RECENT DEVELOPMENTS AND PROPOSED APPLICATIONS OF THE ACCELERATORS AT ITHEMBA LABS

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1 RECENT DEVELOPMENTS AND PROPOSED APPLICATIONS OF THE ACCELERATORS AT ITHEMBA LABS J.L. Conradie, L.S. Anthony, F. Azaiez, S. Baard, F. Balzun, G. Badenhorst, R.A. Bark, A.H. Barnard, P. Beukes, J.I. Broodryk, J. Crafford, G. Darries, J.G. de Villiers, C. Doyle, H. du Plessis, W. Duckitt, D.T. Fourie, P.G. Gardiner, M.E. Hogan, I.H. Kohler, J. Lawrie, C. Lussi, N.R. Mantengu, S. Marsh, V. Mbele, R.H. McAlister, J.P. Mira, H.W. Mostert, C.B. Mtshali, A.S. Miller, S.M. Mullins, C. Naidoo, F. Nemulodi, M.M. Nkosi, O. Pekar, C.A. Pineda-Vargas, W.J. Przybylowicz, M. Sakildien, G.F. Steyn, N.P. Stodart, R.W. Thomae, M.J. van Niekerk, P.A. van Schalkwyk, T.P. Sechogela, S. Winkler and S. Woodborne ithemba LABS P.O. Box 722, Somerset West 7130, SouthAfrica ABSTRACT ithemba LABS hosts a number of research accelerators, comprising 2 solid-pole injector cyclotrons, a separated sector cyclotron (SSC) with a k-value of 200, a 6 MV tandem accelerator, a new 3 MV tandetron, and an 11 MeV PET cyclotron. The newly commissioned tandetron accelerator has replaced the 51-yearold 6 MV CN Van de Graaff accelerator for materials research with light and heavy ions. The 6 MV EN tandem accelerator was fully refurbished to be mainly used for accelerator mass spectrometry. A large component of this consists of isotope-based techniques used to establish the age of fossils and other objects. A new research programme for the SSC and its two injector cyclotrons has been proposed with the main focus on research with stable beams and the production of radioactive beams. This will include the construction of a new radioactive ion beam facility, making use of the ISOL production method. Within the new proposal the SSC will not be used for radioisotope production anymore, and will instead concentrate on subatomic physics. A new 70 MeV cyclotron will be acquired, dedicated to an envisaged increase in production of radioisotopes. The upgrades of the different accelerators and new applications will be discussed. KEYWORDS RIB, Radioisotope, Tandetron, AMS, Cyclotron 1. INTRODUCTION ithemba Laboratory for Accelerator Based Sciences (ithemba LABS) is a multi-disciplinary research centre, operated by the National Research Foundation (NRF) of South Africa. It provides accelerator facilities for research and training in the physical, biomedical, and material sciences, production of radioisotopes and radiopharmaceuticals for use in nuclear medicine, accelerator mass spectrometry services and treatment of cancer patients with energetic neutrons and protons. A number of different accelerators are operated: AccApp '17, Quebec, Canada, July 31-August 4,

2 - A k=200 separated sector cyclotron (SSC), equipped with two solid-pole injector cyclotrons (SPC1 and SPC2), is capable of providing high intensity 66 MeV proton beams, as well as lower intensity light ion, heavy ion, and polarized proton beams. - For most of the radioisotope production a 66 MeV proton beam from the SSC is used, but for the production of 18 F a dedicated 11 MeV cyclotron is employed. - For the past 51 years a 6 MV Van de Graaff (VDG) accelerator had been in operation at the current Materials Research Department (MRD) of ithemba LABS. This accelerator was recently decommissioned and it was replaced with a new 3 MV tandetron. - An accelerator mass spectrometry (AMS) facility based around a 6 MV EN tandem accelerator is used for determining relative abundances of isotopes, enabling various studies such as radiocarbon and cosmogenic dating of fossil finds. Future plans for ithemba LABS include the establishment of a facility currently known as the South African Isotope Facility (SAIF), which consists out of two parts: - Accelerator Centre for Exotic Isotopes (ACE Isotopes): A new radioisotope production facility based around a dedicated commercial 70 MeV cyclotron, will free the SSC from radioisotope and radiotherapy commitments enabling it to be dedicated to nuclear physics research. - Accelerator Centre for Exotic Beams (ACE Beams): A radioactive ion beam (RIB) facility for performing experiments on unstable beams. An isotope separation on-line (ISOL) method using the SSC as the first stage accelerator of stable proton beams is planned. A phased introduction of the RIB facility, starting with a low energy radioactive ion beam (LERIB) project is foreseen. 