A compact laser-driven plasma accelerator for megaelectronvolt-energy neutral atoms

Abstract

Tremendous strides have been made in charged-particle acceleration using intense, ultrashort laser pulses. Accelerating neutral atoms is an important complementary technology because such particles are unaffected by electric and magnetic fields and can thus penetrate deeper into a target than ions. However, compact laser-based accelerators for neutral atoms are limited at best to millielectronvolt energies. Here, we report the generation of megaelectronvolt-energy argon atoms from an optical-field-ionized dense nanocluster ensemble. Measurements reveal that nearly every laser-accelerated ion is converted to an energetic neutral atom as a result of highly efficient electron transfer from Rydberg excited clusters, within a sheath around the laser focus. This process, although optimal in nanoclusters, is generic and adaptable to most laser-produced plasmas. Such compact laser-driven energetic neutral atom sources could have applications in fast atom lithography for surface science and tokamak diagnostics in plasma technology.