Gauteng LABS – Accelerator Mass Spectrometry
ACCELERATOR MASS SPECTROMETRY
AMS counts atoms instead of counting decays. This simple, yet effective, technique will enable large-scale, rapid and sensitive analysis of samples across and involving a wide range of disciplines. It is anticipated that all South African universities will participate in this state-of-the-art facility, which will be the only one of its kind on the African continent.
AMS at iThemba LABS (Gauteng).
Significant contributions will be made to areas such as Biomedicine, Diagnostics, Agriculture and Minerals, Materials and Chemicals. AMS can detect contaminants at parts per billion in high-purity electronics components in fields such as Materials Characterisation and Trace Element Detection.
The financial and concomitant research benefits that will accrue from AMS by involving pharmaceutical companies and research institutes are evident.
The high throughput of samples and the accuracy of the results obtained by AMS will prove to be of increasing importance in agriculture and hydrology. Specifics here may include groundwater chemistry, the residence time of carbon in the soil reservoir and in the oceans, thus improving strategic planning of soil and water management in Southern Africa.
AMS will provide a vital and cost-effective role in determining the economics of the geology and mineralogy in Africa, especially considering the sheer scale and variety of the mineral wealth of the continent.
Expected Outcomes by applying AMS with particular relevance to Southern Africa.
Research in global and regional climate change based on long lived cosmogenic isotopes in the atmosphere such as 14C, 10Be and 36Cl. These isotopes enable studies of long term climatic change and geologic processes and make it possible to establish the ocean circulation patterns and rates which are strongly coupled to climate, such as the El Niño effect.
Characterisation of anthropogenic and fossils sources of atmospheric pollution.
AMS measurements of radiocarbon (14C) can determine the age of sources of carbon-containing atmospheric trace gases. In this way it can resolve the controversy of how much of the atmospheric content for some of these gases is derived from human combustion of fossil fuels as opposed to natural sources (wood/plant burning sources).
Characterisation of Regional Groundwater Systems.
The advantage of AMS for Isotope Hydrology would lie principally in the ability to measure very small samples of 14C and in the long lived or low level isotopes such as 36Cl.
Anthropology, Archaeology, History and Preservation Technology.
AMS has made significant contributions in dating, precisely the transition to the cultivation of crops, the age of stone tools, prehistoric rock painting, and other events and artefacts of historical importance. The requirement for microgram sized samples makes the technique non-destructive and enables to be used in sensitive artefacts such as paintings and historic pottery of the indigenous San people. San paintings are among the very few well preserved artefacts from hunter-gatherer societies, and the ability to date possible small amounts of organic carbon will give unique insight in migration periods of the San, as well as the Bantu who migrated from Central West Africa.
AMS in Biomedical Dosimetry.
The high sensitivity of the technique for long-lived isotopes makes it possible to measure from one to five orders of magnitude increases in the sensitivity of DNA adduct detection. This allows the testing of assumptions about the physiological response to small doses of carcinogens to specific nucleotides that can be recognised at ng/kg (nanograms/kilogram) exposure levels. Experiments at Lawrence Livermore National Laboratory have demonstrated the usefulness of AMS in pharmacokinetic studies and in highly specific radio-immunoassays. Biomedical-AMS is one of the fastest growing applications of the AMS technology.
Qualifying Therapeutic Drugs.
With its ability to detect mutagenic chemicals attached to DNA, the use of AMS in eliminating unsuitable drug candidates early in the process can have enormous research and financial benefits to pharmaceutical studies.
Research in Geosciences.
The high sensitivity of AMS makes it possible to use 10Be measurements in establishing erosion rates of rocks, dating of young volcanic flows, marine and lake sedimentation rates, which constitute a significant part of the research in Southern Africa. 10Be, 14C and 36Cl are also important for polar ice and meteorite research in the arctic regions. In the sphere of Geosciences, AMS applications have hitherto concentrated on the use of cosmogenic isotopes and rare in-situ produced isotopes for geomorphological and geophysical studies. Special features of AMS lend themselves to more general applications to other isotopes and geochronological systems.
Ultra-sensitive Trace Element AMS (TEAMS) Applications in Materials Science.
TEAMS has already been established in certain laboratories overseas for applications in the semiconducting industry. Here, TEAMS will be applied in certain studies related to dopants and impurities in diamond.
Judging from overseas labs which have added AMS capability to their Tandem Accelerators, a large number of postgraduate students from different scientific disciplines is expected to use the AMS facility at iThemba (Gauteng) in order to obtain valuable data for their studies.
Undergraduate and Technical/Diploma Students.
Many such students will be used in, for example, the Environmental Isotope Laboratory as part of their ongoing training. Engineering students, as part of their normal familiarization and techniques training, can be used directly in the AMS facility, and in all aspects relating to the normal operation of the Tandem Accelerator.
Sample Preparation Laboratory .
The quality of AMS measurements depends enormously on the sample chemistry. Particular processes have to be followed in order to convert the “raw” sample to a final suitable cathode mounted in the ion source of the accelerator. Such processes requires a suitable and modern sample preparation laboratory. Its size is determined by the number of samples analysed per year and the type of isotopes to be measured. For radiocarbon (14C) samples, the present decay counting sample preparation facility within the Environmental Isotope Laboratory should be modified and extended to accommodate the graphitization stage.
It is planned to enhance and upgrade the facilities of the Environmental Isotope Laboratory. Please see the section relating to this facility.
The sample preparation for other isotopes such as tritium, 10Be, 26Al, 36Cl, 41Ca and 129I require different methods of sample preparation. In the case of isotopes not yet established as measurable by other laboratories, one would have to develop new methods of sample preparation. These often require a considerable amount of research and development and the availability of a well established chemistry and sample preparation laboratory.