G.W.A. Newton

Excitation functions and isomer ratios in the reactions 93Nb(α, xn) (x = 1−4)

Abstract Excitation functions and isomer ratios for 93Tc96Tc from the reactions 93Nb(α, xn) have been measured between 16 and 72 MeV. The excitation functions cannot be satisfactorily explained with a model assuming only a statistically-equilibrated compound nucleus, but the inclusion of pre-equilibrium processes produces a much better fit. The isomer ratio data (expressed as high spin/low spin) show a characteristic increase followed by a decrease in the tail of the excitation function. This is explained by taking explicit account of the distribution in spin arising from the initial interaction. When combined with hybrid (compound nucleus plus pre-equilibrium) model calculations, this provides a satisfactory explanation of the observed isomer ratios. The fall in isomer ratio arises from the increasing importance of pre-equilibrium processes in the tail of the excitation function, since these processes appear to produce residual nuclei with lower average spins than those formed by compound nucleus decay.

103Rh(α, xn) 107−xAg reactions

Abstract Excitation functions have been measured for the yields of Ag isotopes in the reactions 103 Rh(α, xn ) 107− x Ag for x = 1−5. The results are consistent with a combination of compound nucleus and pre-equilibrium mechanisms. The low values of experimental isomer ratios [(high spin)/(low spin) measured x = 1, 3 and 5 only)] compared to theoretical predictions indicate that a considerable fraction of nuclei are by-passing the high-spin isomer to populate the low-spin state. This fraction has been estimated as 27.5% for the (α, n ) reaction, 16.7% for the (α,3 n ) reaction and 18.2% for the (α, 5 n ) reaction.

Black-on-red ware in the levant: A neutron activation analysis study

Abstract Black-on-red ware was widely used throughout the Eastern Mediterranean between about the 11th and 8th centuries BC. Its origins have been much discussed: its ubiquitous appearance throughout the region could be a result of either several manufacturing regions or a single place of manufacture associated with considerable trading in the ware. In the present study, neutron activation analysis has been carried out for 15 chemical elements in 58 specimens of black-on-red ware from Cyprus (11), Syria (26) and Palestine (21). The analytical results clearly separate the ware into three major groups, corresponding to origins in Palestine, Syria and Cyprus. The hypothesis of a single source of the ware is therefore not tenable. All 14 of the Syrian finds of the single-handled neck ridge juglet are closely grouped with the Cyprus samples, indicating extensive trade in this vessel from Cyprus to Syria. The Palestine samples clearly separate into two sub-groups. Arguments are presented suggesting that this indicates the ware from the two sub-groups was made at different times. The Cyprus group provides tentative evidence of several sites of manufacture on the island.

Classical and Hellenistic black glaze ware in the Mediterranean: A study by epithermal neutron activation analysis

Abstract Fifteen chemical elements have been measured quantitatively by epithermal neutron activation analysis in 58 sherds of black glaze pottery found in Carthage/Tunis (23 sherds), the Athenian Agora (9 sherds), Sicily (7 sherds), and several sites in Southern Italy (19 sherds). Detailed statistical analysis of the results clearly distinguishes five separate groups: (a) one of local Carthage/Tunis origin; (b) one of probable Sicilian origin; (c) a large group of Attic origin comprising sherds found at the Athenian Agora and at Carthage/Tunis; and (d) two separate groups from S Italy.

Spallation cross sections in the system 93Nb +4He

Abstract Excitation functions were measured for six radioactive products formed in the reaction between 93 Nb and 4 He ions in the energy range 15–72 MeV. Agreement between experimental values and theoretical calculations was satisfactory only if allowance was made for pre-equilibrium (PE) nucleon emission. The compound nucleus (CN) model alone fails to account for the high energy tail in many of the excitation functions. The calculations do not give a particularly good fit for the (α, 2 p ) and (α, α′n) reactions which are very sensitive to parameters describing compound nucleus decay and the initial interaction respectively.

Rare earth yields from bombardment of tungsten targets with 24 GeV protons

Abstract Cumulative and independent yields of lanthanides have been measured in tungsten targets following 24 GeV proton irradiation. A chain yield curve in this mass region was obtained by reference to a charge dispersion curve which was constructed for A = 148 by an extrapolation technique. The FWHM of this curve was about 1·8 charge units and Zp ∼ 64·6. The mass yield curves for different proton energies have been compared and the implications for possible reaction mechanisms considered.

The chemical separation of some heavy elements from proton irradiated tungsten

Abstract A method is outlined for separating lanthanides, actinides, and the elements Os, Ir, Au, Hg, Tl and Pb together with their super heavy homologues, from about 30 g of irradiated tungsten metal. This involves anodic dissolution of the tungsten, and near qunatitative deposition of the elements of interest onto a molybdenum cathode, followed by conventional chemical separations. Overall chemical yields are given.

Recoil ranges of Tc activities from 93Nb(4He, xn) reactions

Abstract The recoil momenta of a series of technetium isotopes produced by the reactions 93 Nb ( 4 He , xn) (x = 2–5) have been measured at 38.4 and 56.8 MeV, using the thick target/thick catcher technique. The isotopes are produced by a mixture of compound nucleus (CN) and pre-equilibrium (PE) processes. The isomer ratios (of 94Tc and 93Tc) and the recoil momenta are consistent with a picture of PE reactions which involve the emission of one or more high energy neutrons, scattered mainly in the forward direction. This results in a net residual spin and a net recoil momentum which is lower than that predicted by the CN mechanism.

Study of 32P in n-irradiated ammonium hypophosphite using different analytical techniques

Abstract 32 P in n -irradiated ammonium hypophosphite has been studied by three different analytical techniques; classical aqueous, non-aqueous and thin layer chromatographic analysis, the latter using a non-aqueous solvent. A comparison of the results obtained by the three methods shows that (a) P(V) valence state is a hydrolytic product, (b) P(III) valence state arises from an independent precursor in the solid state and (c) there are at least three precursors for the P(I) valence state.

Nuclear and radiochemistry training in the UK

Nuclear and radiochemistry training in the UK is described. A brief history of some of the departments is included.