Search Results (3 total)

The frequency dependence of the electrorheological response was studied experimentally in a suspension of barium titanate spherical particles suspending in silicone oil. In the system, only one factor, namely the frequency of the applied electric field, affects the electrorheological effect. The experimental data reflect the frequency effect more reliably and more accurately. Under the sinusoidal electric fields, the shear stress increases sharply with frequency below 500  Hz and reaches a saturated value beyond 500  Hz. The phenomena can be explained well with the permittivity mismatch theory. More experiments indicate that the electrorheological effect should be the sum of the mismatch polarization and the interfacial polarization.

The interaction between a low-density electron cloud in a circular particle accelerator with a circulating charged particle beam is considered. The particle beam’s space charge attracts the cloud, enhancing the cloud density near the beam axis. It is shown that this enhanced charge and the image charges associated with the cloud charge and the conducting wall of the accelerator may have important consequences for the dynamics of the beam propagation. The tune shift due to the electron cloud is obtained analytically and compared to a new numerical model (QuickPIC) that is described here. Sample numerical results are presented and their significance for current and planned experiments is discussed.

This Letter examines the electron-hosing instability in relation to the drivers of current and future plasma-wakefield experiments using fully three-dimensional particle-in-cell simulation models. The simulation results are compared to numerical solutions and to asymptotic solutions of the idealized analytic equations. The measured growth rates do not agree with the existing theory and the behavior is shown to depend sensitively on beam length, shape, and charge. We find that even when severe hosing occurs the wake can remain relatively stable.