Background: The cross section for forming a heavy evaporation residue in fusion reactions depends on the capture cross section, the fusion probability, P CN , i.e., the probability that the projectile-target system will evolve inside the fission saddle point to form a completely fused system rather than re-separating (quasifission), and the survival of the completely fused system against fission. P CN is the least known of these quantities. Methods: We measured the fission fragment angular distributions for these reactions and used the formalism of Back to deduce the fusion-fission and quasifission cross sections. From these quantities we deduced P CN for each reaction. Conclusions:The new measured values of P CN agree roughly with the semi-empirical systematic dependence of P CN upon fissility for excited nuclei.

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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