These equations contain some of the dynamical information that is present in the study of the cluster decomposition property. The authors discuss the problems within this idea and its study using the Schwinger-Dyson equations

Mechanical collapse of confined fluid membrane vesicles.

Science.gov (United States)

Rim, Jee E; Purohit, Prashant K; Klug, William S

2014-11-01

Compact cylindrical and spherical invaginations are common structural motifs found in cellular and developmental biology. To understand the basic physical mechanisms that produce and maintain such structures, we present here a simple model of vesicles in confinement, in which mechanical equilibrium configurations are computed by energy minimization, balancing the effects of curvature elasticity, contact of the membrane with itself and the confining geometry, and adhesion. For cylindrical confinement, the shape equations are solved both analytically and numerically by finite element analysis. For spherical confinement, axisymmetric configurations are obtained numerically. We find that the geometry of invaginations is controlled by a dimensionless ratio of the adhesion strength to the bending energy of an equal area spherical vesicle. Larger adhesion produces more concentrated curvatures, which are mainly localized to the "neck" region where the invagination breaks away from its confining container. Under spherical confinement, axisymmetric invaginations are approximately spherical. For extreme confinement, multiple invaginations may form, bifurcating along multiple equilibrium branches. The results of the model are useful for understanding the physical mechanisms controlling the structure of lipid membranes of cells and their organelles, and developing tissue membranes.

Confined subdiffusion in three dimensions

International Nuclear Information System (INIS)

Qin Shan-Lin; He Yong

2014-01-01

Three-dimensional (3D) Fick's diffusion equation and fractional diffusion equation are solved for different reflecting boundaries. We use the continuous time random walk model (CTRW) to investigate the time-averaged mean square displacement (MSD) of a 3D single particle trajectory. Theoretical results show that the ensemble average of the time-averaged MSD can be expressed analytically by a Mittag—Leffler function. Our new expression is in agreement with previous formulas in two limiting cases: <δ 2 -bar> ∼ Δ in short lag time and <δ 2 -bar> ∼ Δ 1-α in long lag time. We also simulate the experimental data of mRNA diffusion in living E. coli using a 3D CTRW model under confined and crowded conditions. The simulation results are well consistent with experimental results. The calculations of power spectral density (PSD) further indicate the subdiffsive behavior of an individual trajectory. (general)

The role of edge physics and confinement issues in the fusion reactor

International Nuclear Information System (INIS)

Lackner, K.; Schneider, R.

1993-01-01

The compatibility of the power exhaust to the walls and target plates with an adequate survival time of these structures and a sufficiently low impurity concentration in the bulk plasma, on the one hand, and the scaling of the energy confinement time with the tokamak parameters, on the other, are presently seen as two of the most critical issues determining the viability and minimum size of a fusion reactor. Statistical analysis of the world-wide data base of divertor tokamaks and experimental progress in superposing different forms of confinement improvements instil confidence that tokamak devices with the dimensions of ITER can meet the energy confinement requirements for ignition when operating in the H-regime. The critical problem consists, however, in simultaneously satisfying both the impurity and energy confinement related requirements. Regimes of improved confinement also tend to show a reduced rate of outward flow of impurities, thus increasing (for a given production rate at the walls or - in the case of helium - in the interior) their expected concentration. The confinement improvement in the H-regime also extends beyond the separatrix, leading to a thinner scrape-off layer with enhanced power concentration at the target plate and an enhanced penetration of impurities into the bulk plasma. These issues have therefore become the focal point of divertor and H-regime studies. Experiments on ASDEX, DIII-D and JET have successfully demonstrated that the impurity concentration in the H-regime can be effectively limited by the spontaneous cyclic destruction of the transport barrier at the edge (through the so-called ELMs) with only partial sacrifice of the energy confinement improvement. Expectations of handling the power load issues hinge on the capability of the divertor solution to decouple plasma properties in the edge of the bulk plasma from those near the target plates and the possibility of converting the energy flux arriving in the divertor into

Origin of the various beta dependences of ELMy H-mode confinement properties

International Nuclear Information System (INIS)

Takizuka, T; Urano, H; Takenaga, H; Oyama, N

2006-01-01

Dependence of the energy confinement in ELMy H-mode tokamak on the beta has been investigated for a long time, but a common conclusion has not been obtained so far. Recent non-dimensional transport experiments in JT-60U demonstrated clearly the beta degradation. A database for JT-60U ELMy H-mode confinement was assembled. Analysis of this database is carried out, and the strong beta degradation consistent with the above experiments is confirmed. Two subsets of ASDEX Upgrade and JET data in the ITPA H-mode confinement database are analysed to find the origin of the various beta dependences. The shaping of the plasma cross section, as well as the fuelling condition, affects the confinement performance. The beta dependence is not identical for different devices and conditions. The shaping effect, as well as the fuelling effect, is a possible candidate for causing the variation of beta dependence

Confinement and the Pomeron

International Nuclear Information System (INIS)

White, A.R.

1989-01-01

The importance of confinement for obtaining a unitary high-energy limit for QCD is discussed. ''Minijets'' are argued to build up non-unitary behavior endash when k T > Λ is imposed. For minijets to mix with low k T Pomeron Field Theory describing confinement, and give consistent asymptotic behavior, new ''quarks'' must enter the theory above the minijet transverse momentum scale. The Critical Pomeron is the resulting high-energy limit. 22 refs

FRP confined smart concrete/mortar

Science.gov (United States)

Xiao, Y.; Zhu, P. S.; Choi, K. G.; Wu, Y. T.; Huang, Z. Y.; Shan, B.

2006-03-01

In this study, fiber reinforced polymer (FRP) confined smart concrete/mortar sensors were invented and validated for significantly improved measurement range. Several trial mixes were made using cement mortar and micron-phase graphite powders at different mix proportions. Compressive loading tests were conducted on smart mortar cylinder specimens with or without FRP confinement. Two-probe method was used to detect the electrical resistance of the smart cement mortar specimens. Strong correlation was recognized between the stress and electric resistance of the smart mortar. The test results indicated that the FRP wrapping could significantly enlarge the range of such self-sensing property as a consequence of confinement.

Two-fluid model for locomotion under self-confinement

Science.gov (United States)

Reigh, Shang Yik; Lauga, Eric

2017-09-01

The bacterium Helicobacter pylori causes ulcers in the stomach of humans by invading mucus layers protecting epithelial cells. It does so by chemically changing the rheological properties of the mucus from a high-viscosity gel to a low-viscosity solution in which it may self-propel. We develop a two-fluid model for this process of swimming under self-generated confinement. We solve exactly for the flow and the locomotion speed of a spherical swimmer located in a spherically symmetric system of two Newtonian fluids whose boundary moves with the swimmer. We also treat separately the special case of an immobile outer fluid. In all cases, we characterize the flow fields, their spatial decay, and the impact of both the viscosity ratio and the degree of confinement on the locomotion speed of the model swimmer. The spatial decay of the flow retains the same power-law decay as for locomotion in a single fluid but with a decreased magnitude. Independent of the assumption chosen to characterize the impact of confinement on the actuation applied by the swimmer, its locomotion speed always decreases with an increase in the degree of confinement. Our modeling results suggest that a low-viscosity region of at least six times the effective swimmer size is required to lead to swimming with speeds similar to locomotion in an infinite fluid, corresponding to a region of size above ≈25 μ m for Helicobacter pylori.

Electron energy confinement in ELMO Bumpy Torus (EBT)

International Nuclear Information System (INIS)

Hiroe, S.; Haste, G.R.; Dandl, R.A.

1979-06-01

Using a calibrated, solid-state, soft x-ray detector, the electron temperature and density have been measured over a wide range of operating conditions of ELMO Bumpy Torus (EBT). The empirical relations of the temperature or the density to the microwave power and the ambient pressure have been determined. The toroidally stored energy has been observed to increase as the stored energy of the hot electron annulus increases. The energy confinement time has been obtained for various plasma parameters and has been found to agree with the neoclassical theory. The advantages of EBT collisionless scaling for fusion plasma confinement have been noted, i.e., n/sub e/tau/sub E/ increases as T/sub e/ 1 5 in the collisionless regime

Structure and Dynamics of Ionic Liquid [MMIM][Br] Confined in Hydrophobic and Hydrophilic Porous Matrices: A Molecular Dynamics Simulation Study.

Science.gov (United States)

Sharma, Anirban; Ghorai, Pradip Kr

2016-11-17

The effects of confinement on the structural and dynamical properties of the ionic liquid (IL) 1,3-dimethylimidazolium bromide ([MMIM][Br]) have been investigated by molecular dynamics simulations. We used zeolite faujasite (NaY) as a hydrophilic confinement and dealuminated faujasite (DAY) as a hydrophobic confinement. The presence of an extra framework cation, [Na + ], in NaY makes the host hydrophilic, whereas DAY, with no extra framework cation, is hydrophobic. Although both NaY and DAY have almost similar structures, the IL showed markedly different structural and dynamical properties in these confinements and in bulk. In the confinements, the cation-cation radial distribution function, which strongly depends on temperature, exhibits a layer-like structure, whereas in bulk, it shows a liquid-like structure that hardly depends on temperature. Although the interaction between [MMIM] + and Br - in DAY is stronger than that in both NaY and bulk, the strength of the interaction between them is almost invariant with temperature. Both [MMIM] + and Br - strongly interact with Na + of the host, and their interaction strongly depends on temperature, whereas the interaction of the IL with Si and O is very weak and invariant with temperature. In bulk, the self-diffusion coefficient, [D], of both [MMIM] + and Br - increases exponentially with temperature, and the D of the cation is slightly higher than that of the anion at all studied temperatures, whereas in the confinements, [MMIM] + moves much faster than Br - . For example, in the hydrophilic confinement, the D of the cation is 20-30 times higher than that of the anion. The D of both the ions decreases significantly in the confinements as compared to that in bulk. During diffusion, [MMIM] + diffuses closer to the inner surface in the hydrophilic confinement than that in the hydrophobic confinement. The diffusion pathway imperceptibly depends on temperature but strongly depends on the nature of the confinement. The self

Decay of orientational grating of weakly confined excitons in GaAs thin films

International Nuclear Information System (INIS)

Kojima, O.; Isu, T.; Ishi-Hayase, J.; Kanno, A.; Katouf, R.; Sasaki, M.; Tsuchiya, M.

2008-01-01

We report the dynamical properties of the exciton orientation in GaAs thin films using the orientational grating (OG) technique. From the results of excitation-power dependence of OG signal, we confirmed that the OG signal comes from the optical nonlinearity of weakly confined excitons. In addition, the OG-decay time decreases with an increase of excitation power due to exciton-exciton interaction, and the shortest decay time is below 1 ps. Our results may imply the potential application of optical nonlinearity of weakly confined exciton to ultrafast switching devices operating at 1 Tbit/s

Thermal stability of a thermonuclear plasma for different confinement scaling laws

International Nuclear Information System (INIS)

Johner, J.

1985-10-01

The thermal stability of the ignition curve is investigated using a simple OD model for a temperature dependent energy confinement time (tausub(E) is proportional to 1/Tsup(γ)). The stability limit in the (ntausub(E),T) plane is also calculated for a plasma with external heating. The degradation of confinement time with increasing temperature is found to be favourable for divergence temperature and minimum temperature for stable ignition. It also decreases the external power per unit volume necessary to reach divergence. On the contrary, it is extremely unfavourable for the required μsub(E) for divergence and ignition. Detailed results are given for the special case of the Kaye-Goldston scaling (γ=1.38)

Regime of very high confinement in the boronized DIII-D tokamak

International Nuclear Information System (INIS)

Jackson, G.L.; Winter, J.; Taylor, T.S.; Burrell, K.H.; DeBoo, J.C.; Greenfield, C.M.; Groebner, R.J.; Hodapp, T.; Holtrop, K.; Lazarus, E.A.; Lao, L.L.; Lippmann, S.I.; Osborne, T.H.; Petrie, T.W.; Phillips, J.; James, R.; Schissel, D.P.; Strait, E.J.; Turnbull, A.D.; West, W.P.; DIII-D Team

1991-01-01

Following boronization, tokamak discharges in DIII-D have been obtained with confinement times up to a factor of 3.5 above the ITER89-P L-mode scaling and 1.8 times greater than the DIII-D/JET H-mode scaling relation. Very high confinement phases are characterized by relatively high central density with n e (0)∼1x10 20 m -3 , and central ion temperatures up to 13.6 keV at moderate plasma currents (1.6 MA) and heating powers (12.5--15.3 MW). These discharges exhibit a low fraction of radiated power, P≤25%, Z eff (0) close to unity, and lower impurity influxes than comparable DIII-D discharges before boronization

Progress in application of hybrid numerical simulation methods to magnetic confinement systems. Annual report

International Nuclear Information System (INIS)

Morse, R.L.

1979-06-01

Hybrid codes have been developed to simulate high density, high β confined plasmas. The major areas of application have been end plugging and heating of linear confinement systems. In particular, significant progress has been made in understanding the role of line and recombination radiation in recent experiments which showed large increases in energy confinement times from the use of solid end plugs. Another accomplishment is the conception and theoretical analysis of an efficient, low frequency, axial heating method which we believe could significantly increase the attractiveness of linear systems as reactors

Tokamak-like confinement at high beta and low field in the reversed field pinch

International Nuclear Information System (INIS)

Sarff, J S; Anderson, J K; Biewer, T M; Brower, D L; Chapman, B E; Chattopadhyay, P K; Craig, D; Deng, B; Hartog, D J Den; Ding, W X; Fiksel, G; Forest, C B; Goetz, J A; O'Connell, R; Prager, S C; Thomas, M A

2003-01-01

For several reasons, improved-confinement achieved in the reversed field pinch (RFP) during the last few years can be characterized as 'tokamak-like'. Historically, RFP plasmas have had relatively poor confinement due to tearing instability which causes magnetic stochasticity and enhanced transport. Tearing reduction is achieved through modification of the inductive current drive, which dramatically improves confinement. The electron temperature increases to >1 keV and the electron heat diffusivity decreases to approx. 5 m 2 s -1 , comparable with the transport level expected in a tokamak plasma of the same size and current. This corresponds to a 10-fold increase in global energy confinement. Runaway electrons are confined, and Fokker-Planck modelling of the electron distribution reveals that the diffusion at high energy is independent of the parallel velocity, uncharacteristic of stochastic transport. Improved-confinement occurs simultaneously with increased beta approx. 15%, while maintaining a magnetic field strength ten times weaker than a comparable tokamak. Measurements of the current, magnetic, and electric field profiles show that a simple Ohm's Law applies to this RFP sustained without dynamo relaxation

Confinement of quarks

International Nuclear Information System (INIS)

Nambu, J.

1978-01-01

Three quark models of hadron structure, which suggest an explanation of quarks confinement mechanism in hadrons are considered. Quark classifications, quark flawors and colours, symmetry model of hadron structure based on the colour theory of strong interaction are discussed. Diagrams of colour combinations of quarks and antiquarks, exchange of gluons, binding quarks in hadron. Quark confinement models based on the field theory, string model rotating and bag model are discussed. Diagrams of the colour charge distribution explaining the phenomena of infrared ''slavery'' and ultraviolet ''freedom'' are given. The models considered explain but some quark properties, creating prerequisites for the development of the consequent theory of hadron structure

Analysis of the neutron time-of-flight spectra from inertial confinement fusion experiments

Energy Technology Data Exchange (ETDEWEB)

Hatarik, R., E-mail: hatarik1@llnl.gov; Sayre, D. B.; Caggiano, J. A.; Phillips, T.; Eckart, M. J.; Bond, E. J.; Cerjan, C.; Grim, G. P.; Hartouni, E. P.; Mcnaney, J. M.; Munro, D. H. [Lawrence Livermore National Laboratory, Livermore, California 94550 (United States); Knauer, J. P. [Laboratory for Laser Energetics, University of Rochester, Rochester, New York 14623 (United States)

2015-11-14

Neutron time-of-flight diagnostics have long been used to characterize the neutron spectrum produced by inertial confinement fusion experiments. The primary diagnostic goals are to extract the d + t → n + α (DT) and d + d → n + {sup 3}He (DD) neutron yields and peak widths, and the amount DT scattering relative to its unscattered yield, also known as the down-scatter ratio (DSR). These quantities are used to infer yield weighted plasma conditions, such as ion temperature (T{sub ion}) and cold fuel areal density. We report on novel methodologies used to determine neutron yield, apparent T{sub ion}, and DSR. These methods invoke a single temperature, static fluid model to describe the neutron peaks from DD and DT reactions and a spline description of the DT spectrum to determine the DSR. Both measurements are performed using a forward modeling technique that includes corrections for line-of-sight attenuation and impulse response of the detection system. These methods produce typical uncertainties for DT T{sub ion} of 250 eV, 7% for DSR, and 9% for the DT neutron yield. For the DD values, the uncertainties are 290 eV for T{sub ion} and 10% for the neutron yield.

Dimensional crossover in fluids under nanometer-scale confinement.

Science.gov (United States)

Das, Amit; Chakrabarti, J

2012-05-01

Several earlier studies have shown signatures of crossover in various static and dynamics properties of a confined fluid when the confining dimension decreases to about a nanometer. The density fluctuations govern the majority of such properties of a fluid. Here, we illustrate the crossover in density fluctuation in a confined fluid, to provide a generic understanding of confinement-induced crossover of fluid properties, using computer simulations. The crossover can be understood as a manifestation of changes in the long-wavelength behavior of fluctuation in density due to geometrical constraints. We further show that the confining potential significantly affects the crossover behavior.

Plasma confinement in a magnetic dipole

International Nuclear Information System (INIS)

Kesner, J.; Bromberg, L.; Garnier, D.; Mauel, M.

1999-01-01

A dipole fusion confinement device is stable to MHD interchange and ballooning modes when the pressure profile is sufficiently gentle. The plasma can be confined at high beta, is steady state and disruption free. Theory indicates that when the pressure gradient is sufficiently gentle to satisfy MHD requirements drift waves will also be stable. The dipole approach is particularly applicable for advanced fuels. A new experimental facility is presently being built to test the stability and transport properties of a dipole-confined plasma. (author)

Plasma confinement in a magnetic dipole

International Nuclear Information System (INIS)

Kesner, J.; Bromberg, L.; Garnier, D.; Mauel, M.

2001-01-01

A dipole fusion confinement device is stable to MHD interchange and ballooning modes when the pressure profile is sufficiently gentle. The plasma can be confined at high beta, is steady state and disruption free. Theory indicates that when the pressure gradient is sufficiently gentle to satisfy MHD requirements drift waves will also be stable. The dipole approach is particularly applicable for advanced fuels. A new experimental facility is presently being built to test the stability and transport properties of a dipole-confined plasma. (author)

A Study of Confined Helium Atom

International Nuclear Information System (INIS)

Xie Wenfang

2007-01-01

The helium atom confined by a spherical parabolic potential well is studied employing the adiabatic hyperspherical approach method. Total energies of the ground and three low-excited states are obtained as a function of the confined potential radii. We find that the energies of a spherical parabolic potential well are in good agreement with those of an impenetrable spherical box for the larger confined potential radius. We find also that the confinement may cause accidental degeneracies between levels with different low-excited states and the inversion of the energy values. The results for the three-dimensional spherical potential well and the two-dimensional disc-like potential well are compared with each other. We find that the energy difference between states in a two-dimensional parabolic potential is also obviously larger than the corresponding levels for a spherical parabolic potential.

Topology of polymer chains under nanoscale confinement.

Science.gov (United States)

Satarifard, Vahid; Heidari, Maziar; Mashaghi, Samaneh; Tans, Sander J; Ejtehadi, Mohammad Reza; Mashaghi, Alireza

2017-08-24

Spatial confinement limits the conformational space accessible to biomolecules but the implications for bimolecular topology are not yet known. Folded linear biopolymers can be seen as molecular circuits formed by intramolecular contacts. The pairwise arrangement of intra-chain contacts can be categorized as parallel, series or cross, and has been identified as a topological property. Using molecular dynamics simulations, we determine the contact order distributions and topological circuits of short semi-flexible linear and ring polymer chains with a persistence length of l p under a spherical confinement of radius R c . At low values of l p /R c , the entropy of the linear chain leads to the formation of independent contacts along the chain and accordingly, increases the fraction of series topology with respect to other topologies. However, at high l p /R c , the fraction of cross and parallel topologies are enhanced in the chain topological circuits with cross becoming predominant. At an intermediate confining regime, we identify a critical value of l p /R c , at which all topological states have equal probability. Confinement thus equalizes the probability of more complex cross and parallel topologies to the level of the more simple, non-cooperative series topology. Moreover, our topology analysis reveals distinct behaviours for ring- and linear polymers under weak confinement; however, we find no difference between ring- and linear polymers under strong confinement. Under weak confinement, ring polymers adopt parallel and series topologies with equal likelihood, while linear polymers show a higher tendency for series arrangement. The radial distribution analysis of the topology reveals a non-uniform effect of confinement on the topology of polymer chains, thereby imposing more pronounced effects on the core region than on the confinement surface. Additionally, our results reveal that over a wide range of confining radii, loops arranged in parallel and cross

A GASFLOW analysis of a steam explosion accident in a typical light-water reactor confinement building

International Nuclear Information System (INIS)

Travis, J.R.; Wilson, T.L.; Spore, J.W.; Lam, K.L.; Rao, D.V.

1994-01-01

Steam over-pressurization resulting from ex-vessel steam explosion (fuel-coolant interaction) may pose a serious challenge to the integrity of a typical light-water reactor confinement building. If the steam generation rate exceeds the removal capacity of the Airborne Activity Confinement System, confinement overpressurization occurs. Thus, there is a large potential for an uncontrolled and unfiltered release of fission products from the confinement atmosphere to the environment at the time of the steam explosion. The GASFLOW computer code was used to analyze the effects of a hypothetical steam explosion and the transport of steam and hydrogen throughout a typical light-water reactor confinement building. The effects of rapid pressurization and the resulting forces on the internal structures and the heat exchanger service bay hatch covers were calculated. Pressurization of the ventilation system and the potential damage to the ventilation fans and high-efficiency particulate air filters were assessed. Because of buoyancy forces and the calculated confinement velocity field, the hydrogen diffuses and mixes in the confinement atmosphere but tends to be transported to its upper region. (author). 2 refs., 14 figs

A GASFLOW analysis of a steam explosion accident in a typical light-water reactor confinement building

International Nuclear Information System (INIS)

Travis, J.R.; Wilson, T.L.; Spore, J.W.; Lam, K.L.; Rao, D.V.

1994-01-01

Steam over-pressurization resulting from ex-vessel steam explosion (fuel-coolant interaction) may pose a serious challenge to the integrity of a typical light-water reactor confinement building. If the steam generation rate exceeds the removal capacity of the Airborne Activity Confinement System, confinement over pressurization occurs. Thus, there is a large potential for an uncontrolled and unfiltered release of fission products from the confinement atmosphere to the environment at the time of the steam explosion. The GASFLOW computer code was used to analyze the effects of a hypothetical steam explosion and the transport of steam and hydrogen throughout a typical light-water reactor confinement building. The effects of rapid pressurization and the resulting forces on the internal structures and the heat exchanger service bay hatch covers were calculated. Pressurization of the ventilation system and the potential damage to the ventilation fans and high-efficiency particulate air filters were assessed. Because of buoyancy forces and the calculated confinement velocity field, the hydrogen diffuses and mixes in the confinement atmosphere but tends to be transported to its upper region

Quark confinement in a constituent quark model

International Nuclear Information System (INIS)

Langfeld, K.; Rho, M.

1995-01-01

On the level of an effective quark theory, we define confinement by the absence of quark anti-quark thresholds in correlation function. We then propose a confining Nambu-Jona-Lasinio-type model. The confinement is implemented in analogy to Anderson localization in condensed matter systems. We study the model's phase structure as well as its behavior under extreme conditions, i.e. high temperature and/or high density

Infrared slavery and quark confinement

CERN Document Server

Alabiso, C

1976-01-01

The question is considered of whether the so-called infrared slavery mechanism as, e.g., being manifest in non-Abelian gauge theories, necessarily confines quarks. Making a specific ansatz for the long- range forces, the Schwinger-Dyson equation is solved for the quark Green function. Besides having a confining solution, it appears that quarks may by-pass the long-range forces and be produced. (20 refs).

Infrared slavery and quark confinement

International Nuclear Information System (INIS)

Alabiso, C.; Schierholz, G.

1976-01-01

The question of whether the so-called infrared slavery mechanism as, e.g., being manifest in non-Abelian gauge theories, necessarily confines quarks is posed. Making a specific ansatz for the long-range forces, the Schwinger-Dyson equation is solved for the quark Green function. Besides having a confining solution, it appears that quarks may by-pass the long-range forces and be produced. (Auth.)

["Tied down"--the process of becoming bedridden through gradual local confinement].

Science.gov (United States)

Zegelin, Angelika

2005-10-01

To be bedridden is a common phenomenon in nursing. However, there is no solid base of knowledge on reasons, types, development of and coping with this situation. The concept of being bedridden is applied in an arbitrary manner and the state of being bedridden is far from being clearly defined. A literature review revealed that only pathophysiological effects of this state are sufficiently explained. The aim of this study was to gain knowledge of the development of being confined to bed. Thirty-two interviews with elderly, bedridden people (nineteen women, thirteen men) were conducted. They were asked about their perspective on and their experience of the development of being confined to bed. Half of the interviewees lived in a nursing home, the others were cared for at home. Data collection and analysis were performed by using a Grounded Theory approach as developed by Strauss and Corbin. "Gradual local fixation" was identified as the core category. Becoming bedridden is a slow process by which the person is increasingly confined to one location. This development is related to an increasing need for support and to negative consequences such as a pathology of immobility, narrowing of interests, and loss of time. These consequences again are responsible for a downward spiral development. This study reveals phases of development and a range of factors influencing them. Many of these factors arise from the person and his/her interactional behaviour in the circumstances, other influences are structural factors such as external pressure caused by time constraints of professional nursing services or unfavourable arrangements of furniture. A lot of factors of being confined to bed are changeable. Long periods of being bedridden can be prevented in many cases, if early warning signs are being recognized and preventive measures are taken in time.

Numerical Investigations On The Seismic Behaviour Of Confined Masonry Walls

International Nuclear Information System (INIS)

Calderini, Chiara; Cattari, Serena; Lagomarsino, Sergio

2008-01-01

In the last century, severe earthquakes highlighted the seismic vulnerability of unreinforced masonry buildings. Many technological innovations have been introduced in time in order to improve resistance, ductility, and dissipation properties of this type of constructions. The most widely diffused are reinforced masonry and confined masonry. Damage observation of recent earthquakes demonstrated the effectiveness of the response of confined masonry structures to seismic actions. In general, in this type of structures, reinforced concrete beams and columns are not main structural elements, however, they have the following functions: to confine masonry in order to increase its ductility; to bear tensile stresses derived from bending; to contrast the out-of-plane overturning of masonry panels. It is well evident that these functions are as much effectively performed as the connection between masonry and reinforced concrete elements is good (for example by mean of local interlocking or reinforcements). Confined masonry structures have been extensively studied in the last decades both from a theoretical point of view and by experimental tests Aims of this paper is to give a contribution to the understanding of the seismic behaviour of confined masonry walls by means of numerical parametrical analyses. There latter are performed by mean of the finite element method; a nonlinear anisotropic constitutive law recently developed for masonry is adopted. Comparison with available experimental results are carried out in order to validate the results. A comparison between the resistance obtained from the numerical analyses and the prevision provided by simplified resistance criteria proposed in literature and in codes is finally provided

Generation and confinement of hot ions and electrons in a reversed-field pinch plasma

International Nuclear Information System (INIS)

Chapman, B E; Almagri, A F; Anderson, J K; Caspary, K J; Clayton, D J; Den Hartog, D J; Ennis, D A; Fiksel, G; Gangadhara, S; Kumar, S; Magee, R M; O'Connell, R; Parke, E; Prager, S C; Reusch, J A; Sarff, J S; Stephens, H D; Brower, D L; Ding, W X; Craig, D

2010-01-01

By manipulating magnetic reconnection in Madison Symmetric Torus (MST) discharges, we have generated and confined for the first time a reversed-field pinch (RFP) plasma with an ion temperature >1 keV and an electron temperature of 2 keV. This is achieved at a toroidal plasma current of about 0.5 MA, approaching MST's present maximum. The manipulation begins with intensification of discrete magnetic reconnection events, causing the ion temperature to increase to several kiloelectronvolts. The reconnection is then quickly suppressed with inductive current profile control, leading to capture of a portion of the added ion heat with improved ion energy confinement. Electron energy confinement is simultaneously improved, leading to a rapid ohmically driven increase in the electron temperature. A steep electron temperature gradient emerges in the outer region of the plasma, with a local thermal diffusivity of about 2 m 2 s -1 . The global energy confinement time reaches 12 ms, the largest value yet achieved in the RFP and which is roughly comparable to the H-mode scaling prediction for a tokamak with the same plasma current, density, heating power, size and shape.

Report on the combined meeting of the core confinement and internal transport barrier expert group, confinement database and modeling expert group and edge pedestal expert group, 12-16 April 1999, Garching

International Nuclear Information System (INIS)

Janeschitz, G.; Connor, J.W.; Cordey, G.; Kardaun, O.; Mukhovatov, V.; Stambaugh, R.; Ryter, F.; Wakatani, M.

1999-01-01

This contribution to the ITER EDA Newsletter reports on the combined meeting of the core confinement and internal transport barrier expert group, confinement database and modeling expert group and edge pedestal expert group in Garching, Germany. This is the first workshop of its kind after the re-organisation of the expert groups. The new scheme of the meetings, namely to permit more interaction between groups by arranging them at the same time and location turned out to be very successful. The main issues discussed were for the Confinement Database: merging of edge pedestal and confinement data, improvement of the density- and magnetic shape parameters, addition of new dedicated threshold data, the effect of different divertors in JET; for the H-Mode Power Threshold Database: assembly of a new version of the database with about 650 time points from 10 tokamaks; for the 1-D Modelling Workshop: management of the database after the re-organisation of the Joint Central Team an ongoing efforts in plasma transport modelling; for the newly formed pedestal group: issues of the H-mode shear layer at the plasma edge. There was also an executive summary given of a recent USA workshop on internal transport barriers and regimes with weak or negative magnetic shear

Correlations In Confined Quantum Plasmas

International Nuclear Information System (INIS)

Dufty, J.W.

2012-01-01

This is the final report for the project 'Correlations in Confined Quantum Plasmas', NSF-DOE Partnership Grant DE FG02 07ER54946, 8/1/2007 - 7/30/2010. The research was performed in collaboration with a group at Christian Albrechts University (CAU), Kiel, Germany. That collaboration, almost 15 years old, was formalized during the past four years under this NSF-DOE Partnership Grant to support graduate students at the two institutions and to facilitate frequent exchange visits. The research was focused on exploring the frontiers of charged particle physics evolving from new experimental access to unusual states associated with confinement. Particular attention was paid to combined effects of quantum mechanics and confinement. A suite of analytical and numerical tools tailored to the specific inquiry has been developed and employed

Cylindrical fabric-confined soil structures

Science.gov (United States)

Harrison, Richard A.

A cylindrical fabric-soil structural concept for implementation on the moon and Mars which provides many advantages is proposed. The most efficient use of fabric is to fashion it into cylindrical tubes, creating cylindrical fabric-confined soil structures. The length, diameter, and curvature of the tubes will depend on the intended application. The cylindrical hoop forces provide radial confinement while end caps provide axial confinement. One of the ends is designed to allow passage of the soil into the fabric tube before sealing. Transportation requirements are reduced due to the low mass and volume of the fabric. Construction requirements are reduced due to the self-erection capability via the pneumatic exoskeleton. Maintenance requirements are reduced due to the passive nature of the concept. The structure's natural ductility is well suited for any seismic activity.

Reinforced confinement in a nuclear reactor

International Nuclear Information System (INIS)

Norman, H.

1988-01-01

The present invention concerns a nuclear reactor containing a reactor core, a swimming pool space that is filled and pressurized with a neutron-absorbing solution, a reactor tank, at least one heat exchanger, at least one inlet line, at least one return line and at least one circulation pump, where the said reactor tank is confined in the said swimming pool space and designed to be cooled with the aid of relatively pure water, which is fed by means of the said at least one circulating pump to the said reactor tank from the said heat exchanger via the said at least one inlet line and is returned to the heat exchanger via the said at least one return line. The problem that is to be solved by the invention is to design a reactor of the above type in such a way that a complete confinement of the primary circuit of the reactor is achieved at relatively low extra cost. This problem is solved by providing the reactor with a special confinement space that confines the heat exchanger, but not the reactor tank, with the confinement space and the swimming pool space being fashioned in the same concrete body

Transport increase and confinement degradation caused by MARFE

Science.gov (United States)

Shi, Peng; Zhuang, Ge; Gao, Li; Zhou, Yinan

2017-10-01

Recently, the MARFE phenomenon associated with high density plasmas has been observed on J-TEXT Ohmically heated discharges. The MARFE on J-TEXT is charactered by the poloidally local region at high field side (HFS) edge with high density and strong radiation. At the almost same time of MARFE appearance, the density peaking factor and sawtooth oscillation reach maximum and decrease with density increasing, infers that the plasma confinement is saturated. By analyzing the far-forward scattering signals from polarimeter-interferometer, it is found that the local radial density turbulence at high field edge increases significantly after MARFE onset. It is inferred that the local particle transport at MARFE affected region (HFS edge) is enhanced. The enhancement of radial transport at MARFE affected region is considered as the possible reason for confinement saturation on J-TEXT. Furthermore, the trapped electron mode (TEM) with quasi-coherent characteristics is measured by far-forward scattering. The TEMs are always observed in plasmas with low density, and disappear after the plasma density exceeds a threshold. The density threshold of TEM disappearance is consistent with the density threshold of MARFE onset. The evolution of turbulences affirms that the MARFE may be the cause of energy confinement transition from LOC to SOC.

Exceptional confinement in G(2) gauge theory

International Nuclear Information System (INIS)

Holland, K.; Minkowski, P.; Pepe, M.; Wiese, U.-J.

