Energetic neutral atom Energetic neutral atom Energetic neutral atom (ENA) imaging, often described as "seeing with atoms", is a technology used to create global images of otherwise invisible phenomena in the magnetospheres of planets and throughout the heliosphere, even to its outer boundary. This constitutes the far-flung edge of the solar system. The solar wind consists of ripped-apart atoms (called plasma) flying out of the Sun. This is mostly hydrogen, that is, bare electrons and protons, with a little bit of other kinds of nuclei, mostly helium. The space between solar systems is similar, but they come from other stars in our galaxy.
AWAKE bunch in the wakefield is thus crucial, since only a fraction (1/4th) of the wakefield is both focused and accelerated, which is needed for the trapping and the acceleration of the electrons. AWAKE is the first plasma wakefield experiment using a bunch of protons as a driver. Protons, as e.g. the protons form the CERN SPS, can carry a large amount of energy (~ 400 GeV). Therefore, they can produce wakefields in a plasma for much longer distances than a laser pulse or electron bunch as a driver due to energy depletion. A plasma can be seen as an ensemble