The fission Time Projection Chamber (fissionTPC) is a compact (15 cm diameter) two-chamber MICROMEGAS TPC designed to make precision cross section measurements of neutron-induced fission. The actinide targets are placed on the central cathode and irradiated with a neutron beam that passes axially through the TPC inducing fission in the target. The 4π acceptance for fission fragments and complete charged particle track reconstruction are powerful features of the fissionTPC which will be used to measure fission cross sections and examine the associated systematic errors. This paper provides a detailed description of the design requirements, the design solutions, and the initial performance of the fissionTPC.

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We have measured the capture-fission excitation functions for the reaction of stable 39 K and radioactive 46 K with 181 Ta using the ReA3 facility at the NSCL. In addition the capture-fission excitation function for the 39 K + 181 Ta reaction was measured at ANU. The capture cross sections for the 46 K + 181 Ta reaction are larger than those for the 39 K induced reactions in the near barrier region although the reduced excitation functions for the two reactions do not indicate any fundamental differences between the reactions. The results of the measurements are compared to modern phenomenological models and microscopic TDHF calculations. The implications of these measurements for the synthesis of heavy nuclei at radioactive beam facilities are discussed.