7th Asia-Pacific Conference on Plasma Physics, 12-17 Nov, 2023 at Port Messe Nagoya

Laboratory measurement of FeX MIT effect for coronal magnetic field diagnosisand very high accuracy calibration of visible light wavelengths in an EBITYANG Yang1, XU Guoqin1, LI Wenxian2, SI Ran1, CHEN Chongyang1, BAI Xianyong2, TIAN Hui3,
LI Yajing1, YAO Ke1, XIAO Jun1, Roger HUTTON1, ZOU Yaming1
1
Shanghai EBIT Laboratory, Key Laboratory of Nuclear Physics and Ion-Beam Application (MOE),Institute of Modern Physics, Fudan University, 2 Key Laboratory of Solar Activity, National
Astronomical Observatories, CAS, 3 School of Astronomy and Space Science, CASe-mail (speaker):yangyang@fudan.edu.cn
The magnetic field is extremely important forunderstanding the properties of the solar corona.
However, there are still difficulties in the direct
measurement of coronal magnetic fields. The discoveryof the magnetic-field-induced transition (MIT) in Fe X,
which was also observed in the coronal spectra, opened
up a new method for measuring the coronal magneticfield.
In this work, we obtained the Fe X extreme ultraviolet(EUV) spectra in the wavelength range of 174–267 Å inShanghai high-temperature superconducting electron
beam ion trap, and for the first time, verified the effect of
MIT in Fe X by measuring the line ratios between
257.262 Å and reference line of 226.31 Å (257/226) atdifferent magnetic field strengths. The plasma electron
density that may affect the 257/226 value was also
obtained experimentally and then verified by comparing
the density-sensitive line ratios with the theoreticalprediction, and there was good agreement between them.
By comparing the simulated line ratios of 257/226 withthe experimental values at given electron densities andmagnetic fields, the critical energy splitting of thefine-structure levels, one of the most critical parameters
to determine the MIT transition rate, was obtained.
Possible reasons which may lead to the difference
between the obtained energy splitting and therecommended value in previous work are discussed.
Magnetic field response curves for the 257/226 value
were calculated and compared to the experimental results,
which is necessary for future MIT diagnostics.[1]The 4s24p 2P3/2 – 2P1/2 magnetic dipole transition in
Ga-like ions is interested in developing of high precise
highly charged ion clock. we present direct observationsof the transition in Mo11+ and Ru13+ ions at an electron
beam ion trap. Internal and external calibration methods
are used for determining the wavelength of the Mo11+ andRu13+ lines, respectively. Both measurements reachprecision levels of a few ppm. Compared with theavailable values, the current results significantly improvethe experimental uncertainty.[2]Figure 2. (a) Electron beam energy dependence of theRu13+ spectra, and (b) the corresponding charge state
distributions of ruthenium ions.

2.0LineRatio_257.262 / 226.31

1.9
1.8
1.7

ΔE/cm-1 = 8.6 log Ne/cm-3 = 10.2
ΔE/cm-1 = 8.6 log Ne/cm-3 = 10.4
ΔE/cm-1 = 8.6 log Ne/cm-3 = 10.6
ΔE/cm-1 = 2.29 log Ne/cm-3 = 10.8
ΔE/cm-1 = 2.29 log Ne/cm-3 = 11.0
ΔE/cm-1 = 2.29 log Ne/cm-3 = 11.2

1.6
1.5
1.4
1.3
Experiment data
1255 G
1679 G2102 G

1.2
1.1
1.08001000

1200

1400 1600 1800
Magnetic field (G)20002200Figure 1. Theoretical and experimental values of line
ratios of 257.262 Å and 226.31 Å versus the magneticfield.

Figure 3. The experimental wavelength (in air) of the
Ru13+ and Ne2+ lines. The two lines are measured
alternately.
References[1] G.Xu, et al, Astro. Phys. J. 937, 48 (2022)[2] Y. Li et al, J. Phys. B: At. Mol. Opt. Phys. 54, 235001(2021)