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Tungsten Investigations in the Republic of Argentina, 1942-43

Description: From foreword: This is a progress report describing four tungsten mines in the Republic of Argentina that were examined between October 1942 and May 1943. The work leading to this report was carried on by the Geological Survey, United States Department of the Interior, and Direcci6n de Minas y Geologia, Ministerio de Agricultura de la Republica Argentina. This work was part of a larger cooperative program sponsored by the Interdepartmental Committee on Scientific and Cultural Cooperation and was carried on under the auspices of the United States Department of State. It is hoped that this cooperative work will be continued, for it is not only of direct practical use to miners but of high scientific interest.
Date: 1947
Creator: Smith, Ward C. & González, E. M.
Item Type: Report

Excitation Function of the Reaction C12(n,2n)C11 at High Energies

Description: The excitation curve for the reaction C{sup 12}(n,2n)C{sup 11} has been calculated for energies up to 100 Mev. The calculations were done as described in the preceding letter for the similar reaction of C{sup 12} under proton bombardment. The results of the calculations for 50% charge exchange are shown in Figure 1. The calculated cross section for the reaction at 90 Mev is: .011 barns for 100% charge exchange and .013 barns for 50% charge exchange. The experimental value is 0.025 {+-} .004 barns. The ratio of the cross section of the reaction C{sup 12}(pnpn)C{sup 11} to the cross section of the above reaction at 90 Mev is 5.8 for 100% charge exchange and 3.8 for 50% charge exchange. The experimental ratio is 2.7 at 90 Mev. This difference in cross sections between the two reactions is established by two factors. Firstly, there is the part played by charge exchange in the C{sup 12}(pnpn)C{sup 11} reaction which leads to excited N{sup 12} with the subsequent boiling off of a proton, while a similar exchange process cannot take place for the C{sup 12}(n2n)C{sup 11} reaction. Secondly, there is the difference between the contributions of the knock out process as a result of the difference in the n - p and the n - n cross sections, which favors the p + C{sup 12} knock out reaction. It will be noted that the parts of the reactions which go through excited C{sup 12}, while practically equal, are so small that they do not greatly affect either reaction. Although the results of these calculations do not agree too closely with the experimental results, the results are probably as good as are to be expected because of the crudity of the assumed model. The results do, though, seem to give a good qualitative picture ...
Date: November 1, 1947
Creator: Heckrotte, Wolff & Wolff, Peter
Item Type: Report

Excitation Function of the Reaction C12(p,pn)C11 at High Energies

Description: Chupp and McMillan have recently measured the excitation curve for the reaction C{sup 12}(pnpn)C{sup 11} at high energies. Using the model of the nucleus described by Serber, the excitation curve of the above reaction has been calculated for energies up to 100 Mev. The excitation of the nucleus is determined on the basis that the incident proton makes individual collisions with the nucleons, the transferred energy exciting the nucleus. n-p collisions are taken to be three times more probable than n-n or p-p collisions. Charge exchange is assumed. The calculations were made for both 50% and 100% charge exchange. The decay of the excited nucleus is treated by the usual evaporation mode.
Date: November 1, 1947
Creator: Heckrotte, W. & Wolff, Peter
Item Type: Report

Electronic Circuits Lectures

Description: The two-electrode vacuum tube, or diode, consists of an electron-emitting cathode surrounded by a positive anode (plate). A plot of plate current (i{sub b}) vs plate voltage (e{sub b}) is shown. At low anode voltages, the anode current is limited by the repelling effect that the negative electrons already in the space have on the electrons just being emitted (space-charge effect). When a full space charge is present, the plate current depends upon the plate voltage according to Childs law: i{sub b} {approx} e{sub b}{sup 3/2}. Increasing the plate voltage eventually results in an electron flow equal to total cathode emission, after which further increases in anode voltage will produce practically no additional current (voltage saturation). However, for high field stresses, additional electrons are pulled out of the cathode (field emission), increasing the current even further.
Date: December 1, 1947
Creator: Mozley, Robert
Item Type: Report

