The "absolute" containment of ions in the DCX magnetic mirror field resulting from the cylindrical symmetry of the field is discussed. The regions of confinement in space and momentum are plotted for 300 Kev deuterons.

Preliminary experiments have been conducted to evaluate the use of the nuclear reactions Li6 (n,α)H3 and O16(H13,n)F18 to determine the thickness of oxide films on metals. Sheets of thin paper and of aluminum, imbedded in powdered LiF, were irradiated with pile neutrons at a flux of 6 x 10^11 n/cm^2/sec and counted with an end-window proportional counter. A saturation activity of 1.87 hr F18 of 150 dis/min per microgram of oxygen was observed in the paper, but radioactivity due to impurities masked F18 in the aluminum. It is concluded that a 1 A (0.01 μgm/cm^2) oxide film thickness may be measured by a neutron irradiation at a flux of 10^14 n/cm^2/sec but chemical separation of induced radioactivity from the bulk metal is essential.