First beam measurements on the vessel for extraction and source plasma analyses (VESPA) at the Rutherford Appleton Laboratory (RAL)

In order to facilitate the testing of advanced H⁻ ion sources for the ISIS and Front End Test Stand (FETS) facilities at the Rutherford Appleton Laboratory (RAL), a Vessel for Extraction and Source Plasma Analyses (VESPA) has been constructed. This will perform the first detailed plasma measurements on the ISIS Penning-type H⁻ ion source using emission spectroscopic techniques. In addition, the 30-year-old extraction optics are re-designed from the ground up in order to fully transport the beam. Using multiple beam and plasma diagnostics devices, the ultimate aim is improve H⁻ production efficiency and subsequent transport for either long-term ISIS user operations or high power FETS requirements. The VESPA will also accommodate and test a new scaled-up Penning H⁻ source design. This paper details the VESPA design, construction and commissioning, as well as initial beam and spectroscopy results.