No abstract

Proton-proton scattering between 200 and 300 kev has been studied as a function of energy and of angle. The results are in good agreement with Breit's calculations based on a square well proton-proton interaction potential of e 2 /mc 2 radius and 10.500 Mev depth. The scattering chamber was isolated from the accelerating tube by a differential pumping system. Scattered protons were detected by Geiger-Klemperer proportional counters filled with purified hydrogen. Two separate counters connected to similar amplifier-recorder circuits detected simultaneously protons scattered at different angles from the beam, and the ratio of scattering at these angles was calculated directly. Tests of the performance of the counters are given. Two different scattering chambers yielded similar results.

NOTICE This document contains information of preliminary nature. It is subject to revision or cor.re.c.tion and therefore does not represent a final report.On loan from ERDA. Now associated with the CRBR Project Office in Oak Ridge, Tennessee.

An electron synchrotron, capable of accelerating electrons to energies of 300 Mev, which has been in operation for some time at the Research Laboratory, General Electric Company, is described. This machine uses no iron to produce the magnetic guide field. Electrons are injected at an energy of 100 kev, accelerated to 4 Mev by betatron action, and to 300 Mev by synchrotron action. The magnetic fields for the betatron and synchrotron guide fields are produced directly by large currents flowing in coils suitably disposed near the electron orbit. The orbit diameter is 48 in. and a field of 16 000 oersteds at the orbit is produced by a current pulse with an amplitude of 26 000 amperes. The entire coil system, together with the radio-frequency resonator and injector, is located in a vacuum. The repetition frequency is 15 pulses/sec, and the x-ray beam from an internal target has an intensity of about 2×1010 equivalent quanta/min through a collimator which transmits about 60% of the total beam.

Tentative Theory of NovaeAs has been indicated by the author, 1 a star model having an ordinary thermonuclear source of energy must show a steady increase with time in luminosity and effective temperature, moving slowly upward along the main sequence of the Hertzsprung-Russell diagram. At the point of maximum luminosity all hydrogen will be finally used up and the star will be suddenly deprived of any source of nuclear energy. At the succeeding stages of its evolution we should expect a progressive contraction, the radiation being supplied by utilizing gravitational energy only. However at this turning point of evolution a redistribution of mass in the stellar interior must take place (from "point source" to "contractive" distribution). The gravitational energy liberated in such a redistribution is likely to cause a sudden short increase of luminosity and it is possible that such phenomena may account for the explosions of stars known as novae. From this point of view the observed pre-nova stage of the star should correspond to a vanishing hydrogencontent and should correspondingly possess a luminosity about a hundred times larger than that of a normal star of the same mass. The history of the star after the contraction has started will depend essentially on its mass. For masses smaller than the critical mass of Chandrasekhar-Landau (about 3.2 sun masses) the contraction will lead through all stages of hot and dense stars to the well-known type of white dwarfs, having a degenerated electron gas inside and very small energy production. For larger masses the formation and growth of a neutron core, representing a practically unlimited,source of energy, should be expected. The growth of such a core, accompanied by increasing energy liberation (and probably expansion of the atmos-|Mw. FIG. 1. Tracks of novae and supernovae in Hertzsprung-Russeldiagram. Broken lines and empty circles-hypothetical.phere), may bring the star into the Giant branch of the H-R diagram. The explosion of massive stars thus will lead to extremely bright novae and might be identified with the so-called super-novae of Baade and Zwicky. 2 We see from Fig. 1, where the tracks of the explosions of various novae with known absolute magnitudes 3 are schematically shown in the frame of the H-R diagram, that there is no marked gap in intensity between ordinary novae and the so-called super-novae. The hypothetical pre-nova stages of super-novae (indicated by empty circles) are visually too faint (w v is-18.5 and 19.5) to be observed against the background of an extra-galactic nebula. We see that stars of small initial luminosity, after passing through the maximum (average increase 11 magnitudes) come finally to the region of higher effective temperatures (i.e., smaller radii) in agreement with the above theoretical considerations. However the "anomalous" Nova Carinae (1843) which, judging from its initial luminosity, possesses the largest mass of all observed novae, behaves in a rather different way, returning to its initial spectral class and radius....