Spectroscopy in the extreme ultraviolet on an electron beam ion trap

A compact grazing-incidence spectrometer was implemented on the Livermore electron beam ion trap facility for spectral measurements in the extreme ultraviolet spectral region. The spectrometer employed a 1200 rho/mm grating designed for flat-field focusing and a charge coupled device camera for readout. The instrument was used to measure line emission in the range from 25 to 220 Angstrom with a resolving power as high as 600. The performance and calibration of the instrument is described and spectra from highly charged nitrogen and iron ions are presented. Measurements of the K-shell spectrum of He-like N5+ are presented that confirm earlier wavelength determinations and illustrate the accuracy achievable with the instrument. Our measurement suggests a change in the line identifications of the forbidden He-like N5+ transition 1s2s S-3(1) --> (1)s(2) S-1(0) and of the Li-like N4+ collisional satellite transition 1s2s2p P-2(3/2) --> 1s(2)2s S-2(1/2) observed on the Alcator C-Mod tokamak. (C) 1999 American Institute of Physics. [S0034-6748(99)51801-7].