Single electron beams from the LEP pre-injector

At the request of the L3 collaboration (one of the LEP (Linear Electron-Positron collider) experiments) a new facility was built to close to the Electron Positron Accumulator (EPA) to provide a single electron per beam pulse at an energy which can be selected between 180 MeV and 500 MeV. The intensity of the ejected electron beam is reduced by changing the gun parameters and by adjusting the aperture of the slits in the linac. The energy is defined by letting the beam do 1^1/4 turn in the EPA. The energy spread is limited to ±0.5×10^-3 by reducing the slits aperture in the LIL/EPA transfer line. A new transfer line was built to transport the beam from the EPA ejection septum to the detector test stand. The facility was then used to test the response of the L3 electromagnetic calorimeter composed of bismuth-germanium-oxide crystals in the 100-MeV range