Time-and-space resolved comparison of plasma expansion velocities in high-power diodes with velvet cathodes J. Appl. Phys. 113, 043307 (2013) Development of a diffuse air-argon plasma source using a dielectric-barrier discharge at atmospheric pressure Appl. Phys. Lett. 102, 033503 (2013) Nonmonotonic radial distribution of excited atoms in a positive column of pulsed direct currect discharges in helium Appl. Phys. Lett. 102, 034104 (2013) Iterative Boltzmann plot method for temperature and pressure determination in a xenon high pressure discharge lamp J. Appl. Phys. 113, 043303 (2013) Additional information on Rev. Sci. Instrum. Imaging bolometers utilize an infrared ͑IR͒ video camera to measure the change in temperature of a thin foil exposed to the plasma radiation, thereby avoiding the risks of conventional resistive bolometers related to electric cabling and vacuum feedthroughs in a reactor environment. A prototype of the IR imaging video bolometer ͑IRVB͒ has been installed and operated on the JT-60U tokamak demonstrating its applicability to a reactor environment and its ability to provide two-dimensional measurements of the radiation emissivity in a poloidal cross section. In this paper we review this development and present the first results of an upgraded version of this IRVB on JT-60U. This upgrade utilizes a state-of-the-art IR camera ͑FLIR/Indigo Phoenix-InSb͒ ͑3-5 m, 256ϫ 360 pixels, 345 Hz, 11 mK͒ mounted in a neutron/gamma/magnetic shield behind a 3.6 m IR periscope consisting of CaF 2 optics and an aluminum mirror. The IRVB foil is 7 cmϫ 9 cm ϫ 5 m tantalum. A noise equivalent power density of 300 W / cm 2 is achieved with 40ϫ 24 channels and a time response of 10 ms or 23 W / cm 2 for 16ϫ 12 channels and a time response of 33 ms, which is 30 times better than the previous version of the IRVB on JT-60U.

The infrared imaging video bolometer (IRVB) in JT-60U includes a single graphite-coated gold foil with an effective area of 9×7cm2 and a thickness of 2.5μm. The thermal images of the foil resulting from the plasma radiation are provided by an IR camera. The calibration technique of the IRVB gives confidence in the absolute levels of the measured values of the plasma radiation. The in situ calibration is carried out in order to obtain local foil properties such as the thermal diffusivity κ and the product of the thermal conductivity k and the thickness tf of the foil. These quantities are necessary for solving the two-dimensional heat diffusion equation of the foil which is used in the experiments. These parameters are determined by comparing the measured temperature profiles (for ktf) and their decays (for κ) with the corresponding results of a finite element model using the measured HeNe laser power profile as a known radiation power source. The infrared camera (Indigo/Omega) is calibrated by fitting the temperature rise of a heated plate to the resulting camera data using the Stefan-Boltzmann law.

An overview of the research and development of imaging bolometers giving a perspective on the applicability of this diagnostic to a fusion reactor is presented. Traditionally the total power lost from a high temperature, magnetically confined plasma through radiation and neutral particles has been measured using one dimensional arrays of resistive bolometers. The large number of signal wires associated with these resistive bolometers poses hazards not only at the vacuum interface, but also in the loss of electrical contacts that has been observed in the presence of fusion reactor levels of neutron flux. Imaging bolometers, on the other hand, use the infrared radiation from the absorbing metal foil to transfer the signal through the vacuum interface and out from behind a neutron shield. Recently a prototype imaging bolometer known as the InfraRed imaging Video Bolometer has been deployed on the JT-60U tokamak which demonstrates the ability of this diagnostic to operate in a reactor environment. The application of computed tomography demonstrates the ability of one imaging bolometer with a semi-tangential view to produce images of the plasma emissivity. In addition, new detector foil development promises to strengthen the foil and increase the sensitivity by an order of magnitude.

No abstract

There is increasing interest in extreme-ultraviolet (EUV) laser-based lamps for sub-10-nm lithography operating in the region of 6.6 nm. A collisional-radiative model is developed as a post-processor of a hydrodynamic code to investigate emission from resonance lines in Kr, Gd, and Tb ions under conditions typical for mass-limited EUV sources. The analysis reveals that maximum conversion efficiencies of Kr occur at 5×1010W/cm2, while for Gd and Tb it was ≃0.9%/2πsr for laser intensities of (2−5)×1012W/cm2.