Gridded Ionization Charbberの特性とその応用

抄録

A gridded ionization chamber has been constructed; its saturation characteristics, energy resolution, and the pulse-height-versus-energy relation and performance of electronic circuits are determined.
The energy resolution of 60 KeV in half width was attained for a 6 MeV peak; r.m.s. noise in this case (about 500 in electronic charges) was 20 percent larger than the calculated value.
Both the saturation value of the pulse-height and the energy resolution were found to depend on the pressure of gas in the chamber.
Pulse-shape and pulse-height analyses of grid-signals are made as a preliminary test for possible applications of grid-pulses to electronic collimation and measurement of angular distribution of (n, α) or (n, ƒ) reactions. In particular, a “double-grid” arrangement is tried to eliminate the undesirable capacitive coupling between grid and collector.
With the chamber, a study of air-borne radioactivity is made. The concentration of Pu-239 in 1957 at Tokyo was determined to be at least 10^-20 curie/litre.
Also, the Q-value of the N¹⁴ (n, α) B¹¹ reaction is measured, with special attention to the pulse-height vs. energy relationship at lower alpha-energies. The Q-value obtained was in a better agreement with the current mass-Q-value than that found by previous authors. Furthermore, drift velocities of electrons in argon gas are determined from the pulse-shape.