Homaira Parchamy

Development of imaging bolometers for magnetic fusion reactors (invited).

Imaging bolometers utilize an infrared (IR) 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 (IRVB) 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-InSb) (3-5 microm, 256 x 360 pixels, 345 Hz, 11 mK) 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 cm x 9 cm x 5 microm tantalum. A noise equivalent power density of 300 microW/cm(2) is achieved with 40 x 24 channels and a time response of 10 ms or 23 microW/cm(2) for 16 x 12 channels and a time response of 33 ms, which is 30 times better than the previous version of the IRVB on JT-60U.

Detailed in situ laser calibration of the infrared imaging video bolometer for the JT-60U tokamak

The infrared imaging video bolometer (IRVB) in JT-60U includes a single graphite-coated gold foil with an effective area of 9 × 7 cm 2 and a thickness of 2.5 μ m . 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 t f 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 k t f ) 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...

Laser-plasma source parameters for Kr, Gd, and Tb ions at 6.6 nm

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.

Spectral irradiance of singly and doubly ionized zinc in low-intensity laser-plasma ultraviolet light sources

The absolute spectral irradiances of laser-plasmas produced from planar zinc targets are determined over a wavelength region of 150 to 250 nm. Strong spectral radiation is generated using 60 ns full-width-at-half-maximum, 1.0 μm wavelength laser pulses with incident laser intensities as low as ∼5 × 108 W cm−2. A typical radiation conversion efficiency of ∼2%/2πsr is measured. Numerical calculations using a comprehensive radiation-hydrodynamics model reveal the strong experimental spectra to originate mainly from 3d94s4p-3d94s2, 3d94s4d-3d94s4p, and 3d94p-3d94s, 3d94d-3d94p unresolved-transition arrays in singly and doubly ionized zinc, respectively.

Ultraviolet out-of-band radiation studies in laser tin plasma sources

Out-of-band long wavelength emission measurements from high power, high-repetition-rate extreme-ultra-violet lithography (EUVL) laser plasma sources are imperative to estimating heat deposition in EUV mirrors, and the impact of short wavelength light transported through the imaging system to the wafer surface. This paper reports a series of experiments conducted to measure the absolute spectral irradiances of laser-plasmas produced from planar tin targets over the wavelength region of 124 to 164 nm by 1.06 μm wavelength, 10 ns full-width-at-half-maximum Gaussian laser pulses. The use of spherical targets is relevant to the EUVL source scenario. Although plasmas produced from planar surfaces evolve differently, there is a close similarity to the evolution of current from 10.6 μm CO2 laser EUVL sources, which use a pre-pulse from a lower energy solid-state laser to melt and reform an initial spherical droplet into a thin planar disc target. The maximum of radiation conversion efficiency in the 124–164 nm wa...

Comparison of the Au and Ta Foil Parameters from laser Calibration of Imaging Bolometer Foils

The calibration technique of the imaging bolometer foil gives confidence in the measured values of the plasma radiation power. In this paper we improve the accuracy of the calibration of the imaging bolometer foil by using an IR camera (FLIR/SC500) (60 Hz, 320 x 240 pixels, 7.5-13 mum) in a calibration laboratory (low noise environment) with a close-up lens, which provides a spatial resolution of ~0.09 mm which is ~7 times better than the previous in situ calibration using a different IR camera (Indigo/Omega) (30 Hz, 160 x 120 pixels, 7.5-13.5 mum). In addition the foil material is changed for the development of the imaging bolometer. Tantalum (Ta) is offered for improved sensitivity, foil strength, and lower neutron cross-section compared to the previously used gold foil of the imaging bolometer for the JT-60U tokamak. In this paper we report the local foil properties (the thermal conductivity (constant), and the thickness) of a single graphite-coated gold foil (a nominal thickness of 2.5 mum) for LHD compared with those of a single graphite-coated tantalum foil (a nominal thickness of 5 mum) for JT-60U by calibration with a He-Ne laser.

Experimental and numerical investigation of laser-based short wavelength plasma sources

Laser-based plasma lamps are of particular interest in the semiconductor industry. This study examines the optimum regions of laser-plasma operational space for a number of intense laser-irradiated mass-limited droplet source scenarios.

Laser-based plasma sources at 6.6 and 60 nm

Potential high power laser-based xenon and terbium plasma sources are identified based on the reflectivity profiles of the available LaN/B4C, LaN/B, and Al/Yb/Sio multilayer mirrors for applications such as surface processing and semiconductor industry.

Design of an imaging bolometer upgrade for JT-60U

In this paper we present the design of an upgraded version of the imaging bolometer on JT-60U. The 2.5 micron gold foil is replaced with a 5 micron Ta foil for improved rigidity. The vacuum window will be enlarged from 58 mm (ZnSe) to 100 mm (sapphire). The enlarged window and a 3.8 m IR periscope using CaF2 optics and an aluminum mirror will improve the optical throughput. The periscope will permit a more advanced IR camera (FLIR/Indigo Phoenix-mid) (3-5 microns, 256 times 360 pixels, 345 Hz, 25 mK) to be mounted at a location of lower neutron flux and lower magnetic field in a shield box consisting of 2 cm of soft iron (against magnetic field), 2 cm of lead (against secondary gammas), and 10 cm of polyethylene (against neutrons). Through the combination of improved optical throughput using the periscope and the improved sensitivity of the IR camera we expect an improvement in the sensitivity of the imaging bolometer by at least a factor of 50 compared to the previous version. This improvement in sensitivity is used to increase the number of channels from 12 (toroidal) times 16 (poloidal) to 24 times 40 by reducing the aperture size from 5 mm times 5 mm to 2 mm times 2.5 mm, respectively. This imaging bolometer represents a reactor relevant prototype for those planned for KSTAR, LHD, JT-60SA and proposed for ITER.

Radiation from Tightly Focused Highly Intense Laser Pulse Interaction with Weakly Magnetized Plasma

From a tightly focused highly intense ultrashort laser pulse interaction with a weakly magnetized plasma, radiations in the microwave frequency range have been observed. To investigate the microwave radiation produced by the laser-plasma interaction, a mode-locked Ti:Sapphire laser beam with a wavelength of 800 nm, a pulse width of 100 fs [full width at half maximum (FWHM)], a maximum energy of 100 mJ per pulse, and a repetition rate of 10 Hz has been employed. Radiation emission characteristics could be explained by the electron motion along the applied magnetic field, where electrons are affected by the electric field created by an ion column. Calculated data of the electron motion are in good agreement with experimental data.