R. B. Mendell

Fast-Neutron Detector with Discrimination against Background Radiation

A detector that measures neutrons between 1 and 10 MeV in a mixed background of charged and neutral radiation was developed for use in cosmic‐ray studies. The detector consists of liquid scintillator NE213 surrounded by a thin shield of plastic phosphor NE102 for charged particle rejection. Both scintillators are viewed by a single photomultiplier, in an adaptation of the pulse‐shape discrimination technique.

Plateau Slopes and Pulse Characteristics of Large, High‐Pressure BF3 Counters

Factors affecting the flatness of plateaus of BF3 neutron counters of large radius and at high pressure were investigated. Counters prepared using special purification techniques showed improved characteristics. Counters of cathode radius from 1.91 to 5.06 cm were filled to pressures of BF3 from 40 to 64 cm Hg, and their pulse‐height distributions were compared. Results are discussed in terms of electron attachment in BF3 and space charge effects.

Photography of the eclipse of 7 March 1970 from two locations

In an effort to detect motion of material in the corona, photographs were made with identical cameras from Nejapa, Mexico and from Kinston, North Carolina, U.S.A. The time separation of these two places from the point of view of the Moons shadow arrival is almost exactly one hour. Two Questars, equipped with Nikon camera bodies were employed. The focal length is such (1440 mm) that the corona just nicely fills a standard 35 mm frame. Eastman XR film was used, in order to look at various radial portions of the corona, and a range of exposures from 0.1 to 4 s was programmed. The intent of the experiment was to seek some identifiable feature such as a condensation or intenser region and to determine whether it had moved appreciably in the time available. No motion was detected in any feature observable, from which a conclusion is drawn that the velocities were less than about 20 km/s. The data was sought in connection with our studies of the possible mechanisms of acceleration of particles in the Sun.