Total Stored Energy Research Articles

An X-ray preionised self sustained discharge HF/DF laser

We report the design and characterisation of a flash X-ray preionised, transversely excited HF/DF laser with energy outputs at the joule level. The laser used a H2/D2: SF6 mixture at a pressure of around 120 Torr. X-ray photon fluxes and ionisation rates in the laser gas are presented and the laser dependence on these examined. It is shown that X-ray preionisation can be effective and it is estimated that the laser should operate satisfactorily with as little as 5% of the total stored electrical energy in the preionisation circuit. The laser performance is comparable to that of a UV preionised device with similar operating parameters.

Application of IBW-induced transport barrier in TFTR

Experimental results obtained in PBX-M suggest that IBW can be used to induce locally a transport barrier and improve core confinement. Using similar neoclassical-like particle and ion energy diffusivity values as inferred inside the IBW-induced core barrier, the CH-mode performance is assessed for TFTR high performance D - T plasmas. By controlling the barrier location, Q-factors in the range can be obtained with a total stored energy of MJ.

The ITER project: status and prospects

The International Thermonuclear Experimental Reactor (ITER) is a fusion energy cooperative programme among the European Atomic Energy Community, the Governments of Japan, the Russian Federation and the United States of America. The main objective of the ITER Project is to achieve a controlled ignited burn time of 1000 seconds. The nominal fusion power is to be 1500 MW. During the first 10 years of operation the Basic Performance Phase, the machine should achieve typically a total of a few thousand hours of burn, while during the second phase, the Enhanced Performance Phase, a more extensive burn time is expected for material tests, energy extraction and tritium breeding tests. The machine is a tokamak and has a toroidal geometry. The plasma, with major and minor radii of respectively 8.1 and 2.8 m, will carry a current of 21 MA. The plasma current is induced and controlled by a set of large superconducting coils with a diameter up to 30 m. The confining toroidal magnetic field will be produced by a set of 20 large superconducting magnets with a total magnetic stored energy of 100 GJ and a maximum field at the winding of 12.5 T. The plasma and nuclear engineering features of the project are also described.

Effect of changing capacitors between phases of a biphasic defibrillation shock.

In this study, we examined the effect of changing capacitor values between phases of a biphasic waveform with the goal of lowering leading edge voltage (LEV), total delivered energy (TDE), and total stored energy (TSE). Defibrillation thresholds were determined in 18 open-chest swine using epicardial patch electrodes. In part I, three combinations of capacitors were tested: 150:150 microF; 150:300 microF; and 300:150 microF. Waveform durations were 6/0, 6/2, 6/4, 6/6, and 6/8 ms. In part II, phase 1 capacitance was 150 microF. Three phase 2 capacitance values were used: 150 microF; 75 microF; and 37.5 microF. Phase 2 LEV was a multiple of phase 1 trailing edge voltage: x 0.5; x 0.75; x 1; x 2; x 3; and x 4. A 3.5/2.0 ms biphasic waveform was used. In part III, thresholds were determined for two sets of capacitor values, which can be created by switching a pair of capacitors from in parallel to in series, 150:37.5 microF and 300:75 microF, and nine waveform durations, 4/0, 4/2, 4/4, 6/0, 6/3, 6/6, 8/0, 8/4 and 8/8 ms. In part I, the 300:150 microF system defibrillated with the lowest LEV, TDE and TSE were not different for any of the biphasic waveforms tested except for the 6/8 ms, which was higher. In part II, there was no difference in LEV among any of the three phase 2 capacitor values. LEV was lowest for the x 2, x 3, x 4 multipliers. Peak voltage was lowest for the x 1 and x 2 multipliers. TDE was lowest for the x 0.5, x 0.75, x 1, and x 2 multipliers. In part III, the 300:75 microF system defibrillated at a lower LEV than did the 150:37.5 microF system. The 150:37.5 microF system defibrillated at a lower total delivered energy than did the 300:75 microF. These results suggest that defibrillation can be accomplished with lower LEV, TDE, and TSE if two capacitors are switched from a parallel configuration to a series configuration between phases of the biphasic waveform.

