Schematic of the UF-CHERS system. The spectrometer consists of prism coupled transmission grating mounted on a conical bearing for fine wavelength scan and two f/2, 200 mm Nikkor telephoto lenses for light collimation. The figure also shows a bifurcated fiber assembly conveying light from eight different spectral channels at the output slit of the spectrometer to a detector box.
Spot diagrams from ray tracing for the exit focal plane. Three lines correspond to three wavelengths, from left to right 527 nm (green dots), 529 nm (blue dots), and 531 nm (red dots). The center to center distance in image is 11.2 mm for the 4 nm wavelength range. (a) A straight image is obtained by using a curved input slit, where the radius of curvature is 76 mm. (b) A curved image is obtained if the input slit is left straight.
Schematics of input and output fiber bundles. (a) shows the curved input fiber bundle. (b) shows the input end of the output fiber bundle. (c) shows both ends of the output fiber bundle. (d) shows the detector end of the output fiber bundle.
Time integrated data from five spectral channels fit to a Gaussian. Background is subtracted, and the signal levels are corrected for absolute intensity calibration. The measured ion temperature is about 570 eV.
The raw APD signal (a) and running average of the standard deviation of the APD signal after background subtracted (b). The signal tracks the photon noise from charge exchange emission line. CER data for the same plasma condition is shown in (c).
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