Recoil distance method lifetime measurements at TRIUMF-ISAC using the TIGRESS Integrated Plunger

• Published in: Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment Vol. 882; pp. 69 - 83
• Main Authors: Chester, A., Ball, G.C., Bernier, N., Cross, D.S., Domingo, T., Drake, T.E., Evitts, L.J., Garcia, F.H., Garnsworthy, A.B., Hackman, G., Hallam, S., Henderson, J., Henderson, R., Krücken, R., MacConnachie, E., Moukaddam, M., Padilla-Rodal, E., Paetkau, O., Pore, J.L., Rizwan, U., Ruotsalainen, P., Shoults, J., Smallcombe, J., Smith, J.K., Starosta, K., Svensson, C.E., Van Wieren, K., Williams, J., Williams, M.
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 21-02-2018
• Subjects: Coulomb excitation; CsI(Tl) pulse shape analysis; Doppler-shift lifetime methods; Gamma-ray spectroscopy; Monte Carlo analysis; Gamma-ray spectroscopy; Monte Carlo analysis; Coulomb excitation; Doppler-shift lifetime methods; CsI(Tl) pulse shape analysis
• ISSN: 0168-9002; 1872-9576
• DOI: 10.1016/j.nima.2017.11.029

The TIGRESS Integrated Plunger device (TIP) has been developed for recoil distance method (RDM) lifetime measurements using the TIGRESS array of HPGe γ-ray detectors at TRIUMF’s ISAC-II facility. A commissioning experiment was conducted utilizing a 250 MeV  84Kr beam at ≈2×108 particles per second. The 84Kr beam was Coulomb excited to the 21+ state on a movable  27Al target. A thin Cu foil fixed downstream from the target was used as a degrader. Excited nuclei emerged from the target and decayed by γ-ray emission at a distance determined by their velocity and the lifetime of the 21+ state. The ratio of decays which occur between the target and degrader to those occurring after traversing the degrader changes as a function of the target–degrader separation distance. Gamma-ray spectra at 13 target–degrader separation distances were measured and compared to simulated lineshapes to extract the lifetime. The result of τ=5.541±0.013(stat.)±0.063(sys.) ps is shorter than the literature value of 5.84±0.18 ps with a reduction in uncertainty by a factor of approximately two. The TIP plunger device, experimental technique, analysis tools, and result are discussed.