ABSTRACT
The Total Energy Suppression Shield Array (TESSA) has been operating on the 20 MV Tandem at the Daresbury Laboratory since the beginning of 1983. The suppression shields used in TESSA are 25 cm diameter by 20 cm long cylindrical NaI crystals with the germanium detector inserted parallel to the crystal axis such that γ-rays strike the curved surface of the germanium. TESSA has been used extensively at Daresbury in the past eighteen months to study discrete γ-ray lines in nuclei around mass 80, around mass 130 and in many nuclei in the rare earth region. TESSA has the attributes required for continuum γ-ray spectroscopy; high resolution, excellent peak to total fractions, good channel selection and reasonable statistics. TESSA has been used to study the angular momentum distributions which are present in the fusion of several heavy ions close to the Coulomb barrier.
