Development of a high current H- source for ESS

For the European Spallation Source (ESS), a volume source based on the HIEFS (high efficiency source) is being developed. The source will be optimized to produce high current densities in pulsed operation. A pulse generator delivering 1 to 1.5 ms pulses was installed. Furthermore, cesium was supplied to the plasma generator from an external oven. The cesium injection was optimized for a low e/H- ratio and a high current. We obtained a current density of 70 mA/cm2. This way, with an aperture radius of 4.25 mm, an H- current of 40 mA was extracted at an extraction voltage of 22 kV. After a description of the source and the experimental setup, measurements of the beam current density and the e/H- ratio will be presented in this paper