Laser-plasma accelerators (LPAs) hold promise for generating compact, cost-effective proton beams, but challenges like target replacement and beam divergence have hindered their progress. Now, researchers have made a surprising breakthrough using a simple stream of water. Instead of solid targets, the team used a thin water sheet, replenished after each laser pulse. This solved the target replacement issue, but also unexpectedly focused the proton beam.
Traditional proton accelerators are bulky and expensive, limiting their deployment. LPAs offer a compact alternative but have struggled with efficiency due to target destruction by the high-intensity laser pulses and the resulting beam divergence. This new research tackles both problems simultaneously.
Researchers used a thin sheet of water as a target. The laser interaction produced a proton beam as expected, but surprisingly, the evaporated water formed a vapor cloud that focused the beam. This self-regenerating water target eliminates the need for constant target replacement, dramatically increasing the repetition rate. Furthermore, the vapor cloud’s interaction with the beam generated magnetic fields, naturally focusing the protons and reducing divergence tenfold. Beam efficiency also increased by a factor of 100 compared to solid targets.
This unexpected effect opens new avenues for LPA research. The team’s findings suggest this approach can be scaled to higher energies, producing even brighter beams. Notably, the beam delivered a 40 Gray radiation dose per shot, a level used in proton therapies, a first for LPAs at this repetition rate. Achieved with a low-energy laser, this advance brings LPAs closer to practical applications in medicine and industry.
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