Shanghai Institute of Optics and Mechanics has made progress in collimating and accelerating proton beam with plasma prism driven by ultra strong vortex laser

Recently, the State Key Laboratory of Strong Field Laser Physics of the Shanghai Institute of Optics and Precision Machinery, Chinese Academy of Sciences has made progress in achieving efficient bunching proton acceleration by driving plasma prisms with ultra strong vortex lasers. Related achievements were published on Applied Physics Letters under the title of Collimated particle acceleration by vortex laser induced self structured "plasma lens".

It is always a difficult problem to obtain a proton beam with small divergence angle and high collimation in the application field of laser driven particle acceleration. In order to solve this problem, scientists have proposed the use of structural targets, cascade acceleration, magnetic quadrupole and other schemes to achieve the regulation of high-energy ions. In essence, these methods provide a "electric prism" or "magnetic prism" horizontally to focus high-energy ion beams. The configuration of the target is complex and expensive, and there are strict requirements for accurate time-space synchronization of multiple laser beams. For the high repetition rate PW, or even 10PW laser driven high repetition rate proton sources required for proton medicine, neutron generation, nuclear reaction and other applications, it is urgent to find a simple scheme that can reduce the experimental requirements.

Super intense Laguerre Gaussian (LG) laser provides us with an effective method to obtain repetitive proton sources. The research team found that using the pre pulse and main pulse of a single ring LG laser to interact with the simplest planar film target can "self align" to form concave plasma expansion, and then realize the normal convergence acceleration of the proton beam by the concave sheath field in the normal acceleration mechanism of the sheath field behind the target (divergence angle is 2.7 °), which is only 1/10 of the proton acceleration driven by the traditional Gaussian laser, and the maximum cutoff energy of the proton beam can be increased by about 50%, This mechanism provides a feasible and effective method for the wide application of high repetition rate proton source driven by high repetition rate PW laser in the future.

This achievement is based on the research team's work of putting forward a new type of optical tweezers - Relativistic Review Letters 122024801 (2019) in theory and obtaining the world's strongest LG laser generation (Physical Review Letters 125034801 (2020)) in experiment, which further develops the application of ultra strong LG laser and has broad application value.

Relevant research work has been supported by the general programs of the National Natural Science Foundation of China, the general programs of the Shanghai Natural Science Foundation of China, and the original innovation 0-1 program of the Chinese Academy of Sciences.

Fig. 1 (a) Intensity distribution of Gaussian laser and LG laser (b) Schematic diagram of LG laser focused proton acceleration

Fig. 2 Comparison of the distribution of proton divergence field driven by Gaussian laser and convergence field driven by LG laser

Source: Shanghai Institute of Optics and Precision Machinery, Chinese Academy of Sciences