It is shown that under very simple and general assumptions the existence of an antiunitary reflection transformation and the charge gauge group implies the existence of an antiparticle corresponding to a given charged particle. Similar consequences follow on replacing the charge gauge group by the baryon gauge group. No assumptions as to specific wave equations, or indeed the existence of local fields, are made.

It is shown that the annihilation rates of positrons in metals can be correlated to a good degree by a simple model of the annihilation process based on an assumption that the fractional number of electrons available for annihilation varies as the inverse of the atomic volume of the metal.

Even in its present primitive stage the molecular beam method promises to open up many opportunities for detailed studies of reactive collisions. The early results described here have revealed several features inaccessible to the traditional methods of kinetics. We hope this program of beam studies will ultimately provide the basis for constructing a theory of the molecular mechanics of reactions. By borrowing what are now everyday techniques in nuclear physics (modulation of the beams; mass analysis and counting of detected ions) it appears possible to gain from four to six orders of magnitude.

Analysis of the problem of accelerating ions in a Thomas cyclotron has been confined almost entirely to the integration of various equations of motion (for single particles) for which a complete field description is necessary. In contrast, the problem of principal interest to rf system engineers concerns the gross transfer of electrical energy from an rf generator into an accelerated beam.

The intuitive concept that a sector shaped centrifuge cell is free from convection is criticized. Not only is a form of convection present for a single sedimenting species, but a more insidious type occurs in a mixture having an appreciable Johnston-Ogston effect. Rather than striving for convection-free sedimentation, the proposal is to utilize if possible an apparently harmless type of convection occurring in a very thin annulus in order to avoid the convection extending between boundaries in a mixture. The requirement that the concentrations be independent of time meets this condition and yields a hyperbolic cell, which is approximated by a sector cell placed in the rotor backwards. Simultaneously, area measurements and calculations involving the Johnston-Ogston anomaly are simplified because of the time independence.

Quarterly progress reports on various projects in the Chemistry Division.

Measurements were made on the full scale drift tube magnets to check values predicted from the model magnets measurements. These investigations were carried out by the magnetic measurements group.

We have preliminarily reported the interpretation of our experimental results that the intensity of the spectrum at the maximum energy was zero. But, as reported in the second paper UCRL-1261 we found that the results may also be fitted to a different spectrum with finite intensity at the maximum energy. Quite recently, however, the most probable value for the mass of the p-meson has been revised by two independent groups based on two different experiments.

The root locus method of the treatment of stability problems in the field of servomechanisms is briefly summarized. A simple mechanical instrument of the analogue type (a summing device) containing no gear mechanisms, and designed to do most of the numerical work of the root locus method, is also described.

The previous calculation of the energy spectrum of the high energy deuteron beam from the stripping of He3 (UCRL-2150) was thought to be in error, especially as regards the low energy tail, on the basis of some experiments with the neutron time-of-flight detector, which indicated a considerably narrower spectrum than that calculated in UCRL-2150. Since the value used for the attenuation cross section of deuterons in uranium is considerably lower than that presently considered correct a new calculation was made using this latter cross section. Since the equations used in this new calculation differ somewhat from those used in the previous report a brief derivation is given here.

A "particle" of charge Ze moves with velocity v, mass M, energy [formula], through a "substance" of atomic number Zo, density N atoms/cm3. We have to consider the process of slowing down, and the nature of the trail of ions produced. Very slow particles are of little interest, as their range is very short. If Z is large, or if the particle is an electron, there are complications which we postpone. Thus, our considerations will apply particularly to protons, deuterons, o< -particles, and mesons.

The Bevatron requires an intense source of high energy protons. The machine should accept monoenergetic protons for a duration of approximately 500 microseconds once every 6 seconds. To satisfy the requirements of small loss due to scattering by the gas in the accelerating chamber, a 9.9-Mev linear accelerator has been built and operated.