Ultra high vacuum technology applied for the design of warm E.B.I.S. or E.B.I.T. ion sources

The important feature in the Electron Beam Ion Source (E.B.I.S.) or Electron Beam Ion Trap (E.B.I.T.) design is the low vacuum pressure (>10-9Pa) required in the main part of the source to obtain an intense highly charged ion beam. Until now, the best sources used cryogenic pumping which does, however, present drawbacks: formation of cryosorbats and an important cryogenic dead time prior to each intervention inside the source. The vacuum pumping technology applied on accelerators and storage rings such as MIMAS at the Saturne National Laboratory has been adopted, enabling the achievement of very low pressure. This technology uses different types of pumps such as the high compression turbo molecular pump and titanium sublimators. This paper reports the results achieved in an ion source prototype, where the pressure is lower than 8.1010 Pa and the main residual gas being hydrogen. The vacuum chamber is made of a stainless steel vessel in which the electron gun cathode is heated to nominal operating temperature (1 100 deg C). A gas can be injected (Argon 2.6 10-8 Pa) over a period of several days to create the working ions. After injection the initial pressure and the quality of the residual gas are recovered within a few hours. (authors). 3 refs., 4 figs