Abstract: 〈sec〉In order to further improve the superconducting current carrying capacity of RE-Ba-Cu-O coated conductor under the action of strong magnetic field, ion irradiation is used to generate the pinning centers of introduced magnetic flux in the RE-Ba-Cu-O coated conductor. In this work, the H〈sup〉+〈/sup〉-ion irradiation of second-generation high-temperature superconductor RE-Ba-Cu-O strip is carried out by using the 320 kV high charge state ion synthesis research platform. Doppler broadened slow positron beam analysis combined with Raman spectroscopy is used to measure the change of microstructure in Y〈sub〉0.5〈/sub〉Gd〈sub〉0.5〈/sub〉Ba〈sub〉2〈/sub〉Cu〈sub〉3〈/sub〉O〈sub〉7–〈i〉δ〈/i〉 〈/sub〉(YBCO) sample irradiated by H〈sup〉+〈/sup〉 ions in a range of 5.0 × 10〈sup〉14〈/sup〉–1.0 × 10〈sup〉16〈/sup〉 ions/cm〈sup〉2〈/sup〉. The positron annihilation parameters in YBCO before and after irradiation are analyzed. It is found that after 100 keV H〈sup〉+〈/sup〉 ion irradiation, a large number of defects including vacancies, vacancy groups or dislocation groups are produced in the superconducting layer.〈/sec〉〈sec〉The larger the irradiation dose, the more the produced vacancy type defects are and the more complex the defect types, and the annihilation mechanism of positrons in the defects changes. Raman spectroscopy results show that with the increase of H〈sup〉+〈/sup〉 ion irradiation dose, the oxygen atoms in the coating rearrange, the plane spacing increases, the orthogonal phase structure of the coating is destroyed, and the degree of order decreases. The defects produced by such an ion irradiation lay a foundation for the introduction of flux pinning centers. Further research can be carried out in combination with X-ray diffractometer, transmission electron microscope, superconductivity and other testing methods to provide theoretical and practical reference for the optimization of material properties.〈/sec〉

Abstract: In order to further improve the superconducting current carrying capacity of REBCO coated conductor under strong magnetic field, ion irradiation is used to generate the pinning center of introduced magnetic flux in the REBCO coated conductor. In this paper, the H-ion irradiation of REBCO second generation high temperature superconductor strip was carried out by using the 320kV high charge state ion synthesis research platform. DB-SPBA combined with Raman spectroscopy was used to measure the change of microstructure in YBCO samples irradiated by H+ions within the range of 5.0×10〈sup〉14〈/sup〉~1.0×10〈sup〉16〈/sup〉. The positron annihilation parameters in YBCO before and after irradiation were analyzed. It is found that after 100 keV H+ion irradiation, a large number of defects including vacancy, vacancy group or dislocation group are produced in the superconducting layer. The larger the irradiation dose, the more vacancy type defects are produced, the more complex the defect types are, and the annihilation mechanism of positrons in the defects changes. Raman spectroscopy results show that with the increase of H+ion irradiation dose, the oxygen atoms in the coating rearrange, the plane spacing increases, the orthogonal phase structure of the coating is destroyed, and the degree of order decreases. The defects produced by such ion irradiation lay a foundation for the introduction of flux pinning centers. Further research can be carried out in combination with X-ray diffractometer, transmission electron microscope, superconductivity and other testing methods to provide theoretical and practical reference for the optimization of material properties.

Abstract: The polarization of protons emitted at six angles from the C12(d,p)C13 and Ca40(d,p)Ca41 ground state reactions has been measured. For the C12 reaction, the data at small angles are very close to the results of previous works, and in agreement with thesemiclassical sign rule jn=ln±1/2,P=(±). The value at θ= 115° has not been mea-sured before, we obtained P = 0.529± 0.068 at this angle. For the Ca40 reaction, the sign of polarization which we found in the region of small angles is also in agreement with the semiclassical sign rule, and is the same as those found in the work of Nemetz and of Boschitz, but is opposite to those obtained by Takeda and Bercaw. This difference may be due to the difference in the deuteron energy used, since in these experiments, the three with higher deuteron energies all gave the same positive sign of polarization while the three with lower deuteron energies all gave the same negative sign. After a survey of the polarization data now available we found that the semiclassical sign rule is still true to a certain degree, and that it may be possible to find out a modified sign rule for the use in the nuclear spectroscopy. In some cases, we found that the pattern of the polarization angular distribution is shifted towards small angles as the deuteron energy is increased, and this may be a characteristic of direct reactions. For the correspondence between the cross-section angular distribution and polarization angular distribution, we found that the position of a minimum in the cross-section curve may correspond to the position of a change in sign or of a maximum absolute value in the polarization curve, and that the position of a maximum in the cross-section curve may also correspond to the position of a change in sign in the polarization curve. We discuss these phenomena by using the distored wave theory.

