Charged particle activation of medium Z elements

A survey has been made on the application of charged particle activation analysis for the detection of traces of medium Z elements (40≤Z≤58, 72, 74) using protons and deuterons of 20 MeV,³He and⁴He ions of 40 MeV. The product nuclides considered were γ-ray emitting radioisotopes with half lives ranging from 10 min to 3 days. Based on the thick target yields obtained, proton activation was found to provide an optimum compromise between sensitivity and selectivity.     

Studies in heavy ion activation analysis

A procedure for measuring trace amounts of Li and Be in different types of samples has been studied using a 12.5 MeV¹⁴N beam. At this energy the principal nuclear reactions are⁶Li(¹⁴N, d)¹⁸F,⁷Li(¹⁴N, t)¹⁸F, and⁹Be(¹⁴N, αn)¹⁸F. Detection limit for destructive analysis for either beryllium or lithium has been calculated at 300 ppb with a determination limit of 5 ppm for an irradiation with a beam of 1 μA·h/cm². Destructive analysis was performed on CANMET SY-2 and USGS BCR-1 (rock samples 1–10 ppm Be). Non-destructive analysis for beryllium and lithium was performed on NBS SRM 610 (500 ppm trace element glass), NBS 612 (50 ppm trace element glass), and NBS SRM 181 (Spodumene ore, 6.4% Li₂O). Detection limit of 2 ppm has been calculated for nondestructive analysis of either lithium or beryllium.     

Comparison of nondestructive proton and neutron activation: The case of biological samples

The capabilities of reactor neutron and 12 MeV proton activation were evaluted on samples of orchard leaves, beef liver and bovine liver. Based on γ-ray spectrometry, As, Ca, Cu, Fe, Mo, Pb, Sr, Ti, Zn and Zr at levels ranging from 2 to 20 900 ppm were detected following proton activation of 1 hour. Al, Br, Ca, Cl, Cu, Mg, Mn, Rb and V (ranging from 0.4 to 20 900 ppm) were measured by neutron activation (1 min irradiation). As, Ba, Br, Cr, Co, Fe, Hg, La, Na, Rb, Sb and Zn (ranging from 0.2 to 2400 ppm) were determined following a 14 h neutron irradiation. Although covering different elements, the two techniques are comparable in their scope, i. e. detection limits that can be achieved and number of elements that can be detected simultaneously.     

Recent developments in chemical characterization with MeV ion beams

A multitude of ion-atom interactions are induced with projectiles of E0.1 MeV/nucleon. Analytical techniques derived from these include particle induced X-ray emission (PIXE), charged particle activation analysis (CPAA), prompt nuclear reactions (PNR), and Rutherford backscattering spectrometry (RBS). Among their features are broad elemental coverage (PIXE), subnanogram sensitivity (PIXE, CPAA), isotopic specificity (CPAA, PNR), and depth resolution (RBS, PNR). A limiting requirement with each technique is the need for high intensity ion beams. Novel approaches seek now to obtain analytical information with very small numbers of bombarding ions. Sample integrity is then maintained; moreover, they can be delivered in a microbeam (diameter 5 mm). A phenomenon which under these conditions provides useful analytical information is the particle induced desorption of molecular fragments. Thus, microscopic chemical analysis can be achieved with a small number (<10,000) of heavy fast projectiles and identification of the species desorbed from the sample surface via time-of-flight mass spectrometry. Experimental work with 84 MeV kr ions indicates the following: (a) high desorption yields can be obtained (>50%); (b) mass spectrometry on microspots (diameter of a few m) is feasible; (c) < 10⁶ atoms can be detected. Further capabilities of ion beams for minute, detailed, and comprehensive chemical characterization remain to be explored.