S.G. Thompson

Application of High-Resolution Semiconductor Detectors in X-ray Emission Spectrography

Solid-state devices developed primarily for nuclear gamma spectroscopy have many potential uses in x-ray analysis.

The New ELement Mendelevium, Atomic Number 101

We have produced and chemically identified for the first time a few atoms of the element with atomic number 101. Very intense helium ion bombardments of tiny targets of 99{sup 253} have produced a few spontaneously fissionable atoms which elute in the eka-thulium position on a cation resin column.

Spontaneous fission half lives of 254Cf, 255Fm, and 250Cf

Abstract The remeasured spontaneous-fission half-life of 254 Cf is 60·5 ± 0·2 days. The spontaneous-fission half-life of 255 Fm is determined to be (0.1 +0.6 −0.3 × 10 4 years. The remeasured alpha-to-fission ratio in the decay of 250 Cf is (1330 ± 45). The remeasured eletron-capture/β-decay branching ratio in 254 m Es is (0·078 ± 0·006) per cent.

Spallation reactions of californium-252 with helium ions

Cross sections were determined for Cf/sup 252/( alpha ,xn) and ( alpha ,pxn) reactions. The product of the ( alpha ,3n) reaction, Fm/sup 253/, was found to have a half life of 1.0 plus or minus 0.2 days and the most abundant alpha -particle energy was 6.95 plus or minus 0.05 Mev. From the decay of Fm/ sup 253/, the electron-capture daughter Es/sup 253/ was found to have an electron- capture to alpha -decay branching ratio of 8.5 plus or minus 1.0. (C.J.G.)

Electron capture half-life of 243Cm

Abstract A sample containing 243 Cm was milked for Am after a known growth period. From the relative activity intensities and mass ratios in the curium sample and the amount of 243 Am which grew in, a value of 1·0 ± 0·1 × 10 4 years was calculated for the electron capture half-life of 243 Cm.

Magnetic Steering Device for Electron Coincidence Experiments

The highly convergent fringing field produced by a 100 kVA C‐magnet has been used to guide electrons emitted at a source around a 90° arc to a Si(Li) detector. This source‐detector configuration is often desirable because it enables the electron detector to be effectively shielded from other radiations emitted at the source. The electron motion in this device consists of a superposition of a trochoidal motion and a vertical oscillation through the magnet symmetry plane. The high detection efficiency of the system (∼5%) makes it particularly well suited for applications in electron coincidence experiments. Utilization of the device in a study of internal conversion in coincidence with fission is described, and several other applications are suggested.

γ-ray spectrum of Sb131

Abstract The γ-spectrum of 25·5 ± 2 min Sb 131 was investigated with a scintillation spectrometer. γ-rays with energies of 0·645 and 0·950 MeV were observed, and their absolute abundances determined.

DISCOVERY OF A NEW FERMIUM ISOTOPE

Abstract A new spontaneous-fission activity has been observed in a fermium fraction separated from 120 mg of mixed curium isotopes which had been subjected to an integrated flux of 2·4 × 10 22 neutrons per cm 2 at the Materials Testing Reactor, Idaho Falls Idaho (MTR). A least-squares analysis of the spontaneous-fission decay data yielded a half-life of 10·8 days with a standard deviation of about ( +2.2 −1.8 days. An estimated half-life of (11 +10 −6 days is reported here. The mass assignment is uncertain, but limited to A = 258 or 257.

Evidence for Subshell at N = 152

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Californium Isotopes from Bombardment of Uranium with Carbon Ions

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