Laser Pulse Timing Found to Control Particle Acceleration Efficiency, Study Reveals
In high-intensity laser-matter interactions, such as laser-driven particle acceleration, physicists aim to achieve the maximum possible focused laser peak power—defined by the amount of energy delivered per unit area over the shortest possible pulse duration. With the same pulse energy and focus, the most intense peak is produced by using an ultra-short laser pulse.
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Why Laser Pulse Structure Matters
According to Károly Osvay, head of the National Laser-Initiated Transmutation Laboratory (SZTE NLTL) at the University of Szeged, scientists have long known that adjusting the laser's spectral phase allows the pulse's frequency components to arrive at the target in a controlled time sequence, effectively shaping the pulse in time.
"We examined what happens when the relative timing of these frequency components is altered," Osvay explained. "Our results show that their order directly affects which particles are accelerated most efficiently and to what degree. With deuterated solid-state foils, for instance, we can modify the balance between accelerated protons and deuterons, as well as the proportion of particles driven forwards or backwards. These effects are fundamentally governed by the complex temporal structure of the laser pulse."
The study's results were reported in Communications Physics.
Experiments Conducted at the LEIA Beamline
The team conducted the experiments using the LEIA beamline, which was designed, constructed and is operated by the SZTE National Laser-Initiated Transmutation Laboratory, and is powered by the laser systems at ELI ALPS. Supporting simulations were carried out by Zsolt Lécz, a research fellow based at ELI ALPS.
"Together with senior researchers from the SYLOS Group, we generated laser pulses of varying shapes and examined how the target responded," Osvay explained. "Our targets consisted of a very thin transparent film and a similarly thin sheet of liquid."
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Optimizing Ion Acceleration Performance
The researchers set out to optimize key characteristics of laser-accelerated ions, focusing not only on particles with the highest kinetic energy but also on the total energy carried by all accelerated ions.
Key Experimental Findings
- For any given target and material thickness, the temporal shape of a laser pulse can be precisely tailored
- Pulse shaping can achieve either maximum kinetic energy or optimal acceleration efficiency
- Reaching the highest peak power does not necessarily require the shortest possible pulse
- Carefully engineered time profiles are more important than pulse duration alone
- Each optimization approach demands distinct optical and laser technologies
Custom Lasers for Specific Particle Acceleration
Building on these results, Osvay's team now plans to develop lasers specifically optimized to accelerate particular charged particles—such as electrons, protons or deuterons—interacting with defined targets, including liquids, gases or thin sheets.
"Our aim is to develop a laser capable of accelerating charged particles with the highest possible efficiency," he explained. "This would allow us to deliver cost-effective laser solutions for the medical, microelectronics and energy sectors, including applications at an industrial scale."
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Broader Impact Across European Laser Facilities
Dr Osvay believes the findings will make it possible to maximize ion energies on the LEIA beamline, as well as on comparable facilities at ELI Beamlines in Dolnà Břežany, Czech Republic, and ELI Nuclear Physics in Măgurele, Romania.
Researchers using the LEIA beamline are also expected to benefit from higher neutron yields as a result of this optimization.
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