Abstract: 〈 sec 〉 Traditionally, ion microbeam is generated by focusing or/and collimating to reduce the beam size to submicron level. The traditional setup for generating the microbeam consists of an expensive focusing and collimating system with a large space, based on electromagnetic fields. Meanwhile, the microbeam obtained through pure collimation of metal micro-tubes is limited by the fabrication processing, i.e. the size of beam spot is largely limited to a few microns and its manufacture is not as simple as that of a glass capillary. Inspired by early guidance effect research, the use of inexpensive and easy-to-make glass capillaries as the tool for ion external microbeam generation has become a new direction. 〈 /sec 〉 〈 sec 〉 In this work, we use a glass capillary with an open outlet (108 μm in diameter), which serves as a vacuum differential and collimating component, to produce a 2.5 MeV-proton microbeam directly from the linear accelerator into the atmosphere for measurements. We measure the beam spot diameter and energy distribution of the microbeam as a function of e tilt angle of the capillary. We also conduct calculations and ion trajectory analysis on the scattering process of 2.5 MeV protons on the inner walls. 〈 /sec 〉 〈 sec 〉 The measurement results show that when the tilt angle is around 0°, there are a direct transmission part that maintains the initial incident energy, and a scattering part with the energy loss in the microbeam. It is found that the proportion of directly transmitted protons and the beam spot size are highest near zero tilt angle. As the tilt angle increases, the beam spot diameter decreases; when the tilt angle is greater than the geometric angle, all the microbeams come from the scattering with the energy loss. The simulation combined with the ion trajectory analysis based on the scattering process can explain the experimental results. It is found that the large angle scattering determines the entire external microbeam spot, and the central region of the beam spot is composed of directly penetrating ions, whose size is determined by the geometric shape of the glass capillary, i.e. the outlet diameter and aspect ratio. 〈 /sec 〉 〈 sec 〉 The natural advantage of producing external micobeames easily and inexpensively through glass capillaries is their relative safety and stable operation, and the last but not least point is to simply locate the microbeams on the sample without complex diagnostic tools. The microbeams are expected to be widely used in fields such as radiation biology, medicine, and materials. 〈 /sec 〉

