Studies of the electron beam for the Fermilab electron cooling experiment

The electron beam for the Fermilab Electron Cooling Experiment provides a cold (Tsub(e) approximately 1 eV) D.C. electron beam with 110 kV, 26A. Stable operation has been achieved up to 70 kV, 6A. A new mechanism for efficient beam collection and energy recovery is described. The beam is decelerated nearly to rest before entering the collector geometry. Providing the electric and magnetic fields obey several conditions in this region, residual gas ions trap stably on the space charge equipotentials, permit deceleration nearly to rest in vacuo, and suppress backscatter electrons from the collector surface. In this way current losses can be reduced to approximately 2 x 10-4, while recovering approximately 95% of the beam power. (Auth.)