Abstract
An active fission target has been developed for the FIPPS instrument at ILL, enabling for the first time an efficient suppression of upbeta -delayed upgamma rays in high-resolution and high-efficiency upgamma -ray spectroscopy of fission fragments at a neutron beam. The target is based on a liquid scintillator in which the actinide is dissolved, resulting in a 4pi fragment detection. Measurements have been performed with ^{233, 235}U, with a fission tagging efficiency of 97.8(25)%. The high efficiency, together with the good time resolution of the scintillator target, provide high-selectivity data for upgamma -ray spectroscopy studies of fission fragments.
Highlights
Ion induced fission [7,8]
An active fission target has been developed for the Fission Product Prompt γ-ray Spectrometer (FIPPS) instrument at Institut Laue-Langevin (ILL), enabling for the first time an efficient suppression of β-delayed γ rays in high-resolution and high-efficiency γ-ray spectroscopy of fission fragments at a neutron beam
An efficient suppression of β-delayed γ rays from fission products has been possible for the first time by using a liquid scintillator based active fission target which was developed for the FIPPS spectrometer, located at the Institut Laue-Langevin (ILL) in Grenoble, France
Summary
The neutrons are produced by the institute’s high flux reactor and delivered as a strongly collimated beam to the target position, with a beam diameter of about 15 mm and a capture equivalent flux of up to 108 n/cm2/s. The main spectrometer consists of eight germanium clover detectors which form a closed octagon around the target, perpendicular to the neutron beam. In order to provide a fission tagging detector for FIPPS, which can be deployed in the neutron beam, an active target was developed based on an organic liquid scintillator. The actinide of interest is directly dissolved in the scintillator, allowing for a 4π fragment detection with high efficiency. This paper presents the design of the active target setup as well as the performance during the first fission campaigns, using 233U and 235U targets
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