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The energy spectra of neutrons from the fission of U235, U233, and Pu239 have been studied with seven high-energy activation detectors covering the range 0.6 to 16 Mev. Interpretation is in terms of the Maxwellian spectral function E1/2 exp(-E/T). By means of a unique cavity arrangement within a moderator to obtain pure thermal-neutron-induced fission neutrons, the average energies of the three spectra are found to be in the ratios U235: U233: Pu239= (1): (1.016+or-0.003): (1.039+or-0.003). Differences between the normalized spectra are most pronounced at high energies as exemplified by the relative Pu239:U235 flux ratios 1.17+or-0.013 for 611 Mev.

Ever since the discovery of cosmic rays, investigations of time variations in their intensity have been carried out in the hope of obtaining information on their nature and origin. Early experiments were somewhat contradictory, but it was soon clear that any variation present could be no longer than a few percent at the most. This meant that experiments had to be carefully planned and carried out over a long period of time to attain the statistical accuracy necessary for clear-cut results. In addition, the influence of the atmosphere and the earth's magnetic field made it very difficult to interpret the experiments in terms of properties of the primary radiation.

If a one-dimensional shock wave travels through argon, the translational degrees of freedom of the atoms are immediately excited and reach translational equilibrium within two collision lengths. If the shock velocity is sufficiently high, energy will be transferred from the translational degrees of freedom to those of electronic excitation and ionization until complete thermal equilibrium exists. The region between the first disturbance in front of the shock and the point at which thermal equilibrium is first realized is the shock front.

The statistical model of the atom, first propounded by Fermi and Thomas has proved a most useful approximation to the self-consistent field method in calculating electron distributions and fields in atoms. Because of its relative simplicity, it has found wide application as a means of predicting properties of free atoms and of solids. The original theory has been the subject of many modifications and refinements, some of which are reviewed in this paper.

If the phenomenon of isomerism occurred in bromine nuclei, it would be of great help in elaborating the level schemes of these isotopes. The occurrence of isomerism in the odd isotopes of arsenic and rubidium, the nearest odd-Z neighbors to bromine, suggested similar behavior in bromine odd-Z isotopes. In this investigation, the pulsed-beam method was used to search for isomers. The procedure consisted of pulsing the beam of a Van de Graaff accelerator and counting any resulting activities during the time between beam pulses. After preliminary surveys during which natural bromine was bombarded with neutrons and natural selenium was bombarded with protons and deuterons, protons were used to bombard selenium targets enriched in selected isotopes. The spectra of the resulting activities were observed with a 100-channel analyzer and the half-lives of the activities of interest were measured with a 9-channel time-delay analyzer. The detectors of the gamma-ray activities consisted of thallium-activated sodium iodide crystals mounted on photomultipliers. From these measurements it was possible to conclude that there indeed were isomers in Br77, Br79 and Br81 as well as Br78. Some of the activities found had been previously reported but were not assigned to any particular bromine isotope.

We wish now to address ourselves to that problem which can be described in physical terms as the reflection and transmission of "waves" by and through some sort of "transition region" between two homogeneous media. At this stage we will work strictly within one dimension; later on this severe restriction will be somewhat eased. For simplicity of notation we will for the present give the transition region a finite thickness h; later on we will often allow h to become infinite when the disturbance due to the transition region dies away fast enough with distance.

In recent years, much work has been done in the investigation of high-energy nuclear collisions in various materials. The purpose of these investigations is to gain a better understanding of nucleon-meson-nucleon interactions at high energies. Laboratory accelerating devices are capable at the present time of attaining energies which are still very low in comparison to the upper limit of the cosmic radiation energy spectrum. As a result, these investigations are best carried out by using the very hard component of the cosmic radition as the primary particle of the collision.

Radiative capture (n,y) cross sections, in addition to their theoretical interest, are of great practical importance to the technology of reactor design. A knowledge of the absolute excitation functions of the various materials employed in reactors permits calculation of the effect of these materials on the reactivity of a reactor, and also enables shielding calculations to be made.

The purpose of this thesis is to determine how the muon component of an extensive air shower varies with the energy of the incident primary particle and different values of inelasticity and multiplicity for the nuclear interactions according to a simple theory of extensive air showers suggested by Professor Roy Thomas of the University of New Mexico. The method of attacking this problem will be to calculate the number of muons resulting from decay of pions produced in each nuclear interaction of the primary particle and from this the total number of muons passing through certain levels of the earth’s atmosphere for different values of the variable indicated above.

