E.A. Bakkum

The response of BGO scintillation detectors to light charged particles

Measurements of the response of BGO crystals to protons in the energy range from 6 to 13 MeV and to alpha particles in the range from 6 to 19 MeV are discussed. Results were obtained with a photomultiplier tube and a photodiode readout. A comparison is made with the response of a NaI(Tl) crystal to 13 MeV protons.

Light-particle detection with plastic scintillators coupled to a photodiode readout system

Abstract The response to alpha particles (between 13 and 20 MeV) and protons (between 3 and 12 MeV) of a large area photodiode coupled to plastic scintillators was measured with both charge- and current-sensitive preamplifiers. The results for the measurements with the charge-sensitive preamplifier are compared with data on other scintillators coupled to photodiode readout systems. These measurements were part of a study in which the possibility of constructing a light-particle detector consisting of a plastic phoswich scintillator and a photodiode was investigated.

A CCBA description of the (p, t) reaction to low-lying O+ states in the Ge isotopes

Differential cross sections for the (p, t) reaction to 0+ states in the even Ge isotopes have been measured at an incident energy (Ep = 13 MeV) where the triton energy is below the Coulomb barrier. The data are described by a coupled-channels calculation with wave functions consisting of neutron configurations only. Sequential transfer processes can explain the anomalies, which have led previously to the introduction of shape isomerism or proton excitations.

Four-nucleon transfer with the 32S(16O, 12C)36Ar reaction

Abstract Angular distributions have been measured for the 32 S( 16 O, 12 C) 36 Ar reaction at 45.5 MeV leading to excited states between E x , = 0 and 8 MeV. Experimental cross sections are compared with exact finite-range DWBA calculations in combination with extensive shell-model calculations, which include sd- and fp-shell configurations. Transitions to low-energy positive-parity states and bound negative-parity states are well reproduced. The calculations, however, fail to describe some high-energy positive-parity states. Calculations with a complete cluster expansion for the four transferred nucleons give about 50% larger cross sections, but can not explain the observed discrepancies. Possible interference of reaction processes other than direct α-transfer and special structure effects are discussed.

THE STRUCTURE OF 26Mg INVESTIGATED WITH THE (d, p) REACTION

Abstract Angular distributions have been measured for the 25 Mg(d, p) 26 Mg reaction at 13 MeV leading to excited states between E x = 0 and 8 MeV. Experimental cross sections are compared with DWBA calculations and extended shell-model calculations in the full sd shell. Spin and parity restrictions are obtained for several levels in the region E x = 6−;8 MeV. Spectroseopic factors for transitions to the lowest four positive-parity states of each spin are well reproduced by the shell-model calculations; however, in mixed configurations the largest component is systematically underestimated by the shell model. Only 60% of the strength for s 1 2 transfer is observed.

Excitation-energy sharing in20Ne induced reactions

Excitation-energy sharing has been studied in the20Ne+54Fe reaction at 11 and 15 MeV/nucleon using projectile-like fragment-α correlations. Since the dominant part of the correlation can be described by sequential decay, primary excitation distributions were obtained. An unexpected strong asymmetry in the excitation-energy sharing is observed.