Collective Ion Acceleration Controlled by a Gas Gradient

Energetic alpha particles are observed when an intense relativistic electron beam is injected into a decreasing pressure profile of helium gas. In a 7 kG external magnetic field up to 1010 9 MeV alpha particles are detected on cellulose nitrate. By viewing the electron beam as an expanding "gas" of reflecting electrons the corresponding ion distribution is calculated and compared to the measured distribution. Good agreement in these results supports the reflecting beam model of Ryutov.