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Multi-GeV Electron Beam Generation by a Dual-Stage Laser-Wakefield Accelerator Pumped by Petawatt La
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Multi-GeV Electron Beam Generation by a Dual-Stage Laser-Wakefield Accelerator Pumped by Petawatt Laser Pulses

Since the proposal of laser-wakefield acceleration (LWFA) by T. Tajima and J. M. Dawson in 1979, LWFA has been regarded as a promising method to develop a compact electron accelerator for generating a multi-GeV electron beam because it has a huge field gradient comparing to conventional rf accelerators. The LWFA is an acceleration of electron bunches in a travelling plasma wave with a phase velocity near to the speed of light, excited by an intense laser pulse as shown in figure 1.

In fast decade, the LWFA technology has been rapidly progressed but the energy of the electron beam from the LWFA is still limited in 1~2 GeV level due to the power of the driving laser pulses. Recently, PW laser systems have been developed and so they can provide an opportunity to realize multi-GeV electron beam generation.

A research group at the Gwangju Institute of Science and Technology has realized electron acceleration over 3-GeV energy by using the PW laser system, PULSER, of the Ultrashort Quantum Beam Facility. In this research, a dual-stage acceleration scheme has been applied to LWFA with a PW laser pulse in order to separate the injection stage and the acceleration stage as shown in figure 2. The 4-mm and 10-mm long helium gas jets have been used for the dual-stage acceleration with different electron densities of 21018 cm-3 and 81017 cm-3, respectively.

A 400-MeV electron beam from the first 4-mm gas jet was injected into a 10-mm jet for further acceleration and an electron beam over 3 GeV was produced after the second acceleration stage as shown in figure 2. The divergence of the electron beam after the acceleration stage was about 4 mrad, and the charge of the electron beam for energies over 2-GeV is estimated to be about 10 pC. The electron spectrum has two separate peaks at 1.1 and 2.7 GeV while the maximum energy of the electron spectrum reached 4 GeV.

This result can be a basis for the development of a compact multi-stage laser-wakefield electron accelerator with multi-GeV energy by using PW laser pulses.

Fig. 1: Mechanism of laser wakefield acceleration using intense laser pulses.

Fig. 2: (a) Experimental layout for LWFA using dual-stage acceleration pumped by a PW laser pulse and (b) the energy spectrum of electron beam from the dual-stage acceleration

References

1. H . T. Kim, K. H. Pae, H. J. Cha, I J. Kim, T. J. Yu, J. H. Sung, S. K. Lee, T. M. Jeong, and J. Lee, "Enhancement of Electron Energy to the Multi- GeV Regime by a Dual-Stage Laser-Wakefield Accelerator Pumped by Petawatt Laser Pulses", Phys. Rev. Lett. 111, 165002 (2013).

 
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