2003-01-01

We study theories with the exceptional gauge group G(2). The 14 adjoint 'gluons' of a G(2) gauge theory transform as {3}, {3-bar} and {8} under the subgroup SU(3), and hence have the color quantum numbers of ordinary quarks, anti-quarks and gluons in QCD. Since G(2) has a trivial center, a 'quark' in the {7} representation of G(2) can be screened by 'gluons'. As a result, in G(2) Yang-Mills theory the string between a pair of static 'quarks' can break. In G(2) QCD there is a hybrid consisting of one 'quark' and three 'gluons'. In supersymmetric G(2) Yang-Mills theory with a {14} Majorana 'gluino' the chiral symmetry is Z(4) χ . Chiral symmetry breaking gives rise to distinct confined phases separated by confined-confined domain walls. A scalar Higgs field in the {7} representation breaks G(2) to SU(3) and allows us to interpolate between theories with exceptional and ordinary confinement. We also present strong coupling lattice calculations that reveal basic features of G(2) confinement. Just as in QCD, where dynamical quarks break the Z(3) symmetry explicitly, G(2) gauge theories confine even without a center. However, there is not necessarily a deconfinement phase transition at finite temperature

Measurement of dynamic viscoelasticity of confined lubricant by using oscillating optical fiber probe

International Nuclear Information System (INIS)

Itoh, S; Fukuzawa, K; Hamamoto, Y; Zhang, H

2007-01-01

When a liquid is confined in molecularly narrow gaps, it shows characteristic viscoelasticity such as enhanced viscosity or prolonged relaxation time. In order to investigate the dynamic viscoelasticity of the confined liquid, we developed a new shear force measuring method that uses a ball-ended optical fiber as a shearing probe. Our method can measure the shear force of 0.1 nN order with the oscillation frequency of up to 10 kHz. In addition, the gap that confines the liquid can be set at any constant value ranging from 10 μm to 0.1 nm. In this study, we measured the gap dependence of viscoelasticity of confined liquid lubricants. The gap ranged from 200 nm to a few nm. The tested lubricant was Fomblin Z03 and Zdo14000. A magnetic disk was used as the solid substrate. Oscillation frequency was set at 800 Hz. The experiment showed the viscosity of both Z03 and Zdo14000 gradually increased as the confining gap decreased. The gap width where the viscosity increase started was wider than 100 nm, which is dozens of times larger than the gyration diameter of lubricant molecules. Although Z03 and Zdo14000 have negligibly small elasticity in a bulk state, elasticity suddenly appeared at gaps less than about 8 nm with Zdo14000, and at gaps less than about 4 nm with Z03. Stronger affinity of Zdo14000 molecules to the solid substrate could cause the wider gap width of elasticity appearance

The impact of confinement scaling on ITER [International Thermonuclear Experimental Reactor] parameters

International Nuclear Information System (INIS)

Reid, R.L.; Galambos, J.D.; Peng, Y.K.M.

1988-09-01

Energy confinement scaling is a major concern in the design of the International Thermonuclear Experimental Reactor (ITER). The existing database for tokamaks can be fitted with a number of different confinement scaling expressions that have similar degrees of approximation. These scaling laws predict confinement times for ITER that vary by over an order of magnitude. The uncertainties in the form and magnitude of these scaling laws must be substantially reduced before the plasma performance of ITER can be predicted with adequate reliability. The TETRA systems code is used to calculate the dependence of major ITER parameters on the scaling laws currently in use. Design constraints of interest in the present phase of ITER consideration are used, and the minimum-cost devices arising from these constraints are reviewed. 9 refs., 13 figs., 4 tabs

Energy Confinement of both Ohmic and LHW Plasma on EAST

International Nuclear Information System (INIS)

Yang Yao; Gao Xiang

2011-01-01

Study on the characters of energy confinement in both Ohmic and lower hybrid wave (LHW) discharges on EAST is conducted and the linear Ohmic confinement (LOC), saturated ohmic confinement (SOC) and improved Ohmic confinement (IOC) regimes are investigated in this paper. It is observed that an improved confinement mode characterized by both a drop of D α line intensity and an increase in line average density can be triggered by a gas puffing pulse. (magnetically confined plasma)

Monopole current dynamics and color confinement

International Nuclear Information System (INIS)

Ichie, H.; Suganuma, H.; Tanaka, A.

1998-01-01

Color confinement can be understood by the dual Higgs theory, where monopole condensation leads to the exclusion of the electric flux from the QCD vacuum. We study the role of the monopole for color confinement by investigating the monopole current system. When the self-energy of the monopole current is small enough, long and complicated monopole world-lines appear, which is a signal of monopole condensation. In the dense monopole system, the Wilson loop obeys the area-law, and the string tension and the monopole density have similar behavior as the function of the self-energy, which seems that monopole condensation leads to color confinement. On the long-distance physics, the monopole current system almost reproduces essential features of confinement properties in lattice QCD. In the short-distance physics, however, the monopole-current theory would become nonlocal and complicated due to the monopole size effect. This monopole size would provide a critical scale of QCD in terms of the dual Higgs mechanism. (orig.)

Extended BRS algebra and color confinement

International Nuclear Information System (INIS)

Shintani, Meiun.

1984-02-01

We examine the color confinement scheme and its realizations proposed by Kugo and Ojima. Using the Nakanishi's theorem, we obtain a representation of the extended BRS algebra compatible with the so-called K-O condition of their confinement criteria. However, it turns out that the representation is not physically acceptable, and thus their scheme lacks self-consistency at the level of realizations. We also clarify what kind of ghost structures are suggested by the well-definedness or ill-definedness of the charge operator Nsup(a) constituting a part of the global color charge operator. It is shown that there are four possible cancellation mechanisms of ghosts. In particular, it turns out that the octet of ghosts suggested by Nishijima in his confinement theory arises from the well-definedness of the Nsup(a) charge, whereas the elementary quartet arises from the ill-definedness of the Nsup(a). Moreover, from the octet structures, we deduce the confinement condition which replaces the K-O condition. (author)

Physics of inertial confinement pellets

International Nuclear Information System (INIS)

Mead, W.C.

1979-01-01

An overview of inertial confinement fusion pellet physics is given. A discussion is presented of current estimated ICF driver requirements and a couple of pellet examples. The physics of driver/plasma coupling for two drivers which are being considered, namely a laser driver and a heavy ion accelerator driver, is described. Progress towards inertial confinement fusion that has been made using laser drivers in target experiments to date is discussed

Climate conditions in bedded confinement buildings

Science.gov (United States)

Confinement buildings are utilized for finishing cattle to allow more efficient collection of animal waste and to buffer animals against adverse climatic conditions. Environmental data were obtained from a 29 m wide x 318 m long bedded confinement building with the long axis oriented east to west. T...

Quark propagators and correlators in a confining vacuum

International Nuclear Information System (INIS)

Simonov, Yu.A.

1987-01-01

Quark propagators, quark-antiquark Green functions and photon selfenergy operator Π (2) (k) are considered in the background (anti)selfdual field. The cases of a homogeneous selfdual field in d=4 and magnetic field in d=2 are studied in detail. Isolated quarks and quark-antiquark pairs are shown to be confined in those cases with the quadratic form of confining potential. In the space filled with domains of the homogeneous field with random directions the confining potential is of linear form, and the colorless qq-bar pair is not confined

Plasma confinement system and methods for use

Science.gov (United States)

Jarboe, Thomas R.; Sutherland, Derek

2017-09-05

A plasma confinement system is provided that includes a confinement chamber that includes one or more enclosures of respective helicity injectors. The one or more enclosures are coupled to ports at an outer radius of the confinement chamber. The system further includes one or more conductive coils aligned substantially parallel to the one or more enclosures and a further set of one or more conductive coils respectively surrounding portions of the one or more enclosures. Currents may be provided to the sets of conductive coils to energize a gas within the confinement chamber into a plasma. Further, a heat-exchange system is provided that includes an inner wall, an intermediate wall, an outer wall, and pipe sections configured to carry coolant through cavities formed by the walls.

Radiofrequency-heated enhanced confinement modes in the Alcator C-Mod tokamak

International Nuclear Information System (INIS)

Takase, Y.; Boivin, R.L.; Bombarda, F.; Bonoli, P.T.; Christensen, C.; Fiore, C.; Garnier, D.; Goetz, J.A.; Golovato, S.N.; Granetz, R.; Greenwald, M.; Horne, S.F.; Hubbard, A.; Hutchinson, I.H.; Irby, J.; LaBombard, B.; Lipschultz, B.; Marmar, E.; May, M.; Mazurenko, A.; McCracken, G.; OShea, P.; Porkolab, M.; Reardon, J.; Rice, J.; Rost, C.; Schachter, J.; Snipes, J.A.; Stek, P.; Terry, J.; Watterson, R.; Welch, B.; Wolfe, S.

1997-01-01

Enhanced confinement modes up to a toroidal field of B T =8T have been studied with up to 3.5 MW of radiofrequency (rf) heating power in the ion cyclotron range of frequencies (ICRF) at 80 MHz. H-mode is observed when the edge temperature exceeds a threshold value. The high confinement mode (H-mode) with higher confinement enhancement factors (H) and longer duration became possible after boronization by reducing the radiated power from the main plasma. A quasi-steady state with high confinement (H=2.0), high normalized beta (β N =1.5), low radiated power fraction (P rad main /P loss =0.3), and low effective charge (Z eff =1.5) has been obtained in Enhanced D α H-mode. This type of H-mode has enhanced levels of continuous D α emission and very little or no edge localized mode (ELM) activity, and reduced core particle confinement time relative to ELM-free H-mode. The pellet enhanced performance (PEP) mode is obtained by combining core fueling with pellet injection and core heating. A highly peaked pressure profile with a central value of 8 atmospheres was observed. The steep pressure gradient drives off-axis bootstrap current, resulting in a shear reversed safety factor (q) profile. Suppression of sawteeth appears to be important in maintaining the highly peaked pressure profile. Lithium pellets were found to be more effective than deuterium pellets in raising q 0 . copyright 1997 American Institute of Physics

A compliant mechanism for inspecting extremely confined spaces

Science.gov (United States)

Mascareñas, David; Moreu, Fernando; Cantu, Precious; Shields, Daniel; Wadden, Jack; El Hadedy, Mohamed; Farrar, Charles

2017-11-01

We present a novel, compliant mechanism that provides the capability to navigate extremely confined spaces for the purpose of infrastructure inspection. Extremely confined spaces are commonly encountered during infrastructure inspection. Examples of such spaces can include pipes, conduits, and ventilation ducts. Often these infrastructure features go uninspected simply because there is no viable way to access their interior. In addition, it is not uncommon for extremely confined spaces to possess a maze-like architecture that must be selectively navigated in order to properly perform an inspection. Efforts by the imaging sensor community have resulted in the development of imaging sensors on the millimeter length scale. Due to their compact size, they are able to inspect many extremely confined spaces of interest, however, the means to deliver these sensors to the proper location to obtain the desired images are lacking. To address this problem, we draw inspiration from the field of endoscopic surgery. Specifically we consider the work that has already been done to create long flexible needles that are capable of being steered through the human body. These devices are typically referred to as ‘steerable needles.’ Steerable needle technology is not directly applicable to the problem of navigating maze-like arrangements of extremely confined spaces, but it does provide guidance on how this problem should be approached. Specifically, the super-elastic nitinol tubing material that allows steerable needles to operate is also appropriate for the problem of navigating maze-like arrangements of extremely confined spaces. Furthermore, the portion of the mechanism that enters the extremely confined space is completely mechanical in nature. The mechanical nature of the device is an advantage when the extremely confined space features environmental hazards such as radiation that could degrade an electromechanically operated mechanism. Here, we present a compliant mechanism

Density and Phase State of a Confined Nonpolar Fluid

Science.gov (United States)

Kienle, Daniel F.; Kuhl, Tonya L.

2016-07-01

Measurements of the mean refractive index of a spherelike nonpolar fluid, octamethytetracylclosiloxane (OMCTS), confined between mica sheets, demonstrate direct and conclusive experimental evidence of the absence of a first-order liquid-to-solid phase transition in the fluid when confined, which has been suggested to occur from previous experimental and simulation results. The results also show that the density remains constant throughout confinement, and that the fluid is incompressible. This, along with the observation of very large increases (many orders of magnitude) in viscosity during confinement from the literature, demonstrate that the molecular motion is limited by the confining wall and not the molecular packing. In addition, the recently developed refractive index profile correction method, which enables the structural perturbation inherent at a solid-liquid interface and that of a liquid in confinement to be determined independently, was used to show that there was no measurable excess or depleted mass of OMCTS near the mica surface in bulk films or confined films of only two molecular layers.

Fuel and helium confinement in fusion reactors

International Nuclear Information System (INIS)

Houlberg, W.A.; Attenberger, S.E.

1993-01-01

An expanded macroscopic model for particle confinement is used to investigate both fuel and helium confinement in reactor plasmas. The authors illustrate the relative effects of external sources of fuel, divertor pumping, and wall and divertory recycle on core, edge and scrape-off layer densities by using separate particle confinement times for open-quote core close-quote fueling (deep pellet or beam penetration, τ c ), open-quote shallow close-quote fueling (shallow pellet penetration or neutral atoms that penetrate the scrape-off layer, τ s ) and fueling in the scrape-off layer (τ sol ). Because τ s is determined by the parallel flow velocity and characteristic distance to the divertor plate, it can be orders of magnitude lower than either τ c or τ sol . A dense scrape-off region, desirable for reduced divertor erosion, leads to a high fraction of the recycled neutrals being ionized in the scrape-off region and poor core fueling efficiency. The overall fueling efficiency can then be dramatically improved with either shallow or deep auxillary fueling. Helium recycle is nearly always coupled to the scrape-off region and does not lead to strong core accumulation unless the helium pumping efficiency is much less than the fuel pumping efficiency, or the plasma preferentially retains helium over hydrogenic ions. Differences between the results of this model, single-τ p macroscopic models, and 1-D and 2-D models are discussed in terms of assumptions and boundary conditions

Diffusion of Finite-Size Particles in Confined Geometries

KAUST Repository

Bruna, Maria; Chapman, S. Jonathan

2013-01-01

The diffusion of finite-size hard-core interacting particles in two- or three-dimensional confined domains is considered in the limit that the confinement dimensions become comparable to the particle's dimensions. The result is a nonlinear diffusion equation for the one-particle probability density function, with an overall collective diffusion that depends on both the excluded-volume and the narrow confinement. By including both these effects, the equation is able to interpolate between severe confinement (for example, single-file diffusion) and unconfined diffusion. Numerical solutions of both the effective nonlinear diffusion equation and the stochastic particle system are presented and compared. As an application, the case of diffusion under a ratchet potential is considered, and the change in transport properties due to excluded-volume and confinement effects is examined. © 2013 Society for Mathematical Biology.

Simulations of water nano-confined between corrugated planes

Science.gov (United States)

Zubeltzu, Jon; Artacho, Emilio

2017-11-01

Water confined to nanoscale widths in two dimensions between ideal planar walls has been the subject of ample study, aiming at understanding the intrinsic response of water to confinement, avoiding the consideration of the chemistry of actual confining materials. In this work, we study the response of such nanoconfined water to the imposition of a periodicity in the confinement by means of computer simulations, both using empirical potentials and from first-principles. For that we propose a periodic confining potential emulating the atomistic oscillation of the confining walls, which allows varying the lattice parameter and amplitude of the oscillation. We do it for a triangular lattice, with several values of the lattice parameter: one which is ideal for commensuration with layers of Ih ice and other values that would correspond to more realistic substrates. For the former, the phase diagram shows an overall rise of the melting temperature. The liquid maintains a bi-layer triangular structure, however, despite the fact that it is not favoured by the external periodicity. The first-principles liquid is significantly affected by the modulation in its layering and stacking even at relatively small amplitudes of the confinement modulation. Beyond some critical modulation amplitude, the hexatic phase present in flat confinement is replaced by a trilayer crystalline phase unlike any of the phases encountered for flat confinement. For more realistic lattice parameters, the liquid does not display higher tendency to freeze, but it clearly shows inhomogeneous behaviour as the strength of the rugosity increases. In spite of this expected inhomogeneity, the structural and dynamical response of the liquid is surprisingly insensitive to the external modulation. Although the first-principles calculations give a more triangular liquid than the one observed with empirical potentials (TIP4P/2005), both agree remarkably well for the main conclusions of the study.

Effect of Short-Circuit Pathways on Water Quality in Selected Confined Aquifers (Invited)

Science.gov (United States)

McMahon, P. B.

2010-12-01

Confined aquifers in the United States generally contain fewer anthropogenic contaminants than unconfined aquifers because confined aquifers often contain water recharged prior to substantial human development and redox conditions are more reducing, which favors degradation of common contaminants like nitrate and chlorinated solvents. Groundwater in a confined part of the High Plains aquifer near York, Nebraska had an adjusted radiocarbon age of about 2,000 years, and groundwater in a confined part of the Floridan aquifer near Tampa, Florida had apparent ages greater than 60 years on the basis of tritium measurements. Yet compounds introduced more recently into the environment (anthropogenic nitrate and volatile organic compounds) were detected in selected public-supply wells completed in both aquifers. Depth-dependent measurements of flow and chemistry in the pumping supply wells, groundwater age dating, numerical modeling of groundwater flow, and other monitoring data indicated that the confined aquifers sampled by the supply wells were connected to contaminated unconfined aquifers by short-circuit pathways. In the High Plains aquifer, the primary pathways appeared to be inactive irrigation wells screened in both the unconfined and confined aquifers. In the Floridan aquifer, the primary pathways were karst sinkholes and conduits. Heavy pumping in both confined systems exacerbated the problem by reducing the potentiometric surface and increasing groundwater velocities, thus enhancing downward gradients and reducing reaction times for processes like denitrification. From a broader perspective, several confined aquifers in the U.S. have experienced large declines in their potentiometric surfaces because of groundwater pumping and this could increase the potential for contamination in those aquifers, particularly where short-circuit pathways connect them to shallower, contaminated sources of water, such as was observed in York and Tampa.

Magnetic confinement

Energy Technology Data Exchange (ETDEWEB)

Batistoni, Paola; De Marco, Francesco; Pieroni, Leonardo (ed.)

2005-07-01

The Frascati Tokamak Upgrade (FTU) is a compact, high-magnetic-field tokamak capable of operating at density and magnetic field values similar to, or even encompassing, those of International Thermonuclear Experimental Reactor (ITER) and therefore provides a unique opportunity to explore physics issues that are directly relevant to ITER. During 2004 the experimental activities were focussed on fully exploiting the lower hybrid system (for generating and controlling the plasma current) and the electron cyclotron heating system (joint experiment with the Institute of Plasma Physics of the National Research Council, Milan). With all four gyrotrons in operation, full electron cyclotron power was achieved up to a record level of 1.5 MW. By simultaneously injecting lower hybrid waves, to tailor the plasma current radial profile, and electron cyclotron waves, to heat the plasma centre, good confinement regimes with internal transport barriers were obtained at the highest plasma density values ever achieved for this operation regime (n {approx}1.5X10{sup 20}m{sup -3}). Specific studies were devoted to optimising the coupling of lower hybrid waves to the plasma (by real-time control of the plasma position) and to generating current by electron cyclotron current drive. The new scanning CO{sub 2} interferometer (developed by the Reversed Field Experiment Consortium) for high spatial and time resolution (1 cm/50 {mu}s) density profile measurements was extensively used. The Thomson scattering diagnostic was upgraded and enabled observation of scattered signals associated with the Confinement background plasma dynamics. As for theoretical studies on the dynamics of turbulence in plasmas, the transition from Bohm-like scaling to gyro-Bohm scaling of the local plasma diffusivity was demonstrated on the basis of a generalised four wave model (joint collaboration with Princeton Plasma Physics Laboratory and the University of California at Irvine). The transition from weak to strong

Magnetic confinement

International Nuclear Information System (INIS)

Batistoni, Paola; De Marco, Francesco; Pieroni, Leonardo

2005-01-01

The Frascati Tokamak Upgrade (FTU) is a compact, high-magnetic-field tokamak capable of operating at density and magnetic field values similar to, or even encompassing, those of International Thermonuclear Experimental Reactor (ITER) and therefore provides a unique opportunity to explore physics issues that are directly relevant to ITER. During 2004 the experimental activities were focussed on fully exploiting the lower hybrid system (for generating and controlling the plasma current) and the electron cyclotron heating system (joint experiment with the Institute of Plasma Physics of the National Research Council, Milan). With all four gyrotrons in operation, full electron cyclotron power was achieved up to a record level of 1.5 MW. By simultaneously injecting lower hybrid waves, to tailor the plasma current radial profile, and electron cyclotron waves, to heat the plasma centre, good confinement regimes with internal transport barriers were obtained at the highest plasma density values ever achieved for this operation regime (n ∼1.5X10 20 m -3 ). Specific studies were devoted to optimising the coupling of lower hybrid waves to the plasma (by real-time control of the plasma position) and to generating current by electron cyclotron current drive. The new scanning CO 2 interferometer (developed by the Reversed Field Experiment Consortium) for high spatial and time resolution (1 cm/50 μs) density profile measurements was extensively used. The Thomson scattering diagnostic was upgraded and enabled observation of scattered signals associated with the Confinement background plasma dynamics. As for theoretical studies on the dynamics of turbulence in plasmas, the transition from Bohm-like scaling to gyro-Bohm scaling of the local plasma diffusivity was demonstrated on the basis of a generalised four wave model (joint collaboration with Princeton Plasma Physics Laboratory and the University of California at Irvine). The transition from weak to strong energetic particle

Coupling motion of colloidal particles in quasi-two-dimensional confinement

International Nuclear Information System (INIS)

Ma, Jun; Jing, Guangyin

2014-01-01

The Brownian motion of colloidal particles in quasi-two-dimensional (q2D) confinement displays a distinct kinetic character from that in bulk. Here we experimentally report dynamic coupling motion of Brownian particles in a relatively long process (∼100 h), which displays a quasi-equilibrium state in the q2D system. In the quasi-equilibrium state, the q2D confinement results in the coupling of particle motions, which slowly damps the motion and interaction of particles until the final equilibrium state is reached. The process of approaching the equilibrium is a random relaxation of a many-body interaction system of Brownian particles. As the relaxation proceeds for ∼100 h, the system reaches the equilibrium state in which the energy gained by the particles from the stochastic collision in the whole system is counteracted by the dissipative energy resulting from the collision. The relaxation time of this stochastic q2D system is 17.7 h. The theory is developed to explain coupling motions of Brownian particles in q2D confinement. (paper)

Random walks and polygons in tight confinement

International Nuclear Information System (INIS)

Diao, Y; Ernst, C; Ziegler, U

2014-01-01

We discuss the effect of confinement on the topology and geometry of tightly confined random walks and polygons. Here the walks and polygons are confined in a sphere of radius R ≥ 1/2 and the polygons are equilateral with n edges of unit length. We illustrate numerically that for a fixed length of random polygons the knotting probability increases to one as the radius decreases to 1/2. We also demonstrate that for random polygons (walks) the curvature increases to πn (π(n – 1)) as the radius approaches 1/2 and that the torsion decreases to ≈ πn/3 (≈ π(n – 1)/3). In addition we show the effect of length and confinement on the average crossing number of a random polygon

Exploring Heterogeneous and Time-Varying Materials for Photonic Applications, Towards Solutions for the Manipulation and Confinement of Light.

KAUST Repository

San Roman Alerigi, Damian

2014-01-01

Over the past several decades our understanding and meticulous characterization of the transient and spatial properties of materials evolved rapidly. The results present an exciting field for discovery, and craft materials to control and reshape light that we are just beginning to fathom. State-of-the-art nano-deposition processes, for example, can be utilized to build stratified waveguides made of thin dielectric layers, which put together result in a material with effective abnormal dispersion. Moreover, materials once deemed well known are revealing astonishing properties, v.gr. chalcogenide glasses undergo an atomic reconfiguration when illuminated with electrons or photons, this ensues in a temporal modification of its permittivity and permeability which could be used to build new Photonic Integrated Circuits.. This work revolves around the characterization and model of heterogeneous and time-varying materials and their applications, revisits Maxwell's equations in the context of nonlinear space- and time-varying media, and based on it introduces a numerical scheme that can be used to model waves in this kind of media. Finally some interesting applications for light confinement and beam transformations are shown.

Exploring Heterogeneous and Time-Varying Materials for Photonic Applications, Towards Solutions for the Manipulation and Confinement of Light.

KAUST Repository

San Roman Alerigi, Damian

2014-11-01

Over the past several decades our understanding and meticulous characterization of the transient and spatial properties of materials evolved rapidly. The results present an exciting field for discovery, and craft materials to control and reshape light that we are just beginning to fathom. State-of-the-art nano-deposition processes, for example, can be utilized to build stratified waveguides made of thin dielectric layers, which put together result in a material with effective abnormal dispersion. Moreover, materials once deemed well known are revealing astonishing properties, v.gr. chalcogenide glasses undergo an atomic reconfiguration when illuminated with electrons or photons, this ensues in a temporal modification of its permittivity and permeability which could be used to build new Photonic Integrated Circuits.. This work revolves around the characterization and model of heterogeneous and time-varying materials and their applications, revisits Maxwell\\'s equations in the context of nonlinear space- and time-varying media, and based on it introduces a numerical scheme that can be used to model waves in this kind of media. Finally some interesting applications for light confinement and beam transformations are shown.

The cruel and unusual phenomenology of solitary confinement.

Science.gov (United States)

Gallagher, Shaun

2014-01-01

What happens when subjects are deprived of intersubjective contact? This paper looks closely at the phenomenology and psychology of one example of that deprivation: solitary confinement. It also puts the phenomenology and psychology of solitary confinement to use in the legal context. Not only is there no consensus on whether solitary confinement is a "cruel and unusual punishment," there is no consensus on the definition of the term "cruel" in the use of that legal phrase. I argue that we can find a moral consensus on the meaning of "cruelty" by looking specifically at the phenomenology and psychology of solitary confinement.

Higher representations: Confinement and large N

International Nuclear Information System (INIS)

Sannino, Francesco

2005-01-01

We investigate the confining phase transition as a function of temperature for theories with dynamical fermions in the two index symmetric and antisymmetric representation of the gauge group. By studying the properties of the center of the gauge group we predict for an even number of colors a confining phase transition, if second order, to be in the universality class of Ising in three dimensions. This is due to the fact that the center group symmetry does not break completely for an even number of colors. For an odd number of colors the center group symmetry breaks completely. This pattern remains unaltered at a large number of colors. The confining/deconfining phase transition in these theories at large and finite N is not mapped in the one of super Yang-Mills theory. We extend the Polyakov loop effective theory to describe the confining phase transition of the theories studied here for a generic number of colors. Our results are not modified when adding matter in the same higher dimensional representations of the gauge group. We comment on the interplay between confinement and chiral symmetry in these theories and suggest that they are ideal laboratories to shed light on this issue also for ordinary QCD. We compare the free energy as a function of temperature for different theories. We find that the conjectured thermal inequality between the infrared and ultraviolet degrees of freedom computed using the free energy does not lead to new constraints on asymptotically free theories with fermions in higher dimensional representations of the gauge group. Since the center of the gauge group is an important quantity for the confinement properties at zero temperature our results are relevant here as well

Magnetic well for plasma confinement

International Nuclear Information System (INIS)

Valfells, A.; Chiu, Y.C.

1977-01-01

A multipole magnetic well for plasma confinement includes a plurality of current-carrying coils placed on planes corresponding to the facets of a regular polyhedron that can be symmetrically circumscribed about a sphere. The direction of current in the coils is such as to minimize the flux density at the center of the polyhedron, thereby providing a confinement well with three-dimensional symmetry having an increasing flux density in all directions from the center. 16 claims, 18 figures

Neutron spectroscopy for confinement studies

International Nuclear Information System (INIS)

Zorn, R.

2010-01-01

Neutron spectroscopy is an important method for the study of microscopic dynamics because it captures the spatial as well as the temporal aspects of the atomic or molecular motion. In this article techniques will be presented which are of special importance for the study of confined systems. Many of these are based on the fact that neutron scattering is isotope-dependent. Possible sources of systematic errors in measurements of confined systems will be pointed out. (author)

Improved mechanical stability of HKUST-1 in confined nanospace.

Science.gov (United States)

Casco, M E; Fernández-Catalá, J; Martínez-Escandell, M; Rodríguez-Reinoso, F; Ramos-Fernández, E V; Silvestre-Albero, J

2015-09-28

One of the main concerns in the technological application of several metal-organic frameworks (MOFs) relates to their structural instability under pressure (after a conforming step). Here we report for the first time that mechanical instability can be highly improved via nucleation and growth of MOF nanocrystals in the confined nanospace of activated carbons.

Diffusion of Finite-Size Particles in Confined Geometries

KAUST Repository

Bruna, Maria

2013-05-10

The diffusion of finite-size hard-core interacting particles in two- or three-dimensional confined domains is considered in the limit that the confinement dimensions become comparable to the particle\\'s dimensions. The result is a nonlinear diffusion equation for the one-particle probability density function, with an overall collective diffusion that depends on both the excluded-volume and the narrow confinement. By including both these effects, the equation is able to interpolate between severe confinement (for example, single-file diffusion) and unconfined diffusion. Numerical solutions of both the effective nonlinear diffusion equation and the stochastic particle system are presented and compared. As an application, the case of diffusion under a ratchet potential is considered, and the change in transport properties due to excluded-volume and confinement effects is examined. © 2013 Society for Mathematical Biology.

Recycling and particle confinement characteristics in TFR 600

International Nuclear Information System (INIS)

1980-07-01

Recycling rates and gross particle confinement time have been determined in TFR 600 by measuring the time evolution of plasma density and the flow rate of the injected neutral gas. Several conditioning methods of walls and chamber components are briefly described and the main results obtained with ohmic, neutral injection and R.F. heatings are summarized. For different types of experiments with pure plasmas, a global model can be used to describe the general recycling behavior of hydrogen isotopes and to obtain the recycling coefficient during a discharge. The effective particle life time and the total number of trapped particles in the inner wall are also directly obtained for each discharge. More than 50% of the injected gas is trapped during a discharge and released from the wall between two successive discharges. This low retention rate is indicative of the behavior of clean surfaces. The boundary plasma density and temperature are measured with Langmuir probes to determine the gross particle confinement time and the recycling rate of the walls. Hsub(α) measurements indicate a low ionization rate in the shadow of the limiter. The plasma edge temperature 14 cm -3 . In spite of the high recycling rate of deuterium atoms on the wall, low injection of light impurities are observed due to the poor oxygen and carbon contents of the surface. The radiation power is less than 30% of the total input power with 460 kW of injected R.F. power into the torus

Confinement and power balance in the S-1 spheromak

Energy Technology Data Exchange (ETDEWEB)

Levinton, F.M.; Meyerhofer, D.D.; Mayo, R.M.; Janos, A.C.; Ono, Y.; Ueda, Y.; Yamada, M.

1989-07-01

The confinement and scaling features of the S-1 spheromak have been investigated using magnetic, spectroscopic, and Thomson scattering data in conjunction with numerical modeling. Results from the multipoint Thomson scattering diagnostic shows that the central beta remains constant (/beta//sub to/ /approximately/ 5%) as the plasma current density increases from 0.68--2.1 MA/m/sup 2/. The density is observed to increase slowly over this range, while the central electron temperature increases much more rapidly. Analysis of the global plasma parameters shows a decrease in the volume average beta and energy confinement as the total current is increased. The power balance has been modeled numerically with a 0-D non-equilibrium time-dependent coronal model and is consistent with the experimental observations. 20 refs., 12 figs., 2 tabs.

Confinement and power balance in the S-1 spheromak

International Nuclear Information System (INIS)

Levinton, F.M.; Meyerhofer, D.D.; Mayo, R.M.; Janos, A.C.; Ono, Y.; Ueda, Y.; Yamada, M.; Rochester Univ., NY; Los Alamos National Lab., NM; Princeton Univ., NJ

1989-07-01

The confinement and scaling features of the S-1 spheromak have been investigated using magnetic, spectroscopic, and Thomson scattering data in conjunction with numerical modeling. Results from the multipoint Thomson scattering diagnostic shows that the central beta remains constant (β to ∼ 5%) as the plasma current density increases from 0.68--2.1 MA/m 2 . The density is observed to increase slowly over this range, while the central electron temperature increases much more rapidly. Analysis of the global plasma parameters shows a decrease in the volume average beta and energy confinement as the total current is increased. The power balance has been modeled numerically with a 0-D non-equilibrium time-dependent coronal model and is consistent with the experimental observations. 20 refs., 12 figs., 2 tabs

Energy confinement in the tokamak devices pulsator and ASDEX

International Nuclear Information System (INIS)

Klueber, O.; Murmann, H.

1982-04-01

The energy confinement of ohmically heated hydrogen plasmas obtained in the ASDEX and Pulsator tokamaks is investigated. In both devices, the confinement time does not follow a simple scaling law of the type tausub(E) approx. equal to nsub(e)a 2 . In the case of Pulsator, a regime is identified in which the transport is governed by electron heat conduction. The experimental data are compared with an analytic solution of the energy balance equation from which a heat diffusivity chisub(e) approx. equal to Zsub(eff)sup(1/3)/nsub(e)(r)Tsub(e)sup(1/2)(r)q(r) is inferred. chisub(i) is supposed to be neoclassical (plateau regime). Heat conduction following these laws is shown to lead to a consistent description of the full data set. (orig.)

Pellet fuelling into radiative improved confinement discharges in TEXTOR-94

NARCIS (Netherlands)

Hobirk, J.; Messiaen, A. M.; Finken, K.H.; Ongena, J.; Brix, M.; R. Jaspers,; Koslowski, H. R.; Kramer-Flecken, A.; Mank, G.; Rapp, J.; Telesca, G.; Unterberg, B.

