Energetic proton acceleration from interaction of intense short circularly polarized laser pulse with a sandwich target is investigated using two-dimensional particle-in-cell simulation. The sandwich target consists of a hydrogen-plasma layer surrounded by carbon-plasma layers. It is found that the transverse electric fields generated at the plasma layer interfaces efficiently confine the longitudinally accelerated protons to within the hydrogen-plasma layer such that they are collimated and have smaller energy spread compared with a pure proton layer target. The proton energy spectrum can be controlled by adjusting the target parameters, in particular the width of the hydrogen-plasma layer and the density of the carbon-plasma layer.

Terahertz radiation can provide unprecedented vistas in physical studies such as transient matter state control and advanced free-electron manipulation. Here, we present one feasible path towards high-repetition-rate, intense THz sources by combining the wire-based THz source on a consecutively running, wire-conveying tape design. The proof-of-principle experimental results show an upper 30 mW average THz power output under 1 kHz laser excitation, which presents the first high-repetition-rate, and most importantly, portable and application in handy THz source that is generated by solid plasmas. The generated THz pulses are characterized with a 0.3 THz center frequency and ~0.3 THz bandwidth. We believe this tabletop laser-driven highrepetition-rate THz source will open a new door for THz and related interdisciplinary sciences.