Generation of gamma-rays carrying orbital angular momentum by inverse Compton scattering

Date: 
Monday, October 30, 2017 - 4:00pm
Speaker: 
Yoshitaka Taira
Speaker's Institution: 
National Institute of Advanced Industrial Science and Technology (AIST)

After remarkable work conducted by L. Allen et al., which revealed that a Laguerre Gaussian (LG) laser mode carries orbital angular momentum (OAM) per photon [1], research on optical vortices using visible wavelength lasers has thrived and resulted in successful applications in various research fields. Moreover, vortex beams are not limited to visible light but have been generated in 10 keV X-rays, terahertz/radio waves, sub-MeV electron beams and cold neutrons.

Gamma-rays are an important tool for various research fields including solid-state physics using magnetic Compton scattering, positron production via pair production for a linear collider, nuclear physics, medical diagnostics and therapy, non-destructive inspection for industrial products and homeland security, and astrophysics. In this research, the final goal is to generate a gamma-ray vortex with energy in the MeV and GeV energy range, and to explore the application of gamma-ray vortices for nuclear physics research. If the OAM of gamma-rays is transferred to the angular momentum of quarks and gluons inside a proton, it may be a strong tool to measure the spin configuration of protons.

Gamma-ray vortices can be generated by inverse Compton scattering (ICS) [2]. In ICS, the laser photon is backscattered by the relativistic electron and its energy is increased to a high energy region. Gamma-rays with energy of tens of MeV can be generated by using a 1 GeV electron beam, and ~ GeV gamma-rays can be produced by a 10 GeV electron beam. In this seminar, I will present the OAM characteristics and the spatial intensity distribution of gamma-ray vortex beams generated by ICS. I also show an experimental plan to be conducted at accelerator and laser facilities.

 

References

[1] L. Allen, et al., “Orbital angular momentum of light and the transformation of Laguerre-Gaussian laser modes”, Phys. Rev. A, 45, 8185-8189, (1992).

[2] Y. Taira, T. Hayakawa, M. Katoh, “Gamma-ray vortices from nonlinear inverse Thomson scattering of circularly polarized light”, Scientific Reports, 7, 5018-1-9, (2017).