S.T. Emerson

Three-body break-up in 7 Li(d, n α) 4 He and 7 Li(d, αα)n reactions

Abstract The reaction 7 Li(d, n α) 4 He has been studied detecting neutron-alpha coincidences. The energies of the detected particles were determined by means of time-of-flight measurement for neutrons and a silicon, surface-barrier detector for alphas. Simultaneously alpha-alpha coincidences from 7 Li(d, αα)n were detected using two solid-state detectors. The measurements were performed at bombarding energies from 2.6 to 4.0 MeV in steps of 0.2 MeV. In addition the reaction 7 Li(d, αα)n was studied separately at 4.0 and 9.0 MeV for several angular settings of the two solid-state detectors. The most important reaction mechanism is found to be sequential decay through intermediate 5 He and 8 Be states.

CHARGED PARTICLE MASS IDENTIFICATION.

Abstract A time-of-flight particle identification technique has been developed and applied for charged particles in the range from mass 1 to mass 9, and from 0.5 MeV to 10 MeV. The technique has the advantage of wide dynamic range and also affords a significant reduction in the background of random coincidences.

METHOD FOR NEUTRON DETECTION EFFICIENCY MEASUREMENTS AND NEUTRON--CHARGED PARTICLE COINCIDENCE DETECTION.

A simple and straightforward method for experimentally determining neutron time-of-flight detector threshold and efficiency as a function of neutron energy is presented. A procedure for neutron-charged particle coincidence studies is included also.

Neutron time-of-flight facility at rice university

Abstract A neutron time-of-flight facility in the T.W. Bonner Nuclear Laboratories at Rice University, developed in connection with the EN tandem Van de Graaff accelerator, is presented. The details of the pulse shape discrimination and neutron detection as well as the beam pulsing and bunching are described. Characteristic neutron detector efficiency data and neutron T-o-F spectra are shown.

The 11B(p, 2α)4He reaction at the 163 keV resonance

Abstract The 11 B(p, 2 α ) 4 He reaction has been studied at a bombarding energy of 163 keV to complement the previous measurements at energies of a few MeV. Many two-parameter spectra have been taken, both around the 8 Be ∗ recoil axes and at selected angles away from the recoil axes. Coplanar and non-coplanar cases for the three alpha particles have been studied. Analysis yields results similar to those found previously for the higher bombarding energies but in dis-agreement with the conclusions of Dehnhard. Strong sequential decay through the 8 Be ∗ states has been observed with very little or no evidence for simultaneous three-alpha decay.

FINAL-STATE INTERACTIONS IN THE

Abstract The 9 Be + p → d + 2α reaction has been studied at a proton bombarding energy of 9.0 MeV, by the coincident detection of pairs of reaction products. Mass identification of one detected particle has been accomplished using a time-of-flight technique. The reaction yield has been shown to be dominated by final-state interactions through states in 8 Be and 6 Li, with little or no yield from direct three-body disintegration. Theoretical fits to the data using the generalized density of states functions reproduce quite accurately the shapes of the spectra. Efforts to fit the angular dependence of the yield have met with limited success.

sup 9

Abstract The 9 Be + p → d + 2α reaction has been studied at a proton bombarding energy of 9.0 MeV, by the coincident detection of pairs of reaction products. Mass identification of one detected particle has been accomplished using a time-of-flight technique. The reaction yield has been shown to be dominated by final-state interactions through states in 8 Be and 6 Li, with little or no yield from direct three-body disintegration. Theoretical fits to the data using the generalized density of states functions reproduce quite accurately the shapes of the spectra. Efforts to fit the angular dependence of the yield have met with limited success.

Be + p

Abstract Three-body reactions resulting from 6Li + d at a deuteron bombarding energy of 10 MeV have been studied by the coincident detection of two charged-particle reaction products in silicon surface barrier detectors. Mass identification of one of the particles has been accomplished using a time-of-flight technique. Final-state interactions are observed through states in the possible intermediate nuclei. Decay through excited states of 4He near 20.2 and 21.9 MeV was observed but with branching ratios significantly different from those previously reported. Interference effects were observed in the d-d and α-d coincident spectra.

Yields

Abstract The 2 H(p, pn) reaction has been studied at a bombarding energy of 9.0 MeV and several coincidence detection angles using the Rice University tandem Van de Graaff accelerator and computer-analyzer system. The energies of the detected, coincident particles were determined using a solid-state surface barrier detector for the proton and time-of-flight measurement on the neutron. The contributions of the neutron-proton final state interaction and neutron-proton quasi-free scattering have been observed. The final state interaction contribution has been reproduced using Phillips, Griffy and Biedenharn theory. The shape of quasi-free scattering contribution spectrum is in reasonable agreement with simple impulse approximation prediction. The absolute value of cross section is smaller than predicted by spectator model calculations.