The Thirty Kilowatt Continuous Input X‐Ray Equipment and High Constant Voltage Generating Plant of the Watters Memorial Research Laboratory at the California Institute of Technology

This report describes in detail with photographs and cross‐sectional views an x-ray tube with a gyrating water‐cooled target which the authors have operated continuously for periods of hours at 287,000 volts and 105 milliamperes. The theoretical predictions of DuMond, Watson and Hicks as to the ratio of safe load in moving and fixed targets seems to be roughly fulfilled by these results. The computed power output in the form of x-rays alone is some 3/4 kilowatt. The report further describes in detail the power supply equipment consisting of a synchronous motor driven 40 kw motor generator set giving 150 cycle current both half-waves of which, after transformation to high voltage, are rectified by two thermionic valves (filament emission 2 amperes maximum) of our own design and construction here fully described. The powerful electrical filter system to reduce the ripple to a low value and some technical problems arising from the large power rating of the equipment as well as the facilities now almost completed for stabilizing and measuring precisely the high voltage supplied to the x‐ray tube are discussed. At the outset a brief indication of the program of research work projected for this set is given

Decays of Ta182 and Ta183

The beta - decays of Ta182 and Ta183 into excited states of W182 and W183 have been studied using a curved crystal gamma-ray diffraction spectrometer and a homogeneous field, ring focusing beta-ray spectrometer. In each case de-excitation of the daughter nucleus gives rise to complex gamma-ray and conversion electron spectra. Energies and relative intensities of gamma rays and conversion lines arising from 27 transitions in W182 and 29 transitions in W183 are presented. Internal conversion coefficients and multipolarities have been deduced for most of the transitions and together with the gamma-ray energies form the basis of decay schemes proposed for both W182 and W183. The two decays are reported together because of the close experimental relationship which existed between them as a consequence of the method used for their production, namely, simultaneous production of Ta182 by single neutron capture and Ta183 by double neutron capture from stable Ta181. A corollary result is the value 1.3 x 10^4 barns for the thermal neutron cross section of Ta182. An interpretation of these results on W182 in terms of collective rotational motion has been given by A. Bohr and collaborators [Kgl. Danske Videnscab. Selskab, Mat.-fys. Medd. 29, No. 9 (1955)]

Measurement of High-Energy Gamma-Rays with a Photographic Bent Crystal Spectrograph

It has been shown by one of the authors and his coworkers that it is possible to determine accurately the wavelengths of gamma rays with quantum energies up to 1.3 Mev by direct crystal diffraction methods using the Mark I 2-meter bent crystal spectrograph at the California Institute of Technology. They were able to record and to measure with a precision of one part in 10^3 the two gamma rays at 1.17 and 1.33 Mev which are emitted by a Co^(60) source

Breadth of Compton modified line

Professors Ross and Clark of Stanford, using the ingenious balanced filter method of Ross, have investigated the shifted line in the Compton effect for antimony, Kα1 and Kα2, lines scattered from beryllium. In this method the scattering angle is varied so as to vary the shift of the modified line

Precision wave-length measurements of the 1.1- and 1.3-Mev lines of CO60 with the two-meter focusing curved-crystal spectrometer

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 β-decay of Co60 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 cm and (10.580±0.005)×10-11 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 λ2-dependence on wave-length down to 9 x.u. the shortest so far observed

Rotational and intrinsic levels in Tm169 and Lu175

Nuclear levels in Tm169 excited by electron capture of Yb169, and levels in Lu175 excited by both beta decay of Yb175 and electron capture of Hf175 have been studied by using the curved-crystal gamma-ray spectrometer and the ring-focusing beta-ray spectrometer, as well as a semicircular beta-ray spectrometer for low energies. From the precision energies and the multipolarity determinations, the levels in Tm169 have the following energies in kev, and spin and parity assignments: A (ground state) (½+), B 8.42 (3/2+), C 118.20 (5/2+), D 138.95 (7/2+), E 316.19 (7/2+), F 379.31 (7/2-), G 472.91 (9/2-). Levels A, B, C, and D are members of a rotational band whose characteristic constants are given. Levels E and F are interpreted as particle excitations and level G as a rotational level based on the state F. The Lu175 excited states have the following energies in kev, spins, and parities: A (ground state) (7/2+), B 113.81 (9/2+), C 251.46 (11/2+), D 343.40 (5/2+), E 396.31 (9/2-), F 432.76 (7/2+), G 504.7 (1/2+). A, B, and C form a rotational band for which the characteristic constants are given. Some features of the levels and transition probabilities are discussed and compared with the unified model. A brief survey of second-order rotational energy constants and of intrinsic excitation levels is given

Gamma Transitions in W182

[No abstract]