Laser-driven particle acceleration relies on the interaction of ultra-intense, ultrashort laser pulses with matter, producing strongly coupled plasmas that sustain electric fields several orders of magnitude higher than those achievable in conventional radiofrequency accelerators. These extreme fields enable the acceleration of electrons and ions over micrometer-scale distances, opening a pathway toward compact particle accelerators and secondary radiation sources. During the laser–target interaction, the irradiated region is rapidly ionized into a dense plasma, followed by explosive expansion, particle emission, and irreversible destruction or dispersion of the target material.
The inherently destructive nature of this interaction presents a critical challenge for high-repetition-rate operation, where stable and continuous target delivery is required. Conventional solid targets, such as rotating wheels or tape drives, are limited by mechanical complexity, debris generation, and restricted repetition rates. In contrast, cryogenic liquid and supercritical jets provide a continuous, renewable, and debris-free interaction medium with high chemical purity and well-defined geometry. Their flowing nature ensures that fresh material is delivered to the interaction point after each laser shot, enabling operation at repetition rates up to the kHz regime and beyond.
At ELI Beamlines, a dedicated cryogenic target platform has been developed to support next-generation laser–plasma experiments. The system is based on a closed-cycle cryocooler coupled to a temperature-controlled condensation cell, allowing the production of high-density cryogenic fluids directly from gas phase. Interchangeable micron-scale nozzles enable the formation of stable jets of nitrogen, argon, and krypton under vacuum conditions compatible with high-intensity laser systems. The design minimizes thermal fluctuations and ensures long-term operational stability, which is essential for user-oriented experimental campaigns.
Precise thermodynamic control of pressure and temperature allows fine tuning of jet parameters, including diameter, velocity, and density profile. These parameters play a crucial role in determining the laser energy coupling efficiency, plasma formation dynamics, and ultimately the quality and stability of the accelerated particle beams. In addition, the absence of solid debris significantly reduces contamination of the interaction chamber and downstream diagnostics, improving experimental reproducibility and reducing maintenance requirements.
The presented system represents a versatile and scalable solution for high-repetition-rate target delivery in laser-driven particle acceleration. Its modular design allows adaptation to different target materials and experimental conditions, including operation in the liquid or supercritical phase regime. Ongoing developments focus on extending the accessible parameter space, integrating advanced diagnostics, and exploring novel target geometries.

Keywords
Cryogenic systems|laser driven particle acceleration