"High resolution study of fission resonance structure in 233Th"
Margit Csatlós, MTA ATOMKI, Debrecen, Hungary
(id #73)
Seminar: NoPoster: Yes
Invited talk: No
From detailed study of the hyperdeformed states in 234,236U isotopes, we obtained new insight into the fission barrier landscape in the actinide region. We observed numerous hyperdeformed rotational bands in 234,236U isotopes [1,2] and from the density of the states considerably deeper third minima were deduced than predicted earlier, and these new values are in good agreement with the latest theoretical predictions [3]. In a high resolution experiment Blons et al. identified for the first time rotational bands in the 232Th(n,f) reaction [4] and suggested a very shallow third minimum contrary to our experimental findings for uranium isotopes. Moreover, it was also shown that using a triple humped potential barrier with a shallow third minimum and broad transitional states the energy dependence of the cross section can be described [5].
In order to determine the depth of the third minimum also in 233Th we remeasured the fission probability and the angular distribution of the fission fragments in a wider excitation energy range and with better resolution compared to the study of Blons et al. The 232Th(d,pf) experiment was performed at the Tandem accelerator of the Maier-Leibnitz Laboratory at Garching with a deuteron beam of E=14 MeV. The energy of the protons was measured with a high resolution Q3D magnetic spectrograph in coincidence with the fission fragments. The position sensitive avalanche fission detectors supplied also precise angular distribution data. The energy and angular resolutions were 6 keV and ≤ 5o respectively, during the experiment.
We have observed new resonances in the covered excitation energy region. The avarege energy difference of the observed resonances is comparable to the ones observed previously for 234U [1] and 235U [2], suggesting much deeper third minimum than the one assumed by Blons earlier.
References:
[1] A. Krasznahorkay et al., Phys. Rev. Lett. 80(1998) 2073; Phys. Lett. B461 (1999) 15.
[2] M. Csatlós et al., Phys. Lett.. B615 (2005) 175.
[3] S. Ćwiok et al., Phys. Lett. B322 (1994) 304.
[4] J. Blons et al., Phys. Rev. Lett. 35(1975) 1749.; Nucl. Phys. A477 (1988) 231.
[5] M. Sin et al., Phys. Rev. C74(2006) 014608.
In order to determine the depth of the third minimum also in 233Th we remeasured the fission probability and the angular distribution of the fission fragments in a wider excitation energy range and with better resolution compared to the study of Blons et al. The 232Th(d,pf) experiment was performed at the Tandem accelerator of the Maier-Leibnitz Laboratory at Garching with a deuteron beam of E=14 MeV. The energy of the protons was measured with a high resolution Q3D magnetic spectrograph in coincidence with the fission fragments. The position sensitive avalanche fission detectors supplied also precise angular distribution data. The energy and angular resolutions were 6 keV and ≤ 5o respectively, during the experiment.
We have observed new resonances in the covered excitation energy region. The avarege energy difference of the observed resonances is comparable to the ones observed previously for 234U [1] and 235U [2], suggesting much deeper third minimum than the one assumed by Blons earlier.
References:
[1] A. Krasznahorkay et al., Phys. Rev. Lett. 80(1998) 2073; Phys. Lett. B461 (1999) 15.
[2] M. Csatlós et al., Phys. Lett.. B615 (2005) 175.
[3] S. Ćwiok et al., Phys. Lett. B322 (1994) 304.
[4] J. Blons et al., Phys. Rev. Lett. 35(1975) 1749.; Nucl. Phys. A477 (1988) 231.
[5] M. Sin et al., Phys. Rev. C74(2006) 014608.
