K. X. Liu | Searcharxiv

arXiv2017

Study on high order modes in a beta=0.09 srf hwr cavity for 100 ma proton acceleration

There's presently a growing demand for cw high current proton and deuteron linear accelerators based on superconducting technology to better support various fields of science. Up to now, high order modes (HOMs) studies induced by ion beams with current higher than 10 mA and even 100 mA accelerated by low beta non-elliptical Superconducting rf (SRF) cavities are very few. Peking University has recently designed and fabricated a beta=0.09 162.5 MHz HWR cavity to study the key physics problems in accelerating beam with current of about 100mA. This paper focuses on the study of the HOM-induced power in this cavity. The incoherent beam energy loss induced by 100 mA beam through the HWR SRF cavity were obtained from both time domain solver and frequency domain eigenmodes spectrum method. We also analysed the possibility of coherent excitation of this cavity considering of manufacture errors.

physics.acc-ph↗

arXiv2016

Critical scaling of icosahedral medium-range order in CuZr metallic glass-forming liquids

The temperature evolution of icosahedral medium-range order formed by interpenetrating icosahedra in CuZr metallic glass-forming liquids was investigated via molecular dynamics simulations. Scaling analysis based on percolation theory was employed, and it is found that the size distribution of clusters formed by the central atoms of icosahedra at various temperatures follows a very good scaling law with the cluster number density scaled by $S^{-τ}$ and the cluster size $S$ scaled by $|1-T_c/T|^{-1/σ}$, respectively. Here $T_c$ is scaling crossover-temperature. $τ$ and $σ$ are scaling exponents. The critical scaling behaviour suggests that there would be a structural phase transition manifested by percolation of locally favoured structures underlying the glass transition, if the liquid could be cooled slowly enough but without crystallization intervening. Furthermore, it is revealed that when icosahedral short-range order (ISRO) extends to medium-range length scale by connection, the atomic configurations of ISROs will be optimized from distorted ones towards more regular ones gradually, which significantly lowers the energies of ISROs and introduces geometric frustration simultaneously. Both factors make key impacts on the drastic dynamic slowdown of supercooled liquids. Our findings provide direct structure-property relationship for understanding the nature of glass transition.

cond-mat.dis-nn↗