Strong evidence has been gathered demonstrating that the majority of the mass in the Universe is composed of non-luminous, non-baryonic matter, called Dark Matter. The search for Dark Matter is one of the major quests in physics. It is invoked to explain gravitational effects in the Universe, such as the motion of stars in galaxies. It is expected to be 5 times more abundant than standard matter, but its interaction with normal matter is extremely weak. The direct detection of Dark Matter is therefore extremely difficult.
The SABRE (Sodium iodide with Active Background REjection) experiments aim to detect an annual rate modulation from dark matter interactions in ultra-high purity NaI(Tl) crystals. The SABRE south experiment will be located at the Stawell Underground Physics Laboratory (SUPL), Australia, and will be the first deep underground laboratory in the Southern Hemisphere, due to be completed in early 2022. SABRE South is designed to disentangle seasonal or site-related effects from the dark matter-like modulated signal first observed by DAMA/LIBRA in the Northern Hemisphere using an active veto and muon detection system. It is a partner to the SABRE North effort at the Laboratori Nazionali del Gran Sasso (LNGS).
Radioimpurities such as 40K, 238U, 210Pb and 232Th, either intrinsic to the detector material or surface contamination, provide a fundamental limit to the sensitivity of SABRE. Therefore, it is crucial to characterise and minimise this background to allow unambiguous detection of the signals that will indicate detection of dark matter particles.
The student will participate in the chemical extraction, Accelerator Mass Spectrometry (AMS) measurements to determine the ultra-low radioactivity levels and analysis of potential detector materials. AMS is a single atom counting technique that measures extraordinarily low concentrations of rare (radioactive) isotopes of natural or anthropogenic origin. It will involve the use of Australia's 15-million-volt accelerator at ANU as well as a complementary accelerator at ANSTO in Sydney.