2000-01-01

Normally pellet injection in strongly heated discharges leads at most to a relatively short improvement of the energy and particle confinement times. In contrast to this finding, the radiative improved (RI) mode plasma of TEXTOR-94 is a very well suited target for pellet injection: the interaction

Helical Confinement Concepts

Energy Technology Data Exchange (ETDEWEB)

Beidler, C; Brakel, R; Burhenn, R; Dinklage, A; Erckmann, V; Feng, Y; Geiger, J; Hartmann, D; Hirsch, M; Jaenicke, R; Koenig, R; Laqua, H P; Maassberg, H; Wagner, F; Weller, A; Wobig, H [Max-Planck Institut fuer Plasmaphysik, EURATOM Association, Greifswald (Germany)

2012-09-15

Stellarators, conceived 1951 by Lyman Spitzer in Princeton, are toroidal devices that confine a plasma in a magnetic field which originates from currents in coils outside the plasma. A plasma current driven by external means, for example by an ohmic transformer, is not required for confinement. Supplying the desired poloidal field component by external coils leads to a helically structured plasma topology. Thus stellarators - or helical confinement devices - are fully three-dimensional in contrast to the toroidal (rotational) symmetry of tokamaks. As stellarators can be free of an inductive current, whose radial distribution depends on the plasma parameters, their equilibrium must not be established via the evolving plasma itself, but to a first order already given by the vacuum magnetic field. They do not need an active control (like positional feedback) and therefore cannot suffer from its failure. The outstanding conceptual advantage of stellarators is the potential of steady state plasma operation without current drive. As there is no need for current drive, the recirculating power is expected to be smaller than in equivalent tokamaks. The lack of a net current avoids current driven instabilities; specifically, no disruptions, no resistive wall modes and no conventional or neoclassical tearing modes appear. Second order pressure-driven currents (Pfirsch-Schlueter, bootstrap) exist but they can be modified and even minimized by the magnetic design. The magnetic configuration of helical devices naturally possesses a separatrix, which allows the implementation of a helically structured divertor for exhaust and impurity control. (author)

Confinement and quark structure of light hadrons

International Nuclear Information System (INIS)

Efimov, G.V.; Ivanov, M.A.

1988-01-01

We present a quark confinement model (QCM) for the description of the low-energy physics of light hadrons (mesons and baryons). The model is based on two hypotheses. First, the quark confinement is realized as averaging over vacuum gluon fields which are believed to provide the confinement of any colour objects. Second, hadrons are treated as collective colourless excitations of quark-gluon interactions. The description of strong, electromagnetic and weak interactions of mesons and baryons at the low energy is given from a unique point of view

Topological superfluids confined in a nanoscale slab geometry

Science.gov (United States)

Saunders, John

2013-03-01

Nanofluidic samples of superfluid 3He provide a route to explore odd-parity topological superfluids and their surface, edge and defect-bound excitations under well controlled conditions. We have cooled superfluid 3He confined in a precisely defined nano-fabricated cavity to well below 1 mK for the first time. We fingerprint the order parameter by nuclear magnetic resonance, exploiting a SQUID NMR spectrometer of exquisite sensitivity. We demonstrate that dimensional confinement, at length scales comparable to the superfluid Cooper-pair diameter, has a profound influence on the superfluid order of 3He. The chiral A-phase is stabilized at low pressures, in a cavity of height 650 nm. At higher pressures we observe 3He-B with a surface induced planar distortion. 3He-B is a time-reversal invariant topological superfluid, supporting gapless Majorana surface states. In the presence of the small symmetry breaking NMR static magnetic field we observe two possible B-phase states of the order parameter manifold, which can coexist as domains. Non-linear NMR on these states enables a measurement of the surface induced planar distortion, which determines the spectral weight of the surface excitations. The expected structure of the domain walls is such that, at the cavity surface, the line separating the two domains is predicted to host fermion zero modes, protected by symmetry and topology. Increasing confinement should stabilize new p-wave superfluid states of matter, such as the quasi-2D gapped A phase, which breaks time reversal symmetry, has a protected chiral edge mode, and may host half-quantum vortices with a Majorana zero-mode at the core. We discuss experimental progress toward this phase, through measurements on a 100 nm cavity. On the other hand, a cavity height of 1000 nm may stabilize a novel ``striped'' superfluid with spatially modulated order parameter. Supported by EPSRC (UK) GR/J022004/1 and European Microkelvin Consortium, FP7 grant 228464

High temperature L- and H-mode confinement in JET

International Nuclear Information System (INIS)

Balet, B.; Boyd, D.A.; Campbell, D.J.

1990-01-01

The energy confinement properties of low density, high ion temperature L- and H-mode plasmas are investigated. For L-mode plasmas it is shown that, although the global confinement is independent of density, the energy confinement in the central region is significantly better at low densities than at higher densities. The improved confinement appears to be associated with the steepness of the density gradient. For the H-mode phase, although the confinement at the edge is dramatically improved, which is once again associated with the steep density gradient in the edge region, the central confinement properties are essentially the same as for the standard L-mode. The results are compared in a qualitative manner with the predictions of the ion temperature gradient instability theory and appear to be in disagreement with some aspects of this theory. (author). 13 refs, 15 figs

Repetitive pulsed power technology for inertial-confinement fusion

International Nuclear Information System (INIS)

Prestwich, K.R.; Buttram, M.T.

1983-01-01

The pulsed power requirements for inertial-confinement fusion reactors are defined for ion-beam and laser drivers. Several megajoule beams with 100's of terrawatt peak powers must be delivered to the reactor chamber 1 to 10 times per second. Ion-beam drivers are relatively efficient requiring less energy storage in the pulsed-power system but more time compression in the power flow chain than gas lasers. These high peak powers imply very large numbers of components for conventional pulse-power systems. A new design that significantly reduces the number of components is presented

Confined Mobility of TonB and FepA in Escherichia coli Membranes.

Directory of Open Access Journals (Sweden)

Yoriko Lill

Full Text Available The important process of nutrient uptake in Escherichia coli, in many cases, involves transit of the nutrient through a class of beta-barrel proteins in the outer membrane known as TonB-dependent transporters (TBDTs and requires interaction with the inner membrane protein TonB. Here we have imaged the mobility of the ferric enterobactin transporter FepA and TonB by tracking them in the membranes of live E. coli with single-molecule resolution at time-scales ranging from milliseconds to seconds. We employed simple simulations to model/analyze the lateral diffusion in the membranes of E.coli, to take into account both the highly curved geometry of the cell and artifactual effects expected due to finite exposure time imaging. We find that both molecules perform confined lateral diffusion in their respective membranes in the absence of ligand with FepA confined to a region [Formula: see text] μm in radius in the outer membrane and TonB confined to a region [Formula: see text] μm in radius in the inner membrane. The diffusion coefficient of these molecules on millisecond time-scales was estimated to be [Formula: see text] μm2/s and [Formula: see text] μm2/s for FepA and TonB, respectively, implying that each molecule is free to diffuse within its domain. Disruption of the inner membrane potential, deletion of ExbB/D from the inner membrane, presence of ligand or antibody to FepA and disruption of the MreB cytoskeleton was all found to further restrict the mobility of both molecules. Results are analyzed in terms of changes in confinement size and interactions between the two proteins.

Solitons and confinement

International Nuclear Information System (INIS)

Swieca, J.A.

1976-01-01

Some aspects of two recent developments in quantum field theory are discussed. First, related with 'extended particles' such as soliton, kink and the 't Hooft monopole. Second, with confinement of particles which are realized in the Schwinger model [pt

Evaluation of the confinement option for LMRs

International Nuclear Information System (INIS)

Himes, D.A.; Stepnewski, D.D.; Franz, G.R.

1985-12-01

The coolant in liquid metal cooled reactors operates at low pressures and therefore contains relatively little stored energy compared to LWR systems. This presents the possibility of using a more conventional building for containment coupled with a confinement system which vents the internal volume of the building through a filter/scrubber. The confinement system would be designed to keep the internal pressure in the containment near atmospheric thereby minimizing unfiltered leakage. The principal benefits of such an arrangement would be lower capital cost and less stringent leaktightness requirements permitting simpler and less disruptive testing. In conclusion, the confinement system assumed here would reduce consequences to the public of an LMR HCDA to acceptable levels. However control room doses are unacceptable due to the noble gas concentration inside the control room. A confinement system is therefore a viable design option for LMR's provided means are included for keeping noble gases out of the control room. Such means are readily available including, for example, selectable remote air intakes, an exhaust stack, or a noble gas filter. Probably the most satisfactory alternative would be a large cryogenic filter on the confinement system exhaust

Packing frustration in dense confined fluids.

Science.gov (United States)

Nygård, Kim; Sarman, Sten; Kjellander, Roland

2014-09-07

Packing frustration for confined fluids, i.e., the incompatibility between the preferred packing of the fluid particles and the packing constraints imposed by the confining surfaces, is studied for a dense hard-sphere fluid confined between planar hard surfaces at short separations. The detailed mechanism for the frustration is investigated via an analysis of the anisotropic pair distributions of the confined fluid, as obtained from integral equation theory for inhomogeneous fluids at pair correlation level within the anisotropic Percus-Yevick approximation. By examining the mean forces that arise from interparticle collisions around the periphery of each particle in the slit, we calculate the principal components of the mean force for the density profile--each component being the sum of collisional forces on a particle's hemisphere facing either surface. The variations of these components with the slit width give rise to rather intricate changes in the layer structure between the surfaces, but, as shown in this paper, the basis of these variations can be easily understood qualitatively and often also semi-quantitatively. It is found that the ordering of the fluid is in essence governed locally by the packing constraints at each single solid-fluid interface. A simple superposition of forces due to the presence of each surface gives surprisingly good estimates of the density profiles, but there remain nontrivial confinement effects that cannot be explained by superposition, most notably the magnitude of the excess adsorption of particles in the slit relative to bulk.

Plasma transport simulation modeling for helical confinement systems

International Nuclear Information System (INIS)

Yamazaki, K.; Amano, T.

1991-08-01

New empirical and theoretical transport models for helical confinement systems are developed based on the neoclassical transport theory including the effect of radial electric field and multi-helicity magnetic components, and the drift wave turbulence transport for electrostatic and electromagnetic modes, or the anomalous semi-empirical transport. These electron thermal diffusivities are compared with CHS (Compact Helical System) experimental data, which indicates that the central transport coefficient of the ECH plasma agrees with the neoclassical axi-symmetric value and the transport outside the half radius is anomalous. On the other hand, the transport of NBI-heated plasmas is anomalous in the whole plasma region. This anomaly is not explained by the electrostatic drift wave turbulence models in these flat-density-profile discharges. For the detailed prediction of plasma parameters in LHD (Large Helical Device), 3-D(dimensional) equilibrium/1-D transport simulations including empirical or drift wave turbulence models are carried out, which suggests that the global confinement time of LHD is determined mainly by the electron anomalous transport near the plasma edge region rather than the helical ripple transport in the core region. Even if the ripple loss can be eliminated, the increase of the global confinement is 10%. However, the rise in the central ion temperature is more than 20%. If the anomalous loss can be reduced to the half level of the present scaling, like so-called 'H-mode' of the tokamak discharge, the neoclassical ripple loss through the ion channel becomes important even in the plasma core. The 5% radial inward shift of the plasma column with respect to the major radius is effective for improving plasma confinement and raising more than 50% of the fusion product by reducing this neoclassical asymmetric ion transport loss and increasing 10% in the plasma radius. (author)

Analytic properties of form factors in strictly confining models

International Nuclear Information System (INIS)

Csikor, F.

1979-12-01

An argument is presented showing that strict confinement implies the possible existence of an (unwanted) branch point at q 2 =0 in the form factors. In case of a bag extended to infinity in the relative time, the branch point is certainly there (provided that the form factor is non zero at q 2 =0). (author)

Cockroaches traverse crevices, crawl rapidly in confined spaces, and inspire a soft, legged robot

Science.gov (United States)

Jayaram, Kaushik; Full, Robert J.

2016-01-01

Jointed exoskeletons permit rapid appendage-driven locomotion but retain the soft-bodied, shape-changing ability to explore confined environments. We challenged cockroaches with horizontal crevices smaller than a quarter of their standing body height. Cockroaches rapidly traversed crevices in 300–800 ms by compressing their body 40–60%. High-speed videography revealed crevice negotiation to be a complex, discontinuous maneuver. After traversing horizontal crevices to enter a vertically confined space, cockroaches crawled at velocities approaching 60 cm⋅s−1, despite body compression and postural changes. Running velocity, stride length, and stride period only decreased at the smallest crevice height (4 mm), whereas slipping and the probability of zigzag paths increased. To explain confined-space running performance limits, we altered ceiling and ground friction. Increased ceiling friction decreased velocity by decreasing stride length and increasing slipping. Increased ground friction resulted in velocity and stride length attaining a maximum at intermediate friction levels. These data support a model of an unexplored mode of locomotion—“body-friction legged crawling” with body drag, friction-dominated leg thrust, but no media flow as in air, water, or sand. To define the limits of body compression in confined spaces, we conducted dynamic compressive cycle tests on living animals. Exoskeletal strength allowed cockroaches to withstand forces 300 times body weight when traversing the smallest crevices and up to nearly 900 times body weight without injury. Cockroach exoskeletons provided biological inspiration for the manufacture of an origami-style, soft, legged robot that can locomote rapidly in both open and confined spaces. PMID:26858443

28 CFR 570.21 - Time-frames.

Science.gov (United States)

2010-07-01

... 28 Judicial Administration 2 2010-07-01 2010-07-01 false Time-frames. 570.21 Section 570.21... PROGRAMS Pre-Release Community Confinement § 570.21 Time-frames. (a) Community confinement. Inmates may be... inmate's term of imprisonment or six months. (c) Exceeding time-frames. These time-frames may be exceeded...

The cruel and unusual phenomenology of solitary confinement

Directory of Open Access Journals (Sweden)

Shaun eGallagher

2014-06-01

Full Text Available What happens when subjects are deprived of intersubjective contact? This paper looks closely at the phenomenology and psychology of one example of that deprivation: solitary confinement. It also puts the phenomenology and psychology of solitary confinement to use in the legal context. Not only is there no consensus on whether solitary confinement is a cruel and unusual punishment, there is no consensus on the definition of the term ‘cruel’ in the use of that legal phrase. I argue that we can find a moral consensus on the meaning of ‘cruelty’ by looking specifically at the phenomenology and psychology of solitary confinement.

Congestion and communication in confined ant traffic

Science.gov (United States)

Gravish, Nick; Gold, Gregory; Zangwill, Andrew; Goodisman, Michael A. D.; Goldman, Daniel I.

2014-03-01

Many social animals move and communicate within confined spaces. In subterranean fire ants Solenopsis invicta, mobility within crowded nest tunnels is important for resource and information transport. Within confined tunnels, communication and traffic flow are at odds: trafficking ants communicate through tactile interactions while stopped, yet ants that stop to communicate impose physical obstacles on the traffic. We monitor the bi-directional flow of fire ant workers in laboratory tunnels of varied diameter D. The persistence time of communicating ant aggregations, τ, increases approximately linearly with the number of participating ants, n. The sensitivity of traffic flow increases as D decreases and diverges at a minimum diameter, Dc. A cellular automata model incorporating minimal traffic features--excluded volume and communication duration--reproduces features of the experiment. From the model we identify a competition between information transfer and the need to maintain jam-free traffic flow. We show that by balancing information transfer and traffic flow demands, an optimum group strategy exists which maximizes information throughput. We acknowledge funding from NSF PoLS #0957659 and #PHY-1205878.

Confinement and strings in MQCD

International Nuclear Information System (INIS)

Hanany, A.; Strassler, M.J.; Zaffaroni, A.

1998-01-01

We study aspects of confinement in the M-theory fivebrane version of QCD (MQCD). We show heavy quarks are confined in hadrons (which take the form of membrane-fivebrane bound states) for N=1 and softly broken N=2 SU(N) MQCD. We explore and clarify the transition from the exotic physics of the latter to the standard physics of the former. In particular, the many strings and quark-antiquark mesons found in N=2 field theory by Douglas and Shenker are reproduced. It is seen that in the N=1 limit all but one such meson disappears while all of the strings survive. The strings of softly broken N=2, N=1, and even non-supersymmetric SU(N) MQCD have a common ratio for their tensions as a function of the amount of flux they carry. We also comment on the almost BPS properties of the Douglas-Shenker strings and discuss the brane picture for monopole confinement on N=2 QCD Higgs branches. (orig.)

An outbreak of echovirus 11 amongst neonates in a confinement home in Penang, Malaysia.

Science.gov (United States)

Bina Rai, S; Wan Mansor, H; Vasantha, T; Norizah, I; Chua, K B

2007-08-01

Confinement homes are private institutions that provide full-time care for newborn babies and their respective postpartum mothers up to one month after delivery. An outbreak of fever and diarrhoea amongst newborns occurred in one such confinement home in Penang between the months of September to October 2004. An outbreak investigation was carried out including all babies, their respective mothers and workers in the home to determine the source of the outbreak and to institute control measures. Based on a working case definition of febrile illness with or without diarrhoea, 11 out of the 13 babies in the confinement home met the case definition. One hundred percent had symptoms of fever. 36.4% had symptoms of diarrhea and other respiratory conditions respectively. The attack rate of among babies in the confinement home was 90%. Echovirus 11 was isolated from 3 out of the 11 febrile cases. Echovirus 11 was isolated from the cerebrospinal fluid and stool of another baby at a private hospital that was epidemiologically linked to the first case. In conclusion, the outbreak of febrile illness amongst newborn babies in the affected confinement home was due to echovirus 11. The source was probably health-care associated with efficient transmission within the confinement home. The faecal-oral route was the most likely mode of transmission.

Don't Fence Me In: Free Meanders in a Confined River Valley

Science.gov (United States)

Eke, E. C.; Wilcock, P. R.

2015-12-01

The interaction between meandering river channels and inerodible valley walls provides a useful test of our ability to understand meander dynamics. In some cases, river meanders confined between valley walls display distinctive angular bends in a dynamic equilibrium such that their size and shape persist as the meander migrates. In other cases, meander geometry is more varied and changes as the meander migrates. The ratio of channel to valley width has been identified as a useful parameter for defining confined meanders, but is not sufficient to distinguish cases in which sharp angular bends are able to migrate with little change in geometry. Here, we examine the effect of water and sediment supply on the geometry of confined rivers in order to identify conditions under which meander geometry reaches a persistent dynamic equilibrium. Because channel width and meander geometry are closely related, we use a numerical meander model that allows for independent migration of both banks, thereby allowing channel width to vary in space and time. We hypothesize that confined meanders with persistent angular bends have smaller transport rates of bed material and that their migration is driven by erosion of the cutbank (bank-pull migration). When bed material supply is sufficiently large that point bar deposition drives meander migration (bar-push migration), confined meander bends have a larger radius of curvature and a geometry that varies as the meander migrates. We test this hypothesis using historical patterns of confined meander migration for rivers with different rates of sediment supply and bed material transport. Interpretation of the meander migration pattern is provided by the free-width meander migration model.

Confinement effects on strongly polar alkylcyanobiphenyl liquid crystals probed by dielectric spectroscopy

Energy Technology Data Exchange (ETDEWEB)

Leys, Jan; Glorieux, Christ; Thoen, Jan [Laboratorium voor Akoestiek en Thermische Fysica, Departement Natuurkunde en Sterrenkunde, Katholieke Universiteit Leuven, Celestijnenlaan 200D-bus 2416, B-3001 Leuven (Belgium)], E-mail: jan.leys@fys.kuleuven.be, E-mail: jan.thoen@fys.kuleuven.be

2008-06-18

Dielectric spectroscopy has often been used to study confinement effects in alkylcyanobiphenyl liquid crystals. In this paper, we highlight some of the effects that have been discovered previously and add new data and interpretation. Aerosil nanoparticles form a hydrogen bonded random porous network. In dispersions of alkylcyanobiphenyls with aerosils, an additional slow process arises, that we ascribe to the relaxation of liquid crystal molecules in close interaction with these nanoparticles. Their relaxation is retarded by a hydrogen bond interaction between the cyano group of the liquid crystals and an aerosil surface hydroxyl group. A similar surface process is also observed in Vycor porous glass, a random rigid structure with small pores. A comparison of the temperature dependence of the relaxation times of the surface processes in decylcyanobiphenyl and isopentylcyanobiphenyl is made, both for Vycor and aerosil confinement. In decylcyanobiphenyl, the temperature dependence for the bulk and surface processes is Arrhenius (in a limited temperature range above the melting point), except in Vycor, where it is a Vogel-Fulcher-Tamman dependence (over a much broader temperature range). In bulk and confined isopentylcyanobiphenyl, the molecular processes have a Vogel-Fulcher-Tamman dependence, whereas the surface processes have an Arrhenius one. Another effect is the acceleration of the rotation around the short molecular axis in confinement, and particularly in aerosil dispersions. This is a consequence of the disorder introduced in the liquid crystalline phase. The disorder drives the relaxation time towards a more isotropic value, resulting in an acceleration for the short axis rotation.

Confinement and βsub(p)-studies in neutral injection heated ASDEX plasmas

International Nuclear Information System (INIS)

Wagner, F.; Becker, G.; Behringer, K.; Campbell, D.; Eberhagen, A.; Engelhardt, W.; Fussmann, G.; Gehre, O.; Gernhardt, J.; Gierke, G. von; Haas, G.; Huang, M.; Karger, F.; Keilhacker, M.; Klueber, O.; Kornherr, M.; Lackner, K.; Lisitano, G.; Lister, G.G.; Mayer, H.M.; Meisel, D.; Mueller, E.R.; Murmann, H.; Niedermeyer, H.; Poschenrieder, W.; Rapp, H.; Roehr, H; Schneider, F.; Siller, G.; Speth, E.; Staebler, A.; Steuer, K.H.; Succi, S.; Venus, G.; Vollmer, O.

1983-03-01

Neutral injection experiments into limiter and divertor discharges in ASDEX are described with hydrogen and deuterium as working gas. Two operational regimes have been observed in neutral injection heated divertor discharges. One regime is characterized by deteriorated energy and particle confinement. The global energy confinement times are comparable to those of neutral injection heated limited discharges. Tthe other regime has particle and energy confinement times comparable to those of ohmic discharges with tausub(E) = 40 - 60 msec at beam powers up to 3.1 MW. This regime is further characterized by high βsub(p)-values comparable to the aspect ratio A (βsub(p) proportional 0.65 A), by good electron heating (etasub(e) proportional 2.5 x 10 13 eV cm -3 kW -1 ) and ion heating (etasub(i) proportional 4.2 x 10 13 eV cm -3 kW -1 ). In both regimes, tausub(E) increases with plasma current but there is hardly any variation with density. The differences in confinement and scaling to ohmic discharges seem to be caused by modifications of the electron loss channel. The high βsub(p)-regime develops at an injection power >=1.8 MW, anti nsub(e) >= 3 x 10 13 cm -3 and q >= 2.45, and is so far only observed in divertor discharges. There are indications that this may be due to the broad profiles with high edge temperatures which can develop in divertor discharges. An indication of broad current density profiles is given by the lack of sawtooth activity in these discharges. (orig.)

Plasma Confinement in the UCLA Electric Tokamak.

Science.gov (United States)

Taylor, Robert J.

2001-10-01

The main goal of the newly constructed large Electric Tokamak (R = 5 m, a = 1 m, BT 8 x 10^12 cm-3 when there is no MHD activity. The electron temperature, derived from the plasma conductivity is > 250 eV with a central electron energy confinement time > 350 msec in ohmic conditions. The sawteeth period is 50 msec. Edge plasma rotation is induced by plasma biasing via electron injection in an analogous manner to that seen in CCT(R.J. Taylor, M.L. Brown, B.D. Fried, H. Grote, J.R. Liberati, G.J. Morales, P. Pribyl, D. Darrow, and M. Ono. Phys. Rev Lett. 63 2365 1989.) and the neoclassical bifurcation is close to that described by Shaing et al(K.C. Shaing and E.C. Crume, Phys. Rev. Lett. 63 2369 (1989).). In the ohmic phase the confinement tends to be MHD limited. The ICRF heating eliminates the MHD disturbances. Under second harmonic heating conditions, we observe an internal confinement peaking characterized by doubling of the core density and a corresponding increase in the central electron temperature. Charge exchange data, Doppler data in visible H-alpha light, and EC radiation all indicate that ICRF heating works much better than expected. The major effort is focused on increasing the power input and controlling the resulting equilibrium. This task appears to be easy since our current pulses are approaching the 3 second mark without RF heating or current drive. Our initial experience with current profile control, needed for high beta plasma equilibrium, will be also discussed.

Current, temperature and confinement time scaling in toroidal reversed-field pinch experiments ZT-I and ZT-S

International Nuclear Information System (INIS)

Baker, D.A.; Burkhardt, L.C.; Di Marco, J.N.; Haberstich, A.; Hagenson, R.L.; Howell, R.B.; Karr, H.J.; Schofield, A.E.

1977-01-01

The scaling properties of a toroidal reversed-field Z pinch have been investigated over a limited range by comparing two experiments having conducting walls and discharge-tube minor diameters which differ by a factor of approximately 1.5. Both the confinement time of the plasma column and the electron temperature were found to increase about a factor of two with the increased minor diameter. Both the poloidal field diffusion and the decay of the toroidal reversed field were significantly reduced with the larger tube diameter. These results support the hypothesis that the loss of stability later in the discharge is caused by diffusion-induced deterioration of initially favourable plasma-field profiles to MHD unstable ones. This conclusion has been verified by stability analysis of the magnetic field profiles. Fusion reactor calculations show that small reactors are conceptually possible assuming good containment can be achieved for current densities approximately >20MAm -2 . (author)

Particle confinement and fueling effects on the Maryland spheromak

International Nuclear Information System (INIS)

Filuk, A.B.

1991-01-01

The spheromak plasma confinement concept provides the opportunity to study the evolution of a nearly force-free magnetic field configuration. The plasma currents and magnetic fields are produced self-consistently, making this type of device attractive as a possible fusion reactor. At present, spheromaks are observed to have poorer particle and magnetic confinement than expected from simple theory. The purpose of this study is to examine the role of plasma density in the decay of spheromaks produced in the Maryland Spheromak experiment. Density measurements are made with an interferometer and Langmuir probe, and results are correlated with those of other plasma diagnostics to understand the sources of plasma, the spheromak formation effects on the density, and the magnitude of particle loss during the spheromak decay. A power and particle balance computer model is constructed and applied to the spheromaks studied in order to assess the impact of high density and particle loss rate on the spheromak decay. The observations and model indicate that the decay of the spheromaks is at present dominated by impurity radiation loss. The model also predicts that high density and short particle confinement time play a critical role in the spheromak power balance when the impurity levels are reduced

Intermittent fluctuations in the Alcator C-Mod scrape-off layer for ohmic and high confinement mode plasmas

Science.gov (United States)

Garcia, O. E.; Kube, R.; Theodorsen, A.; LaBombard, B.; Terry, J. L.

2018-05-01

Plasma fluctuations in the scrape-off layer of the Alcator C-Mod tokamak in ohmic and high confinement modes have been analyzed using gas puff imaging data. In all cases investigated, the time series of emission from a single spatially resolved view into the gas puff are dominated by large-amplitude bursts, attributed to blob-like filament structures moving radially outwards and poloidally. There is a remarkable similarity of the fluctuation statistics in ohmic plasmas and in edge localized mode-free and enhanced D-alpha high confinement mode plasmas. Conditionally averaged waveforms have a two-sided exponential shape with comparable temporal scales and asymmetry, while the burst amplitudes and the waiting times between them are exponentially distributed. The probability density functions and the frequency power spectral densities are similar for all these confinement modes. These results provide strong evidence in support of a stochastic model describing the plasma fluctuations in the scrape-off layer as a super-position of uncorrelated exponential pulses. Predictions of this model are in excellent agreement with experimental measurements in both ohmic and high confinement mode plasmas. The stochastic model thus provides a valuable tool for predicting fluctuation-induced plasma-wall interactions in magnetically confined fusion plasmas.

Inertial confinement fusion target

International Nuclear Information System (INIS)

Bourdier, A.

2001-12-01

A simple, zero-dimensional model describing the temporal behaviour of an imploding-shell, magnetized fuel inertial confinement fusion target is formulated. The addition of a magnetic field to the fuel reduces thermal conduction losses. As a consequence, it might lead to high gains and reduce the driver requirements. This beneficial effect of the magnetic field on thermonuclear gains is confirmed qualitatively by the zero-dimensional model results. Still, the extent of the initial-condition space for which significant gains can occur is not, by far, as large as previously reported. One-dimensional CEA code simulations which confirm this results are also presented. Finally, we suggest to study the approach proposed by Hasegawa. In this scheme, the laser target is not imploded, and the life-time of the plasma can be very much increased. (author)

Fluorescence Microscopy of Nanochannel-Confined DNA.

Science.gov (United States)

Westerlund, Fredrik; Persson, Fredrik; Fritzsche, Joachim; Beech, Jason P; Tegenfeldt, Jonas O

2018-01-01

Stretching of DNA in nanoscale confinement allows for several important studies. The genetic contents of the DNA can be visualized on the single DNA molecule level and both the polymer physics of confined DNA and also DNA/protein and other DNA/DNA-binding molecule interactions can be explored. This chapter describes the basic steps to fabricate the nanostructures, perform the experiments and analyze the data.

Interactive optical trapping shows that confinement is a determinant of growth in a mixed yeast culture

DEFF Research Database (Denmark)

Arneborg, N.; Siegumfeldt, H.; Andersen, G.H.

2005-01-01

Applying a newly developed user-interactive optical trapping system, we controllably surrounded individual cells of one yeast species, Hanseniaspora uvarum, with viable cells of another yeast species, Saccharomyces cerevisiae, thus creating a confinement of the former. Growth of surrounded and non......-surrounded H. uvarum cells was followed under a microscope by determining their generation time. The average generation time of surrounded H. uvarum cells was 15% higher than that of non-surrounded cells thereby showing that the confinement imposed by viable S. cerevisiae cells on H. uvarum inhibits growth...

Confinement of pure electron plasmas in the Columbia Non-neutral Torus

International Nuclear Information System (INIS)

Berkery, John W.; Pedersen, Thomas Sunn; Kremer, Jason P.; Marksteiner, Quinn R.; Lefrancois, Remi G.; Hahn, Michael S.; Brenner, Paul W.

2007-01-01

The Columbia Non-neutral Torus (CNT) [T. S. Pedersen, J. P. Kremer, R. G. Lefrancois, Q. Marksteiner, N. Pomphrey, W. Reiersen, F. Dahlgreen, and X. Sarasola, Fusion Sci. Technol. 50, 372 (2006)] is a stellarator used to study non-neutral plasmas confined on magnetic surfaces. A detailed experimental study of confinement of pure electron plasmas in CNT is described here. Electrons are introduced into the magnetic surfaces by placing a biased thermionic emitter on the magnetic axis. As reported previously, the insulated rods holding this and other emitter filaments contribute to the radial transport by charging up negatively and creating ExB convective transport cells. A model for the rod-driven transport is presented and compared to the measured transport rates under a number of different conditions, finding good agreement. Neutrals also drive transport, and by varying the neutral pressure in the experiment, the effects of rod-driven and neutral-driven transport are separated. The neutral-driven electron loss rate scales linearly with neutral pressure. The neutral driven transport, presumably caused by electron-neutral collisions, is much greater than theoretical estimates for neoclassical diffusion in a classical stellarator with strong radial electric fields. In fact the confinement time is on the order of the electron-neutral collision time. Ion accumulation, electron attachment, and other effects are considered, but do not explain the observed transport rates

Behaviour of FRP confined concrete in square columns

OpenAIRE

Diego Villalón, Ana de; Arteaga Iriarte, Ángel; Fernandez Gomez, Jaime Antonio; Perera Velamazán, Ricardo; Cisneros, Daniel

2015-01-01

A significant amount of research has been conducted on FRP-confined circular columns, but much less is known about rectangular/square columns in which the effectiveness of confinement is much reduced. This paper presents the results of experimental investigations on low strength square concrete columns confined with FRP. Axial compression tests were performed on ten intermediate size columns. The tests results indicate that FRP composites can significantly improve the bearing capacity and duc...

Finite temperature approach to confinement

International Nuclear Information System (INIS)

Gave, E.; Jengo, R.; Omero, C.

1980-06-01

The finite temperature treatment of gauge theories, formulated in terms of a gauge invariant variable as in a Polyakov method, is used as a device for obtaining an effective theory where the confinement test takes the form of a correlation function. The formalism is discussed for the abelian CPsup(n-1) model in various dimensionalities and for the pure Yang-Mills theory in the limit of zero temperature. In the latter case a class of vortex like configurations of the effective theory which induce confinement correspond in particular to the instanton solutions. (author)

Pellet injection and toroidal confinement

International Nuclear Information System (INIS)

1989-12-01

The proceedings of a technical committee meeting on pellet injection and toroidal confinement, held in Gut Ising, Federal Republic of Germany, 24-26 October, 1988, are given in this report. Most of the major fusion experiments are using pellet injectors; these were reported at this meeting. Studies of confinement, which is favorably affected, impurity transport, radiative energy losses, and affects on the ion temperature gradient instability were given. Studies of pellet ablation and effects on plasma profiles were presented. Finally, several papers described present and proposed injection guns. Refs, figs and tabs

INERT Atmosphere confinement operability test procedure

International Nuclear Information System (INIS)

RISENMAY, H.R.

1999-01-01

This Operability Test Procedure (OTP) provides instructions for testing operability of the Inert Atmosphere Confinement (IAC). The Inert Atmosphere Confinement was designed and built for opening cans of metal items that might have hydrided surfaces. Unreviewed Safety Question (USQ) PFP-97-005 addresses the discovery of suspected plutonium hydride forming on plutonium metal currently stored in the Plutonium Finishing Plant vaults. Plutonium hydride reacts quickly with air, liberating energy. The Inert Atmosphere Confinement was designed to prevent this sudden liberation of energy by opening the material in an inert argon atmosphere instead of the normal glovebox atmosphere. The IAC is located in glovebox HC-21A, room 230B of the 234-5Z Building at the Plutonium Finishing Plant (PFP) in the 200-West Area of the Hanford Site

Collective oscillations and coupled modes in confined microfluidic droplet arrays

Science.gov (United States)

Schiller, Ulf D.; Fleury, Jean-Baptiste; Seemann, Ralf; Gompper, Gerhard

Microfluidic droplets have a wide range of applications ranging from analytic assays in cellular biology to controlled mixing in chemical engineering. Ensembles of microfluidic droplets are interesting model systems for non-equilibrium many-body phenomena. When flowing in a microchannel, trains of droplets can form microfluidic crystals whose dynamics are governed by long-range hydrodynamic interactions and boundary effects. In this contribution, excitation mechanisms for collective waves in dense and confined microfluidic droplet arrays are investigated by experiments and computer simulations. We demonstrate that distinct modes can be excited by creating specific `defect' patterns in flowing droplet trains. While longitudinal modes exhibit a short-lived cascade of pairs of laterally displacing droplets, transversely excited modes form propagating waves that behave like microfluidic phonons. We show that the confinement induces a coupling between longitudinal and transverse modes. We also investigate the life time of the collective oscillations and discuss possible mechanisms for the onset of instabilities. Our results demonstrate that microfluidic phonons can exhibit effects beyond the linear theory, which can be studied particularly well in dense and confined systems. This work was supported by Deutsche Forschungsgemeinschaft under Grant No. SE 1118/4.

