C.B. Fulmer

Fission-fragment mass separator and the nuclear charge distribution of fission fragments of a single mass

Abstract An energetic fission fragment passing through a gas changes its charge frequently by electron capture and loss collisions with gas molecules. Its average charge e is found to be very nearly proportional to velocity, so that magnetic deflection depends only on the mass; thus, passing fission fragments through a gas-filled magnetic spectrograph gives mass separation. At low pressure the resolution is limited by the statistics of the electron capture and loss process; increasing the pressure to reduce this effect is eventually limited by energy loss and the resulting multiple scattering. However, before this occurs there is a pressure range where the resolution is limited by the nuclear charge distribution of fragments of a single mass. All of these effects were studied experimentally. The best resolution obtained for mass-97 fragments was 3.5 % full width at half maximum (with 20 mm-Hg of helium), of which 2.2 % is due to the width of the nuclear charge distribution. Combining this with the results of a study of the dependence of e on nuclear charge, gives the width of the nuclear charge distribution for mass-97 fragments as 2.4±0.5 units. This is in agreement with determinations from yields of shielded isotopes, but is in disagreement with the predictions of most theories. The best obtainable resolution from the mass separator is 4.5 mass units for light fragments. Several applications of the separator are described and others are suggested.

Levels in 140,142,144Nd and a search for pairing vibrations at N = 82 with the (p, t) reaction

Abstract The 142,144,146 Nd(p, t) reactions were studied with 31 MeV protons. A pair-vibrational like state is observed in the 144 Nd(p, t) reaction but shifted in energy and with less intensity than expected. Although no such state is seen in the 146 Nd(p, t) reaction, the same L = 0 intensity to excited states is observed to be distributed among a number of 0 + levels.

The (d,3He) reaction on 126Te, 128Te and 130Te nuclei

Abstract The (d,3He) reaction was employed to study the shell-model composition of the ground states of 126Te, 128Te and 130Te. The study was performed with a 34 MeV deuteron beam from the Oak Ridge Isochronous Cyclotron. A silicon counter telescope was used to detect the 3He particles. Angular distributions for the 3He groups were compared with DWBA predictions to obtain angular momentum transfers and spectroscopic factors. States were observed corresponding to the removal of protons from the 1 g 7 2 , 2 d 5 2 , 2 d 3 2 , and 3 s 1 2 shell-model orbits. In additions, states are populated which are due to pick-up of 1 g 9 2 , 2 p 1 2 and 2 p 3 2 protons from the next (lower) shell. The Q-value of the 130Te(d,3He)129Sb reaction was measured to be −4.55±0.03 MeV; it significantly increases the accuracy of the measured mass for 129Sb.

Analysis of 50.8 MeV proton scattering from the samarium isotopes

Abstract An analysis was made of proton scattering from the ground and first 2+ state of the stable even isotopes of samarium at 50.8 MeV. The analysis of the elastic scattering was in terms of the simple optical model and of the reformulation by Greenlees, Pyle and Tang in terms of nuclear matter distributions and the nucleon-nucleon force. Angular distributions for the lowest 2+ levels were fitted by using the collective model in the DWBA and by a coupled channels analysis. Predictions are also presented to fit scattering data from the lowest 4+ level of 154Sm. The implications and conclusions of each type of analysis are compared to determine which effects are model dependent. Systematic trends depending on target mass were observed for the parameters of all the models used. In particular both the volume integral and the depth of the real central potential decrease with increasing deformation, and the volume integral of the imaginary potential increases.

Excitation functions for radioactive nucleides produced by deuteron-induced reactions in copper

Abstract Cross sections were measured for the production of radioactive nucleides by deuteron-induced reactions in natural copper at bombarding energies up to 40 MeV. Stacked foil targets were bombarded with douterons from the Oak Ridge Isochronous Cyclotron. Gamma spectra of individual foils were measured with a Ge(Li) spectrometer. Excitation functions were obtained for 61Cu, 62Cu, 64Cu, 66Cu, 62Zn, 63Zn and 65Zn. Yields for 63Cu(d,xn) reactions show a strong dependence on level density of the residual nucleus.

Target-spin effects on elastic scattering cross sections☆

Abstract It is shown, using a simple model and empirical results, that the odd-even differences in the scattering of He ions from 59 Co and 60 Ni can be explained as due to the scattering from the quadrupole moment which is allowed for the odd target nucleus but not the even.

Energy levels of 94Ru observed with the 96Ru(p, t) reaction

Abstract The level structure of the neutron-magic nucleus 94 Ru, up to an excitation energy of 4 MeV, has been studied by means of the (p, t) reaction. Particular emphasis was placed on a search for excited 0 + levels, none of which have been reported previously. Among new levels observed in this study are 0 + levels at 2.995, 3.615 and 3.770 MeV, and the 3 − octupole vibration at 2.965 MeV.

Elastic scattering of 50.8 MeV protons from the even samarium isotopes

Abstract Angular distributions were measured over the angular range of 12° – 130°. Forward of ≈60° the angular distributions are very similar; at larger angles the amplitude of the oscillations increases and the cross sections decrease with increasing target deformation.

Target-spin dependence observed in 50 MeV 3He elastic scattering☆

Abstract Elastic scattering of 50 MeV 3He ions from 59 Co (J = 7 2 ) and 60 Ni (J = 0) was measured over the angular range of 12° to 130°. A significant difference was observed in the large-angle scattering from the two targets. This is interpreted as arising from a target spin dependence in 3He elastic scattering.