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A 14-channel grating polychromator for the purpose of measuring the electron cyclotron emission (ECE) spectrum has been developed and installed on the large helical device (LHD). The grating polychromator has a Czerny–Turner setup. The main advantage of the grating polychromator is that it has a broad spectral range. Hence, it can be utilized at different magnetic field strengths. Changing the angle or replacing the grating can do this. Gratings with a grid constant of d=2.3, 3, and 5 mm and a blaze angle of 20° can be applied and the scattered spectrum is directed to 14-liquid He cooled InSb detectors. Standard operation is performed with d=3 mm, f[sup range]=148–105 GHz. This is second harmonic ECE for B=2.75 T. Each channel has a spectral resolution of Δf (full width at half maximum)=2.6 GHz or f/Δf=60 at f=150 GHz. The properties of the instrument and first experimental results of LHD ECE will be described in this article. © 2001 American Institute of Physics. [ABSTRACT FROM AUTHOR]

A new method to magnify a small polarization angle with brazed gratings has been developed. In the method, difference in diffraction efficiency for S and P polarization components is used. The magnification dependence on the incident angle can be small by arranging the grating in Littrow layout. A magnification with a factor ~2.7 has been demonstrated for a 10.6 µmCO2 laser beam as expected from a calculation. The method is applicable in many polarimetry fields. [ABSTRACT FROM AUTHOR]