Diffraction Effects in Neutron Attenuation Measurements

Description: All errors due to diffraction effects in a neutron attenuation experiment are computed. Also a special experiment to measure the forward intensity of diffracted neutrons from lead and copper is described, and the results given. These agree with the theoretical values.
Date: November 1, 1947
Creator: Sewell, D.C. & McMillan, E.M.
Item Type: Report

Progress Report for October 1947, Physics Section

Description: This summary discusses the following topics: (1) 184-inch cyclotron program; (2) a 60-inch cyclotron program; (3) synchrotron program; (4) Linear accelerator program; (5) Experimental physics, experiments with the 184-inch cyclotron, fast neutron scattering, and neutron-proton scattering; (6) Theoretical physics; and (7) isotope research program.
Date: October 1, 1947
Creator: Brobeck, W.M.; Hamilton, J.G.; Martin, M.; Alvarez, L.W.; Thornton, R.L.; Serber, R. et al.
Item Type: Report

Proton Angular Distribution for 90 Mev Neutron-proton Scattering

Description: The angular distribution of the recoil protons in neutron-proton scattering at 90 Mev has been measured for angles between 5{sup o} and 65{sup o} from the direction of the neutron beam. The neutrons were produced by stripping 190 Mev deuterons in a 1/2 inch Be target in the 184-inch F.M. cyclotron. R. Serber has calculated the neutron energy distribution; it has a peak at 90 Mev and a half width of 27 Mev. This distributiQn has been checked experimentally for the neutrons by Wilson Powell and by W.Chupp, E.Gardner, and T.B.Taylor for the protons also produced by stripping. The neutrons were collimated by a two-inch hole through 8 feet of concrete. Thin paraffin scatters of known hydrogen and carbon content were used; the number of protons arising from neutron-carbon and neutron-air reactions was determined by using pure carbon scatters and by making blank runs. The scatters were placed in the beam outside of the concrete shielding at a point approximately 52 feet from the cyclotron target. The scattered protons were detected by a telescope of four proportional counters used in coincidence, and set at a constant distance from the scatterer but at a varying angle from the neutron beam. A copper absorber was placed between the scatterer and the counters. The thickness of the absorber was adjusted for each angle so that only protons scattered by incident neutrons of energy greater than 66 Mev could be counted. It was found that the results did not depend on whether the absorber was placed in front of all four counters, or between the first two. The beam was monitored by placing a second one inch piece of paraffin in the neutron beam and measuring the protons scattered from it by means of two additional proportional counters. Fig. 1 is a plot of ...
Date: November 3, 1947
Creator: Hadley, James; Leith, Cecil E. & York, Herbert F.
Item Type: Report

Progress Report for 1947

Description: The year 1947 has witnessed the dawn of a new era of atomic science, a flowering of fundamental knowledge of the nature of matter which appears to be unsurpassed even by that period of the 1930's which led to the age of plutonium. A great new cyclotron, an atom-smasher ten times more powerful than the one which brought plutonium into the world, has carried mankind over a new horizon of sub-atomic space. It has brought scientists at last to grips with the infinitely small and rapid forces, until now beyond reach, which operate within the incredibly tiny distances of nuclear space. On the new energy frontier created by the giant machine, now laws govern nuclear reactions. methods are at hand, heretofore unavailable, which permit the measurement and determination of the nature of sub-atomic forces. Under ultra-high energy bombardment, the nucleus presents a different appearance from the nucleus of Bohr and Rutherford, the nucleus of atomic energy fission. The new exploration of the atom has been sponsored by the Atomic Energy Commission with the giant, new 4000-ton cyclotron in the Radiation Laboratory of the University of California. This is the thirdmajor machine built by the Director of the Laboratory and inventor of the cyclotron, Professor Ernest O. Lawrence. Whether the new knowledge will be of immediate practical consequence cannot now be predicted. Nor could Professor Lawrence predict, when in 1934 he established a new atomic energy range for that day with his first cyclotron, that the fundamental knowledge he pursued would be climaxed with the discovery of plutonium. What can be predicted is this: without the new basic knowledge, practical atomic developments of the future would be limited to the applicability of the fundamental information which made possible the initial release of atomic energy. In short, the nation's atomic potential has ...
Date: November 1, 1947
Creator: Authors, Various
Item Type: Report