Abstract: 〈sec〉Potential energy curves (PECs), dipole moments (DMs) and transition dipole moments (TDMs) of the X〈sup〉2〈/sup〉Π, a〈sup〉4〈/sup〉Σ〈sup〉–〈/sup〉, A〈sup〉2〈/sup〉Σ〈sup〉–〈/sup〉, b〈sup〉4〈/sup〉Π, B〈sup〉2〈/sup〉Δ, C〈sup〉2〈/sup〉Σ〈sup〉+〈/sup〉, D〈sup〉2〈/sup〉Π, 2〈sup〉2〈/sup〉Σ〈sup〉+〈/sup〉 states correlating with the three lowest dissociation channels of AsH〈sup〉+〈/sup〉 cation are calculated by using the multireference configuration interaction (MRCI) method. The Davidson correction, core-valence (CV) correlation, and spin-orbit coupling (SOC) effect are all considered. The aug-cc-pV5Z all-electron basis set of H atom and the aug-cc-pwCV5Z-PP pseudopotential basis set of As atom are both selected in the calculation.〈/sec〉〈sec〉In the complete active space self-consistent field (CASSCF) calculation, H (1s) and As (4s4p) shell are selected as active orbitals, As (3p3d) shells are selected as closed orbitals, which keeps doubly occupation, the remaining electrons are in the frozen orbitals. In the MRCI calculation, As (3p3d) shells are used for CV correlation, and the calculation accuracy can be improved. The SOC effects are considered with Breit-Pauli operators.〈/sec〉〈sec〉All calculated states are bound states. The X〈sup〉2〈/sup〉Π is the ground state, which is a deep potential well, the dissociation energy is 3.100 eV. The b〈sup〉4〈/sup〉Π, C〈sup〉2〈/sup〉Σ〈sup〉+〈/sup〉 and D〈sup〉2〈/sup〉Π are weakly bound states. The spectroscopic parameters are obtained by solving radial Schrodinger equation. To the best of our knowledge, there has been no study of the spectroscopy of AsH〈sup〉+〈/sup〉 cation so far. Comparing with Ⅴ-hydride cations 〈i〉M〈/i〉H〈sup〉+〈/sup〉 (〈i〉M〈/i〉 = N, P, As), the orders of the energy levels of the low-lying states for three ions are identical. The dissociation energy and harmonic frequency both decrease with the increase of the atomic weight of 〈i〉M〈/i〉.〈/sec〉〈sec〉At spin-free level, the PEC of b〈sup〉4〈/sup〉Π state and the PEC of B〈sup〉2〈/sup〉Δ state cross at about 1.70 Å. When SOC effects are taken into account, according to the rule of avoid-crossing, the 〈inline-formula〉〈tex-math id="M5"〉\begin{document}$ {{{\rm{B}}^2}}{\Delta _{3/2}} $\end{document}〈/tex-math〉〈alternatives〉〈graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="21-20221104_M5.jpg"/〉〈graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="21-20221104_M5.png"/〉〈/alternatives〉〈/inline-formula〉state and 〈inline-formula〉〈tex-math id="M6"〉\begin{document}$ {{{\rm{B}}^2}}{\Delta _{5/2}} $\end{document}〈/tex-math〉〈alternatives〉〈graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="21-20221104_M6.jpg"/〉〈graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="21-20221104_M6.png"/〉〈/alternatives〉〈/inline-formula〉state change to the double potential wells, and the avoided crossing between the 〈inline-formula〉〈tex-math id="M7"〉\begin{document}$ {{{\rm{B}}^2}}{\Delta _{3/2}} $\end{document}〈/tex-math〉〈alternatives〉〈graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="21-20221104_M7.jpg"/〉〈graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="21-20221104_M7.png"/〉〈/alternatives〉〈/inline-formula〉 (〈inline-formula〉〈tex-math id="M8"〉\begin{document}$ {{{\rm{B}}^2}}{\Delta _{3/2}} $\end{document}〈/tex-math〉〈alternatives〉〈graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="21-20221104_M8.jpg"/〉〈graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="21-20221104_M8.png"/〉〈/alternatives〉〈/inline-formula〉) state and 〈inline-formula〉〈tex-math id="M9"〉\begin{document}${{\rm{b}}^4}{\Pi _{3/2}}$\end{document}〈/tex-math〉〈alternatives〉〈graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="21-20221104_M9.jpg"/〉〈graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="21-20221104_M9.png"/〉〈/alternatives〉〈/inline-formula〉 (〈inline-formula〉〈tex-math id="M10"〉\begin{document}${{\rm{b}}^4}{\Pi _{5/2}}$\end{document}〈/tex-math〉〈alternatives〉〈graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="21-20221104_M10.jpg"/〉〈graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="21-20221104_M10.png"/〉〈/alternatives〉〈/inline-formula〉) state is observed. The transition dipole moment (TDM) of the 〈inline-formula〉〈tex-math id="M11"〉\begin{document}$ {{{\rm{A}}^2}}{\Sigma ^ - } \to {{{\rm{X}}^2}}\Pi $\end{document}〈/tex-math〉〈alternatives〉〈graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="21-20221104_M11.jpg"/〉〈graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="21-20221104_M11.png"/〉〈/alternatives〉〈/inline-formula〉, 〈inline-formula〉〈tex-math id="M12"〉\begin{document}$ {{{\rm{a}}^4}}\Sigma _{1/2}^ - \to {{{\rm{X}}^2}}{\Pi _{1/2}} $\end{document}〈/tex-math〉〈alternatives〉〈graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="21-20221104_M12.jpg"/〉〈graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="21-20221104_M12.png"/〉〈/alternatives〉〈/inline-formula〉 and 〈inline-formula〉〈tex-math id="M13"〉\begin{document}$ {{{\rm{A}}^2}}\Sigma _{1/2}^ - \to {{{\rm{X}}^2}}{\Pi _{1/2}} $\end{document}〈/tex-math〉〈alternatives〉〈graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="21-20221104_M13.jpg"/〉〈graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="21-20221104_M13.png"/〉〈/alternatives〉〈/inline-formula〉 transition are also calculated. The TDM at the equilibrium distance of the 〈inline-formula〉〈tex-math id="M14"〉\begin{document}$ {{{\rm{a}}^4}}\Sigma _{1/2}^ - \to {{{\rm{X}}^2}}{\Pi _{1/2}} $\end{document}〈/tex-math〉〈alternatives〉〈graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="21-20221104_M14.jpg"/〉〈graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="21-20221104_M14.png"/〉〈/alternatives〉〈/inline-formula〉 spin-forbidden reaches 0.036 Debye, therefore, the SOC effect plays an important role. Based on the accurate PECs and PDMs, the Franck-Condon factors, spontaneous radiative coefficients, and spontaneous radiative lifetimes of the 〈inline-formula〉〈tex-math id="M15"〉\begin{document}$ {{{\rm{A}}^2}}{\Sigma ^ - } \to {{{\rm{X}}^2}}\Pi $\end{document}〈/tex-math〉〈alternatives〉〈graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="21-20221104_M15.jpg"/〉〈graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="21-20221104_M15.png"/〉〈/alternatives〉〈/inline-formula〉, 〈inline-formula〉〈tex-math id="M16"〉\begin{document}$ {{{\rm{a}}^4}}\Sigma _{1/2}^ - \to {{{\rm{X}}^2}}{\Pi _{1/2}} $\end{document}〈/tex-math〉〈alternatives〉〈graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="21-20221104_M16.jpg"/〉〈graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="21-20221104_M16.png"/〉〈/alternatives〉〈/inline-formula〉, and 〈inline-formula〉〈tex-math id="M17"〉\begin{document}$ {{{\rm{A}}^2}}\Sigma _{1/2}^ - \to {{{\rm{X}}^2}}{\Pi _{1/2}} $\end{document}〈/tex-math〉〈alternatives〉〈graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="21-20221104_M17.jpg"/〉〈graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="21-20221104_M17.png"/〉〈/alternatives〉〈/inline-formula〉 transition are also calculated.〈/sec〉

