High resolution extreme ultraviolet spectrometer for an electron beam ion trap.
An extreme ultraviolet spectrometer has been developed for spectroscopic studies of highly charged ions with an electron beam ion trap. It has a slit-less configuration with a spherical varied-line-spacing grating that provides a flat focal plane for grazing incidence light. Alternative use of two different gratings enables us to cover the wavelength range 1-25 nm. Test observations with the Tokyo electron beam ion trap demonstrate the high performance of the present spectrometer such as a resolving power of above 1000.
Electron density dependence of intensity ratio for FeXXII extreme ultraviolet emission lines arising from different ground levels in electron beam ion trap and large helical device
Extreme ultraviolet (EUV) spectra of highly charged iron ions in a wavelength range of 100–300 A have been observed from two different plasma sources of the Tokyo Electron Beam Ion Trap (Tokyo-EBIT) with a monoenergetic electron beam and a Large Helical Device (LHD) with Maxwellian electron energy. The excitation process of the spectral lines is compared between the two plasmas, and it is found that the excitation process for Fe XIX - Fe XXII ions is clearly different. Namely, the EUV emission lines from the EBIT plasma are only dominated by electron impact excitation connected to the ground state, but the excitation mechanism is not so simple in the LHD plasma. The difference in the excitation process is studied by measuring the intensity ratio of EUV emission lines (114.412 A [1s22s2p2 2P3/2 → 1s22s22p 2P3/2]/117.144 A [1s22s2p2 2P1/2 → 1s22s22p 2P1/2]) arising from different ground levels in the Fe XXII ions. The line intensity ratio has an extremely small value of 0.2 in the EBIT plasma with a low bea...
Measurement and Modeling of Density-Sensitive Lines of Fe XIII in the Extreme Ultraviolet
We present an analysis of the spectral emission of Fe XIII near 200 Å. High-resolution spectra were recorded at two densities (~2 × 1011 and ~1013 cm−3) in the laboratory and compared to collisional radiative model calculations based on the CHIANTI database, and to models using atomic data from distorted-wave and R-matrix calculations. The Fe XIII lines in this wavelength range are sensitive indicators of plasma density below ~ 1011 cm–3. The laboratory data thus test calculations in the astrophysical high-density limit. Significant differences between the measurements and models were found for several line ratios. Differences in the wavelengths employed in the different models also changed the agreement with the measurements. The best agreement was found for comparisons with CHIANTI.