Counterstreaming Electron Beam Profile and Position Monitor

Individual profiles and positions of two counterstreaming 10 MeV electron beams have been measured using the strongly forward directed bremsstrahlung radiation produced when a small fraction of the beam impinges on a tantalum foil. The 0.02 mm wide foil is driven through the electron beams by an external motor connected to the foil by a linear vacuum feedthrough. Bremsstrahlung radiation is detected by a series of ordinary semiconductor diodes spaced around the circumference of the beam vacuum pipe in two planes. The planes are on opposite sides of the foil and are equidistant and parallel to the plane of motion of the foil. The diodes produce output currents proportional to the bremsstrahlung radiation intensity and require no biasing voltages. Design and operational features of the beam monitor for electron beams up to 100 MeV are described. Measurements on counterstreaming 10 MeV pulsed electron beams are presented. Spatial resolutions of 0.3 mm are easily discernable.