分类： 天文学 >> 天文学 提交时间： 2023-02-19
摘要： Energetic X-ray radiations emitted from various accretion systems are widely considered to be produced by Comptonization in the hot corona. The corona and its interaction with the disc play an essential role in the evolution of the system and are potentially responsible for many observed features. However many intrinsic properties of the corona are still poorly understood, especially for the geometrical configurations. The traditional spectral fitting method is not powerful enough to distinguish various configurations. In this paper we intent to investigate the possible configurations by modeling the polarization properties of X-ray radiations. The geometries of the corona include the slab, sphere and cylinder. The simulations are implemented through the publicly available code, LEMON, which can deal with the polarized radiative transfer and different electron distributions readily. The results demonstrate clearly that the observed polarizations are dependent on the geometry of the corona heavily. The slab-like corona produces the highest polarization degrees, the following are the cylinder and sphere. One of the interesting things is that the polarization degrees first increase gradually and then decrease with the increase of photon energy. For slab geometry there exists a zero point where the polarization vanishes and the polarization angle rotates for 90^\circ. These results may potentially be verified by the upcoming missions for polarized X-ray observations, such as IXPE and eXTP.
分类： 光学 >> 量子光学 提交时间： 2023-02-19
摘要： We propose an enantio-detection method of chiral molecules in a cavity with external drive. The chiral molecules are coupled with a quantized cavity field and two classical light fields to form the cyclic three-level systems. The chirality-dependent cavity-assisted three-photon process in the three-level systems leads to the generation of intracavity photons. Simultaneously, the drive field also results in the chirality-independent process of the generation of intracavity photons. Based on the interference between the intracavity photons generated from these two processes, one can detect the enantiomeric excess of chiral mixture via monitoring the transmission rate of the drive field.
分类： 光学 >> 量子光学 提交时间： 2023-02-19
摘要： Two-dimensional mono-elemental material is an excellent saturable absorber candidate with low saturation intensity, large modulation depth, high nonlinearities, and fast recovery time of excited carriers. Typically, these mono-elemental material with two-dimensional structure possesses tunable bandgap from metallic to semiconducting according to different number of layers. The successful application of these materials as the saturable absorber has exploited the development of mode-locked fiber lasers. Therefore, this review is intended to provide an up-to-date information to the development of mono-elemental saturable absorber for the advances in mode-locked fiber laser, with emphasis on their material properties, synthesis process and material characterization. Meanwhile, issues and challenges of the review research topic will be highlighted and addressed with several concrete recommendations.
分类： 天文学 >> 天文学 提交时间： 2024-07-15 合作期刊: 《Research in Astronomy and Astrophysics》
摘要： A possible quasi-periodic oscillation (QPO) at frequency 7.045 × 10−5 Hz is found in the narrow-line Seyfert 1 galaxy Mrk 142 in the data of XMM-Newton collected on 2020 April 11. We find that the QPO signal is statistically significantly larger than the 5σ level and highly coherent with quality factor Q > 5 at the 0.3–10 keV band by using the method of the Lomb–Scargle Periodogram, the Weighted Wavelet Z-transform and the REDFIT. We analyze the data in 0.3–0.6 keV, 0.6–1 keV, 1–3 keV and 3–10 keV energy bands, and find obvious QPO signals at 0.3–0.6 keV and 1–3 keV bands. We then analyze the time-average spectra and time variability at the QPO frequency of 7.045 × 10−5 Hz, and use a model to fit them. We find that the QPO signal mainly comes from the X-ray hot corona.
分类： 光学 >> 量子光学 提交时间： 2023-02-19
摘要： Chaotic semiconductor lasers have been widely investigated for high-speed random bit generation, which is applied for the generation of cryptographic keys for classical and quantum cryptography systems. Here, we propose and demonstrate a self-chaotic microlaser with enhanced chaotic bandwidth for high-speed random bit generation. By designing tri-mode interaction in a deformed square microcavity laser, we realize a self-chaotic laser caused by two-mode internal interaction, and achieve an enhanced chaotic standard bandwidth due to the photon-photon resonance effect by introducing the third mode. Moreover, 500 Gb/s random bit generation is realized and the randomness is verified by the NIST SP 800-22 statistics test. Our demonstration promises the applications of microlasers in secure communication, chaos radar, and optical reservoir computing, and also provides a platform for the investigations of multimode nonlinear laser dynamics.
