Relativistic radioactive beams: A new access to nuclear-fission studies

Schmidt, Karl‐Heinz; Steinhäuser, S.; Böckstiegel, C.; Grewe, A.; Heinz, A.; Junghans, A. R.; Benlliure, J.; Clerc, H.‐G.; Jong, M. de; Müller, J.; Pfützner, M.; Voss, B.

doi:10.1016/s0375-9474(99)00384-x

Cited by 313 publications

(257 citation statements)

References 91 publications

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“…This process is non trivial given that no theoretical calculation of Y (A, Z, TKE) exists and no experiment provides complete measurement of this quantity. While phenomenological models have been developed [21], in the current implementation we often combine experimental information from several sources. Thus, data on fission fragment yields and TKE distribution from different experiments is usually supplemented by systematics [22].…”

Section: Model Overviewmentioning

confidence: 99%

“…This includes the initial excitation energy, initial spin and parity of each fragment. We simply assume that the parity distribution is equiprobable for positive and negative parities, but the problem of determining the partitioning of excitation energy sharing is more complicated and phenomenological models have been developed [4,21,[25][26][27]. Similarly, for the initial spin distribution we use a simple model [28].…”

Section: Model Overviewmentioning

confidence: 99%

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Properties of prompt-fissionγrays

et al. 2014

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In a Monte-Carlo Hauser-Feshbach statistical framework, we describe spectra, average multiplicities, average energy and multiplicity distributions of the prompt γ rays produced in the thermal neutron-induced fission of 235 U and 239 Pu, and the spontaneous fission of 252 Cf. Comparisons against recent experimental data show reasonable agreement in all cases investigated, after adjustment of the initial spin distribution in the fission fragments. In particular, when we include in the calculation the Doppler broadening we obtain a qualitatively good description of the measured low-energy spectra, where contributions from collective discrete transitions in specific fragments can be identified. At higher energies, both the calculated neutron and γ-ray spectra are softer than experimental data. The impact of selected model parameters on the prompt neutron and γ-ray spectra is analyzed. Finally, we present prompt γ spectrum and multiplicity distribution for the neutron-induced fission of 235 U for 5.5 MeV neutron incident energy, just below the threshold for second-chance fission.

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Section: Model Overviewmentioning

confidence: 99%

Section: Model Overviewmentioning

confidence: 99%

Properties of prompt-fissionγrays

et al. 2014

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“…In the pre-actinide region, predominantly symmetric FF mass distributions were measured. A few relevant cases for the present discussion (see also Fig.1) are 195 Au, 198 Hg and 208,210 Po, studied by means of charged-particle induced reactions [20][21][22] and 204,206,208 Rn studied via electromagnetically (EM)-induced fission [23,24]. In contrast to this, recent β-delayed fission experiments have established a new region of asymmetry around nuclei 178,180 Hg [25][26][27], which in fission divide into neutron-deficient fragments with most probable mass numbers around A L ∼ 80 and A H ∼ 100.…”

mentioning

confidence: 99%

“…These intriguing cases will be further studied at the RILIS [45] or CRIS [46,47] , with fission-fragment masses on the horizontal and their relative yields on the vertical axis, for even-N neutron-deficient isotopes between gold and radium at excitation energies slightly above the theoretical fission-barrier heights B f,th [33]. The calculated yields are compared with selected experimental MDs (red) from particle-induced [20,21], β-delayed ( [25,26], this work) and EM-induced fission [23,24]. The border of the lightest known isotopes is shown by the thick solid line, β-stable nuclei are shown on a gray background.…”

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confidence: 99%

Evolution of fission-fragment mass distributions in the neutron-deficient lead region

