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Up-Grade Bypass Controlled Supercritical CO2 Gas Turbine for 0.6 GWth FFHR Series Fusion Reactors
Get PDFFor the purpose of further improving the power generation performance by the supercritical CO2 gas turbine power generation system, aerodynamic optimum and heat transfer flow analysis were carried out for vertical single-axial bypass control type supercritical CO2 gas turbine power generation system model in the 0.6 GW class FFHR-b1 nuclear fusion power reactor model. As a result, the following conclusions were obtained.
(1) Since the outlet temperature of the 5-stage final stage of the improved main compressor as an alternative to the low/high pressure compressor can be lowered to 318 K compared to the conventional design (outlet temperature 334 K), there are design cases that do not require an intercooler in the conventional design.
(2) As a result of reviewing the structural design and operating conditions of the turbine, the output increased by about 1.1%.
(3) Since a compact design with a total length of about 2.2 m is possible in the design of the above CO2 gas turbine power generation system (excluding the generator), the feasibility of designing a vertical single-axial bypass control type supercritical CO2 gas turbine power generation system is clarified.
From these results, the redesigned vertical uniaxial bypass control type supercritical CO2 gas turbine power generation system is expected to be a compact and economical power generation system that exceeds the power generation efficiency of the conventional design model up to about 0.6%.journal articl
Prediction of Neutron Emission Rate in Deuterium Neutral Beam Heated CFQS Plasmas Using FIT3D-DD Code
Get PDF0000-0002-5364-805XFIT3D-DD code, which is a neutron emission and heating efficiency evaluation code based on a simple analytical solution of the Fokker-Planck equation, was applied to deuterium Chinese first quasi-axisymmetric stellarator (CFQS) plasmas heated by a deuterium neutral beam injector. A database of the neutron emission rate due to the beam-bulk D-D fusion reaction in the CFQS was created with the electron temperature and density, which were evaluated from the energy confinement time using ISS04 scaling. The neutron emission rate increases monotonically with the increase in the electron temperature and density. The neutron emission rate is expected to be up to ∼2.7 × 1012 [n/s] for an electron density of less than 4 × 1019 m−3.journal articl
Estimation of a Plasma Mirror Reflectivity of LFEX Laser and Relevant Results Using Electron Energy Spectrometers
Get PDFIn the counter-irradiation, which is one of the fast ignition schemes, higher core energy coupling can be expected when there are two hot electron flows in counter directions. Two plasma mirrors were installed for the counter irradiation at about 180 degrees. The hot electron effective temperatures (Teff) were measured by using electron energy spectrometers. Teff vs the laser intensity on a foil target followed Wilkes' scaling law. The energy incident on the target could be calculated by estimating the laser intensity on the target from Teff and estimating the focusing radius from the X-ray pinhole camera image. As a result, the reflectivity could be estimated to be 17 ± 3%.journal articl
Nambu mechanics viewed as a Clebsch parameterized Poisson algebra: Toward canonicalization and quantization
Get PDF0000-0002-9165-6616In his pioneering paper [Phys. Rev. E 7, 2405 (1973)], Nambu proposed the idea of multiple Hamiltonian systems. The explicit example examined there is equivalent to the so(3) Lie–Poisson system, which represents noncanonical Hamiltonian dynamics with a Casimir; the Casimir corresponds to the second Hamiltonian of Nambu’s formulation. The vortex dynamics of an ideal fluid, while it is infinite dimensional, has a similar structure, in which the Casimir is the helicity. These noncanonical Poisson algebras are derived by the reduction, i.e., restricting the phase space to some submanifold embedded in the canonical phase space. We may reverse the reduction to canonicalize some Nambu dynamics, i.e., view the Nambu dynamics as the subalgebra of a larger canonical Poisson algebra. Then, we can invoke the standard corresponding principle for quantizing the canonicalized system. The inverse of the reduction, i.e., representing the noncanonical variables by some canonical variables may be called “Clebsch parameterization” following the fluid mechanical example.journal articl
Design, Fabrication and Soundness Test of A Bi2223 Magnet Designed for Cooling by Liquid Hydrogen
Get PDF0000-0003-1454-8117The critical heat flux in liquid hydrogen is ten times higher than that in liquid helium and is approximately half of that in liquid nitrogen. Since the resistivity of pure metal such as copper or silver at 20 K is less than one-hundredth of that at 300 K, HTS magnets immersed in liquid hydrogen are expected to satisfy the fully cyostable condition or to be stable against high resistive heat generation enough for quench detection at a practical current density. In order to examine cryostability of HTS magnets in liquid hydrogen, a pool-cooled Bi2223 magnet with a 5 T magnetic field at 20 K has been designed, fabricated and tested in liquid nitrogen prior to excitation tests in liquid hydrogen. The magnet consists of six outer double pancake coils with the inner diameter of 0.20 m and four inner double pancake coils with the outer diameter of 0.16 m. The resistive voltage to initiate thermal runaway in the coil assembly in liquid nitrogen was higher than 1 V that is sufficient high for quench detection.journal articl
Electron temperature and density measurement by Thomson scattering with a high repetition rate laser of 20 kHz on LHD
