Nuclear Physics

Modern accelerator mass spectrometry is a technique, which was born in nuclear physics laboratories in the late seventies of the last century. Many different research areas are touched by AMS, including archaeology, biological applications, atmospheric science, climatology, environmental science, hydrology, oceanography, glaciology, geological applications, nuclear forensics, ice core research, astrophysics, cosmic-rays, meteorites, nuclear physics and particle physics.

Applications

Half-live measurements. Half-life values are a fundamental nuclear physics quantity for dating applications where the decay in combination with its half-life value is used (note, the situation is different for ¹⁴C where an absolute time calibration independent of the half-life value has been established). The half-life is often also directly related to the isotope ratio of AMS standards, because the absolute number of the radionuclide in a sample can be deduced from its activity and the half-life value. New state-of-the-art AMS systems can produce highly precise data, e.g. ¹⁰Be/⁹Be ratios can be measured to better than 1%. Therefore, also the standards and consequently half-life values need to be known accurately. AMS had been used to measure half-lives of long-lived radionuclides, e.g. ³²Si, ⁴¹Ca, ⁶⁰Fe or ¹⁴⁶Sm.

Search for super-heavy elements in nature. The discovery of new elements (natural or artificially produced) has been a driving force in chemistry and physics. A run for the search for long-lived superheavy elements, possibly present in Nature since the formation of the solar system, started shortly after the hypothesis of an island of stability was suggested. Such species could be produced in nucleosynthesis by the rapid (r-) neutron capture process, as is the case in our present understanding for naturally occurring thorium and uranium. Similar to the search for interstellar longer-lived radionuclides in terrestrial archives (see Astrophysics and Meteorites), AMS is also used for direct search of such exotic nuclides. So far, no evidence exists and AMS measurements reached limits of abundance sensitivity in the 10^-12 to 10^-16 range relative to stable chemical homologues.

Nucleosynthesis in the laboratory—nuclear reaction studies. The knowledge of nuclear reaction cross sections has always been a prime goal of experimental nuclear physics. Nuclear data are of crucial importance in many applications - AMS represents a complementary approach for the precise measurements of cross sections (see also Astrophysics and Meteorites). Such applications include nuclear astrophysics (nucleosynthesis, cosmo-chemistry, meteorites), space technology, nuclear technology (nuclear fusion, nuclear fission and advanced reactor concepts) and medical applications (hadron therapy, radiation dose measurements). Furthermore, many applied AMS research areas rely on a proper understanding of the production of cosmogenic radionuclides in environmental, geological and extraterrestrial studies. Cross-sections and total induced activities are key parameters for safety and design analyses in advanced reactor concepts, such as fusion applications; i.e. accurate cross sections are crucial for calculating the production of long-lived activation products. In a fusion environment, particularly long-lived activation products may lead to significant long-term waste disposals and radiation damage.

This work relates to ITER, generation IV reactors, advanced reactor concepts, accelerator driven systems, and accelerators for medical applications. These research activities include a number of collaborations, e.g. with JRC/IRMM (Joint European Centre, Geel, Belgium), IAEA (Vienna), VERA (Univ. of Vienna) and ANSTO/Sydney; FRM II/TU Munich, ILL/Grenoble and Atominstitut – TU Vienna. We are linked to the IAEA through specialist’s activities within their nuclear data program. We are also part of the n_TOF collaboration through complementary measurements. n_TOF is a pulsed neutron source at CERN and designed to study neutron-induced interactions for neutron energies between meV to GeV. Research fields range from stellar nucleosynthesis to applications of nuclear technology, including the transmutation of nuclear waste and accelerator driven systems.

Radioimpurities in particle detectors for dark matter studies. AMS allows to study extremely low levels of radioactivity in ultra-high purity detector materials that need to be characterized for Dark Matter studies. We are part of the SABRE-South collaboration through the Australian Centre of Excellence for Dark Matter Particle Physics. SABRE (Sodium iodide with Active Background Rejection) is designed as a dark matter direct detection system to be installed in an underground laboratory in Australia.

Measurement of the neutrino mass. ¹⁶³Ho (T_1/2 = 4570 yr) is an interesting candidate for studying the mass scale of the electron neutrino. The main reason is its very low-energy electron-capture decay properties. Crucial for this study is the production of a sample containing ¹⁶³Ho of sufficient activity combined with high isotopic purity (see ECHO project). A major concern in this respect is the co-production of another long-lived isotope ^166mHo (T_1/2 = 1200 yr). AMS is used to verify the isotopic purity of ¹⁶³Ho and to quantify ^166mHo impurities.