Hai-Shan Zhou

The effects of sand stabilization and revegetation on cryptogam species diversity and soil fertility in the Tengger Desert, Northern China

Cryptogamic crusts have long been regarded as important components of desert ecosystems. In order to reduce and combat the hazards of sandstorm and desertification, it is critical to conserve cryptogamic crusts in arid desert and semiarid regions. In this study, we characterized soil physical and chemical properties after revegetation on sanddunes stabilized with straw checkerboard. Revegetation accelerated the improvement of environmental conditions leading to the establishment and propagation of cryptogams on sanddunes in the Tengger desert region. Since revegetation began 44 years ago, 24 species of algae and 5 species of moss have established on fixed sanddunes in the Shapotou region in the northwest of China, but no lichens have been observed. Algal cover and species richness were found to be positively correlated with soil pH, contents of silt and clay, concentrations of HCO3−, Cl−, SO42-, Mg2+, soil organic carbon and N contents (p < 0.01), but were only weakly correlated with concentration of Ca2+, electrical conductivity (EC) and potassium content (K2O). The number of species and cover of mosses were positively correlated with soluble K+ and Na+ but no other relationships were apparent. The percent sand in composition of soil particle sizes, and soil bulk density were both negatively correlated to species number and cover for both cryptogam organisms. This study represents a successful example of restoration of cryptogam species diversity in arid desert regions.

Development and Optimization of STEP—A Linear Plasma Device for Plasma-Material Interaction Studies

The linear plasma device Simulator for Tokamak Edge Plasma (STEP) has been constructed at Beihang University, Beijing, to study plasma-material interactions (PMIs) for fusion reactor applications. The device can produce versatile low-energy and high flux plasma in laboratory experiments and is highly cost-effective to replicate the fusion-relevant plasma environment to study PMI processes. The attractive feature of the device is its compact design with a main body dimension of 1.5 × 1.5 × 0.8 m3 including the plasma source, vacuum chamber, magnetic coils, and diagnostics. A longitudinal magnetic field of up to 0.26 T is used to confine the plasma onto the target in an ∼1-m-long vacuum tube. It can produce a steady-state plasma of low impinging ion energy of <100 eV, ion flux up to 1022 m−2 · s−1, and fluence of >1026 m−2 per exposure. Various plasma species such as hydrogen, deuterium, helium, and nitrogen can be produced to manipulate PMI processes for different target grades. The STEP device provides an experimental platform to improve the understanding of PMIs, validate computational simulation results, and build a database of fusion material performance and lifetime.

Characteristics of edge pedestals in LHW and NBI heated H-mode plasmas on EAST

By using the recently developed Thomson scattering diagnostic, the pedestal structure of the H-mode with neutral beam injection (NBI) or/and lower hybrid wave (LHW) heating on EAST (Experimental Advanced Superconducting Tokamak) is analyzed in detail. We find that a higher ratio of the power of the NBI to the total power of the NBI and the lower hybrid wave (LHW) will produce a large and regular different edge-localized mode (ELM), and a lower ratio will produce a small and irregular ELM. The experiments show that the mean pedestal width has good correlation with , The pedestal width appears to be wider than that on other similar machines, which could be due to lithium coating. However, it is difficult to draw any conclusion of correlation between ρ * and the pedestal width for limited ρ * variation and scattered distribution. It is also found that T e/ T e is ~2 cm, which is the same as the AUG (ASDEX Upgrade), DIII-D and JET (Joint European Torus) results.