Abstract
The sensitivity of an infrared imaging video bolometer (IRVB) was improved for the measurement of relatively low energy plasma radiation from the viewpoint of the metal foil absorber material. The photon energy of the radiation was considered up to 1 keV for the divertor plasma measurement. The thickness of the foil absorber was evaluated not only for conventional heavy elements, e.g., platinum, but also for light elements by the relation between the photon energy and attenuation length and by mechanical strength. A heat-transfer calculation using ANSYS suggested that light elements with practical foil thickness provide a higher temperature rise of the foil absorber compared with heavier elements with practical foil thickness. The maximum of the temperature rise was evaluated using He-Ne laser irradiation onto absorber samples. The material dependence of the temperature rise has a similar tendency between calculations and experiments. Experimentally, the sensitivity of the IRVB improved from 280 to 110 µW/cm2 using titanium with 1 µm thickness compared with conventional platinum with 2.5 µm thickness. Consequently, the signal-to-noise ratio of the IRVB could be improved from 2.8 to 9.1.
Highlights
In fusion reactors, radiative cooling using impurity seeding is a common scenario to reduce divertor heat load.In ITER, 50-60% of the heating power should be dispersed as plasma radiation
In this paper, sensitivity of the IRVB was improved by focusing on the divertor plasma measurement
Sensitivity of the IRVB was improved for measurement of relatively low energy plasma radiation from the viewpoint of a metal foil absorber material
Summary
Radiative cooling using impurity seeding is a common scenario to reduce divertor heat load. Resistive bolometers are commonly used for plasma radiation measurement mainly in large devices [4]. It is too costly, especially for radiation profile measurement with a number of channels. The material of the absorber has not been investigated for the plasma radiation with low energy only from divertor plasmas. In this paper, sensitivity of the IRVB was improved by focusing on the divertor plasma measurement. By considering the IRVB has been installed at the upstream region of the E-divertor region, plasma radiation with the photon energy up to 1 keV is considered.
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