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Centimeter-Level High-Quality Electron Cascade Acceleration Achieved with THz Accelerator

August 25, 2021      Author:

Recently, the research team led by Academician Zhang Jie and Professor Xiang Dao from School of Physics and Astronomy, SJTU demonstrated the feasibility of high-quality cascade acceleration of relativistic electrons on the scale of centimeter by using a multi-period narrow-band terahertz source generated by a femtosecond laser in a periodically polarized lithium niobate crystal, combined with an ultra-short electron beam provided by a megavoltage ultrafast electron diffraction device. The energy dispersion and energy stability of the electron beam were maintained in the experiment with close to 100% charge coupling efficiency. The research team made a breakthrough from "THz acceleration" to "THz accelerator". Their work was published in the August 2021 issue of Physical Review Letters, titled "Stable and Scalable Multistage Terahertz-Driven Particle Accelerator" (H. Tang, L. Zhao et al. al., Phys. Rev. Lett. 127, 074801 (2021)).

Particle accelerators have been widely used in scientific research, national defense, industry, and medicine. In scientific research, for example, 1/3 of the Nobel Prizes in physics after 1939 are related to accelerators. In the past decades, advanced acceleration concepts and technologies such as plasma acceleration, laser dielectric acceleration, and terahertz acceleration have become important research directions in the field of accelerators.

The team led by Academician Zhang Jie and Professor Xiang Dao have conducted systematic research on the interaction between strong field terahertz pulses and relativistic electron beams in recent years. They have made significant breakthroughs in terahertz sources, precision preparation of terahertz structures, precision synchronous matching of terahertz fields and electron beams, and have achieved a series of results.

This research is mainly supported by the Major Program of Shanghai Science and Technology Commission (No. 18JC1410700), The National Science Fund for Innovative Research Groups (No. 11721091), and The National Science Fund for Distinguished Young Scholars (No. 11925505). PhD student Tang Heng and postdoctoral fellow Zhao Lingrong are the co-first authors of the paper.

 

Source: School of Physics and Astronomy, SJTU

Translated by Zhang Yue

 

ABSTRACT:

Particle accelerators that use electromagnetic fields to increase a charged particle's energy have greatly advanced the development of science and industry since invention. However, the enormous cost and size of conventional radio-frequency accelerators have limited their accessibility. Here, we demonstrate a miniaccelerator powered by terahertz pulses with wavelengths 100 times shorter than radio-frequency pulses. By injecting a short relativistic electron bunch to a 30-mm-long dielectric-lined waveguide and tuning the frequency of a 20-period terahertz pulse to the phase-velocity-matched value, precise and sustained acceleration for nearly 100% of the electrons is achieved with the beam energy spread essentially unchanged. Furthermore, by accurately controlling the phase of two terahertz pulses, the beam is stably accelerated successively in two dielectric waveguides with close to 100% charge coupling efficiency. Our results demonstrate stable and scalable beam acceleration in a multistage miniaccelerator and pave the way for functioning terahertz-driven high-energy accelerators.