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Wave generation and heating near ion cyclotron frequency in the ST Tokamak

Description: The results of the recent, high power ICRH experiments performed on the ST Tokamak are reported. It was demonstrated that both the fast and slow waves could be generated in toroidal geometry, and heating of the plasma ions at power levels up to 1 MW was observed both at the ion cyclotron frequency ($omega$/sub ci/) and its second harmonic (2$omega$/sub ci/). Measurements by a charge exchange neutral detector directed tangentially to the plasma torus revealed that at 2$omega$/sub ci/ the ion energy within the bulk of the ion distribution function (''parallel body temperature'') could be increased from about 100 eV up to 200 eV with efficiencies ranging from 8 to 45 percent. Efficiency at $omega$/ sub ci/ in raising the parallel temperature was less than at 2$omega$/sub ci/. Charge exchange neutral detection perpendicular to the plasma column showed that both at $omega$/sub ci/ and 2$omega$/sub ci/ the ''perpendicular body temperature'' was enhanced very rapidly by a factor of up to 3. Also, buildup of a high energy ''tail'' in the ion energy distribution was observed. Power transfer to the ions seemed extremely efficient. (auth)
Date: October 1, 1975
Creator: Takahashi, H.
Partner: UNT Libraries Government Documents Department

Effect of multiple step excitation on the reactivation and x-ray intensities following the fusion d. mu. d, d. mu. t and p. mu. t

Description: Menshikov and Ponomarev recently studied analytically the effect of multistep excitation on the muon reactivation for d..mu..t fusion and got a rather large activation factor of 35%. As expected, this shows a large density effect on the reactivation factor. The numerical cascade calculation with the cross section for multistep excitation, used by them, indicates that the reactivation factor is 25%. Due to the large Auger transition rates in the high excited states, the density effect on the reactivation factor is not large. Muonic x-ray spectra of ..mu../sup 3/He from ..mu..-catalyzed pd and dd fissions, measured by H. bossy et al., are analyzed by the cascade model used for the muon reactivation calculation. The model calculation is in good agreement with the intensity ratios ..mu../sup 3/He(3-1)/..mu../sup 3/He(2-1) of 0.13 +- 0.02 and 0.03 +- 0.007 measured for dd and pd fusions, and the multistep excitation increases 5% of the x-ray ratio for dd fusion. 10 refs., 3 figs., 2 tabs.
Date: January 1, 1986
Creator: Takahashi, H.
Partner: UNT Libraries Government Documents Department

ICRF heating and wave generation in the ATC tokamak. Part 1: wave generation, propagation and absorption

Description: Experimental results and their theoretical interpretations of rf heating experiments in the ion cyclotron range of frequencies are presented. The presentation is in two parts, with this part describing the experimental facilities and characteristics of fast compressional Alfven waves in the tokamak, and a subsequent paper which will deal with the pricipal heating results. It is shown that a simple coupling structure which consists essentially of a semi-circular metal strip and a pair of bumper limiters is sufficient to efficiently couple rf power to the plasma. The major part of the coupled power is radiated as the fast wave, and there is no evidence that parasitic loading, if any, accounts for a significant amount of the power. A coupling efficiency (net coupled power/incident power) in excess of 90% is routinely obtained.
Date: April 1, 1979
Creator: Takahashi, H.
Partner: UNT Libraries Government Documents Department

ICRF heating in tokamaks

Description: The current status of ICRF heating of Tokamak plasmas is described. Two aspects of the subject are discussed: the physics of wave damping and the evaluation of ion heating. Recent experiments in several Tokamak devices at the second harmonic of the deuteron cyclotron frequency have exhibited large discrepancies between the observed and predicted wave damping. A possible explanation, based upon enhanced cyclotron harmonic damping due to the proximity of the two-ion hybrid and cyclotron resonance layers, is discussed. The boundary value problem for fast wave propagation in an inhomogeneous two-ion plasma has been solved explicitly to obtain the wave field structure. For modest proton concentrations (less than 5 percent) a steep gradient in the left-hand polarized electric field is found in the region between the hybrid and cyclotron resonant layers. This gradient appears to provide sufficient enhancement of the second harmonic damping strength to account for the observed discrepancies. However, a reliable measurement of the proton concentration is needed to choose between the two possibilities. Ion heating was examined in detail in recent experiments in the ATC device. It is shown that ICRF heating can heat the bulk of the ions in the core of a Tokamak plasma with efficiencies ranging from 10 to 40 percent, without causing any significant change in the ion energy confinement.
Date: October 1, 1977
Creator: Takahashi, H.
Partner: UNT Libraries Government Documents Department

