A feasibility study of the (3He,8He) reaction with the K600 magnetic spectrometer

Swartz, Jacobus Andreas (2010-03)

Thesis (MSc (Physics))--University of Stellenbosch, 2010.

Thesis

ENGLISH ABSTRACT: Highly exotic nuclei can be studied in rare reactions using stable beams, with macroscopic intensities, and thick targets. Exotic nuclei are interesting for a number of reasons e.g. for testing nuclear models under conditions of high isospins. In the case of very neutron-deficient nuclei, two-proton decay is the most recently discovered nuclear decay mode and the subject of many theoretical investigations involving cluster and shell models. This thesis presents a feasibility study of investigating light exotic nuclei near the proton drip line with the K600 magnetic spectrometer. The 27Al(3He,8He)22Al five-neutron pick-up reaction was investigated at a spectrometer angle of θlab = 8◦ with a beam energy of Elab = 220 MeV. This reaction can be used to populate highly neutron-deficient nuclei. Should the study of this reaction prove to be feasible, then a number of nuclei on the proton drip line or beyond could be investigated. A new data acquisition system, with VME electronics and MIDAS software, was used along with one new drift chamber, which consists of both an X wire plane and a U wire plane. The particles 1,2,3H and 3,4He were all identified as outgoing particles from the collision of 3He with 27Al. Cross section calculations were performed for these observed reactions. Discrete spectra for the (3He,6He) and (3He,8He) reactions could not be identified. The mass calculation of A ∼ 20 nuclei on the proton drip line depends on the determination of the Coulomb energy, which differs a lot between mirror nuclei. Mass calculations were performed for known nuclei in the mass region A ≤ 50, using the Isobaric Multiplet Mass Equation. Agreement with experimental data was found to be far better in odd nuclei than in even nuclei. Hence mass predictions were performed for odd nuclei along the proton drip line.

AFRIKAANSE OPSOMMING: Hoogs eksotiese kerne kan bestudeer word in seldsame reaksies deur middel van stabiele bundels, met makroskopiese intensiteite, en dik teikens. Eksotiese kerne is interessant om verskeie redes, onder andere om kernfisiese modelle te toets onder omstandighede van ho¨e isospin. In die geval van baie neutron-arm kerne is twee-proton verval die nuutste ontdekte tipe van kernverval. Dit is ook die onderwerp van vele teoretiese studies met betrekking tot bondel en skilmodelle. Hierdie tesis beskryf ‘n uitvoerbaarheidstudie vir die ondersoek van ligte eksotiese kerne naby die proton drup lyn met behulp van die K600 magnetiese spektrometer. Die 27Al(3He,8He)22Al vyf-neutron kaapreaksie is ondersoek by ‘n spektrometer hoek van θlab = 8◦ met ‘n bundel energie van Elab = 220 MeV. Sou die uitvoerbaarheidstudie van hierdie reaksie slaag, dan kan verskeie kerne op of anderkant die proton drup lyn ondersoek word. ‘n Nuwe data verkrygingssisteem, met VME elektronika en MIDAS sagteware, is gebruik saam met een nuwe dryfkamer, wat bestaan uit beide ‘n X draadvlak en ‘n U draadvlak. Die partikels 1,2,3H en 3,4He is almal geidentifiseer as uitgaande partikels van die botsing van 3He met 27Al. Kansvlak-berekeninge is uitgevoer vir alle waargenome reaksies. Diskrete spektra kon nie gevind word vir die (3He,6He) of (3He,8He) reaksies nie. Die massa berekening van A ∼ 20 kerne op die proton drup lyn is afhanklik van die bepaling van die Coulomb energie, wat baie verskil tussen spie¨elkerne. Massa berekeninge is uitgevoer vir bekende kerne in die massa gebied A ≤ 50, deur die gebruik van die Isobariese Multiplet Massa Vergelyking. Die ooreenstemming met eksperimentele data was baie beter in die geval van onewe kerne as met ewe kerne. Daarom was die massa voorspellings uitgevoer vir slegs onewe kerne naby die proton drup lyn.

Please refer to this item in SUNScholar by using the following persistent URL: http://hdl.handle.net/10019.1/4297
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