Summary of the Reseach Progress Meeting

Description: A 1,000 Mev synchrotron is under construction. The magnet will be a ring magnet containing about 900 tons of steel. The plates are of 1.2 inch steel with a 0.1 percent carbon content. A diagram of the cross section of this magnet is given in Figure 1. The design of the vacuum chmnber presents some difficulties since the space behind the gap is not large enough to permit easy access to the windings and to the vacuum space behind the gap. The field strength at the gap is 15,000 gauss with a 1 sec. rise time. A d.c. generator of 1,000 v and 10,000 amps and a flywheel will be used to energize the magnet and store the energy. Plans for the vacuum system are not complete, but probably a porcelain system will be used. This will reduce the gap quite considerably. It is planned to inject at 3,000 volts. The energy added to be about 200 ev per revolution. The frequency range is 250 kc/sec to 10 mc/sec; the power required is 10 Kw. A diagrammatic view of the electrical arrangement of the r.f. system is given.The variable inductance is a coil tipped at variable pitch into a pool of mercury. The energy is supplied by four 3J160E tubes. The frequency must be accurate to 0.1 percent at the time of injection and after that 1 percent is sufficient. This is to be accomplished by means of a peeking coil in the field. The injection period is 100 microseconds. It is planned to use a 0.5 Mev d.c. Philips set to supply the injection voltage.
Date: November 1, 1947
Creator: O'Brien, Inez
Item Type: Report

Summary of the Research Progress Meeting

Description: This summary discusses the following topics: (1) Neutron Scattering. By R. Hildebrand. A series of measurements have been made of the angular distribution of neutrons scattered from small spheres of various materials placed in the neutron beam of the l84-inch cyclotron. The scattered neutrons were detected by copper covered carbon detectors placed in a symmetrical arrangement about the scatterer. The carbon detectors, which wore activated by the neutrons through the C{sup 12}(n, 2n)C{sup 11} reaction, were counted using an arrangement involving four counting tubes. The copper around the detectors served the purpose of stopping any protons. A carbon disk monitor was placed at the collimating channel in the cyclotron shield. This disk Was also counted by the same arrangement. (2) Electrical Resistance of the Blood. By R. Rosenthal. It has been found that animals exposed to total body irradiation developed in their blood an anti-coagulant called heparin. This substance, which can be produced synthetically, has the property of prolonging the clotting time of the blood. In an article which appeared in 'Science' some work was reported on the variation of the electrical resistance of the blood with the amount of heparin present, If some simple relationship could be found between the electrical resistance and the amount of heparin in the blood it might be possible to get a measure of the total radiation to which the animal had been subjected. In the work mentioned above the electrical resistance was found to vary with time for normal human blood and blood from people treated with heparin in the manner shown in Figure. 3. The clotting time was the same for both cases. (3) l84-inch Deflector. By J. Vale. In an effort to determine the shape of the deflected deuteron beam as it emerges from the 1/8 inch aluminum window in the ...
Date: November 1, 1947
Creator: Wakerling, R.K.
Item Type: Report

Interium Report on An Exact Analysis of a Limited Plane Plasma in a Magnetic Field

Description: Prior analyses of a plasma in a magnetic field have been limited, as far as the writer is aware, to cases in which the relative change in field over the orbital distance and the relative change in ion concentration are both small, or in which the relations have been viewed in a purely hydrodynamical way. The first approach excludes cases which can be of considerable interest, for it fails for a plasma edge. The second loses all sight of the structure imposed by the orbital motions.
Date: January 1, 1947
Creator: Tonka, Lewi
Item Type: Report

