Grant: Subatomic Physics Envelope - Research Tools and Instruments

The weak interaction has small effects in atoms, and can be separated from the much stronger electromagnetic interaction by its violation of parity (`mirror') symmetry. These effects are largest in atoms with large atomic number Z, which enhances the degree of overlap of the atomic electrons with the nucleus. Francium is the highest-Z alkali element, so of very heavy atoms its atomic structure-- a single electron outside a nobel gas core-- can be most easily understood. We are building a laser trap for francium atoms at TRIUMF to pursue these experiments. The results would be a probe of other parity-violating interactions besides the standard model ones, both between the electrons and quarks and between protons and neutrons. We will also study the distribution of nuclear magnetism in francium isotopes. The wavefunctions of the single electron's orbitals are very well understood, so the energy change of the atom from their overlap with the magnetic distribution of the nucleus allows us to probe that distribution. This `hyperfine anomaly' will be studied with this trap by measuring accurate optical frequencies of the atomic transitions. The magnetism distribution is intrisically interesting for nuclear structure-- such as comparing nuclear spin isomers-- and also to provide information on the neutron distribution needed to interpret the weak interaction experiments. This request is for equipment to test the francium trap. An ion source of naturally-occuring rubidium atoms will simulate the radioactive francium ion beam from the ISAC faciilty. This ion source will let us test efficient trapping of the rubidium, to test our trap's readiness for francium. We need a naturally occuring element to make us independent of the oversubscribed radioactive beam (as well as the ISAC facility's stable ion source, which is usually on standby as a pilot beam for the accelerated radioactive beam). Other items include a residual gas analyzer to troubleshoot the ultra-high vacuum system, and vacuum hardware to place a 221Fr source (from 15 day half-life 225Ra) near the trap-loading apparatus to test it.