[en] Using a tandem Van de Graaff equipped with a moderately high resolution injector system (M/ΔM approx. 150) we have investigated the stability of the negative hydride ions of potassium. We find that, using a Cs sputter source, and NH₃ gas appropriate for CaH₃^- emission, the ratio KH₃^-/K^- is less than or equal to 10^-8 (and perhaps much less). These results are very favourable to the eventual detection of natural ⁴¹Ca (half-life 10⁵ years) using a tandem electrostatic accelerator

[en] ¹⁰Be (t/sub 1/2) = 1.5 MY) is(formed in the upper atmosphere by cosmic ray spallation on nitrogen and oxygen. It is transported to the earth's surface via precipitation. In the oceans it is eventually associated with solid phases depositing on the ocean floor such as manganese nodules and deep-sea sediments. One of the assumptions that is normally made in analysis of such processes is that ¹⁰Be has been produced at a relatively uniform rate over the pat several million years. If we assume, in addition, that the initial specific concentration of ¹⁰Be as it precipitates with a solid phase is invariant with time, then we would expect that the decrease of the ¹⁰Be concentration as a function of depth in a deep-sea core or in a manganese nodule would provide a record of sediment accumulation rate in the former and of growth rate in the latter. The possibility of using cosmic-ray produced ¹⁰Be for the dating of marine deposits had been proposed 25 years ago by Arnold and Goel et al. The method of analysis used by these investigators, and those subsequently pursuing the problem, was low-level β counting. Though the potential of using ¹⁰Be for dating manganese nodules was explored more than a decade ago, only a few measurements of ¹⁰Be in nodules exist in date. This is largely because of the ¹⁰Be measurements in environmental samples have gained considerable momentum during the past 3 to 4 years, after the development of accelerator mass spectrometry for its determination

[en] Systematic errors in accelerator dating can be minimised by transmitting in sequence the three isotopes of carbon through the accelerator. Many processes exist which cause isotopic fractionation, and the extent of these has been discussed, but is not predictable. Many are linear, that is, a first order correction of the ¹⁴C fractionation can be calculated from a measurement of e ¹³C/¹²C ratio, but some processes are known to be not so well behaved. It has to be assumed that such processes remain unchanged between measurements on sample and standard; with this assumption it has been demonstrated that the technique, although failing to provide absolute isotope ratios, provides in principle sufficient data for the calculation of dates to an accuracy of better than 0.1%. Of course accuracy is not only limited by such fluctuations, but also for example by the Poisson statistics and by contamination, and this conclusion should only be taken to indicate that there is no need for further data in the form, say, of a separate ¹³C/¹²C measurement - there would be no way of using such data

[en] The ISOTope and Rare Atom Counting Equipment (ISOTRACE) facility was effectively launced in April 1979 at the approval of the Natural Sciences and Engineering Research Council of Canada for the purchase of a General Ionex TANDETRON mass spectrometer. In 1980 the funds to develop the facility for the various applications were obtained from the Department of Supply and Services with the Ministry of Energy, Mines and Resources, the Canadian Geological Survy and Environment Canada as sponsors. A steering commitee coordinates this development while a projects evaluation and allocation committee 2), consisting of experts from ouside the ISOTRACE group, was put in place in late 1980

[en] The reflected beam sputter ion source has been found to have an inherent need for frequent readjustment of several voltages during use. Its lack of cylindrical symmetry is reflected in the asymmetry of its beam, and the position and shape of the sputtering Cs⁺ beam have been shown to depend strongly on the Cs⁺ current because of space charge effects. There has been a tendency for ion source designs starting from a simple concept to be subjected to continual improvement a process which, while improving one feature, often complicates the originally simple concept, and makes operation more complex

[en] Radionuclide mass spectroscopy at the University of Rochester tandem Van de Graaff accelerator is reviewed. Measurements have been made with ¹⁰Be, ¹⁴C, ²⁶Al, ³²Si, ³⁶Cl, and ¹²⁹I, enabling age estimates to be made with several different half-life isotopes. Sensitivities of the measuring method have, in some cases approached one part in 10¹⁶. 37 references

[en] In the absence of written records that go back more than 150 years, the frequency of major earthquakes in the seismically active regions of the western United States can only be deduced from geologic evidence. Scarps along the Wasatch fault near Salt Lake City, Utah exhibit cumulative surface displacements as large as 10 meters in alluvial deposits that post-date the recession of Lake Bonneville, 12,000 years ago; although no damaging earthquakes have occurred since the area was settled. Recent trenching studies by Swan et. al. have exposed ancient surface soil layers in which discontinuities reveal a sequence of significant surface faulting events. Radiocarbon dates of detrital charcoal from these deposits would be a record of earthquake recurrence intervals, vital data for contemporary earthquake hazards assessment. Most of the samples collected so far have been too small for conventional beta-decay counting. We report a successful radiocarbon assay by direct atom counting of four milligram-sized specimens from the Wasatch study

[en] From early 1950's a carbon 14 dating laboratory was created at the Centre des Faibles Radioactivites de Gif-sur Yvette (C.F.R.). From this time, more than 5000 archaeological and geological samples were measured with the Libby method by this laboratory. C.F.R. is in the way to actualise its dating activities with the new accelerator method. A 3 MV General Ionex Tandetron is planned to be located at Gif-sur-Yvette next year and shared with Orsay University for ¹⁴C, ¹⁰Be and ³⁶Cl mass spectroscopy measurement. During the same time attempts have been made to adapt the Super FN Tandem of the Centre d'Etudes Nucleaires de Saclay for ¹⁴C dating

[en] The potential of tandem accelerator based mass spectrometry [TAMS] for the detection and measurement of rare isotopic abundances has been demonstrated consistently at numerous laboratories. Based on these exploratory experiments, a number of dedicated facilities are presently under construction, primarily for the measurement of the radioisotopes ¹⁴C and ³⁶Cl at natural abundances. To further increase the versatility of the Unversity of Toronto Isotrace laboratory using TAMS, a series of modifications is being considered to make possible the detection of heavier ions, for example the rare earth elements, Pt, Pu, and to improve the precision of isotope ratio measurements. These modifications are discussed

[en] The evaluation and management of water as a resource requires an understanding of the chemical, and geological interactions that water effects or undergoes in the hydrologic cycle. Delivery of water to the land surface by precipitation, subsequent streamflow, circulation in surface waters and evapotranspiration, infiltration, recharge, movement of waters in the subsurface, and discharge are of interest. Also important are the quality of water, water's role in mineral dissolution, transport, and deposition, and the various water-related geotechnical problems of subsidence, tectonics, slope instability, and earth structures. Mathematical modeling techniques are available and are being improved which describe these phenomena and predict future system behavior. Typically, however, models suffer from substantial uncertainties due to insufficient data. Refinement, calibration,and verification of hydrologic models require expansion of the data base. Examination of chemical constituents of water which act as tracers can often supply the needed information. Unfortunately, few tracers are available which are both mobile and chemically stable. Several long-lived radioisotopic hydrologic tracers exist, however, which have received little attention in hydrologic studies to date because of low concentration, low specific activity, or sample size limitations. Recent development of ultra-sensitive accelerator mass spectrometry techniques (AMS) by Purser and others (1977), Nelson and others (1977), Bennett and others (1978), Muller and others (1978), Raisbeck and others (1978) is now expected to provide access to many of these tracers