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HK: Fachverband Hadronen und Kerne

HK 67: Poster Session

HK 67.40: Poster

Thursday, March 19, 2009, 14:00–16:00, Audi-Max

Optimization of the recoil-shadow projection method for the investigation of short-lived fission isomers* — •M. Helmecke, P.G. Thirolf, D. Habs, E. Gartzke, V. Kolhinen, C. Lang, J. Szerypo, and L. Trepl — Fakultät f. Physik, LMU München, Germany and Maier-Leibnitz Laboratory, Garching, Germany

Spectroscopic studies of super- and hyperdeformed actinide nuclei offer the possibility to gain insight into the multiple-humped fission barrier landscape. With the identification of deep third minima in ²³⁴U and ²³⁶U the systematics of fission isomers in light actinides was revisited, especially searching for isomers in light uranium isotopes with half-lives in the pico-second range. Using the recoil-shadow projection method [1] and solid state nuclear track detectors, an experimental search for their observation has been started. This well-established detection technique nowadays benefits from an efficient analysis technology based on a PC-controlled auto-focus microscope and a CCD camera together with pattern recognition software. The flatness and the definition of the shadow edge of the target is the critical point of this method: Due to the energy loss of the beam the target carrier foil (1µm Ni) may develop thermal distortions in the µm range, leading to misinterpretations of isomeric fission fragments. Therefore the flatness of the target foil is continuously monitored via a capacitance measurement. First results applying this method to the search of a fission isomer in ²³⁴U via the ²³²Th(α,2n) reaction will be presented.

[1] Metag et al., Nucl. Instr. Meth. 114 (1974) 445.

*supported by DFG Cluster of Excellence UNIVERSE