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Studying a kind of portable ultra-bright microfocus x-ray source

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Chinese Physics B 2009年第5期18卷 1807-1813页

作者：王凯歌王雷牛憨笨 Institute of photonics & photonic Technology Northwest University Institute of Optoelectronics Shenzhen University Xi'an Institute of Applied optics

This paper studies the properties of a kind of portable ultra-bright microfocus x-ray source with the Monte-Carlo method in detail. The new x-ray source consists of an electron-emission system, an electrostatic focusing system and a metal target. A crystal Lanthanum Hexaboride cathode, a Wehnelt grid and an extracted electrode compose the triode electrode electron-gun system. Two equal radius cylinder electrodes form the focusing system. The key factors determining the focus properties of the electron beam such as the ratio Dw/H, grid bias Vg, and the properties of the extracted electrode arc numerically studied. The calculated results reveal that when Dw/H, Vg, the length of the extracted electrode, and the distance between the grid and the extracted electrode equals 5, q）.6 kV, 10 mm, and 8 mm respectively, the electron beam focal spot can be concentrated down to 9 μm in radius and a reasonable focal length about 72.5 mm can be achieved, at the same time, the cathode emission currents can be as high as 30 mA.

关键词： microfocus x-ray source high brightness micro-focal spot Monte-Carlo method

First-principles calculation of the structural, electronic, elastic, and optical properties of sulfur-doping ε-GaSe crystal

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Chinese Physics B 2016年第8期25卷 266-273页

作者：黄昌保吴海信倪友保王振友戚鸣张春丽 Anhui Provincial Key Laboratory of photonic Devices and Materials Anhui Institute of Optics and Fine MechanicsChinese Academy of Sciences

The structural,electronic,mechanical properties,and frequency-dependent refractive indexes of GaSe1-xSx（x=0,0.25,and 1） are studied by using the first-principles pseudopotential method within density functional *** calculated results demonstrate the relationships between intralayer structure and elastic modulus in GaSe1-xSx（x=0,0.25,and 1）.Doping of ε-GaSe with S strengthens the Ga-X bonds and increases its elastic moduli of C（11） and C（66）.Born effective charge analysis provides an explanation for the modification of cleavage properties about the doping of e-GaSe with *** calculated results of band gaps suggest that the distance between intralayer atom and substitution of S（Se）,rather than interlayer force,is a key factor influencing the electronic exciton energy of the layer *** calculated refractive indexes indicate that the doping of ε-GaSe with S reduces its refractive index and increases its birefringence.

关键词： S-doping GaSe first-principles linear response mechanical properties

Calculating Hamiltonian parameters for Yb^(3+) in a low-symmetry lattice site,and fitting the structure and levels of Yb^(3+) :TaO_4 (= Gd,Y,and Sc)

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Chinese Physics B 2013年第6期22卷 522-529页

作者：张庆礼宁凯杰丁丽华刘文鹏孙敦陆江海河殷绍唐 The Key Laboratory of photonic Devices and Materials of Anhui Province Anhui Institute of Optics and Fine MechanicsChinese Academy of Sciences

An iterative method is used to find the values of the Hamiltonian parameters for Yb^3＋ in a given low-symmetry crys- talline site. Samples of Yb^3＋：RETaO4 （RE = Gd, Y, and Sc） were prepared and their structures were determined. Based on the obtained structural data, their orbital-spin parameters and crystal field parameters were fitted by the superposition model （SM）. Using the crystal field parameters obtained by the SM fitting as the initial parameters, the Hamiltonian parameters were fitted iteratively. The calculated and experimental energy levels for Yb^3＋：RETaO4 are consistent, and the maximal mean-root-square deviation is only 2.84 cm^- 1, indicating that the method is effective to determine the Hamiltonian parameters of Yb^3＋ in low-symmetry crystalline sites.

关键词： crystal field parameter rare earth X-ray diffraction Yb^3+ :RETaO4

Theoretical analysis of stack gas emission velocity measurement by optical scintillation

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Chinese Physics B 2014年第4期23卷 202-207页

作者：杨阳董凤忠倪志波庞涛曾宗泳吴边张志荣 Anhui Provincial Key Laboratory of photonic Devices and Materials Anhui Institute of Optics and Fine MechanicsChinese Academy of Sciences

Theoretical analysis for an online measurement of the stack gas flow velocity based on the optical scintillation method with a structure of two parallel optical paths is performed. The causes of optical scintillation in a stack are first introduced. Then, the principle of flow velocity measurement and its mathematical expression based on cross correlation of the optical scintillation are presented. The field test results show that the flow velocity measured by the proposed technique in this article is consistent with the value tested by the Pitot tube. It verifies the effectiveness of this method. Finally, by use of the structure function of logarithmic light intensity fluctuations, the theoretical explanation of optical scintillation spec- tral characteristic in low frequency is given. The analysis of the optical scintillation spectrum provides the basis for the measurement of the stack gas flow velocity and particle concentration simultaneously.

关键词： optical scintillation cross correlation flow velocity spectrum

Sensitive absorption measurements of hydrogen sulfide at 1.578 μm using wavelength modulation spectroscopy

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Chinese Physics B 2015年第3期24卷 180-184页

作者：夏滑董凤忠吴边张志荣庞涛孙鹏帅崔小娟韩荦王煜 Anhui Provincial Key Laboratory of photonic Devices and Materials Anhui Institute of Optics&Fine MechanicsChinese Academy of Sciences

Sensitive detection of hydrogen sulfide（H2S） has been performed by means of wavelength modulation spectroscopy（WMS） near 1.578 μm. With the scan amplitude and the stability of the background baseline taken into account, the response time is 4 s for a 0.8 L multi-pass cell with a 56.7 m effective optical path length. Moreover, the linearity has been tested in the 0–50 ppmv range. The detection limit achievable by the Allan variance is 224 ppb within 24 s under room temperature and ambient pressure conditions. This tunable diode laser absorption spectroscopy（TDLAS） system for H2 S detection has the feasibility of real-time online monitoring in many applications.