Phosphorus Turnover and Photosynthesis

Description: The participation of phosphorus in biological oxidation-reduction reactions of the type found in glycolysis ADP {ne} PO{sub 4}H{sup -} + 3-phosphoglyceraldehyde + DPN{sup +} = 3-phosphoglycerate{sup -} + 2H{sup +} + DPHN + ATP has suggested theories in which similar reactions are proposed for photosynthesis. In these theories the reducing power of photosynthesis is utilized not only for reduction of carbon dioxide but also, by means of coupled oxidations, for the generation of high-energy phosphate bonds, or in the last reference directly for the generation of high-energy phosphate. Since in these theories acyl phosphate is formed from inorganic phosphate, they are amenable to proof without isolation of particular intermediates, by means of radioactive phosphorus. It would be expected that the rate of conversion of inorganic phosphate to organic phosphate would be greater in light than in the dark. They have investigated this possibility under a variety of conditions and are unable to substantiate the theories.
Date: November 1, 1947
Creator: Calvin, Melvin
Item Type: Report

Phosphorus Turnover and Photosynthesis

Description: The participation of phosphorus in biological oxidation-reduction reactions of the type found in glycolysis ADP + PO{sub 4}H{sup -} + 3-phosphoglyceraldehyde + DPN{sup +} = 3-phosphoglycerate{sup -} + 2H{sup +} + DPNH + ATP has suggested theories in which similar reactions are proposed for photosynthesis. In these theories the reducing power of photosynthesis is utilized not only for reduction of carbon dioxide but also, by means of coupled oxidations, for the generation of high-energy phosphate bonds, or in the last reference directly for the generation of high-energy phosphate. Since in these theories acyl phosphate is formed from inorganic phosphate, they are amenable to proof without isolation of particular intermediates, by means of radioactive phosphorus. It would be expected that the rate of conversion of inorganic phosphate to organic phosphate would be greater in light than in the dark. They have investigated this possibility under a variety of conditions and are unable to substantiate the theories.
Date: November 1, 1947
Creator: Aronoff, Sam & Calvin, Melvin
Item Type: Report

The Eight New Synthetic Elements

Description: In an early continuation of the investigation of the radioactive isotopes of element number 43 (technetium) Segre and Seaborg produced by the deuteron and neutron bombardment of molybdenum the isotope Tc{sup 99}, which they observed to decay by means of an isomeric transition with a half-life of 6.6 hours to a lower isomeric state with a half-life greater than 40 years. The upper isomeric state of this isotope was observed by Segre and C. S. Wu to be produced in the fission of uranium and more recently R. P. Schumann and also D. C. Lincoln and W. H Sullivan working on the Plutonium Project of the Manhattan District have independently observed the beta-particles of half-life about 10 years due to the lower isomeric state. Later work by E. E. Motta and G. E. Boyd sets a more accurate value of 9.4 x 10{sup 5} years for this half-life. Since this isotope is formed in rather large amounts, namely, a fission yield of 6.2%, in the slow neutron induced fission of uranium it is now possible to isolate technetium in weighable amounts and in rather substantial quantities. For example, a uranium pile operating at a power level of 10{sup 5} kw would produce about four grams of technetium, as the isotope T{sup 99}, per day. With such a long half-life the radioactivity associated with convenient amounts (some mg.) would be so small in intensity as to not create a problem provided reasonable care in handling were exercised.
Date: November 1, 1947
Creator: Seaborg, Glenn T.
Item Type: Article

Diffraction Effects in Neutron Attenuation Measurements

Description: All errors due to diffraction effects in a neutron attenuation experiment are computed. Also a special experiment to measure the forward intensity of diffracted neutrons from lead and copper is described, and the results given. These agree with the theoretical values.
Date: November 1, 1947
Creator: McMillan, E.M. & Sewell, D.C.
Item Type: Report

Preparation of 1-C14-Propene-1 and the Mechanism of PermanganateOxidation of Propene

Description: 1-C{sup 14}-propene has been prepared. The migration of the double bond under a variety of experimental conditions in the preparation of propene has been investigated. The mechanism of the permanganate oxidation of the labeled propene has been examined; it has been found to proceed by several paths, the relative importance of which depends upon the experimental conditions, especially the pH.
Date: December 10, 1947
Creator: Fries, B.A. & Calvin, M.
Item Type: Report