Muon sticking factor in muon catalyzed fusion and the other aspect of this fusion process

Description: The effect of resonance nuclear fusion reaction on the initial muon sticking factor is formulated. The analysis shows that it is very sensitive to the resonance parameter, and the factor calculated, using the molecular wave function obtained by the Diffusion Monte Carlo method, is 0.1 +- 0.01 for the presently evaluated resonance parameter. The analysis of the multistep excitation effect on the reactivation factor shows that the effect is not so large, and the analysis of muonic x-ray spectra of ..mu../sup 3/He from P..mu..d and d..mu..d fusions is in good agreement with the values measured by Bossy et al.
Date: January 1, 1986
Creator: Takahashi, H.
Partner: UNT Libraries Government Documents Department

Laser enhancement of resonance (dt. mu. ,d2e) and (dd. mu. ,d2e) (molecular) formation

Description: The enhancement of resonance molecular formation rates of (dt..mu..,d2e) and (dd..mu..,d2e) by strong laser irradiation have been studied. The formation rates decrease until the laser intensity reaches the order of 10/sup 8/ to 10/sup 9/ W/cm/sup 2/, and they increase substantially for the intensity range of 10/sup 10/ W/cm/sup 2/ to 10/sup 11/ W/cm/sup 2/. The (dt..mu..,d2e) formation rate using the angular frequency laser such as 11.4 x 10/sup 13/ rad/sec becomes 4 x 10/sup 10/ l/sec for the laser intensity of 3 x 10/sup 10/ W/cm/sup 2/. Further increase of laser intensity reduces the formation rate due to the mismatch of the resonance condition. The formation rate is very sensitive to the frequency of the laser and the formation rate of (dd..mu..,d2e) becomes comparable with one of (dt..mu..,d2e) for the cases of w = 22.8 x 10/sup 13/ rad/sec. For the case of dt initial molecule, there is the possibility of enhancing the formation rate by exciting the vibrational motion by laser field.
Date: January 1, 1987
Creator: Takahashi, H.
Partner: UNT Libraries Government Documents Department

Energy production due to the. mu. -catalized DT fusion process in a mixture of deuterium and tritium

Description: This study indicates the possible use of ..mu..-catalized fusion for energy production. Further work needs to be carried out on the effect of target temperature and on reducing the high energy cost for producing ..mu../sup -/ mesons which are required.
Date: January 1, 1981
Creator: Takahashi, H.
Partner: UNT Libraries Government Documents Department

Some thoughts on the muon catalyzed fusion reactor

Description: The design of the muon catalyzed fusion reactor is discussed. Some of the engineering challenges and critical research areas such as ..pi../sup -/ meson transport, beam entry single crystal window and coherent x-ray for stripping the muon from ..cap alpha.. particle, are considered. In order to reduce the tritium inventory and neutron wall loading, use of the laser technique for manipulating the d-t mixture is considered. The heterogeneous d-t mixture using the droplet or jet is discussed. 39 refs., 6 figs.
Date: January 1, 1986
Creator: Takahashi, H.
Partner: UNT Libraries Government Documents Department

Breeding nuclear fuels with accelerators: replacement for breeder reactors

Description: One application of high energy particle accelerators has been, and still is, the production of nuclear fuel for the nuclear energy industry; tantalizing because it would create a whole new industry. This approach to producing fissile from fertile material was first considered in the early 1950's in the context of the nuclear weapons program. A considerable development effort was expended before discovery of uranium ore in New Mexico put an end to the project. Later, US commitment to the Liquid Metal Fast Breeder Reactors (LMFBR) killed any further interest in pursuing accelerator breeder technology. Interest in the application of accelerators to breed nuclear fuels, and possibly burn nuclear wastes, revived in the late 1970's, when the LMFBR came under attack during the Carter administration. This period gave the opportunity to revisit the concept in view of the present state of the technology. This evaluation and the extensive calculational modeling of target designs that have been carried out are promising. In fact, a nuclear fuel cycle of Light Water Reactors and Accelerator Breeders is competitive to that of the LMFBR. At this time, however, the relative abundance of uranium reserves vs electricity demand and projected growth rate render this study purely academic. It will be for the next generation of accelerator builders to demonstate the competitiveness of this technology versus that of other nuclear fuel cycles, such as LMFBR's or Fusion Hybrid systems. 22 references, 1 figure, 5 tables.
Date: January 1, 1984
Creator: Grand, P. & Takahashi, H.
Partner: UNT Libraries Government Documents Department

