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By 3D particle-in-cell simulation and analysis, we propose a plasma lens to make high intensity, high contrast laser pulses with a steep front. When an intense, short Gaussian laser pulse of circular polarization propagates in near-critical plasma, it drives strong currents of relativistic electrons which magnetize the plasma. Three pulse shaping effects are synchronously observed when the laser passes through the plasma lens. The laser intensity is increased by more than 1 order of magnitude while the initial Gaussian profile undergoes self-modulation longitudinally and develops a steep front. Meanwhile, a nonrelativistic prepulse can be absorbed by the overcritical plasma lens, which can improve the laser contrast without affecting laser shaping of the main pulse. If the plasma skin length is properly chosen and kept fixed, the plasma lens can be used for varied laser intensity above 10(19) W/cm(2).

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A deuteron radio-frequency quadrupole (RFQ) is being built by the RFQ group at Peking University. It is a very compact high-current RFQ, operating at 162.5 MHz in continuous-wave mode. By optimizing the beam dynamics design, our simulations reached 98% transmission efficiency for acceleration of the 50-mA deuteron beam from 50 keV to 1 MeV, with an intervane voltage of 60 kV and a length of 1.809 m. This RFQ adopts a window-type structure, with low power consumption and sufficient mode separation, with no stabilizing rods required. Its magnetic coupling windows have been optimized by both electromagnetic simulation and the construction of an equivalent circuit model. The empirical equation based on the circuit model provides a new way to evaluate the effect of the window size on the frequency. In addition, an aluminum model of the full-length RFQ has been built and tested, and the results show good agreement with the simulations. During the tuning process, the magnetic coupling effect between quadrants was found to be unique to the window-type RFQ. We also propose a method to estimate the effects of different degrees of electric field unflatness on the beam transmission. For the cooling system design, the results of thermostructural analysis, verified by comparing results from ANSYS and CST, show that the special cooling channels provide a high cooling efficiency around the magnetic coupling windows. The maximal deformation of the structure was approximately 75 μm. The beam-loading effect caused by a high current, and the coupler design, are also discussed.