PDF《2017》

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58 ・ IMP & HIRFL Annual Report

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2 Measurement of the Lifetime and the Proportion of C3+ Ions as a Preparation for Laser Cooling Experiments at the CSRe? Wang Hanbing, Wen Weiqiang, Huang Zhongkui, Zhang Dacheng, Hai Bang, Zhu Xiaolong, Zhao Dongmei, Li Jie, Li Xiaoni, Mao lijun, Mao Ruishi, Yang Jiancheng, Yuan Youjin, Ma Xinwen and Laser Cooling Collaboration Laser cooling is the most promising method to achieve high phase-space densities, even crystalline beams for relativistic heavy ion at storage rings[1] .

While a pure ion beam is usually desirable for laser cooling experiments to avoid spurious heating e?ects by any non-cooled ion species, we have found the C3+ ion beams produced by an Electron Cyclotron Resonance (ECR) ion source to be mixed with a signi?cant fraction of O4+ , because these two ions have almost the same mass-to-charge ratio and could not be separated by the analyzing magnets. Therefore, both ion species were injected into the CSRe and present during all experiments. An experiment was conducted in preparation of laser cooling experiments at the heavy-ion storage ring CSRe. The individual lifetimes of C3+ and O4+ ion beams were determined by a Schottky resonator. Using electron-cooling, the signals of the C3+ and O4+ ions could be separated and clearly observed in the Schottky spectrum as shown in Fig.

1 (a). Fig.

1 (b) shows the extracted lifetimes from the recorded Schottky spectrum of Fig.

1 (a) and the obtained individual lifetimes of the C3+ and O4+ components were 23.6 and 17.8, respectively. The proportion of C3+ ions in the stored ion beam was measured to be more than 70% at the beginning of the injection and increasing as a function of time. These measurements will be great helpful for further laser cooling and precision laser spectroscopy of C3+ ions at the heavy-ion cooler storage ring CSRe. Fig.

1 (color online) (a) Schottky spectrum of coasting C3+ and O4+ ion beams under electron cooling. The ions were successfully separated in the momentum phase space. The relative momentum di?erence between these species was calculated to be 7*10?5. (b) The individual lifetimes of C3+ and O4+ ion beams as determined from ?gure (a). The intensities of the Schottky spectrum have been converted into number of ions. (c) The proportion of C3+ ions in the stored ion beams extracted from ?gure (a). The proportion at the beginning of the injection is more than 70%, and it increases as a function of time. ? Foundation item: National Natural Science Foundation of China(11221064) and the External Cooperation Program of the CAS (GJHZ1305)

2017 IMP & HIRFL Annual Report ・

59 ・ Reference [1] U. Schramm, Crystalline ion beams, Progress in Particle and Nuclear Physics, 53(2004)583.

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3 Fully Di?erential Study of Few-body Dynamics in Multi-electron Atomic Fragmentation Processes Gao Yong, Ma Xinwen, Zhang Shaofeng, Zhu Xiaolong, Guo Dalong, Feng Wentian, Zhang Ruitian, Hai Bang, Zhang Min and Zhao Dongmei Fig.

1 (color online) Fully di?erential cross sections for two electrons, each with an energy of (10±5) eV, ejected into the scattering plane as a function of the polar ejection angles of both electrons. The transverse momentum transfer was ?xed at (5±1) a.u. The ar- rows show the direction and the opposite one of the momentum transfer vector. Employing the reaction microscope, the experiment of He2+ collisions on Ar was performed[1] . We have mea- sured fully momentum analyzed Ar3+ recoil ions and two ejected electrons as well as He+ projectiles in coin- cidence with each other. Fully di?erential cross sections (seeing Fig. 1) for electron transfer from the target to the projectile accompanied by the ejection of two ad- ditional target electrons were extracted. This is the ?rst measuring fully di?erential cross section on the ?ve- body process which supplies the most rigorous test for the relative theories[2] . To a large extent the data can be reproduced by an independent electron model. How- ever, we also observed a surprisingly strong correlation between the electron momenta and the projectile mo- mentum transfer. Up to now, it is not clear why the ejected electron momenta follow the momentum trans- fer so closely, and a ?nal explanation of the strong cor- relation probably also has to await the full quantum- mechanical treatment. References [1] X. Ma, Phys. Rev. A, 83(2011)052707. [2] Y. Gao, J. Phys. B: At. Mol. Opt. Phys., 50(2017)10LT01.