The bremsstrahlung emitted by an electron scattered in a Coulomb field was first calculated by Bethe and Heitler. The total cross section for production of photons with wave number between k and k + dk by a nonrelativistic electron of kinetic energy {epsilon} is d{sigma}/dk dk = 16/3 Z{sup 2}r{sub 0}{sup 2} (e{sup 2}/hc) (mc{sup 2}/{epsilon})log ({radical} {epsilon}/hck + {radical} {epsilon}/hck -1) dk/k, where Ze is the charge of the (heavy) ion, and r{sub 0} is the classical electron radius. Bremsstrahlung in a plasma has been computed by a number of authors in the approximation of replacing the Coulomb field by a cut-off Coulomb or static Debye potential. It is the purpose of this communication to call attention to another important effect of the medium upon the rate of emission of bremsstrahlung. This may be described as a modification of the relation of the photon's energy to its wave number, due to the index of refraction of the medium. Equivalently, we note that one must include in the calculation of bremsstrahlung in a medium the photon-medium interactions which result in the 'clothing' of a 'bare' photon. The replacement of a particle by a quasiparticle has long been known to be …

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The labeling of newly-formed lymph cells with tritiated thymidine, lymphatic duct cannulation, and the peripheral destruction of lymphocytes by extracorporeal irradiation of the blood were used to estimate the mass of prestored lymphocytes and the relative degree of recirculation of 1ymphocytes from blood to lymph and back again. Topics discussed include the effects of extiacorporeal irradiation on the histologic picture of the lymphoreticular tissue, the influence of extracorporeal irradiation upon the thoracic duct output, and preliminary observations on labeling of lymphocytes by tritiated thymidine at the completion of extracorporeal irradiation. Data indicate that the mass of preformed small lymphocytes may be as large as 40 times that present in peripheral blood, that the blood feeds lymphocytes primarily into the lymph, and presents strong evidence for lymphocyte recycling. (C.H.)

A solenoid wound with high-field superconducting wire displays maximum currents and fields (H) that are less than the critical field of the wire itself in an equal field (H). Montgomery's and Chandraseknar and Hulm's models for these maximum properties indicate, respectively, a unique coil quenching characteristic for geometrically similar solenoids and one unique characteristic for all solenoids with identical wire type and turn distance. Experiments with Pb coils did not verify Montgomery's model and contradicted Chandrasekhar and Hulm's model. The experimental results, however, did support an analysis of the surface currents in an ideal superconducting infinitely long solenoid. (D.C.W.)

The current-carrying capacity of Nb- Zr wire was studied under conditions of swept magnetic field and fixed wire current and of fixed magnetic field and swept wire current. The effects of wire movement, thermal environment, copper coating of the wire, and rate of sweep of wire current or magnetic field were determined for these test conditions. (auth)

The absorption of longitudinal ultrasonic waves was studied as a function of transverse magnetic field in pure single crystals of lead at 1.2 deg K. The results were found to be generally consistent with the Fermi surface of lead suggested by Gold. In particular a detailed study of the magneto-acoustic oscillations, as a function of sample orientation and field direction, allowed the determination of some of the dimensions of the hole surface in the second Brillouin zone and revealed a number of new electronic orbits on the multiply- connected surface in the third zone. The absolute magnitude of the attenuation and its dependence on propagation direction and on magnetic field were studied and the results interpreted in terms of the general theory of ultrasonic absorption. (auth)

Mathematical implications of the Pomeranchuk rule and the Pomeranchuk- Okun rule are discussed. (auth)

An equation is given for the relative hazard, H, of various radionuclides under uniform working conditions. H is defined as the ratio of the average muC/cc inhaled in the working area to the maximum permissible concentration, MPC, of the radionuclide for occupational exposure. The variation of H is discussed in relation to such parameters as radioactive and biological half lives of the radionuclides, fractional retention, dilution factors, specific activity, energy, RBE, relative damage factor, n, mass of the critical organ, and the maximum permissible does to the critical organ. Comparisons are made with values of H obtained by this and other investigations. The values of H obtained by this method appear to be consistent with estimates from operational experience. A table of values of specific activity, (MPC)/sub c/ and relative hazard, H, is given for the radionuclides listed in ICRP Publication No. 2, p.us values for a number of additional transuranic elements not previously listed by the ICRP.. (auth)

