Search Results

You are looking at 1 - 10 of 42 items for

  • Author or Editor: E. Schweikert x
  • Refine by Access: All Content x
Clear All Modify Search

Professor Richard E. Wainerdi

Presented with the Hevesy Medal for 1977

Journal of Radioanalytical and Nuclear Chemistry
Author: E. Schweikert
Restricted access

Abstract  

Various ion beam techniques (E≥1 MeV/amu) are compared from the standpoint of their analytical capabilities: Charged Particle Activation Analysis (CPAA), Particle Induced X-Ray Emission (PIXE), Ion Induced γ-Ray Emission for bulk analysis, Prompt Reaction Analysis (PRA), Rutherford Backscattering Spectrometry for surface layer characterization and ion absorptiometry for microscopic analysis. With CPAA and PIXE≥70 elements can be detected with sub-ppm sensitivity. The scope of CPAA is being extended with heavy ion beams for radioactivation of H, He, Li, Be, B, C isotopes. In surface layer characterization recent developments in PRA and RBS also involve heavy ion beams. In RBS they can significantly enhance mass resolution for M>50 in comparison with α scattering. For example,63Cu and65Cu can be quantitatively identified in surface films using a 1 MeV/amu40Ar beam. In microscopic analysis, the nuclear microprobe can provide atom-specific signals from quantities ≥10−12 g on spots of a diameter ≥2 μm. Ion absorptiometry techniques can sense density variations as low as ±0.5% in 1 μm3 or less of sample volume.

Restricted access

Abstract  

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.

Restricted access

Abstract  

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.

Restricted access

Abstract  

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.

Restricted access

Abstract  

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.

Restricted access

Abstract  

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 and reduction.

Restricted access

Abstract  

This method is based upon the measurement of 3.95-hr43Sc which is formed during α-activation from40Ca, the most abundant (96.8%) isotope of calcium. The excitation function for the40Ca(α, p)43Sc reaction was determined and the maximum yield of43Sc (about 107 cpm per mg of calcium for a 1-hr irradiation at a beam current of 1 μA) was obtained at an irradiation energy of 14 MeV. The interference free sensitivity of the method at this energy was found to be 8.5·10−12 g, for a 1-hr irradiation at a beam current of 10 μA. The elements most likely to interfere with the determination are potassium and scandium. The extent of this interference was investigated as a function of irradiation energy and methods to eliminate or subtract the activity formed from these elements are discussed. An attempt was made to determine non-destructively the calcium content of very pure silicon and aluminium and upper limits for the concentration of calcium in these samples were set at 0.27 ppb and 6.9 ppb, respectively. Magnesium, thulium oxide and yttrium oxide samples of known calcium content were also analysed.

Restricted access

Abstract  

The scope of NDP can be expanded by measuring (via time-of-flight) the kinetic energies of the recoils emitted from (n,p) or (n,) reactions. When they occur inside a solid, the energies of the emerging recoils reveal depth from which they originated. The Recoil Nucleus Time-of-Flight NDP (RN-TOF-NDP) technique can reveal the depth distribution of some isotopes (e.g.,10B,210Bi) with a resolution of a few Å. Furthermore, it is possible to detect atomic and molecular species ejected at the surface site where the recoil emerges from the solid. This paper discusses the methodology for RN-TOF-NDP and its applications including surface analysis based on atomic and molecular ions codesorbed with the recoils.

Restricted access

Abstract  

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.

Restricted access