High-throughput Accurate-wavelength Lens-based Visible Spectrometer
Authors: Ronald E. Belll and Filippo Scotti
Abstract:
A scanning visible spectrometer has been prototyped to complement fixed-wavelength transmission grating
spectrometers for charge exchange recombination spectroscopy. Fast f/1.8 200 mm commercial lenses are
used with a large 2160 mm-1 grating for high throughput. A stepping-motor controlled sine drive positions the grating, which is mounted on a precision rotary table. A high-resolution optical encoder on the grating stage
allows the grating angle to be measured with an absolute accuracy of 0.075 arcsec, corresponding to a
wavelength error ≤ 0.005 Å. At this precision, changes in grating groove density due to thermal expansion
and variations in the refractive index of air are important. An automated calibration procedure determines all
relevant spectrometer parameters to high accuracy. Changes in bulk grating temperature, atmospheric
temperature and pressure are monitored between the time of calibration and the time of measurement to
insure a persistent wavelength calibration.
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Submitted to: Review of Scientific Instruments (May 2010)
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Download PPPL-4526 (pdf 288 KB 4 pp)
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