An Ion Doppler Spectrometer Instrument for Ion Temperature and Flow Measurements on SSPX
A high-resolution ion Doppler spectrometer has been installed on the Sustained Spheromak Plasma Experiment to measure ion temperatures and plasma flow. The system is composed of a 1 meter focal length Czerny-Turner spectrometer with diffraction grating line density of 2400 lines/mm, which allows for first order spectra between 300 and 600 nm. A 16-channel photomultiplier tube detection assembly combined with output coupling optics provides a spectral resolution of 0.0126 nm per channel. We calculate in some detail the mapping of curved slit images onto the linear detector array elements. This is important in determining wavelength resolution and setting the optimum vertical extent of the slit. Also, because of the small wavelength window of the IDS, a miniature fiber optic survey spectrometer sensitive to a wavelength range 200 to 1100 nm and having resolution 0.2 nm, is used to obtain a time-integrated spectrum for each shot to verify specific impurity line radiation. Several measurements validate the systems operation. Doppler broadening of C III 464.72 nm line in the plasma shows time-resolved ion temperatures up to 250 eV for hydrogen discharges, which is consistent with neutral particle energy analyzer measurements. Flow measurements show a sub-Alfvenic plasma flow ranging from 5 to 45 km/s for helium discharges.
- Research Organization:
- Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States)
- Sponsoring Organization:
- USDOE
- DOE Contract Number:
- W-7405-ENG-48
- OSTI ID:
- 945815
- Report Number(s):
- LLNL-JRNL-404111; RSINAK; TRN: US0901104
- Journal Information:
- Review of Scientific Instruments, Vol. 79; ISSN 0034-6748
- Country of Publication:
- United States
- Language:
- English
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