Single phase energy minimizers for materials with nonlocal spatial dependence

We consider a one-dimensional body and assume that the total stored energy functional depends not only on the local strain field but also on the spatial average of the strain field over the body, weighted with an influence kernel. We investigate the problem of minimizing the total stored energy subject to given end displacements. The general existence theory for this problem is reviewed. Then, we narrow our study and concentrate on certain fundamental aspects of nonlocal spatial dependence by restricting our consideration to the case of a convex local energy and an exponential-type influence function for the nonlocal part. We find explicit solutions and show their characteristic properties as a function of the parameter that measures the extent of influence in the nonlocal kernel. We then study in detail the behavior that results when the total stored energy functional loses its coercivity. In this case, issues concerning the local and global stability of extremal fields are considered.

Measurement of the energy of grain boundary geometrically-necessary dislocations in copper

Measurements of the stored energy of cold work and recrystallization temperature of polycrystalline copper of a variety of grain sizes as a function of strain have been performed and it has been shown that: (1) The increase of stored energy with increasing strain falls into three distinct regimes as noted previously. (2) The total stored energy can be divided into two components: the stored energy from statistically-stored dislocations, which increases with increasing strain, and the stored energy from geometrically-necessary dislocation which increases sharply to a strain of {approximately}10%, at which point it saturates. (3) The saturation value of the stored energy from geometrically-necessary dislocations is inversely proportional to the grain size.

The effect of grain size on the stored energy of cold work as a function of strain for polycrystalline nickel

It is well known that both the distribution and density of dislocations are affected by grain boundaries and that the stored energy of deformation is e function of the density of dislocations. Thus, the grain size affects the stored energy of deformation. In general, a fine grain-sized material has a higher dislocation density than a coarse grain-sized material for a given plastic strain. This paper presents measurements of the total stored energy as a function of strain for a series of polycrystalline nickel specimens of different grain size. The aim is to determine how the stored energy of deformation from the geometrically-necessary dislocations contributes to the total stored energy of deformation as a function of the strain.

Direct Energy Conversion Beam Dump for a 1.6-Mev Neutral Beam for the International Thermonuclear Experimental Reactor

A beam direct converter of the Kyoto type, which uses magnetic separation of the D[sup +] and D[sup [minus]] leaving the neutralizer, is adapted to a Lawrence Berkeley Laboratory concept of a neutral-beam injector for the International Thermonuclear Experimental Reactor, which used electrostatic separation of the D[sup +] and D[sup [minus]]. Among the advantages of a direct converter over an ordinary beam dump for the residual D[sup +] and D[sup [minus]] beam leaving the neutralizer is that the power density on the beam dump is reduced by a large factor, making heat removal easier. Further, [open quotes]soft landing[close quotes] virtually eliminates deuterium-deuterium neutron production on the dump electrodes, a particular advantage in the development stage. In addition, the total power consumed is less. This paper addresses the technological obstacle to feasibility, which is holding the large voltage (+1.6 and -1.6 MV for a 1.6-MeV neutral beam). The electrode system in the present design uses 15 grading electrodes around each 1.6 MV collector with 100 kV between them. Each grading electrode is subdivided into two. The total stored energy is 260 J (4 J per electrode) and an average of 10 kV/cm on the insulators. The calculated efficiency is 92%. 13more » refs., 10 figs.« less

Data analysis on TFTR using the SNAP transport code

This paper describes the between shots data analysis on TFTR using the one-dimensional equilibrium kinetic analysis code SNAP. SNAP accepts as input data: the measured plasma size and current, toroidal field, surface voltage, plasma composition (total Zeff and Zeff contribution from metallic impurities), edge neutral density, auxiliary heating power data (neutral beam power, energy, injection geometry and/or rf power and frequency), and measured profiles of Te(R), ne(R), Ti(R), Vφ(R), and Prad(R). SNAP iteratively calculates: (1) the mapping of profile data to a minor radius grid, (2) the magnetic topology including Shafranov shifted circular flux surfaces, (3) neutral beam attenuation and deposition profiles, (4) unthermalized beam ion density and beam power density delivered to thermal plasma species from a numerical solution to the Fokker–Planck equation, (5) the neutral density profile, (6) local heat and particle transport coefficients consistent with the measured profiles and calculated source terms, (7) ICRF power profiles from a reduced order full wave analysis and isotropic Stix quasilinear model, and (8) total neutron emissivity and plasma stored energy. Several ion heat transport models (including neoclassical χi and χi∝χe) are available to calculate an expected Ti(r) profile in the absence of measurements.

