Fig. 1. Response curves of the filtered AXUV diode array. The positions of the channel numbers indicate the spectral edges of each channel. Reproduced with permission from Ham et al., Rev. Sci. Instrum. 92(5), 053509 (2021). Copyright 2021 AIP Publishing.

Fig. 2. SNU X-pinch with the filtered AXUV diode array. The filtered AXUV diode array is mounted with half on each of the opposite vacuum ports. The distance between the wire load and AXUV diodes is 765 mm. Reproduced with permission from Ham et al., Rev. Sci. Instrum. 92(5), 053509 (2021). Copyright 2021 AIP Publishing.

Fig. 3. Currents measured by short circuit test. Black and red lines show the currents generated with charging voltages of 50 and 55 kV, respectively.

Fig. 4. (a) Typical x-ray signals of Cu wire X-pinches with charging voltages of 50 kV. The yellow areas indicate ranges of three bursts of x-rays. (b)–(d) Signals of the first, second, and third bursts, respectively, on narrower time scales.

Fig. 5. (a) Typical x-ray signals of Cu wire X-pinches with charging voltages of 55 kV. The yellow areas indicate the ranges of three bursts of x-rays. (b)–(d) Signals of the first, second, and third bursts, respectively, on narrower time scales.

Fig. 6. Synthetic spectra of Cu plasma with electron temperatures of 0.1 (black), 0.8 (red), and 1.5 (blue) keV. The electron density is 10²¹ cm⁻³.

Fig. 7. Synthetic spectra of Cu plasmas with electron densities of 10²¹ (black) and 10²³ (red) cm⁻³. The electron temperature is 0.8 keV.

Fig. 8. Reconstructed (dotted) and synthetic (solid) spectra with different plasma parameters: (a) electron density 10²³ cm⁻³, electron temperature 1.0 keV, and fast electron fraction 20%; (b) electron density 10²² cm⁻³, electron temperature 1.5 keV, and fast electron fraction 0%.

Fig. 9. X-ray power ratios with different electron temperatures and electron densities obtained from the FLYCHK code: (a) first ratio r₁; (b) second ratio r₂.

Fig. 10. Synthetic spectra with different characteristic energies of 10 (black), 20 (red), and 30 (blue) keV. The electron temperature and density are 1.6 keV and 10²³ cm⁻³, respectively, which are similar to those of an HS. The fast electron fraction is 9%.

Fig. 11. Synthetic spectra with different characteristic energies of 10 (black), 20 (red), and 30 (blue) keV. The electron temperature and density are 0.1 keV and 10²³ cm⁻³, respectively, which correspond to a low-temperature plasma. The fast electron fraction is 9%.

Fig. 12. Synthetic spectra with fast electron fractions of 0% (black) and 5% (red). The electron temperature is 0.8 keV and the electron density is 10²¹ cm⁻³.

Fig. 13. X-ray power ratios with fast electron fractions of 1% [(a) and (b)], 5% [(c) and (d)], and 15% [(e) and (f)].

Fig. 14. Synthetic spectra calculated with various plasma sizes: optically thin (black), 1 µm (red), 10 µm (blue), 100 µm (orange) and 1 mm (green). (a)–(d) Spectra without fast electrons: (a) and (b) spectra with electron temperature 0.8 keV and electron densities 10²¹ and 10²³ cm⁻³, respectively; (c) and (d) spectra with electron temperature 1.5 keV and electron densities 10²¹ and 10²³ cm⁻³, respectively. (e) and (d) Spectra with fast electron fraction 5%, electron temperature 0.8 keV, and electron densities of 10²¹ and 10²³ cm⁻³, respectively.

Fig. 15. Example of a comparison of the x-ray power ratios from the first peak of the 50 kV case. (a) and (b) Plasma parameters of the first and second ratios, respectively, with errors less than 10%. (c) Plasma parameters with averaged errors of the x-ray power ratios less than 10%.

Fig. 16. Signals of channels 1, 2, and 10 and temporal evolution of estimated electron densities, electron temperatures, and fast electron fractions for the first burst of the 50 kV case. Estimated plasma parameters of three x-ray peaks from peak-integrated x-ray powers are plotted together.

Fig. 17. Signals of channels 1, 2, and 10 and temporal evolution of estimated electron densities, electron temperatures, and fast electron fractions for the first burst of the 55 kV case. Estimated plasma parameters of two x-ray peaks from peak-integrated x-ray powers are plotted together.

Fig. 18. Signals of channels 1, 2, and 10 and temporal evolution of estimated electron densities, electron temperatures, and fast electron fractions for the second burst of the 50 kV case.

Fig. 19. Signals of channels 1, 2, and 10 and temporal evolution of estimated electron densities, electron temperatures, and fast electron fractions for the second burst of the 55 kV case.

Fig. 20. Signals of channels 1, 2, and 10 and temporal evolution of estimated electron densities, electron temperatures, and fast electron fractions for the third burst of the 50 kV case.

Fig. 21. Signals of channels 1, 2, and 10 and temporal evolution of estimated electron densities, electron temperatures, and fast electron fractions for the third burst of the 55 kV case.

Table 1. Filter materials and their thicknesses: (a) low-energy channels combined with beryllium filters with a thickness of 10 µm; (b) high-energy channels for x-ray energies above 2 keV. Reproduced with permission from Ham et al., Rev. Sci. Instrum. 92(5), 053509 (2021). Copyright 2021 AIP Publishing.