The density of the air is in general determined from a knowledge of the pressure and temperature by applying the ideal gas law. This law may be stated in the following for; p=MP/TR, where p is the density of the air in gm/cm3, M is the gram molecular weight, P is the pressure in dynes/cm2, T is the temperature in degrees kelvin and R is the universal gas constant in ergs per degree absolute for one mole. This method is also used in the determination of the air density as a function of the height in the atmosphere. Certainly it is the most convenient method, for the parameters of pressure and temperature may be measured by a number of simple techniques.

It should be mentioned that this paper deals mostly with the work done by others and only a certain portion is original. The student wishes to state that he is presenting a thesis that would be considered theoretical and not empirical. The history of the work done in the field of osmotic pressure is treated at length and much of the theory used by the experimenters is derived. Many periodicals carry the papers written by the scientists of osmotic pressure and some of these men have spent perhaps fifteen of twenty years on their experiments.

The object of this inquiry is to examine the relation between plane wave sound velocities in cubic crystals and the elastic constants of such crystals. Leading directly into this an extensive treatment of the classical theory of elasticity as it pertains to the cubic system. An application of the results will be made by detailing a means for obtaining the elastic constants of plastic single-crystals from measurements of velocity made on poly crystalline specimens.

It was proposed that an attempt be made to measure the directional energy of high-energy primary gamma radiations in space. The difficulties of such an effort are readily obvious. To escape the environmental air envelope of the earth and to lessen the interference of secondary radiations, an instrument package would have to placed into a known orbital trajectory.

In an attempt to understand certain of the high energy processes that occur in the solar and terrestrial atmospheres and the interplanetary medium a detector of 20 to 160 MeV neutrons had been designed and constructed for inclusion in the NASA Orbiting Solar Observatory, Satellite OSO-G, which was launched into a near circular orbit at approximately 500 km altitude in August 1969. Both the angle of incidence and the energy of the neutron are determined by a telescopic arrangement of four scintillation plastic counters (Pilot B; hydrogen to carbon ratio 1:1) which generates proton recoils and provides pulse heights for analyzing them. The set of four counters is embedded in an envelope of scintillation plastic (Semi-Elements) to discriminate against charged particles and other background.

The search for an anisotrophy in the penetrating component of the cosmic-ray flux is usually carried out with narrow-angle directionally sensitive detectors located near the surface of the earth. Directional sensitivity is achieved by using a cosmic-ray telescope, consisting of Geiger counters or of scintillation counters, in a coincidence arrangement. Thus a solid angle of acceptance for the cosmic-ray particles is defined.

Our concern here will be to investigate the form of certain solutions of equation (7); we will be content with a two-dimensional analysis.

A liquid hydrogen bubble chamber for use as a neutron spectrometer has been constructed and operated. The chamber employs 90o stereography and is expanded by a piston located in the liquid. The construction and operation of the chamber are described. A special measuring microscope for analyzing the data is described along with the associated electronics for digitizing the screws of this device. Reading rates of 60 proton recoils per hour have been obtained and the reading procedure is discussed. Preliminary results from a neutron-proton differential cross section measurement indicates a resolution of 5% may be obtained with 22 Mev neutrons, with a background of < 5% of the peak height

Many phases of present-day experimental physics require remote indicating devices where data must be transmitted either by wire or radio to a distant point. For example, when atmospheric parameters are measured by means of sounding balloons, it would be desirable to use a lightweight device which would accurately convert measured information into electrical data in a form which would allow easy transmission to a receiving station.

The two theories that have been presented for the zodiacal light show that it is due to light scattered (and perhaps emitted) from an extensive lenticular cloud of particles lying in the plane of the ecliptic. The basic difference of the two theories is the position of the center of this cloud. One, the planetary theory, places the sun at the center of this cloud. The other, the atmospheric theory, places the earth at the center of the cloud.

This phenomenon of the spray produced by bursting bubbles at liquid surfaces is certainly familiar to drinkers of carbonated soda pop, champagne and other effervescent liquids. This same phenomenon has been observed at ocean surfaces. Small bubbles, some of which originate at great depths, rise to the surface and break; tiny droplet is thrown upward from most of the imploding bubbles. Some of these droplets may be caught and carried into the atmosphere by winds sweeping along the surface. The droplets evaporate but leave small particles of salt suspended in the air; the particles then serve as condensation nuclei and are of great importance in the formation of rain and fog. The purpose of this paper is to examine this phenomenon, considering in particular the energies of the droplets as a function of the solution and surface tension.

