The Debrecen superconducting magnetic spectrometer (SMS) has been adapted for in-beam internal-pair studies. Test measurements have been carried out using a 207Bi radioactive source and the 19F(p, αγ)16O, 23Na(p, αγ)20Ne, 27Al(p,p′γ)27Al and 42Ca(p, p′γ)42Ca reactions (at bombarding energies Ep = 3.5-4.0 MeV). Convenient spectrometer parameters, backscattering of electrons and positrons from one detector to the other, and methods for background reduction have been investigated. Experimental values of (14±3)%, (12±3)%, and (14±2)% for the one-detector pair-line efficiencies were determined for the 20Ne(E2; 1634 keV), 42Ca(E0; 1837 keV) and 27Al(M1 + E2; 2211 keV) transitions, respectively. The observed pair-line detection efficiencies for two detectors operated in sum-coincidence mode were (35 ± 7)% and (34 +-6)% for the 42Ca(E0; 1837 keV) and 27Al(M1 + E2; 2211 keV) transitions, respectively. The energy resolution of the spectrometer was ≈ 0.5% in singles and ≈ o.6% in sum-coincidence measurements for the 2211 keV M1 + E2 pair line of 27Al. Effective pair-formation coefficients for one-detector and opposite two-detector geometries have been calculated theoretically for various multipoles. Different methods for the determination of the multipolarity of internal-pair transitions have been investigated. Optimum multipole discrimination effects have been discussed. The experiments show that a good multipole discrimination power can be achieved with the SMS.
|Number of pages||7|
|Journal||Nuclear instruments and methods in physics research|
|Publication status||Published - Jun 1 1984|
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