J. J. van Zyl

Characterization of the proposed 4-α cluster state candidate in O 16

CITATION: Li, K. C. W., et al. 2017. Characterization of the proposed 4−α cluster state candidate in ¹⁶O. Physical Review C, 95(3):1-6, doi:10.1103/PhysRevC.95.031302.

Analyzing power distribution in the 12C(p, pα)8Be(g.s.) reaction at an incident energy of 100 MeV

The analyzing power distribution in the 12C(p,pα)8Be(g.s.) reaction at an incident energy of 100 MeV is investigated. The experimental coincidence data measured under quasifree kinematic conditions are in remarkable agreement with the trend of free p+4He elastic scattering, and also with a distorted-wave impulse approximation prediction. Thus the projectiles interact with the clusters as if they were free entities, with the rest of the target nucleons acting merely as spectators to the reaction. This result provides compelling and direct evidence for the existence of preformed α-clusters in 12C, as has often been postulated for this nucleus.

Re-examining the Mg26(α,α′)Mg26 reaction: Probing astrophysically important states in Mg26

P. Adsley, 2, 3, ∗ J.W. Brümmer, K.C.W. Li, D.J. Maŕın-Lámbarri, 4, 5 N.Y. Kheswa, L.M. Donaldson, 6 R. Neveling, P. Papka, 2 L. Pellegri, 6 V. Pesudo, 4 L.C. Pool, F.D. Smit, and J.J. van Zyl Department of Physics, Stellenbosch University, Private Bag X1, 7602 Matieland, Stellenbosch, South Africa iThemba Laboratory for Accelerator Based Sciences, Somerset West 7129, South Africa Institut de Physique Nucléaire d’Orsay, UMR8608, CNRS-IN2P3, Université Paris Sud 11, 91406 Orsay, France Department of Physics, University of the Western Cape, P/B X17, Bellville 7535, South Africa Instituto de F́ısica, Universidad Nacional Autónoma de México, Apdo. Postal 20-364, 01000 Cd. México, Mexico School of Physics, University of the Witwatersrand, Johannesburg 2050, South Africa (Dated: October 24, 2017)

α Clustering in Si 28 probed through the identification of high-lying 0+ states

CITATION: Adsley, P., et al. 2017. α clustering in ²⁸Si probed through the identification of high-lying 0⁺ states. Physical Review C, 95(2):1-8, doi:10.1103/PhysRevC.95.024319.

A high energy-resolution zero degree facility for (p,p′) and (p,t) reactions

Medium-energy hadronic scattering and reactions at zero degrees are very selective to excitations with low angular momentum transfer. Only a few facilities exist worldwide where high energy-resolution measurements of this nature can be performed. The K600 Zero-Degree Facility at iThemba LABS, South Africa, was recently successfully developed. Measurements were performed for inelastic proton scattering at an incident energy of 200 MeV for targets ranging from 27Al to 208Pb. Excitation energy-resolution of 50 keV (FWHM) was achieved. A reasonable background subtraction procedure allows for the extraction of excitation energy spectra with low background. Measurements of the (p,t) reaction at 100 MeV benefit from a large difference in magnetic rigidity between the reaction products and primary particles, resulting in almost background-free spectra with excitation energy-resolution of 32 keV (FWHM).

Incident‐Energy Dependent Quenching of the Analyzing Power in Pre‐Equilibrium Composite Particle Emission

The proton‐induced pre‐equilibrium process in the energy range of 100 to 160 MeV, which leads to emission of composite ejectiles such as 3He and α‐particles, is discussed. New cross section and analyzing power measurements for the (p,3He) reaction on 93Nb at an incident energy of 160 MeV are presented, and these are found to be in agreement with the prediction of a statistical multistep theoretical formulation. The observed quenching of the analyzing power is also reproduced well by the theory. The results are consistent with earlier work at lower incident energies and other nuclear species.

Factorization of the Cross Section for the 12C(p,pα)8Be(g.s.) Reaction at an Incident Energy of 100 MeV

Cross sections and analyzing powers for the reaction 12C(p,pα)8Be at an incident energy of 100 MeV, measured over a range of quasifree scattering angle pairs, are compared with elastic scattering of protons from 4He. Remarkable agreement between angular distributions of the two sets of data, presented as a function of the scattering angle in the two‐body centre‐of mass, is found. Thus the α‐cluster reacts to the projectile just like a free particle.

Multistep direct mechanism in the (p-vector,{sup 3}He) inclusive reaction on {sup 59}Co and {sup 93}Nb at incident energies between 100 and 160 MeV

Emission-energy distributions for cross sections as well as analyzing powers were investigated for (p-vector,{sup 3}He) reactions on {sup 59}Co and {sup 93}Nb to the continuum from a threshold of {approx}40 MeV up to the kinematic limit at incident energies of 130 and 160 MeV. A range of scattering angles from 15 degree sign to 140 deg. (laboratory) was explored. The experimental distributions were compared with a multistep direct theory in which a reaction mechanism based on deuteron pickup is employed. Reasonable agreement between experimental double differential cross sections and analyzing powers and the theoretical expectation was obtained. This work, together with published results for the same reaction and targets at a lower projectile energy of 100 MeV, allowed the incident-energy dependence of the cross section and analyzing power distributions to be explored.

Reaction Cross Sections for Protons on 12C, 40Ca, 90Zr, and 208Pb at Energies between 80 and 180 MeV

Results of reaction cross‐section measurements on 12C, 40Ca, 90Zr, and 208Pb at incident proton energies between 80 and 180 MeV are presented. The experimental procedure is described and the results are compared with earlier measurements and predictions using macroscopic and microscopic models.

The USE of a pulsatile bloodless perfusion system in organ preservation

Summary A method for isolated bloodless perfusion of primate (baboon) kidneys is described. Kidneys were perfused using oxygen or helium gas and the results were compared. Improved renal cortical circulation with increase in the extractions of PAH and creatinine and filtration fractions was shown to be secondary to a generalized renal vasodilation associated with helium exposure. In both gas systems, renal autoregulation was present. A relative renal cortical vasoconstriction, as shown by similar measurements, was noted in the oxygen-treated kidneys. Salt and water concentration was maintained in helium-exposed kidneys despite little or no renal oxygen consumption, demonstrating that the isolated bloodless perfused kidney obtained adequate metabolic substrate from intrinsic or extrinsic stores provided in the perfusion system. Urinary enzymatic concentrations were normal with both gases and correlated with observed renal morphological microscopic status. These and other observations on PAH transport and kinetics confirm that with the present perfusion system helium gas may be employed with benefit to the renal cortical circulation metabolism and ultimately may benefit preservation and storage of organs.