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Neutron Deficient Isotopes of Tellurium and Antimony

Description: While investigating the relative yields for the many reactions resulting from the irradiation of antimony with 200-Mev deuterons in the Berkeley 184-inch cyclotron several previously unreported isotopes of tellurium and antimony were encountered. The tellurium fraction when followed on a thin mica window counter could be resolved into half-life periods of 2.5 hrs, 6.0 days and a small amount of a long-lived component. The 2.5 hour period has not been further characterized with respect to mass number or mode of decay other than to note that the radiation is predominantly electrons. The 6.0-day period is accompanied by positrons which were shown to be due to a 3.5 minute antimony daughter which is undoubtedly the same activity assigned to Sb{sup 118} by Risser, Lark-Horowitz and Smith. The positron energy was found to be 3.1 {+-} 0.2 Mev by absorption in berylllum and from the end point of the energy distribution curve taken with a low-resolution beta-ray spectrometer. Gamma activity is also present with this period. The 6.0-day tellurium showed a high abundance of x-rays, little or no conversion electrons and some gamma-ray activity which could be due to the 3.5 minute antimony daughter. The tellurium fraction contained another component of 4.5-day half-life which could not be observed in the decay curve because of its low abundance but which was detected by means of its 39-hour antimony daughter. The 39-hour antimony showed x-rays of tin (critical absorption with cadmiium, silver and palladium), no detectable hard radiation or electrons and is apparently identical with an activity recently assigned to Sb{sup 119} by Coleman and Pool.
Date: January 1, 1948
Creator: Lindner, M. & Perlman, I.
Item Type: Report

The Estimation of Heats of Formation

Description: The procedure for estimation of heats of formation of compounds is illustrated by discussion of compounds of several of the elements of the actinide series. The procedure is particularly suited for lanthanide and actinide elements because of the similarity of the ionic radii and types of bonding.
Date: February 2, 1948
Creator: Brewer, Leo
Item Type: Report

Excitation Curves of C12(p,pn)C11 and B11(p,n)C11 up to 32 MeV.

Description: The reaction C{sup 12} (p,pn)C{sup 11} which has been studied by McMillan, Chubb and Miller for energies up to 100 Mev is an example of a reaction whose high energy behavior cannot be explained by a compound nucleus process. The purpose of the study was to investigate this reaction at the high resolution possible with the Berkeley linear accelerator near the excitation threshold. The excitation curve was obtained by stacking specially molded polystyrene (composition C{sub n}H{sub n}) foils of high uniformity and bombarding them in the proton beam. The resultant activity was then counted on a Geiger counter in standard geometry. The resultant curve is shown in Figure 1. An immediately evident feature is the sharp threshold of the reaction. The second derivative curve, illustrated in Figure 2, of the excitation shows an RMS width of 270 kV, the theoretical straggling width due to the foils of 170 kv, and the remaining width in accordance with the energy spread of approximately {+-} 100 kv half width of the linear accelerator. The data therefore are compatible with a sharp threshold for this reaction. This curve, incidentally, furnishes independent evidence as to the energy homogeneity of the linear accelerator beam.
Date: April 20, 1948
Creator: Phillips, Robert & Panofsky, Wolfgang K.H.
Item Type: Report

The Half-Lives of Aluminum25 and Aluminum26

Description: The availability of separated isotopes of Mg makes it easy to determine the half life of Al{sup 26}, a member of the Wigner series which has long been suspected to have a half life of approximately 7 seconds, but which has not been confirmed because of the masking 7 second activity of Al{sup 26}. Mg{sup 24}, Mg{sup 25} and Mg{sup 26} (in the form of MgO) have been bombarded with protons from the Berkeley Linear Accelerator, with the following results: (1) Mg{sup 24} yields an activity of approximately 23 seconds half life, presumably due to Na{sup 21} from the reaction Mg{sup 24}(p,a)Na{sup 21}; (2) the Mg{sup 25} yields an activity of approximately 8 seconds half life, which they assign to the reaction Mg{sup 25}(p,n)Al{sup 25}; and (3) The Mg{sup 26} yields an activity of approximately 6 seconds half life, assigned to Al{sup 26} according to a similar reaction. It seems probable therefore that the 7 seconds half life normally given for Al{sup 26} is a mixture of these two activities.
Date: April 24, 1948
Creator: Bradner, Hugh & Gow, J.D.
Item Type: Report

