Engineering notes on limiting bore diameter, angular divergence in a linear accelerator.

Progress on projects on experimental physics, theoretical physics, MTA Target-Physics Program, accelerator construction and operation, chemistry, biology and medicine, plant and equipment.

The principal types of particle accelerators are described briefly according to operation and history. Known operating particle accelerators are listed with their pertinent dimensions.

The development of high-energy charged particle accelerators such as the Bevatron and of improved nuclear-event detection devices such as the Berkeley 72-in. hydrogen bubble chamber has greatly increased the need for high-speed data reduction of nuclear events. Full exploitation of the potential of the 72-in. bubble chamber demands a very high-speed analysis system. This paper describes an approach to such a system.

A method is presented for measuring the average energy of the neutrons from a source. The attenuation of the neutrons by polyethylene is measured by the use of a long counter in good geometry. The attenuation length is a sensitive function of the neutron energy. The average neutron energies from several (o, n) sources have been measured and agree well with values obtained by other techniques.

To properly assess the "sensitivity" of explosives systems under impact conditions we must obtain detailed information on these mechanisms by which explosives are ignited by impact. It is necessary to know which impact conditions represent the greatest hazard to explosive materials, as well as to know for a given impact condition the relative responses of explosives of interest. I should like to describe to you a program sponsored jointly by the Department of Defense and the Atomic Energy Commission to attain this type of information. A wide variety of impact experiments have been conducted using geometrical arrangements of explosive, plastic, and metal which are relatively simple compared to complete ordnance systems. All of these tests have employed billets of explosive fabricated by standard production techniques, and the billets have been sufficiently large that ignition, once started, has something of the same opportunity to grow or decay as in full scale ordnance assemblies. From these relatively simple tests there has accrued much new useful information on the behavior of explosives under impact. With this new information providing a base from which to work, it is hoped that theoretical calculations on impact phenomena will in the future make a bigger contribution to …

In the course of modern physics research, the need frequently arises for storage of large quantities of electrical energy which can be periodically discharged at high peak power into a load. Until recently, the homopolar machine has been an intriguing device having considerable academic interest but little practical value. In recent years, successful machines have been developed to utilize liquid-metal brush systems. The liquid-metal brush overcomes all the problems associated with current collection power loss, frictional loss, and limiting peripheral velocity. Consequently, these machines are now worth serious consideration where high-current dc generation is required. The main purpose in setting up a homopolar generator test program was to establish the limits to which an essentially standard commercially available generator of this type could be pushed.

This bibliography lists selected articles on molybdenum, niobium, tantalum, tungsten and uranium oxide in the journal literature of the U.S.S.R. The following sources were used and also are noted after each citation, Special Library Association Translation monthly 1959-June 1960, U.S. Library of Congress Monthly index of Russian accessions 1955-June 1960, U.S. Office of Technical Services Technical translations 1955-1958.

At the Montreal colloquium Ahmed urged Oliver to make batches of emulsion which would differ only in gelatin concentration. At that meeting Oliver had reported finding a correlation between grain size and silver ion concentration during precipitation, as implied by Perfilov and his Leningrad colleagues. Ahmad felt that one should have more precise knowledge of the relative influence of gelatin concentration of grain sized and their distribution. The incentive is that, in spite of excellent progress in many laboratories and in consistently dependable production from industry (to us, of course, Ilford is most familiar), nuclear emulsions are needed in a wider variety of sensitivities and grain sizes. Available nuclear emulsions have limitations in sensitivity, discriminatory ability, and concentration of hydrogen nuclei. Fine grain size enhances discriminatory ability. An incentive is also in that there is a shortage of literature dealing with the processes involved in the fundamental steps of emulsion production.

Introduction. The von Neumann stability criterion is used to analyze the stability of three types of difference schemes for partial differential equations. It is shown that, contrary to the usual rule of thumb, there exist symmetric implicit schemes for a class of equations which are unstable for every mesh-ratio but that this cannot occur if (a) there are fewer than three "space" variables or (b) the difference expression is used to approximate the mixed derivative.

This is a selected bibliography of books, journal articles, and unclassified reports published on the state of matter at high pressure from 1950 to October 1959. Sources consulted were: Physics Abstracts, Nuclear Science Abstracts, Geophysical Abstracts, Library of Congress Monthly Index of Russian Accessions, and Chemical Abstracts.

