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 l/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 Å 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 ³S₁→1s^{2 1}S₀ and of the Li-like N⁴⁺ collisional satellite transition 1s2s2p ²P_3/2→1s²2s ²S_1/2 observed on the Alcator C-Mod tokamak.