Researchers at Jet Propulsion Laboratory have come up with a novel approach to the simplification of the 194-nm light source and optical guidance in mercury trapped ion spectroscopy research. Mercury plasma is generated in a capillary tube with a diameter of a few hundred microns (in contrast to current lamp bulbs with a diameter of 13 mm). The deep ultraviolet (DUV) light from the plasma can be guided directly to the ions held in an ion trap in a vacuum system via a piece of DUV fiber that is fused at the end of the capillary tube.
Argon and isotopically enriched mercury (202Hg) are prepared and sealed in a piece of capillary tube with a diameter of a few hundred microns. The mercury plasma can be generated inside the tube with externally applied RF or microwave power. Coils or surface strip electrodes can be used as a capacitive resonator to sustain the plasma. One end of the tube is sealed, and the other end of the tube is fused with a piece of large-core DUV step-index fiber, where the DUV radiation from the plasma is collected. A gradient-index lens can be manufactured at the output tip of the fiber to deliver the condensed light to the ions. The fiber output can be brought close to the ion trap assembly and coupled through a UV window or fiber feed-through assembly. Alternatively, the miniature plasma and delivery assembly could be placed entirely in the ion trap vacuum assembly.