Engineering topics

Kawano, Y.

Publications and source records attributed to Kawano, Y..

5 records

DOE OSTI2019

Thermal analysis of high-pressure hydrogen during the discharging process

The transient temperature and pressure of hydrogen are measured during the hydrogen discharging process through an orifice in a high-pressure vessel. The initial pressures of hydrogen in the vessel are set to approximately 30, 60, and 100 MPa. The mass flow rate and heat flux between hydrogen and the inner wall of the vessel are theoretically estimated using fundamental equations and experimental results with accurate thermophysical properties of hydrogen. The generation of temperature distribution and flow due to heat transfer in the vessel during discharge is verified by numerical analysis. Further, the relationship between reference gas temperature and heat flux in the vessel during the release of high-pressure hydrogen is studied. The average heat flux in the vessel is calculated using experimental and numerical analysis. The appropriate reference temperature is obtained using the comparison of the average heat flux in the vessel. In addition, the dominant heat transfer mode during hydrogen discharge is investigated. Numerical analysis shows that natural convection is formed inside the vessel due to a decrease in temperature. The Nusselt numbers in this process are presented as a function of Rayleigh numbers which are obtained by the experimental results and mass and energy conservations. The relationship between the Nusselt and Rayleigh numbers agrees with the heat transfer correlations of natural convections.

08 HYDROGEN↗

DOE OSTI2019

The ITPA disruption database

A multi-device database of disruption characteristics has been developed under the auspices of the International Tokamak Physics Activity magneto-hydrodynamics topical group. The purpose of this ITPA disruption database (IDDB) is to find the commonalities between the disruption and disruption mitigation characteristics in a wide variety of tokamaks in order to elucidate the physics underlying tokamak disruptions and to extrapolate toward much larger devices, such as ITER and future burning plasma devices. In contrast to previous smaller disruption data collation efforts, the IDDB aims to provide significant context for each shot provided, allowing exploration of a wide array of relationships between pre-disruption and disruption parameters. The IDDB presently includes contributions from nine tokamaks, including both conventional aspect ratio and spherical tokamaks. An initial parametric analysis of the available data is presented. This analysis includes current quench rates, halo current fraction and peaking, and the effectiveness of massive impurity injection. The IDDB is publicly available, with instruction for access provided herein.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗

DOE OSTI2016

Design of tangential viewing phase contrast imaging for turbulence measurements in JT-60SA

A tangential viewing phase contrast imaging system is being designed for the JT-60SA tokamak to investigate microturbulence. In order to obtain localized information on the turbulence, a spatial-filtering technique is applied, based on magnetic shearing. The tangential viewing geometry enhances the radial localization. The probing laser beam is injected tangentially and traverses the entire plasma region including both low and high field sides. The spatial resolution for an Internal Transport Barrier discharge is estimated at 30%–70% of the minor radius at k = 5 cm{sup −1}, which is the typical expected wave number of ion scale turbulence such as ion temperature gradient/trapped electron mode.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗

DOE OSTI2016

Development of real-time rotating waveplate Stokes polarimeter using multi-order retardation for ITER poloidal polarimeter

The rotating waveplate Stokes polarimeter was developed for ITER (International Thermonuclear Experimental Reactor) poloidal polarimeter. The generalized model of the rotating waveplate Stokes polarimeter and the algorithm suitable for real-time field-programmable gate array (FPGA) processing were proposed. Since the generalized model takes into account each component associated with the rotation of the waveplate, the Stokes parameters can be accurately measured even in unideal condition such as non-uniformity of the waveplate retardation. Experiments using a He-Ne laser showed that the maximum error and the precision of the Stokes parameter were 3.5% and 1.2%, respectively. The rotation speed of waveplate was 20 000 rpm and time resolution of measuring the Stokes parameter was 3.3 ms. Software emulation showed that the real-time measurement of the Stokes parameter with time resolution of less than 10 ms is possible by using several FPGA boards. Evaluation of measurement capability using a far-infrared laser which ITER poloidal polarimeter will use concluded that measurement error will be reduced by a factor of nine.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗

DOE OSTI2014

Note: Magnification of a polarization angle with a Littrow layout brazed grating

A new method to magnify a small polarization angle with brazed gratings has been developed. In the method, difference in diffraction efficiency for S and P polarization components is used. The magnification dependence on the incident angle can be small by arranging the grating in Littrow layout. A magnification with a factor ∼2.7 has been demonstrated for a 10.6 μm CO{sub 2} laser beam as expected from a calculation. The method is applicable in many polarimetry fields.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