A system to measure isomeric state half-lives in the 10 ns to 10 μs range

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Toufen D.L.
Allegro P.R.P.
Medina N.H.
Oliveira J.R.B.
Cybulska E.W.
Seale W.A.
Linares R.
Silveira M.A.G.
Ribas R.V.
Review of Scientific Instruments
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Toufen, D.L.; ALLEGRO, P.R.P.; Medina, N.H.; Oliveira, J.R.B.; Ribas, R V; Cybulska, E W; Seale, W A; LINARES, R.; SILVEIRA, M. A. G.. A system to measure isomeric states half-lives in the 10 ns to 10 μs range. Review of Scientific Instruments, v. 85, n. 7, p. 073501, 2014.
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The Isomeric State Measurement System (SISMEI) was developed to search for isomeric nuclear states produced by fusion-evaporation reactions. The SISMEI consists of 10 plastic phoswich telescopes, two lead shields, one NaI(Tl) scintillation detector, two Compton suppressed HPGe γ-ray detectors, and a cone with a recoil product catcher. The new system was tested at the 8 UD Pelletron tandem accelerator of the University of São Paulo with the measurement of two known isomeric states: 54Fe, 10+ state (E = 6527.1 (11) keV, T1/2 = 364(7) ns) and the 5/2+ state of 19F (E = 197.143 (4) keV, T1/2 = 89.3 (10) ns). The results indicate that the system is capable of identifying delayed transitions, of measuring isomeric state lifetimes, and of identifying the feeding transitions of the isomeric state through the delayed γ-γ coincidence method. The measured half-life for the 10+ state was T1/2 = 365(14) ns and for the 5/2+ state, 100(36) ns. © 2014 AIP Publishing LLC.