The guiding center motion and the adiabatic invariants of charged particle trajectories in electromagnetic fields are treated in this review. General and specific theories of charged particle motion are also reviewed.

A repeatable technique for preparation of thin, self-supporting copper films has been developed at the Lawrence Radiation Laboratory in Livermore, California. The process, done in a vacuum chamber, involves evaporation of copper by electron bombardment, and deposition of the copper on a detergent-coast glass substrate. The copper film is later removed from the substrate by immersion in water.

An easy experiment for undergraduate students to measure the mass and diameter of a copper atom can be performed with inexpensive apparatus normally available any college physics laboratory. By measuring the density and by copperplating, one can obtain results which are accurate to better than 5%.

This paper reports the chemical and physical properties of the NTA film packet. It correlates with these properties the response of this packet to neutrons of various energies. In this correlation the concept of the track unit is introduced as a basic unit for reporting film-packet response.

Figures 1 and 2 summarize total decay energies for the four radioactive series. The alpha-decay energy obtained by measuring the energy of the alpha particle leading to the ground state includes the energy of the recoil nucleus. The curve shown in figure 3 defines in broad outline the conditions and regions of alpha instability. A great deal more is to be learned from a more detailed examination of the region where alpha radioactivity is prominent. Of great value to the experimentalist is that he is able to predict alpha energies, and the agreement between predicted and measured values often serves as a criterion for isotopic assignment. A number of systems for correlating alpha decay energies have been employed, and that perhaps most widely used is illustrated in figure 4. Here the isotopes of each element on a mass number vs. energy plot are joined, resulting in a family of curves which over a wide region comprise a series of nearly parallel lines.

Previous attempts to interpret chemical structure in terms of x-electron resonance have been recently criticized. A reinterpretation of the lengths of the C-C bonds in terms of orbital radii has not revealed any effects of x-electron resonance in the ground states of classical molecules such as 1, 3-butadiene, methyl acetylene, etc. Even in a non-classical molecule such as benzene, resonance shortening of the CC bond is only in terms of the strengths of the hybrid orbitals. If the lengths and force constants of the C-C bonds vary with hybridization, so also must their bond energies. If resonance is not important in classical molecules, the heat of atomization of a classical molecule must be given by the sum of either the energies of the bonds or the contributions of the atoms present in it. To test this theory, we have estimated the contributions of some standard carbon atoms, viz., primary, secondary, tertiary, quaternary, trigonal, and diagonal carbon atoms.

An electron can suffer a very large acceleration in passing through the Coulomb field of a nucleus, and in this interaction the radiant energy (photons) lost by the electrons is called bremsstrahlung (also, bremsstrahlung sometimes designates the interaction itself). If an electron whose total energy [formula] traverses matter of atomic number Z, the electron loses energy chiefly by bremsstrahlung. This case is considered here.

The problem of the natural convection of an electrically and thermally conducting fluid within a long, narrow, vertical toroidal channel centered in a large block of an electrically and thermally conducting solid is analyzed. A uniform horizontal magnetic field is applied to the fluid, and the bottom of the solid block is maintained at a higher fixed temperature than the top. The laminar steady-state single-cell convective motion of the fluid is considered and an approximate solution is found for the heat transfer rate between the bottom and top surfaces of the block in the limiting cases of small and large Hartmann number. A numerical example is given for liquid sodium in which the application of a magnetic field of a few hundred gauss is shown to significantly reduce the rate of heat transfer.

The sodium-ammonia solution system permits investigation of an array of compositions spanning the transition from non-metallic to metallic bonding. Reflection spectra in the range 1-20 [ ] were measured for solutions of mole ratio 5.5 to 168 [ ] per Na. The dilute solutions show peaks characteristic of the vibrations of ammonia and a strong peak near 1.5 [ ] which is assigned to the solvated [ ] species. Concentrated solutions show high reflectivity over broad wavelength ranges. The results for nearly saturated solutions are fitted reasonably by the free electron model, but in the range of mole ratio 10-15 a complex array of energy absorption processes of finite frequencies are required to fit the spectra.

The radius of a c-p hybrid orbital has been found to be given by the expression: [formula] where A is the radius of the pure p orbital, B, a universal constant equal to 0.336 A, and [ ], the coefficient of mixing in the hybrid s + [ ]. When radii appropriate for the orbitals that are paired together are used, bond length is additive of the orbital radii and no Schomaker-Stevenson correction is necessary. This shows that most bonds can be treated as covalent, single and localized.

The method of dispersion relations has in recent years found a wide application for the study of elementary particle reactions. Most of the work, however, deals with reactions of the type [formula], while the theory of those with more than two particles in the final state is still in a very preliminary stage. One reason for this is that even with only three particles in the final state the theory is already much more complicated. Nevertheless, a further development of the theory seemed to us very desirable. The theory at present is being developed on various levels simultaneously. Generally speaking, the aim of this paper is to put the theory in a form as closely as possible analogous to Mandelstam's formulation of the theory of reactions of type [formula]. In the later sections we specialize on reactions [formula], but as much as possible the formulation is in more general terms.

Tables of the electron pressure and kinetic energy for a partially degenerate, relativistic, ideal electron gas are computed by numerical integration using an IBM 7090 electronic calculator. These are given in terms of log10(B) and log10(0), where B is the ratio of the temperature to the rest mass of the electron and (O) is proportional to the numerical density of electrons. The tables include values of T from 5 million to 400 billion degrees and cover the range of electron densities from the region of a perfect gas to the region of complete degeneracy.