2. SEPARATED SECTOR CYCLOTRON FACILITY At the heart of the ithemba LABS accelerator complex is the variable-energy k=200 SSC. The k=8 SPC1, injector is used for the acceleration of protons and for light and heavy ions and polarized proton beams the k=11 SPC2 injector is employed. Protons accelerated to an energy of 66 MeV are utilized for the production of radioisotopes and for neutron therapy, whereas proton therapy is done at an energy of 200 MeV. Low intensity beams of light and heavy ions as well as polarized protons are provided for nuclear physics research. The SSC is primarily shared by four disciplines: nuclear physics research, radioisotope production, radiation biology research, and radiotherapy with protons and neutrons. The usual mode of operation is that nuclear physics research is conducted over weekends, while the rest of the week is scheduled for the production of both short- and long-lived radioisotopes as well as radiotherapy [1]. Nuclear physics research at ithemba LABS can be broadly divided into nuclear reaction mechanism and nuclear structure studies [2]. The main facilities operated by the Subatomic Physics Department are the AFRODITE gamma detector array, the only multi detector gamma-ray spectrometer in Africa, and the K600 magnetic spectrometer, one of only two high resolution magnetic spectrometers with the capability to measure ejectiles at zero degrees. In addition the near mono-energetic fast neutron beam facility is one of only a few in the world. Gamma ray nuclear spectroscopy using heavy ions is undertaken at the AFRODITE gamma-ray spectrometer array composed of 9 Compton suppressed clover detectors and 7 segmented planar Ge detectors. Recent investigations carried out using this detector include the study of chiral systems across the nuclear chart, the search for tetrahedral structures in the mass 160 and 230 regions, and a focus on excited 0 + states in the rare-earth region. The K600 spectrometer is used for experimental studies of high resolution knock-out reactions, namely (p, 2p) and (p, 2α); decays of giant resonances on (p, px) for x = n, p, α and studies of mixed symmetry states. AccApp '17, Quebec, Canada, July 31-August 4,

3 Proton beams from the SSC are also used to perform radiation biophysics research. This includes molecular radiation biology such as radiosensitivity of breast and cervical cancer, cellular radiation biology such as radiosensitivity and HIV status, automated radiation bio-dosimetry methods, Auger electron DNA damage and dose-volume effects of protons and neutrons. ithemba LABS is engaged in a number of NTeMBI projects, where a consortium of institutions is investigating aspects such as the early detection of cancer, hypoxic cell markers in cancer, dendrimers (large molecules) for detection and treatment of cancer with radioactive isotopes, and chemical dosimetry related to malaria prevention. 3. PLANNED RADIOACTIVE ION BEAM PRODUCTION Many beams desired for research consist of atoms that do not exist naturally and must be artificially created. At the planned ACE Beams facility such Radioactive Ion Beams (RIBs) will be produced using the Isotope Separation On-Line (ISOL) method, pioneered at the ISOLDE facility at CERN. In this method, a primary high-energy proton beam is used to bombard a uranium target, which is composed of uranium carbide discs. The target is consequently heated to vaporise the reaction products, which may then migrate to an ionsource where they are ionized and extracted. The extracted beam usually has an energy of a few tens of kev and it can be directed to an experimental station or charge bred for post-acceleration to high energies. A RIB test facility at ithemba LABS, presently under construction, will be upgraded to become the Low- Energy RIB facility (LERIB), the main ISOL bombardment target/ion-source for ACE Beams. LERIB is centered on a collaboration between ithemba LABS and INFN Legnaro the front-end or target/ionsource is identical to that of the SPES project [3]. As part of this collaboration, a high-power test of a SiC target has been successfully conducted, in which a 4 kw beam of 66 MeV protons was sustained on the SiC target for approximately one hour [4]. The test confirmed the ability of FEM calculations to simulate temperature and stress profiles of the production target under realistic conditions. For LERIB, an UC x target bombarded by a 100 µa, 66 MeV proton beam from the SSC will produce a fission rate of up to fissions per second. Expected yields from such a source for 50 µa beam current are shown in Fig. 1. The most intense (singly-charged) RIBs would be delivered at a rate of above ions/sec, or over 10 na of current. The physically interesting Sn isotope, 132 Sn is expected to have an intensity above 10 9 ions/sec. Figure. 1. Expected yields of singly-charged radioactive ions from the LERIB target-ion-source, when an UC x target is bombarded by 50 µa of 70 MeV protons. AccApp '17, Quebec, Canada, July 31-August 4,