Deep processes in non-relativistic confining potentials

International Nuclear Information System (INIS)

Fishbane, P.M.; Grisaru, M.T.

1978-01-01

The authors study deep inelastic and hard scattering processes for non-relativistic particles confined in deep potentials. The mechanisms by which the effects of confinement disappear and the particles scatter as if free are useful in understanding the analogous results for a relativistic field theory. (Auth.)

Potential Role of Inorganic Confined Environments in Prebiotic Phosphorylation.

Science.gov (United States)

Dass, Avinash Vicholous; Jaber, Maguy; Brack, André; Foucher, Frédéric; Kee, Terence P; Georgelin, Thomas; Westall, Frances

2018-03-05

A concise outlook on the potential role of confinement in phosphorylation and phosphate condensation pertaining to prebiotic chemistry is presented. Inorganic confinement is a relatively uncharted domain in studies concerning prebiotic chemistry, and even more so in terms of experimentation. However, molecular crowding within confined dimensions is central to the functioning of contemporary biology. There are numerous advantages to confined environments and an attempt to highlight this fact, within this article, has been undertaken, keeping in context the limitations of aqueous phase chemistry in phosphorylation and, to a certain extent, traditional approaches in prebiotic chemistry.

Summary on inertial confinement fusion

International Nuclear Information System (INIS)

Meyer-Ter-Vehn, J.

1995-01-01

Highlights on inertial confinement during the fifteenth international conference on plasma physics and controlled nuclear fusion are briefly summarized. Specifically the following topics are discussed: the US National Ignition Facility presently planned by the US Department of Energy; demonstration of diagnostics for hot spot formation; declassification of Hohlraum target design; fusion targets, in particular, the Hohlraum target design for the National Ignition Facility (NIF), Hohlraum experiments, direct drive implosions, ablative Rayleigh-Taylor instabilities, laser imprinting (of perturbations by the laser on the laser target surface), hot spot formation and mixing, hot spot implosion experiments at Lawrence Livermore National Laboratory, Livermore, USA, time resolving hot spot dynamics at the Institute of Laser Engineering (ILE), Osaka, Japan, laser-plasma interaction

Effect of prepartum exercise, pasture turnout, or total confinement on hoof health.

Science.gov (United States)

Black, R A; van Amstel, S R; Krawczel, P D

2017-10-01

Lameness is a major welfare concern in the dairy industry, and access to physical activity during the dry period may improve hoof health. The objective of this study was to determine the effects of forced exercise, pasture turnout, or total confinement of dry cows on horn growth and wear and sole thickness. Twenty-nine primiparous and 31 multiparous, pregnant, nonlactating Holstein (n = 58) and Jersey-Holstein crossbred (n = 2) dairy cows were assigned to either total confinement (n = 20), exercise (n = 20), or pasture (n = 20) treatments at dry-off using rolling enrollment from January to November 2015. Cows were managed with a 60-d dry period (58.5 ± 5.4 d) divided into far-off (dry-off to 2 wk before parturition) and close-up periods (2 wk before projected parturition). Cows were housed in a naturally ventilated, 4-row freestall barn at the University of Tennessee's Little River Animal and Environmental Unit (Walland, TN) with concrete flooring and deep-bedded sand freestalls. Cows assigned to confinement remained in the housing pen. Exercise cows were walked for a targeted 1.5 h at 3.25 km/h, 5 times/wk until calving. Pasture cows were turned out for a targeted 1.5 h, 5 times/wk until calving. Hoof growth and wear and sole thickness of the rear hooves were measured on d 2 and 44, relative to dry-off. Data were analyzed using the MIXED procedure of SAS (SAS Institute Inc., Cary, NC). Cranial and caudal horn wear was greater for exercise cows than confinement and pasture cows. Exercise cows experienced more equal rates of horn growth and wear cranially. Confined cows tended to increase sole thickness from d 2 to 44, relative to dry-off. Frequent, short duration exercise on concrete did not impair the hoof health of late-gestation dry cows. Further, exercise may improve overall hoof health, potentially improving cow welfare. Copyright © 2017 American Dairy Science Association. Published by Elsevier Inc. All rights reserved.

Qualitative quark confinement

International Nuclear Information System (INIS)

Jackson, T.L.

1976-01-01

The infrared limit in asymptotically free non-abelian gauge theories using recently developed non-perturbative methods which allow derivation of zero momentum theorems for Green's functions and vertices is described. These low-energy theorems are compared to the infrared behavior predicted from the renormalization group equation when the existence of an infrared fixed point is assumed. A set of objects is exhibited whose low energy theorems violate the scaling behavior predicted by the renormalization group. This shows that the assumed fixed point cannot exist and that in the Landau gauge the effective charge becomes infinite in the infrared. Qualitatively this implies that as an attempt is made to separate elementary quanta the interaction between the quanta becomes arbitrarily strong. This indicates at least that the theories studied are capable of color confinement. Results are true only for theories with large numbers of quarks. This opens the possibility that large numbers of quarks are actually necessary for confinement

Greater-confinement disposal

International Nuclear Information System (INIS)

Trevorrow, L.E.; Schubert, J.P.

1989-01-01

Greater-confinement disposal (GCD) is a general term for low-level waste (LLW) disposal technologies that employ natural and/or engineered barriers and provide a degree of confinement greater than that of shallow-land burial (SLB) but possibly less than that of a geologic repository. Thus GCD is associated with lower risk/hazard ratios than SLB. Although any number of disposal technologies might satisfy the definition of GCD, eight have been selected for consideration in this discussion. These technologies include: (1) earth-covered tumuli, (2) concrete structures, both above and below grade, (3) deep trenches, (4) augered shafts, (5) rock cavities, (6) abandoned mines, (7) high-integrity containers, and (8) hydrofracture. Each of these technologies employ several operations that are mature,however, some are at more advanced stages of development and demonstration than others. Each is defined and further described by information on design, advantages and disadvantages, special equipment requirements, and characteristic operations such as construction, waste emplacement, and closure

Stellarator approach to toroidal plasma confinement

International Nuclear Information System (INIS)

Johnson, J.L.

1981-12-01

An overview is presented of the development and current status of the stellarator approach to controlled thermonuclear confinement. Recent experimental, theoretical, and systems developments have made this concept a viable option for the evolution of the toroidal confinement program. Some experimental study of specific problems associated with departure from two-dimensional symmetry must be undertaken before the full advantages and opportunities of steady-state, net-current-free operation can be realized

Dynamic response of materials on subnanosecond time scales, and beryllium properties for inertial confinement fusion

International Nuclear Information System (INIS)

Swift, Damian C.; Tierney, Thomas E.; Luo Shengnian; Paisley, Dennis L.; Kyrala, George A.; Hauer, Allan; Greenfield, Scott R.; Koskelo, Aaron C.; McClellan, Kenneth J.; Lorenzana, Hector E.; Kalantar, Daniel; Remington, Bruce A.; Peralta, Pedro; Loomis, Eric

2005-01-01

During the past few years, substantial progress has been made in developing experimental techniques capable of investigating the response of materials to dynamic loading on nanosecond time scales and shorter, with multiple diagnostics probing different aspects of the behavior. These relatively short time scales are scientifically interesting because plastic flow and phase changes in common materials with simple crystal structures--such as iron--may be suppressed, allowing unusual states to be induced and the dynamics of plasticity and polymorphism to be explored. Loading by laser-induced ablation can be particularly convenient: this technique has been used to impart shocks and isentropic compression waves from ∼1 to 200 GPa in a range of elements and alloys, with diagnostics including line imaging surface velocimetry, surface displacement (framed area imaging), x-ray diffraction (single crystal and polycrystal), ellipsometry, and Raman spectroscopy. A major motivation has been the study of the properties of beryllium under conditions relevant to the fuel capsule in inertial confinement fusion: magnetically driven shock and isentropic compression shots at Z were used to investigate the equation of state and shock melting characteristics, complemented by laser ablation experiments to investigate plasticity and heterogeneous response from the polycrystalline microstructure. These results will help to constrain acceptable tolerances on manufacturing, and possible loading paths, for inertial fusion ignition experiments at the National Ignition Facility. Laser-based techniques are being developed further for future material dynamics experiments, where it should be possible to obtain high quality data on strength and phase changes up to at least 1 TPa

Curvature of random walks and random polygons in confinement

International Nuclear Information System (INIS)

Diao, Y; Ernst, C; Montemayor, A; Ziegler, U

2013-01-01

The purpose of this paper is to study the curvature of equilateral random walks and polygons that are confined in a sphere. Curvature is one of several basic geometric properties that can be used to describe random walks and polygons. We show that confinement affects curvature quite strongly, and in the limit case where the confinement diameter equals the edge length the unconfined expected curvature value doubles from π/2 to π. To study curvature a simple model of an equilateral random walk in spherical confinement in dimensions 2 and 3 is introduced. For this simple model we derive explicit integral expressions for the expected value of the total curvature in both dimensions. These expressions are functions that depend only on the radius R of the confinement sphere. We then show that the values obtained by numeric integration of these expressions agrees with numerical average curvature estimates obtained from simulations of random walks. Finally, we compare the confinement effect on curvature of random walks with random polygons. (paper)

[Analysis of Cr in soil by LIBS based on conical spatial confinement of plasma].

Science.gov (United States)

Lin, Yong-Zeng; Yao, Ming-Yin; Chen, Tian-Bing; Li, Wen-Bing; Zheng, Mei-Lan; Xu, Xue-Hong; Tu, Jian-Ping; Liu, Mu-Hua

2013-11-01

The present study is to improve the sensitivity of detection and reduce the limit of detection in detecting heavy metal of soil by laser induced breakdown spectroscopy (LIBS). The Cr element of national standard soil was regarded as the research object. In the experiment, a conical cavity with small diameter end of 20 mm and large diameter end of 45 mm respectively was installed below the focusing lens near the experiment sample to mainly confine the signal transmitted by plasma and to some extent to confine the plasma itself in the LIBS setup. In detecting Cr I 425.44 nm, the beast delay time gained from experiment is 1.3 micros, and the relative standard deviation is below 10%. Compared with the setup of non-spatial confinement, the spectral intensity of Cr in the soil sample was enhanced more than 7%. Calibration curve was established in the Cr concentration range from 60 to 400 microg x g(-1). Under the condition of spatial confinement, the liner regression coefficient and the limit of detection were 0.997 71 and 18.85 microg x g(-1) respectively, however, the regression coefficient and the limit of detection were 0.991 22 and 36.99 microg x g(-1) without spatial confinement. So, this shows that conical spatial confinement can/improve the sensitivity of detection and enhance the spectral intensity. And it is a good auxiliary function in detecting Cr in the soil by laser induced breakdown spectroscopy.

Long-Pulse Operation and High-Energy Particle Confinement Study in ICRF Heating of LHD

International Nuclear Information System (INIS)

Mutoh, Takashi; Kumazawa, Ryuhei; Seki, Tetsuo

2004-01-01

Long-pulse operation and high-energy particle confinement properties were studied using ion cyclotron range of frequency (ICRF) heating for the Large Helical Device. For the minority-ion mode, ions with energies up to 500 keV were observed by concentrating the ICRF heating power near the plasma axis. The confinement of high-energy particles was studied using the power-modulation technique. This confirmed that the confinement of high-energy particles was better with the inward-shifted configuration than with the normal configuration. This behavior was the same for bulk plasma confinement. Long-pulse operation for more than 2 min was achieved during the experimental program in 2002. This was mainly due to better confinement of the helically trapped particles and accumulation of fewer impurities in the region of the plasma core, in conjunction with substantial hardware improvements. Currently, the plasma operation time is limited by an unexpected density rise due to outgassing from the chamber materials. The temperature of the local carbon plates of the divertor exceeded 400 deg, C, and a charge-coupled device camera observed the hot spots. The hot spot pattern was well explained by a calculation of the accelerated-particle orbits, and those accelerated particles came from outside the plasma near the ICRF antenna

Percolating cluster of center vortices and confinement

International Nuclear Information System (INIS)

Gliozzi, Ferdinando; Panero, Marco; Provero, Paolo

2003-01-01

We study the role of percolating clusters of center vortices in configurations of an Ising gauge theory in 3D. It is known that low energy features of gauge theories can be described in terms of an 'effective string picture', and that confinement properties are associated with topologically non-trivial configurations. We focus our attention upon percolating clusters of center vortices, and present numerical evidence for the fact that these objects play a preminent role in confinement phenomenon, since their removal sweeps off confinement altogether. Moreover, numerical simulations show that the string fluctuations, and in particular the Mischer term, are completely encoded in the percolating cluster

Quantum confinement effect in cheese like silicon nano structure fabricated by metal induced etching

Energy Technology Data Exchange (ETDEWEB)

Saxena, Shailendra K., E-mail: phd1211512@iiti.ac.in; Sahu, Gayatri; Sagdeo, Pankaj R.; Kumar, Rajesh [Material Research Laboratory, Discipline of Physics & MSEG, Indian Institute of Technology Indore, Madhya Pradesh-452017 (India)

2015-08-28

Quantum confinement effect has been studied in cheese like silicon nano-structures (Ch-SiNS) fabricated by metal induced chemical etching using different etching times. Scanning electron microscopy is used for the morphological study of these Ch-SiNS. A visible photoluminescence (PL) emission is observed from the samples under UV excitation at room temperature due to quantum confinement effect. The average size of Silicon Nanostructures (SiNS) present in the samples has been estimated by bond polarizability model using Raman Spectroscopy from the red-shift observed from SiNSs as compared to its bulk counterpart. The sizes of SiNS present in the samples decreases as etching time increase from 45 to 75 mintunes.

Measurement of inertial confinement fusion reaction rate

International Nuclear Information System (INIS)

Peng Xiaoshi; Wang Feng; Tang Daorun; Liu Shenye; Huang Tianxuan; Liu Yonggang; Xu Tao; Chen Ming; Mei Yu

2011-01-01

Fusion reaction rate is an important parameter for measuring compression during the implosion in inertial confinement fusion experiment. We have developed a system for fusion reaction history measurement with high temporal resolution. The system is composed of plastic scintillator and nose cone, optical system and streak camera. We have applied this system on the SG-III prototype for fusion reaction rate measuring. For the first time, fusion reaction rate history have been measured for deuterium-tritium filled targets with neutrons yields about 10 10 . We have analyzed possible influence factor during fusion reaction rate measuring. It indicates that the instrument measures fusion reaction bang time at temporal resolutions as low as 30 ps.(authors)

New steady-state quiescent high-confinement plasma in an experimental advanced superconducting tokamak.

Science.gov (United States)

Hu, J S; Sun, Z; Guo, H Y; Li, J G; Wan, B N; Wang, H Q; Ding, S Y; Xu, G S; Liang, Y F; Mansfield, D K; Maingi, R; Zou, X L; Wang, L; Ren, J; Zuo, G Z; Zhang, L; Duan, Y M; Shi, T H; Hu, L Q

2015-02-06

A critical challenge facing the basic long-pulse high-confinement operation scenario (H mode) for ITER is to control a magnetohydrodynamic (MHD) instability, known as the edge localized mode (ELM), which leads to cyclical high peak heat and particle fluxes at the plasma facing components. A breakthrough is made in the Experimental Advanced Superconducting Tokamak in achieving a new steady-state H mode without the presence of ELMs for a duration exceeding hundreds of energy confinement times, by using a novel technique of continuous real-time injection of a lithium (Li) aerosol into the edge plasma. The steady-state ELM-free H mode is accompanied by a strong edge coherent MHD mode (ECM) at a frequency of 35-40 kHz with a poloidal wavelength of 10.2 cm in the ion diamagnetic drift direction, providing continuous heat and particle exhaust, thus preventing the transient heat deposition on plasma facing components and impurity accumulation in the confined plasma. It is truly remarkable that Li injection appears to promote the growth of the ECM, owing to the increase in Li concentration and hence collisionality at the edge, as predicted by GYRO simulations. This new steady-state ELM-free H-mode regime, enabled by real-time Li injection, may open a new avenue for next-step fusion development.

FRP-Confined Recycled Coarse Aggregate Concrete: Experimental Investigation and Model Comparison

Directory of Open Access Journals (Sweden)

Yingwu Zhou

2016-10-01

Full Text Available The in situ application of recycled aggregate concrete (RAC is of great significance in environmental protection and construction resources sustainability. However, it has been limited to nonstructural purposes due to its poor mechanical performance. External confinement using steel tubes and fiber-reinforced polymer (FRP can significantly improve the mechanical performance of RAC and thus the first-ever study on the axial compressive behavior of glass FRP (GFRP-confined RAC was recently reported. To have a full understanding of FRP-confined RAC, this paper has extended the type of FRP and presents a systematic experimental study on the axial compressive performance of carbon FRP (CFRP-confined RAC. The mechanical properties of CFRP-confined RAC from the perspective of the failure mode, ultimate strength and strain, and stress–strain relationship responses were analyzed. Integrated with existing experimental data of FRP-confined RAC, the paper compiles a database for the mechanical properties of FRP-confined RAC. Based on the database, the effects of FRP type (i.e., GFRP and CFRP and the replacement ratio of recycled coarse aggregate were investigated. The results indicated that the stress–stain behavior of FRP-confined RAC depended heavily on the unconfined concrete strength and the FRP confining pressure instead of the replacement ratio. Therefore, this study adopted eleven high-performance ultimate strength and strain models developed for FRP-confined normal aggregate concrete (NAC to predict the mechanical properties of FRP-confined RAC. All the predictions had good agreement with the test results, which further confirmed similar roles played by FRP confinement in improving the mechanical properties of RAC and improving those of NAC. On this basis, this paper finally recommended a stress–strain relationship model for FRP-confined RAC.

Structure and spectra of a confined HeH molecule

International Nuclear Information System (INIS)

Lo, J M H; Klobukowski, M; Bielinska-Wacz, D; Schreiner, E W S; Diercksen, G H F

2006-01-01

The influence of spatial confinement on the structure and spectra of the Rydberg HeH molecule is analysed at the level of the variational full configuration interaction approach. The confining potential is assumed to have cylindrical symmetry, with the symmetry axis of the potential overlapping with the molecular bond. In the direction perpendicular to the axis quadratic dependence of the potential on the electron coordinates is assumed. The influence of the confining potential on the form of the potential energy curves (in particular on the bond lengths), on the electronic spectra and on the ionization due to the confinement is studied in detail

The cruel and unusual phenomenology of solitary confinement

OpenAIRE

Shaun eGallagher; Shaun eGallagher; Shaun eGallagher

2014-01-01

What happens when subjects are deprived of intersubjective contact? This paper looks closely at the phenomenology and psychology of one example of that deprivation: solitary confinement. It also puts the phenomenology and psychology of solitary confinement to use in the legal context. Not only is there no consensus on whether solitary confinement is a cruel and unusual punishment, there is no consensus on the definition of the term ‘cruel’ in the use of that legal phrase. I argue that we ...

Reproduction, mastitis, and body condition of seasonally calved Holstein and Jersey cows in confinement or pasture systems.

Science.gov (United States)

Washburn, S P; White, S L; Green, J T; Benson, G A

2002-01-01

Dairy cows in confinement and pasture-based feeding systems were compared across four spring-calving and three fall-calving replicates for differences in reproduction, mastitis, body weights, and body condition scores. Feeding systems and replicates included both Jersey and Holstein cows. Cows in confinement were fed a total mixed ration, and cows on pasture were supplemented with concentrates and provided baled hay or haylage when pasture supply was limiting. Breeding periods were for 75 d in spring or fall. Reproductive performance did not differ significantly due to feeding system or season. Jerseys had higher conception rates (59.6 vs. 49.5 +/- 3.3%) and higher percentages of cows pregnant in 75 d (78.1 vs. 57.9 +/- 3.9%) than Holsteins. Cows in confinement had 1.8 times more clinical mastitis and eight times the rate of culling for mastitis than did cows on pasture. Jerseys had half as many clinical cases of mastitis per cow as Holsteins. Only 41 +/- 5% of confinement Holsteins remained for a subsequent lactation, starting within the defined calving season compared with 51 +/- 5% of pastured Holsteins and 71 and 72 +/- 5% of Jerseys, respectively. Body weights and condition scores were generally higher for confinement cows than pastured cows, and Jerseys had higher condition scores and lower body weights than Holsteins. In summary, pastured cows had fewer clinical cases of mastitis, lower body condition scores, and lower body weights than confinement cows. Holsteins were less likely to rebreed, had more mastitis, higher culling rates, and lower body condition scores than Jerseys.

Injection, compression and confinement of electrons in a magnetic mirror

International Nuclear Information System (INIS)

Fisher, A.

1975-01-01

A Helmholtz coil configuration has been constructed where the magnetic field can be increased to about 10 kGauss in 20 μsec. Electrons are injected from a hot tantalum filament between two plates across which a potential of about 5 keV is applied. The electric field E is perpendicular to the magnetic field B so that the direction of the E x B drift is radial--into the magnetic mirror. About 10 14 electrons were injected and about 10 13 electrons were trapped. The initial electron energy was about 5 keV and after compression 500 keV x-rays were observed. The confinement time is very sensitive to vacuum. Confinement times of milliseconds and good compression were observed at vacuum of 5.10 -5 torr or less. Above 5.10 -5 torr there was no trapping or compression. After a compressed ring of electrons was formed, it was released by a pulse applied to one of the Helmholtz coils that reduced the field. Ejection of the electron ring was observed by x-ray measurements

Masonry Columns Confined by Steel Fiber Composite Wraps

Directory of Open Access Journals (Sweden)

Marco Corradi

2011-01-01

Full Text Available The application of steel fiber reinforced polymer (SRP as a means of increasing the capacity of masonry columns is investigated in this study. The behavior of 23 solid-brick specimens that are externally wrapped by SRP sheets in low volumetric ratios is presented. The specimens are subjected to axial monotonic load until failure occurs. Two widely used types of masonry columns of differing square cross-sections were tested in compression (square and octagonal cross-sections. It is concluded that SRP-confined masonry behaves very much like fiber reinforced polymers (FRP-confined masonry. Confinement increases both the load-carrying capacity and the deformability of masonry almost linearly with average confining stress. A comparative analysis between experimental and theoretical values computed in compliance with the Italian Council of Research (CNR was also developed.

Confined catalysis under two-dimensional materials

OpenAIRE

Li, Haobo; Xiao, Jianping; Fu, Qiang; Bao, Xinhe

2017-01-01

Small spaces in nanoreactors may have big implications in chemistry, because the chemical nature of molecules and reactions within the nanospaces can be changed significantly due to the nanoconfinement effect. Two-dimensional (2D) nanoreactor formed under 2D materials can provide a well-defined model system to explore the confined catalysis. We demonstrate a general tendency for weakened surface adsorption under the confinement of graphene overlayer, illustrating the feasible modulation of su...

Chiral symmetry breaking and confinement - solutions of relativistic wave equations

International Nuclear Information System (INIS)

Murugesan, P.

1983-01-01

In this thesis, an attempt is made to explore the question whether confinement automatically leads to chiral symmetry breaking. While it should be accepted that chiral symmetry breaking manifests in nature in the absence of scalar partners of pseudoscalar mesons, it does not necessarily follow that confinement should lead to chiral symmetry breaking. If chiral conserving forces give rise to observed spectrum of hadrons, then the conjuncture that confinement is responsible for chiral symmetry breaking is not valid. The method employed to answer the question whether confinement leads to chiral symmetry breaking or not is to solve relativistic wave equations by introducing chiral conserving as well as chiral breaking confining potentials and compare the results with experimental observations. It is concluded that even though chiral symmetry is broken in nature, confinement of quarks need not be the cause of it

Modelling of HTR Confinement Behaviour during Accidents Involving Breach of the Helium Pressure Boundary

Directory of Open Access Journals (Sweden)

Joan Fontanet

2009-01-01

Full Text Available Development of HTRs requires the performance of a thorough safety study, which includes accident analyses. Confinement building performance is a key element of the system since the behaviour of aerosol and attached fission products within the building is of an utmost relevance in terms of the potential source term to the environment. This paper explores the available simulation capabilities (ASTEC and CONTAIN codes and illustrates the performance of a postulated HTR vented confinement under prototypical accident conditions by a scoping study based on two accident sequences characterized by Helium Pressure Boundary breaches, a small and a large break. The results obtained indicate that both codes predict very similar thermal-hydraulic responses of the confinement both in magnitude and timing. As for the aerosol behaviour, both codes predict that most of the inventory coming into the confinement is eventually depleted on the walls and only about 1% of the aerosol dust is released to the environment. The crosscomparison of codes states that largest differences are in the intercompartmental flows and the in-compartment gas composition.

First results on dense plasma confinement at the multimirror open trap GOL-3-II

International Nuclear Information System (INIS)

Koidan, V.S.; Arzhannikov, A.V.; Astrelin, V.T.

2001-01-01

First results of experiments on plasma confinement in multimirror open trap GOL-3-II are presented. This facility is an open trap with total length of 17 m intended for confinement of a relatively dense (10 15 -10 17 cm -3 ) plasma in axially-symmetrical magnetic system. The plasma heating is provided by a high-power electron beam (1 MeV, 30 kA, 8 ms, 200 kJ). New phase of the experiments is aimed to confinement of high-β thermalized plasma. Two essential modifications of the facility have been done. First, plasma column was separated by vacuum sections from the beam accelerator and exit beam receiver. Second, the magnetic field on part of the solenoid was reconfigured into multimirror system with H max /H min ∼1.5 and 22 cm cell length. Results of the experiments at modified configuration of the device indicate that the confinement time of the plasma with n e ∼(0, 5/5)·10 15 cm -3 and T e ∼1 keV increases more than order of magnitude. (author)

CONFINEMENT OF HIGH TEMPERATURE PLASMA

Science.gov (United States)

Koenig, H.R.

1963-05-01

The confinement of a high temperature plasma in a stellarator in which the magnetic confinement has tended to shift the plasma from the center of the curved, U-shaped end loops is described. Magnetic means are provided for counteracting this tendency of the plasma to be shifted away from the center of the end loops, and in one embodiment this magnetic means is a longitudinally extending magnetic field such as is provided by two sets of parallel conductors bent to follow the U-shaped curvature of the end loops and energized oppositely on the inside and outside of this curvature. (AEC)

Energy confinement in Ohmic H-mode in TUMAN-3M

International Nuclear Information System (INIS)

Andrejko, M.V.; Askinazi, L.G.; Golant, V.E.; Kornev, V.A.; Lebedev, S.V.; Levin, L.S.; Tukachinsky, A.S.

1997-01-01

The spontaneous transition from Ohmically heated limiter discharges into the regime with improved confinement termed as ''Ohmic H-mode'' has been investigated in ''TUMAN-3''. The typical signatures of H-mode in tokamaks with powerful auxiliary heating have been observed: sharp drop of D α radiation with simultaneous increase in the electron density and stored energy, suppression of the density fluctuations and establishing the steep gradient near the periphery. In 1994 new vacuum vessel had been installed in TUMAN-3 tokamak. The vessel has the same sizes as old one (R 0 =0.55 m, a 1 =0.24 m). New vessel was designed to reduce mechanical stresses in the walls during B T ramp phase of a shot. Therefore modified device - TUMAN-3M is able to produce higher B T and I p , up to 2 T and 0.2 MA respectively. During first experimental run device was operated in Ohmic Regime. In these experiments the possibility to achieve Ohmic H-mode was studied. The study of the parametric dependencies of the energy confinement time in both OH and Ohmic H-mode was performed. In Ohmic H-mode strong dependencies of τ E on plasma current and on input power and weak dependence on density were found. Energy confinement time in TUMAN-3/TUMAN-3M Ohmic H-mode has revealed good agreement with JET/DIII-D/ASDEX scaling for ELM-free H-mode, resulting in very long τ E at the high plasma current discharges. (author)

Glass transition and relaxation dynamics of propylene glycol-water solutions confined in clay

Science.gov (United States)

Elamin, Khalid; Björklund, Jimmy; Nyhlén, Fredrik; Yttergren, Madeleine; Mârtensson, Lena; Swenson, Jan

2014-07-01

The molecular dynamics of aqueous solutions of propylene glycol (PG) and propylene glycol methylether (PGME) confined in a two-dimensional layer-structured Na-vermiculite clay has been studied by broadband dielectric spectroscopy and differential scanning calorimetry. As typical for liquids in confined geometries the intensity of the cooperative α-relaxation becomes considerably more suppressed than the more local β-like relaxation processes. In fact, at high water contents the calorimetric glass transition and related structural α-relaxation cannot even be observed, due to the confinement. Thus, the intensity of the viscosity related α-relaxation is dramatically reduced, but its time scale as well as the related glass transition temperature Tg are for both systems only weakly influenced by the confinement. In the case of the PGME-water solutions it is an important finding since in the corresponding bulk system a pronounced non-monotonic concentration dependence of the glass transition related dynamics has been observed due to the growth of hydrogen bonded relaxing entities of water bridging between PGME molecules [J. Sjöström, J. Mattsson, R. Bergman, and J. Swenson, Phys. Chem. B 115, 10013 (2011)]. The present results suggest that the same type of structural entities are formed in the quasi-two-dimensional space between the clay platelets. It is also observed that the main water relaxation cannot be distinguished from the β-relaxation of PG or PGME in the concentration range up to intermediate water contents. This suggests that these two processes are coupled and that the water molecules affect the time scale of the β-relaxation. However, this is most likely true also for the corresponding bulk solutions, which exhibit similar time scales of this combined relaxation process below Tg. Finally, it is found that at higher water contents the water relaxation does not merge with, or follow, the α-relaxation above Tg, but instead crosses the �

The cruel and unusual phenomenology of solitary confinement

OpenAIRE

Gallagher, Shaun

2014-01-01

What happens when subjects are deprived of intersubjective contact? This paper looks closely at the phenomenology and psychology of one example of that deprivation: solitary confinement. It also puts the phenomenology and psychology of solitary confinement to use in the legal context. Not only is there no consensus on whether solitary confinement is a “cruel and unusual punishment,” there is no consensus on the definition of the term “cruel” in the use of that legal phrase. I argue that we ca...

Exercise as Countermeasure for Decrements of Performance and Mood During Long-Term Confinement

Science.gov (United States)

Schneider, Stefan; Piacentini, Maria F.; Meeusen, Romain; Brummer, Vera; Struder, Heiko K.

2008-06-01

In order to prepare for crewed exploratory missions to Moon and Mars, currently ESA is participating in two isolation studies, MARS 500 and on the antarctis station CONCORDIA. The aim of the present study is to identify exercise as a countermeasure to confinement addicted changes in mood. It is planned (1) to look at influences of exercise on the serotonergic system, which is known to have mood regulating effects and (2) to record changes in brain cortical activity due to exercise. Mood and performance tests will be carried out several times during the confinement. We hypothesize that impairments in mood due to the isolated and confined environment together with a lack of physical exercise lead to decreases in mental and perceptual motor performance whereas physical exercise linked with an activation of the serotonergic system will improve mood and therefore performance irrespectively of the environmental restrictions.

Power requirements for superior H-mode confinement on Alcator C-Mod: experiments in support of ITER

International Nuclear Information System (INIS)

Hughes, J.W.; Reinke, M.L.; Terry, J.L.; Brunner, D.; Greenwald, M.; Hubbard, A.E.; LaBombard, B.; Lipschultz, B.; Ma, Y.; Wolfe, S.; Wukitch, S.J.; Loarte, A.

2011-01-01

Power requirements for maintaining sufficiently high confinement (i.e. normalized energy confinement time H 98 ≥ 1) in H-mode and its relation to H-mode threshold power scaling, P th , are of critical importance to ITER. In order to better characterize these power requirements, recent experiments on the Alcator C-Mod tokamak have investigated H-mode properties, including the edge pedestal and global confinement, over a range of input powers near and above P th . In addition, we have examined the compatibility of impurity seeding with high performance operation, and the influence of plasma radiation and its spatial distribution on performance. Experiments were performed at 5.4 T at ITER relevant densities, utilizing bulk metal plasma facing surfaces and an ion cyclotron range of frequency waves for auxiliary heating. Input power was scanned both in stationary enhanced D α (EDA) H-modes with no large edge localized modes (ELMs) and in ELMy H-modes in order to relate the resulting pedestal and confinement to the amount of power flowing into the scrape-off layer, P net , and also to the divertor targets. In both EDA and ELMy H-mode, energy confinement is generally good, with H 98 near unity. As P net is reduced to levels approaching that in L-mode, pedestal temperature diminishes significantly and normalized confinement time drops. By seeding with low-Z impurities, such as Ne and N 2 , high total radiated power fractions are possible, along with substantial reductions in divertor heat flux (>4x), all while maintaining H 98 ∼ 1. When the power radiated from the confined versus unconfined plasma is examined, pedestal and confinement properties are clearly seen to be an increasing function of P net , helping to unify the results with those from unseeded H-modes. This provides increased confidence that the power flow across the separatrix is the correct physics basis for ITER extrapolation. The experiments show that P net /P th of one or greater is likely to lead to H

'Tied down'- the process of becoming bedridden through gradual local confinement.

Science.gov (United States)

Zegelin, Angelika

2008-09-01

To raise awareness of the process of being bedridden, to create knowledge about the different causes and types of being bedridden, to highlight what exactly constitutes being bedridden, to describe which factors influence being bedridden. Being bedridden is a common phenomenon in nursing. However, there is no solid base of knowledge on reasons, types, development of and coping with this situation. The concept of being bedridden is applied in an arbitrary manner and the state of being bedridden is far from being clearly defined. A literature review revealed that only pathophysiological effects of this state are sufficiently explained. The aim of this study was to gain knowledge of the development of being confined to bed. Data collection and analysis were performed by using a Grounded Theory approach as developed by Strauss and Corbin. Thirty-two interviews with older, bedridden people were conducted. They were asked about their perspective on and their experience of the development of being confined to bed. Half of the interviewees lived in a nursing home, the others were cared for at home. 'Gradual local confinement' was identified as the core category. Becoming bedridden is a slow process by which the person is increasingly confined to one location. This development is related to an increasing need for support and to negative consequences, such as a pathology of immobility, narrowing of interests and loss of time. These consequences again are responsible for a downward spiral development. The study is the first research on the topic of being bedridden; no research in this field had been done before. There are some research results on bedrest, based on a purely medical perspective. The problem of being bedridden from the perspective of nursing is totally different. This study reveals phases of development and a range of factors influencing the problem of becoming bedridden. Many of these factors arise from the person and his/her interactional behaviour in the

Impact of production systems on swine confinement buildings bioaerosols.

