Laser-driven ion acceleration has long been a powerful tool, capable of generating extreme energies in an instant. It has been hailed for applications ranging from cancer treatment to semiconductor processing and fusion research. But its most significant limitation?
The massive laser systems required to achieve it restrict practical use to extensive experimental facilities.
Now, researchers from TIFR Hyderabad have broken this barrier, demonstrating a method to accelerate ions to megavolt energies using tiny millijoule lasers, repeating the process a thousand times per second. Their work could pave the way for high-speed ion sources on university lab tabletops, revolutionizing accessibility to laser-driven ion acceleration.
Massive lasers delivering several joules of energy per pulse are typically needed to drive ion acceleration. These systems can only fire a few times per second—any faster, and overheating threatens delicate components.
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Smaller lasers, found in university labs, can fire thousands of times per second. Still, their lower energy levels restrict ion acceleration to a few kilovolts—far below the millions of volts achieved by large-scale systems.
So, how did the researchers bridge this gap? They turned a well-known problem—pre-pulses—into a solution.
Pre-pulses are small bursts of laser energy that occur before the main pulse. They often disrupt the ion acceleration process by damaging the target surface. Traditionally, scientists suppress them, adding complexity to laser systems. But instead of eliminating the pre-pulse, the TIFRH team harnessed its effects, unlocking a new pathway for efficient acceleration.
In their experiments, the pre-pulse sculpts a hollow cavity in a liquid microdroplet, creating a low-density plasma. This plasma acts as a breeding ground for the main laser pulse, triggering two giant waves that travel through it. As they collapse, they release bursts of high-energy electrons, driving proton acceleration to extreme speeds.
By leveraging this pre-pulse-generated plasma environment, the team demonstrated high-repetition-rate ion acceleration at a fraction of the usual laser intensity.
This approach not only avoids the need for ultra-powerful laser setups but also eliminates the need for complex pre-pulse suppression systems, making it far more scalable. The method could open doors to cost-effective, high-speed ion sources in fields like biomedicine, materials science, and particle physics.
With this breakthrough, the gap between large-scale laser accelerators and compact, accessible systems is finally shrinking, bringing high-speed ion beams into reach for labs worldwide.
Journal Reference:
- S. V. Rahul, R. Sabui, R. M. G. M Trines et al. High-repetition rate ion acceleration driven by a two-plasmon decay instability. Physical Review Research. DOI: 10.1103/PhysRevResearch.7.013240