4 Because LERIB will use the SSC as the driver accelerator, ACE Beams will require a new post-accelerator to produce beams with sufficient energy to induce nuclear reactions. This is expected to be a LINAC in order to optimize transport efficiency. Prior to injection into the LINAC, beams from LERIB will be cooled, mass selected with a high-resolution mass-separator and charge bred for post-acceleration. Two types of charge breeders are envisaged an ECR ion source and an electron string ion source (ESIS), developed at the Joint Institute of Nuclear Research, Russia [5]. The latter has the advantage for the less intense species, of delivering more pure beams and better concentrating the ions into a given charge state. Post-accelerated energies will initially be approximately 5 MeV/A. Beta-decay tape stations are presently under construction and will be equipped with clover detectors from the AFRODITE array, LaBr 3(Ce) detectors for fast timing and an electron spectrometer for conversion electron spectroscopy. The first beams from the LERIB facility, indicated in light-blue in Fig. 2, are expected to become available for physics experiments from early RADIOISOTOPE PRODUCTION PROGRAMME The routine radioisotope production programme with the SSC started in At that time the 66 MeV proton beam with a maximum intensity of 100 µa was used to produce the short-lived radioisotopes for the South African nuclear medicine community. For the first decade of operations, the single photon emission computed tomography (SPECT) radioisotopes which included 123 I, 67 Ga, 81 Rb/ 81m Kr, 111 In, 201 Tl and 52 Fe were routinely developed and produced with the first target station, the horizontal beam target station (HBTS) [6]. In the second decade the targetry and processing methods of long-lived radioisotopes were developed and optimised and this included: 22 Na, 68 Ge, 73 As, 82 Sr and others on an experimental basis such as 88 Y, 57 Co, 67 Cu, 133 Ba, 109 Cd and 103 Pd. In 1996 a second target station was designed and built for the bombardment of semi-permanent targets. It originally accommodated an in-house developed neon target system for the production of 18 F but this was later replaced with the more efficient enriched 18 O-water target. The routine production of 18 F with the large SSC was never envisaged to be the optimal route; it always made better sense to produce this radioisotope with a dedicated PET cyclotron. In 2013, ithemba LABS together with NTP purchased and commissioned the Siemens 11 MeV cyclotron for the exclusive production and supply of 18 F-FDG to the two PET Centres in the Western Cape, five days a week. In 2006, the third target station, the vertical beam target station (VBTS) was commissioned to exploit the high intensity proton beams that could be delivered by the upgraded SSC [7]. The targetry developed for the VBTS focussed on the production of the long-lived and high value radioisotopes such as 22 Na, 68 Ge, and 82 Sr. The technology of bombarding tandem targets with a high-intensity beam was further exploited to increase production yields. This included the bombardment of tandem targets such as Rb/Ga to produce 82 Sr/ 68 Ge simultaneously and Mg/Ga to produce 22 Na/ 68 Ge simultaneously. When the beam splitter was commissioned it provided the radioisotope production programme the opportunity to bombard tandem targets in two different stations simultaneously i.e. in the HBTS and VBTS, thus providing ithemba LABS the capacity to bombard 4 targets simultaneously. A list of radioisotopes currently produced at ithemba LABS on a routine basis is provided in Table 1. All the above infrastructure upgrades were undertaken to increase the production yield of the long-lived radioisotopes 22 Na, 68 Ge, and 82 Sr in order to meet the high market demand, but the options for further production growth have now been exhausted. Further growth can only be met by an increase in allocated beam time, which would come at the expense of one or more of the other programmes, or it can be done by procuring a dedicated cyclotron for the production of radioisotopes. AccApp '17, Quebec, Canada, July 31-August 4,

