Application of the alpha transfer reactions at incident energies below the Coulomb barrier to determination of the astrophysical reaction rate

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The present study aims to develop a new experimental method of determining the astrophysical nuclear reaction rate by the measurement of the heavy-ion induced transfer reactions at incident energies below the Coulomb barrier with the recoil mass separator which has recently been developed at Kyushu University tandem accelerator laboratory. This separator is designed to achieve highest possible capability of the background rejection in the condition of inverse kinematics. Application of the proposed method to the deduction of the rate of the α-particle induced radiative capture reactions which cross sections are too small to measure directly at the accelerator facilities is expected to provide rich and new information on the evolution of the massive stars.Instrumental developments have been carried out at both the accelerator and the measuring devices for facilitating the observation of the reaction products emitted at center-of-mass angles of 0 and 180 degrees from the transfer reactions in the condition of the inverse kinematics with negligible contamination of the primary beam particles and the background particles associated with a primary beam. At the accelerator, the beam pulsing system and the windowless gas stripper have been developed to derive a pulsed beam of good emittance, essential to the elimination of the background. The detailed investigations on the performance of the mass separator and the response of a silicon semiconductor detector for low energy light-heavy particles have assured the background rejection capability of the measuring system enough to realize the unambiguous measurement. With these developments and investigations, we are about to start the experiments to examine the applicability of the transfer reaction data at low incident energies to the extraction of the astrophysical nuclear reaction rate.