E179: A 1.4 meter-long plasma wakefield acceleration experiment

Summary form only given. In the E-157 plasma wakefield experiment conducted at SLAC, a 30 GeV, 2 ps (/spl sigma//sub z/=0.6 mm) electron bunch is sent in a 1.4 m long lithium plasma with a density n/sub c/ in the 1-4/spl times/10/sup 14/ cm/sup -3/ range. The electron bunch density is larger than the plasma density, and the bunch completely expels the plasma electrons (blow-out regime), creating a focusing ion channel. When the plasma electrons rush back into the ion channel, they give rise to a large longitudinal accelerating gradient of the order of 1 GeV/m (with n/sub c/=2.1/spl times/10/sup 14/ cm/sup -3/, and 4/spl times/10/sup 10/ e per bunch). The electrons in the tail of the bunch (/spl sigma//sub z//spl ap//spl lambda//sub p/ the plasma wavelength) experience the accelerating gradient and gain energy. The plasma source consists of a heat-pipe oven producing a 1.4 m long lithium neutral column with a density n/sub 0/ in the 2-5/spl times/10/sup 15/ cm/sup -3/ range. The vapor column length is estimated from temperature profile measurements, and the neutral column density length product (n/sub 0/L) is measured using white light absorption, hook method, and uv absorption.