5 Table 1: Radiopharmaceuticals and radioisotopes produced by ithemba LABS on a routine basis: Product Application 67 Ga-citrate Localisation of certain tumours and inflammatory lesions 123 I-mIBG, solutions, capsules Thyroid studies and localisation of tumours such as neuroblastoma and pheochromocytoma 18 F-FDG Glucose metabolic studies, brain studies 68 Ge/ 68 Ga generator Neuroendocrine tumour localisation 82 Sr (irradiated Rb metal targets) Used to manufacture 82 Sr/ 82 Rb generators for myocardial perfusion studies 22 Na (solutions and UHV sources) Positron annihilation studies in materials research 5. PLANNED RADIOISOTOPE PRODUCTION FACILITY The acquisition of a dedicated 70 MeV cyclotron for the radioisotope production programme is proposed. This would release the SSC from its commitment to radioisotope production and greatly increase the beam time available to nuclear physics, allowing the sub-atomic physics research programme to expand into frontiers such as the Low Energy Rare Isotope Beam (LERIB). The acquisition of this cyclotron is envisaged to change the landscape of accelerator-based sciences research in South Africa as well as substantially increase South Africa s footprint in the global radioisotopes market, supplying both medical and industrial radioisotopes. The 70 MeV cyclotron dedicated to radioisotope production and research is proposed to have two separate vaults each containing two target stations. Vault 1 will consist of a medium current (80 µa) target station and a high current (250 µa) target station and Vault 2 will consist of a high current (250 µa) target station and a research target station (targetry development). The cyclotron is proposed to have two extraction ports operating simultaneously at the desired currents for each target station 24/7 for 48 weeks of the year (4 weeks maintenance period). Fig. 2 shows the proposed layout of the 70 MeV cyclotron with its two vaults, each containing two target stations which is proposed to be positioned in the existing proton and neutron vaults of the current Medical Radiation Therapy programme. Figure 2: Proposed layout of the 70 MeV cyclotron facility, indicated in yellow. AccApp '17, Quebec, Canada, July 31-August 4,

6 With the 70 MeV cyclotron it is envisaged that the radioisotope production programme will continue with the currently produced short-lived radioisotopes ( 123 I and 67 Ga) and long-lived radioisotopes ( 82 Sr, 68 Ge and 22 Na) which have a high market demand. Other radioisotopes which were no longer produced over recent years due to a low market demand or limited beam time could be restarted for production, including 201 Tl, 111 In, 109 Cd, 67 Cu, 133 Ba and 103 Pd. In addition, an additional catalogue of radioisotopes referred to as the alpha-particle-emitting radioisotopes and therapeutic-diagnostic (theranostic) radioisotopes will be investigated for production. Alpha-particle-emitting radioisotopes have been the subject of considerable investigation as cancer therapeutics. In the context of targeted therapy, alpha-particle emitters have the advantage of high potency and specificity, a technique also referred to as Targeted Alpha Therapy (TAT). Alpha-particle-emitting radioisotopes produced by a cyclotron that are medically relevant and currently available for the potential therapeutic application are 211 At, 213 Bi, 225 Ac, 227 Th and 149 Tb. Theranostic radioisotopes have in recent times also been receiving attention. Theranostic radioisotopes i.e. matched pairs of radioisotopes that behave, in vivo in the same way as an imaging radioisotope and a therapeutic radioisotope. The 43 Sc radioisotope can be used for the diagnostic nuclear medicine application and the match partner 47 Sc can be used for the therapeutic nuclear medicine application. Others include the matched pairs 123 I (diagnostic) and 131 I (therapeutic); 64 Cu(diagnostic) and 67 Cu (therapeutic); 152 Tb (diagnostic) and 149 Tb (therapeutic). The biggest challenge producing some of the aforementioned radioisotopes is the limitations of the 