Internal kink stabilization by high-energy ions with nonstandard orbits

A generalized energy principle that takes into account the nonstandard, potato-shaped particle orbits of high-energy ions in the central region of a tokamak is derived. It is shown that, in the limit of zero orbit width, this energy principle reduces to the one formulated by Van Dam et al. [Phys. Fluids 25, 1349 (1982)]. The modification of hot particle stabilization theory when such orbit effects are important is investigated. In particular, a model distribution function is chosen to describe high-energy trapped ions produced by ion cyclotron resonant frequency (ICRF) heating applied near the axis of a tokamak. Standard banana orbit theory predicts that, for fixed total stored energy of energetic particles peaked about the magnetic axis, the stabilizing influence on internal kink modes is inversely proportional to the spatial spread of the hot particles. However, this scaling saturates when the spatial spread of the distribution function approaches the width of a typical nonstandard orbit. Hence, ICRF heating is most efficient in producing stabilization when the heating zone is comparable to the orbit width, while the tendency to stabilize does not improve if the heating zone is narrower than the orbit width. Further, it is shown that, if particle orbits can extend close to the q=1 surface, the tendency for stabilization is inhibited.

Fusion yield in high-power D-beam injected He3 plasmas

Fusion yield in He3 plasmas by 10 MW injection of 500 keV deuteron(D)-beam and by up to 30 MW injection of 120 keV D-beam is studied by taking global energy confinement into account. The global energy confinement time, tau E, defined by the ratio of the total stored energy to the input power, is taken to be inversely proportional to the square root of the input power. Higher fusion yield is produced in the regime of lower ne and higher Te, unless the reduction of the He3 density due to the increase of the non-thermal deuteron population is too significant. The hot ion mode of Ti=2Te assumed for high-power 120 keV D-beam injection is found not to be preferable to the Ti=Te mode under the same tau E. The effect of accumulation of thermal deuterons on the fusion yield is also discussed.

Contribution of Superconducting Large Helical Device to Fusion Technology

Large Helical Device (LHD) is a superconducting heliotron type device for advanced fusion experiments. The SC coil system is composed of a pair of helical coils and 3 sets of poloidal coils with a total stored magnetic energy of 1.63 GJ, which will be the world maximum. The main machine parameters, major radius (RC), coil minor radius (aC), magnetic field, plasma minor radius (aP), and plasma volume are 3.9m, 0.975m, 4T, 0.65m, and 30m3, respectively. The material of the super-conductor is NbTi, and the cooling systems are pool-boiling for helical coils and forced-flow for poloidal coils. Since the current density of the helical coils is as high as 53.3A/mm2 with the maximum experienced magnetic field strength of 9.6T, the refrigeration with the super-fluid helium is required. LHD is expected to demonstrate the viability of the helical magnetic configuration extrapolatable to the fusion reactor. The major contributions to fusion technology area are seen in the superconductivity research and development. The necessary R & D programs, detailed design, and construction of parts are now in progress. The construction will be completed in 1997.

Design status of superconducting Large Helical Device

The Large Helical Device (LHD) is a superconducting heliotron/torsatron device. The SC coil system is composed of l=2 helical coils and three sets of poloidal coils with a total stored magnetic energy of 1.63 GJ. The m-number, l-number, major radius, coil minor radius magnetic field, plasma minor radius, and plasma volume are 10, 2, 3.9 m, 0.975 m, 4 T, 0.65 m, and 30 m/sup 3/, respectively. This is an alternative toroidal device which aims at producing plasmas extrapolatable to the reactor regime. The currentless steady operation is the final goal of the LHD program, and there is no danger from the major current disruptions. The material of the superconductor is NbTi, and the cooling systems are pool boiling for helical coils and forced flow for poloidal coils. Since the current density of the helical coils is as high as 53.3 A/mm/sup 2/ with a maximum experienced magnetic field strength of 9.6 T, refrigeration with superfluid helium is required. The LHD has a divertor to control the steady particle recycling and to improve the confinement potential. The vacuum vessel has a dumbbell-shaped poloidal cross section, which makes it possible to install the closed divertor chamber. The necessary R&D programs and detailed design are described.