Ghys¹,

Andreyev²,

Huyse³

et al. 2014

Phys. Rev. C

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Low-energy β-delayed fission of 194,196 At and 200,202 Fr was studied in detail at the mass separator ISOLDE at CERN. The fission-fragment mass distributions of daughter nuclei 194,196 Po and 202 Rn indicate a triple-humped structure, marking the transition between asymmetric fission of 178,180 Hg and symmetric fission in the light Ra-Rn nuclei. Comparison with the macroscopic-microscopic finite-range liquid-drop model and the self-consistent approach employing the Gogny D1S energy density functional yields discrepancies. This demonstrates once more the need of dynamical fission calculations, as for both models the potential-energy surfaces lack pronounced structures, in contrast to the actinide region.Nuclear fission, the division of a heavy atomic nucleus into predominantly two parts, continues to provide new and unexpected features in spite of a long history of intensive theoretical and experimental studies [1][2][3][4][5][6][7]. The fission process is not only important for several applications, such as energy production and radiopharmacology, but also has a direct impact on the understanding of the fission recycling process in r -process nucleosynthesis [8,9]. Therefore, a description of the fission process with reliable predictive power is needed, in particular for low-energy fission where the fission-fragment (FF) mass distributions are strongly * lars.ghys@fys.kuleuven.be sensitive to microscopic effects [4]. Mass distributions (MDs) are usually predominantly symmetric or asymmetric with the yields exhibiting a single peak or two distinct peaks, respectively. However, in several cases a mixture of two modes was observed [5]. Experimental observables characterizing various fission modes are the width of the MD peak(s), the position of these peaks in asymmetric mass division and total kinetic energy (TKE) of the FFs. The dominance of asymmetric fission in most of the actinide region beyond A = 226 up to about 256 Fm was attributed to strong microscopic effects of the heavier FF, near the doubly-magic 132 Sn [4,10,11]. However, nuclei such as 258 Fm and 259,260 Md exhibit complex MDs, each with a narrow and a broad symmetric component with a higher and lower TKE, respectively. 2This phenomenon is called bimodal fission [12][13][14][15]. Competition between symmetric and asymmetric fission, corresponding to respectively lower and higher TKE and resulting in a triple-humped MD has been reported around 226 Th [16][17][18]. These observations strongly support the hypothesis that nuclei may fission through several independent fission modes corresponding to different pre-scission shapes and fission paths in a multidimensional potential-energy landscape, referred to in literature as multimodal or multichannel fission [4,5,11,[16][17][18][19]. In the pre-actinide region, predominantly symmetric FF mass distributions were measured. A few relevant cases for the present discussion (see also Fig.1) are 195 Au, 198 Hg and 208,210 Po, studied by means of charged-particle induced reactions [20][21][22] and 204,206,...

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“…Since the 90s, experimental efforts on inverse kinematics reactions fall in with this trend by providing extremely accurate yields data for various fissioning nuclei [1][2][3][4]. On the other side, building a predictive theory of fission applicable where no data is available remains a major challenge of nuclear physics.…”

Section: Introductionmentioning

confidence: 99%

Microscopic description of fission dynamics: Toward a 3D computation of the time dependent GCM equation

Regnier

Dubray

Schunck³

et al. 2017

EPJ Web Conf.

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Abstract. Accurate knowledge of fission fragment yields is an essential ingredient of numerous applications ranging from the formation of elements in the r-process to fuel cycle optimization in nuclear energy. The need for a predictive theory applicable where no data is available, together with the variety of potential applications, is an incentive to develop a fully microscopic approach to fission dynamics. One of the most promising theoretical frameworks is the time dependent generator coordinate method (TDGCM) applied under the Gaussian overlap approximation (GOA). However, the computational cost of this method makes it difficult to perform calculations with more than two collective degree of freedom. Meanwhile, it is well-known from both semi-phenomenological and fully microscopic approaches that at least four or five dimensions may play a role in the dynamics of fission. To overcome this limitation, we develop the code FELIX aiming to solve the TDGCM+GOA equation for an arbitrary number of collective variables. In this talk, we report the recent progress toward this enriched description of fission dynamics. We will briefly present the numerical methods adopted as well as the status of the latest version of FELIX. Finally, we will discuss fragments yields obtained within this approach for the low energy fission of major actinides.

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Relativistic radioactive beams: A new access to nuclear-fission studies

Cited by 313 publications

References 91 publications

Properties of prompt-fissionγrays

Properties of prompt-fissionγrays

Evolution of fission-fragment mass distributions in the neutron-deficient lead region

Microscopic description of fission dynamics: Toward a 3D computation of the time dependent GCM equation

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