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• High Power Laser Science and Engineering
• Vol. 9, Issue 3, 03000e43 (2021)
Hao Zhang1, Jie Zhao1, Yanting Hu1, Qianni Li1, Yu Lu1, Yue Cao1, Debin Zou1, Zhengming Sheng2、3、4, Francesco Pegoraro5, Paul McKenna2, Fuqiu Shao1, and Tongpu Yu1、*
Author Affiliations
• 1Department of Physics, National University of Defense Technology, Changsha410073, China
• 2SUPA, Department of Physics, University of Strathclyde, GlasgowG4 0NG, UK
• 3Collaborative Innovation Center of IFSA (CICIFSA), Key Laboratory for Laser Plasmas (MoE) and School of Physics and Astronomy, Shanghai Jiao Tong University, Shanghai200240, China
• 4Tsung-Dao Lee Institute, Shanghai200240, China
• 5Department of Physics Enrico Fermi, University of Pisa, and CNR/INO, Pisa56122, Italy
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Abstract

X/γ-rays have many potential applications in laboratory astrophysics and particle physics. Although several methods have been proposed for generating electron, positron, and X/γ-photon beams with angular momentum (AM), the generation of ultra-intense brilliant γ-rays is still challenging. Here, we present an all-optical scheme to generate a high-energy γ-photon beam with large beam angular momentum (BAM), small divergence, and high brilliance. In the first stage, a circularly polarized laser pulse with intensity of 1022 W/cm2 irradiates a micro-channel target, drags out electrons from the channel wall, and accelerates them to high energies via the longitudinal electric fields. During the process, the laser transfers its spin angular momentum (SAM) to the electrons’ orbital angular momentum (OAM). In the second stage, the drive pulse is reflected by the attached fan-foil and a vortex laser pulse is thus formed. In the third stage, the energetic electrons collide head-on with the reflected vortex pulse and transfer their AM to the γ-photons via nonlinear Compton scattering. Three-dimensional particle-in-cell simulations show that the peak brilliance of the γ-ray beam is $\sim 1{0}^{22}$ photons·s–1·mm–2·mrad–2 per 0.1% bandwidth at 1 MeV with a peak instantaneous power of 25 TW and averaged BAM of $1{0}^6\hslash$/photon. The AM conversion efficiency from laser to the γ-photons is unprecedentedly 0.67%.

Keywords

1 Introduction

Bright X/γ-ray sources have various applications in the laboratory astrophysics, nuclear photonics, ultra-high-density matter radiography, high-flux positron generation, and nuclear medical imaging[16]. Hard X/γ-rays are conventionally produced by large synchrotron facilities with peak brilliance in the range of $\sim 1{0}^{19}$–1024 photons·s–1·mm–2·mrad–2 per 0.1% bandwidth and photon energy ranging from several kiloelectronvolts (keV) to megaelectronvolts (MeV). However, the huge size and high cost of these large infrastructures mean that access to these sources is limited. Laser–plasma-based X/γ-photon sources have the advantages of compact size, relatively low cost, high beam brilliance, and photon energy, making them extremely attractive for potential applications, especially in astrophysics and high-energy physics[79]. In the past few years, significant progress has been made in experiments, to develop a table-top hard X/γ-ray source, allowing a peak brilliance of the same order of magnitude as the synchrotrons at photon energy between 20 and 150 keV[1012]. In numerical studies, many proposals based on petawatt-class (PW-class) laser pulse interaction with micro-wire[13] and channel[14], gas[10], near-critical-density plasma[1518], mass-limited foil and solid[19,20], have also been proposed to produce ultra-brilliant γ-rays with cutoff photon energy of several gigaelectronvolts and peak brilliance of several orders of magnitude higher than that of synchrotrons. However, owing to the high photon energy, short pulse duration, and small source size, it is very challenging to manipulate these γ-rays in a compact manner, e.g., the wave front, intensity distribution, and angular momentum (AM).

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Hao Zhang, Jie Zhao, Yanting Hu, Qianni Li, Yu Lu, Yue Cao, Debin Zou, Zhengming Sheng, Francesco Pegoraro, Paul McKenna, Fuqiu Shao, Tongpu Yu. Efficient bright γ-ray vortex emission from a laser-illuminated light-fan-in-channel target[J]. High Power Laser Science and Engineering, 2021, 9(3): 03000e43