Symmetry breaking and competition effect in phase transitions.

This study is started from a photon-magnon model with a competition effect of the level attraction and repulsion, its Hermiticity is mainly decided by a phase-dependent and asymmetric coupling factor, namelyφ = 0 for Hermitian andϕ=πfor non-Hermitian. Then an extensional study predicts the quantum critical behaviors using an Hermitian and even no-Hermitian photon-spins model with an additional second-order drive. The numerical results firstly indicate that this coupling phaseφcan function the protective effect on quantum phase transitions (QPTs), and the new tricritical points can not only be modulated by this nonlinear drive, but also be influenced by the dissipation and the collective decoherence. Secondly, this competition effect can also induce a reversal of the value of order parameters between the positive and negative. This study can also bring more important results of QPTs toward the issue of symmetry breaking and non-Hermiticity.

[Application of Extreme-Ultraviolet Ar Spectra Analysis in the Study of Divertor Impurity Screening in EAST Tokamak].

Divertor impurity injection on Tokamak is the most important means to achieve divertor impurity screening efficiency. In this paper, a fast-response extreme-ultraviolet (EUV) spectrometer is used to monitor the Ar emission lines during the EAST(Experimental Advanced Superconducting Tokamak)divertor Ar injection experiment. Based on the NIST(National Institute of Standards and Technology)atomic spectrum database, the emission lines from different ionized Ar ions in 2～50 nm wavelength range, e.g. Ar Ⅳ, Ar Ⅳ-Ⅺ and Ar ⅩⅣ-ⅩⅥ, are being identified. Ar ⅩⅥ 35.39 nm and Ar Ⅳ 44.22 nm with the ionization energy of 918.4 and 59.6 eV respectively are being monitored during the experiment with Ar puffing to observe the behavior of Ar impurities in different regions in plasmasimultaneously. The preliminary analysis on divertor impurity screening efficiency is carried outwith the time evolution of intensities of two Ar emission lines. The results of experiment puffing from the same gas puffing inlet (e. g. from lower outer target inlet) and withdifferent plasma configurations (e. g. lower single null, upper single null) show that the screening effect on the impurity injected from the divertor region is better thanfrom the main plasma region; the screening effect of lower divertor and particle pumping by internal cryopump installed in lower divertor is stronger than upper divertor.