H. R. Crane

Measurements of the Mobilities of the Negative Ions in Oxygen and in Mixtures of Oxygen with the Noble Gases, Hydrogen, Nitrogen, and Carbon Dioxide

The mobility constants for oxygen negative ions in He, Ne, A, Kr, Xe, H2, N2, and CO2, each containing various partial pressures of O2 were measured, and extrapolations to zero partial pressure of O2 were obtained. A measurement of the mobility of the negative ion in 100% oxygen was also made. The value found for the latter was 2.46±0.05 cm2/v‐sec at STP. It was shown that the mobility values referred to a single species of oxygen ion, but the question as to whether it was O2− or O3− was not resolved. A time‐of‐flight method was used, in which the ions were made by the passage of alpha particles through the gas, and detected by a proportional counter.

CO2‐CS2 Geiger Counter

Experiments on the mechanism and characteristics of a CO2‐CS2 Geiger counter are reported, and circuits and methods of operation which satisfy the special requirements are described. Counter: The active part is 2⅞ in. in diameter and 16 in. long, filled to 1 atm, 95% CO2 and 5% CS2. The cathode is copper and the anode is 0.005‐in.‐diam Chromel A. Characteristics: The electrons released by an ionizing particle become attached, probably to CS2. The self‐quenching action of the counter is excellent, no spurious counts are observed in the absence of electronic quenching. However, a dead time of several milliseconds must be imposed electronically because of the long interval during which the negative ions arrive at the anode. Method: An electronic quench is used which is triggered both by the CO2‐CS2 counter and the anticoincidence ring. This serves to impose the required dead time and also to prevent the firing of the CO2‐CS2 counter by mesons. Measurements: The plateau was measured to 1900 v above threshold ...

Experiments on the Design of Synchrotron Magnets

An important aspect of the problem of synchrotron magnet design is that of obtaining a given magnetic energy in the guide field with the minimum expenditure of iron, copper, and condensers. Tests were made on d.c. magnet models of several configurations, using as criteria (1) the ratio of the peak energy in the useful portion of the magnet air gap to the peak energy which must be stored in the condensers, and (2), the ratio of magnetic flux in the gap to the flux in the return path of the magnetic circuit. Comparative performance data are tabulated. The method of shaping the pole faces to obtain the desired fall‐off of B with r over the greatest range in r is discussed, and a shape worked out by trial and error is given.

Cloud Chamber for Nuclear Disintegration Studies

Construction of an entirely automatic cloud chamber particularly adapted to the study of the high energy electrons produced in artificial disintegration experiments is described. Air core coils which are capable of producing magnetic field strengths up to 4000 gauss at the time of expansion are used. An incandescent light source, using three 1000‐watt projection bulbs furnishes sufficient light for ⅕ second camera exposure.