Science.gov (United States)

Létourneau, Valérie; Nehmé, Benjamin; Mériaux, Anne; Massé, Daniel; Duchaine, Caroline

2010-02-01

Hog production has been substantially intensified in Eastern Canada. Hogs are now fattened in swine confinement buildings with controlled ventilation systems and high animal densities. Newly designed buildings are equipped with conventional manure handling and management systems, shallow or deep litter systems, or source separation systems to manage the large volumes of waste. However, the impacts of those alternative production systems on bioaerosol concentrations within the barns have never been evaluated. Bioaerosols were characterized in 18 modern swine confinement buildings, and the differences in bioaerosol composition in the three different production systems were evaluated. Total dust, endotoxins, culturable actinomycetes, fungi, and bacteria were collected with various apparatuses. The total DNA of the air samples was extracted, and quantitative polymerase chain reaction (PCR) was used to assess the total number of bacterial genomes, as a total (culturable and nonculturable) bacterial assessment. The measured total dust and endotoxin concentrations were not statistically different in the three studied production systems. In buildings with sawdust beds, actinomycetes and molds were found in higher concentrations than in the conventional barns. Aspergillus, Cladosporium, Penicillium, and Scopulariopsis species were identified in all the studied swine confinement buildings. A. flavus, A. terreus, and A. versicolor were abundantly present in the facilities with sawdust beds. Thermotolerant A. fumigatus and Mucor were usually found in all the buildings. The culturable bacteria concentrations were higher in the barns with litters than in the conventional buildings, while real-time PCR revealed nonstatistically different concentrations of total bacteria in all the studied swine confinement buildings. In terms of workers' respiratory health, barns equipped with a solid/liquid separation system may offer better air quality than conventional buildings or barns with

Electrostatically confined quantum rings in bilayer graphene.

Science.gov (United States)

Zarenia, M; Pereira, J M; Peeters, F M; Farias, G A

2009-12-01

We propose a new system where electron and hole states are electrostatically confined into a quantum ring in bilayer graphene. These structures can be created by tuning the gap of the graphene bilayer using nanostructured gates or by position-dependent doping. The energy levels have a magnetic field (B(0)) dependence that is strikingly distinct from that of usual semiconductor quantum rings. In particular, the eigenvalues are not invariant under a B(0) --> -B(0) transformation and, for a fixed total angular momentum index m, their field dependence is not parabolic, but displays two minima separated by a saddle point. The spectra also display several anticrossings, which arise due to the overlap of gate-confined and magnetically confined states.

Progress in toroidal confinement and fusion research

International Nuclear Information System (INIS)

Furth, H.P.

1987-10-01

During the past 30 years, the characteristic T/sub i/n tau/sub E/-value of toroidal-confinement experiments has advanced by more than seven orders of magnitude. Part of this advance has been due to an increase of gross machine parameters. Most of this advance has been due to an increase of gross machine parameters. Most of the advance is associated with improvements in the ''quality of plasma confinement.'' The combined evidence of spherator and tokamak research clarifies the role of magnetic-field geometry in determining confinement and points to the importance of shielding out plasma edge effects. A true physical understanding of anomalous transport remains to be achieved. 39 refs., 11 figs., 1 tab

Theory of plasma confinement in non-axisymmetric magnetic fields.

Science.gov (United States)

Helander, Per

2014-08-01

The theory of plasma confinement by non-axisymmetric magnetic fields is reviewed. Such fields are used to confine fusion plasmas in stellarators, where in contrast to tokamaks and reversed-field pinches the magnetic field generally does not possess any continuous symmetry. The discussion is focussed on magnetohydrodynamic equilibrium conditions, collisionless particle orbits, and the kinetic theory of equilbrium and transport. Each of these topics is fundamentally affected by the absence of symmetry in the magnetic field: the field lines need not trace out nested flux surfaces, the particle orbits may not be confined, and the cross-field transport can be very large. Nevertheless, by tailoring the magnetic field appropriately, well-behaved equilibria with good confinement can be constructed, potentially offering an attractive route to magnetic fusion. In this article, the mathematical apparatus to describe stellarator plasmas is developed from first principles and basic elements underlying confinement optimization are introduced.

Plasma transport simulation modelling for helical confinement systems

International Nuclear Information System (INIS)

Yamazaki, K.; Amano, T.

1992-01-01

New empirical and theoretical transport models for helical confinement systems are developed on the basis of the neoclassical transport theory, including the effect of the radial electric field and of multi-helicity magnetic components as well as the drift wave turbulence transport for electrostatic and electromagnetic modes or the anomalous semi-empirical transport. These electron thermal diffusivities are compared with experimental data from the Compact Helical System which indicate that the central transport coefficient of a plasma with electron cyclotron heating agrees with neoclassical axisymmetric value and the transport outside the half-radius is anomalous. On the other hand, the transport of plasmas with neutral beam injection heating is anomalous in the whole plasma region. This anomaly is not explained by the electrostatic drift wave turbulence models in these discharges with flat density profiles. For a detailed prediction of the plasma parameters in the Large Helical Device (LHD), 3-D equilibrium/1-D transport simulations including empirical or drift wave turbulence models are performed which suggest that the global confinement time of the LHD is determined mainly by the electron anomalous transport in the plasma edge region rather than by the helical ripple transport in the core region. Even if the ripple loss can be eliminated, the increase in global confinement is 10%. However, the rise in the central ion temperature is more than 20%. If the anomalous loss can be reduced to half of the value used in the present scaling, as is the case in the H-mode of tokamak discharges, the neoclassical ripple loss through the ion channel becomes important even in the plasma core. The 5% radial inward shift of the plasma column with respect to the major radius improves the plasma confinement and increases the fusion product by more than 50% by reducing the neoclassical asymmetric ion transport loss and increasing the plasma radius (10%). (author). 32 refs, 7 figs

Effect of laser peening with glycerol as plasma confinement layer

Science.gov (United States)

Tsuyama, Miho; Ehara, Naoya; Yamashita, Kazuma; Heya, Manabu; Nakano, Hitoshi

2018-03-01

The effects of controlling the plasma confinement layer on laser peening were investigated by measuring the hardness and residual stress of laser-peened stainless steels. The plasma confinement layer contributes to increasing the pressure of shock waves by suppressing the expansion of the laser-produced plasma. Most previous studies on laser peening have employed water as the plasma confinement layer. In this study, a glycerol solution is used in the context of a large acoustic impedance. It is found that this glycerol solution is superior to water in its ability to confine plasma and that suitable conditions exist for the glycerol solution to act as a plasma confinement layer to achieve efficient laser peening.

Deuteron-NMR investigation on the dynamics of supercooled, confined water

Energy Technology Data Exchange (ETDEWEB)

Sattig, Matthias; Vogel, Michael [TU Darmstadt, Institut fuer Festkoerperphysik (Germany)

2013-07-01

The dynamical behaviour of water in the regime of the supercooled liquid is a topic of large interest. In particular, the existence of a fragile-to-strong transition (FST) at T=225K related to the transition between two distinct phases of liquid water is controversially discussed. Due to crystallization the temperature range proposed for the FST is hardly accessible in bulk water. Therefore, we confine heavy water to narrow pores in the mesoporous silicate MCM-41. This suppresses the freezing of a substantial fraction of water, enabling direct investigation of the interesting temperatures. Deuteron-NMR methods are utilised to determine the rotational correlation times τ of water on time scales from ns up to s. The spin-lattice-relaxation time T{sub 1} exhibits a typical minimum at about T = 230 K. Above this minimum the correlation times follow a Vogel-Fulcher-Tammann law. Below the minimum, two relaxation processes could be observed. The low-temperature processes show a different temperature dependence, where the curves τ(T) of all processes intersect at about T = 230 K. A comparison with literature data from neutron scattering and dielectric spectroscopy gives rise to the idea that the observed crossover is due to this intersection of processes rather than to a FST. To test this idea studies on water confined to MCM-41 with different pore sizes and fillings are in progress.

Decreased re-conviction rates of DUI offenders with intensive supervision and home confinement.

Science.gov (United States)

Barta, William D; Fisher, Virginia; Hynes, Patrick

2017-11-01

In some jurisdictions, persons who are convicted of driving under the influence of alcohol (DUI) are allowed to serve some portion of their prison sentence under home confinement as part of Intensive Supervision Programs (ISPs) which include pre-release psycho-education and close post-release supervision. Test the hypothesis that persons convicted of DUI offenses who have spent some portion of their sentence under home confinement, as compared to a historical comparison group, will exhibit a relatively low re-conviction rate. Using administrative data for 1,410 repeat DUI offenders (302 members of the historical comparison group, 948 ISP members, and 160 persons who appear in both groups at different points in time), with a follow-up period of up to 3 years and 10 months, a marginal Cox model was employed to compare conviction rates of persons who experienced intensive supervision and home confinement with historical comparison group members. Persons with ISP + home confinement experience a re-conviction rate that is less than half that observed in the comparison group. Age, ethnicity (white vs. non-white), and gender are also significant predictors of re-conviction. Home confinement, in conjunction with psycho-education and other program elements, is one means of reducing the costs of incarceration. The results of this study suggest that, in addition to cost savings, states may realize a public safety benefit in the form of a reduction in DUI offense rates.

Overview of Milestone E activities, greater confinement than shallow land burial

International Nuclear Information System (INIS)

Mezga, L.J.

1981-01-01

In summary, the objective of Milestone E is to provide the technology and documentation needed to open a site providing greater confinement than shallow land burial. To that end, ORNL has prepared a technical position paper defining greater confinement disposal, options for achieving it, and the need for this disposal technology. In order to meet the objective of the milestones, the LLWMP evaluated the full range of options to shallow land burial and decided to focus on a combination of greater depth solidification containment and engineered barriers. The program identified a series of research needs and then focused program efforts on resolving those needs. These tasks are proceeding on schedule at this time but budget reductions may have an impact on our ability to maintain the schedule

High-field penning-malmberg trap: confinement properties and use in positron accumulation

Energy Technology Data Exchange (ETDEWEB)

Hartley, J.H.

1997-09-01

This dissertation reports on the development of the 60 kG cryogenic positron trap at Lawrence Livermore National Laboratory, and compares the trap`s confinement properties with other nonneutral plasma devices. The device is designed for the accumulation of up to 2{times}10{sup 9} positrons from a linear-accelerator source. This positron plasma could then be used in Bhabha scattering experiments. Initial efforts at time-of-flight accumulation of positrons from the accelerator show rapid ({approximately}100 ms) deconfinement, inconsistent with the long electron lifetimes. Several possible deconfinement mechanisms have been explored, including annihilation on residual gas, injection heating, rf noise from the accelerator, magnet field curvature, and stray fields. Detailed studies of electron confinement demonstrate that the empirical scaling law used to design the trap cannot be extrapolated into the parameter regime of this device. Several possible methods for overcoming these limitations are presented.

Particle-confinement criteria for axisymmetric field-reversed magnetic configurations

International Nuclear Information System (INIS)

Hsiao, M.Y.; Miley, G.H.

1984-01-01

Based on two constants of motion, H and Psub(theta), where H is the total energy of a particle and Psub(theta) is its canonical angular momentum, particle confinement criteria are derived which impose constraints on H and Psub(theta). With no electric field at the ends of field-reversed magnetic configurations, confinement criteria for closed-field and absolute confinements are obtained explicitly, including both lower and upper bounds of Psub(theta)/q, where q is the charge of the species considered, for a class of Hill's vortex field-reversed magnetic configurations. The commonly used criterion for the Hamiltonian, H 0 Psub(theta), where ω 0 is identical to qB 0 /mc, is deduced from a more general form as a special case. In this special case, it is found necessary to impose a new criterion, -B 0 R 2 sub(w)/2c 0 is the vacuum field, which reduces the confinement region in (H,Psub(theta)) space. With the presence of electric fields at the ends of field-reversed magnetic configurations, confinement criteria are obtained for two interesting cases. In addition to lower and upper bounds of H, both lower and upper bounds of Psub(theta)/q are found. For axially confined particles, the lower bound of Psub(theta)/q reduces the confinement region in (H,Psub(theta)) space and represents a new criterion. These results can be applied to calculations for field-reversed mirrors and field-reversed theta pinches. (author)

Quantum-confined nanowires as vehicles for enhanced electrical transport

International Nuclear Information System (INIS)

Mohammad, S Noor

2012-01-01

Electrical transport in semiconductor nanowires taking quantum confinement and dielectric confinement into account has been studied. A distinctly new route has been employed for the study. The fundamental science underlying the model is based on a relationship between the quantum confinement and the structural disorder of the nanowire surface. The role of surface energy and thermodynamic imbalance in nanowire structural disorder has been described. A model for the diameter dependence of energy bandgap of nanowires has been developed. Ionized impurity scattering, dislocation scattering and acoustic phonon scattering have been taken into account to study carrier mobility. A series of calculations on silicon nanowires show that carrier mobility in nanowires can be greatly enhanced by quantum confinement and dielectric confinement. The electron mobility can, for example, be a factor of 2–10 higher at room temperature than the mobility in a free-standing silicon nanowire. The calculated results agree well with almost all experimental and theoretical results available in the literature. They successfully explain experimental observations not understood before. The model is general and applicable to nanowires from all possible semiconductors. It is perhaps the first physical model highlighting the impact of both quantum confinement and dielectric confinement on carrier transport. It underscores the basic causes of thin, lowly doped nanowires in the temperature range 200 K ≤ T ≤ 500 K yielding very high carrier mobility. It suggests that the scattering by dislocations (stacking faults) can be very detrimental for carrier mobility. (paper)

Fusion radioactivity confinement and application to postulated ITER accidents

International Nuclear Information System (INIS)

Piet, S.J.; Brereton, S.J.

1991-01-01

An assessment of the ITER radioactivity confinement shows reduction of potential accidental releases to the environment by two orders of magnitude. Important credits are the 1% volume/day confinement leakage rate, radioactivity decay for short-lived isotopes, resumption of detritiation/negative pressure within seven days of the accident, and wind meander during the slow confinement leakage. Achieving this two order of magnitude credit in practice requires appropriate design details, especially the leakage rate and detritiation/negative pressure equipment, and research to validate some key assumptions. The confinement maximizes dependence on passive safety features, thereby working toward using fusion's potential safety advantages. The confinement includes several confinement zones with varying human access allowances. Some confinement areas are normally isolated from the environment, the closed ventilation zone. Some areas have an inert cover gas to inhibit combustion. If future assessments of accidental overpressure show the need, we propose a filter/vent system. This report documents our work for the ITER Conceptual Design Activity (CDA). The report is consistent with the final CDA design reports and descriptions, except that our analysis includes a filter/vent. For gaseous or vapor tritium and for most activated aerosols, the reference release fraction is about 2%. For short-lived tungsten-rhenium aerosols, the reference release fraction is somewhat lower, as low as 0.5% for some accident scenarios. Even without resumption of detritiation/decontamination or negative pressure within seven days of the accident, the release fraction for stays below 4%

Inertial electrostatic confinement (IEC) fusion fundamentals and applications

CERN Document Server

Miley, George H

2014-01-01

This book provides readers with an introductory understanding of Inertial Electrostatic Confinement (IEC), a type of fusion meant to retain plasma using an electrostatic field. IEC provides a unique approach for plasma confinement, as it offers a number of spin-off applications, such as a small neutron source for Neutron Activity Analysis (NAA), that all work towards creating fusion power. The IEC has been identified in recent times as an ideal fusion power unit because of its ability to burn aneutronic fuels like p-B11 as a result of its non-Maxwellian plasma dominated by beam-like ions. This type of fusion also takes place in a simple mechanical structure small in size, which also contributes to its viability as a source of power. This book posits that the ability to study the physics of IEC in very small volume plasmas makes it possible to rapidly investigate a design to create a power-producing device on a much larger scale. Along with this hypothesis the book also includes a conceptual experiment propose...

Electrostatic-Dipole (ED) Fusion Confinement Studies

Science.gov (United States)

Miley, George H.; Shrestha, Prajakti J.; Yang, Yang; Thomas, Robert

2004-11-01

The Electrostatic-Dipole (ED) concept significantly differs from a "pure" dipole confinement device [1] in that the charged particles are preferentially confined to the high-pressure region interior of the dipole coil by the assistance of a surrounding spherical electrostatic grid. In present ED experiments, a current carrying coil is embedded inside the grid of an IEC such as to produce a magnetic dipole field. Charged particles are injected axisymmetrically from an ion gun (or duo-plasmatron) into the center of the ED confinement grid/dipole ring where they oscillate along the magnetic field lines and pass the peak field region at the center of the dipole region. As particles begin accelerating away from the center region towards the outer electrostatic grid region, they encounter a strong electrostatic potential (order of 10's of kilovolts) retarding force. The particles then decelerate, reverse direction and re-enter the dipole field region where again magnetic confinement dominates. This process continues, emulating a complex harmonic oscillator motion. The resulting pressure profile averaged over the field curvature offers good plasma stability in the ED configuration. The basic concept and results from preliminary experiments will be described. [1] M.E. Mauel, et al. "Dipole Equilibrium and Stability," 18th IAEA Conference of Plasma Phys. and Control. Nuclear Fusion, Varenna, Italy 2000, IAEA-F1-CN-70/TH

Interacting supernovae from photoionization-confined shells around red supergiant stars

Science.gov (United States)

Mackey, Jonathan; Mohamed, Shazrene; Gvaramadze, Vasilii V.; Kotak, Rubina; Langer, Norbert; Meyer, Dominique M.-A.; Moriya, Takashi J.; Neilson, Hilding R.

2014-08-01

Betelgeuse, a nearby red supergiant, is a fast-moving star with a powerful stellar wind that drives a bow shock into its surroundings. This picture has been challenged by the discovery of a dense and almost static shell that is three times closer to the star than the bow shock and has been decelerated by some external force. The two physically distinct structures cannot both be formed by the hydrodynamic interaction of the wind with the interstellar medium. Here we report that a model in which Betelgeuse's wind is photoionized by radiation from external sources can explain the static shell without requiring a new understanding of the bow shock. Pressure from the photoionized wind generates a standing shock in the neutral part of the wind and forms an almost static, photoionization-confined shell. Other red supergiants should have much more massive shells than Betelgeuse, because the photoionization-confined shell traps up to 35 per cent of all mass lost during the red supergiant phase, confining this gas close to the star until it explodes. After the supernova explosion, massive shells dramatically affect the supernova light curve, providing a natural explanation for the many supernovae that have signatures of circumstellar interaction.

Experimental Study of Damage Evolution in Circular Stirrup-Confined Concrete.

Science.gov (United States)

Li, Zuohua; Peng, Zhihan; Teng, Jun; Wang, Ying

2016-04-08

This paper presents an experimental study on circular stirrup-confined concrete specimens under uniaxial and monotonic load. The effects of stirrup volume ratio, stirrup yield strength and concrete strength on damage evolution of stirrup-confined concrete were investigated. The experimental results showed that the strength and ductility of concrete are improved by appropriate arrangement of the stirrup confinement. Firstly, the concrete damage evolution can be relatively restrained with the increase of the stirrup volume ratio. Secondly, higher stirrup yield strength usually causes larger confining pressures and slower concrete damage evolution. In contrast, higher concrete strength leads to higher brittleness, which accelerates the concrete damage evolution. A plastic strain expression is obtained through curve fitting, and a damage evolution equation for circular stirrup-confined concrete is proposed by introducing a confinement factor ( C ) based on the experimental data. The comparison results demonstrate that the proposed damage evolution model can accurately describe the experimental results.

Experimental Study of Damage Evolution in Circular Stirrup-Confined Concrete

Science.gov (United States)

Li, Zuohua; Peng, Zhihan; Teng, Jun; Wang, Ying

2016-01-01

This paper presents an experimental study on circular stirrup-confined concrete specimens under uniaxial and monotonic load. The effects of stirrup volume ratio, stirrup yield strength and concrete strength on damage evolution of stirrup-confined concrete were investigated. The experimental results showed that the strength and ductility of concrete are improved by appropriate arrangement of the stirrup confinement. Firstly, the concrete damage evolution can be relatively restrained with the increase of the stirrup volume ratio. Secondly, higher stirrup yield strength usually causes larger confining pressures and slower concrete damage evolution. In contrast, higher concrete strength leads to higher brittleness, which accelerates the concrete damage evolution. A plastic strain expression is obtained through curve fitting, and a damage evolution equation for circular stirrup-confined concrete is proposed by introducing a confinement factor (C) based on the experimental data. The comparison results demonstrate that the proposed damage evolution model can accurately describe the experimental results. PMID:28773402

The destructive interference phenomenon as a reason for the confinement in QEDsub(1+1)

International Nuclear Information System (INIS)

Ilieva, N.P.; Pervushina, V.N.

1986-01-01

Two-dimensional massless QED is considered in terms of gauge-invariant dynamical variables. By an example of the fermion Green function it is shown that the linearly risng potential allows the existence of excitations with quark quantum numbers in the spectrum of the model (so the validity of Wilson criterion does not lead automaticaly to the confinement). The topological generation of the physical-field phase in a finite-volume space-time is considered. The destructive interference of the phase factors is pointed out as a possible reason for the confinement

Issues in tokamak/stellarator transport and confinement enhancement mechanisms

International Nuclear Information System (INIS)

Perkins, F.W.

1990-08-01

At present, the mechanism for anomalous energy transport in low-β toroidal plasmas -- tokamaks and stellarators -- remains unclear, although transport by turbulent E x B velocities associated with nonlinear, fine-scale microinstabilities is a leading candidate. This article discusses basic theoretical concepts of various transport and confinement enhancement mechanisms as well as experimental ramifications which would enable one to distinguish among them and hence identify a dominant transport mechanism. While many of the predictions of fine-scale turbulence are born out by experiment, notable contradictions exist. Projections of ignition margin rest both on the scaling properties of the confinement mechanism and on the criteria for entering enhanced confinement regimes. At present, the greatest uncertainties lie with the basis for scaling confinement enhancement criteria. A series of questions, to be answered by new experimental/theoretical work, is posed to resolve these outstanding contradictions (or refute the fine-scale turbulence model) and to establish confinement enhancement criteria. 73 refs., 4 figs., 5 tabs

Large Eddy Simulation of the spray formation in confinements

International Nuclear Information System (INIS)

Lampa, A.; Fritsching, U.

2013-01-01

Highlights: • Process stability of confined spray processes is affected by the geometric design of the spray confinement. • LES simulations of confined spray flow have been performed successfully. • Clustering processes of droplets is predicted in simulations and validated with experiments. • Criteria for specific coherent gas flow patterns and droplet clustering behaviour are found. -- Abstract: The particle and powder properties produced within spray drying processes are influenced by various unsteady transport phenomena in the dispersed multiphase spray flow in a confined spray chamber. In this context differently scaled spray structures in a confined spray environment have been analyzed in experiments and numerical simulations. The experimental investigations have been carried out with Particle-Image-Velocimetry to determine the velocity of the gas and the discrete phase. Large-Eddy-Simulations have been set up to predict the transient behaviour of the spray process and have given more insight into the sensitivity of the spray flow structures in dependency from the spray chamber design

Some aspects of geometrical confinement

Energy Technology Data Exchange (ETDEWEB)

Novello, M.; De Lorenci, V.A. [Centro Brasileiro de Pesquisas Fisicas (CBPF), Rio de Janeiro, RJ (Brazil); Elbaz, E. [Lyon-1 Univ., 69 - Villeurbanne (France)

1998-04-01

In this paper we present a toy model for the dynamics of a gauge field theory in such way that spin-one particles can be confined in a compact domain. We show that the property of confinement can be associated to the formation of a null surface identified to a horizon. This is due to the presence of an effective geometry generated by the self-interaction of the gauge field that guides the wave propagation of the field. This phenomenon has a striking analogy to the gravitational black hole in Einstein general theory of relativity, separating two domains of spacetime that can be trespassed only into one direction. (author) 4 refs.

Effects of confinement in meso-porous silica and carbon nano-structures; Etude des effets de confinement dans la silice mesoporeuse et dans certaines nanostructures carbonees

Energy Technology Data Exchange (ETDEWEB)

Leon, V

2006-07-15

Physico-chemical properties of materials can be strongly modified by confinement because of the quantum effects that appear at such small length scales and also because of the effects of the confinement itself. The aim of this thesis is to show that both the nature of the confining material and the size of the pores and cavities have a strong impact on the confined material. We first show the effect of the pore size of the host meso-porous silica on the temperature of the solid-solid phase transition of silver selenide, a semiconducting material with enhanced magnetoresistive properties under non-stoichiometric conditions. Narrowing the pores from 20 nm to 2 nm raises the phase transition temperature from 139 C to 146 C. This result can be explained by considering the interaction between the confining and confined materials as a driving force. The effects of confinement are also studied in the case of hydrogen and deuterium inside cavities of organized carbon nano-structures. The effects that appear in the adsorption/desorption cycles are much stronger with carbon nano-horns as the host material than with C60 pea-pods and single-walled carbon nano-tubes. (author)

Effect of surface hydrophobicity on the dynamics of water at the nanoscale confinement: A molecular dynamics simulation study

International Nuclear Information System (INIS)

Choudhury, Niharendu

2013-01-01

Highlights: • We present atomistic MD simulation of water confined between two paraffin-like plates. • Effect of plate hydrophobicity on the confined water dynamics is investigated. • Diffusivity of confined water is calculated from mean squared displacements. • Rotational dynamics of the confined water has bimodal nature of relaxation. • Monotonic dependence of translational and rotational dynamics on hydrophobicity. - Abstract: We present detailed molecular dynamics simulations of water in and around a pair of plates immersed in water to investigate the effect of degree of hydrophobicity or hydrophilicity of the plates on dynamics of water confined between the two plates. The nature of the plate has been tuned from hydrophobic to hydrophilic and vice versa by varying plate-water dispersion interaction. Analyses of the translational dynamics as performed by calculating mean squared displacements of the confined water reveal a monotonically decreasing trend of the diffusivity with increasing hydrophilicity of the plates. Orientational dynamics of the confined water also follows the same monotonic trend. Although orientational time constant almost does not change with the increase of plate-water dispersion interaction in the hydrophobic regime corresponding to the smaller plate-water attraction, it changes considerably in the hydrophilic regime corresponding to larger plate-water dispersion interactions

Quark confinement potential and color Van der Waals force

International Nuclear Information System (INIS)

Zheng Yuming; Hua Daping; Liu Zuhua

1985-01-01

The color-analog Van der Waals force between two hadrons is studied by use of the coupling channel resonating group method in the framework of the Gaussian-type quark confinement potential. The problem of the boundary values for the two channel coupling differential equations is changed to the problem of the initial values. The equations are solved numerically by use of the Gear mehtod. The calculated results show that there is no color Van der Waals force between hadrons in the confinement potential model. This indicates that the confinement potential model not only can describe the internal structure of hadrons but also can be used to calculate the hadron-hadron interactions if the quark confinement potential is chosen properly

Influence of error fields on the plasma confining field and the plasma confinement in tokamak

International Nuclear Information System (INIS)

Matsuda, Shinzaburo

1977-05-01

Influence of error fields on the plasma confining field and the plasma confinement is treated in the standpoint of design. In the initial breakdown phase before formation of the closed magnetic surfaces, the vertical field properly applied is the most important. Once the magnetic surfaces are formed, the non-axisymmetric error field is important. Effect of the shell gap associated with iron core and with pulsed vertical coils is thus studied. The formation of magnetic islands due to the external non-axisymmetric error field is studied with a simple model. A method of suppressing the islands by choosing the minor periodicity is proposed. (auth.)

Confinement and Tritium Stripping Systems for APT Tritium Processing

Energy Technology Data Exchange (ETDEWEB)

Hsu, R.H. [Westinghouse Savannah River Company, AIKEN, SC (United States); Heung, L.K.

1997-10-20

This report identifies functions and requirements for the tritium process confinement and clean-up system (PCCS) and provides supporting technical information for the selection and design of tritium confinement, clean-up (stripping) and recovery technologies for new tritium processing facilities in the Accelerator for the Production of Tritium (APT). The results of a survey of tritium confinement and clean-up systems for large-scale tritium handling facilities and recommendations for the APT are also presented.

Confinement and Tritium Stripping Systems for APT Tritium Processing

International Nuclear Information System (INIS)

Hsu, R.H.; Heung, L.K.

1997-01-01

This report identifies functions and requirements for the tritium process confinement and clean-up system (PCCS) and provides supporting technical information for the selection and design of tritium confinement, clean-up (stripping) and recovery technologies for new tritium processing facilities in the Accelerator for the Production of Tritium (APT). The results of a survey of tritium confinement and clean-up systems for large-scale tritium handling facilities and recommendations for the APT are also presented

Mesoscale simulations of confined Nafion thin films

Science.gov (United States)

Vanya, P.; Sharman, J.; Elliott, J. A.

2017-12-01

The morphology and transport properties of thin films of the ionomer Nafion, with thicknesses on the order of the bulk cluster size, have been investigated as a model system to explain the anomalous behaviour of catalyst/electrode-polymer interfaces in membrane electrode assemblies. We have employed dissipative particle dynamics (DPD) to investigate the interaction of water and fluorocarbon chains, with carbon and quartz as confining materials, for a wide range of operational water contents and film thicknesses. We found confinement-induced clustering of water perpendicular to the thin film. Hydrophobic carbon forms a water depletion zone near the film interface, whereas hydrophilic quartz results in a zone with excess water. There are, on average, oscillating water-rich and fluorocarbon-rich regions, in agreement with experimental results from neutron reflectometry. Water diffusivity shows increasing directional anisotropy of up to 30% with decreasing film thickness, depending on the hydrophilicity of the confining material. A percolation analysis revealed significant differences in water clustering and connectivity with the confining material. These findings indicate the fundamentally different nature of ionomer thin films, compared to membranes, and suggest explanations for increased ionic resistances observed in the catalyst layer.

Effect of ELMs on rotation and momentum confinement in H-mode discharges in JET

DEFF Research Database (Denmark)

Versloot, T.W.; de Vries, P.C.; Giroud, C.

2010-01-01

. An increase in profile peaking of ion temperature and angular frequency is observed. At the same time the plasma confinement is reduced while the ratio of confinement times (Rτ = τE/τ) increases noticeably with ELM frequency. This change could be explained by the relatively larger ELM induced losses......The loss of plasma toroidal angular momentum and thermal energy by edge localized modes (ELMs) has been studied in JET. The analysis shows a consistently larger drop in momentum in comparison with the energy loss associated with the ELMs. This difference originates from the large reduction...... in angular frequency at the plasma edge, observed to penetrate into the plasma up to r/a ~ 0.65 during large type-I ELMs. As a result, the time averaged angular frequency is lowered near the top of the pedestal with increasing ELM frequency, resulting in a significant drop in thermal Mach number at the edge...

NRMC - A GPU code for N-Reverse Monte Carlo modeling of fluids in confined media

Science.gov (United States)

Sánchez-Gil, Vicente; Noya, Eva G.; Lomba, Enrique

2017-08-01

NRMC is a parallel code for performing N-Reverse Monte Carlo modeling of fluids in confined media [V. Sánchez-Gil, E.G. Noya, E. Lomba, J. Chem. Phys. 140 (2014) 024504]. This method is an extension of the usual Reverse Monte Carlo method to obtain structural models of confined fluids compatible with experimental diffraction patterns, specifically designed to overcome the problem of slow diffusion that can appear under conditions of tight confinement. Most of the computational time in N-Reverse Monte Carlo modeling is spent in the evaluation of the structure factor for each trial configuration, a calculation that can be easily parallelized. Implementation of the structure factor evaluation in NVIDIA® CUDA so that the code can be run on GPUs leads to a speed up of up to two orders of magnitude.

Procedure for the reversible confinement of gases or vapours in a natural or synthetic zeolite

International Nuclear Information System (INIS)

1980-01-01

The zeolite is treated with silane at a temperature of 100-140 0 C to silanise it in the H-form. This narrows the pores in the zeolite and the grains bind together creating cavities. The silanised zeolite and the material to be confined are brought into contact at high pressure, for example at an excess pressure of 0.5 atm. Contact is continued until the required quantity of gas or vapour has been adsorbed by the zeolite. Under the same high pressure water is added to the system which causes further narrowing of the pores. Preferably the process of silanising and treating with water is then repeated one or more times to close the pores and ensure confinement. The process is reversed by heating the product above 300 0 C. The bonds formed by silanising are then broken and the confined material is liberated. This process has applications in the confinement of valuable gases such as enriched isotopes, and of dangerous gases such as radioactive waste gases. (Th.W.P.)

Morphology and composition of pyrotechnic residues formed at different levels of confinement.

