[en] Nuclear plant seismic instrument system (KIS)is used for scouting the activity of seism near nuclear plant, and providing analytical information to operators of plant according to seism data. To ensure KIS to perform properly, KIS must be installed and debugged according to standard means. This article introduced the frame, the means of installation and the means of debugging about the renewed KIS of QinShan Phase II plant which has reference to the KIS installation of other nuclear plants. (authors)

[en] Nuclear plant seismic instrument system (KIS)is used for scouting the activity of seism near nuclear plant, recording the seismic data, and providing analytical information to operators of plant who can keep the nuclear reactor in security. The recorded seismic data can be preserved for a long time and help the design institution to validate the anti-seismic design. This article introduced the elements, function, frame and subsystems about the KIS of QinShan Phase II plant. (authors)

[en] A new method of compensating for the excess micromotion along two directions in three-dimensional Coulomb crystals is reported in this paper; this method is based on shape control and optical imaging of a Coulomb crystal in a sectioned linear ion trap. The characteristic parameters, such as the ion numbers, temperatures, and geometric factors of different ion crystals are extracted from the images and secular motion excitation spectra. The method of controlling the shape of the ion crystals can be used in cold ion experiments, such as sympathetically cooling, structural phase transitions, and selective-control of ions, etc. (paper)

[en] We observed the linear-to-zigzag structural phase transition of a ⁴⁰Ca+ crystal in a homemade linear Paul trap. The values of the total temperature of the ion crystals during the phase transition are derived using the molecular-dynamics (MD) simulation method. A series of simulations revealed that the ratio of the radial to axial secular frequencies has a dependence on the total temperature that obeys different functional forms for linear and zigzag structures, and the transition point occurs where these functions intersect; thus, the critical value of the ratio of secular frequencies that drives the structure phase transition can be derived. (atomic and molecular physics)

[en] We explore nonreciprocal transmission behaviors in an optomechanical system, in which two dissipative cavity modes are coupled with each other and also with two parity-time-symmetric mechanical modes. Two cavities, one of which is probed by a weak field, are driven by two strong control fields, respectively. With the active-passive mechanical-resonator scheme, such a closed-loop four-mode system can show an amplification behavior of the probe field with three transmission windows based on optomechanically induced transparency (OMIT). Due to the breaking of the time-reversal symmetry corresponding to the relative phase between two control fields, the amplified nonreciprocal transmission can be realized in the middle OMIT window and its direction can be controlled via the phase modulation. In addition, the system can also show asymmetric group velocities of light propagation, i.e. the tunable asymmetric fast–slow light effects, for example, slow lights along a direction and fast lights along the other one. It is of interest that the dynamic asymmetric fast-to-slow light conversion can be realized periodically by phase modulation. Such a system of three OMIT windows, acting as the schemes of the directional amplifier and all-optical switch of the direction and velocity of light, may provide underlying applications in the photonic network and information communicating process involving multi-signal transmission. (paper)

[en] In this paper, we report a method by which the ion quantity is estimated rapidly with an accuracy of 4%. This finding is based on the low-temperature ion density theory and combined with the ion crystal size obtained from experiment with the precision of a micrometer. The method is objective, straightforward, and independent of the molecular dynamics (MD) simulation. The result can be used as the reference for the MD simulation, and the method can improve the reliability and precision of MD simulation. This method is very helpful for intensively studying ion crystal, such as phase transition, spatial configuration, temporal evolution, dynamic character, cooling efficiency, and the temperature limit of the ions. (paper)

[en] In this paper, we introduce a method of quantitatively evaluating and controlling the space charge effect of a laser-cooled three-dimensional (3D) ion system in a linear Paul trap. The relationship among cooling efficiency, ion quantity, and trapping strength is analyzed quantitatively, and the dynamic space distribution and temporal evolution of the 3D ion system on a secular motion period time scale in the cooling process are obtained. The ion number influences the eigen-micromotion feature of the ion system. When trapping parameter q is ∼0.3, relatively ideal cooling efficiency and equilibrium temperature can be obtained. The decrease of axial electrostatic potential is helpful in reducing the micromotion heating effect and the degradation in the total energy. Within a single secular motion period under different cooling conditions, ions transform from the cloud state (each ion disperses throughout the envelope of the ion system) to the liquid state (each ion is concentrated at a specific location in the ion system) and then to the crystal state (each ion is subjected to a fixed motion track). These results are conducive to long-term storage and precise control, motion effect suppression, high-efficiency cooling, and increasing the precision of spectroscopy for a 3D ion system. (paper)

[en] The ⁷Li⁺ ion is one of the most important candidates for verifying QED theory and obtaining the precise value of the fine-structure constant α. However, direct laser cooling of trapped Li⁺ ions will lead to strong background fluorescence which will influence the spectrum detection. The sympathetic cooling technique is a good choice to solve the problem. In this work, we report sympathetic cooling of ⁷Li⁺ ions to few mK using ⁴⁰Ca⁺ ions in a linear Paul trap. A mixed ion crystal of ⁴⁰Ca⁺ ions and ⁷Li⁺ ions are obtained. We also analyze the motion frequency spectra of pure ⁴⁰Ca⁺ ions and mixed ions. (authors)