Kana Takahashi

Excited states in Si38,40,42 nuclei have been studied via in-beam γ-ray spectroscopy with multinucleon removal reactions. Intense radioactive beams of S40 and S44 provided at the new facility of the RIKEN Radioactive Isotope Beam Factory enabled γ-γ coincidence measurements. A prominent γ line observed with an energy of 742 keV in Si42 confirms the 2 + state reported in an earlier study. Among the γ lines observed in coincidence with the 2 +→0 + transition, the most probable candidate for the transition from the yrast 4 + state was identified, leading to a 41+ energy of 2173 keV. The energy ratio of 2.93 between the 21+ and 41+ states indicates well-developed deformation in Si42 at N=28 and Z=14. Also for Si38,40 energy ratios with values of 2.09 and 2.56 were obtained. Together with the ratio for Si42, the results show a rapid deformation development of Si isotopes from N=24 to N=28. © 2012 American Physical Society.

A 10 kHz pulsed X-ray generator utilising a hot-cathode triode in conjunction with a new type of grid control device for controlling X-ray duration is described. The energy-storage condenser was charged up to 70 kV by a power supply, and the electric charges in the condenser were discharged to the X-ray tube repetitively by the grid control device. The maximum values of the grid voltage, the tube voltage, and the tube current were −1.5 kV, 70 kV, and 0.4 A, respectively. The duration of the flash X-ray pulse was primarily determined by the time constant of the grid control device and the cut-off voltage of thermoelectrons. The X-ray duration was controlled within a region of less than 1 ms; the X-ray intensity with a pulse width of 0.27 ms, a charged voltage of 70 kV, and a peak tube current of 0.4 A was 0.92 μC kg −1 at 0.5 m per pulse. The maximum repetition rate was about 10 kHz, and the size of the focal spot was about 3.5×3.5 mm