The space-resolving measurement of X-ray flux from a specific area (laser spot, re-emitting wall, or capsule) inside the hohlraum is an ongoing and critical problem in indirectly driven inertial-confinement fusion experiments. In this work, we developed a new two-dimensional space-resolving flux detection technique to measure the X-ray flux from specific areas inside the hohlraum by using the time- and space-resolving flux detector (SRFD). In two typical hohlraum experiments conducted at the Shenguang-III prototype laser facility, the X-ray flux and radiation temperature from an area 0.2 mm in diameter inside the hohlraum were measured through the laser entrance hole (LEH). The different flux intensities and radiation temperatures detected using the SRFD from the inner area of the LEH were compared with the result measured using the flat-response X-ray detector from the entire LEH. This comparison was also analyzed theoretically. The inner area detected using the SRFD was found to be the re-emitting wall area alone. This important improvement in space-resolving X-ray flux measurement will enhance the current X-ray flux space characterization techniques, thereby furthering the quantitative understanding of X-ray flux space behavior in the hohlraum.
A transmission grating coupled with an X-ray charge coupled device (CCD) is used to quantitatively measure the proportion of high-order harmonics of the soft-X-ray source of beam line 4B7B. The results show that the monochromatic X-ray has third-order and second-order harmonics. The proportion of second-order harmonic of 4B7B is less than 9.0% and the third-order harmonic is below 0.7% when no suppressing method is applied. When suppression methods are used, the proportion of second-order harmonic is less than 1.7% and the third-order harmonic is ignorable.
Self-powered ultraviolet (UV) photodetectors play an important role in environmental monitoring, aerospace and other fields because of the advantage of effective light response without an external power supply. Herein, a p-CuI/n-GaN heterojunction UV photodetector with self-powered function is constructed by vacuum thermal evaporation method. At 365 nm UV irradiation, the photodetector has an on/off ratio of 7536, a large photocurrent (~35 mA) and a fast response time (rise/decay time of 52.22/66.11 ms) at zero bias. There was no significant decrease in photocurrent during the 100 on/off cycles of the continuous test, and the photocurrent of the photodetector can maintain 93.17% of the initial value after continuous operation for 15 h without bias voltage. The rise in ambient temperature exhibits a negative effect on the UV photodetector, but when it is naturally cooled from 80℃ to room temperature (RT), the photocurrent can restore to 95% of the original level. Furthermore, the photodetector maintains superior stability even after being stored in air for 1 month of without package. This work not only proves the controllable preparation strategy of CuI thin films, but also provides an efficient structure for self-powered UV photodetectors with high operational and storage stability.
Warm dense matter (WDM), a kind of transition state of matter between cold condensed matter and high temperature plasma, is one of the main research objects of high energy density physics (HEDP). Compared with the structure of isolated atom, the electron structure of WDM will change significantly because of the influences of density and temperature effect. As WDM is always strongly coupled and partly degenerate, accurate theoretical description is very complicated and the accurate experimental research is also very challenging. In this paper, the density effect on the warm dense matter electron structure based on the X-ray fluorescence spectroscopy is studied. The warm dense titanium with density larger than solid density is produced experimentally based on a specially designed hohlraum. Then, the titanium is pumped to emit fluorescence by using the characteristic line spectrum emitted by the laser irradiating the pump material (Vanadium). The X-ray fluorescence spectra of titanium with different states are diagnosed by changing the delay time between the pump laser and drive laser. The experimental fluorescence spectrum indicates that the difference in energy between <inline-formula><tex-math id="M5">\begin{document}${\mathrm{K}}_{\text{β}} $\end{document}</tex-math><alternatives><graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="24-20231215_M5.jpg"/><graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="24-20231215_M5.png"/></alternatives></inline-formula> and <inline-formula><tex-math id="M6">\begin{document}$ {\mathrm{K}}_{\text{α}} $\end{document}</tex-math><alternatives><graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="24-20231215_M6.jpg"/><graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="24-20231215_M6.png"/></alternatives></inline-formula> (<inline-formula><tex-math id="M7">\begin{document}$\Delta E_{{\mathrm{K}}_{\text{β}}\text{-}{\mathrm{K}}_{\text{α}}}$\end{document}</tex-math><alternatives><graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="24-20231215_M7.jpg"/><graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="24-20231215_M7.png"/></alternatives></inline-formula>) of the compressed titanium (7.2–9.2 g/cm<sup>3</sup>, 1.6–2.4 eV) is about 2 eV smaller than that of cold titanium. Two theoretical methods, i.e. finite-temperature relativistic density functional theory (FTRDFT) and two-step Hartree-Fock-Slater (TSHFS), are used to calculate the fluorescence spectrum of warm dense titanium. The calculated results indicate that the energy difference (<inline-formula><tex-math id="M10">\begin{document}$\Delta E_{{\mathrm{K}}_{\text{β}}\text{-}{\mathrm{K}}_{\text{α}}} $\end{document}</tex-math><alternatives><graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="24-20231215_M10.jpg"/><graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="24-20231215_M10.png"/></alternatives></inline-formula>) decreases with the increase of density but changes slowly with the increase of temperature during the calculated state (4.5–13.5 g/cm<sup>3</sup>, 0.03–5 eV). The FTRDFT overestimates the density effect on the line shift, while TSHFS underestimates the density effect. The future work will focus on optimizing the experimental method of X-ray fluorescence spectroscopy, obtaining X-ray fluorescence spectrum of titanium with more states, and then testing the theoretical method for warm dense matter.
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