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Neutral atom6/11/2023 Unaffected by electric or magnetic fields, these neutral atoms penetrate deeper in solids than electrons or ions and thereby create high-finesse microstructures for novel electronics and optical devices.In the 1910s, experiments with X rays led to this useful conclusion: the magnitude of the positive charge in the nucleus of every atom of a particular element is the same. With new-age technologies foraying into probing extremes of matter, accelerated mega-electron-volt neutral atoms have a distinct advantage over their charged counterparts. Our experiments show that under optimum conditions, the conversion of ions to neutral atoms can be nearly 100%, thereby resulting in the first compact table-top laser-based MeV neutral atom source. Hence, in summary, the modus operandi of the acceleration mechanism may be envisaged in a scheme comprising laser-ionization, followed by acceleration of the ions and their subsequent neutralization via electron-recapture. A highly effective electron transfer happens from the Rydberg-excited cluster to the energetic ion, thereby engendering highly energetic neutral atoms. This spews out mega-electron-volt ions, which then traverse through the sheath of Rydberg-excited clusters surrounding the laser-focus. On the other hand, the clusters which have been ionized by the laser (thereby generating the swarm of electrons) are reduced to assemblages of ions, bursting with their nascent charge, and exploding under their own self-charge Coulomb repulsion. The swarm of electrons released from this laser-excited region loosely attach themselves to the clusters in the vicinity, forming a halo around them, and giving rise to so-called Rydberg-excited clusters. The interaction of an intense (~10 16 W/cm 2) laser pulse with an argon cluster can remove as many as eight electrons from each atom in the cluster, which typically comprises about 40,000 atoms on an average. Inert gases like argon can conglomerate to clusters, each cluster being an aggregate of a few tens of thousands of atoms. DOI: 10.1038/NPHYS2526) provide a crucial breakthrough in the generation of accelerated neutral atoms, with energies as large as a mega-electron volt (MeV), nearly six orders of magnitude higher compared to previous results. Maher-McWilliams et al., Nature Photonics 6, 386 (2012)) have reported milli-electron-volt (meV) neutral atoms by various laser-induced acceleration mechanisms. Consequently, all the aforesaid acceleration schemes are rendered completely ineffective in the face of the challenging prospect of accelerating a neutral particle, which does not respond to electric or magnetic fields precisely the reason why neutral particles can often penetrate deeper, into regions which are otherwise inaccessible to charged particles. However diverse the acceleration scheme, they are all based on accelerating a charged particle an electron, proton or an ion by an electric field. Thus, while it is the electric field in a radiofrequency (RF) cavity in a conventional accelerator, in TNSA it is the electrostatic sheath field produced at the target rear, whereas in an electron accelerator, it is the wakefield in the plasma wave travelling in the wake of the laser pulse. The basic underlying physics of accelerating a particle, however, hinges on an accelerating electric field, both in conventional as well as in laser-based particle accelerators, occasionally coupled with magnetic fields that steer the particle beam. 85, 2945 (2000)) energies which sound mundane in comparison with conventionally accelerated particle energies, until one realizes that they have been achieved on compact inexpensive table-top accelerators, as opposed to kilometer-long tunnels across nations. 2, 696 (2006)) in a wakefield-accelerator as well as proton energies of 60 mega-electron-volts (MeV) in a so-called target-normal sheath acceleration (TNSA) scheme (R. Laser-based plasma accelerators, on the contrary, follow radically different acceleration schemes and can produce GeV electron bunches (W. The recent hysteria, deservedly so, on the landmark historic discovery of a new Higgs-boson-like particle of mass 125 giga-electron-volts (GeV) at the Large Hadron Collider (LHC) in CERN probably highlights the gargantuan heights scaled by conventional particle accelerators in recent times, routinely accelerating particles to even tera-electron-volt (TeV) energies. Our recent studies provide a crucial breakthrough in the generation of accelerated neutral atoms, with energies as large as an MeV, as a result of the interaction of intense lasers with nanoclusters. NEUTRAL-ATOM ACCELERATORS – SCALING MEV ENERGIES!Īccelerating neutral atoms, contrary to laser-based as well as conventional particle accelerators, is a formidable feat, given the inert, neutral response of these atoms to accelerating fields.
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