Grant: Research Tools and Instruments - Category 1 (<$150,000)

Neon Moderator for an intense positron source Antihydrogen is the simplest antimatter atom and consists of a positron (the antiparticle equivalent of an electron) orbiting about an antiproton. In recent years, antihydrogen atoms have been constructed at CERN by combining trapped antiprotons with trapped positrons. The goal of this research is to precisely study antihydrogen atoms and compare their properties to those of regular hydrogen, thus comparing the properties of antimatter to those of matter. Because of a fundamental symmetry of physics (CPT), it might be expected that the properties will be exactly identical and the comparison will therefore test CPT symmetry. The monies requested are to fund an improved method for collecting positrons. The positrons are produced at very high energy by a sodium-22 radioactive source. A moderator is used to lower their energy by having a small fraction of the positrons thermalize within a solid. Currently we are using a thin crystal of tungsten for this purpose, but the number of positrons available to our experiment could be improved by a factor of 100 if we were to use a solid neon moderator instead. The factor of 100 results from the 10 times higher positron moderation efficiency of solid neon combined with the fact that the resulting higher density allows for better compression of the positron plasma and this compression leads to a factor of 10 higher efficiency in transporting the positrons to the location where the antiprotons are trapped. The grant proposal is for the purchase of a system which will allow us to produce and sustain a solid neon moderator. This moderator must be constructed and maintained at temperatures below 24 Kelvin (-250 degrees Celsius) and require a precision-controlled ultrapure gas system within a high-vacuum apparatus.