# High-energy ion beams generated with high efficiency using laser-driven 3D microstructures

## TL;DR

Researchers developed 3D-printed microstructures that efficiently generate high-energy proton beams using lasers, which could be useful for radiotherapy and other applications.

## Contribution

The study introduces laser-printed 3D microstructures that enable efficient and high-energy proton acceleration using the TNSA mechanism.

## Key findings

- 3D-printed microstructures achieved proton energies up to 110 MeV with ~10% laser-to-proton conversion efficiency.
- Microstructured targets outperformed thin solid-density foils in proton acceleration energy and yield.
- The structures are robust against laser prepulses and suitable for compact proton accelerators.

## Abstract

Laser-driven ion acceleration in plasma is being proposed as a source of ion beams with a high peak current that can be useful in many fields of science and medicine. Using this method, high proton energies have been achieved by increasing the laser power and by using ultrathin (≤ 200 nm) foils. However, this approach is limited by survivability of the nanotargets to laser prepulses and by difficulty in controlling the plasma acceleration properties. Here, we introduce a new target platform using two-photon polymerization, 3D laser-printed “clone” microstructures with average densities lower than solid that are relatively insensitive to the laser prepulse. Two types of microstructured targets consisting of either a multilayered log-pile or a stochastic arrangement of one micron diameter wires are used. Both demonstrate a higher energy and higher yield proton acceleration compared to thin solid-density foil targets by the robust target normal sheath acceleration (TNSA) mechanism. We find that when such 10–20 μm thick structures are irradiated with a petawatt laser, protons with energies up to 110 MeV and a laser-to-proton conversion efficiency of ~ 10% are obtained. Our work suggests that such microstructures optimized for 60–200 MeV compact proton accelerators are promising for future radiotherapy and other applications.