Differential cross section measurements for charge-transfer reaction at 10eV region.

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A small electron-beam-ion-source (EBIS) was designed and constructed in this project, and is connected to the crossed-beam apparatus to measure differential cross sections for chargetransfer process involving multi-charged ions at the collision energy of 10 eV region.The ion-source consists of an electron-gun, drift-tubes, an ion-extractor and an ion-transporting system. A solenoid-coil which is set outside an ultra-high-vacuum chamber is used to confine the electron-beam. This EBIS could produce, for example, O^+ to O^<5+> ions and Ar^+ to Ar^<9+> ions ; the intensity of the O^<2+> or O^<3+> beam after mass-selection was about 0.1 nA,however, after energy selection and the deceleration down to 10 eV region, only a few percent of thebeam was transported to the interaction region. This beam-intensity is the same order or somewhat higher than that obtained by a recoil-ion-source used often for low-energy multicharged ion -atom collision experiments. Whereas the recoil-ion-source needs an accelerated heavy-ion-beam as a pump-beam, the present set-up is very convenient for a small laboratory for the same kind of measurements. An additional advantages of the present set-up is due to that almost all the ions are known to be in the ground states.As a first trial, I measured the angular distribution of O^+ ions produced in the following process at E_<cm>=10eV : O^<2+> (^3P) +He->O^+ (^2P) +He^+ (^2S) +5.52eV.Though the measured angular distribution shows some structure, the statistics of the signal was not enough to compare with theoretical results because a conventional ion-detector which consists of only apertures and a channel-electron-multiplier. To improve the detection efficiency, it is necessary to use a position-sensitive detector system. Therefore, I have started to design a new detector-system using a micro-channel-plate.