Collimated gamma ray pulses generated by high intensity laser
Collimated gamma ray pulses generated by high intensity laser lead image
The ability to generate collimated gamma ray pulses with high conversion-efficiency has attracted attention due to a number of potential applications in laboratory astrophysics, medicine, materials science and other fields. In Applied Physics Letters, investigators present a scheme to produce such pulses by irradiating a narrow tube target with an ultrahigh intensity laser.
The study utilized an analytical model of electron dynamics in laser fields inside a tube-shaped target. The authors solved the relativistic Newton-Lorentz equation governing electron motion analytically. They then carried out two-dimensional particle-in-cell (PIC) simulations of electron acceleration and gamma ray emission in the narrow tube target using the software EPOCH.
The results showed that energetic electrons are efficiently accelerated by the longitudinal electric field and radiate strongly near the inner boundary of the tube, producing a highly collimated gamma ray pulse. The brilliance of the pulse, as calculated from PIC simulations, was found to be two orders of magnitude higher than previously reported. This was due to a high conversion efficiency, up to 18 percent, and a small divergence angle, less than three degrees. In addition, the investigators found that both brilliance and collimation increase with laser intensity, rather than decrease as reported in earlier work by other investigators.
The investigators point out that thicker tube walls can be used for generating highly collimated gamma ray pulses, since only the inner tube diameter affects the results. The proposed scheme can pave the way to future applications of high-brilliance gamma ray pulses produced by lasers.
Source: “The generation of collimated γ-ray pulse from the interaction between 10 PW laser and a narrow tube target,” by J. Q. Yu, R. H. Hu, Z. Gong, A. Ting, Z. Najmudin, D. Wu, H. Y. Lu, W. J. Ma, and X. Q. Yan, Applied Physics Letters (2018). The article can be accessed at https://doi.org/10.1063/1.5030942 .