Introduction. With the imminence of non-destructive landings of small instrumented payloads on the moon, many suggestions are being put forth as to methods of analyzing its surface. It is the purpose of this report to present a body of information which, it is hoped, will be useful in examining the feasibility of an early nuclear experiment to determine the elemental constituents of the lunar surface. The reasons for considering a nuclear approach is that it may be possible to perform an analysis without complex and elaborate manipulations, sample preparation or rigid geometrical constraints. Only those experimental designs which come within the presently-available or very-near-future general boundary conditions on weights, power, vehicles, etc., are discussed. The general approach is to consider the bombardment of the lunar surface with various nuclear beams and to examine the possible nuclear reactions which are know to be dependent on the mass and charge of the irradiated material. Then, those resultant radiations are sought which can be detected with little-or-no loss or distortion of the information which they contain.

The basic scheme under consideration in this research on stability of closed-loop of the Mark I machine is one in which a voltage proportional to the magnitude of the rf fields in the cavity acts to control rectifier voltage output. It is recognized that such is not the only scheme for maximization of output which may be conceived, but only what seems to be a logical and direct way of attaining such an objective.

Abstract: The rate of extraction of PuIV in either direction between benzene-TTA and aqueous HNO3 solutions is shown in the present study to be fast enough so that application of the chelate process to continuous operation should be feasible. This conclusion is based on two primary considerations: 1. The mechanism limiting the rate of extraction appears to be diffusion and not chemical-reaction-limiting. 2. The extraction may be controlled by adjustment of the system conditions to give almost any desired specifications of rate and/or equilibrium. A continuous process involving multiple extraction stages with a controlled pH gradient is proposed for obtaining maximum decontamination and plutonium recovery.

The complexing of lanthanum by various anions and weak acids was investigated by observing the light absorption of the complex formed with thenoyltrifluoracetone (TTA). This species showed the properties needed for a satisfactory specgtrophotometric method of analysis.

Abstract: "Probes were used to measure certain properties of the cloud of positive ions and electrons ejected from a pulsed ion source having two hydrogen-loaded electrodes. Time-of-flight measurements show: the presence of H+ ions with 50 ev directed energy; an increase of this energy with increasing pulse current in the source; a higher peak yield of ions with higher peak currents in the source; and higher yields and higher ion energies up to 110 ev have been recorded with the use of a pulsed magnetic field impressed upon the source. The neutral positive ion-electron beam from the source has been projected against an increasing magnetic field and the reflected and transmitted signals have been recorded and compared as a function of the magnetic field. Probe signals from the plasma as it encounters the magnetic field are oscillatory, suggesting that magnetohydrodynamic phenomena are presented."

Abstract: "The reflections of microwaves from the walls of a plasma-containing vessel are studied. The probable cause of the reflections is discussed, and several suggestions are made for eliminating the reflections from the waveguide in the vessel and particularly from the pyrex vessel wall and copper tubing surrounding the pyrex. Quarter-wave-thick carbon-filled plastics or glasses having a very low vapor pressure room most promising when placed inside the pyrex cylinder. BaTiO3 appears to be an excellent material when placed outside the vacuum."

Report discussing interactions of 420-Mev/c K- mesons incident on a nuclear emulsion stack. Information on the differential scattering, elastic scattering, absorption events, and inelastic scattering of the mesons is provided. Additionally, the ratio of Λ to Σ hyperons produced in the primary interaction is calculated.

"An experimental study has been made regarding the passage of a beam of 100-kV ions (H⁺ and H₂⁺) across a magnetic field by means of a crossed electric field." This experiment was designed to answer the following questions: "(1) Is there a limit to the current that will traverse a magnetic field by the action of a crossed electric field? If so, what is the limit? (2) Do difficulties arise in maintaining the electric field? (3) For the source employed, what is the angular divergence and current density of the beam?"

Abstract: "Experimental evidence is given which indicates that electronic bombardment is responsible for damage and failure of insulating material subjected to intense corona attack. The experimental revolts are further supported by some theoretical considerations of the energy-time properties of corona discharges."

Abstract: "By a simple illustration it is pointed out that, conceivably, the real coupled character of the general magnetohydrodynamic equations may lead to much slower instability growth rates, if not stabilization, than predicted from the linearized set of equations."

A report discussing a more general analysis of "the relation between plasma pressure in the Astron [Thermonuclear Reactor] and the magnetic field of the E-layer" which is described in UCRL-5032. The analysis given in this report has "no restriction to the exponential form and [satisfies] the condition that the pressure at the axis shall be zero."

"This bibliography lists selected books, articles, and unclassified reports which have appeared in the following abstracts and indexes between August 1959 and December 1960."

"This bibliography is a compilation of titles to unclassified reports, journal articles and conference papers written by members of the University of California Radiation Laboratory, Livermore and Berkeley, relating to Project Sherwood (Controlled Thermonuclear Reactions) from 1953 through 1957."