Collaboration with National Physical Laboratory and the University of Birmingham

Atomic clocks are an underpinning technology amongst a surprising amount of day-to-day applications, from navigation and communications, to finance and the national grid. Today, some of the leading atomic clocks are based on optically trapped arrays of Strontium atoms which have been cooled to near absolute zero temperatures. The current record for accuracy is on the order of a few parts in 10^-19 of a second. This is equivalent to 100 milliseconds inaccuracy over the lifetime of the universe! We are nearing the stage where we will redefine the second from the current caesium standard, and the ‘strontium lattice clock’ is a strong contender.

One of major technological challenges in building a strontium lattice clock is the source of strontium itself. One requires these atoms in a vapour phase – free floating in an ultra-high vacuum chamber – but the low vapour pressure of Strontium means that a hot oven is required. This has several disadvantages: the hotter the atom source, the more difficult to trap and cool the atoms, and so one has a lower signal to noise; a lengthy ‘Zeeman slower’ is required to collect sufficient atoms which greatly complicated the clock and results in spurious magnetic fields; the ‘clock transition’ is very sensitive to blackbody energy shifts induced by hot nearly objects thus limiting the clock accuracy. There is a significant interest in making atomic clocks as small and portable as possible, particularly in the area of navigation.

This PhD project aims to look at alternative strontium vapour sources which avoid the use of a hot oven and complex Zeeman slower. An intriguing effect has recently been demonstrated where strontium oxide produced pure strontium oxide under weak UV laser irradiation. The exact mechanism and optimum arrangement is still unknown, and a thorough exploration of the parameter space is required. The same effect has been seen in Ytterbium oxides, which is another contender for the redefinition of a second, albeit in an ion trap. Therefore, part of this project is to thoroughly explore and understand this mechanism. The second approach is to adapt the new voltage-controlled alkali source developed at NIST, for alkaline earth atoms. This exciting device allows one to both source and sink atoms in a highly controllable manner which is very advantageous for future atomic clocks. As part of the project, the student will also be involved in the development of alkali and alkaline-earth reference cells using microfabrication techniques.

The candidate will have a strong background in atomic and optical physics, and ideally have some experience in inorganic chemistry and surface science.