THE RELATION OF BACKSCATTERING TO SELF-ABSORPTION

Description: The effects of backscattering upon self-absorption correction curves are demonstrated. Data are given for the backscattering powers of several substances for the beta radiations from C{sup 14}, and for se1f-absorption of samples of barium carbonate and wax, containing C{sup 14}, mounted on aluminum.
Date: January 1, 1948
Creator: Yankwich, Peter E. & Weigl, John.
Item Type: Report

Research Progress Meeting for March 11,1948

Description: The linear accelerator is again in operation after a shutdown fore repairs and minor changes. Radiofrequency checks of the instrument were made while the Van de Graaff was open. The vacuum of the system is now very good, the base pressure being 1.7 x 10{sup -6} mm Hg with a rate of rise of 800 s/{micro}s. Some preliminary results have been obtained on the activation of carbon with protons. The experiments were done using 10 mil, 50 mg/cm{sup 2} polystyrene discs. The activation curve obtained is shown. The break shown in the curve was found on two separate runs and it yet unexplained. In another experiment a proton induced activity in nickel was found. This had a 3.3 second half-life. Positive mesons have been detected on plates exposed in the 184-inch cyclotron with an arrangement shown schematically. The beam ws allowed to strike a 1/16 inch carbon target, and the mesons, which are bent around by the magnetic field, were detected with photographic plaes placed beneath the circulating beam. A series of experiments were done in which the plates were placed at distances varying from 1-1/2 to 3/4 inch from the beam between 1/4 inch plates of copper. The plates obtained at 1 inch and 3/4 inch were so blackened as to be unusable. From the plates secuired at 1-1/4 inch Lattes has found a total of 30 positive meson tracks, of which 20 end in the emulsion. Eight of these were found to give rise to seconaries, none of which stopped in the emulsion. This work was done with 50 micron plates and will be extended using 100 micron plates. The data will be further analyzed to see if all of the positive mesons and in secondaries. The number of positive mesons produced seems to be comparable to the ...
Date: March 11, 1948
Creator: Wakerling, R.K.
Item Type: Report

Research Progress Meeting of February 19, 1948

Description: Much of the cloud chamber work has been directed toward obtaining the angular distribution of protons bombarded by deuterons from the 184-inch cyclotron. The observations have been restricted to those protons arising from neutrons of energy greater than 65 Mev. The cloud chamber used for this work is of 16-inch diruneter and employs a magnetic field of 14000 gauss. The chamber is filled with hydrogen at a pressure of 1/2 atmosphere; the vapor used is water and alchohol. Nearly 800 proton tracks were measured and calculated before analysis of the data indicated that the measuring procedure should be revised. They gave the angular and energy distributions shown in Figures 1 and 2. The discrepencies between the theoretical and experimental energy distribution of the neutrons shows that serious errors were being made. As a first check of possible sources of error, random parts of the data were remeasured. They indicated that errors in the measurements of the angles were being made that gave a mean deviation of about {+-} 2{sup o} in the beam angle and {+-} 4{sup o} in the dip angle. These errors were largest at large scatter angles. In addition, a more serious error occured in the measurements of the curvature. The mean deviation was as large as 15 percent, with many tracks having errors of 50 to 100 percent in the measured curvature. These errors were dUd to the fact that an adequate measuring technique had not been developed, that the original measuring apparatus and projector were difficult to operate, and that the cloud chamber technique had not been perfected. A systematic analysis of the errors and difficulties involved in the experiment made it evident that revisions in the technique were necessary. In view of the inaccuracy of the original measurements it is not possible to make ...
Date: February 19, 1948
Creator: Wakerling, R.K.
Item Type: Report

