The electric resistivity changes induced by the 12-Mev deuteron bombardment of Cu, Ag, Au, Ni, and Ta foils were determined as functions of the integrated flux. Bombardments were carried out at about -140°C and -150°C, and differences in the two sets of measurements were traced to a thermal recovery process which was proceeding with measurable velocity even at -165°C. This low temperature reaction was characterized by an activation energy of 0.2, ±0.05 ev for Cu, Ag, and Au, and one of 0.3, ±0.1 ev for Ni and Ta. It is suggested that the migration of vacancy pairs offers a reasonable model for the initial recovery process, although other mechanisms are also discussed.
Electrical resistivity increases produced by 12-Mev deuteron irradiation were measured as a function of integrated deuteron flux in Cu, Ag, and Au. The bombardment temperature was near 10°K and no thermal recovery of the irradiation effects was observed; however, evidence that appreciable radiation annealing occurred during the bombardment was found. The resistivity increases near 10°K were much larger than those previously obtained in these metals for equal irradiations made near liquid nitrogen temperature. The observed Z-dependence of the irradiation effects agreed closely with that predicted by Seitz's theory.Warmups made following the bombardments revealed that 40 to 50 percent of the total resistivity increase in Cu recovers near 43 °K and from 13 to 24 percent of that in Ag anneals near 30°K; the rapid recovery in each case indicates that a unique process may be involved, and the associated activation energy is estimated to be 0.1 ev for both. It is suggested that volume diffusion of interstitial atoms or annihilation of very close interstitial atom-vacancy pairs are two possible processes responsible for the low temperature recovery. In addition, for all three metals, a gradual annealing rate was observed in the intermediate temperature range 50°K-220°K, and then a more rapid rate took place in the range 220°-280°K.
Fifty-five ultraviolet laser transitions in the wavelength region 2300–4000 Å have been observed from the ions of N, O, Ne, Ar, Kr, and Xe. The electron transition is p → s for all identified lines, with the exception of two xenon transitions which are p → d. Threshold currents for laser action in a 4-mm-bore tube were in the ranges 10–100, 100–500, and >400 A, respectively, for singly, doubly, and triply ionized atoms. Current saturation and current quenching of laser action both were observed. Results with two tube bores show that the usual inverse relation between gain and tube diameter does not hold in ultraviolet ion lasers.
Friday, Octo 28, 9:OO a.m. to NoonThe pulse width of a &-switched CO,-N,-He laser operating at 1 0 . 6~ setts Institute of Technology, Cambridge, Mass.has been directly measured with a Au:Ge (77O ) detector to be less than or pressure the beat frequency between two longitudinal modes has been ob-equal to 25 nanoseconds. For a 3 meter CW COZ laser operating at low served using the fast Ge:Au detector. When the laser transitions are pressure broadenemd, the laser tends to *operate in a single mode. During Qswitched operation at 1 0 . 6~~ two new groups of laser oscillations have been
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