Science.gov (United States)

Vermeij, Erwin; Duvalois, Willem; Webb, Rutger; Koeberg, Mattijs

2009-04-15

Post explosion residues (PER) are residues from pyrotechnic compositions or explosives that are generated during an explosion. In the recent past SEM/EDX was used several times to analyze PER from pyrotechnic compositions. The results from these studies suggest that there might be a difference in morphology and composition of pyrotechnic residues formed at different levels of confinement. Also because of general thermodynamic principles it is believed that at higher levels of confinement the final pressure and temperature during the explosion is probably (but not necessarily) higher, eventually resulting in smaller and more spherical particles and a more homogeneous elemental composition. If there is a relation between morphology and composition of pyrotechnic residues and the level of confinement at which these are formed, it would be possible to draw conclusions about the conditions at which pyrotechnic residues were formed and the kind and construction of the device used. This may aid forensic scientists not only in the determination of the original explosive composition, but also of the explosive device. To perform controlled experiments with pyrotechnic charges at, at least, two pre-set levels of confinement a test vessel was built by TNO Defence, Security and Safety. For this study, three different flash powder compositions and black powder were selected. The generated residues were sampled on collecting plates and Nucleopore filters connected to a pump system in the immediate vicinity of the venting area for further analyses by SEM/EDX and XRD. From the results it follows that in the pressure range studied, the level of confinement seems to have a minor effect on the features of the generated residue particles. Because passive sampling by means of collector plates seemed doubtful and because the number of experiments had to be limited it is impossible to draw definitive conclusions. In addition to the level of confinement several other variables may affect

Transition to the improved confinement mode in torsatron U-3M in range of rare collision frequencies

International Nuclear Information System (INIS)

Pashnev, V.K.; Sorokovov, E.L.; Berezhnyj, V.L. and others

2010-01-01

Transition to the mode of improved plasma confinement in U-3M facility earlier was discussed in works [1-3]. In these studies discussed the various processes in the confinement volume and in the peripheral plasma that accompany the transition process. Study of plasma confinement and process of transition into the mode of improved confinement just at rare collisions between plasma particles is very important because future fusion reactor based on a toroidal magnetic trap will operate under plasma parameters with rare collision frequencies ('banana' mode). The peculiarity of experiments on torsatron U-3M is that they are conducted at small density n-bar e ≤ 2 lover case x 10 12 cm -3 and, thereby, the frequency of collisions in the confinement area is in the 'banana' mode [4]. And herewith, time of collisions is essentially smaller (up to several orders for electrons and up to the order for ions) than the lifetime of plasma particles. It ensures maxwellization of distribution function and possibility to compare the obtained results with data from other experiments. The objective of this work is to study the main regularity of transition into the mode of improved confinement. Also it is interesting to compare the results with data from other facilities.

Spindles and active vortices in a model of confined filament-motor mixtures.

Science.gov (United States)

Head, David A; Briels, Wj; Gompper, Gerhard

2011-11-16

Robust self-organization of subcellular structures is a key principle governing the dynamics and evolution of cellular life. In fission yeast cells undergoing division, the mitotic spindle spontaneously emerges from the interaction of microtubules, motor proteins and the confining cell walls, and asters and vortices have been observed to self-assemble in quasi-two dimensional microtubule-kinesin assays. There is no clear microscopic picture of the role of the active motors driving this pattern formation, and the relevance of continuum modeling to filament-scale structures remains uncertain. Here we present results of numerical simulations of a discrete filament-motor protein model confined to a pressurised cylindrical box. Stable spindles, nematic configurations, asters and high-density semi-asters spontaneously emerge, the latter pair having also been observed in cytosol confined within emulsion droplets. State diagrams are presented delineating each stationary state as the pressure, motor speed and motor density are varied. We further highlight a parameter regime where vortices form exhibiting collective rotation of all filaments, but have a finite life-time before contracting to a semi-aster. Quantifying the distribution of life-times suggests this contraction is a Poisson process. Equivalent systems with fixed volume exhibit persistent vortices with stochastic switching in the direction of rotation, with switching times obeying similar statistics to contraction times in pressurised systems. Furthermore, we show that increasing the detachment rate of motors from filament plus-ends can both destroy vortices and turn some asters into vortices. We have shown that discrete filament-motor protein models provide new insights into the stationary and dynamical behavior of active gels and subcellular structures, because many phenomena occur on the length-scale of single filaments. Based on our findings, we argue the need for a deeper understanding of the microscopic

Confinement of hydrogen at high pressure in carbon nanotubes

Science.gov (United States)

Lassila, David H [Aptos, CA; Bonner, Brian P [Livermore, CA

2011-12-13

A high pressure hydrogen confinement apparatus according to one embodiment includes carbon nanotubes capped at one or both ends thereof with a hydrogen-permeable membrane to enable the high pressure confinement of hydrogen and release of the hydrogen therethrough. A hydrogen confinement apparatus according to another embodiment includes an array of multi-walled carbon nanotubes each having first and second ends, the second ends being capped with palladium (Pd) to enable the high pressure confinement of hydrogen and release of the hydrogen therethrough as a function of palladium temperature, wherein the array of carbon nanotubes is capable of storing hydrogen gas at a pressure of at least 1 GPa for greater than 24 hours. Additional apparatuses and methods are also presented.

Confined-but-Connected Quantum Solids via Controlled Ligand Displacement

KAUST Repository

Baumgardner, William J.

2013-07-10

Confined-but-connected quantum dot solids (QDS) combine the advantages of tunable, quantum-confined energy levels with efficient charge transport through enhanced electronic interdot coupling. We report the fabrication of QDS by treating self-assembled films of colloidal PbSe quantum dots with polar nonsolvents. Treatment with dimethylformamide balances the rates of self-assembly and ligand displacement to yield confined-but-connected QDS structures with cubic ordering and quasi-epitaxial interdot connections through facets of neighboring dots. The QDS structure was analyzed by a combination of transmission electron microscopy and wide-angle and small-angle X-ray scattering. Excitonic absorption signatures in optical spectroscopy confirm that quantum confinement is preserved. Transport measurements show significantly enhanced conductivity in treated films. © 2013 American Chemical Society.

Static and Dynamic Properties of DNA Confined in Nanochannels

Science.gov (United States)

Gupta, Damini

Next-generation sequencing (NGS) techniques have considerably reduced the cost of high-throughput DNA sequencing. However, it is challenging to detect large-scale genomic variations by NGS due to short read lengths. Genome mapping can easily detect large-scale structural variations because it operates on extremely large intact molecules of DNA with adequate resolution. One of the promising methods of genome mapping is based on confining large DNA molecules inside a nanochannel whose cross-sectional dimensions are approximately 50 nm. Even though this genome mapping technology has been commercialized, the current understanding of the polymer physics of DNA in nanochannel confinement is based on theories and lacks much needed experimental support. The results of this dissertation are aimed at providing a detailed experimental understanding of equilibrium properties of nanochannel-confined DNA molecules. The results are divided into three parts. In first part, we evaluate the role of channel shape on thermodynamic properties of channel confined DNA molecules using a combination of fluorescence microscopy and simulations. Specifically, we show that high aspect ratio of rectangular channels significantly alters the chain statistics as compared to an equivalent square channel with same cross-sectional area. In the second part, we present experimental evidence that weak excluded volume effects arise in DNA nanochannel confinement, which form the physical basis for the extended de Gennes regime. We also show how confinement spectroscopy and simulations can be combined to reduce molecular weight dispersity effects arising from shearing, photo-cleavage, and nonuniform staining of DNA. Finally, the third part of the thesis concerns the dynamic properties of nanochannel confined DNA. We directly measure the center-of-mass diffusivity of single DNA molecules in confinement and show that that it is necessary to modify the classical results of de Gennes to account for local chain

Universal evaporation dynamics of a confined sessile droplet

Science.gov (United States)

Bansal, Lalit; Hatte, Sandeep; Basu, Saptarshi; Chakraborty, Suman

2017-09-01

Droplet evaporation under confinement is ubiquitous to multitude of applications such as microfluidics, surface patterning, and ink-jet printing. However, the rich physics governing the universality in the underlying dynamics remains grossly elusive. Here, we bring out hitherto unexplored universal features of the evaporation dynamics of a sessile droplet entrapped in a 3D confined fluidic environment. We show, through extensive set of experiments and theoretical formulations, that the evaporation timescale for such a droplet can be represented by a unique function of the initial conditions. Moreover, using same theoretical considerations, we are able to trace and universally merge the volume evolution history of the droplets along with evaporation lifetimes, irrespective of the extent of confinement. We also showcase the internal flow transitions caused by spatio-temporal variation of evaporation flux due to confinement. These findings may be of profound importance in designing functionalized droplet evaporation devices for emerging engineering and biomedical applications.

Core electron-root confinement (CERC) in helical plasmas

International Nuclear Information System (INIS)

Yokoyama, M.; Ida, K.; Maassbcrg, H.

2006-10-01

The improvement of core electron heat confinement has been realized in a wide range of helical devices such as CHS, LHD, TJ-II and W7-AS. Strongly peaked electron temperature profiles and large positive radial electric field, E r , in the core region are common fractures for this improved confinement. Such observations are consistent with a transition to the electron-root' solution of the ambipolarity condition for E r in the context of the neoclassical transport, which is unique to non-axisymmetric configurations. Based on this background, this improved confinement has been collectively dubbed 'core electron-root confinement' (CERC). The electron heat diffusivity is much reduced due to the electron-root E r compared to that with E r =0 assumed, which clearly demonstrates that 1/v ripple diffusion (ν being the collision frequency) in low-collisional helical plasmas could be overcome. The magnetic configuration properties play important roles in this transition, and thresholds are found for the collisionality and electron cyclotron heating (ECH) power. (author)

Topological superconductivity, topological confinement, and the vortex quantum Hall effect

International Nuclear Information System (INIS)

Diamantini, M. Cristina; Trugenberger, Carlo A.

2011-01-01

Topological matter is characterized by the presence of a topological BF term in its long-distance effective action. Topological defects due to the compactness of the U(1) gauge fields induce quantum phase transitions between topological insulators, topological superconductors, and topological confinement. In conventional superconductivity, because of spontaneous symmetry breaking, the photon acquires a mass due to the Anderson-Higgs mechanism. In this paper we derive the corresponding effective actions for the electromagnetic field in topological superconductors and topological confinement phases. In topological superconductors magnetic flux is confined and the photon acquires a topological mass through the BF mechanism: no symmetry breaking is involved, the ground state has topological order, and the transition is induced by quantum fluctuations. In topological confinement, instead, electric charge is linearly confined and the photon becomes a massive antisymmetric tensor via the Stueckelberg mechanism. Oblique confinement phases arise when the string condensate carries both magnetic and electric flux (dyonic strings). Such phases are characterized by a vortex quantum Hall effect potentially relevant for the dissipationless transport of information stored on vortices.

L to H-mode Power Threshold and Confinement Characteristics of H-modes in KSTAR

Energy Technology Data Exchange (ETDEWEB)

Kim, H. S.; Na, Y.S., E-mail: ftwalker.hyuns@gmail.com [Seoul National University, Seoul (Korea, Republic of); Ahn, J. W. [Oak Ridge National Laboratory, Oak Ridge (United States); Jeon, Y. M.; Yoon, S. W.; Lee, K. D.; Ko, W. H.; Bae, Y. S.; Kim, W. C.; Kwak, J. G. [National Fusion Research Institute, Daejeon (Korea, Republic of)

2012-09-15

Full text: Since KSTAR has obtained the H-mode in 2010 campaign, H-mode plasmas were routinely obtained with combined heating of NBI with maximum power of 1.5 MW and ECRH with maximum power of {approx} 0.3 MW and {approx} 0.6 MW for 110 GHz and 170 GHz, respectively. The L- to H-mode power threshold and confinement properties of KSTAR H-modes are investigated in this work. Firstly, the L- to H-mode power threshold and the power loss to the seperatrix are calculated by power balance analysis for about collected 400 shots. As a result, a trend of roll-over is observed in the power threshold of KSTAR H-mode compared with the multi-machine power threshold scaling in the low density regime. Dependence of the power threshold on other parameters are also investigated such as the X-point position and shaping parameters like as triangularity and elongation. In addition, the reason of reduction of power threshold in 2011 campaign compared with that in 2010 is addressed. Secondly, the confinement enhancement factors are calculated to evaluate the performance of KSTAR H-modes. The calculated H{sub 89-p} and H{sub 98} (y, 2) represent that the confinement is enhanced in most KSTAR H-mode discharges. Interestingly, even in L-mode phases, confinement is observed to be enhanced against the multi-machine scalings. H{sub exp} factor is newly introduced to evaluate the amount of confinement improvement in the H-mode phase compared with the L-mode phase in a single discharge. H{sub exp} exhibits that the global energy confinement time of the H-mode phase is improved about 1.3 - 2.0 times compared with that of the L-mode phase. Finally, interpretive and predictive numerical simulations are carried out using the ASTRA code for typical KSTAR H-mode discharges. The Weiland model and the GLF23 model are employed for calculating the anomalous contributions of both electron and ion heat transport in predictive simulations. For the H-mode phase, the Weiland model reproduces the experiment

Single Pt Atoms Confined into a Metal-Organic Framework for Efficient Photocatalysis.

Science.gov (United States)

Fang, Xinzuo; Shang, Qichao; Wang, Yu; Jiao, Long; Yao, Tao; Li, Yafei; Zhang, Qun; Luo, Yi; Jiang, Hai-Long

2018-02-01

It is highly desirable yet remains challenging to improve the dispersion and usage of noble metal cocatalysts, beneficial to charge transfer in photocatalysis. Herein, for the first time, single Pt atoms are successfully confined into a metal-organic framework (MOF), in which electrons transfer from the MOF photosensitizer to the Pt acceptor for hydrogen production by water splitting under visible-light irradiation. Remarkably, the single Pt atoms exhibit a superb activity, giving a turnover frequency of 35 h -1 , ≈30 times that of Pt nanoparticles stabilized by the same MOF. Ultrafast transient absorption spectroscopy further unveils that the single Pt atoms confined into the MOF provide highly efficient electron transfer channels and density functional theory calculations indicate that the introduction of single Pt atoms into the MOF improves the hydrogen binding energy, thus greatly boosting the photocatalytic H 2 production activity. © 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Synthesis of Polyimides in Molecular-Scale Confinement for Low-Density Hybrid Nanocomposites.

Science.gov (United States)

Isaacson, Scott G; Fostvedt, Jade I; Koerner, Hilmar; Baur, Jeffery W; Lionti, Krystelle; Volksen, Willi; Dubois, Geraud; Dauskardt, Reinhold H

2017-11-08

In this work, we exploit a confinement-induced molecular synthesis and a resulting bridging mechanism to create confined polyimide thermoset nanocomposites that couple molecular confinement-enhanced toughening with an unprecedented combination of high-temperature properties at low density. We describe a synthesis strategy that involves the infiltration of individual polymer chains through a nanoscale porous network while simultaneous imidization reactions increase the molecular backbone stiffness. In the extreme limit where the confinement length scale is much smaller than the polymer's molecular size, confinement-induced molecular mechanisms give rise to exceptional mechanical properties. We find that polyimide oligomers can undergo cross-linking reactions even in such molecular-scale confinement, increasing the molecular weight of the organic phase and toughening the nanocomposite through a confinement-induced energy dissipation mechanism. This work demonstrates that the confinement-induced molecular bridging mechanism can be extended to thermoset polymers with multifunctional properties, such as excellent thermo-oxidative stability and high service temperatures (>350 °C).

Energy confinement comparison of ohmically heated stellarators to tokamaks

International Nuclear Information System (INIS)

Chu, T.K.; Lee, Y.C.

1979-12-01

An empirical scaling prescribes that the energy confinement time in ohmically heated stellarators and tokamaks is proportional to the internal energy of the plasma and the minor radius, and inversely proportional to the current density. A thermal-conduction energy transport model, based on a heuristic assumption that the effective momentum transfer in the radial direction is proportional to the classical parallel momentum transfer which results in ohmic heating, is used to explain this scaling

Neutron Assay System for Confinement Vessel Disposition

International Nuclear Information System (INIS)

Frame, Katherine C.; Bourne, Mark M.; Crooks, William J.; Evans, Louise; Mayo, Douglas R.; Miko, David K.; Salazar, William R.; Stange, Sy; Valdez, Jose I.; Vigil, Georgiana M.

2012-01-01

Los Alamos National Laboratory has a number of spherical confinement vessels (CVs) remaining from tests involving nuclear materials. These vessels have an inner diameter of 6 feet with 1-inch thick steel walls. The goal of the Confinement Vessel Disposition (CVD) project is to remove debris and reduce contamination inside the CVs. The Confinement Vessel Assay System (CVAS) was developed to measure the amount of special nuclear material (SNM) in CVs before and after cleanout. Prior to cleanout, the system will be used to perform a verification measurement of each vessel. After cleanout, the system will be used to perform safeguards-quality assays of (le)100-g 239 Pu equivalent in a vessel for safeguards termination. The CVAS has been tested and calibrated in preparation for verification and safeguards measurements.

Plasma confinement of Nagoya high-beta toroidal-pinch experiments

International Nuclear Information System (INIS)

Hirano, K.; Kitagawa, S.; Wakatani, M.; Kita, Y.; Yamada, S.; Yamaguchi, S.; Sato, K.; Aizawa, T.; Osanai, Y.; Noda, N.

1977-01-01

Two different types of high-β toroidal pinch experiments, STP [1] and CCT [2,3], have been done to study the confinement of the plasma produced by a theta-pinch. The STP is an axisymmetric toroidal pinch of high-β tokamak type, while the CCT consists of multiply connected periodic toroidal traps. Internal current-carrying copper rings are essential to the CCT. Since both apparatuses use the same fast capacitor bank system, they produce rather similar plasma temperatures and densities. The observed laser scattering temperature and density is about 50 eV and 4x10 15 cm -3 , respectively, when the filling pressure is 5 mtorr. In the STP experiment, strong correlations are found between the βsub(p) value and the amplitude of m=2 mode. It has a minimum around the value of βsub(p) of 0.8. The disruptive instability is observed to expand the pinched plasma column without lowering the plasma temperature. Just before the disruption begins, the q value around the magnetic axis becomes far less than 1 and an increase of the amplitude of m=2 mode is seen. The CCT also shows rapid plasma expansion just before the magnetic field reaches its maximum. Then the trap is filled up with the plasma by this irreversible expansion and stable plasma confinement is achieved. The energy confinement time of the CCT is found to be about 35 μs. (author)

Studies on the quark confinement in a non-relativistic quark model

International Nuclear Information System (INIS)

Pfenninger, T.

1988-01-01

In the framework of the non-relativistic quark model we have studied several aspects of the description of the confinement by a confinement potential. A first consideration applied to the effects of the long-range color van-der-Waals forces on the nucleon-nucleon scattering. Regarding color dipole states as an additional closed channel in a dynamical and nonlocal resonating-group calculation we found a strong attraction. Additionally it was possible by means of the RGM kernels to derive an against earlier calculations improved color van-der-Waals potential in adiabatic approximation which regards correctly the internal kinetic and the confinement energy of the color octet states. This potential is not confined to large NN distances and shows asymptotically a 1/R 2 behaviour if it is based on a harmonic confinement. A further study applied to the question how far a possible vector character of the confinement, which is suggested by the elementary quark-gluon vertex, has effects on baryon properties and the NN interaction. Here it resulted that the vector confinement reacts in view of the model parameters very sensitively in the baryon properties whereas the scalar confinement did not show this dependence. In the NN scattering this vector confinement however plays a more secondary role. Because of the difficulties of the usual confinement potential with long-range color van-der-Waals forces we proposed in the last part a new potential and additional orthogonality relations for the quark wave functions in order to accomodate in the potential model to the string degrees of freedom. In scattering calculations we again studied the effects of the modification on the NN interaction. (orig./HSI) [de

Confined exciton spectroscopy

International Nuclear Information System (INIS)

Torres, Clivia M.S.

1998-01-01

Full text: In this work, the exciton is considered as a sensor of the electronic and optical properties of materials such as semiconductors, which have size compared to the exciton De Broglie wavelength, approximately 20 nm, depending on the semiconductor. Examples of electron-phonon, electron-electron, photon-electron, exciton-polariton, phonon-plasmon, are presented, under different confinement conditions such as quantum wells, superlattices

Alternative lines with magnetic plasma confinement

International Nuclear Information System (INIS)

Wobig, H.

1981-01-01

Plasma confinement with the aid of a magnetic field is the most common and also the most frequently investigated principle on the way to controlled nuclear fusion. Apart from the Tokamak principle, which is the most advanced principle as far as fusion-relevant plasma parameters are concerned, also other approaches are being investigated, e.g. the mirror device, the bumpy tons, and the stellarator. In principle, all three concepts permit 'stationary' plasma confinement in a stationary fusion reactor. Compared with the pulsed Tokamak reactor, this is a considerable advantage. (orig./GG) [de

Magnetic properties of confined electron gas

International Nuclear Information System (INIS)

Felicio, J.R.D. de.

1977-04-01

The effects of confinement by a two or three-dimensional harmonic potential on the magnetic properties of a free electron gas are investigated using the grand-canonical ensemble framework. At high temperatures an extension of Darwin's, Felderhof and Raval's works is made taking into account spin effects at low temperature. A comprehensive description of the magnetic properties of a free electron gas is given. The system is regarded as finite, but the boundary condition psi=0 is not introduced. The limits of weak and strong confinement are also analysed [pt

Impact of hydrogen fuelling on confinement properties in radiative improved mode

International Nuclear Information System (INIS)

Kalupin, D; Dumortier, P; Messiaen, A; Tokar, M Z; Unterberg, B; Verdoolaege, Geert; Wassenhove, G Van; Weynants, R

2003-01-01

The radiative improved (RI) mode at TEXTOR is a high confinement regime, which is obtained by the seeding of neon into deuterium plasmas. Recent experiments were aimed to study the influence of external gas fuelling on the confinement properties of the RI mode. In particular, it was found that a hydrogen puff into such plasmas leads to lower confinement compared with the discharges fuelled with the same amount of deuterium gas. This paper attempts to explain the reduction of confinement in RI plasmas with an external hydrogen puff and its relation to the level of impurity concentration, which is a critical parameter for RI mode confinement

Confinement and surface effects on the physical properties of rhombohedral-shape hematite (α-Fe_2O_3) nanocrystals

International Nuclear Information System (INIS)

Luna, Carlos; Cuan-Guerra, Aída D.; Barriga-Castro, Enrique D.; Núñez, Nuria O.; Mendoza-Reséndez, Raquel

2016-01-01

Highlights: • Uniform rhombohedral hematite nanocrystals (RHNCs) have been obtained. • A detailed formation mechanism of these HNCS has been proposed. • Phonon confinement effects were revealed in the RHNCS vibrational bands. • Quantum confinement effects on the optical and electronic properties were found. - Abstract: Morphological, microstructural and vibrational properties of hematite (α-Fe_2O_3) nanocrystals with a rhombohedral shape and rounded edges, obtained by forced hydrolysis of iron(III) solutions under a fast nucleation, have been investigated in detail as a function of aging time. These studies allowed us to propose a detailed formation mechanism and revealed that these nanocrystals are composed of four {104} side facets, two {110} faces at the edges of the long diagonal of the nanocrystals and two {−441} facets as the top and bottom faces. Also, the presence of nanoscopic pores and fissures was evidenced. The vibrational bands of such nanocrystals were shifted to lower frequencies in comparison with bulk hematite ones as the nanocrystal size was reduced due to phonon confinement effects. Also, the indirect and direct transition band gaps displayed interesting dependences on the aging time arising from quantum confinement and surface effects

Ohmic H-mode and confinement in TCV

International Nuclear Information System (INIS)

Moret, J.M.; Anton, M.; Barry, S.

1995-01-01

The unique flexibility of TCV for the creation of a wide variety of plasma shapes has been exploited to address some aspects of tokamak physics for which the shape may play an important role. The electron energy confinement time in limited ohmic L-mode plasmas whose elongation and triangularity have been varied, has been observed to improve with elongation as κ 0.5 but to degrade with triangularity as (1-0.8 δ), for fixed safety factor. Ohmic H-modes have been obtained in several diverted and limited configurations, with some of the diverted discharges featuring large ELMs whose effects on the global confinement have been quantified. These effects depend on the configuration: in double null (DN) equilibria, a single ELM expels on average 2%, 6% and 2.5% of the particle, impurity and thermal energy content respectively, whilst in single null (SN) configurations, the corresponding numbers are 3.5%, 7% and 9%, indicative of larger ELM effects. The presence or absence of large ELMs in DN discharges has been actively controlled in a single discharge by alternately forcing one or other of the two X-points to lie on the separatrix, permitting stationary density and impurity content (Z eff ≅1.6) in long H-modes (1.5 s). (author) 9 figs., 9 refs

Modèle de confinement pour les colonnes de section circulaire en béton armé confiné avec des enveloppes en polymère renforcé de fibres de carbone Confinement model for circular RC columns wrapped with CFRP composite

Directory of Open Access Journals (Sweden)

Benzaid R.

2012-09-01

Full Text Available Un programme experimental comprenant des essais sur 30 cylindres 160×320 mm a ete mene en vue de determiner le gain de resistance et de ductilite du beton confine par collage externe de tissu de polymere renforce de fibres de carbone (PRFC. Les variables etudiees sont la resistance a la compression du beton non confine f’co, le niveau de confinement, exprime par le nombre de plis de PRFC applique aux eprouvettes. La deformation circonferentielle a la rupture du composite PRF et l’feffet de la pression de confinement laterale effective de l’fenveloppe composite ont ete egalement etudies. Pour l’fensemble des specimens testes, l’faugmentation de la rigidite du confinement entraine a la fois une augmentation significative de la resistance a la compression axiale et de la ductilite des specimens en beton confine avec des PRFC par rapport aux specimens en beton non confine. Base sur les resultats experimentaux, un modele de confinement pratique est propose pour predire la resistance a la compression maximale du beton confine avec des materiaux composites (f’cc et la deformation axiale correspondante (εcc. The present paper deals with the analysis of experimental results, in terms of load carrying capacity and strains, obtained from tests on plain- and reinforced- concrete (RC cylinder, strengthened with external carbon-fiber-reinforced polymer (CFRP. The parameters considered are the number of composite layers, the compressive strength of unconfined concrete. The effective circumferential FRP failure strain and the effect of the effective lateral confining pressure were investigated. Totally thirty cylinders (160×320 mm were subjected to axial compression which includes control specimens. All the test specimens were loaded to failure in axial compression and the behaviour of the specimens in the axial and transverse directions was investigated. Test results shown that the CFRP wrap increases the strength and ductility of reinforced

Laser drivers for inertial confinement fusion

International Nuclear Information System (INIS)

Holzrichter, J.F.

1983-01-01

Inertial Confinement Fusion (ICF) is the technology that we are developing to access the vast stored energy potential of deuterium fuel located in the world's water supply. This form of fusion is accomplished by compressing and heating small volumes of D-T fuel to very high temperatures (greater than 100M 0 C) and to very high densities (greater than 1000 times the normal liquid density). Under these fuel conditions, a thermonuclear reaction can occur, leading to a net energy release compared to the energy used to heat the fuel initially. To accomplish the condition where fusion reactions begin, effective drivers are required. These are lasers or particle beam accelerators which can provide greater than 10 14 W/cm 2 over millimeter scale targets with an appropriately programmed intensity vs time. At present, we are using research lasers to obtain an understanding of the physics and engineering of fuel compression

General approach to polymer chains confined by interacting boundaries.

Science.gov (United States)

Freed, Karl F; Dudowicz, Jacek; Stukalin, Evgeny B; Douglas, Jack F

2010-09-07

Polymer chains, confined to cavities or polymer layers with dimensions less than the chain radius of gyration, appear in many phenomena, such as gel chromatography, rubber elasticity, viscolelasticity of high molar mass polymer melts, the translocation of polymers through nanopores and nanotubes, polymer adsorption, etc. Thus, the description of how the constraints alter polymer thermodynamic properties is a recurrent theoretical problem. A realistic treatment requires the incorporation of impenetrable interacting (attractive or repulsive) boundaries, a process that introduces significant mathematical complications. The standard approach involves developing the generalized diffusion equation description of the interaction of flexible polymers with impenetrable confining surfaces into a discrete eigenfunction expansion, where the solutions are normally truncated at the first mode (the "ground state dominance" approximation). This approximation is mathematically well justified under conditions of strong confinement, i.e., a confinement length scale much smaller than the chain radius of gyration, but becomes unreliable when the polymers are confined to dimensions comparable to their typically nanoscale size. We extend a general approach to describe polymers under conditions of weak to moderate confinement and apply this semianalytic method specifically to determine the thermodynamics and static structure factor for a flexible polymer confined between impenetrable interacting parallel plate boundaries. The method is first illustrated by analyzing chain partitioning between a pore and a large external reservoir, a model system with application to chromatography. Improved agreement is found for the partition coefficients of a polymer chain in the pore geometry. An expression is derived for the structure factor S(k) in a slit geometry to assist in more accurately estimating chain dimensions from scattering measurements for thin polymer films.

Study of confinement and sliding friction of fluids using sum frequency generation spectroscopy

Science.gov (United States)

Nanjundiah, Kumar

2007-12-01

presence of peaks related to PDMS, as well as water, suggested water puddles in the contact area and the sapphire surface had a layer of bound water. This heterogeneity picture provides insight into high friction and stick-slip behavior found in boundary lubrication. For the first time, a broadband SFG system has been coupled with a friction cell to study dynamics and molecular changes at an interface during sliding; sliding of confined alkane between sapphire and PDMS was investigated. A series of SFG spectra were taken while the confined alkane contact spot moved in and out of the laser beam. Even though the experiments were done 15°C above melting temperature, the spectra showed ordering of alkane molecules, similar to that of the confined crystal at the leading and trailing edge. The results suggest that a large portion of the resistance to sliding may come from ordering of molecules at the lens front.

Thermodynamics of partially confined Fermi gases at low temperature

International Nuclear Information System (INIS)

Toms, David J

2004-01-01

We examine the behaviour of non-interacting Fermi gases at low temperature. If there is a confining potential present the thermodynamic behaviour is altered from the familiar results for the unconfined gas. The role of de Haas-van Alphen type oscillations that are a consequence of the confining potential is considered. Attention is concentrated on the behaviour of the chemical potential and the specific heat. Results are compared and contrasted with those for an unconfined and a totally confined gas

Ignitor physics assessment and confinement projections

International Nuclear Information System (INIS)

Horton, W.; Porcelli, F.; Zhu, P.; Aydemir, A.; Tajima, T.; Kishimoto, Y.

2001-01-01

An independent assessment is presented of the physics of Ignitor, a physics demonstration experiment for achieving thermonuclear ignition (where fusion alpha heating compensates for all forms of energy losses). Simulations show that a pulse of particle power up to 10-20 MW is produced for a few seconds. Crucial issues are the production of peaked density profiles over several energy confinement times, the control of current penetration for the optimization of ohmic heating, and sawtooth avoidance. The presence of a 10-20 MW ion cyclotron radio frequency system and the operation of a high-speed pellet injector are considered essential to provide added flexibility in order to counter unexpected, adverse plasma behavior. (author)

Confined-but-Connected Quantum Solids via Controlled Ligand Displacement

KAUST Repository

Baumgardner, William J.; Whitham, Kevin; Hanrath, Tobias

2013-01-01

Confined-but-connected quantum dot solids (QDS) combine the advantages of tunable, quantum-confined energy levels with efficient charge transport through enhanced electronic interdot coupling. We report the fabrication of QDS by treating self

CCSD(T) calculations of stabilities and properties of confined systems

Energy Technology Data Exchange (ETDEWEB)

Holka, F.; Urban, M. [Slovak University of Technology in Bratislava, Faculty of Materials Science and Technology in Trnava, Institute of Materials Science, Bottova 25, SK-917 24 Trnava (Slovakia); Melicherčík, M.; Neogrády, P. [Department of Physical and Theoretical Chemistry, Faculty of Natural Sciences, Comenius University, Mlynská dolina, SK-842 15 Bratislava (Slovakia); Paldus, J. [Department of Applied Mathematics, University of Waterloo, N2L 3G1, Ontario (Canada)

2015-01-22

We analyze energies, electron affinities and polarizabilities of small anions exposed to an external confinement. The second electron in free O{sup 2−} and S{sup 2−} anions is unbound. We investigate the stabilizing effect of the spherical harmonic-oscillator confining potential ω. on these anions employing the Hartree-Fock stability analysis as introduced by Čížek and Paldus. With increasing strength of the external harmonic-oscillator confinement potential ω the broken symmetry (BS) solutions are systematically eliminated. For ω larger than 0.1 all BS solutions for O{sup 2−} disappear. For ω larger than 0.13 the CCSD(T) energy of O{sup 2−} becomes more negative than the energy of the singly charged O{sup −} anion. We relate the harmonic-oscillator confining potential to a crystalline environment in which the O{sup 2−} and S{sup 2−} anions are stable. We also present a model allowing calculations of the in-crystal polarizabilities of anions. The model is based on CCSD(T) calculations of static polarizabilities of selected anions exposed to the spherical harmonic-oscillator confining potential ω This artificial confinement potential ω is then related to the ionic radii of the cation in representative crystal lattices. We investigate the polarizability of O{sup 2−} and S{sup 2−} anions in MgO, MgS, CaO, CaS, SrO, SrS, BaO and BaS crystals. We compare our results with alternative models for in-crystal polarizabilities. External confinement also stabilizes the uracil anion U{sup −}, as is shown by calculations with a stepwise micro-hydration of U{sup −}. Upon hydration is the CCSD(T) adiabatic electron affinity (AEA) of uracil enhanced by about 250 up to 570 meV in comparison with AEA of the isolated molecule, depending on the geometry of the hydrated uracil anion complex. We tried to find an analogy of the stabilization effect of the external confinement on the otherwise unstable anions. In uracil and its anion is the external

Spin waves propagation and confinement in magnetic microstructures

International Nuclear Information System (INIS)

Bailleul, Matthieu

2002-01-01

In this thesis, ferromagnetic thin film elements have been studied on a small scale (μm) and at high frequencies (GHz). For those studies, a microwave spectrometer based on the use of micro-antennae has been developed. It had been applied to two different systems. In a first time, we have launched and detected spin waves in continuous films. This allowed us to describe both the transduction process and the relaxation law for long wavelength spin waves. In a second time, we have studied micrometer-wide stripe for which the magnetic ground state is inhomogeneous. The obtained microwave response has been interpreted in terms of micro-magnetic phase transitions and in terms of spin waves confinement. (author)

Directed transport of confined Brownian particles with torque

Science.gov (United States)

Radtke, Paul K.; Schimansky-Geier, Lutz

2012-05-01

We investigate the influence of an additional torque on the motion of Brownian particles confined in a channel geometry with varying width. The particles are driven by random fluctuations modeled by an Ornstein-Uhlenbeck process with given correlation time τc. The latter causes persistent motion and is implemented as (i) thermal noise in equilibrium and (ii) noisy propulsion in nonequilibrium. In the nonthermal process a directed transport emerges; its properties are studied in detail with respect to the correlation time, the torque, and the channel geometry. Eventually, the transport mechanism is traced back to a persistent sliding of particles along the even boundaries in contrast to scattered motion at uneven or rough ones.

