First results of negative ion extraction with Cs for CRAFT prototype negative beam source

In order to understand the physics and pre-study the engineering issues for radio frequency(RF)negative beam source,a prototype source with a single driver and three-electrode accelerator was developed.Recently,the beam source was tested on the RF source test facility with RF plasma generation,negative ion production and extraction.A magnetic filter system and a Cs injection system were employed to enhance the negative ion production.As a result,a long pulse of 105 s negative ion beam with current density of 153 A m-2 was repeatedly extracted successfully.The source pressure is 0.6 Pa and the ratio of co-extracted electron and negative ion current is around0.3.The details of design and experimental results of beam source were shown in this letter.