A negative ion source for spectrometer calibration

Summary form only given. A negative ion source has been built to perform the primary calibrations of the electron spectrometers used on the Dual Axis Radiographic Hydrodynamic Test (DARHT) Facility at Los Alamos National Laboratory. The calibration requirement for the DARHT electron beam calls for an energy/momentum measurement of better than 1% absolute precision, and better than 0.5% relative precision. The negative ions of hydrogen and oxygen in the energy range of 2.5 keV to 50 keV. The ion source employs a ten-cusp "picket fence" magnetic configuration to confine the arc plasma. The source volume is approximately 0.3 liters, and arc powers of up to a kilowatt can be supported. A widening of one of the cusp gaps of the picket fence creates a barrier magnetic filter for radial beam extraction. The beam is extracted through a 1-mm aperture and is focused onto the entrance of the electron spectrometer by a three-element electrostatic accelerator stack. Result of source operation and electron spectrometer calibrations are presented.