In certain types of experiments involving balloon-borne equipment it is desirable to know how the orientation of the apparatus varies with time. The author has investigated a method of telemetering azimuthal orientation from a balloon to the ground, and has constructed a protoype of a telemetering magnetic compass. The basis of the compass is a rotating-ring magnetometer of the type first described by Nielsen (1) and used by others (2,3,4) for various purposes. The output of this device consists of two a.c. signals, whose relative phase is determined by the orientation of the magnetometer with respect to the external magnetic field. In the compass constructed the signals are converted into pulses, which are transmitted by radio.

This thesis attempt to provide a solution to a basic problem inherent in the operation of Geiger-Mueller counting tubes, that is, reduction of the insensitive time, or “dead time”, following the discharge. Many researchers, using various quenching gases for internal quenching and various vacuum tube circuits for external quenching, have succeeded in reducing the “dead time” significantly. Reduction of the insensitive time provides more efficient and accurate counting. The solutions presented in this thesis utilize transistor circuits instead of vacuum tube circuits for external quenching. In an extensive research of current literature, no attempts to transistorize a quenching circuit could be found.

A large amount of experimental research in the field of atmospheric physics involves carrying apparatus aloft by means of balloons. Data from balloon-borne instruments may be obtained either by recovery of the apparatus or by radio telemetering during the flight. Of these two methods, the latter is of course the more convenient and reliable, since recovery of the apparatus is time-consuming and often impossible.

This investigation is an attempt to correlate variations in cosmic ray intensity with shifts of the isobaric layers in the stratosphere on the basis of the change in path length traveled by radioactive mesotrans, and in consideration of ordinary mass absorption of the air along the path.

A "camera" containing thirty-six nuclear plates was carried into the upper atmosphere to an altitude of twelve miles by a free balloon flight. These plates were arranged in four groups separated by successively thicker layers of steel so that nuclear events under different amounts of matter could be observed. After recovery of the equipment these plates were developed and examined under the microscope. Four plates were selected for intensive investigation, and data was collected on the tracks found in the areas examined. In the first part of this report nuclear plate technique will be discussed in general together with the properties of the particular Ilford C-2 emulsions used in this experiment. In the second part detailed information will be given on the arrangement of the plates in the "camera," the time exposed, and the searching procedure used. In the third part the data collected in the examination of a total area of 4.8 squared centimeters will be tabulated and analyzed.

Because of the incomplete understanding of the processes which cosmic rays undergo in the atmosphere, there is still no generally accepted treatment of the atmospheric dependent variations of the intensity or preferred method of establishing correct coefficients.

This study shows that current noise occurs when there is a deviation of Ohm's Law, i.e., when the applied voltage and resultant current are no longer proportional. Since most, and perhaps all, cases of occurrence of frequency and current dependent noise are associated with non-linear devices, e.g., semiconductors, diodes, vacuum tubes, insulators near breakdown, it seems reasonable to seek a mechanism involving non-linearity as an important feature. Even though it may not be justifiable to seek a single mechanism to explain all of the occurrences of current noise, nevertheless, the fact that in cases studied and discussed herein the non-linearity is not a layer phenomenon (as in semiconductor devices), nor a space-charge effect (as in vacuum tube devices), but simply a result of heating the sample does seem to point to some single underlying cause.

With the advent of the launching of space exploration in the last decade there has been parallel scientific effort to determine the nature of cosmic radiation found in space. This theoretical study has the objective of determining the energy spectrum of gamma rays produced in interstellar matter by the primary cosmic rays.

Theoretical calculations describing the performance of a Čerenkov counter designed as a total absorption gamma ray spectrometer for the energy range 100-1000 Msv are presented, using approximation "A" from the standard shower theory, and R. Wilson's quasi-analytical method of cascade shower analysis.

To date there have been no adequate measurements of the energy spectrum of high energy cosmic gamma-rays. This information can only be obtained from instrumentation located above the atmosphere. An experiment has been designed by Dr. Leavitt at the University of New Mexico to obtain this information. It is to be orbited in the S-17 Orbiting Solar Observatory.

The main interest in this paper is to study the effect of the florescent wavelength shifter "POPOP" with respect to Cerenkov radiation and to determine how the efficiency of a Cerenkov counter is affected.

It was the purpose of this experiment to examine the difference in the density determinations and, since the Geiger tube threshold is much lower, to calibrate the liquid scintillator so that it is capable to determining the absolute particle density with greater accuracy.

Certain molecules, called “globular” molecules, when first solidified form what are called “plastic” crystals. They are called “globular” either because they may exhibit an approximate spherical symmetry about their center of structure or because they may be small enough or of such a shape as to appear spherically symmetric because of rotation. The first case might be exemplified by methane (CH4) which has the configuration of a regular tetrahedron. The second case might be exemplified by hydrogen chloride (HCL).

