The backscattering performance of 2 MeV He+ and N+ beams was studied using Ta2O5 targets as test targets. To allow ready comparison, the scattering geometry, projectile energy, and detection system were kept identical for both beams. Tantalum oxide films with thicknesses of 200 Å to 4000 Å were examined. For thickness determinations, beam straggling was found to be the major limiting factor. For thickness measurements below 1000 Å the N+ beam is best suited for larger thicknesses; the He+ beam is superior. For stoichiometric determinations both beams provide equally accurated and precise data.
An examination of the literature concerning the determination of cadmium by Prompt Gamma-Ray Neutron Activation Analysis (PGNAA) has been conducted. In-vivo activation analysis of the liver and kidney is the most common application reported and is briefly reviewed here. This review will concentrate on the determination of cadmium in in-vitro systems. These include a number of different complex matrices such as geological, environmental and biological materials, as well as water, sediments, foods and construction material. Nuclear reactors, accelerators, and radioisotopes have all been used as neutron sources with varying degrees of sensitivity.
The reaction103Rh(p, n)103Pd was investigated for the trace detection of Rh. Maximum activation of Rh with minimal interferences was achieved with protons of 11 MeV. The detection limit for the nondestructive assay of Rh is 0.03 ppm.
The Time-of-Flight (ToF) technique can be used for mass identification, for separation of a specified mass or for measuring the energy of a given mass particle. The instrumentation required is simple and low in cost. The method features high yield, transmission efficiency is typically of 5 to 20%. Even with short flight paths (5 to 10 cm), ToF has adequate mass resolution (M/M
300 to 500) for identifying isotopic species. This paper examines the scope of ToF in nuclear science with examples in mass spectrometry, in mass separation and in kinetic energy measurements of fixed mass particles. An example of the latter is the energy determination of recoil nuclei. If a recoil is produced inside a solid, the residual recoil energy reveals the depth from which it originates. This approach is used for profiling nitrogen via14N(n, p)14C. The ToF measurement of the14C recoil energies reveals the depth distribution of nitrogen with better than 50 Å resolution.
A survey is given on the analytical use of X-ray emitting radioisotopes produced by charged particle activation. Thirty-nine
proton and deuteron reactions were considered on twentysix elements (34≤Z≤82). Thick target yields and sensitivity estimates
are presented. The features and limitations of this method and the scope of non-destructive and destructive determinations
are discussed. The main interest of this approach is to open an avenue for trace analysis with simplified data acquisition
Trace analysis methods have been developed for determining thallium, lead and bismuth. Proton or deuteron activation is used
followed by a radiochemical separation of the reaction products:203Pb from thallium,206Bi from lead, and207Po from bismuth. Activation curves are presented for different nuclear reactions occuring on the elements studied. Determinations
have been carried out on high purity samples containing varying amounts of thallium, lead, and bismuth. Based on experimental
data, the detection limits are estimated at 0.01 ppm for lead, and 0.001 ppm for thallium and bismuth, respectively.
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.
Among the numerous heavy ion reactions, those of potential interest for chemical analysis can be identified based on their
Q values, Coulomb barriers, and threshold energies. A simple computer code has been written for these calculations. The use
of the calculated data is illustrated with a survey of the possibilities of HIAA with N+, Li+, B+, Be+ and C+ beams yielding radioisotopes with half-lives of 10 to 104 sec.
Excitation functions for proton energies up to 20 MeV have been measured for65Cu(p, n)65Zn; Sn (p, xn)115Sb,116mSb,117Sb,118mSb; Mo (p, xn)94Tc; Te (p, xn)121I,123I,128I,130I; Pd (p, xn)104Ag; Cd (p, xn)109In,110mIn,113mIn; Cs (p, xn)133mBa. The precision of the measurements (overall error estimated at ≤20%) and the conditions for interference-free detection
of these elements at trace levels are also discussed.
Authors:M. Vargas, J. Batchelor, and E. Schweikert
The determination of lead via 30 MeV4He bombardment to produce the long-lived radioisotope210Po was studied. The validity of the technique was tested by the analysis of a series of NBS glass samples doped with 61 different trace elements at nominal 500 to 1 ppm level concentrations. The measurement sensitivity of alpha counting with surface barrier detectors was evaluated. The detection limit was estimated at 0.1 ppm. The4He-activation technique coupled with -counting features a unique combination of sensitivity and accuracy for the trace determination of lead.