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

本项目设计并建造了一台小型电子束离子源(EBIS)，它与交叉束装置相连，用于测量碰撞能量为10 eV的多电荷离子电荷传输过程的微分截面。离子源由电子枪、漂移管、离子引取器和离子传输系统组成。设置在超高真空室外的螺线管线圈用于对电子束进行限制。例如，这种EBIS可以产生O^到O^&lt；5&gt；离子和Ar^到Ar^&lt；9&gt；离子；质量选择后的O^&lt；2&gt；或O^&lt；3&gt；束流的强度约为0.1nA，但经过能量选择和减速到10 eV区域后，只有很少的束流被传输到相互作用区。这种束流强度与通常用于低能多电荷离子-原子碰撞实验的反冲离子源获得的束流强度相同或略高。反冲离子源需要一个加速的重离子束作为泵浦束，而目前的装置对于小型实验室进行同类测量是非常方便的。作为第一次尝试，我在E&lt；cm&gt；=10 eV：O^&lt；2&gt；(^3P)He-&gt；O^(^2P)He^(^2S)5.52 eV处测量了在以下过程中产生的O^离子的角分布。虽然测量的角分布显示出一些结构，但由于传统的离子探测器只由孔和沟道电子倍增器组成，所以信号的统计不足以与理论结果相比较。为了提高检测效率，有必要使用位置灵敏探测器系统。因此，我已经开始设计一种使用微通道板的新型探测器系统。

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.