Browsing by Author "Tshivhase, Victor Makondelele"

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    The study of Gamow-Teller strength in the 51V(p,n)51 Cr reaction at intermediate energies
    (1992) Tshivhase, Victor Makondelele; Aschman, David G
    The ⁵¹V(p,n)⁵¹Cr reaction was studied at four different proton beam energies namely 90, 120, 160, and 200 MeV. The experiment was performed in the angular range between 0 and 4°, using the beam swinger facility at National Accelerator Centre(NAC) at Faure, near Cape Town. The cross sections of the ground state, Isobaric Analog State, and the giant Gamow-Teller resonance were calculated at 0° for each beam energy. The ratio of the cross section of the giant Gamow-Teller resonance to the cross section of the Isobaric Analog State were studied at beam energies 90, 120, 160 and 200 Me V, and beam angles 0, 2 and 4 °. The Gamow-Teller strength was estimated for energies 120, 160 and 200 MeV. The fractions of Fermi and Gamow-Teller strength in the Isobaric Analog State were also estimated.
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    A study of Gamow-teller strength using the 208Pb(p,n) and 181Ta(p,n) reactions at intermediate energy, Ep=122 MeV
    (1997) Tshivhase, Victor Makondelele; Aschman, David G
    The Gamow-Teller strength was measured in ²⁰⁸Pb(p,n)²⁰⁸Bi and ¹⁸¹Ta(p,n)¹⁸¹W reactions at an incident proton energy of 122 MeV. The experiment was performed using the beam-swinger facility at the National Accelerator Centre, Faure, South Africa. The time-of-flight(TOF) technique was employed with a flight-path of 100 m. Detectors comprised three stacks of four rectangular bars of NE 102A plastic scintillators. The outgoing neutrons were observed at laboratory angles, ΘLab = 0°, 2°, 4° and 10° . A multipole decomposition analysis of spectra associated with ²⁰⁸Pb(p,n)²⁰⁸Bi and ¹⁸¹Ta(p,n)¹⁸¹W reactions was performed using the results of distorted-wave impulse approximation (DWIA) calculations. The spectra associated with the two reactions were decomposed into L=0,1 and 2 transfer components. The major contribution to the spectra were found to be L=O, with a very small 1=2 multipole transfer contribution. The spectra were modelled with a combination of symmetrical Gaussians and a polynomial background. The GT strength was extracted by normalizing the cross section of the GT states to the cross section of the isobaric analogue state. The ΣB(GT) strength associated with the ²⁰⁸Pb(p,n)²⁰⁸Bi and ¹⁸¹Ta(p,n)¹⁸¹W reactions was found by summing the individual GT strength in the 0 - 23 MeV and 0 - 20 MeV excitation regions respectively. The ΣB(GT) strength associated with the ²⁰⁸Pb(p,n)²⁰⁸Bi and ¹⁸¹Ta(p,n)¹⁸¹W reactions were found to be less than the values predicted by the 3(N - Z) sum rule, being 81 ± 10% and 78 ± 3% of the sum rule strength respectively.