R.L. Parks

The HHIRF supersonic gas jet target facility

Abstract We describe a supersonic gas jet target built for studying reactions induced by heavy ions with high energy resolution. The device produces very localized high density gas jets in a near vacuum environment and is presently installed in the scattering chamber of a magnetic spectrograph at the ORNL HHIRF. With a 100 MeV 16 O beam collimated to a size of approximately 1 mm 2 at the target, image sizes of 0.42 mm have been obtained at the focal plane of the spectrograph with a solid angle of 2.4 msr and target densities of 15–30 μg/cm 2 .

Mass excess of 147Tb

Abstract The mass excess of 147 Tb has been determined from the Q -value measurement of the 144 Sm( 14N , 11 Be) 147 Tb reaction to be −71.00 ± 0.05 MeV. The two-proton separation energy provides little evidence for a magic proton shell closure at Z = 64.

Search for resonances in 12C(9Be, α)17O

Abstract Excitation functions at 7° (lab) have been measured from E c.m. = 5.1 to 11.4 MeV in approximately 114 keV steps for 15 groups of final states in 17 O populated by the 12 C( 9 Be, α) reaction. Statistical tests have been used to locate possible non-statistical structure in the excitation functions. Possible anomalies were found near E c.m. = 6.3, 7.5, 8.9 and 9.7 MeV. Angular distributions were measured at E c.m. = 9.20, 9.71 and 10.23 MeV for the three lowest excited states in 17 O. The data have been compared with Hauser-Feshbach calculations in addition to the following reaction mechanisms: compound plus a single resonance, compound plus interfering resonances and compound plus direct reactions.

Mass excesses of 79As, 81As, and 80Ge

Abstract Accurate mass measurements for the nuclides 79 As, 81 As, and 80 Ge have been measured. Good agreement has been found for 79 As and 81 As with the Garvey-Kelson transverse mass relation and with several mass model predictions. The agreement for 80 Ge is not as satisfactory and presents a challenge for understanding mass values far off the line of stability.

Proton-inclusive cross sections from 600 MeV proton-nucleus reactions☆

Abstract Proton-inclusive cross sections were measured for 600 MeV proton bombardment of 27Al and 181Ta targets using the SREL synchrocyclotron. Proton energies were measured with a plastic scintillator time-of-flight system, and a 10.2 cm thick NaI detector was used for particle identification. The results of classical many-body and knock-on calculations are compared with the data.

Proton inclusive cross sections from 720 MeV α-nucleus reactions

Abstract Proton inclusive cross sections have been measured from 30°–150° (lab) for outgoing energies up to 500 MeV from the bombardment of 720 MeV α-particles on Al and Ta. An exhaustive survey of applicable models indicates that the intranuclear cascade and knock-out models provide the best description of the data. Single scattering mechanisms seem to be important, and there is some indirect evidence that high nuclear density effects occur.

Comparison of fusion cross sections for 12C+12C → 24Mg and 14N+10B → 24Mg

Abstract The total fusion cross sections have been measured and compared for two light systems, 12 C + 12 C and 14 N + 10 B, leading to the same compound nucleus at the same excitation energies, E ∗ ( 24 Mg ) = 40, 50, 55 and 60 MeV . The critical angular momenta extracted for the formation of 24 Mg via 12 C + 12 C and 1 14 N + 10 B are different enough to clearly indicate the presence of an entrance channel effect (limitation). The Z -distributions of the evaporation residues are compared to each other and to Hauser-Feshbach calculations. The data are also fitted with and compared to theoretical models which predict total fusion cross sections.

Nuclear physics experiments with the ornl-hhirf supersonic gas jet target

A study of target-like fragments produced by bombarding a /sup 14/N target with 150 MeV /sup 28/Si shows that mass and charge distribution of products from orbiting processes is determined by partitioning of an equilibrated dinuclear system. The experiment was performed with the HHIRF supersonic gas jet target which is also described briefly. 6 references, 10 figures.