筒内高功率脉冲磁控放电的电磁控制与优化

高功率脉冲磁控溅射(Hi PIMS)技术被提出以来就受到广泛关注,其较高的溅射材料离化率结合适当的电磁控制,可产生高致密度、高结合力和高综合性能的涂层,但其沉积速率低、放电不稳定、溅射材料离化率差异较大.我们设计了一种筒形溅射源,通过对结构的设计优化,利用类空心阴极放电效应,使问题得到解决.然而其靶面切向磁场不均匀,电子逃逸严重,进而造成等离子体密度偏低,且放电不均匀.本文通过对其放电和等离子体分布进行仿真,提出电场阻挡和磁铁补偿两种方案,研究了不同电场控制条件下的放电行为和等离子体分布.结果表明:增加电子阻挡屏极可以生成势阱,从而有效抑制电子从边缘的逸出;优化后的磁铁补偿可以显著提高靶面横向磁场的均匀性及靶面利用率.两种方案同时作用时,Hi PIMS放电刻蚀环面积更大、且更加均匀.     

Surface Emission of Quark Gluon Plasma at RHIC and LHC

Within the framework of a factorization model, we study the behaviour of nuclear modification factor in Au Au collisions at RHIC and Pb-Pb collisions at LHC. We find that the nuclear modification factor is inversely proportional to the radius of the quark-gluon plasma and is dominated by the surface emission of hard jets. We predict the nuclear modification factor R^LHC AA - 0.15 in central Pb-Pb collisions at LHC. The study shows that the factorization model can be used to describe the centrality dependence of nuclear modification factor of the high transverse momentum particles produced in heavy ion collisions at both RHIC and LHC.     

Hadron Multiplicities in Pb＋Pb Collisions at the Large Hadron Collider and Pomeron Loop Effects

We study the pseudo-rapidity distribution of hadron multiplicities of high energy Pb＋Pb collisions by using color glass condensate dynamics at LHC/ALICE in the fixed coupling case. It is found that after including the pomeron loop effects the charged hadron multiplicities at central rapidity are about 1500 for central Pb＋Pb collisions, which are significantly smaller than the saturation based calculations, ～ 1700 ÷ 2500 and compatible with that based on a study of multiplicities in the fragmentation region.