Superallowed ?-decay energies of 34Cl and 26Alm
Abstract (Summary)Restricted Item. Print thesis available in the University of Auckland Library or available through Inter-Library Loan. Accurate measurements were made of the energies of (i) 33S(p,?)34Cl resonance at 975 keV, 1543 keV and 1995 keV (ii) 25Mg(p,?)26Alm resonance at 1375 keV and 1587 keV (iii) The corresponding excitation energies and (iv) 27Al(p,?)28Si resonance at 992 keV and 1317 keV. Threshold energies of (i) 34S(p,n)34Cl reaction at about 6460 keV (ii) 27Al(p,n)27Si reaction at about 5804 keV and (iii) 26Mg(p,n)26Alm reactions at about 5209 keV were also measured with the view of obtaining more accurate Ft values for the superallowed ?-decays of 26Alm and 34Cl nuclei. An "Enge split-pole magnetic spectrograph" and the 4MV folded tandem AURA II accelerator at Auckland University were used. Proton energy was determined by making them follow a precise geometrical path within the spectrograph and then accelerating heavy ions (either K+ or Cs+) through a high voltage before entering the spectrograph such that they follow the same precise path as the proton beam. The high accelerating voltage was then measured using a specially constructed resistor divider and a 1volt standard which is calibrated regularly against international standards. Application of minor corrections led to the required proton energies. All (p,?) reaction yields were measured as a function of proton energy and resonance energies were extracted by finding the proton energy at the mid-point of the rise in the yield curve. All (p,n) reaction yields were obtained using a pair of plastic scintillator detectors in coincidence and threshold energy extracted after fitting the experimental yield to an expected function of proton energy. The excitation energies were measured with an HPGe detector by selecting suitable cascades of de-excitation gamma rays. Corrections were made for the effects of non-uniform energy loss by protons in target material and finite energy width of the proton beam. Following results were obtained: (i) 27Al(p,?)28Si resonance at 992 keV: (991.77±0.01) keV (ii) 27Al(p,?)28Si resonance at 1317 keV: (1316.89±0.01) keV (iii) Threshold energy for 27Al(p,n)27Si: (5804.29±0.04) keV (iv) ?-decay energy of 26Alm: (4232.40±0.05) keV (v) ?-decay energy of 34Cl: (5490.23±0.23) keV The first three quantities above can be used as calibrations for proton energy measurements. The last two quantities are used to evaluate the ft values which are used to test the conserved vector current hypothesis of the weak interaction.
School Location:New Zealand
Source Type:Master's Thesis
Date of Publication:01/01/1993