Abstract
Nuclear fission yields data measurements for thermal neutron induced fission of 241Pu have been carried out at the Institut Laue Langevin (ILL) in Grenoble, using the Lohengrin mass spectrometer. Mass, isotopic and isomeric yields have been extracted for the last measurements. A focus is given in this document to the mass yield results which are obtained for almost the entire heavy peak and most of the light high yields masses, along with the covariance matrix. The mean kinetic energy as a function of the fission product mass has also been extracted from the measurements. The total mean kinetic energy pre and post neutron emission have been assessed and compared to other works showing a rather good agreement.
Highlights
Nuclear fission yields data measurements for thermal neutron induced fission of 241Pu have been carried out at the Institut Laue Langevin (ILL) in Grenoble, using the Lohengrin mass spectrometer
Since a beam is selected with Lohengrin according to the mass A, the ionic charge q and the kinetic energy Ek of the fission product, one can measure with the ionization chamber the count rate N(A, Ek, q)
The mass yields for the entire heavy peak and a significant part of the light peak have been measured at Lohengrin and the experimental correlation matrix has been computed
Summary
The Lohengrin recoil mass spectrometer [7, 8] of which a descriptive figure is presented Fig. 1, has been built in the 70’s at the ILL and is since a major instrument for nuclear data measurements in particular due to its high mass resolution (∆A/A ∼ 1/400). The ion beam is selected according to the A/q and Ek/q ratios, where A is the fission product mass, Ek its kinetic energy and q its ionic charge. At position 1, the ion beam directly enters in an ionization chamber. This position is used to measure isobaric yields, Y(A). A double ionization chamber with a Frisch grid is used, giving access to a bidimentional map of the deposited energy as it can be seen Fig. 2. Two clovers of four high purity germanium crystals each and two broad energy germanium detectors are placed in the vicinity of the tape and detect γ-rays resulting from the fission products β− disintegration, allowing to measure isotopic yields Y(A, Z)
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