Study of Giant Monopole Resonance in Unstable Nuclei via Proton Inelastic Scattering at Zero Degrees

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We have developed new experimental technique to study Giant Monopole Resonances in exotic nuclei via proton inelastic scattering at zero degrees utilizing inverse kinematics. In this method, low-energy protons emitted at zero degrees are detected by the Si strip focal plane detectors in the 180-degree-bend-type magnetic spectrometer. Total kinetic energy and the time of flight of protons are measured to get the the excitation energy of the nucleus and the scattering angle of protons. After constructing window-frame-type magnetic dipole magnet, development and construction of the Si-strip focal plane detectors, development of high-resolution TOF measurements, energy resolution of less than 10keV (rms) and TOF resolution of less than 1 nsec (rms) were obtained for 0-4 MeV protons. Test experiments were performed at RIKEN accelerator facility. using primary heavy ion beams (^<12>C and^<40>Ar) and neutron-rich secondary beams (^<38>S) at around 60 MeV/A. Through these tests, we have succeeded to reduce physical backgrounds down to negligible level under the actual experimental conditions. Finally we have performed zero-degree proton inelastic scattering measurements from p(^<38>S,p') reaction, and succeeded to observe L=0 and L=1 type excitations. Although backgrounds from C component in CH2 target need to be reduced, we have succeeded to establish proposed new, experimental technique.