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Spontaneous Fission

Description: The first attempt to discover spontaneous fission in uranium was made by Libby, who, however, failed to detect it on account of the smallness of effect. In 1940, Petrzhak and Flerov, using more sensitive methods, discovered spontaneous fission in uranium and gave some rough estimates of the spontaneous fission decay constant of this substance. Subsequently, extensive experimental work on the subject has been performed by several investigators and will be quoted in the various sections. Bohr and Wheeler have given a theory of the effect based on the usual ideas of penetration of potential barriers. On this project spontaneous fission has been studied for the past several years in an effort to obtain a complete picture of the phenomenon. For this purpose the spontaneous fission decay constants {lambda} have been measured for separated isotopes of the heavy elements wherever possible. Moreover, the number {nu} of neutrons emitted per fission has been measured wherever feasible, and other characteristics of the spontaneous fission process have been studied. This report summarizes the spontaneous fission work done at Los Alamos up to January 1, 1945. A chronological record of the work is contained in the Los Alamos monthly reports.
Date: November 22, 1950
Creator: Segre, Emilio
Partner: UNT Libraries Government Documents Department

Antinucleons

Description: The idea of ''antiparticles'', as is well known, originated with Dirac, who in establishing the relativistic equations for the electron noted that besides the solutions corresponding to ordinary electrons there were also ''unwanted solutions'' corresponding to particles of electronic mass but of charge +e instead of the electronic charge - e. The discovery of the positron by CD Anderson offered a brilliant experimental confirmation of Dirac's prediction and gave the first example of an ''antiparticle.''
Date: April 1, 1958
Creator: Segre, Emilio
Partner: UNT Libraries Government Documents Department

Experiments of the Effect of Atomic Electrons on the DecayConstant of Be7

Description: In an attempt to detect a possible influence of the atomic electrons on the radioactive decay constant of Be{sup 7} they have measured {lambda}{sub Be}-{lambda}{sub BeO} and found (-3.0 {+-} 1.8) 10{sup -4} {lambda}{sub Be}. They describe also a method to measure mean lives of radioactive substances in a time short compared with the mean life.
Date: July 1, 1948
Creator: Segre, Emilio & Wiegand, Clyde
Partner: UNT Libraries Government Documents Department

The Mechanism of Proton Polarization in High-EnergyCollisions

Description: Recently experimental evidence has accumulated showing that high-energy collisions of protons with various nuclei induce a considerable polarization in proton beams, and a mechanism has been proposed to account for this effect.
Date: June 9, 1954
Creator: Chamberlain, Owen; Segre, Emilio; Tripp, Robert; Wiegand, Clyde & Ypsilantis, Thomas
Partner: UNT Libraries Government Documents Department

Observation of Antiprotons

Description: One of the striking features of Dirac's theory of the electron was the appearance of solutions to his equations which required the existence of an antiparticle, later identified as the positron.
Date: October 19, 1955
Creator: Chamberlain, Owen; Segre, Emilio; Wiegand, Clyde & Ypsilantis,Thomas
Partner: UNT Libraries Government Documents Department

Antiprotons

Description: Since the development of Dirac's theory of the electron and the brilliant confirmation of one of its most startling predictions by the discovery of the positron by Anderson, it has been assumed most likely that the proton would also have its charge conjugate, the antiproton. The properties that define the antiproton are: (a) charge equal to the electron charge (also in sign); (b) mass equal to the proton mass; (c) stability against spontaneous decay; (d) ability to annihilate by interaction with a proton or neutron, probably generating pions and releasing in some manner the energy 2 mc{sup 2}; (e) generation in pairs with ordinary nucleons; (f) magnetic moment equal but opposite to that of the proton; (g) fermion of spin 1/2. Not all these properties are independent, but all might ultimately be subjected to experiment.
Date: November 29, 1955
Creator: Chamberlain, Owen; Segre, Emilio & Wiegand, Clyde
Partner: UNT Libraries Government Documents Department