70 MeV maximum energy of the cyclotron. Some of the optimal production routes are only obtained with a proton beam of >100 MeV (for example 225 Ac) or with an alpha beam (for example 211 At). The research and development programme for new radioisotopes with the 70 MeV cyclotron will therefore be positioned as per production viability and market demand MV TANDETRON ACCELERATOR After 51 years of excellent service, the CN 6 MV single ended Van de Graaff (VDG) accelerator that was commissioned in 1964 at the Southern University Nuclear Institute (SUNI) at Faure in South Africa, was decommissioned in December SUNI, known today as the Materials Research Department (MRD) at ithemba LABS, housed this accelerator and was the beginning of the first Nuclear Facility in the Cape Town area to be used for Low Energy Nuclear Physics Research and applications. The VDG successfully operated until the 24 December This accelerator was used for low energy nuclear physics research, ion-solid interaction research and the provision of high sensitivity analytical technologies [8]. The main areas of current research at the MRD are: nano-sciences & nanotechnology and thin film physics using material characterization and modification with radiation and scanning probe microscopy; biotechnology trace element distribution and mobilization in biological systems; environmental and geological studies using ion beams; ferrous, non-ferrous alloys, noble metals and materials composites for high technology applications and cultural history materials characterization. Through all these decades the MRD has been at the forefront of Ion Beam Analysis (IBA) research and applications including the development of state-of-the-art techniques such as in-situ Real-Time RBS [9], Cryo Nuclear Microprobe (Cryo-NMP) [10] and Heavy Ion (ToF) ERDA [11]. This Van de Graaff accelerator was recently replaced by a modern state-of-the-art 3.0 MV Tandetron manufactured by High Voltage Engineering Europa and commissioned in May 2017, shown in Fig. 3. AccApp '17, Quebec, Canada, July 31-August 4,

7 Figure 3: New 3.0 MV Tandetron accelerator at the Materials Research Department The main objectives of the Materials Research Department with regards to the new tandetron are: - Continue the research projects that are currently running while developing new beam lines and endstations to support the potential new research projects that users have requested. This includes work on materials synthesis and characterization by specialized ion sources and ion beam types. - After commissioning of the tandetron and re-commissioning of the two previously available beam lines for nuclear microscopy and thin films characterization, we expect the lateral resolution on the ion probe of the nuclear microprobe (NMP) to improve to a theoretically estimated nm. This is one order of magnitude better than previously possible and enables scanning of smaller areas with better current intensities. The stability of the new Tandetron, combined with the improved resolution, will allow the IBA scientists to adjust the quadrupole lenses for optimal 2-dimensional elemental mapping and characterization. This increase in lateral resolution will particularly benefit research on trace element distribution and mobilization in biological systems, using the Cryo-NMP facility. - Going to the nanometre size is a fundamental priority for the development of niche areas of research, particularly in nano-structured materials and their applications. Secondly, a stable accelerator will ensure that in-situ RBS / ERDA experimental data are collected with a precise and constant ion beam current. This also applies to NMP since the event-by-event files containing the mapping information will be executed at constant current. - The tandetron was purchased with two multicusp sources for H - and He - -ions with current thresholds of ~ 1mA before the low energy magnet, and ~ 200 µa post-acceleration for protons. In practice, maximum currents on target will be about 100 µa, particularly if the proposed beam line for astrophysics (to be used for studies of low energy nuclear reactions in nucleosynthesis processes) is commissioned in the near future. - For the first time the new Data Acquisition Systems (based on the MIDAS platform) built during the last two years for the techniques (micro-pixe/bs, RBS/ERDA (at RT and in-situ) and Channelling), will be integrated with the tandetron ion sources and re-commissioned. There will be the reestablishment of the quantitative Real-Time Elemental Mapping algorithm (tested at the NMP with the VDG on the last year of operation), that reconstructs elemental maps for display while the experiment is running. AccApp '17, Quebec, Canada, July 31-August 4,

