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In order to extend the dielectronic recombination (DR) experiments from the main cooler storage ring CSRm with intermediate charge state ions to the experimental cooler storage ring CSRe with highly charged ions and even radioactive ions, a test electron‐ion recombination experiment of B‐like Ar13+ ions was performed with a section of the new electron beam energy detuning system, which will be installed at the CSRe. We present the measured and also the calculated DR spectra for the ∆n = 0 resonances from 0 to 3 eV. The experimental results agree very well with the previous DR experimental data from CRYRING, and the energy resolution reached 30 meV full width at half maximum. This test experiment demonstrates that the reliability and stability of the newly developed electron beam energy detuning system are satisfactory for the upcoming DR experiments at the CSRe. However, we found large discrepancies between the experimental result and the calculation in both resonance positions and the intensities of the recombination spectrum below 0.7 eV, which indicate that precise calculation of the DR spectrum of multielectron ions is still a challenge. [ABSTRACT FROM AUTHOR]

Abstract: The longitudinal dynamics of RF-bunched and electron cooled ion beams have been studied at the experimental cooler storage ring (CSRe), at IMP Lanzhou. By RF-bunching the ion beam at the 50th and 100th harmonic of the revolution frequency, the longitudinal momentum spread and the bunch length of the 22Ne10+ ion beam with an energy of 70MeV/u were measured by the new resonant Schottky pick-up and the capacitive pick-up, respectively. A minimum momentum spread of has been reached with less than 107 ions stored in the ring. By using the harmonic potential extracted from the Taylor expansion and the real sinusoidal potential of the bucket, the trend of momentum spread and synchrotron frequency as well as the bunch length as a function of beam current can be interpreted very well. According to this experiment, the RF-buncher is suitable for upcoming experiments on laser cooling of relativistic heavy ion beams at the CSRe. [Copyright &y& Elsevier]

Abstract: An optical technique to study the longitudinal distribution of ions in a bunched ion beam circulating in a storage ring is presented. It is based on the arrival-time analysis of photons emitted after collisional excitation of residual gas molecules. The beam-induced fluorescence was investigated in the ultraviolet regime with a channeltron and in the visible region using a photomultiplier tube. Both were applied to investigate the longitudinal shape of bunched and electron-cooled 209Bi80+ ion beams at about 400MeV/u in the experimental storage ring (ESR) at GSI Helmholtzzentrum für Schwerionenforschung in Darmstadt, Germany. Bunch lengths were determined with an uncertainty of about 0.5m using the UV-sensitive channeltron and with slightly lower accuracy from the photomultiplier data due to the slower transitions in the red region of the spectrum. The Gaussian shape of the longitudinal distribution of ions inside the bunch was confirmed. With the information of the transverse beam size that can be measured simultaneously by a newly installed ionization profile monitor (IPM) at the ESR, an accurate determination of the ion density in the bunched beam will be allowed. [Copyright &y& Elsevier]

Abstract: A single-particle detector, which is designed to detect ions with energies of more than 2MeV/u, has been built and tested. The detector is operated based on the secondary-electron emission, which are produced by the incident ions impacting on a molybdenum foil with a thickness of about 5μm. The secondary electrons are deflected and focused onto two microchannel plates with chevron assembly. We simulated the trajectories of the secondary electrons in the electrostatic field and obtained the theoretical detection efficiency, which is greater than 90% and depends on electron yields and diameter of area of the electron emission. The detector was tested by an alpha radioactive source offline and by 86Kr26+ ions (25MeV/u) from accelerator. The detector can be used under the counting rate up to about 1×107 s−1, which satisfies the requirements of the dielectronic recombination experiment on storage ring CSRm. [Copyright &y& Elsevier]