LRL has the responsibility of demonstrating the feasibility of a reactor for use as a power plant for a low-altitude, high-Mach-number missile. This reactor is literally a very high power air heater which must work at temperatures in excess of 2000' F. The reactor is exposed to high loads so one of the primary problems is providing high temperature structure. Considerable effort has been devoted to developing ceramic structural elements. One of the materials considered for this purpose is silicon nitride. In ceramic structural elements operating over large temperature ranges, a major problem is coping with thermal stress. In this respect there is a similarity with the radome problem. The work on silicon nitride at LRL consisted of limited fabrication studies (principally for familiarization), measurement of properties of interest to the application, and funding of fabrication scale-up efforts.

Use of that portion of the characteristic curve of photographic film in which transmission is linear with log exposure eliminates the distributional error and thus makes possible the assessment of total mass of an inhomogeneously distributed cell consistent without scanning or measuring the cell's projected area. Measurement consists of obtaining the difference in output of a photocell receiving the total light transmitted by a photomicrograph of the cell, and a photomicrograph of the microscope field illumination against which the cell was photographed. A method of making such measurements is given, and its basis is described.

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 proposed to test gaps corresponding to deuteron energies in the range of 0.45 to 4.5 Mev. The accelerator to be modeled is a 48 mc/sec cylindrical cavity in the TM010 mode with [formula] repeat length, [formula] gap, 0.25 megavolt per cavity foot peak r.f. gradient and strong focusing magnets alternating polarity at each drift tube.