8 - A Heavy Ion (HI) Sputtering Source was also included in the accelerator infrastructure. The availability of a HI Sputter Source will create many possibilities for Ion-Solid Interaction research. In the basic ion-solid interaction research domain, measurements of fundament parameters (stopping power S(E), straggling, effective ranges for analysis), which are involved in the physics of slowing down processes of HI in heavy metals will be carried out. Furthermore this provides appropriate infrastructure to users to perform surface characterization elemental depth profiling with highly charged heavy ions particularly in the fields of nano-sciences, materials engineering, condensed matter and characterization of samples used in nuclear physics experiments at the SSC. - Other potential research infrastructure that would be implemented in one of the beam lines, is a facility specializing in low energy nuclear research for the understanding of the processes of how light nuclei nucleo-synthesis occurs in the universe (astrophysics). If possible, stardust micro particles will also be analysed with the nuclear microprobe to quantify elemental content and distribution. At the same time another line will be devoted to Real-Time IBA characterization of thin film deposition over selected substrates to study the possible formation of in-situ thermodynamic phases arising from the process of deposition. - A new beam line will be implemented to carry out IBA measurement in-air for cultural heritage studies in relevant Southern African archaeological materials to decipher the non-written history of indigenous communities that were living in the area more than 500 years ago. The same in-air facility could be used for the in-situ study of high temperature metals/alloys phases with applications in materials engineering and nano-technology. 7. ATOMIC MASS SPECTROMETRY APPLICATIONS The 6 MV EN tandem accelerator located at the ithemba LABS site in Johannesburg has undergone a major refurbishment, resulting in the installation and commissioning of Africa s only accelerator mass spectrometer (AMS). Applications of AMS are diverse, but the initial focus of the ithemba LABS facility will be in response to the Palaeoscience imperative of the Department of Science and Technology in South Africa. The establishment of a chronology is central to palaeoscience, and the AMS facility at ithemba LABS is specifically recognised in the South African Strategy for the Palaeosciences, which was published in the Government Gazette as a national policy in 2011 [12]. The policy space is motivated by a unique geological circumstance in southern Africa that preserves a record of the evolution of life and in particular mammals and humans. The region has not been glaciated in the last 300 Ma, and slow landscape erosion processes have gradually exposed sedimentary strata that were deposited between 300 and 65 Ma. Within these sediments are preserved the fossil evidence for the evolution of mammal-like reptiles the precursors to dinosaurs that eventually evolved in to mammals and particularly humans. The fossil record continues forward in time to include dinosaurs. This is all a little too old to date directly using AMS techniques, but the evolution of the landscape is explored through applications of cosmogenic dating. Cosmogenic dating is based on the measurement of nuclides such as 10 Be, 26 Al and 36 Cl that are formed during neutron spallation interactions when cosmic radiation bombards the earth surface. The cosmogenic nuclides are radioactive, and eventually a stable land surface will reach an equilibrium in which nuclide production in the surface rock and decay are matched. The process of surface erosion will gradually remove the affected rock, and reveal rock that has been unaffected by the cosmogenic nuclide production [13]. Embedded within this ancient southern African landscape are notable depositional features in the form of karstic, fluvial and alluvial deposits. These contain evidence for the evolution of anatomically modern humans from their Australopithecine ancestors. Recent finds such as Australopithecus sediba, and Homo naledi are critical in understanding the human trajectory, but dating these sites has been challenging. Dates AccApp '17, Quebec, Canada, July 31-August 4,

