6 research outputs found
Upgrade of Imaging Bolometers on LHD
No full textInfrared Imaging Video Bolometers (IRVB) provide an image of the plasma radiation by using a thin metal foil to absorb the radiation, which is then imaged by an IR camera. In LHD IRVBs at Ports 6-T and 1-O have been upgraded. Both of the ? 1 micron × 70 mm × 90 mm gold foils have been replaced with ? 2.5 micron Pt foils of the same area for greater sensitivity (Pt vs Au) and absorption of higher energy photons estimated up to 8.2 keV. Also the IR cameras have been replaced; an FLIR/SC500 (? 100 mK, 60 fps, 320 × 240 pixels) IR camera at Port 1-O with a FLIR/Phoenix (? 16 mK, 345 fps, 320 × 256 pixels) IR camera at Port 10-O and an AGEMA/THV 900 LW (? 190 mK, 15 fps, 136 × 272 pixels)] with a FLIR SC-4000 (? 19 mK, 327 fps, 320 × 256 pixels) IR camera at port 6-T. In the current campaign these IRVBs will use 8 mm × 8 mm apertures resulting in 12 × 16 channels on the foil. The noise equivalent power density for these two new IRVBs ranges from ? 360 ?W/cm2 for 327 fps operation to 3.6 ?W/cm2 for 15 fps operation, which is over two orders of magnitude of improvement over the previous IRVB at Port 6-T.journal articl
Comparison of Au and Pt Foils for an Imaging Bolometer
No full textIn the imaging bolometer a thin metal foil converts plasma radiated power to infrared radiation measured by an infrared camera. Calibration of the foil provides information on its sensitivity, which is helpful in selecting the best foil material. In this study thermal properties of submicron Au and Pt foils are investigated by heating the foils with a chopped HeNe laser beam (?20 mW) and observing the temperature change, ΔT, and thermal time constant, τ, of the foil temperature. Assuming that the foil cooling is dominated by diffusion, we can compare the relative sensitivities of the foils by comparing the ratio of the thermal diffusivity to the thermal conductivity of the foil, κ/k, to the ratio ΔT/τ. The results indicate that Pt is more than 9 times more sensitive than Au even though standard thermal properties indicate that Au should be slightly (14%) more sensitive than Pt. This inconsistency indicates that the IR radiation is dominant over diffusion in the foil cooling. In that case the sensitivity should be evaluated by 1/k ? ΔT, which indicates that Pt is 8 times more sensitive than Au, while the ratio of thermal conductivities indicates that it should be only 4 times more sensitive.journal articl
