D. M. Zhao

Surface nanostructure formation by the interaction of slow xenon ions on HOPG surfaces

Experiments on nanostructure formation on highly oriented pyrolytic graphite (HOPG) surfaces irradiated by slow highly charged Xeq+ (q = 23-29) ions have been carried out at a new experimental terminal for surface physics on the 320 kV ECR platform at the Institute of Modern Physics (IMP). In the tapping mode atomic force microscope (AFM) image, the nano-sized hillocks protruding from the surfaces are probed. The height and diameter of the nanostructures increase with the projectile charge state. The present results reveal a similarity between the nanostructure formation produced by slow highly charged ions and the track formation induced by swift heavy ions.

RF-bunching of relativistic 12C3+ ion beam for laser cooling experiment at the CSRe

To prepare the upcoming experiment of laser cooling of relativistic 12C3+ ion beams at the experimental cooler storage ring (CSRe), a test experiment was performed with 12C3+ ion beams at an energy of 122 MeV/u on the CSRe, at the Institute of Modern Physics, Lanzhou, China. In this experiment, the main storage ring of CSRm was employed to accumulate and accelerate the ion beam which was injected into the CSRe for the experiments. The number of 12C3+ ions at the CSRe reached 5×108 for every injection, which satisfied the experimental requirement. To fulfil the laser cooling experiment, the 12C3+ ion beams were bunched by sinusoidal waveforms with fixed and sweeping frequencies, respectively. A resonant Schottky pick-up was employed to record the Schottky spectra of these ion beams. The test experimental results demonstrated that the RF-buncher and diagnostic systems at the CSRe worked well and the CSRe was very stable with 12C3+ ion beams, hereby the CSRe is suitable for laser cooling experiment.

Development of X‐Ray Mirror Shaped by Mechanical Bending at NSRL

A toroidally bent cylindrical mirror system has been developed for the 4.1–12.4 keV region at NSRL. The design of the bending mechanism of a quasi four‐bar bender with compensation of gravity by a method of balance is described in detail as well as its support architecture which is desirable that all degrees of freedom are independently adjustable with a minimum of cross‐coupling between adjustments. Simulation on the performance of bending by FEM (Finite Element Method) and measurement results by LTP (Long Trace Profiler) are presented. The thermal effects on optical surface and some ongoing improvement of this system are also discussed briefly.

Investigation of fragmentation dynamics of nitrogen dimers by collisions with highly charged ions

Synopsis The fragmentation dynamics of nitrogen molecule dimers have been studied by using highly charged Ne8+ ions at impact energy of 1.0 MeV. For its three-body fragmentation, three fragmentation mechanisms have been identified by analyzing Dalitz plot and Newton diagram of the momenta of three fragment ions. The sequential dissociation of covalent first breakdown is quite surprising in contrast to the fragmentation of triatomic molecule.

Dielectronic recombination of Be-like argon at the CSRm

Electron-ion recombination of Be-like 40Ar14+ has been measured for the first time at the main Cooler Storage Ring (CSRm) at Heavy Ion Research Facility in Lanzhou (HIRFL), China. The absolute rate coefficients over 0-60 eV electron-ion energy were obtained and all the resonances associated with the Δn=0 dielectronic recombination channel (2s2→2s2p) were studied. In addition to radiative and dielectronic recombination, the recombination spectrum also shows strong contributions from trielectronic recombination channel (2s2→2p2). The experimental method and preliminary results are presented.

Kinematically complete experiment for ionization-excitation of helium

We present a newly built reaction microscope for electron induced ionization-excitation of helium. Kinematically complete measurement with 2p state excitation is achieved by detecting the radiated photon, one electron and the He+ ion in the final state in triple coincidence. Near threshold behavior of the ionization- excitation to 2p state is investigated.

Progress of laser cooling of 12C3+ ions at the CSRe

We have performed a test run for laser cooling experiments with 12C3+ ion beams at an energy of 122 MeV/u at the CSRe with a pulsed laser. During this beamtime a lot of progress have been made. This was the first time we could successfully separate the 12C3+ ions and 16O4+ ions in the Schottky spectrum with the help of electron cooling. And our newly installed CPM detector worked well during the experiment. We tried to see effects from the interaction of the pulsed laser light with the stored 12C3+ ion beams, but no cooling effects could yet be observed.

The fragmentation of neon dimer induced by low energy O6+ ions

We have investigated the fragmentation channels Ne+-Ne+ and Ne2+-Ne+ from Ne2 dimer induced by O6+ ions at impact energy of 15 keV/u. The Ne+-Ne+ fragmentation channel mainly results from three pathways: the interatomic coulombic decay of Ne2+(2p4)-Ne initial state, the direct columbic explosion and the radiation charge transfer. Nevertheless, the fragmentation channel Ne2+-Ne+ is predominant by the direct coulombic explosion.

An experimental investigation of the dissociative ionization process of argon cluster ions induced by electron impact

Utilizing the Cold Target Recoil Ions Momentum Spectrometer (COLTRIMS), dissociative ionization of argon cluster was experimentally investigated by electron impact. The recoil ions produced both in the pure ionization process and the dissociative ionization channels are measured with collision energies from 100 and 1000 eV. The ratios of the dimer ions from pure ionization (Ar2P+) and the dimer ions from small cluster dissociation (Ar+2D) to the atomic argon ion (Ar+) in different stagnation pressures were obtained.

Dielectronic recombination experiment of P-like Tin on HIRFL-CSRm at Lanzhou

Total recombination rate coefficients of Sn-112(35+) ions have been firstly measured by employing the electron-ion merged-beams technique on the main cooler storage ring at Lanzhou. Using an electron beam energy detuning system, we precisely tuned the relative energies from 0 to 6.0 eV between the electron beam and the ion beam (momentum spread Delta p/p similar to 5 x 10(-4)). A multi-configuration Breit-Pauli calculation utilizing kappa-averaged relativistic orbitals has been carried-out for the recombination rate coefficients. We find that there are obvious differences between the experimental total rate coefficients and the theoretical calculations.