Generation of bright collimated vortex γ -ray via laser driven cone-fan target

Abstract

We use numerical simulations to demonstrate that a source of bright collimated vortex γ-ray with large orbital angular momentum and small divergence can be achieved by irradiating an intense circularly polarized laser on a cone-fan target. In the all-optical setup, electron beam of energy with hundreds of MeV and also vortex laser pulse are formed. A considerable fraction of angular momentum of laser is converted to electron beam and furthermore to final vortex γ-ray, which are roughly 27.8% and 3%, respectively. The conversion efficiency of energy from laser to them is around 41% and 3.8%. Moreover, comparative simulations for different inner sizes of the cone reveal that there exists an optimal size making the highest angular momentum of γ-ray photons. For simulations with different laser modes, the circularly polarized laser is more appropriate rather than the Laguerre–Gaussian one to generate vortex γ-ray.

Beijing Union Medical College Hospital and China’s Modern Medical Development

“…During the QED process, the TOAM of the STOV pulse remains almost unchanged (further explanation will be provided later), while that of the high-energy electron beam decreases to −1.33 × 10 18 ℏ, and that of the γ-photons and positrons reaches a maximum of −6.6 × 10 18 ℏ and −3.88 × 10 16 ℏ, respectively. The magnitude of particles TOAM is close to that of the longitudinal OAM [20,[22][23][24]. It is found that the change in the TOAM of high-energy electron beam, 6.64 × 10 18 ℏ, is consistent with the sum of the change in TOAM for γ-photons and pairs.…”

“…The SOV pulse [1] carrying longitudinal OAM parallel to the propagation direction has spiral wavefront phase of the form exp(iℓϕ), where ℓ represents the topological charge and ϕ is the azimuthal angle in the transverse plane. In past decades, researchers have extensively studied the generation of SOV pulse [2][3][4][5] and corresponding laser-matter interactions [6][7][8][9][10][11][12][13][14][15][16], especially the generation of γ-photons and pairs with longitudinal OAM [17][18][19][20][21][22][23][24][25][26][27][28][29]. Photons with OAM possesses an additional degree of freedom, which can expand the information capacity for optical communication [30], detect the inhomogeneities of small-scale interstellar medium, investigate OAM transfer in Kerr black holes [31,32] and so on.…”