Responsivity calibration of the extreme ultraviolet spectrometer in the range of 175-435 Å

Abstract

We reported the relative responsivity calibration of the grazing-incidence flat-field EUV spectrometer between 175 and 435 Å by means of two methods. The first method is implemented by measuring the diffraction efficiency of the grating with synchrotron radiation light source. Considering the transmission efficiency and quantum efficiency of the other optical components in the spectrometer, the total responsivity was then obtained. The second one was carried out by measuring line emissions from C3+, N4+ and O3+ ions at Shanghai high temperature super conductor electron beam ion trap (SH-HtscEBIT). The EUV spectra were also simulated theoretically via a collisional radiative model. In the calculation, the second-order relativistic many-body perturbation theory approach based on the flexible atomic code was used to calculate the energy levels and transition rates; the close-coupling R-matrix approach and relativistic distorted wave method were utilized to calculate the collision strength of electron impact excitation. In comparison with the spectroscopic measurements at EBIT device, the differences between the measured and simulated relative line intensities were obtained. The responsivity calibration for the spectrometer was then achieved by a 3rd degree polynomial function fitting. Our measurement shows that the responsivity between 175 and 435 Å varies by factor of ∼ 46. The two results of calibration demonstrated a consistency within an average deviation of 24%. In addition, an evaluation of our calculations on C iv, N v and O iv line emissions in this wavelength region was given.

First Laboratory Measurement of Magnetic-field-induced Transition Effect in Fe x at Different Magnetic Fields

“…The spectral line at 257.262 Å (blend of MIT, E1 transition, and M2 transition) mentioned in Section 1, as well as the reference line at 226.31 Å, was measured with a resolving power of approximately 1000. The line intensity ratios 257/226 were calculated from the measurements and corrected with the grating efficiency, the CCD quantum efficiency, and the transmission efficiency of the aluminum filter in the grazingincidence flat-field spectrometer (Tu et al 2017a). It was found that the charge-state distributions of the trapped ions can be monitored by comparing the relative intensities between the Fe VIII 185.213 Å, Fe XI 188 Å, and Fe X lines.…”

“…On the measurement side, the ratios of line intensities depend on the accuracy of the grating efficiency, the CCD quantum efficiency, and the transmittance of the aluminum filter in front of the spectrometer. The efficiency calibration of the grating at a synchrotron light source was made three years ago (Tu et al 2017a) and applied to the efficiency values of the filter from its factory test a few years before. Although the wavelength range between 257.262 Å and 226.31 Å is not that large, it is still possible that the efficiency ratio at these two wavelengths will change over time.…”

“…The inhomogeneity and instability of the magnetic field generated by the coils in the SH-HtscEBIT would introduce an uncertainty of less than 5%. There is 10% caused by fitting Gaussian profiles for spectral lines, 10% from statistical error, and 10% from efficiency calibration (Tu et al 2017a) of the spectrometer. (A possible systematic offset for the relative efficiencies of the spectrometer at different wavelengths was not included but is discussed in Section 4.4.)…”

Resonant Electron Impact Excitation of 3d levels in Fe$^{14+}$ and Fe$^{15+}$

“…The background, mainly due to the dark counts of the MCP, was estimated from the wavelength region where no line was observed, and subtracted. The correction on the relative quantum efficiency of the grating was made based on the data by Tu et al (2017). The correction was about 9 % in the largest case between the lines (a) and (d).…”