In situ calibration of the foil detector for an infrared imaging video bolometer using a carbon evaporation technique

The InfraRed imaging Video Bolometer (IRVB) is a useful diagnostic for the multi-dimensional measurement of plasma radiation profiles. For the application of IRVB measurement to the neutron environment in fusion plasma devices such as the Large Helical Device (LHD), in situ calibration of the thermal characteristics of the foil detector is required. Laser irradiation tests of sample foils show that the reproducibility and uniformity of the carbon coating for the foil were improved using a vacuum evaporation method. Also, the principle of the in situ calibration system was justified

Improvement of infrared imaging video bolometer for application to deuterium experiment on the large helical device

An infrared imaging video bolometer was improved for application to a neutron environment in fusion plasma devices, i.e., the Large Helical Device (LHD). In order to calibrate the thermal characteristics of the activated foil absorber inside the plasma vacuum vessel, the remote-controlled in situ calibration system was improved with high-surface-flatness mirrors. Furthermore, the carbon coating method was improved by introducing a vacuum evaporation technique instead of the conventional spray technique to realize the coating on both sides of the absorber with reproducibility and uniformity. The optimal thickness of the coating was also determined. Owing to these coating improvements, the reproducibility of the effective emissivity on both sides especially was improved. Finally, the variation with the neutron irradiation of the thermal characteristics of the foil absorber was investigated. It was found that the effect was not significant for the total neutron emission of 3.6 × 1018 on LHD

Microwave-Assisted Regeneration of Synthetic Zeolite Used in Tritium Removal Systems

Microwave irradiation was conducted for the effective regeneration process of a synthetic honeycomb type 5A zeolite adsorbent in a single-mode microwave cavity at 2.46 GHz. To investigate the effect of electromagnetic fields, inductive heating by a magnetic field was applied to synthetic zeolite containing water. Because the microwave energy absorbed in the sample was less than 15 W, the zeolite sample was only heated to a temperature of 71 °C. Water desorption was observed based on the increased temperature of the zeolite sample and the thermogravimetric curve that indicated a single step phenomenon. As a result, the regeneration process of zeolite was not complete over a period of 6000 s. A comparison of dielectric heating by an electric field with inductive heating by a magnetic field showed that the regeneration process by microwave irradiation was particularly beneficial in dielectric heating

MSE Spectroscopy in CHS Heliotron/Torsatron

　　The spectroscopic measurement using the motional Stark effect (MSE) has been recognized to be a useful tool to measure the direction of the magnetic field inside the plasma. The MSE arises from the Lorentz Electric Field, E = v × B, in the atom\u27s rest frame, which is induced when the neutral beam, having the velocity v , crosses the magnetic field B. The spectrum with the motional Stark splitting in the Hα emission consists of 15 components. The spectra which are circularly polarized perpendicular to the Lorentz field are called as σ (0σ, ＋1σ and -1σ lines) components, while the spectra which are linearly polarized parallel to the Lorentz field, namely perpendicular to the magnetic field are called as π (±2π，±3π and ±4π lines) components. Four kinds of spectra with the polarization angle of 0, 45, 90 and 135 degrees are measured to derive the polarization angle of the circularly polarized σ component, and eliminate the overlap between π components and σ components which are perpendicular each other. The diagnostic neutral beam (DNB) is injected almost perpendicularly to the magnetic field line into the Compact Helical System (CHS) heliotron/torsatron device in order to maximize the Lorentz field, namely the Stark shift. The line broadening due to a beam divergence angle results in overlapping between the adjacent lines. Therefore, the smaller beam divergence angle is desirable in DNB for the MSE measurement. The beam divergence angle of DNB is 0.65 degrees, and it gives enough separation between the measured σ and π components in MSE spectroscopy. Although the one-third energy (E/3) component has the smaller motional Stark splitting than the full energy component, the intensity of E/3 component is larger than that of full energy component. Therefore, the one-third energy component is used to derive the pitch angle in CHS.　　The new polarization sensitive spectroscopy, which consists of a polarizer and a ferroelectric liquid crystal (FLC) cell, has been developed to measure the polarization angle with good accuracy. The FLC cell functions as a switchable half-wave retarder, in which polarization angle of the light is rotated by 90 degrees. By using the FLC, the polarization angle can be measured with the error bar of less than ±1 degrees.　　Because the FLC has fast response, the spectra with the polarizer angle of 0 and 90 degrees or -45 and 45 degrees can be measured with the fast modulation of 50 Hz. New CCD detector, where the charse of each pixel is shifted up and down (Dig Dag) synchronized with two sets of FLC modulation, has been developed for MSE measurements. 　　The pitch angle of the magnetic field line is derived from the polarization angle of measured σ and π components of the Hα line with the polarization sensitive spectroscopy. The radial profile of a pitch angle of a local magnetic field is measured for the plasma with the magnetic field of 0.88 T and the magnetic axis of 92.1cm in CHS. The spectra of the σ and π components of the Hα line with the motional Stark effect are measured with the polarization sensitive spectroscopy. The major radius, where the local pitch angle is zero, shifts outboard from that calculated with coil current alone (no plasma) by 28 ± 16 mm. This shift is consistent to that predicted by the effect of finite beta due to bulk plasma and fast ions of heating neutral beam

Hydrogen Solubility of the Molten Salt FLiNaK Mixed with Nano-Ti Powder

The hydrogen-release behavior of the molten salt FLiNaK containing directly synthesized 0.1 wt% nano-Ti powder was investigated. Hydrogen release was faster at higher temperatures, and the volume of released hydrogen from FLiNaK was significantly higher than that from pure FLiNaK. However, the ratio of released H/Ti in FLiNaK was smaller than that in μm-Ti powder

A New Pretreatment Technique for Environmental Tritium Analysis with Microwave Heating Method

The conventional method for FWT and OBT analysis is a liquid scintillation counting method after freeze-drying and combustion of the sample. However, pretreatment for FWT and OBT analysis are complicated and time consuming processes over weeks. Thus, we propose the application of microwave heating technique to save time and effort of the pretreatment of plant samples for FWT analysis. To understand the behavior of the combustion and drying of organic samples, we conducted TG/DTA analysis of pine needle samples. It is found that the sample has to be heated up to 100 - 110 ℃ for complete drying under N2 gas flow condition. Then, we tried the water recovery from fresh pine needle samples by the multi-mode microwave heating system. As a results, it was provided to good recovery yield achieved more than 97% under these experimental conditions. This result shows more preferable for the pretreatment of organic samples by microwave irradiation method than the conventional method