Overview

SuN is a γ-Total Absorption Spectrometer. It is a cylindrical shape NaI(Tl) detector, 16-inch in diameter and 16-inch in height. It is segmented in eight optically separated segments, which are positioned above and below the beam axis as shown in the figures. Each segment is being read by three photomultiplier tubes (PMT) resulting in a total of 24 signals coming out of the detector. The signals from the PMTs are gain-matched using potentiometers located on the PMTs themselves as well as by appropriate high-voltage adjustment. The signals are then fed into the Digital Data Acquisition System (DDAS). SuN is used with auxiliary detectors depending on the type of experiment. A mini-DSSD implantation station was developed for fast-beam decay studies, while the SuNTAN tape transport system is typically used with low-energy beams to study longer-lived isotopes. Finally, an MCP detector and hydrogen gas cell are used for capture-reaction measurements at ReA3.

Technical detail

The efficiency of SuN for a cesium-137 source (Eγ = 661 keV) is 85 percent. For the summing of the two sequential γ-rays from the decay of Co-60 the sum-peak efficiency is 65 percent. The summing efficiency of SuN highly depends on the multiplicity of the γ-cascade being detected; the higher the multiplicity the lower the efficiency. The hit-pattern from the eight segments of SuN can be used to estimate the average multiplicity of a given sum peak. SuN has been simulated in Geometry And Tracking (GEANT4) and for a given γ-decay scheme the detection efficiency can be estimated using this simulation tool.

Funding acknowledgement: The construction of the SuN detector was funded by the NSF through the NSCL Cooperative Agreement PHY-1102511. The construction of SuNTAN was funded by NSF CAREER award PHY 1350234.