Abstract: Establishment and sustainment of the structure of internal transport barriers (ITBs) is an important guarantee for the magnetic fusion plasmas. The related physics process for the establishing and sustaining of ITBs with $q_{min} \simeq$ 2 is simply summarized:the "off-axis sawteeth" (OAS) and double tearing modes instability, fast ions induced Alfvén eigenmodes, thermal pressure gradient induced low-frequency modes (LFMs) instability, etc. Firstly, the burst of "off-axis sawteeth" (OAS) is an important criterion for the evaluating of reversed $q$-profile with $q_{min} \simeq$ 2. The excitation conditions, classification and the structure of precursor mode of OAS are given in detailed, and the collapse event is triggered by the magnetic reconnection of $m$/$n$=2/1 double tearing modes (DTM). Secondly, the beta-induced Alfvén eigenmodes (BAEs) and reversed shear Alfvén eigenmodes (RSAEs) are easily excited by the fast ions during the oscillation of OAS. The toroidal mode numbers of the two kinds of Alfvén waves are 1 $\leq n \leq$ 5, which are located at 1.98 $\leq R \leq$ 2.07 m with normalized minor radius 0.2 $\leq \rho \leq$ 0.45. The excitation conditions are investigated for the condition of $q_{min} \simeq$ 2:and three different physical variables of thermal pressure gradient, fast ions distribution function, and the toroidal flow or flow shear are considered. Thirdly, the low-frequency modes (LFMs) instabilities are excited by the pressure gradient during the oscillation of OAS. The general fishbone like dispersion relationship (GFLDR) is adopted for solving the basic features of LFMs:① the frequency of LFMs scale with ions diamagnetic frequency; ② the LFMs has the Alfvén polarization direction; ③ the LFMs are reactive-type kinetic ballooning modes. The excitation of LFMs is not relied on the fast ions, which is taken place at higher pressure gradient regime $\alpha \propto (1 + \tau) (1 + \eta_i)$, $\tau=T_e/T_i$, $\eta_i=L_{n_i}/L_{T_i}$. In the end, the suppression of OAS and establishment of ITBs are achieved. Three important processes are contained for the condition of $q_{min} \simeq$ 2 in EAST:① the tangential injection (NBI1L) of NBI is more easier for the suppression of OAS in comparison with the perpendicular injection (NBI1R); ② the micro-instability can be suppressed during the oscillation of OAS, and the reversed shear $q$-profile is more favorable in the establishment of the structure of ITBs; ③ the establishment of ITBs is accompanied by the excitation of Alfvén waves instabilities (bigger toroidal mode number:1 $\leq n \leq$ 5), the sustainment of ITBs is accompanied by the thermal ions temperature gradient induced instability (median size:5 $\leq n \leq$ 10). Therefore, understanding the establishment and suppression of OAS, the excitation of Alfvén wave instability and the redistributed fast ions, the related instability of thermal pressure gradient, which are important for the establishment of ITBs.

