[en] The detection of characteristic x-rays using a Si(Li) detector has been investigated for the purpose of nuclear charge (Z) identification of fission fragments. Positive Z identification of one particular x-ray requires that K x-rays be used. The quantitative ambiguity due to K shell internal conversion demands that K shell vacancies be produced after nuclear excitation has relaxed. In this study, inner-shell vacancies were produced by impact ionization. The average x-ray yield for fragments stopping in a silicon surface-barrier detector was measured to be 0.018 +- 0.004 K x-rays per fragment. Similar studies using materials heavier than silicon showed a higher x-ray yield. A K x-ray Z spectrometer is proposed utilizing a germanium particle detector for x-ray production with efficiency estimated as high as 18%. However, due to nuclear straggling effects, the heavy stopping materials necessary for efficient x-ray production cannot be used as a fission fragment energy detector for a time-of-flight mass measurement of 1 amu resolution

[en] Over the past years, Tandem Accelerator Mass Spectrometry (TAMS) has become established as an important method for radionuclide analysis. In the Arizona system the accelerator is operated at a thermal voltage of 1.8MV for C-14 analysis, and 1.6 to 2MV for Be-10. Samples are inserted into a cesium sputter ion source in solid form. Negative ions sputtered from the target are accelerated to about 25kV, and the injection magnet selects ions of a particular mass. Ions of the 3+ charge state, having an energy of about 9MeV are selected by an electrostatic deflector, surviving ions pass through two magnets, where only ions of the desired mass-energy product are selected. The final detector is a combination ionization chamber to measure energy loss (and hence, Z), and a silicon surface-barrier detector which measures residual energy. After counting the trace iosotope for a fixed time, the injected ions are switched to the major isotope used for normalization. These ions are deflected into a Faraday cup after the first high-energy magnet. Repeated measurements of the isotope ratio of both sample and standards results in a measurement of the concentration of the radionuclide. Recent improvements in sample preparation for C-14 make preparation of high-beam current graphite targets directly from CO₂ feasible. Except for some measurements of standards and backgrounds for Be-10 measurements to date have been on C-14. Although most results have been in archaeology and quaternary geology, studies have been expanded to include cosmogenic C-14 in meteorites. The data obtained so far tend to confirm the antiquity of Antarctic meteorites from the Allan Hills site. Data on three samples of Yamato meteorites gave terrestrial ages of between about 3 and 22 thousand years

[en] A portable Faraday cup design is described for the accurate measurement of large-diameter, low-current, and high-energy proton beams traveling in air. The unit has been tested with protons from 4 to 300 MeV. The unit has an accuracy of 10% for beams of 1 pA, improving to about 2% accuracy for ion currents of 20 pA to 1 microA. For the accelerated testing of LSI parts, the Faraday cup is particularly critical, since this application requires very low currents, typically 10--100 pA (1 pA = 6 x 10⁶ protons/s), operating in an electronically noisy accelerator environment

[en] The static electric quadrupole moment Q₂⁺ and the B(E2; 0⁺ → 2⁺) value of the 2⁺ first excited state of ²⁰⁴Hg have been determined using the reorientation effect in Coulomb excitation. An annular Si surface-barrier detector was used to detect backscattered ⁴He, ¹²C and ¹⁶O projectiles. In a subsidiary experiment, spectra were obtained from ²⁰⁴Hg(p,p') ²⁰⁴Hg using Si surface-barrier detectors, and the results were used in conjunction with previously existing data to povide information on higher states of ²⁰⁴Hg which might participate in the Coulomb excitation of the 2⁺ state. From a 3-level analysis, the authors find Q₂⁺ = +0.40 +- 0.20 e.b and B(E2; 0⁺→ 2⁺) = 0.423 +- 0.0005 e² b². These results are in good agreement with the predictions of particle-vibrational coupling calculations. The value obtained for Q₂⁺(²⁰⁴Hg) is substantially smaller in magnitude than values of Q₂⁺ previously determined for ^198200202Hg

[en] The 3 MV tandem accelerator mass spectrometer at the University of Arizona was delivered and installed by General Ionex Corporation in September, 1981. The machine was originally designed as an ultrasensitive mass spectrometer for ₁₄C, and is in the process of being upgraded to do ₃₆Cl and other rare isotopes as well. In this paper only the performance characteristics of the machine that relate to ₁₄C work are discussed

[en] Prominent groups are observed corresponding to excited states in the region of 2.6 MeV in the scattering of 24 and 27 MeV α-particles from ^198200202204Hg and ^204206208Pb. For each of the Pb isotopes the state concerned is identified with the known 3^- octupole vibration. Angular distribution measurements for scattering to the Pb and ²⁰⁴Hg states are in agreement with octupole-vibration coupled-channels predictions, and systematic trends suggest that the states observed in the isotopes ^198200202Hg can also be attributed to octupole vibrations

[en] Coulomb excitation of the 0.718-MeV, Jsup(π) = 1⁺, first excited state of ¹⁰B has been studied using projectile excitation by ²⁰⁸Pb and observing the backward scattered particles. The results give a clear indication of the virtual excitation of the giant dipole resonance as a second-order effect. The observed magnitude is consistent with the usual hydrodynamic model estimate and with a recent shell-model calculation

[en] A description is given of the tandem accelerator mass spectrometer which has recently been installed at the University of Arizona. This system is the primary instrument of a National Science Foundation Regional Instrumentation Facility. Results of tests of its operation are presented. Several experiments on archaeological and other types of samples are described. (orig.)

[en] A technique is described in which a 2 MV tandem accelerator mass spectrometer is used to detect atoms of the radioisotope ¹⁰Be. The lower detection limit is shown to be about ¹⁰Be/⁹Be=5x10¹³. Results from measurements at lower terminal voltages are also presented. (orig.)

[en] Results of tests on the tandem accelerator mass spectrometer (TAMS) at the University of Arizona are presented. These results demonstrate: (a) measurements of ₁₄C/₁₃C ratios with precisions of a few percent can be made in a period of one to several hours; (b) measurements with precisions of 0.5% have been made in which the uncertainties were mainly statistical and in which contributions to the uncertainty of machine fluctuations were negligible; (c) precise measurements of the ratio of ₁₄C/₁₃C in samples of N.B.S. oxalic acid and of 1890 wood are consistent with the accepted value of that ratio; (d) the real signal from a 44,000 year old sample is equal to the background rate produced from a dead carbon sample. In addition, results of some measurements on archaeological samples are presented