9 ranging from 4.2 Ma through to 236 ka have been generated for various occurrences, but the techniques are not ideal for these sites, and this frustrates the interpretation of these key fossils [14]. Cosmogenic techniques measured by AMS are also being applied, but the approach differs slightly from exposure dating of land surfaces. In these cave environments the dating focusses on rock material that has received a cosmic dose at the surface, but has then been deposited in the caves far beyond the range of cosmic radiation [15]. The cosmogenic nuclides that were produced at the surface decay without a supporting formation mechanism. If two cosmogenic nuclides can be measured (typically 10 Be and 26 Al), each with a different decay rate but with a common production history, then the measured difference between the two is indicative of the burial time. The technique is called cosmogenic burial dating. The spread of humanity from its Australopithecine ancestors in Africa to the first truly global hominins that have been given the genus Homo is associated with an archaeological entity known as the African Earlier Stone Age. In Southern Africa the evidence is in the form of Oldowan stone tools dating to Ma, the Acheulean stone tools dating Ma [16]. The transition to the Middle Stone Age takes place at about 500 ka and stone tools known as the Fauresmith Industry date to this period. The Middle Stone Age is again a poignant period in human development, because it is the time when modern human behaviour, rather than modern human morphology, is first noted globally [17]. Sites such as Pinnacle Point and Blombos Cave have yielded evidence of abstract thought and decorations which are considered the oldest art in the world. The modern behaviour dates to about ka, a period in which there is believed to be a reduction in the human genome, suggesting that any human population dating to this time is indeed the only human population from this time [18]. Cosmogenic applications to the rich Middle Stone Age of southern Africa have not been fully explored, mainly because a local facility was not available prior to the commissioning of the ithemba LABS AMS laboratory. There are many archaeological sites around southern Africa that are assigned to the Later Stone Age. This was a period in which a refined hunting and gathering economy was interwoven with a beautiful expression on cave walls in the form of rock art. Rock art has been dated indirectly (from associated material) to as far back as 26 ka at Apollo 11 Cave, and recently the rock art has been dated directly using radiocarbon [19]. Radiocarbon is the standard approach used globally to date archaeological material from this period, and despite the abundance of sites, constraints in access to a local AMS radiocarbon facility has meant that the chronology for this period has been based on the least possible tenable evidence [20]. This is even more important in the subsequent periods in which pastoralists and farming economies emerged in the region. The history of modern populations in southern Africa is reflected in this archaeological domain. The development of an AMS facility at ithemba LABS ushers in a new era for palaeoscience in southern Africa. It facilitates high-level capacity development in the science of chronology, and it also facilitates the production of many more dates that will ensure a kind of dating hygiene [20] that is central to worldleading excellence palaeoscience as envisaged in the South African Strategy for the Palaeosciences [12]. 8. CONCLUSION Several new facilities have become available recently, expanding the range of applications of accelerators at ithemba LABS. Most prominent amongst these are the AMS facility and the new 3 MV Tandetron for materials research. A major revision to the SSC facility is being planned, with the introduction of a new 70 MeV cyclotron for radioisotope production under the ACE Isotopes project, and a radioactive ion beam facility under the ACE Beams project. REFERENCES 1. J.L Conradie et al, Cyclotrons at ithemba LABS, Cyclotrons 2004 Conference, Tokyo (2004). AccApp '17, Quebec, Canada, July 31-August 4,

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