Get PDF0000-0003-2217-6018Thomson scattering measurements with a high-repetition-rate laser have commenced in the Large Helical Device. As an example of the fast phenomena captured by this diagnostic system, measurements at a 20 kHz repetition-rate in hydrogen pellet-injected plasmas are presented. Signal processing methods for this measurement have been developed and electron temperature profiles with almost 70 spatial points were evaluated at time intervals of 50 μs. After Raman scattering calibration, electron density profiles were derived. Fast changes in the electron temperature and density profiles within 1 ms were observed.journal articl
Particle control in long-pulse discharge using divertor pumping in LHD
Get PDF0000-0001-5522-3082Density control is crucial for maintaining stable confined plasma. Divertor pumping, where neutral particles are compressed and exhausted in the divertor region, was developed for this task for the Large Helical Device. In this study, neutral particle pressure, which is related to recycling, was systematically scanned in the magnetic configuration by changing the magnetic axis position. High neutral particle pressure and compression were obtained in the divertor for a high plasma electron density and the inner magnetic axis configuration. Density control using divertor pumping with gas puffing was applied to electron cyclotron heated plasma in the inner magnetic axis configuration, which provides high neutral particle compression and exhaust in the divertor. Stable plasma density and electron temperature were maintained with divertor pumping. A heat analysis shows that divertor pumping did not affect edge electron heat conductivity, but it led to low electron heat conductivity in the core caused by electron-internal-transport-barrier-like formation.journal articl
Real-time wall conditioning and recycling modification utilizing boron and boron nitride powder injections into the Large Helical Device
Get PDF0000-0003-3588-6801Controlled particulate injections from the PPPL impurity powder dropper (IPD) into the Large Helical Device have demonstrated positive effects on the wall conditions on both an intra and inter-shot basis. Injections over a range of densities, input powers, pulse lengths, heating schemes, injection quantities and main ion species show conclusive evidence of improvement to plasma wall conditions. Successful injections are confirmed by both spectroscopic measurements as well as real-time visible camera signals. In 7 s long plasmas the responses include a reduction in wall recycling as well as a reduction in native impurity content as observed over the course of several discharges. For plasmas longer than 40 s, improvements to the recycling rate and increased impurity control are observed in real time as a consequence of the extended particulate injections. These experiments demonstrate the extended applicability of this solid particulate conditioning technique to the control and maintenance of the plasma wall conditions. In addition they are an important initial step in the development of the real-time boronization technique as a supplement to standard conditioning scenarios.journal articl
Direct observation of mass-dependent collisionless energy transfer via Landau and transit-time damping
Get PDF0000-0002-0585-4561The energy transfer from wave to particle occurs in collisionless plasma through the interaction between particle and wave, associated with the deformation of ion velocity space from Maxwell-Boltzmann distribution. Here we show the direct observation of mass-dependent collisionless energy transfer via Landau and transit-time damping in a laboratory plasma. The Landau and transit-time damping are confirmed by the bipolar velocity-space signature of the ion velocity distribution function, measured by fast charge exchange spectroscopy with a time resolution less than ion-ion collision time. The excellent agreement between the resonant phase velocity evaluated from the bipolar velocity-space signature and the wave’s phase velocity, estimated from the frequency of the magnetohydrodynamics oscillation measured with the plasma displacement is clear evidence for the Landau damping. The energy transfer from solitary wave to fully ionized carbon impurity ions is larger than that of bulk ions 2-3 times due to heavier mass.journal articl
Structural Correlation of Random Lasing Performance in Plasma-Induced Surface-Modified Gallium Nitride
No full text0000-0002-7666-9742The surface of GaN has been modified by a simple method that irradiates the substrate with Ar plasma and impurity codeposition, which is termed CoDE (Co-Deposition Etching). Unique structures were formed by the assistance of a small amount of Mo deposition without degradation of the crystal structure. The size of protrusions on the structure is influenced by the amount of deposited Mo particles. The mechanism for the structure formation is discussed based on transmission electron microscopy (TEM) observations and energy dispersive X-ray spectroscopy (EDS) measurements. Based on the GaN surface roughness, we have demonstrated random laser action in the UV region under photoexcitation. The lowest threshold (0.06 J/cm2) for random lasing was observed where the size of the structure is larger than 0.05 μm2, which was formed under conditions with the least amount of deposition. The correlation between the submicro/nanosize structures generated by plasma irradiation and lasing was evaluated in detail. The critical parameter to optimize the random lasing was determined to be the size of structures that can be modified by the Mo deposition rate. The results confirmed that the emission properties can be controlled by the processing conditions. This random laser fabrication technique is expected to be widely applicable to various direct-bandgap compound semiconductors.journal articl