Axial observables in d-->p--> breakup and the three-nucleon force.

We have measured three axial polarization observables in d-->p--> breakup with a polarized 270 MeV deuteron beam on a polarized proton target. Axial observables are zero by parity conservation in elastic scattering but can be easily observed in the breakup channel at the present energy. Based on a symmetry argument, the sensitivity of these observables to the three-nucleon force might be enhanced. Calculations without three-nucleon force are in fair agreement with our measurement, indicating that the expected sensitivity of axial observables to the three-nucleon force is not confirmed. Including a three-nucleon force in the calculation does not improve the agreement with the data.

Vector and tensor polarization lifetimes for a stored deuteron beam.

The time dependence of the vector and tensor polarization of a 270 MeV stored deuteron beam was measured near a depolarizing resonance, which was induced by an oscillating, longitudinal magnetic field. The distance to the resonance was varied by changing the oscillation frequency. The measured ratio of the polarization lifetimes is tau(vector)/tau(tensor)=1.9+/-0.2. Assuming that the effect of the resonance is to induce transitions between magnetic substates m(I), we find that the transition rate between neighboring states (+1 and 0 or -1 and 0) is four times higher than between the states with m(I)=+1 and -1.

First spin flipping of a stored spin-1 polarized beam.

We recently studied spin flipping of a 270 MeV vertically polarized deuteron beam stored in the Indiana University Cyclotron Facility Cooler Ring. We adiabatically swept an rf solenoid's frequency through an rf-induced spin resonance and observed its effect on the deuterons' vector and tensor polarizations. After optimizing the resonance crossing rate and maximizing the solenoid's voltage, we measured a vector spin-flip efficiency of 94.2%+/-0.3%. We also found striking behavior of the spin-1 tensor polarization.

Measurement of analyzing power for proton-carbon elastic scattering in the coulomb-nuclear interference region with a 22-GeV/c polarized proton beam.

The analyzing power for proton-carbon elastic scattering in the Coulomb-nuclear interference region of momentum transfer, 9.0x10(-3)<-t<4.1x10(-2) (GeV/c)(2), was measured with a 21.7 GeV/c polarized proton beam at the Alternating Gradient Synchrotron of Brookhaven National Laboratory. The ratio of hadronic spin-flip to nonflip amplitude, r(5), was obtained from the analyzing power to be Rer(5)=0.088+/-0.058 and Imr(5)=-0.161+/-0.226.

Nuclear polarization of hydrogen molecules from recombination of polarized atoms.

The nuclear polarization of H(2) molecules formed by recombination of polarized H atoms on a Cu surface was measured as a function of external magnetic field and of temperature of the surface. The proton polarization of the molecules was determined by scattering of a longitudinally polarized 203-MeV proton beam in the Indiana University Cyclotron Facility storage ring. The nuclear polarization of the molecules, relative to the polarization of the atoms before recombination, increased from near zero in a weak magnetic field to 0.42 +/- 0.02 in a 0.66 T field. A simple model of the relaxation accounts quantitatively for the observations.

Design of a three-dimensional positron camera for nuclear medicine.

A positron camera is proposed for nuclear medical imaging of radionuclide distributions in a series of isolated planes. This three-dimensional localisation is achieved through analysis of four time signals, whose differences directly measure the position (x, y, z) of individual positron annihilation events. A tetrahedronal symmetry is exploited, with two skewed plastic scintillator bars spanning a large sensitive volume. Phototubes on each end of both bars generate fast timing pulses uniquely determining the decay position through a time-of-flight technique. The mathematical properties of the transformation from the observed quantities to the spatial distribution of the radionuclide are investigated. A discussion of the efficiency of the system and the effects of Compton scattering in tissue is given. A one-dimensional pilot study encourages the development of the prototype three-dimensional positron camera.

Mineral inclusions in diamond: temperature and pressure of equilibration.

Two distinct suites of minerals included in natural diamond occur and probably represent different physical and chemical conditions during diamond growth. Minerals of the ultramafic suite appear to have equilibrated in the range 1000 degrees to 1300 degrees C between 45 and 65 kilobars, whereas the temperature range for minerals of the eclogitic suite is 850 degrees to 1250 degrees C. At present, models relating the partitioning of magnesium and iron between coexisting phases are not sufficiently rigorous to determine a value for the pressure of equilibration of these eclogitic suite inclusions.

Chrome pyrope: an inclusion in natural diamond.

Electron probe analyses of garnets that are rich in magnesium and that occur as inclusions in natural diamonds show that the chrome-garnet end member, Mg(3)Cr(2)Si(3)O(12), is a major constituent (30 percent).