Our proposed ion acceleration scheme, micronozzle acceleration (MNA), generates

proton beams with extremely high kinetic energies on the giga-electron-volt (GeV)

order. The underlying physics and performance of MNA are studied with two-

dimensional particle-in-cell simulations. In MNA targets, a micron-sized hydrogen

rod is embedded inside a hollow micronozzle. Subsequent illumination of the target

along the symmetric axis by an ultraintense ultrashort laser pulse forms a strong

electrostatic field with a long lifetime and an extensive space around the downstream

tail of the nozzle. The electric field significantly amplifies the kinetic energies of the

accelerated protons, and > GeV protons are generated at an applied laser intensity

of 10²² W/cm². 

.