Gate-defined Quantum Confinement in Suspended Bilayer Graphene

Science.gov (United States)

Allen, Monica

2013-03-01

Quantum confined devices in carbon-based materials offer unique possibilities for applications ranging from quantum computation to sensing. In particular, nanostructured carbon is a promising candidate for spin-based quantum computation due to the ability to suppress hyperfine coupling to nuclear spins, a dominant source of spin decoherence. Yet graphene lacks an intrinsic bandgap, which poses a serious challenge for the creation of such devices. We present a novel approach to quantum confinement utilizing tunnel barriers defined by local electric fields that break sublattice symmetry in suspended bilayer graphene. This technique electrostatically confines charges via band structure control, thereby eliminating the edge and substrate disorder that hinders on-chip etched nanostructures to date. We report clean single electron tunneling through gate-defined quantum dots in two regimes: at zero magnetic field using the energy gap induced by a perpendicular electric field and at finite magnetic fields using Landau level confinement. The observed Coulomb blockade periodicity agrees with electrostatic simulations based on local top-gate geometry, a direct demonstration of local control over the band structure of graphene. This technology integrates quantum confinement with pristine device quality and access to vibrational modes, enabling wide applications from electromechanical sensors to quantum bits. More broadly, the ability to externally tailor the graphene bandgap over nanometer scales opens a new unexplored avenue for creating quantum devices.

Computer simulation of confined liquid crystal dynamics

International Nuclear Information System (INIS)

Webster, R.E.

2001-11-01

Results are presented from a series of simulations undertaken to determine whether dynamic processes observed in device-scale liquid crystal cells confined between aligning substrates can be simulated in a molecular system using parallel molecular dynamics of the Gay-Berne model. In a nematic cell, on removal of an aligning field, initial near-surface director relaxation can induce flow, termed 'backflow' in the liquid. This, in turn, can cause director rotation, termed 'orientational kickback', in the centre of the cell. Simulations are performed of the relaxation in nematic systems confined between substrates with a common alignment on removal of an aligning field. Results show /that relaxation timescales of medium sized systems are accessible. Following this, simulations are performed of relaxation in hybrid aligned nematic systems, where each surface induces a different alignment. Flow patterns associated with director reorientation are observed. The damped oscillatory nature of the relaxation process suggests that the behaviour of these systems is dominated by orientational elastic forces and that the observed director motion and flow do not correspond to the macroscopic processes of backflow and kickback. Chevron structures can occur in confined smectic cells which develop two domains of equal and opposite layer tilt on cooling. Layer lilting is thought to be caused by a need to reconcile a mismatch between bulk and surface smectic layer spacing. Here, simulations are performed of the formation of structures in confined smectic systems where layer tilt is induced by an imposed surface pretilt. Results show that bookshelf, chevron and tilled layer structures are observable in a confined Gay-Berne system. The formation and stability of the chevron structure are shown to be influenced by surface slip. (author)

Wild trout responses to a stress experience following confinement conditions during the spawning season

Directory of Open Access Journals (Sweden)

Gilberto Forneris

2010-01-01

-term confinement in artificial environment without refuges or due to “chronic” stress. Furthermore our data demonstrate that cortisolemia is not adequate as a marker for chronic stress but cortisol response to serial acute stress, in relation to time, can be used for the monitoring of stress level and welfare in trout breeders during confinement. The use of refuges and shadow in the artificial environment shown to play a relevant role in the survival of wild breeders of trout during confinement in the spawning season.

Somersault of Paramecium in extremely confined environments

Science.gov (United States)

Jana, Saikat; Eddins, Aja; Spoon, Corrie; Jung, Sunghwan

2015-08-01

We investigate various swimming modes of Paramecium in geometric confinements and a non-swimming self-bending behavior like a somersault, which is quite different from the previously reported behaviors. We observe that Paramecia execute directional sinusoidal trajectories in thick fluid films, whereas Paramecia meander around a localized region and execute frequent turns due to collisions with adjacent walls in thin fluid films. When Paramecia are further constrained in rectangular channels narrower than the length of the cell body, a fraction of meandering Paramecia buckle their body by pushing on the channel walls. The bucking (self-bending) of the cell body allows the Paramecium to reorient its anterior end and explore a completely new direction in extremely confined spaces. Using force deflection method, we quantify the Young’s modulus of the cell and estimate the swimming and bending powers exerted by Paramecium. The analysis shows that Paramecia can utilize a fraction of its swimming power to execute the self-bending maneuver within the confined channel and no extra power may be required for this new kind of self-bending behavior. This investigation sheds light on how micro-organisms can use the flexibility of the body to actively navigate within confined spaces.

Chemical reactions confined within carbon nanotubes.

Science.gov (United States)

Miners, Scott A; Rance, Graham A; Khlobystov, Andrei N

2016-08-22

In this critical review, we survey the wide range of chemical reactions that have been confined within carbon nanotubes, particularly emphasising how the pairwise interactions between the catalysts, reactants, transition states and products of a particular molecular transformation with the host nanotube can be used to control the yields and distributions of products of chemical reactions. We demonstrate that nanoscale confinement within carbon nanotubes enables the control of catalyst activity, morphology and stability, influences the local concentration of reactants and products thus affecting equilibria, rates and selectivity, pre-arranges the reactants for desired reactions and alters the relative stability of isomeric products. We critically evaluate the relative advantages and disadvantages of the confinement of chemical reactions inside carbon nanotubes from a chemical perspective and describe how further developments in the controlled synthesis of carbon nanotubes and the incorporation of multifunctionality are essential for the development of this ever-expanding field, ultimately leading to the effective control of the pathways of chemical reactions through the rational design of multi-functional carbon nanoreactors.

Operational technology for greater confinement disposal

International Nuclear Information System (INIS)

Dickman, P.T.; Vollmer, A.T.; Hunter, P.H.

1984-12-01

Procedures and methods for the design and operation of a greater confinement disposal facility using large-diameter boreholes are discussed. It is assumed that the facility would be located at an operating low-level waste disposal site and that only a small portion of the wastes received at the site would require greater confinement disposal. The document is organized into sections addressing: facility planning process; facility construction; waste loading and handling; radiological safety planning; operations procedures; and engineering cost studies. While primarily written for low-level waste management site operators and managers, a detailed economic assessment section is included that should assist planners in performing cost analyses. Economic assessments for both commercial and US government greater confinement disposal facilities are included. The estimated disposal costs range from $27 to $104 per cubic foot for a commercial facility and from $17 to $60 per cubic foot for a government facility. These costs are based on average site preparation, construction, and waste loading costs for both contact- and remote-handled wastes. 14 figures, 22 tables

Results from deuterium-tritium tokamak confinement experiments

International Nuclear Information System (INIS)

Hawryluk, R.J.

1997-02-01

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

System and method of operating toroidal magnetic confinement devices

Science.gov (United States)

Chance, M.S.; Jardin, S.C.; Stix, T.H.; Grimm, R.C.; Manickam, J.; Okabayashi, M.

1984-08-30

This invention pertains to methods and arrangements for attaining high beta values in plasma confinement devices. More specifically, this invention pertains to methods for accessing the second stability region of operation in toroidal magnetic confinement devices.

Dynamics of proteins aggregation. II. Dynamic scaling in confined media

Science.gov (United States)

Zheng, Size; Shing, Katherine S.; Sahimi, Muhammad

2018-03-01

In this paper, the second in a series devoted to molecular modeling of protein aggregation, a mesoscale model of proteins together with extensive discontinuous molecular dynamics simulation is used to study the phenomenon in a confined medium. The medium, as a model of a crowded cellular environment, is represented by a spherical cavity, as well as cylindrical tubes with two aspect ratios. The aggregation process leads to the formation of β sheets and eventually fibrils, whose deposition on biological tissues is believed to be a major factor contributing to many neuro-degenerative diseases, such as Alzheimer's, Parkinson's, and amyotrophic lateral sclerosis diseases. Several important properties of the aggregation process, including dynamic evolution of the total number of the aggregates, the mean aggregate size, and the number of peptides that contribute to the formation of the β sheets, have been computed. We show, similar to the unconfined media studied in Paper I [S. Zheng et al., J. Chem. Phys. 145, 134306 (2016)], that the computed properties follow dynamic scaling, characterized by power laws. The existence of such dynamic scaling in unconfined media was recently confirmed by experiments. The exponents that characterize the power-law dependence on time of the properties of the aggregation process in spherical cavities are shown to agree with those in unbounded fluids at the same protein density, while the exponents for aggregation in the cylindrical tubes exhibit sensitivity to the geometry of the system. The effects of the number of amino acids in the protein, as well as the size of the confined media, have also been studied. Similarities and differences between aggregation in confined and unconfined media are described, including the possibility of no fibril formation, if confinement is severe.

Fractional Brownian motion and motion governed by the fractional Langevin equation in confined geometries.

Science.gov (United States)

Jeon, Jae-Hyung; Metzler, Ralf

2010-02-01

Motivated by subdiffusive motion of biomolecules observed in living cells, we study the stochastic properties of a non-Brownian particle whose motion is governed by either fractional Brownian motion or the fractional Langevin equation and restricted to a finite domain. We investigate by analytic calculations and simulations how time-averaged observables (e.g., the time-averaged mean-squared displacement and displacement correlation) are affected by spatial confinement and dimensionality. In particular, we study the degree of weak ergodicity breaking and scatter between different single trajectories for this confined motion in the subdiffusive domain. The general trend is that deviations from ergodicity are decreased with decreasing size of the movement volume and with increasing dimensionality. We define the displacement correlation function and find that this quantity shows distinct features for fractional Brownian motion, fractional Langevin equation, and continuous time subdiffusion, such that it appears an efficient measure to distinguish these different processes based on single-particle trajectory data.

Tritium burning in inertial electrostatic confinement fusion facility

Energy Technology Data Exchange (ETDEWEB)

Ohnishi, Masami, E-mail: onishi@kansai-u.ac.jp [Department of Science and Engineering, Kansai University, 3-3-35 Yamate-cho, Suita, Osaka 564-8680 (Japan); Yamamoto, Yasushi; Osawa, Hodaka [Department of Science and Engineering, Kansai University, 3-3-35 Yamate-cho, Suita, Osaka 564-8680 (Japan); Hatano, Yuji; Torikai, Yuji [Hydrogen Isotope Science Center, University of Toyama, Gofuku, Toyama 930-8555 (Japan); Murata, Isao [Faculty of Engineering Environment and Energy Department, Osaka University, 2-1 Yamadaoka, Suita, Osaka 565-0871 (Japan); Kamakura, Keita; Onishi, Masaaki; Miyamoto, Keiji; Konda, Hiroki [Department of Science and Engineering, Kansai University, 3-3-35 Yamate-cho, Suita, Osaka 564-8680 (Japan); Masuda, Kai [Institute of Advanced Energy, Kyoto University, Gokasho, Uji, Kyoto 611-0011 (Japan); Hotta, Eiki [Interdisciplinary Graduate School of Science and Engineering, Tokyo Institute of Technology, 4259 Nagatsuda-cho, Midori-ku, Yokohama 226-8503 (Japan)

2016-11-01

Highlights: • An experiment on tritium burning is conducted in an inertial electrostatic confinement fusion (IECF) facility. • A deuterium–tritium gas mixture with 93% deuterium and 7% tritium is used. • The neutron production rate is measured to be 5–8 times more than that of pure deuterium gas. • The neutron production rate of the D–T gas mixture in 1:1 ratio is expected to be more than 10{sup 8}(1/sec) in the present D–T experiment. - Abstract: An experiment on tritium burning is conducted to investigate the enhancement in the neutron production rate in an inertial electrostatic confinement fusion (IECF) facility. The facility is designed such that it is shielded from the outside for safety against tritium and a getter pump is used for evacuating the vacuum chamber and feeding the fuel gas. A deuterium–tritium gas mixture with 93% deuterium and 7% tritium is used, and its neutron production rate is measured to be 5–8 times more than that of pure deuterium gas. Moreover, the results show good agreement with those of a simplified theoretical estimation of the neutron production rate. After tritium burning, the exhausted fuel gas undergoes a tritium recovery procedure through a water bubbler device. The amount of gaseous tritium released by the developed IECF facility after tritium burning is verified to be much less than the threshold set by regulations.

Tritium burning in inertial electrostatic confinement fusion facility

International Nuclear Information System (INIS)

Ohnishi, Masami; Yamamoto, Yasushi; Osawa, Hodaka; Hatano, Yuji; Torikai, Yuji; Murata, Isao; Kamakura, Keita; Onishi, Masaaki; Miyamoto, Keiji; Konda, Hiroki; Masuda, Kai; Hotta, Eiki

2016-01-01

Highlights: • An experiment on tritium burning is conducted in an inertial electrostatic confinement fusion (IECF) facility. • A deuterium–tritium gas mixture with 93% deuterium and 7% tritium is used. • The neutron production rate is measured to be 5–8 times more than that of pure deuterium gas. • The neutron production rate of the D–T gas mixture in 1:1 ratio is expected to be more than 10"8(1/sec) in the present D–T experiment. - Abstract: An experiment on tritium burning is conducted to investigate the enhancement in the neutron production rate in an inertial electrostatic confinement fusion (IECF) facility. The facility is designed such that it is shielded from the outside for safety against tritium and a getter pump is used for evacuating the vacuum chamber and feeding the fuel gas. A deuterium–tritium gas mixture with 93% deuterium and 7% tritium is used, and its neutron production rate is measured to be 5–8 times more than that of pure deuterium gas. Moreover, the results show good agreement with those of a simplified theoretical estimation of the neutron production rate. After tritium burning, the exhausted fuel gas undergoes a tritium recovery procedure through a water bubbler device. The amount of gaseous tritium released by the developed IECF facility after tritium burning is verified to be much less than the threshold set by regulations.

Enhanced ionic liquid mobility induced by confinement in 1D CNT membranes

Science.gov (United States)

Berrod, Q.; Ferdeghini, F.; Judeinstein, P.; Genevaz, N.; Ramos, R.; Fournier, A.; Dijon, J.; Ollivier, J.; Rols, S.; Yu, D.; Mole, R. A.; Zanotti, J.-M.

2016-04-01

Water confined within carbon nanotubes (CNT) exhibits tremendous enhanced transport properties. Here, we extend this result to ionic liquids (IL) confined in vertically aligned CNT membranes. Under confinement, the IL self-diffusion coefficient is increased by a factor 3 compared to its bulk reference. This could lead to high power battery separators.Water confined within carbon nanotubes (CNT) exhibits tremendous enhanced transport properties. Here, we extend this result to ionic liquids (IL) confined in vertically aligned CNT membranes. Under confinement, the IL self-diffusion coefficient is increased by a factor 3 compared to its bulk reference. This could lead to high power battery separators. Electronic supplementary information (ESI) available. See DOI: 10.1039/c6nr01445c

How to Recharge a Confined Aquifer: An Exploration of Geologic Controls on Groundwater Storage.

Science.gov (United States)

Maples, S.; Fogg, G. E.; Maxwell, R. M.; Liu, Y.

2017-12-01

Decreased snowpack storage and groundwater overdraft in California has increased interest in managed aquifer recharge (MAR) of excess winter runoff to the Central Valley aquifer system, which has unused storage capacity that far exceeds the state's surface reservoirs. Recharge to the productive, confined aquifer system remains a challenge due to the presence of nearly-ubiquitous, multiple silt and clay confining units that limit recharge pathways. However, previous studies have identified interconnected networks of sand and gravel deposits that bypass the confining units and accommodate rapid, high-volume recharge to the confined aquifer system in select locations. We use the variably-saturated, fully-integrated groundwater/surface-water flow code, ParFlow, in combination with a high-resolution, transition probability Markov-chain geostatistical model of the subsurface geologic heterogeneity of the east side of the Sacramento Valley, CA, to characterize recharge potential across a landscape that includes these geologic features. Multiple 180-day MAR simulations show that recharge potential is highly dependent on subsurface geologic structure, with a several order-of-magnitude range of recharge rates and volumes across the landscape. Where there are recharge pathways to the productive confined-aquifer system, pressure propagation in the confined system is widespread and rapid, with multi-kilometer lateral pressure propagation. Although widespread pressure propagation occurs in the confined system, only a small fraction of recharge volume is accommodated there. Instead, the majority of recharge occurs by filling unsaturated pore spaces. Where they outcrop at land surface, high-K recharge pathways fill rapidly, accommodating the majority of recharge during early time. However, these features become saturated quickly, and somewhat counterintuitively, the low-K silt and clay facies accommodate the majority of recharge volume during most of the simulation. These findings

Investigation of stress–strain models for confined high strength ...

Indian Academy of Sciences (India)

High strength concrete; confined concrete; stress–strain models; ... One of its advantages is the lessening column cross-sectional areas. It was ..... Ahmad S H, Shah S P 1982 Stress–strain curves of concrete confined by spiral reinforcement.

Proceedings of the workshop of three large tokamak cooperation on energy confinement scaling under intensive auxiliary heating, May 18 ∼ 20, 1992, Naka

International Nuclear Information System (INIS)

1992-09-01

The workshop of three large tokamak cooperation W22 on 'Energy confinement scaling under intensive auxiliary heating' was held 18-20 May, 1992, at Naka Fusion Research Establishment. This proceedings compiles 14 synopses of contributions (5 from JET, 4 from JT-60, 3 from TFTR, and 1 each from DIII-D JFT-2M) and the summary of the workshop. Topic sections are ; (i) L-mode confinement and scaling, (ii) Confinement at high β P regimes, Supershots, High poloidal beta enhanced confinement mode etc., (iii) Confinement at various H-mode regimes and scaling (including the VH-mode), (iv) Characteristic time scales for present tokamak regimes, and (v) Theoretical comparison with experimental data. (author)

Organ-confined prostate cancer: effect of prior transrectal biopsy on endorectal MRI and MR spectroscopic imaging

International Nuclear Information System (INIS)

Qayyum, Aliya; Coakley, F.V.; Lu, Y.; Olpin, J.D.; Wu, L.; Yeh, B.M.; Carroll, P.R.; Kurhanewicz, J.

2004-01-01

Objective: Our aim was to determine the effect of prior transrectal biopsy on endorectal MRI and MR spectroscopic imaging findings in patients with organ-confined prostate cancer. Materials and Methods: Endorectal MRI and MR spectroscopic imaging were performed in 43 patients with biopsy-proven prostate cancer before radical prostatectomy confirming organ-confined disease. For each sextant, two independent reviewers scored the degree of hemorrhage on a scale from 1 to 5 and recorded the presence or absence of capsular irregularity. A spectroscopist recorded the number of spectrally degraded voxels in the peripheral zone. The outcome variables of capsular irregularity and spectral degradation were correlated with the predictor variables of time from biopsy and degree of hemorrhage after biopsy. Results: Capsular irregularity was unrelated to time from biopsy or to degree of hemorrhage. Spectral degradation was inversely related to time from biopsy (p < 0.01); the mean percentage of degraded peripheral zone voxels was 18.5% within 8 weeks of biopsy compared with 7% after 8 weeks. Spectral degradation was unrelated to the degree of hemorrhage. Conclusion: In organ-confined prostate cancer, capsular irregularity can be seen at any time after biopsy and is independent of the degree of hemorrhage, whereas spectral degradation is seen predominantly in the first 8 weeks after biopsy. MRI staging criteria and guidelines for scheduling studies after biopsy may require appropriate modification. (author)

Effects of confinement in meso-porous silica and carbon nano-structures

International Nuclear Information System (INIS)

Leon, V.

2006-07-01

Physico-chemical properties of materials can be strongly modified by confinement because of the quantum effects that appear at such small length scales and also because of the effects of the confinement itself. The aim of this thesis is to show that both the nature of the confining material and the size of the pores and cavities have a strong impact on the confined material. We first show the effect of the pore size of the host meso-porous silica on the temperature of the solid-solid phase transition of silver selenide, a semiconducting material with enhanced magnetoresistive properties under non-stoichiometric conditions. Narrowing the pores from 20 nm to 2 nm raises the phase transition temperature from 139 C to 146 C. This result can be explained by considering the interaction between the confining and confined materials as a driving force. The effects of confinement are also studied in the case of hydrogen and deuterium inside cavities of organized carbon nano-structures. The effects that appear in the adsorption/desorption cycles are much stronger with carbon nano-horns as the host material than with C60 pea-pods and single-walled carbon nano-tubes. (author)

Charge confinements in CdSe-ZnSe symmetric double quantum wells

International Nuclear Information System (INIS)

Tit, Nacir; Obaidat, Ihab M

2008-01-01

The bound states in the (CdSe) N w (ZnSe) N b (CdSe) N w -ZnSe(001) symmetric double quantum wells are investigated versus the well width (N w ) and the barrier thickness (N b ). A calculation based on the sp 3 s * tight-binding method which includes the spin-orbit interactions is employed to calculate the bandgap energy, quantum-confinement energy, and band structures. The studied systems possess a vanishing valence-band offset (VBO = 0) in consistency with the well known common-anion rule, and a large conduction-band offset (CBO ≅ 1 eV), which plays an essential role in the confinement of electrons within the CdSe wells. The biaxial strain, on the other hand, plays another role in confining the holes at the interfaces (within the well regions) and thus enhancing the radiative efficiency. The induced-strain energy is estimated to be ∼35 meV. More importantly, the results show that, for a fixed barrier thickness, the double wells are able to confine a pair of bound states when they are very thin. By increasing the wells' width (N w ), further, a new pair of states from the conduction-band continuum falls into the wells every time N w hits a multiple of four monolayers (more specifically, for 4n w ≤4(n+1), the number of bound states is 2(n+1), where n is an integer). On the other hand, the barrier thickness (N b ) is shown to have no effect on the number of bound states, but it solely controls their well-to-well interactions. A critical barrier thickness to switch off these latter interactions is estimated to occur at about N crit b ≅ 9 (L crit b ≅ 25∼AA. Rules governing the variation of the quantum-confinement energy versus both barrier thickness (N b ) and well width (N w ) have been derived. Our theoretical results are also shown to have excellent agreement with the available experimental photoluminescence data

Confining but chirally symmetric dense and cold matter

International Nuclear Information System (INIS)

Glozman, L. Ya.

2012-01-01

The possibility for existence of cold, dense chirally symmetric matter with confinement is reviewed. The answer to this question crucially depends on the mechanism of mass generation in QCD and interconnection of confinement and chiral symmetry breaking. This question can be clarified from spectroscopy of hadrons and their axial properties. Almost systematical parity doubling of highly excited hadrons suggests that their mass is not related to chiral symmetry breaking in the vacuum and is approximately chirally symmetric. Then there is a possibility for existence of confining but chirally symmetric matter. We clarify a possible mechanism underlying such a phase at low temperatures and large density. Namely, at large density the Pauli blocking prevents the gap equation to generate a solution with broken chiral symmetry. However, the chirally symmetric part of the quark Green function as well as all color non-singlet quantities are still infrared divergent, meaning that the system is with confinement. A possible phase transition to such a matter is most probably of the first order. This is because there are no chiral partners to the lowest lying hadrons.

Molecular modeling in confined polymer and biomembrane systems

Directory of Open Access Journals (Sweden)

Jayeeta Ghosh

2009-07-01

Full Text Available The computational study of soft materials under confinement for bio- and nanotechnology still poses significantchallenges but has come a long way in the last decade. It is possible to realistically model and understand the fundamentalmechanisms which are at play if soft materials are confined to nanometer dimensions. Here, we present several recentexamples of such studies. Thin polymer films are abundantly used as friction modifiers or steric stabilizers. We show howsystematic modeling can shed light on the interplay between entropic and energetic interactions. Thin glassy films arecritical for the success of nanolithography. For that we have to understand the effect of confinement on the glass transitionbehavior in order to guarantee the stability and integrity of the lithographic masks. Simulations aim to understand the fundamental differences in the densities of states of glass formers in bulk and under confinement. With the advent of bionanotechnology the structure and phase behavior of lipid membranes as models for cellular membranes at the nano scale length is of importance due to implications in understanding the role of the lipids in biochemical membrane processes.

Dynamic Confinement of ITER Plasma by O-Mode Driver at Electron Cyclotron Frequency Range

Science.gov (United States)

Stefan, V. Alexander

2009-05-01

A low B-field side launched electron cyclotron O-Mode driver leads to the dynamic rf confinement, in addition to rf turbulent heating, of ITER plasma. The scaling law for the local energy confinement time τE is evaluated (τE ˜ 3neTe/2Q, where (3/2) neTe is the local plasma thermal energy density and Q is the local rf turbulent heating rate). The dynamics of unstable dissipative trapped particle modes (DTPM) strongly coupled to Trivelpiece-Gould (T-G) modes is studied for gyrotron frequency 170GHz; power˜24 MW CW; and on-axis B-field ˜ 10T. In the case of dynamic stabilization of DTPM turbulence and for the heavily damped T-G modes, the energy confinement time scales as τE˜(I0)-2, whereby I0(W/m^2) is the O-Mode driver irradiance. R. Prater et. al., Nucl. Fusion 48, No 3 (March 2008). E. P. Velikhov, History of the Russian Tokamak and the Tokamak Thermonuclear Fusion Research Worldwide That Led to ITER (Documentary movie; Stefan Studios Int'l, La Jolla, CA, 2008; E. P. Velikhov, V. Stefan.) M N Rosenbluth, Phys. Scr. T2A 104-109 1982 B. B. Kadomtsev and O. P. Pogutse, Nucl. Fusion 11, 67 (1971).

Transient drawdown solution for a constant pumping test in finite two-zone confined aquifers

Directory of Open Access Journals (Sweden)

C.-T. Wang

2012-02-01

Full Text Available The drawdown solution has been widely used to analyze pumping test data for the determination of aquifer parameters when coupled with an optimization scheme. The solution can also be used to predict the drawdown due to pumping and design the dewatering system. The drawdown solution for flow toward a finite-radius well with a skin zone in a confined aquifer of infinite extent in radial direction had been developed before. To our best knowledge, the drawdown solution in confined aquifers of finite extent with a skin zone so far has never before been presented in the groundwater literature. This article presents a mathematical model for describing the drawdown distribution due to a constant-flux pumping from a finite-radius well with a skin zone in confined aquifers of finite extent. The analytical solution of the model is developed by applying the methods of Laplace transforms, Bromwich contour integral, and residue theorem. This solution can be used to investigate the effects of finite boundary and conductivity ratio on the drawdown distribution. In addition, the inverse relationship between Laplace- and time-domain variables is used to develop the large time solution which can reduce to the Thiem solution if there is no skin zone.

Kinetic transport in a magnetically confined and flux-constrained fusion plasma

International Nuclear Information System (INIS)

Darmet, G.

2007-11-01

This work deals with the kinetic transport in a fusion plasma magnetically confined and flux-constrained. The author proposes a new interpretation of the dynamics of zonal flows. The model that has been studied is a gyrokinetic model reduced to the transport of trapped ions. The inter-change stability that is generated allows the study of the kinetic transport of trapped ions. This model has a threshold instability and can be simulated over a few tens confining time for either thermal bath constraint or flux constraint. For thermal baths constraint, the simulation shows a metastable state where zonal flows are prevailing while turbulence is non-existent. In the case of a flux-constraint, zonal flows appear and relax by exchanging energy with system's kinetic energy and turbulence energy. The competition between zonal flows and turbulence can be then simulated by a predator-prey model. 2 regimes can be featured out: an improved confining regime where zonal flows dominate transport and a turbulent regime where zonal flows and turbulent transport are of the same magnitude order. We show that flux as well as the Reynolds tensor play an important role in the dynamics of the zonal flows and that the gyrokinetic description is relevant for all plasma regions. (A.C.)

Experimental scaling of fluctuations and confinement with Lundquist number in the RFP

International Nuclear Information System (INIS)

Stoneking, M.R.; Chapman, J.T.; Prager, S.C.; Sarff, J.S.

1997-09-01

The scaling of the magnetic and velocity fluctuations with Lundquist number (S) is examined experimentally over a range of values from 7 x 10 4 to 10 6 in a reversed field pinch (RFP) plasma. Magnetic fluctuations do not scale uniquely with the Lundquist number. At high (relative) density, fluctuations scale as b∝S -0.18 , and fluctuations are almost independent of S at low relative density, b∝S -0.07 ; however both exponents fall in the range of theoretical and numerical predictions. At high relative density, the scaling of the energy confinement time follows expectations for transport in a stochastic magnetic field. A confinement scaling law (nτ E ∝β 4/5 T -7/10 A -3/5 I φ 2 ) is derived assuming the persistent dominance of stochastic magnetic diffusion in the RFP and on the measured scaling of magnetic fluctuations. The peak velocity fluctuations during a sawtooth cycle scale marginally stronger than magnetic fluctuations but weaker than a simple Ohm's law prediction. The sawtooth period is determined by a resistive-Alfvenic hybrid time (T saw ∝√(τ R τ Alf )) rather than a purely resistive time

Confinement improvement with magnetic levitation of a superconducting dipole

International Nuclear Information System (INIS)

Garnier, D.T.; Mauel, M.E.; Boxer, A.C.; Ellsworth, J.L.; Kesner, J.

2009-01-01

We report the first production of high beta plasma confined in a fully levitated laboratory dipole using neutral gas fuelling and electron cyclotron resonance heating. As compared with previous studies in which the internal coil was supported, levitation results in improved confinement that allows higher-density, higher-beta discharges to be maintained at significantly reduced gas fuelling. Contrary to previous supported dipole plasma results which had the stored energy consisting in a hot electron population, a significant plasma stored energy is shown to reside in the bulk plasma. By eliminating supports used in previous studies, cross-field transport becomes the main loss channel for both the hot and the background species. This leads to a significant improvement in bulk plasma confinement and a dramatic peaking of the density profile. Improved particle confinement assures stability of the hot electron component at reduced neutral pressure.

Behavior of FRP-Confined Concrete-Filled Steel Tube Columns

Directory of Open Access Journals (Sweden)

Yiyan Lu

2014-05-01

Full Text Available This paper presents the results of an experimental study into the behavior of concrete-filled steel tube columns confined by fiber-reinforced polymer (FRP. Eleven columns were tested to investigate the effects of the FRP layer number, the thickness of the steel tube and concrete strength on their load capacity and axial deformation capacity. The experimental results indicated that the FRP wrap can effectively confine the concrete expansion and delay the local buckling of the steel tube. Both the load capacity and the axial deformation capacity of concrete-filled steel tube columns can be substantially enhanced with FRP confinement. A model is proposed to predict the load capacity of the FRP-confined concrete-filled steel tube columns. The predicted results are generally in good agreement with the experimental ones obtained in this study and in the literature.

Shape and 'gap' effects on the behavior of variably confined concrete

International Nuclear Information System (INIS)

Harries, Kent A.; Carey, Shawn A.

2003-01-01

Factors affecting the behavior of variably confined concrete are presented. The effect of debonding the fiber-reinforced polymer (FRP) jacket to the concrete substrate and providing a gap between the concrete and confining jacket is investigated. A second parameter--the shape of the cross section--is also investigated. An experimental program involving the compression testing of standard cylinders and similarly sized square specimens having external FRP jackets providing passive confinement is presented. Factors affecting jacket efficiency and the appropriateness of factors accounting for specimen shape are determined experimentally and discussed. The provision of a gap affected the axial stress at which the confining jacket was engaged, resulting in a reduced maximum attainable concrete strength. The jacket efficiency was not affected by the provision of the gap. The shape of the specimens was observed to affect the level of confinement generated. Square specimens exhibit lower confinement levels than circular specimens having the same jacket

Automated entry technologies for confined space work activities: A survey.

Science.gov (United States)

Botti, Lucia; Ferrari, Emilio; Mora, Cristina

2017-04-01

Work in confined spaces poses a significant risk to workers and rescuers involved in the emergency response when an accident occurs. Despite several standards and regulations define the safety requirements for such activities, injuries, and fatalities still occur. Furthermore, the on-site inspections after accidents often reveal that both employers and employees fail to implement safe entry procedures. Removing the risk is possible by avoiding the worker entry, but many activities require the presence of the operator inside the confined space to perform manual tasks. The following study investigates the available technologies for hazardous confined space work activities, e.g., cleaning, inspecting, and maintenance tasks. The aim is to provide a systematic review of the automated solutions for high-risk activities in confined spaces, considering the non-man entry as the most effective confined space safety strategy. Second, this survey aims to provide suggestions for future research addressing the design of new technologies. The survey consists of about 60 papers concerning innovative technologies for confined space work activities. The document review shows that several solutions have been developed and automation can replace the workers for a limited number of hazardous tasks. Several activities still require the manual intervention due to the complex characteristics of confined spaces, e.g., to remove the remains of the automatic cleaning process from the bottom of a tank. The results show that available technologies require more flexibility to adapt to such occupational environments and further research is needed.

Mott glass from localization and confinement

Science.gov (United States)

Chou, Yang-Zhi; Nandkishore, Rahul M.; Radzihovsky, Leo

2018-05-01

We study a system of fermions in one spatial dimension with linearly confining interactions and short-range disorder. We focus on the zero-temperature properties of this system, which we characterize using bosonization and the Gaussian variational method. We compute the static compressibility and ac conductivity, and thereby demonstrate that the system is incompressible, but exhibits gapless optical conductivity. This corresponds to a "Mott glass" state, distinct from an Anderson and a fully gapped Mott insulator, arising due to the interplay of disorder and charge confinement. We argue that this Mott glass phenomenology should persist to nonzero temperatures.

Recent results on confinement in JET

International Nuclear Information System (INIS)

Campbell, D.J.

1992-01-01

The JET device is the world's largest tokamak and has been utilized in plasma heating experiments at total powers of up to 35MW using both neutral beam injection (NBI) and ion cyclotron resonance heating (ICRH). At the highest performance, JET plasmas have achieved conditions equivalent to energy ''breakeven''. A principal aim of the JET experiment is the investigation of plasma heating and confinement in plasma regimes relevant to thermonuclear ignition. The central issues in confinement physics involved in these advances are briefly reviewed and the most recent investigations of transport in high performance plasmas are summarized. (Author)

Laser thermonuclear fusion with force confinement of hot plasma

International Nuclear Information System (INIS)

Korobkin, V.V.; Romanovsky, M.Y.

1994-01-01

The possibility of the utilization of laser radiation for plasma heating up to thermonuclear temperatures with its simultaneous confinement by ponderomotive force is investigated. The plasma is located inside a powerful laser beam with a tubelike section or inside a cavity of duct section, formed by several intersecting beams focused by cylindrical lenses. The impact of various physical processes upon plasma confinement is studied and the criteria of plasma confinement and maintaining of plasma temperature are derived. Plasma and laser beam stability is considered. Estimates of laser radiation energy necessary for thermonuclear fusion are presented

Microinstability-based models for confinement properties and ignition criteria in tokamaks

International Nuclear Information System (INIS)

Tang, W.M.; Bishop, C.M.; Coppi, B.; Kaye, S.M.; Perkins, F.W.; Redi, M.H.; Rewoldt, G.