Experiments on Antiprotons: Antiproton-Nucleon CrossSections

Description: In this paper experiments a r e reported on annihilation and scattering of antiprotons in H{sub 2}O , D{sub 2}O, and O{sub 2}. From the data measured i t i s possible to obtain an antiproton-proton and a n antiproton-deuteron c r o s s section a t 457 Mev (lab). Further analysis gives the p-p and p-n c r o s s sections a s 104 mb for the H-p reaction c r o s s section and 113 mb for the p-n reaction c r o s s section. The respective annihilation cross sections a r e 89 and 74 mb. The Glauber correction necessary in order to pass from the p-d to the p-n c r o s s section by subtraction of the p-p c r o s s section i s unfortunately large and somewhat uncertain. The data a r e compared with the p-p and p-n c r o s s sections and with other results on p - p collisions.
Date: July 22, 1957
Creator: Chamberlain, Owen; Keller, Donald V.; Mermond, Ronald; Segre,Emilio; Steiner, Herbert M. & Ypsilantis, Tom
Partner: UNT Libraries Government Documents Department

Antiproton Interaction Cross Sections

Description: Using the 1.19-Bev/c antiproton beam recently discovered at the Berkeley Bevatron of the University of California, we have measured the attenuation cross section in beryllium and copper. These cross sections are compared to attenuation measurements made with the same geometry using positive protons of the same incident energy (497 MeV).
Date: February 27, 1956
Creator: Chamberlain, Owen; Keller, Donald V.; Segre, Emilio; Steiner,Herbert M.; Wiegand, Clyde & Ypsilantis, Tom
Partner: UNT Libraries Government Documents Department

Antiproton Star Observed in Emulsion

Description: In connection with the antiproton investigation at the Bevatron we planned and carried out a photographic-emulsion exposure in a magnetically selected beam of negative particles. The magnetic system was identical to the first half (one deflecting magnet and one magnetic lens) of the system used in the antiproton experiment of Chamberlain, Segre, Wiegand, and Ypsilantis. The selected particles left the copper target in the forward direction with momentum 1.09 Bev/c.
Date: December 1, 1955
Creator: Chamberlain, Owen; Chupp, Warren W.; Goldhaber, Gerson; Segre,Emilio; Wiegand, Clyde; Amaldi, E. et al.
Partner: UNT Libraries Government Documents Department

P-P Elastic and Charge-Exchange Scattering at about 120 Mev

Description: Observation of antiprotons in a propane or hydrogen bubble chamber offers the possiblity of studying several phenomena for which counter or photographic emulsion techniques are less suitable. Because there is a high ratio of pions, muons, and electrons to antiprotons in the available momentum-analyzed beams, these beams cannot be used in the bubble chamber without an initial purification, which increases the ratio of antiprotons to other particles. Such a purification has been achieved by utilizing the difference in rates of momentum loss in absorbers between antiprotons and other particles. The principle of the method is to pass a momentum-analyzed beam through an absorber. Since particles of unequal mass do not have the same specific ionization they lose different amounts of momentum, and a further magnetic deflection suffices to separate the particles physically according to mass. In this experiment a desirable momentum for antiprotons entering the bubble chamber was 684 Mev/c; however, at this momentum the ratio of undesirable particles to antiprotons at the target where they are produced is about 6 x 10{sup 5}. By starting with 970-Mev/c particles at the target and using the method of differential absorption, they decreased the ratio of undesirable particles (87% {mu}{sup -}, 105 {pi}{sup -}, 3% e{sup -}) to antiprotons entering the bubble chamber at 684 Mev/c to 1.5 x 10{sup 4}. A system of counters indicatd when an antiproton entered the bubble chamber, and although the chamber was expanded on every Bevatron pulse, the lights were flashed and the chamber photographed only when an antiproton entered.
Date: March 28, 1958
Creator: Agnew Jr., Lewis; Elioff, Tom; Fowler, William B.; Gilly, Louis; Lander, Richard L.; Oswald, Larry et al.
Partner: UNT Libraries Government Documents Department