The enhancement and redistribution of a self-generated quasistatic magnetic field, due to the presence of the polarization field induced by partially ionized atoms, are analytically revealed when a linearly polarized intense and short pulse laser propagates in a partially stripped plasma with higher density. In particular, the shorter wavelength of the laser pulse can evidently intensify the amplitude of the magnetic field. These enhancement and redistribution of the magnetic field are considered physically as a result of the competition of the electrostatic field (electron-ion separation) associated with the plasma wave, the atomic polarization field, and the pondoromotive potential associated with the laser field. This competition leads to the generation of a positive, large amplitude magnetic field in the zone of the pulse center, which forms a significant difference in partially and fully stripped plasmas. The numerical result shows further that the magnetic field is resonantly modulated by the plasma wave when the pulse length is the integer times the plasma wavelength. This apparently implies that the further enhancement and restructure of the large amplitude self-magnetic field can evidently impede the acceleration and stable transfer of the hot-electron beam.

The recent experimental data of anomalous magnetic moments strongly indicate the existence of new physics beyond the standard model. An energetic µ + beam is a potential option to the expected neutrino factories, the future muon colliders and the µSR(the spin rotation, resonance and relaxation) technology. It is proposed a prompt acceleration scheme of the µ + beam in a donut wakefield driven by a shaped Laguerre-Gaussian (LG) laser pulse. The forward part of the donut wakefield can accelerate and also focus positive particle beams effectively. The LG laser is shaped by a near-critical-density plasma. The shaped LG laser has the shorter rise time and can enlarge the acceleration field. The acceleration field driven by a shaped LG laser pulse is six times higher than that driven by a normal LG laser pulse. The simulation results show that the µ + bunch can be accelerated from 200MeV to 2GeV and the transversal size of the µ + bunch is also focused from initial ω 0 = 5µm to ω = 1µm within several picoseconds.

The recent experimental data of anomalous magnetic moments strongly indicates the existence of new physics beyond the standard model. An energetic µ + beam is a potential option to the µ + rare decay, µSR(the spin rotation, resonance and relaxation) technology, future muon colliders and neutrino factories. It is proposed a prompt µ + acceleration in a nonlinear donut wakefield driven by a shaped steep-rising-front Laguerre-Gaussian (LG) laser pulse. An analytical model is given and shows that a µ + beam can be focused by the electron cylinder at the center line of the donut bubble and accelerated by the front part of the longitudinal wakefield. A shaped LG laser with a shorter rise time can push plasma electrons to generate a higher-density electron sheath at the front of the bubble, which can enlarge the acceleration field. The acceleration field driven by the steep-rising-front shaped LG laser pulse is about four times higher than that driven by a normal LG laser pulse. Our simulation results show that a 300MeV µ + bunch can be accelerated to 2GeV and its transverse size is focused from initial w0 = 5µm to w = 1µm in the donut bubble driven by the steep-rising-front shaped LG laser pulse with the normal intensity a = 22.

The muon plays a key role in the field of particle physics and applied physics. To build the neutrino factories or muon colliders, high-quality muon sources are needed. At present, we can only get the low-flux cosmic-ray muons and low-energy accelerator-generated muons. The key issue about accelerating a low-initial-energy muon beam in the plasma wakefield driven by an electron beam is the phase matching between muons and a wakefield. A plasma density down-ramp is considered as an effective method for accelerating a low-initial-energy muon beam, and the decreasing phase velocity at the back edge of the wakefield can lower the muon trapped energy threshold. A 100 MeV muon beam can be accelerated to 6.21 GeV in the plasma wakefield based on a negative plasma density gradient. The trapping and accelerating process can be controlled by adjusting the parameters of the density down-ramp.