Ultrafast gamma-ray line emission driven by laser-accelerated ion beams

Yong Yu,Baifei Shen

doi:10.1063/1.5046174

Abstract

The Monte Carlo code Geant4 is used to demonstrate ultrafast gamma-ray line emission from the 12C +12C reaction driven by laser-accelerated ion beams. With carbon ions of the order of tens of MeV accelerated by laser-bombarding the carbon target, characteristic gamma-ray line emission is generated with durations as short as picoseconds through ultrafast gamma-ray transitions. Because the relative bandwidths of such gamma-ray lines can be reduced to less than 1% and the yield rate of gamma photons is around 10−5 for an incident carbon ion, this gamma-ray line emission can be used as an ultrafast monoenergetic gamma-ray source with a flux of 1.2 × 106 photons/J into 4π. We also show that the bremsstrahlung background induced by electrons accelerated simultaneously with the carbon ions can be mitigated by choosing a proper detection angle and an optimized target thickness.

Highlights

As important compact sources of gamma rays, laser-driven gamma-ray sources have attracted much attention because of their wide applications, such as the radiography of dense objects,[1] gammaray beam transmutation,[2,3] and nondestructively measuring and assaying nuclear material by nuclear resonance fluorescence[4,5] for nuclear security and safeguards.[6]
The full width at half maximum (FWHM) for 440 keV is only 4 keV when we integrate from θ = 80◦ to 100◦, and we reduce the relative bandwidth to 1%
The yield rates of gamma photons for 440 keV and 1,636 keV are around 10−5 per carbon ion, which can be calculated from the gamma spectrum (e.g., Fig. 3(b))

Summary

INTRODUCTION

As important compact sources of gamma rays, laser-driven gamma-ray sources have attracted much attention because of their wide applications, such as the radiography of dense objects,[1] gammaray beam transmutation,[2,3] and nondestructively measuring and assaying nuclear material by nuclear resonance fluorescence[4,5] for nuclear security and safeguards.[6]. Because gamma-ray transitions take place mainly in excited nuclides with half-lives as short as nanoseconds or even picoseconds, we propose using laser-accelerated ultrashort (picosecond) carbon-ion beams to generate ultrafast gamma-ray line emission with pulse width of several picoseconds. These results show that if we use a monoenergetic (quasi-monoenergetic) ion source,[21,32] the gamma line emission is purer and more gamma photons are generated because the nuclear levels can be excited more selectively.

22 Nam 23 Nam 22 Nam 20 Nem 23 Nam

ELECTRON-INDUCED BREMSSTRAHLUNG BACKGROUND

Findings

CONCLUSIONS