Towards²⁶Na via (d,p) with SHARC and TIGRESS and a novel zero-degree detector

Abstract

Abstract. Nucleon transfer experiments have in recent years begun to be exploited in the study of nuclei far from stability, using radioactive beams in inverse kinematics. New techniques are still being developed in order to perform these experiments. The present experiment is designed to study the odd-odd nucleus 26 Na which has a high density of states and therefore requires gamma-ray detection to distinguish between them. The experiment employed an intense beam of up to 3 × 10 7 pps of 25 Na at 5.0 MeV/nucleon from the isac-ii facility at triumf. The new silicon array sharc was used for the first time and was coupled to the segmented clover gamma-ray array tigress. A novel thin plastic scintillator detector was employed at zero degrees to identify and reject reactions occurring on the carbon component of the (CD)2 target. The efficiency of the background rejection using this detector is described with respect to the proton and gamma-ray spectra from the (d,p) reaction.

Shell evolution approaching the N= 20 island of inversion: Structure of 26Na

“…Notably, the 1p 3/2 neutron configuration was found to play an enhanced role in the structure of the low-lying negative parity states in 26 Na, compared to the isotone 28 Al. Thus, the lowering of the 1p 3/2 orbital relative to the 0f 7/2 occuring in the neighbouring Z=10 and 12 nuclei - 25,27 Ne and 27,29 Mg -is seen also to occur at Z=11 and further strengthens the constraints on the modelling of the transition into the island of inversion.…”

“…In order to identify events in SHARC arising from fusion-evaporation reactions initiated on the carbon in the target (a source of significant background), an Al foil followed by a thin plastic scintillator detector (the TRIFOIL [26]) were installed 400 mm downstream of the target. The Al thickness of 30 µm was chosen to stop fusion-evaporation residues whilst transmitting the beam and the products of direct reactions [27]. Further, the scintillator foil was thin enough (10 µm) to transmit the radioactive beam.…”

Investigating Single-Particle Structure in 26Na Using the New SHARC Array

“…The γ rays from the de-excitation of 26 Na were positively identified with reasonable efficiency, with approximately 60% being tagged. The TRIFOIL also reduced the smooth background of charged particles underlying the protons, reducing it by 90%, but also only 80% of the ejected protons were tagged [16].…”

What Can We Learn from Transfer, and How Is Best to Do It?

“…Note that, in the longer term, the purpose-built fragment mass separator EMMA [76] will become available at TRIUMF. In the meantime, a detector developed at LPC Caen and called the trifoil was adapted [77] from its original purpose, which was to provide a timing signal for secondary beams produced via projectile fragmentation at intermediate energies. The experimental layout for the first experiment [70] using the trifoil in this fashion is shown in Figure 23.…”

“…A plastic scintillator detector was introduced at zero degrees, 400 mm beyond the target, to help in identifying and eliminating events arising from reactions on the carbon component of the CD 2 target. The performance of this trifoil detector [77] is discussed in the text.…”