关键词： tunable diode laser spectroscopy wavelength modulation hydrogen sulfide detection low absorbance condition

Structural analysis and crystal-field calculations of Nd^(3+) in Gd_x Lu_(1-x) TaO_4(x = 0.85) polycrytalline

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Chinese Physics B 2012年第10期21卷 335-344页

作者：高进云张庆礼杨华军周鹏宇孙敦陆殷绍唐何晔 Anhui Provincial Key Laboratory of photonic Devices and Materials Anhui Institute of Optics and Fine MechanicsChinese Academy of Sciences Graduate School of the Chinese Academy of Sciences China Electronics Technology group Corporation No.26 Research Institute

The crystal structural parameters of Nd ^3＋-doped rare earth orthotantalate Gd x Lu 1 x TaO 4（x = 0.85） are determined by applying the Rietveld refinement to its X-ray diffraction,and its emission and excitation spectra at 77 K are *** relativistic model of ab initio self-consistent DV-Xα method,which is applied to the cluster NdO 8 in Gd x Lu 1 x TaO 4,and the effective Hamiltonian model are used to investigate its spin-orbit and crystal-field *** free-ions and crystal-field parameters are fitted to the experimental energy levels at 77 K with a root-mean-square deviation of 14.92 cm *** to the crystal-field calculations,96 levels of Nd ^3＋ are ***,the fitting results of free-ions and crystal-field parameters are compared with those already reported for Nd ^3＋：YAlO *** results indicate that the free-ion parameters are similar to those of the Nd3＋ in Gdx Lu1-x TaO4 and YAlO 3 hosts,and the crystal-field interaction of Nd^3＋ in Gdx Lu1-x TaO4 is stronger than that in YAlO 3.

关键词： rare earth orthotantalate crystal structure optical properties DV-Xα method crystalfield calculations

Optical and defect properties of S-doped and Al-doped GaSe crystals

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Chinese Physics B 2017年第9期26卷 248-251页

作者：黄昌保吴海信倪友保王振友陈诗静 Anhui Provincial Key Laboratory of photonic Devices and Materials Anhui Institute of Optics and Fine MechanicsChinese Academy of SciencesHefei 230031China

S-doped and Al-doped GaSe crystals are promising materials for their applications in nonlinear frequency conversion devices. The optical and defect properties of pure, S-doped, and Al-doped GaSe crystals were studied by using photoluminescence（PL） and Fourier transform infrared spectroscopy（FT-IR）. The micro-topography of（0001） face of these samples was observed by using scanning electron microscope（SEM） to investigate the influence of the doped defects on the intralayer and interlayer chemical bondings. The doped S or Al atoms form the SSe^0 or AlGa^＋1） substitutional defects in the layer GaSe structure, and the positive center of AlGa-^＋1 could induce defect complexes. The incorporations of S and Al atoms can change the optical and mechanical properties of the GaSe crystal by influencing the chemical bonding of the layer structure. The study results may provide guidance for the crystal growth and further applications of S-doped and Al-doped GaSe crystals.

关键词： doped GaSe crystals defect optical properties mechanical properties

Projectile angular-differential cross sections for single electron transfer in fast He^+-He collisions

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Chinese Physics B 2015年第3期24卷 127-135页

作者： Ebrahim Ghanbari-Adivi Hoda Ghavaminia Department of Physics and Isfahan Quantum optics group (IQOG) Faculty of ScienceUniversity of Isfahan

The four-body Coulomb–Born distorted wave approximation is applied to investigate the integral as well as projectile angular-differential cross sections for single-electron capture in the collision of energetic singly positive charged helium ions with helium atoms in their ground states. The formalism satisfies the correct boundary conditions. The influence of the dynamic electron correlations on the cross sections is studied by considering the inter electronic interactions in the complete perturbation potentials in post form. Also, the sensitivity of the cross sections to the static electronic correlations is studied by using the single-zeta and the highly correlated Byron–Joachain wave functions to describe the initial bound state of the active electrons. The obtained results for the energy range of 40–5000 ke V/amu are reported and compared with other three- and four-body theoretical data and available experimental measurements. The comparison leads us to discuss the validity of the applied approach and survey the interaction effects on the cross sections by recognizing the electron–electron interaction. Particularly, for differential cross sections, the comparison of the present four-body method with the experiment shows that the agreement is not as good as that for its three-body version.

关键词： Coulomb–Born distorted-wave approximation four-body approximation Coulomb boundary conditions differential and total cross secti

Dissipative dynamics of an entangled three-qubit system via non-Hermitian Hamiltonian: Its correspondence with Markovian and non-Markovian regimes

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Chinese Physics B 2021年第3期30卷 283-292页

作者： M Rastegarzadeh M K Tavassoly Laser and optics group Faculty of PhysicsYazd UniversityYazd 89195-741Iran

We investigate an entangled three-qubit system in which only one of the qubits experiences the decoherence effect by considering a non-Hermitian Hamiltonian,while the other two qubits are isolated,i.e.,do not interact with environment,***,the time evolution of the density matrix(for the pure as well as mixed initial density matrix)and the corresponding reduced density matrices are obtained,by which we are able to utilize the dissipative non-Hermitian Hamiltonian model with Markovian and non-Markovian regimes via adjusting the strange of the non-Hermitian term of the total Hamiltonian of the under-considered system.

关键词： non-Hermitian Hamiltonian entanglement concurrence measure Markovian and non-Markovian regimes