分类： 光学 >> 量子光学 提交时间： 2023-02-19
摘要： To enable an exploration of the initiation mechanism of nanosecond laser damage on a potassium dihydrogen phosphate (KDP) surface, a defect-assisted energy deposition model is developed that involves light intensity enhancement and a sub-band gap energy level structure. The simulations provide an explanation on why the laser-induced damage threshold (LIDT) of the KDP crystal is two orders of magnitude lower than the theoretical value. The model is verified by use of the transient images that appear during the laser damage. In addition, the dimensions of the "dangerous" surface defects that are the most sensitive to the laser damage are proposed. This work enables clarification on the initial energy deposition (IED) and initiation mechanism of the nanosecond laser damage caused by the KDP surface defects on micro-nano scale. It is helpful in understanding the laser-matter interactions and to improve the processing technique for high quality optical components.
分类： 物理学 >> 核物理学 提交时间： 2025-03-12
摘要： Research experiments regarding radiation effects demand the precise simulation of diverse radiation environments. In both the space and nuclear sectors, hybrid radiation fields with varying neutron-gamma ratios are prevalent. This study puts forward a convenient approach to regulate the neutron-gamma ratio and verifies its precision through experimental measurements at the 100MeV proton cyclotron of the China Institute of Atomic Energy. To achieve accurate and adjustable regulation of the neutron-gamma ratio within a range spanning from a few to several hundred, a neutron-gamma ratio regulator has been developed. The regulator was composed of different shielding materials with varying thicknesses and settled on the quasi-monoenergetic neutron beam line. The incident neutrons were generated by bombarding a lithium target with protons. Beam detection and calibration experiments were conducted, which demonstrated the effectiveness and superiority of generating hybrid radiation with adjustable neutron-gamma ratios in accelerator-based neutron fields.
分类： 天文学 >> 天文学 提交时间： 2023-02-19
Hao Cheng
Bao-Hua Sun
Li-Hua Zhu
Motohiko Kusakabe
Yun Zheng
Liu-Chun He
Toshitaka Kajino
Zhong-Ming Niu
Tian-Xiao Li
Cong-Bo Li
Dong-Xi Wang
Meng Wang
Guang-Shuai Li
Kang Wang
Lin Song
Ge Guo
Zhi-Yong Huang
Xiu-Lin Wei
Fu-WeI Zhao
Xiao-Guang Wu
摘要： Rare information on photodisintegration reactions of nuclei with mass numbers A \approx 160 at astrophysical conditions impedes our understanding of the origin of p-nuclei. Experimental determination of the key (p,\gamma) cross sections has been playing an important role to verify nuclear reaction models and to provide rates of relevant (\gamma,p) reactions in \gamma-process. In this paper we report the first cross section measurements of ^{160}Dy(p,\gamma)^{161}Ho and ^{161}Dy(p,n)^{161}Ho in the beam energy range of 3.4 - 7.0 MeV, partially covering the Gamow window. Such determinations are possible by using two targets with various isotopic fractions. The cross section data can put a strong constraint on the nuclear level densities and gamma strength functions for A \approx 160 in the Hauser-Feshbach statistical model. Furthermore, we find the best parameters for TALYS that reproduce the A \thicksim 160 data available, ^{160}Dy(p,\gamma)^{161}Ho and ^{162}Er(p,\gamma)^{163}Tm, and recommend the constrained ^{161}Ho(\gamma,p)^{160}Dy reaction rates over a wide temperature range for \gamma-process network calculations. Although the determined ^{161}Ho(\gamma, p) stellar reaction rates at the temperature of 1 to 2 GK can differ by up to one order of magnitude from the NON-SMOKER predictions, it has a minor effect on the yields of ^{160}Dy and accordingly the p-nuclei, ^{156,158}Dy. A sensitivity study confirms that the cross section of ^{160}Dy(p, \gamma)^{161}Ho is measured precisely enough to predict yields of p-nuclei in the \gamma-process.
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