1987-02-01

This paper reports on results of theoretical studies dealing with: (1) the use of microinstability-based thermal transport models to interpret the anomalous confinement properties observed in key tokamak experiments such as TFTR and (2) the likely consequences of the presence of such instabilities for future ignition devices. Transport code simulations using profile-consistent forms of anomalous thermal diffusivities due to drift-type instabilities have yielded good agreement with the confinement times and temperatures observed in TFTR under a large variety of operating conditions including pellet-fuelling in both ohmic- and neutral-beam-heated discharges. With regard to achieving an optimal ignition margin, the adverse temperature scaling of anomalous losses caused by drift modes leads to the conclusion that it is best to operate at the maximum allowable density while holding the temperature close to the minimum value required for ignition

Submicron confinement effect on electrical activation of B implanted in Si

International Nuclear Information System (INIS)

Bruno, E.; Mirabella, S.; Impellizzeri, G.; Priolo, F.; Giannazzo, F.; Raineri, V.; Napolitani, E.

2005-01-01

In this work we studied the effect of B implantation in Si through submicron laterally confined area on B clustering and its electrical activation. For this study, we implanted B 3 keV into a Si wafer grown by Molecular Beam Epitaxy (MBE) through a patterned oxide mask with opening widths down to 0.38 μm. Then, we annealed the sample at 800 deg. C for several times up to 120 min and monitored the 2D carrier profile by quantitative high resolution Scanning Capacitance Microscopy (SCM). We show that by reducing the opening widths, not only the B clustering is strongly reduced, but also the B cluster dissolution is accelerated. This demonstrates the beneficial role of implanted B confinement on the B electrical activation. The above results have a significant impact in the modern Si based electronic device engineering

The confining string from the soft dilaton theorem

International Nuclear Information System (INIS)

Alvarez, Enrique; Gomez, Cesar

2000-01-01

A candidate for the confining string of gauge theories is constructed via a representation of the ultraviolet divergences of quantum field theory by a closed string dilaton insertion, computed through the soft dilaton theorem. The resulting (critical) confining string is conformally invariant, singles out naturally d=4 dimensions, and can not be used to represent theories with Landau poles

Structural behavior of supercritical fluids under confinement

Science.gov (United States)

Ghosh, Kanka; Krishnamurthy, C. V.

2018-01-01

The existence of the Frenkel line in the supercritical regime of a Lennard-Jones (LJ) fluid shown through molecular dynamics (MD) simulations initially and later corroborated by experiments on argon opens up possibilities of understanding the structure and dynamics of supercritical fluids in general and of the Frenkel line in particular. The location of the Frenkel line, which demarcates two distinct physical states, liquidlike and gaslike within the supercritical regime, has been established through MD simulations of the velocity autocorrelation (VACF) and radial distribution function (RDF). We, in this article, explore the changes in the structural features of supercritical LJ fluid under partial confinement using atomistic walls. The study is carried out across the Frenkel line through a series of MD simulations considering a set of thermodynamics states in the supercritical regime (P =5000 bar, 240 K ≤T ≤1500 K ) of argon well above the critical point. Confinement is partial, with atomistic walls located normal to z and extending to "infinity" along the x and y directions. In the "liquidlike" regime of the supercritical phase, particles are found to be distributed in distinct layers along the z axis with layer spacing less than one atomic diameter and the lateral RDF showing amorphous-like structure for specific spacings (packing frustration) and non-amorphous-like structure for other spacings. Increasing the rigidity of the atomistic walls is found to lead to stronger layering and increased structural order. For confinement with reflective walls, layers are found to form with one atomic diameter spacing and the lateral RDF showing close-packed structure for the smaller confinements. Translational order parameter and excess entropy assessment confirms the ordering taking place for atomistic wall and reflective wall confinements. In the "gaslike" regime of the supercritical phase, particle distribution along the spacing and the lateral RDF exhibit features

Turbulence and energy confinement in TORE SUPRA ohmic discharges

International Nuclear Information System (INIS)

Garbet, X.; Payan, J.; Laviron, C.; Devynck, P.; Saha, S.K.; Capes, H.; Chen, X.P.; Coulon, J.P.; Gil, C.; Harris, G.; Hutter, T.; Pecquet, A.L.

1992-06-01

Results on confinement and turbulence from a set of ohmic discharges in Tore Supra are discussed. The attention is focused on the saturation of the energy confinement time and it is emphasized that this saturation could be explained by a saturation of the electron heat diffusivity. Ion behaviour is indeed governed by dilution and equipartition effects. Although the ion heat transport is never neoclassical, there is no enhanced degradation at the saturation. This behaviour is confirmed by turbulence measurements given by CO 2 laser coherent scattering. The density fluctuations level follows the electron heat diffusivity variations with the average density. Waves propagating in the ion diamagnetic direction are always present in turbulence frequency spectra. Thus, the saturation cannot be explained by the onset of an ion turbulence. The existence of an ion turbulence at the edge at all densities cannot be excluded. However, this ion feature in scattering spectra could be explained by a Doppler shift associated to an inversion point of the radial electric field at the edge

First experimental result of toroidal confinement of non-neutral plasma on Proto-RT

International Nuclear Information System (INIS)

Himura, H.; Yoshida, Z.; Morikawa, J.

1999-01-01

Recently, an internal-ring device named Proto-RT (Prototype Ring Trap) was constructed at University of Tokyo, and experiments on the device have been just initiated. The goal of Proto-RT is to explore an innovative way which has a possibility to attain a plasma equilibrium with extremely high-β (β>1) in a toroidal geometry using non-neutral condition. At the first series of the experiments, pure electron plasma (n e ∼10 12 m -3 ) is successfully confined inside a separatrix. No disruption is so far observed. The confinement time of the electron plasma is the order of 1 sec. A shear effect of magnetic fields seems to result in longer confinement. The non-neutrality of Δn e ∼10 12 m -3 is already beyond the value required to produce an enough self-electric field E in plasma, causing a strong ExB flow thoroughly all over the plasma where the hydrodynamic pressure of the flow is predicted to balance with the thermal pressure of the plasma. (author)

Confinement for More Space

DEFF Research Database (Denmark)

Kipnusu, Wycliffe K.; Elsayed, Mohamed; Kossack, Wilhelm

2015-01-01

Broadband dielectric spectroscopy and positron annihilation lifetime spectroscopy are employed to study the molecular dynamics and effective free volume of 2-ethyl-1-hexanol (2E1H) in the bulk state and when confined in unidirectional nanopores with average diameters of 4, 6, and 8 nm. Enhanced α...

Extended BRS algebra and color confinement criteria

International Nuclear Information System (INIS)

Shintani, Meiun.

1983-09-01

We examine the color-confinement criteria proposed by Kugo and Ojima. With the use of the extended BRS symmetry and the Nakanishi's theorem, we look for the representations of the BRS algebra compatible with the first condition of their criteria (the K-O condition) and then ask whether or not they are physically acceptable. As a result, the quartet mechanism does not work, and the K-O condition is not regarded as a confinement condition. (author)

Status analysis for the confinement monitoring technology of PWR spent nuclear fuel dry storage system

Energy Technology Data Exchange (ETDEWEB)

Baeg, Chang Yeal; Cho, Chun Hyung [Korea Radioactive Waste Agency, Daejeon (Korea, Republic of)

2016-03-15

Leading national R and D project to design a PWR spent nuclear fuel interim dry storage system that has been under development since mid-2009, which consists of a dual purpose metal cask and concrete storage cask. To ensure the safe operation of dry storage systems in foreign countries, major confinement monitoring techniques currently consist of pressure and temperature measurement. In the case of a dual purpose metal cask, a pressure sensor is installed in the interspace of bolted double lid(primary and secondary lid) in order to measure pressure. A concrete storage cask is a canister based system made of double/redundant welded lid to ensure confinement integrity. For this reason, confinement monitoring method is real time temperature measurement by thermocouple placed in the air flow(air intake and exit) of the concrete structure(over pack and module). The use of various monitoring technologies and operating experiences for the interim dry storage system over the last decades in foreign countries were analyzed. On the basis of the analysis above, development of the confinement monitoring technology that can be used optimally in our system will be available in the near future.

Computer simulation of confined liquid crystal dynamics

Energy Technology Data Exchange (ETDEWEB)

Webster, R.E

2001-11-01

Results are presented from a series of simulations undertaken to determine whether dynamic processes observed in device-scale liquid crystal cells confined between aligning substrates can be simulated in a molecular system using parallel molecular dynamics of the Gay-Berne model. In a nematic cell, on removal of an aligning field, initial near-surface director relaxation can induce flow, termed 'backflow' in the liquid. This, in turn, can cause director rotation, termed 'orientational kickback', in the centre of the cell. Simulations are performed of the relaxation in nematic systems confined between substrates with a common alignment on removal of an aligning field. Results show /that relaxation timescales of medium sized systems are accessible. Following this, simulations are performed of relaxation in hybrid aligned nematic systems, where each surface induces a different alignment. Flow patterns associated with director reorientation are observed. The damped oscillatory nature of the relaxation process suggests that the behaviour of these systems is dominated by orientational elastic forces and that the observed director motion and flow do not correspond to the macroscopic processes of backflow and kickback. Chevron structures can occur in confined smectic cells which develop two domains of equal and opposite layer tilt on cooling. Layer lilting is thought to be caused by a need to reconcile a mismatch between bulk and surface smectic layer spacing. Here, simulations are performed of the formation of structures in confined smectic systems where layer tilt is induced by an imposed surface pretilt. Results show that bookshelf, chevron and tilled layer structures are observable in a confined Gay-Berne system. The formation and stability of the chevron structure are shown to be influenced by surface slip. (author)

Monopoles and confinement in lattice gauge theory

International Nuclear Information System (INIS)

Singh, V.

1992-01-01

The mechanism by which quarks, believed to be the fundamental constituents of matter, are prevented from existing in the free state is fundamental problems in physics. One of the most viable candidates for a hypothesis of confinement is the dual superconductor mechanism that likens quark confinement to the Meissner effect in superconductors. The peculiarities of quark interactions make a numerical approach to the subject a necessity, and therefore, much of the work in this area has been done through the methods of lattice gauge theory, with the simplicities afforded by putting spacetime on a four-dimensional grid. Over the years a large amount of indirect evidence has accumulated that the dual superconductor hypothesis does indeed lead to quark confinement but unambiguous evidence has eluded research efforts until recently. This work presents the first direct proof of a Meissner-like effect that leads to confinement, using the numerical techniques of lattice gauge theory. It is shown that for a U(1) lattice gauge theory, that serves as a toy model of the real world of quarks, a dual London relation and an electric fluxoid qauntization condition is satisfied, allowing the author to conclude that the vacuum in this case acts like an extreme type-II superconductor, and that quarks are confined. The author also shows that SU(2) lattice gauge theory, which is qualitatively different and another step closer to reality, shows a Meissner-like effect. In contrast to the U(1) case, the author's results are found consistent with a dual version of the Ginsburg-Landau theory of superconductor on the borderline between type-I and type-II. This approach paves the wave for a study of the more complicated theory, quantum chromodynamics, that is believed to describe quarks

Probabilistic aspects of lattice gauge theories: confinement problem and correlation inequalities

International Nuclear Information System (INIS)

Ruiz, J.

1982-03-01

Definition, formalism and important results are presented. A probabilistic method is developed which enables permanent confinement to be demonstrated in dimension 3 of space time for the gauge models defined on group U(1) or a group such that its centre contains O(1). Correlation inequalities are given for the Ising gauge model defined on the discrete group Z 2 [fr

Structural and mechanical properties of glassy water in nanoscale confinement.

Science.gov (United States)

Lombardo, Thomas G; Giovambattista, Nicolás; Debenedetti, Pablo G

2009-01-01

We investigate the structure and mechanical properties of glassy water confined between silica-based surfaces with continuously tunable hydrophobicity and hydrophilicity by computing and analyzing minimum energy, mechanically stable configurations (inherent structures). The structured silica substrate imposes long-range order on the first layer of water molecules under hydrophobic confinement at high density (p > or = 1.0 g cm(-3)). This proximal layer is also structured in hydrophilic confinement at very low density (p approximately 0.4 g cm(-3)). The ordering of water next to the hydrophobic surface greatly enhances the mechanical strength of thin films (0.8 nm). This leads to a substantial stress anisotropy; the transverse strength of the film exceeds the normal strength by 500 MPa. The large transverse strength results in a minimum in the equation of state of the energy landscape that does not correspond to a mechanical instability, but represents disruption of the ordered layer of water next to the wall. In addition, we find that the mode of mechanical failure is dependent on the type of confinement. Under large lateral strain, water confined by hydrophilic surfaces preferentially forms voids in the middle of the film and fails cohesively. In contrast, water under hydrophobic confinement tends to form voids near the walls and fails by loss of adhesion.

Shearing Nanometer-Thick Confined Hydrocarbon Films: Friction and Adhesion

DEFF Research Database (Denmark)

Sivebæk, I. M.; Persson, B. N. J.

2016-01-01

We present molecular dynamics (MD) friction and adhesion calculations for nanometer-thick confined hydrocarbon films with molecular lengths 20, 100 and 1400 carbon atoms. We study the dependency of the frictional shear stress on the confining pressure and sliding speed. We present results...

Enhanced confinement phenomenology in magnetic fusion plasmas: Is it unique in physics?

International Nuclear Information System (INIS)

Dendy, R.O.

2002-01-01

There is substantial experimental evidence that simple diffusive models for turbulent transport are insufficient to produce all the confinement phenomena observed in tokamaks. This paper reports on the emerging linkage between rapid, nonlocal, nondiffusive transport and overall confinement phenomenology including edge pedestals, enhanced confinement, ELMs, and internal transport barriers. Modern statistical physics techniques are used to construct simple models that generate many of the distinctive elements of global tokamak confinement phenomenology. The similarities are deep and are quantified. These results imply that current observations of avalanching transport in tokamaks may be deeply linked to the fundamental global features of tokamak plasma confinement. (author)

Application of spatially resolved high resolution crystal spectrometry to inertial confinement fusion plasmas.

Science.gov (United States)

Hill, K W; Bitter, M; Delgado-Aparacio, L; Pablant, N A; Beiersdorfer, P; Schneider, M; Widmann, K; Sanchez del Rio, M; Zhang, L

2012-10-01

High resolution (λ∕Δλ ∼ 10 000) 1D imaging x-ray spectroscopy using a spherically bent crystal and a 2D hybrid pixel array detector is used world wide for Doppler measurements of ion-temperature and plasma flow-velocity profiles in magnetic confinement fusion plasmas. Meter sized plasmas are diagnosed with cm spatial resolution and 10 ms time resolution. This concept can also be used as a diagnostic of small sources, such as inertial confinement fusion plasmas and targets on x-ray light source beam lines, with spatial resolution of micrometers, as demonstrated by laboratory experiments using a 250-μm (55)Fe source, and by ray-tracing calculations. Throughput calculations agree with measurements, and predict detector counts in the range 10(-8)-10(-6) times source x-rays, depending on crystal reflectivity and spectrometer geometry. Results of the lab demonstrations, application of the technique to the National Ignition Facility (NIF), and predictions of performance on NIF will be presented.

Matter confinement in light of the Gribov horizon

International Nuclear Information System (INIS)

Palhares, Leticia F.

2016-01-01

The procedure of quantization of Landau-gauge Yang-Mills theories that takes into account the presence of Gribov copies has led to the construction of a scenario of gluon confinement via an infrared effective action, the (refined) Gribov-Zwanziger theory. Here we briefly review and discuss a possible extension of this picture to the matter sector of confining Yang-Mills theories. (paper)

Thermalization in a holographic confining gauge theory

Science.gov (United States)

Ishii, Takaaki; Kiritsis, Elias; Rosen, Christopher

2015-08-01

Time dependent perturbations of states in the holographic dual of a 3+1 dimensional confining theory are considered. The perturbations are induced by varying the coupling to the theory's most relevant operator. The dual gravitational theory belongs to a class of Einstein-dilaton theories which exhibit a mass gap at zero temperature and a first order deconfining phase transition at finite temperature. The perturbation is realized in various thermal bulk solutions by specifying time dependent boundary conditions on the scalar, and we solve the fully backreacted Einstein-dilaton equations of motion subject to these boundary conditions. We compute the characteristic time scale of many thermalization processes, noting that in every case we examine, this time scale is determined by the imaginary part of the lowest lying quasi-normal mode of the final state black brane. We quantify the dependence of this final state on parameters of the quench, and construct a dynamical phase diagram. Further support for a universal scaling regime in the abrupt quench limit is provided.

Thermalization in a holographic confining gauge theory

International Nuclear Information System (INIS)

Ishii, Takaaki; Kiritsis, Elias; Rosen, Christopher

2015-01-01

Time dependent perturbations of states in the holographic dual of a 3+1 dimensional confining theory are considered. The perturbations are induced by varying the coupling to the theory’s most relevant operator. The dual gravitational theory belongs to a class of Einstein-dilaton theories which exhibit a mass gap at zero temperature and a first order deconfining phase transition at finite temperature. The perturbation is realized in various thermal bulk solutions by specifying time dependent boundary conditions on the scalar, and we solve the fully backreacted Einstein-dilaton equations of motion subject to these boundary conditions. We compute the characteristic time scale of many thermalization processes, noting that in every case we examine, this time scale is determined by the imaginary part of the lowest lying quasi-normal mode of the final state black brane. We quantify the dependence of this final state on parameters of the quench, and construct a dynamical phase diagram. Further support for a universal scaling regime in the abrupt quench limit is provided.

Hydrodynamic instabilities in inertial confinement fusion

International Nuclear Information System (INIS)

Freeman, J.R.

1977-01-01

Inertial confinement fusion targets generally consist of hollow high-density spheres filled with low density thermonuclear fuel. Targets driven ablatively by electrons, ions, or lasers are potentially unstable during the initial acceleration phase. Later in time, the relatively low density fuel decelerates the dense inner portion of the sphere (termed the pusher), permitting unstable growth at the fuel-pusher interface. The instabilities are of the Rayleigh-Taylor variety, modified by thermal and viscous diffusion and convection. These problems have been analyzed by many in recent years using both linearized perturbation methods and direct numerical simulation. Examples of two-dimensional simulations of the fuel-pusher instability in electron beam fusion targets will be presented, along with a review of possible stabilization mechanisms

Linking of uniform random polygons in confined spaces

International Nuclear Information System (INIS)

Arsuaga, J; Blackstone, T; Diao, Y; Karadayi, E; Saito, M

2007-01-01

In this paper, we study the topological entanglement of uniform random polygons in a confined space. We derive the formula for the mean squared linking number of such polygons. For a fixed simple closed curve in the confined space, we rigorously show that the linking probability between this curve and a uniform random polygon of n vertices is at least 1-O(1/√n). Our numerical study also indicates that the linking probability between two uniform random polygons (in a confined space), of m and n vertices respectively, is bounded below by 1-O(1/√(mn)). In particular, the linking probability between two uniform random polygons, both of n vertices, is bounded below by 1-O(1/n)

Roles of electric field on toroidal magnetic confinement

International Nuclear Information System (INIS)

Itoh, Kimitaka; Itoh, Sanae; Sanuki, Heiji; Fukuyama, Atsushi.

1992-11-01

Theoretical research on the influence of the electric field on the toroidal magnetic confinement is surveyed. The static electric field is first described. Physics pictures on the generation of the radial electric field and the influence on the confinement are shown. Neoclassical effects as well as the nonclassical processes are discussed. Emphasis is made on the connection with the improved confinement. Convective cell, i.e. the nonuniform potential on the magnetic surface is also discussed. The roles of the fluctuating electric field are then reviewed. The progress in the recent theories on the anomalous transport is addressed. Through these surveys, the impact of the experiments using the heavy ion beam probes on the modern plasma physics is illustrated. (author) 66 refs

A transport model with color confinement

International Nuclear Information System (INIS)

Loh, S.

1997-01-01

First the mostly important properties of QCD are dealt with. It is made plausible, how the QCD vacuum generates a screening of color charges and is by this responsible for the quark confinement in color singlets. in the following the behaviour of classical color charges and color fields is studied and it is concluded that by this approximation, the neglection of quantum-mechanical fluctuation, the quark confinement cannot be explained, because the mean-field approximation leads to a screening of the color charges. Motivated by this result the Friedberg-Lee soliton model is presented, in which the the color confinement and all further nonperturbative QCD effects are phenomenologically modelled by means of a scalar field. Thereafter a derivation of the transport equations for quarks in the framework of the Wigner-function is presented. An extension of the equation to the Friedberg-Lee model is explained. As results the ground-state properties of the model are studied. Mesonic and baryonic ground-state solutions (soliton solutions) of the equations are constructed, whereby the constituents are both light quarks and heavy quarks. Furthermore the color coupling constant of QCD is fixed by means of the string tension by dynamical separation of the quarks of the meson. The flux tubes formed dynamically in this way are applied, in order to study the interaction of two strings and to calculate a string-string potential. Excited states of the meson (isovectorial modes) are presented as well as the influence of the color confinement on the quark motion. Finally the dynamical formation and the break-up of a string by the production of light and heavy quark pairs is described

Predictions of a theory of quark confinement

International Nuclear Information System (INIS)

Mack, G.

1980-03-01

We propose a theory of quark confinement which uses only the simplest of approximations. It explains persistence of quark confinement in Yang Mills theories with gauge group SU(2) or SU(3) as a consequence of asymptotic freedom in perturbation theory and of the known phase structure of Z(2) resp. Z(3) lattice gauge theory. Predictions are derived which can in principle be tested by computer simulation. Some are already tested by results of Creutz. They are in good agreement. (orig.)

Magnetic confinement in plasmas in nuclear devices

International Nuclear Information System (INIS)

Tull, C.G.

1979-01-01

The main emphasis of the magnetic fusion energy research program today lies in the development of two types of confinement schemes: magnetic mirrors and tokamaks. Experimental programs for both of these confinement schemes have shown steady progress toward achieving fusion power breakeven. The scaling of the current machines to a reactor operating regime and newly developed methods for plasma heating will very likely produce power breakeven within the next decade. Predictions are that the efficiency in a fusion power plant should exceed 32%

Predictions of a theory of quark confinement

International Nuclear Information System (INIS)

Mack, G.

1980-01-01

A theory of quark confinement is proposed which uses only the simplest of approximations. It explains persistence of quark confinement in Yang-Mills theories with gauge group SU(2) or SU(3) as a consequence of asymptotic freedom in perturbation theory and of the known phase structure of Z(2) and Z(3) lattice gauge theory. Predictions are derived which can in principle be tested by computer simulation. Some are are already tested by results of Creutz. They are in good agreement

Initial assessment of MHTGR confinement releases

International Nuclear Information System (INIS)

Maneke, J.L.; Lanning, D.D.; Lidsky, L.M.

1986-01-01

Initial investigation of Modular High Temperature Gas-Cooled Reactor (MHTGR) designs suggest that source terms during postulated accidents will be considerably lower than Light Water Reactor (LWR) source term estimates. These lower postulated accident releases are not only a safety incentive, but also an economic incentive for the development of this reactor type. For example, it is hoped that a filtered confinement building, rather than a more expensive LWR-like containment building, would adequately protect the public from radiological releases. The ability of a confinement building to satisfy safety requirements for the MHTGR depends on several reactor parameters, such as fuel quality, reactor design, and the design of the reactor building. SCIMCA, a Simple Code for Initial MHTGR Confinement Assessment has been developed for preliminary MHTGR building requirement calculations. The code is capable of modeling a decay chain with a maximum of five regions. Phenomena such as fission product decay and buildup, natural deposition, building filtration, and intercompartmental transport are incorporated. SCIMCA models reduction mechanisms, such as dispersion and decay, occurring as radioactivity is transported through the environment. A subroutine for calculating doses at specified distances has also been included

Optimized confinement discharges in the stellarator W7-AS

International Nuclear Information System (INIS)

Baldzuhn, J.; Giannone, L.; Kick, M.; McCormick, K. J.

2000-01-01

In addition to the well known H-mode, other types of discharges with enhanced core energy confinement can be observed in the stellarator W7-AS. In this contribution, the properties of some particular examples of those optimized confinement (OC) discharges are presented. These are characterized, besides improved core energy confinement, by strong negative radial electric fields and high ion temperatures in the gradient region, steep density profile gradients and a high penetration depth of neutrals, and small edge electron densities. The role of these plasma parameters for the OC discharges is investigated quantitatively by a numerical model. (author)

Theoretical and numerical analysis of reinforced concrete beams with confinement reinforcement

Directory of Open Access Journals (Sweden)

R. G. Delalibera

Full Text Available This paper discusses the use of confinement in over-reinforced concrete beams. This reinforcement consists of square stirrups, placed in the compression zone of the beam cross-section, in order to improve its ductility. A parametric numerical study is initially performed, using a finite element computational program that considers the material nonlinearities and the confinement effect. To investigate the influence of the transverse reinforcing ratio on the beam ductility, an experimental program was also conducted. Four over-reinforced beams were tested; three beam specimens with additional transverse reinforcement to confine the beams, and one without it. All specimens were fabricated with a concrete designed for a compressive strength of 25 MPa. The experimental results show that the post-peak ductility factor is proportional to the confining reinforcement ratio, however the same is not observed for the pre-peak ductility factor, which varied randomly with changes in the confining reinforcement ratio. It was also observed from the experiments that the confinement effect tends to be smaller close to the beam neutral axis.

Total curvature and total torsion of knotted random polygons in confinement

Science.gov (United States)

Diao, Yuanan; Ernst, Claus; Rawdon, Eric J.; Ziegler, Uta

2018-04-01

Knots in nature are typically confined spatially. The confinement affects the possible configurations, which in turn affects the spectrum of possible knot types as well as the geometry of the configurations within each knot type. The goal of this paper is to determine how confinement, length, and knotting affect the total curvature and total torsion of random polygons. Previously published papers have investigated these effects in the unconstrained case. In particular, we analyze how the total curvature and total torsion are affected by (1) varying the length of polygons within a fixed confinement radius and (2) varying the confinement radius of polygons with a fixed length. We also compare the total curvature and total torsion of groups of knots with similar complexity (measured as crossing number). While some of our results fall in line with what has been observed in the studies of the unconfined random polygons, a few surprising results emerge from our study, showing some properties that are unique due to the effect of knotting in confinement.

Dynamics of an optically confined nanoparticle diffusing normal to a surface.

Science.gov (United States)

Schein, Perry; O'Dell, Dakota; Erickson, David

2016-06-01

Here we measure the hindered diffusion of an optically confined nanoparticle in the direction normal to a surface, and we use this to determine the particle-surface interaction profile in terms of the absolute height. These studies are performed using the evanescent field of an optically excited single-mode silicon nitride waveguide, where the particle is confined in a height-dependent potential energy well generated from the balance of optical gradient and surface forces. Using a high-speed cmos camera, we demonstrate the ability to capture the short time-scale diffusion dominated motion for 800-nm-diam polystyrene particles, with measurement times of only a few seconds per particle. Using established theory, we show how this information can be used to estimate the equilibrium separation of the particle from the surface. As this measurement can be made simultaneously with equilibrium statistical mechanical measurements of the particle-surface interaction energy landscape, we demonstrate the ability to determine these in terms of the absolute rather than relative separation height. This enables the comparison of potential energy landscapes of particle-surface interactions measured under different experimental conditions, enhancing the utility of this technique.

Ohmic H-mode and confinement in TCV

International Nuclear Information System (INIS)

Moret, J.-M.; Anton, M.; Barry, S.

1995-01-01

The unique flexibility of TCV for the creation of a wide variety of plasma shapes has been exploited to address some aspects of tokamak physics for which the shape may play an important role. The electron energy confinement time in limited ohmic L-mode plasmas whose elongation and triangularity have been varied (κ = 1.3 - 1.9, δ 0.1 - 0.7) has been observed to improve with elongation as κ 0.5 but to degrade with triangularity as (1 - 0.8 δ), for fixed safety factor. Ohmic H-modes have been obtained in several diverted and limited configurations, with some of the diverted discharges featuring large ELMs whose effects on the global confinement have been quantified. These effects depend on the configuration: in double null (DN) equilibria, a single ELM expels on average 2%, 6% and 2.5% of the particle, impurity and thermal energy content respectively, whilst in single null (SN) configurations, the corresponding numbers are 3.5%, 7% and 9%, indicative of larger ELM effects. The presence of absence of large ELMs in DN discharges has been actively controlled in a single discharge by alternately forcing one or other of the two X-points to lie on the separatrix, permitting stationary density and impurity content (Z eff ∼ 1.6) in long H-modes (1.5 s). (Author)

Synthesis of Ru nanoparticles confined in magnesium oxide-modified mesoporous alumina and their enhanced catalytic performance during ammonia decomposition

KAUST Repository

Tan, Hua

2012-09-01

In this work, Ru nanoparticles confined in the channels of ordered mesoporous alumina (MA) and magnesium oxide-modified ordered MA are prepared for the first time via a two-solvent technique, combined with the amorphous citrate route. Structural characterizations reveal that uniform 2-3 nm Ru nanoparticles are highly dispersed in the blockage-free channels of mesoporous supports. The Ru nanoparticles confined in MA modified with 20% molar ratio magnesium oxide exhibited a high catalytic activity and stability during ammonia decomposition due to the optimized particle size, basic support, lack of chlorine, and confined space provided by the channels of the mesoporous supports. © 2012 Elsevier B.V. All rights reserved.

Synthesis of Ru nanoparticles confined in magnesium oxide-modified mesoporous alumina and their enhanced catalytic performance during ammonia decomposition

KAUST Repository

Tan, Hua; Li, Kun; Sioud, Salim; Cha, Dong Kyu; Amad, Maan H.; Hedhili, Mohamed N.; Al-Talla, Zeyad

2012-01-01

In this work, Ru nanoparticles confined in the channels of ordered mesoporous alumina (MA) and magnesium oxide-modified ordered MA are prepared for the first time via a two-solvent technique, combined with the amorphous citrate route. Structural characterizations reveal that uniform 2-3 nm Ru nanoparticles are highly dispersed in the blockage-free channels of mesoporous supports. The Ru nanoparticles confined in MA modified with 20% molar ratio magnesium oxide exhibited a high catalytic activity and stability during ammonia decomposition due to the optimized particle size, basic support, lack of chlorine, and confined space provided by the channels of the mesoporous supports. © 2012 Elsevier B.V. All rights reserved.

Effects of Predamaged Level on Confined HSC Columns

Directory of Open Access Journals (Sweden)

Ma Chau-Khun

2017-01-01

Full Text Available In the design of repair works for damaged concrete, an accurate and representative stress-strain model is of important. The stress-strain model for damaged high strength concrete (HSC repaired with post-tensioning steel straps confinement yet available, although the confining method has been proven to be effective in improving the performance of non-damaged HSC. A series of experimental test was carried out to investigate the stress-strain relationships of such concrete. A total of 24 HSC cylinders were compressed until certain damaged levels, then repaired by using steel straps. Two important parameters have been identified to have significant effects on the stress-strain relationship of such repaired concrete, namely the confining volumetric ratio and damaged levels. These parameters were incorporated into the development of stressstrain model, which later was shown to correlate well with the experimental results. This paper also has evidenced that existing stressstrain models of damaged concrete are not suitable to be directly applied to the design of repair works using post-tensioning steel straps confinement that produce external lateral stress on damaged columns before subsequent loading applied.

Hot-electron plasma formation and confinement in the tandem mirror experiment-upgrade

International Nuclear Information System (INIS)

Ress, D.B.

1988-06-01

The tandem mirror experiment-upgrade (TMX-U) at the Lawrence Livermore National Laboratory (LLNL) is the first experiment to investigate the thermal-barrier tandem-mirror concept. One attractive feature of the tandem magnetic mirror as a commercial power reactor is that the fusion reactions occur in an easily accessible center-cell. On the other hand, complicated end-cells are necessary to provide magnetohydrodynamic (MHD) stability and improved particle confinement of the center-cell plasma. In these end-cells, enhanced confinement is achieved with a particular axial potential profile that is formed with electron-cyclotron range-of-frequency heating (ECRF heating, ECRH). By modifying the loss rates of electrons at spatially distinct locations within the end-cells, the ECRH can tailor the plasma potential profile in the desired fashion. Specifically, the thermal-barrier concept requires generation of a population of energetic electrons near the midplane of each end-cell. To be effective, the transverse (to the magnetic field) spatial structure of the hot-electron plasma must be fairly uniform. In this dissertation we characterize the spatial structure of the ECRH-generated plasma, and determine how the structure builds up in time. Furthermore, the plasma should efficiently absorb the ECRF power, and a large fraction of the electrons must be well confined near the end-cell midplane. Therefore, we also examine in detail the ECRH power balance, determining how the ECRF power is absorbed by the plasma, and the processes through which that power is confined and lost. 43 refs., 69 figs., 6 tabs

Confinement of a neutral plasma using nested electric potential wells

International Nuclear Information System (INIS)

Ordonez, C.A.

1997-01-01

A self-consistent, two-dimensional analysis is presented on confining a region of neutral plasma with a Penning/Malmberg type plasma trap using a nested well configuration. It is found that a neutral plasma region having disparate electron and ion temperatures or having high charge state ions can be confined with static fields. For confining a neutral region comprised of electrons and equal temperature low charge state ions, a quasistatic approach appears promising. copyright 1997 American Institute of Physics

Possible retardation effects of quark confinement on the meson spectrum

International Nuclear Information System (INIS)

Qiao, C.; Huang, H.; Chao, K.

1996-01-01

The reduced Bethe-Salpeter equation with scalar confinement and vector gluon exchange is applied to quark-antiquark bound states. The so-called intrinsic flaw of the Salpeter equation with static scalar confinement is investigated. The notorious problem of narrow level spacings is found to be remedied by taking into consideration the retardation effect of scalar confinement. A good fit for the mass spectrum of both heavy and light quarkonium states is then obtained. copyright 1996 The American Physical Society

Confined compressive strength model of rock for drilling optimization

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Xiangchao Shi

2015-03-01