Medium temperature. mu. -catalyzed fusion and use of laser beam to detect bound. mu. /sup -/ mesons

Description: An investigation of the high-temperature cross section of ..mu..-catalyzed fusion reactions and the feasibility of using laser light to detach bound ..mu../sup -/ meson from fusion product ..cap alpha..-particles are discussed. To effectively produce the ..mu..-catalyzed DT fusion reactions, it is necessary to make the ..mu../sup -/ mesonic molecular state of DT..mu.. by using a resonance reaction of the excited rotational vibrational level.
Date: January 1, 1983
Creator: Takahashi, H. & Moatz, A.
Partner: UNT Libraries Government Documents Department

Analysis of neutron yield produced by high energy proton. [400 and 660 MeV]

Description: Vasil'kov et al.'s experiments for neutron yield and neutron capture distribution produced by 400 and 660 MeV protons were analyzed by using ENDF/B-IV data and the BNL codes NMTC and TWOTRAN. The calculated total neutron radiative capture by /sup 238/U is 77 and 60% of the measured values for protons of 660 and 400 MeV, respectively. The calculated distribution has the higher peak in the central part of the target system, and steeper gradient both in the r and z directions, compared to experimental. The leakage rate of neutrons from the target assembly is calculated as more than 20%, which is much higher than the 10% estimated from the experiment. The total neutron captures determined using ENDF/B-IV are 3.8 and 3.0% higher than those determined using ENDF/B-III for protons of 660 and 400 MeV, respectively. 12 references.
Date: January 1, 1979
Creator: Takahashi, H. & Nakanara, Y.
Partner: UNT Libraries Government Documents Department

Effect of polarized fusion on the neutronics of a mirror fusion reactor

Description: The conclusions of this study are that for the anisotropic neutron source: (1) the radiation damage in the first wall is reduced, and (2) both the fraction of energy (heat) deposited in the hot interior, and the tritium breeding ratio do not change significantly. These conclusions apply to this particular blanket design only. In order to increase the fractional heating and the breeding ratio, the blanket design must be modified.
Date: January 1, 1983
Creator: Takahashi, H. & Lazareth, O.W.
Partner: UNT Libraries Government Documents Department

Very high flux research reactors based on particle fuels

Description: A new approach to high flux research reactors is described, the VHFR (Very High Flux Reactor). The VHFR fuel region(s) are packed beds of HTGR-type fuel particles through which coolant (e.g., D/sub 2/O) flows directly. The small particle diameter (typically on the order of 500 microns) results in very large surface areas for heat transfer (approx. 100 cm/sup 2//cm/sup 3/ of bed), high power densities (approx. 10 megawatts per liter), and minimal ..delta..T between fuel and coolant (approx. 10 K) VHFR designs are presented which achieve steady-state fluxes of approx. 2x10/sup 16/ n/cm/sup 2/sec. Deuterium/beryllium combinations give the highest flux levels. Critical mass is low, approx. 2 kg /sup 235/U for 20% enriched fuel. Refueling can be carried out continuously on-line, or in a batch process with a short daily shutdown. Fission product inventory is very low, approx. 100 to 300 grams, depending on design.
Date: January 1, 1985
Creator: Powell, J.R. & Takahashi, H.
Partner: UNT Libraries Government Documents Department

Fractal characterization of subsurface fracture network for geothermal energy extraction system

Description: As a new modeling procedure of geothermal energy extraction systems, the authors present two dimensional and three dimensional modeling techniques of subsurface fracture network, based on fractal geometry. Fluid flow in fractured rock occurs primarily through a connected network of discrete fractures. The fracture network approach, therefore, seeks to model fluid flow and heat transfer through such rocks directly. Recent geophysical investigations have revealed that subsurface fracture networks can be described by "fractal geometry". In this paper, a modeling procedure of subsurface fracture network is proposed based on fractal geometry. Models of fracture networks are generated by distributing fractures randomly, following the fractal relation between fracture length r and the number of fractures N expressed with fractal dimension D as N =C&middot;r<sup>-D</sup>, where C is a constant to signify the fracture density of the rock mass. This procedure makes it possible to characterize geothermal reservoirs by the parameters measured from field data, such as core sampling. In this characterization, the fractal dimension D and the fracture density parameter C of a geothermal reservoir are used as parameters to model the subsurface fracture network. Using this model, the transmissivities between boreholes are also obtained as a function of the fracture density parameter C, and a parameter study of system performances, such as heat extraction, is performed. The results show the dependence of thermal recovery of geothermal reservoir on fracture density parameter C.
Date: January 28, 1993
Creator: Watanabe & Takahashi, H.
Partner: UNT Libraries Government Documents Department

