APS : Direct Determination of Fission-Barrier Heights Using Light-Ion Transfer in Inverse Kinematics

Bennett, S.A.; Freeman, S.J.; Ayyad, Y.; Tang, T.L.; Hoffman, C.R.; Smith, A.G.; Gaffney, L.P.; Sharp, D.K.; Heinz, A.; Chen, J.; Dolan, A.; Kay, B.P.; Tolstukhin, I.A.; Page, R.D.; Wright, T.J.; Müller-Gatermann, C.; Davies, P.J.; Garrett, K.; Wilson, G.L.

doi:10.1103/PhysRevLett.130.202501

Article
Report number	arXiv:2304.10281
Title	Direct Determination of Fission-Barrier Heights Using Light-Ion Transfer in Inverse Kinematics
Author(s)	Bennett, S.A. (Manchester U.) ; Garrett, K. (Manchester U.) ; Sharp, D.K. (Manchester U.) ; Freeman, S.J. (Manchester U. ; CERN) ; Smith, A.G. (Manchester U.) ; Wright, T.J. (Manchester U.) ; Kay, B.P. (Argonne, PHY) ; Tang, T.L. (Argonne, PHY) ; Tolstukhin, I.A. (Argonne, PHY) ; Ayyad, Y. (Santiago de Compostela U., IGFAE) ; Chen, J. (Argonne, PHY) ; Davies, P.J. (York U., England) ; Dolan, A. (Liverpool U.) ; Gaffney, L.P. (Liverpool U.) ; Heinz, A. (Chalmers U. Tech.) ; Hoffman, C.R. (Argonne, PHY) ; Müller-Gatermann, C. (Argonne, PHY) ; Page, R.D. (Liverpool U.) ; Wilson, G.L. (Louisiana State U. ; Argonne, PHY)
Publication	2023-05-19
Imprint	2023-04-20
Number of pages	6
In:	Phys. Rev. Lett. 130 (2023) 202501
DOI	10.1103/PhysRevLett.130.202501 (publication)
Subject category	nucl-ex ; Nuclear Physics - Experiment
Abstract	We demonstrate a new technique for obtaining fission data for nuclei away from $\beta$-stability. These types of data are pertinent to the astrophysical \textit{r-}process, crucial to a complete understanding of the origin of the heavy elements, and for developing a predictive model of fission. These data are also important considerations for terrestrial applications related to power generation and safeguarding. Experimentally, such data are scarce due to the difficulties in producing the actinide targets of interest. The solenoidal-spectrometer technique, commonly used to study nucleon-transfer reactions in inverse kinematics, has been applied to the case of transfer-induced fission as a means to deduce the fission-barrier height, among other variables. The fission-barrier height of $^{239}$U has been determined via the $^{238}$U($d$,$pf$) reaction in inverse kinematics, the results of which are consistent with existing neutron-induced fission data indicating the validity of the technique.
Copyright/License	preprint: (License: arXiv nonexclusive-distrib 1.0) publication: © 2023-2024 authors (License: CC BY 4.0)

$To-scale schematic of the experimental setup with example particle trajectories for $^{238}$U($d$,$pf$) events. Example proton trajectories for reactions populating the ground state in $^{239}$U (orange curves) and states at 7~MeV close to the fission barrier (purple curves) are shown for a range of c.m. proton angles. Example fission fragment trajectories are also shown for fragments with $A = 138$ (red curves) and $A=100$ (blue curves), for a range of emission angles. The equally spaced circular detector apertures have radius 8~cm, and are centered 18~cm from the beam axis. The axial distance between the target and detector apertures is 70~cm.$ $(a)~Excitation-energy spectra associated with all events for Si array data taken with both CD$_2$ and C targets where the C data has been scaled onto the CD$_2$ data, and for the carbon subtracted CD$_2$ data. (b)~Same as for (a), but for events in which $\geq 1$ fission fragments are detected with the MWPCs of the fission array. The vertical solid line denotes the known fission-barrier height \cite{bjornholm1980double}. The carbon target spectra were scaled by $\times$1.92 and $\times$1.76 for the singles and fission-gated data, respectively.$ $(a)~Experimental fission probability, as defined in Equation~\ref{eqn:pf} compared to a GEF simulation~\cite{schmidt2016general} (the GEF result has been normalized to our data) and empirical Hill-Wheeler fit with $\chi^2_{\mathrm{red.}} = 0.57$. The vertical line denotes the known fission-barrier height. (b)~Experimental fission probability in the region around the fission barrier compared to probabilities deduced from evaluated nuclear data libraries (JEFF-3.3~\cite{plompen2020joint}, ENDF/B-VIII.0~\cite{brown2018endf}, JENDL-4.0~\cite{shibata2011jendl}). In the bottom panel, the experimental data have been increased by 30\% as explained in the main text. The error bars represent the statistical uncertainty.$ Show more plots

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Record created 2023-05-25, last modified 2024-09-27

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