Abstract: A novel fast tunable electro-optic (EO) polymer waveguide grating is proposed an d designed. Its resonant wavelength can be linearly tuned by first-order EO effe ct with a high sensitivity of 6.1pm/V. Its spectrum characteristics depend stron gly on many optical parameters of grating, such as refractive index modulation, modulation function, grating period and period number. Material selection, fabri cation technology, EO tunability and polarization dependence of the polymer wave guide grating are also discussed. This waveguide grating not only dispenses with the slow wavelength tuning and large-scale integration inconvenience of convent ional optic fiber gratings, but have many advantages, such as high resonant wave length tuning sensitivity, using same fabrication technology as semiconductor de vices, and polarization independence.

Abstract: We present a quasi-three-dimensional efficient model for simulating and designing the terahertz quantum cascade laser with nonlinear axial waveguide structure, based on the finite difference beam propagation method. The traditional beam propagation method is widely used to simulate the beam profile of the passive waveguide. In order to study the active device, however, the current induced variation in the active region should also be considered in the numerical simulation model. In the model presented in this paper, the phase and the amplitude of the propagating confined field in the active waveguide are determined by a few linear and non-linear effects. The parameters relating to the linear effects, such as the intrinsic refractive index profile and the intrinsic losses of the waveguide under zero current injection, are calculated by using COMSOL-Multiphysics. While the non-linear effects, such as the modal gain and the refractive index variation induced by current injection, are considered in a rigorous way by including the rate-equation set for calculating the carrier dynamics in the active region. The parameters used in the rate-equation set are obtained by referring to the literature and fitting the experimental results of the considered terahertz lasers. By adding the current induced gain and refractive index variation, the presented beam propagation model is able to simulate many current-dependant properties of a laser, such as the output power, the gain guiding effect, and the self-focusing effect. We show in this paper that the latter two effects have influence on inner-waveguide beam profile, and the competitive balance between them determines the output beam quality. By utilizing this numerical model, the terahertz quantum cascade laser with tapered waveguide structure is simulated, and the influences of the taper angle on output power and beam quality are investigated. According to the simulation results, we find that there is an obvious increase in the output power when the taper angle is increased from 0 to 3 degree, while the increment in the output power decreases rapidly when the taper angle is further increased. Besides, we observe that for the far field the full width at half maximum of the output beam decreases sharply with increasing the taper angle. However, when the taper angle equals 8 degree, multiple lateral modes are observed, which indicates poor output beam quality of this device and poor beam coupling efficiency between this device and the power meter.Therefore, although the simulation results show that the output power of this device is higher than that of the device with 5 degree taper angle, the experiment results show that the measured output power is lower. So the taper angle is not the larger the better, but there exists an optimum value, at which the terahertz quantum cascade laser can achieve the highest effective output power.

Abstract: Quantum walk is a typical quantum computing model which is receiving significant attention in recent years from theory researchers. In this paper, we prove that the two major formulations for discrete quantum walks, coined and scattering, are unitarily equivalent on star graph. We then propose a new quantum search algorithm on star graph based on the scattering quantum walk. It is shown that the temporal complexity of the algorithm is the same as that in Grover algorithm, but success probability is greater than that in Grover algorithm when the objects are more than one third of total items.

Abstract: GaN-based LED wafers with nano-folding InGaN/GaN multiple quantum wells (MQWs) are grown on n-GaN nanopillar array templates which are fabricated using self assembled Ni nanodots as etching mask. Photoluminescence (PL) spectra of the wafer show uniform light emission wavelength over the whole area of it. No blue shift of the main peak is observed in the electroluminescence (EL) spectra of the LED devices fabricated with the wafer as the injection current increases from 10 mA to 80 mA. This can be ascribed to the reduced quantum confinement Stark effect (QCSE) and the resulting less band gap tilted by strain relaxation in the nano-folded MQWs. The device shows an excellent rectifying behavior with a forward voltage of 4.6 V under 20 mA injection current.