Steady State H-mode by Ergodic Field on JFT-2M.

H-mode has little controllability from the point of view of a steady state operation. By applying a high-m ergodic magnetic field, the suppression in density and radiation increase is observed with Hα bursts. And a steady state H-mode can be realized in JFT-2M. The total stored energy of the steady state H-mode shows some loss compared with that of the burst free H-mode. But it is only less than about 10% due to the suppression of density increase. The profiles of the core plasma density and temperature are almost the same with and without the ergodic field. The controlled region of the steady state H-mode can be seen as a belt above L/H threshold in neutral beam power versus ergodic field graph. That region increases with increasing the ergodic field. This demonstrates an active controllability of the H-mode.

Energetics of high surface area silicas

The energetics and structure of high surface area, amorphous silicas prepared by low pressure chemical vapor deposition (LPCVD), flame hydrolysis and sol-gel were studied by high temperature transposed temperature drop calorimetry and solution calorimetry. Utilizing appropriate thermodynamic cycles, the total stored energy (measured as ‘fast’ energy release during drop experiments and as ‘slow’ energy release during solution experiments) of impurity free amorphous silicas relative to fused silica glass was determined. The ‘fast’ energy release involves the healing of point defects, reduction of surface area, release of strain, rearrangement of 2- and 3-fold rings by pore collapse or annealing of 2-fold rings (in conjunction with an appropriate concentration of 3- and 4-fold rings). The ‘slow’ energy release differences in the distribution of 3-fold and higher rings in annealed silica relative to fused silica glass. LPCVD film silicas had been deposited at 0.4 Torr pressure by the reaction of SiH 4 and excess O 2 and 523, 643 and 703 K. The total stored energy of 22 to 44 kJ/mol is mainly due to the presence of 2- and 3-fold rings, consistent with Raman and infrared spectra of films and diffraction studies on related ‘snows’. The metastability of the LPCVD films decreases with increasing temperature of deposition due to the increased capacity to anneal metastable siloxane bonds. This trend continues to higher temperatures. An amorphous silica prepared by flame hydrolysis at 1073 K by the combustion of SiCl 4 in O 2 shows little or no stored energy and is energetically almost identical to fused silica glass. Acid- (pH ∼ 1) and base- (pH ∼ 11) catalyzed dry silica gels were prepared by mixing TEOS : ethanol: water in molar proportion 1 : 4 : 4, then aged at 333 K for 24 h and dried at 423 K for 2–3 days. ‘Fast’ energy release accounts for most of the total stored energy of 7.3 kJ/mol for acid-catalyzed and 66.2 kJ/mol for base-catalyzed dry silica gel. It is unlikely that high concentrations of 2- and 3-fold rings percontact with the aqueous medium during the sol-gel process. Therefore, the total stored energy arises predominantly from structural relaxation and rearrangement in the base-catalyzed gel and rearrangement of surface siloxane by pore collapse during volatile loss in the acid-catalyzed gel. The creation of metastable siloxanes from the rapid condensation of monomers (present due to the high solubility of silica in the basic solution) during the drying of the base-catalyzed gel may be the source of its extremely large metastability.

