Precision Wave-Length Measurements of the 1.1- and 1.3-Mev Lines of CO60with the Two-Meter Focusing Curved-Crystal Spectrometer

Abstract

Recent improvements in the two-meter focusing curved-crystal gamma-ray spectrometer are described which have extended its quantum energy range well above 1 Mev and have also yielded much better luminosity and resolving power than were obtained initially. The improved components are (1) the crystal holder whose aperture and resolving power have been nearly doubled and (2) the collimator the new model of which can now discriminate between the reflected and transmitted beams when these differ in direction by only 8 minutes of arc, a threefold improvement over our first model. Our plans for further possible improvements and the factors governing these are also discussed. Wavelengths of two gamma-rays emitted following $\beta$-decay of ${\mathrm{Co}}^{60}$ have been measured with this new equipment using a source of about 50 mc strength and found to have values of (9.308±0.005)×${10}^{-11\mathrm{}}$ cm and ${(10.580\mathrm{}\pm 0.005)\times 10}^{-11\mathrm{}}$ cm corresponding to quantum energies of 1.3316±0.0010 Mev and 1.1715±0.0010 Mev, respectively. The lines appear to have equal intensities. The integrated reflection coefficient of the (310) planes of the curved-quartz crystal still appears to follow a ${\lambda }^2$-dependence on wave-length down to 9 x.u. the shortest so far observed.