Accelerator breeder with uranium, thorium target

Description: An accelerator breeder, that uses a low-enriched fuel as the target material, can produce substantial amounts of fissile material and electric power. A study of H/sub 2/O- and D/sub 2/O-cooled, UO/sub 2/, U, (depleted U), or thorium indicates that U-metal fuel produces a good fissile production rate and electrical power of about 60% higher than UO/sub 2/ fuel. Thorium fuel has the same order of magnitude as UO/sub 2/ fuel for fissile-fuel production, but the generating electric power is substantially lower than in a UO/sub 2/ reactor. Enriched UO/sub 2/ fuel increases the generating electric power but not the fissile-material production rate. The Na-cooled breeder target has many advantages over the H/sub 2/O-cooled breeder target.
Date: January 1, 1983
Creator: Takahashi, H.; Powell, J. & Kouts, H.
Partner: UNT Libraries Government Documents Department

Neutron-transport equation in a general curvelinear coordinate system

Description: Different from a fission reactor, a fusion reactor has complex geometry, such as toroidal geometry. Neutron transport equation for the toroidal coordinate system has been derived by using coordinate transformation from the cartesian coordinate. These methods require rather tedious calculations. Presented here is a simple method to formulate the neutron transport equation in the general curvelinear coordinate system. The equations for parabolic cylinder and toroidal coordinate systems are derived as an example.
Date: January 1, 1981
Creator: Takahashi, H
Partner: UNT Libraries Government Documents Department

Multiphoton processes in the field of two-frequency circularly polarized plane electromagnetic waves

Description: The authors solve Dirac`s equation for an electron in the field of a two-frequency plane electromagnetic wave, deriving general formulae for the probabilities of radiation of a photon by the electron, and for the probabilities for pair production by a photon when the two-frequency wave is circularly polarized. In contrast to the case of a monochromatic-plane electromagnetic wave, when an electron is in the field of a two-frequency circularly polarized wave, besides the absorption of multiphotons and emission of simple harmonics of the individual waves, stimulated multiphoton emission processes and various composite harmonic-photon emission processes are occurred: when a high-energy photon is in a such a field, multiphoton processes also follow the pair production processes.
Date: July 1, 1997
Creator: Yu, An & Takahashi, H.
Partner: UNT Libraries Government Documents Department

Experimental determination of the vertical instability strength in PDX tokamak

Description: The instability strength of a diverted plasma with vertical elongation is measured for a range of the magnetic field decay index, -1.5 < n < +0.5, in the standard-D and inverted-D configurations. The range of the instability growth time is from one to four orders of magnitude greater than previously published results. When the plasma current is in the range, 170 to 310 ka, the instability can be suppressed by passive stabilization due to currents induced in a discrete coil system together with a moderate power (100 kw) active feedback system. The inverted-D configuration is three times more unstable than the standard-D configuration for the same ellipticity. The inverted-D configuration is destabilized by its negative triangularity and the standard-D is stabilized by its positive triangularity.
Date: July 1, 1982
Creator: Takahashi, H.; Bol, K.; Maeda, H.; Okabayashi, M. & Reusch, M.
Partner: UNT Libraries Government Documents Department

Linear Accelerator Reactors (LARs) year end report, FY 1977--September 30, 1977

Description: Under the Nuclear Alternative Systems Assessment Program (NASAP), Brookhaven National Laboratory has initiated a study of Linear Accelerator Assisted Reactors to assess their potential and feasibility in a nuclear energy scenario which will minimize the risk of weapons proliferation. This report covers the period from the inception of the project to the end of FY 1977 (July--September 1977).
Date: January 1, 1977
Creator: Powell, J R; Steinberg, M & Takahashi, H
Partner: UNT Libraries Government Documents Department