Research Progress Meeting of March 25, 1948

Description: This summary of the research progress meeting for March 25, 1948 covers the following topics: (1) Recent n-p scattering measurements; (2) Mass measurements of mesons; and (3) Naphthalene counters.
Date: March 25, 1948
Creator: Wakerling, R.K.
Item Type: Report

Summary of the Research Progress Meeting April 1, 1948

Description: This summary of the research progress meeting on April 1, 1948 discusses the following topics: (1) Meson fission counter; (2) Delayed neutron periods; and (3) Products of bombardment of copper with high energy deuterons and helium ions.
Date: April 1, 1948
Creator: Folden, Margaret Foss
Item Type: Report

The Fission of Thorium with Alpha Particles

Description: The fission distribution of fission of thorium with alpha particle of average energy 37.5 Mev has been measured by the chemical method. The distribution found shows that the characteristic dip in the fission yield mass spectrum has been raised to within a factor of two of the peaks compared to a factor of 600 in slow neutron fission of U{sup 235}. The raise in the deip has caused a corresponding lowering in fission yield of these elements at the peaks. The cross section for fission of thorium with 37.5 Mev alphas was found to be about 0.6 barn, and the threshold for fission was found to be 23 to 24 Mev.
Date: April 15, 1948
Creator: Newton, Amos S.
Item Type: Article

The Fission of thorium with Alpha Particles

Description: Soon after the discovery of fission, Meitner, Bretscher and Cook found differences in the decay of various chemical fractions separated from uranium irradiated with slow neutrons and thorium irradiated with fast neutrons respectively and suggested that a difference existed in the distribution of fission products in the two cases. In 1940, Turner suggested that the distribution in various modes of fission should be investigated. The fact that elements such as tin, cadmium, palladium, and silver were found in fast neutron and deuteron fission of uranium and thorium before they were found in slow neutron fission of uranium suggested that the middle region of the distribution was raised as the energy of the incident particle was increased. Since the compound nucleus formed in the fission of thorium with alpha particles is U{sup 236}, the same compound nucleus formed in the fission of U{sup 235} with neutrons, it is of interest to study the fission of thorium with alphas and compare the resulting distribution of fission products with that found with uranium with slow and thorium with fast neutrons. Any difference between the various results where the same compound nucleus is formed must be due to differences in energy content and possible differences in distribution of the nucleons in the compound nucleus at the time of fission.
Date: October 15, 1948
Creator: Newton, Amos S.
Item Type: Report

The Distribution of Radioactivity in the Mouse Following Administration of Dibenzanthracene Labeled in the 9 and 10 Positions with Carbon Fourteen

Description: Dibenzanthracene, labeled in the 9 and 10 positions with carbon fourteen has been administered to mice intravenously and by stomach tube as an aqueous colloid, and intraperitoneally, subcutaneously, and by stomach tube in tricaprylin solution. The distribution of radioactivity in the mice at various time intervals after administration of the carcinogen has been determined. The radioactivity is rapidly eliminated, largely through the feces, and ordinarily very little is absorbed. The distribution and rate of elimination depends upon the mode of administration. There is an appreciable quantity of radioactivity in tumors produced several months after a single subcutaneous injection of dibenzanthracene. There appear to be no detectable effects from the radiation of the labeled carcinogen.
Date: January 30, 1948
Creator: Heidelberger, Charles & Jones, Hardin, B.
Item Type: Article

