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The propagation of low energy continuous ion beams through background plasmas is studied numerically using a three-dimensional particle-in-cell code. It is found that after the well known self-modulation effect, a secondary self-modulation occurs, leading to a trimodal energy spectrum of the ion beam. The accuracy of the “focusing regions” concept is studied by comparing the phase relation of the wakefield and beam density. Furthermore, the form of the wakefield induced by two counter-propagation ion beams is verified.

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An accelerator electron bunch is focused and modulated in a plasma lens and then converted into a gamma-ray source using bremsstrahlung radiation in a dense material. In the linear regions with beam density much smaller than plasma density, a proper plasma density needs to be chosen to produce a high quality gamma-ray beam with a small spot size and low divergence, which can be applied in the radiograph of complex and dense objects with sub-millimeter resolution. As the bunch charge increases and bunch density approaches plasma density, micro-bunching of the bunch due to the nonuniform transverse wakefield and bunch energy chirp is observed, leading to a significant increase in gamma-ray beam divergence.

The study of the interaction between ion beam and plasma is very important to the areas of inertial fusion energy and high energy density physics (HEDP). With detailed one-dimensional (1D) electromagnetic particle-in-cell (PIC) simulations, we investigate here the interaction of a laser-accelerated proton beam assuming an ideal monoenergetic beam with a gas-discharge plasma. After the saturation stage of the two-stream instability excited by the proton beam, significant high energy electrons are observed, with maximum energy approaching 2 MeV, and a new two-stream instability occurs between the high energy electrons and background electrons. The trajectories of plasma electrons are studied, showing the process of electron trapping and de-trapping from the wakefield.