High bandwidth power supplies for optical pumping of francium atoms for atomic parity violation studies

点击翻译按钮获取中文摘要

The fundamental forces of nature are one of the fascinating subjects that can be studied at the ISAC radioactive beam facility at TRIUMF, Canada's national laboratory for nuclear and particle physics. In particular, the weak force, causing the beta-decay of nuclei, is unique in exhibiting the phenomenon of parity-violation: the mirror images of physical processes mediated by the weak force are not observed in nature. ISAC offers the possibility to study atomic parity-violation in francium (Fr), an element combining a very heavy nucleus (Z=87) with the simple, essentially hydrogenlike, valence structure of an alkali. Fr nuclei are the least stable among the first 103 elements in the periodic table, the longest-lived isotope decays in only 23 minutes. To make optimum use of the minute sample, the Fr atoms are slowed down with laser light and captured into a `magneto-optical' laser trap, suspended in free space at temperatures millions of times colder than room temperature. We have established a francium trapping facility at ISAC; in collaboration with researchers from the United States and Mexico, we are now using this francium source to carry out a series of precision experiments using laser and microwave spectroscopy. Working our way towards atomic parity violation measurements, we are exciting an exceedingly faint electronic transition, 7s to 8s, and measure its property. For these measurements, the atoms have to be optically pumped with laser light into a quantum state that has the atom's magnetic moment aligned with an externally applied magnetic field. Optical pumping is not compatible with the laser trapping setup, and we have to rapidly, on the order of a millisecond, switch back and forth between magnetic field configurations suitable for laser trapping and optical pumping. For this purpose we require 3 high-current power supplies that can be switched on and off at the hundred microsecond scale to control a three-dimensional coil configuration. With this equipment in place, we can push towards an atomic parity violation experiment in francium.