Production of Mesons by the 184-inch Berkeley Cyclotron

Description: The authors have observed tracks which they believe to be due to mesons in photographic plates placed near a target bombarded by 380 Mev alpha particles. For a 10-minute exposure in the cyclotron, about 50 meson tracks are found along the 3-inch edge of a photographic plate. The mass has been determined by measuring the bending in the magnetic field and the range in emulsion. From the first 50 meson tracks measured they find a mass of 313 {+-} 16 electron masses. It is highly probable that these mesons are the heavy mesons described by Lattes, Occhialini, and Powell.
Date: January 1, 1948
Creator: Gardner, Eugene & Lattes, C.M.G.
Item Type: Article

Production of Mesons by the 184-inch Berkeley Cyclotron Part I. Experimental Arrangement

Description: The authors have observed traks which they believe to be due to mesons in photographic plates placed near a ta5rget bombarded by 380 Mev alpha particles. The plates used were Ilford Nuclear Research Plates, type C.2. the identification of the particles responsible for the tracks was first made on the basis of the appearance of the tracks; they show the same type of scattering and variation of grain density with residual range found in cosmic ray meson tracks and about two-thirds of them produce observable stars at the end of their range. For a 10-minute exposure in the cyclotron, about 50 meson tracks are found along the 3-inch edge of a photographic plate. Carbon, beryllium, copper, and uranium have been used so far as target materials, and all are found to give mesons. When a carbon target was bombarded with 300 Mev alpha particles, mesons were found but with reduced yield.
Date: April 1, 1948
Creator: Gardner, Eugene & Lattes, C.M.G.
Item Type: Article

The Production of Thin Be Foils

Description: A procedure for making Be foils between 10{sup -5} cm. and 10{sup -3} cm. thick, and with diameters up to an inch and a half is described, and methods of mounting these foils are indicated.The problem of making thin Be foils was presented in connection with focusing the proton beam in the Berkeley Linear Accelerator, and although the foils are not now used in the accelerator, they have proved to be quite useful as thin targets, target supports, thin windows, etc. The Be was evaporated in vacuum and deposited on a metal collector plate. The problems encountered were: (1) obtaining reproducible quantities of evaporated Be; (2) stripping of Be from the collector plates; (3) preventing curl of the foils when they were stripped; and (4) mounting the foils.
Date: March 18, 1948
Creator: Bradner, Hugh
Item Type: Report

Products of High-Energy Deuteron and Helium Ion Bombardments of Copper

Description: The identity and relative yields of about twenty of the radioisotopes produced by the bombardment of natural copper with 190 Mev deuterons and 380 Mev helium ions have been determined. Two previously unreported isotopes were detected: Zn{sup 62}, decaying by orbital electron capture with a 9.5-hour half-life, and Fe{sup 52}, decaying by positron emission with a 7.8-hour half-life.
Date: March 1, 1948
Creator: Miller, D.R.; Thompson, R.C. & Cunningham, B.B.
Item Type: Report

Summary of the Research Progress Meeting

Description: This summary of the research progress meeting on March 18, 1948 covers the following topics: (1) Proton-proton scattering at 7 Mev; (2) Some animal experiments with 90 Mev neutrons; and (3) Yields of spallation products of antimony.
Date: March 18, 1948
Creator: Folden, M.F.
Item Type: Report

Summary of the Research Progress Meeting

Description: This report discusses progress on the following topics: (1) some new isotopes in the rare earth region; (2) remarks on a new alpha series; (3) solid counters; (4) naphthalene crystals have been replaced with anthracite in one of the experimental counters and some excellent results are obtained; and (5) biological experiments with the deuteron bean of the 184-inch cyclotron.
Date: April 8, 1948
Creator: Wakerling, R.K.
Item Type: Report

Studies with Colloids Containing Radioisotopes of Yttrium, Zirconium, Columbium, and Lanthanum: 1. The Chemical Principles and Methods Involved in Preparation of Colloids of Yttrium, Zirconium, Columbium, and Lanthanum

