INFN-LNF Laboratori Nazionali di Frascati
The SPARC_LAB research team at the Frascati National Laboratory has recently demonstrated that the plasma-based acceleration technique allows to obtain an high-quality particle beam, comparable to the beams produced in traditional accelerators.
The results of this study have been published on Nature and pave the way to the realization of compact and portable particle accelerators, to be used not only in the research context but also in the medical and industrial sectors.
The possibility to accelerate electron beams to ultra-relativistic velocities over short distances by using plasma-based technology holds the potential for a revolution in the field of particle accelerators.
Despite the high acceleration gradients produced in a plasma (up to three orders of magnitude higher than the conventional machines based on RF technology), their use has been limited due to the low quality of the beam produced. The study reported on Nature carried out at SPARC_LAB showed that, for the first time, it is possibile to use an high quality beam accelerated by a plasma wave to generate coherent radiation in a Free Electron Laser (FEL) in the infrared range.
The results was obtained injecting two electron bunches (few tens of microns sized) in the plasma contained in a 3 cm long capillary. Firstly it is necessary to create the plasma by ionizing hydrogen gas with a high voltage discharge. Then, the two electron bunches are injected. The first bunch (driver) serves to excite the plasma accelerating waves that are exploited by the second bunch (witness) that is accelerated. The high quality of the witness at the entrance of the plasma is preserved along the acceleration process and, in addition to the high current, is capable of driving a free-electron laser (FEL) by generating coherent light pulses. The experiment conducted at SPARC_LAB allowed the light pulses to reach the energy of 30 nJ.
“The plasma acceleration technique will allow to realize accelerators in small places, limiting the production costs of the hosting infrastructures and making this technology more accessible and available also for medical applications in equipped hospitals, and especially in underground facilities as the ones necessary for accelerators in High Energy physics”, says Riccardo Pompili, Principal Investigator of the experiment carried out at SPARC_LAB.
“This result has not only a great scientific relevance per se, but it represents also a milestone towards the realization of the are project EUPRAXIA, that yearns for the construction of the first research infrastructure addressed to users, based on plasma acceleration”, explains Massimo Ferrario, responsible of the EUPRAXIA@SPARC_LAB project, financed also by a contribution of the Italian Minister of Research and University (MUR) and recently included in the ESFRI roadmap, the strategic forum for research infrastructures.