Recent progress in the demo poloidal coil program

The fabrication of two 30-kA NbTi pulsed coils and one 10-kA Nb/sub 3/Sn coil with a total stored energy of 40 MJ is in progress as a part of the DPC (Demonstration Poloidal Coil) Program. All the Nb-Ti superconducting strands have been fabricated, and their loss time-constant has been measured at 0.32 ms at 7 T, which is well below the initial target of less than 1 ms. A novel winding technique is described for the large current conductor which provides good mechanical contact. >

AC losses in the SMES conductor and coil structure

The authors present a methodology for calculating AC losses in the SMES/ETM (Superconducting Magnetic Energy Storage/Engineering Test Model) conductor and coil structure. Coupling and eddy current losses are discussed for a 100-s discharge of a 143-m-diameter ETM with a total stored energy of 21 MWh. The chosen pitch length, filament size, and winding configuration are shown to result in coupling losses that are small during this 400-MW. The total coupling losses are about 0.0048 J/cm/sup 3/. The structural current losses result in energy deposition of about 0.05 J/cm/sup 3/ during the same discharge. The energy is being deposited in the structure (away from the conductor) and over a very long time as far as stability is concerned (100/s). In addition, the highest power deposition occurs toward the end of the discharge, when the conductor current is lowest. The AC losses during slow utility discharge, calculated using the proposed methodology, represent part of the steady-state heat load to be removed by the refrigeration system. >

Analysis of second harmonic ICRF waves in NBI heated JT-60 plasmas

The propagation and absorption of second harmonic ion cyclotron range of frequency (ICRF) waves in NBI heated plasmas are investigated for the regime of plasma parameters in JT-60. The quasi-linear diffusion in the velocity space of ions is taken into account. The Fokker-Planck equation and the kinetic wave equation are numerically solved to obtain the spatial profile of the velocity distribution function and the power deposition profile in a self-consistent manner. The calculation of the power partition rate includes two processes: the direct absorption of the wave through wave-particle interactions and the power transfer due to Coulomb collisions. The power partition between electrons and ions is strongly affected by the plasma density and the RF power. The plasma temperature and the NBI power have some influence on power partition and tail formation in the experimental conditions of interest. The acceleration of the injected particles by ICRF heating is studied. The tail temperature, which is defined by the gradient of the velocity distribution function of tail ions, and the total stored energy of the plasma are calculated and the dependence on the plasma parameters is analysed.

A series wound air core homopolar generator: SWAC for tactical armor applications

The results of a study on generator design for a pulsed electromagnetic (EM) railgun launcher for a 10-shot low-repetition-rate mobile tactical system are presented. A novel design for a series-wound air-core (SWAC) homopolar generator is discussed. A number approaches to the problems associated with multiple-shot operation and high power density are presented. Specifically, designs for a spiral coil group, segmented current collection, active cooling and optimized rotor kinetic energy are addressed. The most significant features of the design are conventional water cooling, low rotational stored energy, and demonstrated materials and fabrication techniques. The resulting power supply consists of two counterrotating SWAC machines with a net energy density of 10 kJ/kg, 60-MJ total stored energy per shot, 2.50 mA peak current at 320 V, and significantly reduced eddy current losses. >

High power ion cyclotron resonance heating in JET

Ion Cyclotron Resonance Heating (ICRH) powers of up to 17 MW have been coupled to JET limiter plasmas. The plasma stored energy has reached 7 MJ with 13 MW of RF in 5 MA discharges with Zeff approximately=2. When Ip/Bphi approximately=1 MA/T the stored energy can be 50 % greater than the Goldston L mode scaling. This is due to transient stabilisation of sawteeth (up to 3 s) and to a significant energy content in the minority particles accelerated by RF (up to 30 % of the total stored energy). Central temperatures of Te approximately 11 keV and Ti approximately=8 keV have been reached with RF alone. (He3)D fusion experiments have given a 60 kW fusion yield (fusion rate of 2*1016 s-1 in the form of energetic fast particles (14.7 MeV(H), 3.6 MeV(He4)) in agreement with modelling. When transposing the same calculation to a (D)T scenario, Q is predicted to be between 0.2 and 0.8 using plasma parameters already achieved. For the first time, a peaked density profile generated by pellet injection could be reheated and sustained by ICRF for 1.2 s. Electron heat transport in the central region is reduced by a factor 2 to 3. The fusion product nio tau ETio reaches 2.2*1020 m-3.s.kev in 3 MA discharges which is a factor of 2.3 times larger than with the normal density profile.