Xianbin Du

Simple dissipative quartz crystal microbalance and methods for determining dissipation decay constants

We describe a simple dissipative quartz crystal microbalance (QCM) and two simple methods for determining the dissipation factor. The microbalance consists of an oscillator circuit interfaced with a personal computer. The oscillation voltages are undersampled through a low speed data acquisition card. Both methods for determining the resonant frequency and the dissipation factor assume a limited variation of the resonant frequency, which is the case for general applications of QCMs. The first method directly fits the undersampled data with a nonlinear function. The second method determines the resonant frequency of a quartz crystal by Fourier transformation of the acquired data. The dissipation factor is obtained by rectifying the undersampled data and then fitting them with an exponential function.

Upgrade of X-ray crystal spectrometer for high temperature measurement using neon-like xenon lines on EAST

A two-crystal X-ray spectrometer system has been implemented in the EAST tokamak to simultaneously diagnose high- and low-temperature plasmas using He- and H-like argon spectra. But for future fusion devices like ITER and Chinese Fusion Engineering Test Reactor (CFETR), argon ions become fully stripped in the core and the intensity of the H-like lines will be significantly at high temperatures (Te > 5 keV). With increasing auxiliary heating power on EAST, the core plasma temperature could also reach 5 keV and higher. In such conditions, the use of a xenon puff becomes an appropriate choice for both ion-temperature and flow-velocity measurements. A new two-crystal system using a quartz 110 crystal (2d = 4.913 Å) to view He-like argon lines and a quartz 011 crystal (2d = 6.686 Å) to view Ne-like xenon spectra has been deployed on a poloidal X-ray crystal spectrometer. While the He-like argon spectra will be used to measure the plasma temperature in the edge plasma region, the Ne-like xenon spectra will be used for measurement in the hot core. The new crystal arrangement allows a wide temperature measurement ranging from 0.5 to 10 keV or even higher, being the first tests for burning plasmas like ITER and CFETR. The preliminary result of lab-tests, Ne-like xenon lines measurement will be presented.

Mechanical and Viscoelastic Properties of Polymer Layers on Solid-Liquid Interfaces

Mechanical and viscoelastic properties of polymer layers adsorbed on solid-liquid interfaces from solutions can be distinctly different from that of the corresponding polymers in bulk solution due to interaction of molecules with the interfaces. We have studied the mechanical and viscoelastic properties of polyethylene glycol (PEG) solution boundary layers using a quartz crystal resonator technique. The viscosity and shear moduli of the PEG solution boundary layers as a function of PEG concentration are determined from the resonant frequency shift and the dissipation broadening of the resonance of the quartz crystal. The results show that the viscosity and the shear modulus of a boundary layer increase with the PEG concentration in the solution. The increase depends on the molecular weight and the molecular configuration. For solutions with large PEG molecules the viscoelastic properties of the solution boundary layers are distinctly different from that of corresponding bulk solutions. These behaviors can be explained in terms of solid-like behaviors due to an increased concentration of PEGs next to the quartz crystal surface and the interactions between PEG polymers and the interfaces.