Specimens suitable for transmission electron microscopy have been prepared from bulk polycrystalline molybdenum after tensile deformation and recovery. The resulting dislocation substructures are described. Some tentative conclusions concerning the mechanism of plastic deformation in molybdenum are discussed.

Volatile hydrides may be prepared from ether solutions by the reaction of the appropriate chlorides with lithium hydroaluminate. In this general method, it is necessary to work with strictly anhydrous reagents and solvents because of the great reactivity of lithium hydroaluminate toward water. The procedures described here are believed to be much more convenient because the reducing agent employed is potassium hydroborate, which is relatively insensitive toward water. Since only aqueous solutions are involved, there are no solvent-purification steps and there is no dissolution or contamination of stopcock grease, etc.

Both in magnetohydrodynamic shocks and in accelerated partially ionized gas flow across a magnetic field, space charge separation occurs that establishes very large electric fields in the direction of motion. The width of the current layers associated with the acceleration is never less than the electron Larmor radius with no collisions and is broadened by electron collisions to a width solely determined by the effective resistivity. The electrons gain an energy regardless of collisions equal to the electric potential difference across the layer. This potential corresponds to the change in kinetic energy of mass motion per ion. For slightly ionized gases, the additional stress of neutral ion collisions within the layer can make the electric potential and hence gain in electron energy very large for only modest changes in mass velocity. Hence ionization may occur when the change in kinetic energy of the ions is small compared to the ionization potential.

Pulse-amplitude discriminators are useful in nuclear counting to separate signals of greater amplitude from a background of unwanted or noise signals of lesser amplitude. As used here, the term "fast" implies circuits capable of responding to pulses between a nanosecond and a microsecond in duration. An ideal discriminator would produce for any incoming signal whose amplitude is greater than a threshold bias level, an output pulse of constant amplitude, duration, and delay with respect to the input signal, regardless of the incoming duration and rate; and for signals less than the threshold, zero output.

Thin foils suitable for transmission electron microscopy have been prepared from bulk specimens of Cu-12.0% Al alloy quenched from 800' C to produce martensite. The martensitic structure consists of long lenticular plates which are twinned on 20-50A scale. The twin planes in the martensite are shown to be [formula]. There is evidence that this structure is ordered as expected for a transformation from an ordered parent lattice. Experiments using a high temperature stage show that the decomposition of the martensite on tempering can be followed directly, but the martensitic transformation did not recur on cooling.

"This study is primarily concerned with obtaining an order-of-magnitude estimate of the electromagnetic fields to be expected from a high-altitude nuclear bomb explosion; and it is not intended to be a complete analysis."

The structure and operation of cyclotrons are discussed. Factors limiting cyclotron size and energy are given. Improvements to the basic continuous-wave cyclotron are described, including frequency modulation, strong focusing, and variable-energy facilities.

Recent experience in instrumentation of several nuclear-physics experiments has demonstrated the feasibility of automating the data-acquisition phases of the experiment. Electronic circuits are employed wherever the rate of data flow would be slowed by the use of human operations. Information is selected, temporarily stored, and then recorded in a form suitable for immediate entry into a computer. Experimenters thus freed from the tedious aspects of data collection can devote their time to studying the results of the experiments. Potentially useful nuclear events are first selected by the fast-logic part of the instrumentation. Circuits performing simple logical functions are packaged in modular form for easy grouping into particular coincidence, gating, and mixing configurations. Circuits with slower response times are used for temporary storage and recording operations. Automatic test routines are used to initially align the equipment as well as provide continuous calibration during the experiments. Some of the high-speed circuits are described as well as the methods used to incorporate them into a large counting system.

Based on the assumption that the noise contribution of a semiconductor detector is due solely to the bulk properties of the semiconductor, equations are presented which indicate the theoretical limits of noise in detector-amplifier combinations. These equations show that an optimum amplifier time constant and detector bias voltage exist for which condition the minimum noise is independent of the semiconductor resistivity. The optimum performance of a detector-amplifier system is shown to depend only upon detector area, input capacity (less detector capacity), semiconductor minority carrier lifetime, and the transconductance of the amplifier input tube. A new detector structure including a guard-ring electrode as an integral part of the detector structure is described which largely eliminates noise due to surface leakage. Experimental results for detector leakage and energy resolution are presented which agree well with theory.

A system for measuring depths of cryogenic liquids is described. The indicating device is a modified differential pressure gage. The level sensing probes are of various types, either permanent or removable. The heat leak to cryogenic liquids may be made negligibly small.

Recently a T=1 resonance in the [Alpha w] system called [Y*1] has been observed with a mass of 1385 Mev. Two types of resonances have been predicted that might relate this observation to other elementary-particle interactions: (1) P 3/2 resonances in the Alpha w and Sigma w systems predicted by global symmetry corresponding to the (3/2, 3/2) resonance of the wN system, (2) a spin-1/2 Y-w resonance resulting from a bound state in the KN system. The position and width of the observed [Y*1] resonance agree with both theories but since the spin and parity have not yet been determined, it is impossible at present to distinguish between the two theoretical interpretations.

In previous letters we have reported a Av resonance, called Y*1, observed through the study of the interaction of 1.15-Bev/c K* mesons in hydrogen in the Lawrence Radiation Laboratory 15-in. bubble chamber. We now wish to report the results of the study of the three reactions [formula](1), [formula](2) and [formula](3).