B. J. Dropesky

A SUMMARY OF THE DECAY OF SOME FISSION PRODUCT TIN AND ANTIMONY ISOTOPES

Abstract The mass assignments, half-lives and radiation characteristics of the isobaric pairs 126Sn126Sb, 127Sn127Sb, 128Sn128Sb and 129Sn129Sb and the isotope 130Sb have been investigated. Samples of tin and antimony chemically separated from reactor-irradiated 235U were examined with β- and γ-scintillation spectrometers and β-proportional counters. The main results of this programme are summarized in the present report.

Note on the decay of the new nucleide Cr56

Abstract Cr 56 has been identified and was found to decay with a 5.94 min half-life. A 1.5-MeV β -group and a 26-, 83-keV γ -ray cascade were observed in this decay.

Interlaboratory comparison of spallation-reaction cross sections for iron and copper with 590-MeV protons☆

Abstract Three sets of thin foils of carbon, aluminum, iron and copper have been simultaneously irradiated with 590-MeV protons. Cross sections of some of the γ-ray emitting spallation products from Fe and Cu have been measured independently by members of the three participating laboratories. The results are compared and average cross sections are given. Various sources of error common to such experiments are presented, and the steps taken to minimize them in this work are discussed.

Short-lived 123Sn and 125Sn from thermal-neutron fission of 235U

Abstract Isotopic separation of 40·1-min 123 Sn and 9·6-min 125 Sn from other tin fission products allowed determination of their fission yields and study of the chemical states of 123 Sn that are formed in fission. The yields determined are 0·0141±0·0012% for 40·1-min 123 Sn, 0·0014% for 9·6-min 125 Sn, ∼0·062% for 2·1-hr 127 Sn, and ∼0·30% for 128 Sn. It was also determined that 54±2% of 40·1-min 123 Sn is formed in the +2 oxidation state (the rest being in the +4 state) in an aqueous solution containing 1·0 M HCl, 0·21 M HF, 0·013 M UO 2 2+ , 0·011 M Sn(II), and 0·011 M Sn(IV). This value for 123 Sn is larger than that for 27-hr 121 Sn formed under the same chemical conditions and shows that the fraction of tin formed in the +2 state by beta decay is not a constant but depends on the characteristics of the beta decay process.

Fragmentation of gold by pions and protons

Abstract The excitation function for the formation of 24 Na in the interaction of gold with protons has been determined between 200 and 800 MeV and the 24 Na cross section measured for 294 MeV π + .

Rotating-wheel detector system for measuring millisecond half-life high-energy β emitters☆

Abstract In order to detect the 11 ms 12N activity produced in the pion single charge exchange reaction 12C(π+, π0)12N, a high-energy β-particle telescope was designed, constructed, and used successfully in the high-background field of γ rays, neutrons, and high-energy charged particles at LAMPF. A high-speed rotating wheel served both as a target and as a means of transporting the short-lived activity to an array of telescopes for counting. Monte Carlo calculations were carried out to optimize the design parameters of the telescope and to estimate counting efficiencies.

Excitation functions of pion single charge exchange reactions in /sup 27/Al, /sup 45/Sc, and /sup 65/Cu

The cross sections for the pion single charge exchange reactions /sup 27/Al(..pi../sup -/,..pi../sup 0/) /sup 27/Mg, /sup 45/Sc(..pi../sup +/,..pi../sup 0/) /sup 45/Ti, and /sup 65/Cu(..pi../sup -/,..pi../sup 0/) /sup 65/Ni were measured at pion kinetic energies from 80 to 400 MeV by activation techniques. The excitation functions measured for these target nuclei do not show any structure near the (3,3) resonance, but rather, all exhibit a monotonic decrease in cross section over this energy range, proportional to T/sub ..pi..//sup -1/. Theoretical predictions based on the impulse approximation with the Fermi gas model show a minimum near the (3,3) resonance, in disagreement with these experimental results.