For 50 years particle accelerators employing accelerating cavities and deflecting magnets have been developed at a prodigious rate. New accelerator concepts and hardware ensembles have yielded great improvements in performance and GeV/$. The great idea for collective acceleration resulting from intense auxiliary charged-particle beams or laser light may or may not be just around the corner. In its absence, superconductivity (SC) applied both to rf cavities and to magnets opened up the potential for very large accelerators without excessive energy consumption and with other economies, even with the cw operation desirable for colliding beams. HEP has aggressively pioneered this new technology: the Fermilab single ring 1 TeV accelerator - 2 TeV collider is near the testing stage. Brookhaven National Laboratory's high luminosity pp 2 ring 800 GeV CBA collider is well into construction. Other types of superconducting projects are in the planning stage with much background R and D accomplished. The next generation of hadron colliders under discussion involves perhaps a 20 TeV ring (or rings) with 40 TeV CM energy. This is a very large machine: even if the highest practical field B approx. 10T is used, the radius is 10x that of the Fermilab accelerator. An extreme effort …

Several difficulties involved in accelerating heavy ions in a tandem Van de Graaff are discussed, and experiments with Br and I ions to determine the response of silicon detectors to fission fragments are described. The pulseheight spectra of the ions are given, and the stopping cross section for I ions in Au, Ni, Al, and C at 20--120 Mev are plotted. (C.E.S.)

Colloidal aggregates (10 to 20 m mu ) of human serum albumin /sup 131/I may be used safely by intravenous injection to perform photoscans of the heart, liver, spleen, stomach, and salivary glands in man. Large particle size suspensions (10 to 50 mu ) of the same material were investigated experimentally in animals for scanning the lungs after intravenous injection and the brain following injection into an internal carotid artery. The advantages of this test material are the relatively low radiation exposure to the target organs and the number of organs that may be examined. Radiation exposure is low because of the rapid turnover in the target organs and removal from the body, mainly by urinary excretion, within 72 hr. The mechanism of liverspleen localization with this organic colloid is the same as for inorganic colloidal /sup 198/Au, namely, rapid removal from the blood by the phagocytic cells of the liver and spleen. However, in contrast to the inorganic colloid, which remains in the phagocytic cells permanently, albumin is digested by proteolytic enzymes and the /sup 131/I label is set free to re-enter the general circulation. With the thyroid blocked, the / sup 131/ is excreted mainly in the urine …

The qualitative dependence of the neutron strength function upon optical model parameters is discussed with emphasis on the effects of variations in the magnitude and spatial dependence of the absorptive potential. A model is presented that gives a good account of strength functions and potential scattering radii, as well as neutron scattering cross sections below 1 Mev for spherical nuclei. (auth)

Methods for determination of calcium turnover in man with radioisotopes are presented and the clinical use of various techniques is evaluated. In the discussion of kinetic analyses, some important observations were made. The accretion rate calculation can be made independent of the number of compartments in the exchangeable calcium pool, and thus is not distorted by approximate estimations of this pool. However, if the exchangeable calcium pool is calculated with the isotope dilution technique, and the accretion rate obtained from this value by the total turnover equation, then an error is introduced into the value of the accretion rate. It was also pointed out that the multicompartment treatment is more appropriate than the customary single compartment analysis and utilizes all available information. Since the pool size has been of little clinical use so far, it was suggested that multicompantment analyses be used in the future. At present, no accepted model exists which can account for all data obtained in tracer studies and in particular for the last part of the serum disappearance curve. Preliminary results of long term studies of the retention in bones of strontium-85 was presented. These show that there is measurable turnover of tracer deposited in bone …

