Time-resolved observation of ultrahigh intensity laser-produced electron jets propagating through transparent solid targets

We report on shadowgraphic measurements showing the first space- and time-resolved snapshots of ultraintense laser pulse-generated fast electrons propagating through a solid target. A remarkable result is the formation of highly collimated jets (<20-mu m) traveling at the velocity of light and extending up to 1 mm. This feature clearly indicates a magnetically assisted regime of electron transport, of critical interest for the fast ignitor scheme. Along with these jets, we detect a slower (approximate to c/2) and broader (up to 1 mm) ionization front consistent with collisional hot electron energy transport.