Description: For a number of investigations, including fundamental studies of radiation effects on living tissues and therapeutic utilization of radioisotopes, it is valuable to have methods for the selective localization of radioisotopes in certain tissues. Finely dispersed anhydrous chromic phosphate has been found useful by Jones, Wrobel, and Lyons in selectively irradiating the liver and spleen with p{sup 32} beta particles. The present studies, reported in this and the following communication, are concerned with methods for controlled selective localization of colloids (incorporating radioisotopes) in the liver, spleen, or bone marrow, and with an analysis of some of the factors involved in the phenomenon of localization.
Date: April 21, 1948
Creator: Gofman, John W.
Item Type: Report

Studies with Colloids Containing Radioisotopes of Yttrium, Zirconium, Columbium and Lanthaum: 2. The Controlled Selective Localization of Radioisotopes of Yttrium, Zirconium, Columbium in the Bone Marrow, Liver and Spleen

Description: Several workers have shown that certain colloidally dispered materials are removed from the blood stream by the liver and spleen. Jones, Wrobel, and Lyons have utilized suspensions of anhydrous chromic phosphate for the selective irradiation of the liver and spleen with p{sup 32} beta particles. Gersh demonstrated that colloidal calcium phosphate is taken up by the liver and spleen. He stressed the failure of bone marrow phagocytes to take up this colloid in rats and dogs (though he referred to possible uptake in the marrow of rabbits under special conditions), and commented on the relative 'refractoriness' in general of the bono marrow as compared with liver and spleen with respect to the uptake of colloidal dyes from the blood stream. Some histological data indicate that 'Thorotrast' (a colloidal thorium dioxide preparation) is deposited in the bone marrow as well as in the liver and spleen, but no quantitative data as to the relative distribution are available. In the preceding communication the methods for the preparation of colloids incorporating radioisotopes of yttrium, columbium, and zirconium were given. The present studies are concerned with the localization of such colloids primarily in the bone marrow or primarily in the spleen and liver, with an analysis of some of the factors which may be responsible for differences in localization.
Date: April 21, 1948
Creator: Dobson, E.L.; Gofman, J.W.; Jones, H.B.; Kelly, Lola S. & Walker, L.
Item Type: Report

The Metabolism of Curium in the RAT

Description: The heaviest of the known elements is curium, which was recently discovered by Seaborg and his associates. This new element can be produced by the alpha particle transmutation of plutonium by the following reaction: {sub 94}Pu{sup 239} + {sub 2}He{sup 4} {yields} {sub 96}Cm{sup 242} + {sub 0}N{sup 1} This isotope of curium is radioactive and decays by the emission of an alpha particle to form plutonium 238 which, in turn, is also radioactive. Curium 242 has a half-life of 150 days, and its radioactive daughter, plutonium 238, has a half-life of 50 years. This isotope of plutonium decays by the emission of an alpha particle to form uranium 234 which has a half-life of 233,000 years. Shortly after the organization of the Atomic Energy Project, it became apparent that formidable problems would be presented as the result of the release of nuclear energy. One of the most urgent of these was the hazard presented by the production of large quantities of the radio-elements created by the fission of uranium and the coincidental formation of neptunium and plutonium. In an attempt to evaluate the potential danger presented by these radio-elements from the chain reacting pile, a large series of metabolic studies with experimental animals were undertaken in a number of laboratories working upon the Atomic Energy program. These studies, which have been briefly summarized elsewhere, included a series of investigations on the metabolism in the rat of the more important members of the fission products in the carrier-free state, as well as most of the heaviest elements at the end of the periodic table. These studies made it possible to predict on a semi-quantitative basis the potential hazards that this large number of radioactive elements might present should they gain entry into the body.
Date: January 15, 1948
Creator: Hamilton, J.; Scott, K. & Axelrod, D.
Item Type: Report

Medical and Health Divisions Quarterly Report October 1947 To Jan. 1948

Description: This quarterly report discusses the following topics: (1) the metabolic properties of plutonium and allied materials; (2) biological studies of radiation effects; (3) biological effects of radiation from external and internal zones; and (4) health chemistry.
Date: February 4, 1948
Creator: Authors, Various
Item Type: Report