The Vertical distribution of atmospheric ozone has been determined spectroscopically either from surface observations or from balloon-borne spectrographs sent aloft. These spectrographic techniques have several disadvantages. Surface observations of the "Umkehr Effect" give only a rough distribution, four or five points for the entire atmosphere.

In connection which a program of research in the physics of the atmosphere, a need has arisen for a sensitive differential photometer which would be adaptable to balloon-borne operation. This paper describes a prototype of such an instrument. The present photometer is constructed for preliminary investigations to be carried out in the laboratory, but with light weight components used in the design except for the power supply and the main structural frame. Consideration is given to these latter features to the extent that the entire equipment is designed for operation from power sources which can be directly replaced by small light-weight battery packs. The optical components are all replaceable by equivalent ones of smaller size, and the metal parts of the frame can by replaced almost entirely by fibre or plastic materials.

The purpose of this thesis is to present a procedure for calculating the fraction of high energy electrons incident on a Cerenkov counter which are scattered out of the region of detection. With the assistance of Professor Christopher P. Leavitt of the University of New Mexico, a method of solving the above problem has been established. The method uses the theory of multiple scattering as described by Rossi and Greisen and a numerical integration technique to evaluate the effective or average scattering distribution function for the Cerenkov counter. A relationship is developed which can be programmed on a Bendix G-15 Computer (or similar calculator) to determine the probability of scattering loss for an election at some given energy.

Three major topics are discussed in this thesis. The first of these has immediate application to analysis of air shower data which is presently being gathered by two large scintillation tanks located immediately behind the University of New Mexico physics building. The data with which the other two topics are concerned cannot be gathered with present equipment, but these preliminary calculations have been performed in anticipation of the installation of the appropriate apparatus.

For experiments involving small scintillators and for experiments involving scintillator telescopes, the circuitry may closely resemble that used with geiger counters. However, if it is desired to make use of the variation in the signal amplitude in a large scintillator, some means must be found to deal with a wide range of amplitudes. The scintillator employed in the experiment to which this work relates is a tank 10 feet in diameter that contains 300 gallons of activated toluene; light of the scintillations is collected by a 16 inch photo-multiplier tube that is located on top of the tank.

Magnetic field variations in both magnitude and direction are known to occur due to such phenomena as atmospheric tides and solar activity. Magnetic storms caused by solar activity may bring about variations in excess of one percent of the magnitude of the earth's normal magnetic field; but in general the changes are slight and require sensitive instruments for their measurement.

In nuclear magnetic resonance absorption work, the detection of the absorption of energy by protons situated in a steady strong magnetic field and subject to a weak radiofrequency (RF) magnetic field is attempted. The protons are present in a sample placed inside an RF coil. A radiofrequency current, present in this coil, produces a rapidly oscillating magnetic field which is capable of supplying energy to the system of protons in the steady strong magnetic field. This absorption of energy by the protons alters their relative numerical distribution among the energy levels available to them.

In this paper the spectrum of the neutrons escaping from a critical sphere of U233 is investigated experimentally and theoretically. The experimental investigation involved exposing a nuclear emulsion to the neutron flux and, after development, examining the details of the proton-recoil tracks visible in the emulsion.

In connection with other research work in the physics department at the University of New Mexico it became of interest to make a detailed study of a resistance-capacitance couples low-pass filter which incorporate inverse feed-back. In order to determine the effect of the inverse feed-back on the filters, calculations are made on circuits with and without feed-back. Response curves are calculated for step-wave inputs and for sine-wave inputs, and these calculated curves then compared with experimental response curves.

In the investigation of cosmic rays at balloon altitudes, it is important to recognize the various factors that affect the total intensity at any point in the atmosphere. The three main factors are: (1) Atmospheric influence: variation of intensity with atmospheric depth, (2) Geomagnetic influences: variations of intensity with the geomagnetic latitude, and (3) Extraterrestrial influences: periodic and non periodic variations of intensity.

The purpose of this study is to investigate the possibility that this diurnal variation in cosmic-ray flux may be due to a general dipole-like magnetic field centered upon the sun.

The object of the zodiacal light work at Capillo Peak is to take comparable records of zodiacal light intensities over an extended period of time. In order to obtain extra-terrestrial isophotes from the original recordings, corrections for loss of light intensity in the atmosphere must be made.

Under conditions of standard temperature and pressure, it has been found that no reaction occurs between silver and oxygen, nor between silver and ozone. When the temperature of the silver is raised, however, it is oxidized by ozone but not by oxygen. Upon raising the products of the reaction to a still higher temperature, they decompose into silver and ordinary oxygen. By measuring the amount of oxygen thus produced, it would be possible to calculate the amount of ozone involved originally.