Laser-driven generation of collimated ultra-relativistic positron beams

Abstract

Recent development in laser-based accelerators is finally offering the possibility of building metre-size electron-positron colliders with specifications comparable to those based on conventional acceleration techniques. Electron beams with energies exceeding the GeV have been experimentally demonstrated [1] with the possibility of approaching 100 GeV with the next generation of laser systems [2]. It is thus timely to study the feasibility of generating laser-driven positron beams with similar characteristics. Here we report on the experimental demonstration of table-top, all-optical generation of short (beam duration ~ 30fs), ultra-relativistic and collimated positron beams with peak energies approaching the GeV and divergencies in the mrad range. Plasma-based afterburners [3] to further accelerate these beams will also be discussed. The reported results represent the first experimental step towards the generation of metre-scale all-optical electron-positron colliders. The intrinsic synchronisation of these sources with a high-intensity laser will prove fundamental for the study of highly non-linear photon-lepton interactions and the testing of matter-antimatter symmetry in a highly non-linear regime.

Non-invasive characterisation of a laser-driven positron beam

“…The spectra resemble a relativistic Maxwellian distribution, with a maximum positron charge observed for a converter thickness of ∼ 9 mm, which corresponds to approximately 1.6 radiation lengths (L P b 5.6 mm). This observation is in good agreement with previous experimental results [5][6][7]9,10 . Numerical simulations indicate a temporal broadening of the positrons at 100 MeV of the order of 50 -100 fs, resulting in a peak positron current, at the rear surface of the converter, of the order of 1 A.…”

Nonlinear Breit–Wheeler pair creation with bremsstrahlungγrays

“…In particular, we will use our analytical results to show how the bremsstrahlung process may be optimized to produce the greatest number of Breit-Wheeler positrons. While these results are not dependent on the source of the electrons, one advantage of using LWFA is the small size and divergence of the accelerated electron beam [37]. As the γ ray beam inherits this size and divergence, this aids the achievement of good overlap with the second laser pulse, which must be focussed to a micron-sized focal spot to reach high intensity [14].…”

“…Relativistic beaming means that we expect the divergence of the bremsstrahlung photons to be inversely proportional to the Lorentz factor of the electron beam: for ℓ∼1, the root-mean-square (rms) angle is approximately [37] shows that this scaling works reasonably well. We now discuss the implications of these results for the generation of Breit-Wheeler pairs.…”

Coherent combs of antimatter from nonlinear electron-positron-pair creation

“…The following experiments reached positron energies up to 20MeV [7][8][9]. Most recently, positron beams with energies up to 120MeV have been produced in an all-optical setup experiment carried out at the Hercules laser facility [10,11].…”