Samuel K. Allison

Lithium Ion Sources

The preparation of artificial β‐eucryptite (Li2O Al2O3 2SiO2) as a filament coating for the emission of Li+ ions is discussed. Two ion sources with their initial focusing gaps are described.

Construction and Calibration of a Cylindrical Electrostatic Analyzer

A cylindrical electrostatic deflector has been constructed with average radius 15 cm, spacing 0.5 cm and deflection 90°, in which the deflecting potential can be in the neighborhood of 50 kv. Thus protons up to 0.75 Mev can be focused. Movable slits have been incorporated in the design, and the geometry of the entrance and exit apertures of the deflecting channel is such that the stray field may be calculated analytically. This has been done for the case in which the deflecting plates are symmetrically charged above and below zero potential. The predictions have been compared with experiments on the focusing of electron beams by the instrument under controlled conditions. Agreement with the calculations is demonstrated within the accuracy of the experiments, which is about 0.3 percent.Experiments with asymmetric charging of the electrodes are reported and shown to agree with a plausible extension of the theory. Further experiments investigated the effect of small displacements of the slits from the comput...

Ten Years of the Atomic Age

Ten years have passed since the first successful nuclear chain reaction was brought under way at the University of Chicago metallurgical laboratory. We print here the recollections of two leading figures in that laboratory, Dr. A. H. Compton, then director of the Manhattan project (of which the metallurgical laboratory was a part) and now chancellor of Washington University in St. Louis, and Dr. S. K. Allison, director of the metallurgical laboratory and now director of the Institute of Nuclear Studies at the University of Chicago.

Let Us Pledge Not to Use H-Bomb First!

At the close of the recent meeting of the Physical Society in New York, twelve of the countrys prominent physicists issued the following statement:

Experiments on the Efficiencies of Production and the Half-Lives of Radio-Carbon and Radio-Nitrogen

These experiments were performed at the Cavendish Laboratory with the high voltage apparatus of Cockcroft and Walton and may be considered as a continuation of the experiments of Cockcroft, Gilbert and Walton on the production of induced radioactivity by high velocity protons and deuterons.

Note on the laboratory to centre-of-mass transformation of particle distributions continuous in energy

Abstract It is noted that the Jacobian determinant for the transformation of d2σ/dωdE from the laboratory to the centre-of-mass coordinate systems is simply (νmC/νmL), the ratio of the centre-of-mass velocity of particle m in the continuum to its velocity observed in the laboratory. It is shown that the numerical factors needed for such a transformation can be read from tables of the function F(x, y) = (1+x 2 −2x cos y) 1 2 and its square.