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With the decrease in dimension of ion traps employed in optical frequency standards and precision spectroscopy, the sensitivity of trapping behavior to trap geometry is more and more prominent. We present a guide for the design and construction of a miniature trap for a single ion confinement, and propose an optimized combination of rring/rendcap ≈ 0.5 and z0 ≈ r0 within the range of r0 = 0.7 ± 0.2 mm. Compared with the trap used by Huang et al. [Phys. Rev. A 84 (2011) 053841], the design can lead to an increase in trap pseudo-potential of more than 20% and a reduction on potential anharmonicity of more than 90%. The improvements make the trap closer to an ideal hyperboloidal trap to confine a single ion tightly with the benefit of weaker micro-motion. Considering the imperfection of electrodes machining and traps alignment, we also demonstrate the importance of trap symmetry, especially on two endcap electrodes. [ABSTRACT FROM AUTHOR]

We report the realization of quantum logic spectroscopy on the1S0→ 3P0clock transition of a single27Al+ion. This ion is trapped together with a40Ca+ion in a linear Paul trap, coupled by Coulomb repulsion, which provides sympathetic Doppler laser cooling and also the means for internal state detection of the clock state of the27Al+ion. A repetitive quantum nondemolition measurement is performed to improve the fidelity of state detection. These techniques are applied to obtain clock spectroscopy at approximately 45 Hz. We also perform the preliminary locking on the1S0 → 3P0clock transition. Our work is a fundamental step that is necessary toward obtaining an ultra-precision quantum logic clock based on40Ca+-27Al+ions. [ABSTRACT FROM AUTHOR]

The 27Al+ ion optical clock is one of the most attractive optical clocks due to its own advantages such as low black-body radiation shift at room temperature and insensitivity to the magnetic drift. However, it cannot be laser-cooled directly in the absence of 167nm laser to date. This problem can be solved by sympathetic cooling. In this work, a linear Paul trap is used to trap both 40Ca+ and 27 Al+ ions simultaneously, and a single Doppler-cooled40 Ca+ ion is employed to sympathetically cool a single 27Al+ ion. Thus a ‘bright-dark’ two-ion crystal has been successfully synthesized. The temperature of the crystal has been estimated to be about 7 mK by measuring the ratio of carrier and sideband spectral intensities. Finally, the dark ion is proved to be an 27Al+ ion by precise measuring of the ion crystal's secular motion frequency, which means that it is a great step for our 27Al+ quantum logic clock. [ABSTRACT FROM AUTHOR]

In clinical practice, brain death is the irreversible end of all brain activity. Compared to current statistical methods for the determination of brain death, we focus on the approach of complex networks for real-world electroencephalography in its determination. Brain functional networks constructed by correlation analysis are derived, and statistical network quantities used for distinguishing the patients in coma or brain death state, such as average strength, clustering coefficient and average path length, are calculated. Numerical results show that the values of network quantities of patients in coma state are larger than those of patients in brain death state. Our findings might provide valuable insights on the determination of brain death. [ABSTRACT FROM AUTHOR]

We report stable narrow linewidth laser systems based on self-developed Littman configuration external cavity diode lasers (ECDLs). The frequency of the ECDL is stabilized to a high fineness ultralow-expansion glass reference cavity with the Pound-Drever-Hall technique. By heterodyne beating of two identical systems, we conclude that the linewidth of each ECDL is reduced to lower than 150 Hz and its frequency stability reaches 4.3 x 10-14 at an averaging time of 1s, the averaged long-term frequency drift is less than 0.2 Hz/s over 30 h measurement time. [ABSTRACT FROM AUTHOR]

Arc efficiency is a critical criterion for assessing the performance of the ion source. High arc efficiency is necessary for a high power ion source, because it can decrease the load of the arc power supply. Thus the relationship between the discharge parameters (gas pressure, arc voltage, filament current, bias resistance connecting between the anode and plasma grid) and the arc efficiency is investigated in experiment especially. It is found that with increasing pressure, the arc efficiency increases fast if the pressure is below 0.4 Pa, but when it is above 0.4 Pa, the arc efficiency remains unchanged or increases slowly. If we increase the arc voltage or filament current, the arc efficiency decreases. The bias resistance also influences the arc efficiency, at the same pressure the arc efficiency increases with resistance. [ABSTRACT FROM AUTHOR]

A circular magnetic multi-pole line-cusp ion source with a nominal 45 keV 25 A hydrogen ion beam is developed for the neutral beam injector of the HL-2A tokomak. At present, this bucket ion source can produce a 40 keV 20 A hydrogen ion beam for less than 100 ms on a test bed, and a 35 keV 13 A ion beam for 300 ms on the injector of the HL-2A tokomak. The 1/e half-width of the ion beam power profile is about 6.0 +- 0.2 cm at the position of 3.26m downstream from ion source, and the corresponding divergence degree is nearly 1.1. The optimum perveance matched conditions were obtained experimentally, and were in good agreement with the values from experiential equation of Uhlemann et al. The maximum of optimum perveance reached 2.2 x 10[?]6 A/V1.5 for 38 keV beam energy. An ion beam with above 60% H+ species fraction can be achieved, which was measured by Ha light Doppler shift spectroscopy. According to research results, a neutral beam with a total power of more than 0.6 MW was successfully injected into the plasma of the HL-2A Tokomak in 2008. [ABSTRACT FROM AUTHOR]