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A review was made of the effects of fluoride ions on the corrosion behavior of zirconium alloys in high-temperature water. Corrosion was found to occur as the result of contamination of the water or the zirconium surface. A major source of fluorides is undue delay in rinsing the HF--HNO/sub 3/ pickling solution during surface preparation. The oxide on corrosion-resistant material has been found to contain up to 7600 ppm fluoride from this source. The threshold concentration of fluoride in the oxide film which produces poor corrosion resistance ranges from 8500 to 17,000 ppm. Accelerated corrosion from fluorides in water at 300 to 360 deg C occurs at about 100 ppm, although increased corrosion has been reported at 10 ppm fluoride in water at 300 deg C. Fluorocarbon plastics degrade and contribute fluorides to the hightemperature water or to the alloy surface when in direct contact with zirconium. Chlorides (1 to 10,000 ppm) and iodides (1270 ppm) do not adversely affect the corrosion behavior of zirconium alloys in water at 360 deg C. The mechanism of corrosion is not well understood but apparently is related to the formation of insoluble zirconium oxyfluorides during pickling and during exposure to fluoride- contaminated water. …

From International Conference on Nuclear Physics with Reactor Neutrons, Argonne, Ill., Oct. 1963. Experiments were performed in which the kinetic energies of correlated fragment pairs from thermal- and resonance-neutron-induced fission were measured. In addition, a three-parameter ternary fission experiment was performed in which the energies of correlated fragments were measured in coincidence with the energy of a third emitted particle, usually a long-range alpha particle. The detectors were large-area silicon surface barrier detectors. The instrumentation associated with these experiments is discussed in detail. The complete system is described, with attention given to the problems of background reduction (fast-coincidence requirements), stability, linearity, and resolution. Particular attention is given to the reduction of spectrum distortion by pile-up pulses (alphaon-fission pile-up within the amplifier resolving time). Methods and limitations of pile-up detection are discussed. A new method for inspection and removal of pile-up pulses is described. (auth)

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From American Nuclear Society Meeting, New York, Nov. 1963. The use of the asymptotic solution to the one-velocity transport equation is considered. The angular distribution for fast neutron elastic scattering by heavy elements is discussed. An exponential angular distributi on is assumed to simplify the decay length calculation. The diffusion length of 1 to 15 Mev neutrons in iron is calculated, as well as the vector flux angular dependence. The asymptotic solution for an arbitrary angular distribution of a plane delta -function source is also found. An isotropic source is investigated, and some applications of the model are examined. (auth)

From American Nuclear Society Meeting, New York, Nov. 1963. The need for control of the flow distribution and/or steam quality in boiling reactors is discussed. A quality control device is being developed which consists of an entrance venturi and an exit venturi for measuring the flow rates into and out of the channel, means for comparing the two flow rate signals, and a value for regulating the flow rate. This device can be used either as a constantquality device or as a controlled-quality device. Results are given of air-water studies of two-phase flow in a vertical venturi. (D.L.C.)

l963. The Wisconsin tandem accelerator is used part of the time for experiments in neutron physics. In these experiments the properties of neutrons from charged-particle reactions as well as the interaction of neutrons with nuclei are studied. Some of the techniques used and some of the results obtained are described. (auth)

The effects of competition between resonances of different isotopes were investigated. Flux and reaction rate calculations on a Pu/sup 239/-- U/sup 238/ system revealed that U/sup 238/ exhibits both self-shielding and interference effects, the latter becoming noticeable at enrichnnents of a few per cent. Gold activation was also found to be depressed by the presence of U, but was insensitive at low enrichment values, Investigation of the Pu/sup 239/ resonance integral showed an asymmetric effect involving both interference between potential and resonant scattering and interferance with resonance absorption in another isotope. The interference scattering arising in each resonance level had a notable effect on the average change in the Doppler coefficient. (D.C.W.)

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