Z.K. Huang

Study of dielectronic recombination at the CSRm using lithium-like Ar15+ ions

The main cooler storage ring (CSRm) of the HIRFL facility in Lanzhou, China is equipped with an electron-cooler and denotes an ideal platform for dielectronic recombination (DR) experiments. In order to fully understand our DR experimental setup and especially the electron energy detuning system, we have performed a DR calibration experiment using the Li-like argon ions at the CSRm because Ar15+ has a simple electronic structure and the DR spectrum can be calculated with an ultra-high precision and be compared with the existing experimental data. The experiment was carried out over the center-of-mass energy range 0–32 eV that includes all DR resonance associated with 2S1/2 → 2p1/2 and most of the 2S1/2 → 2p3/2 excitations. We present the details of the experimental technique and the DR experimental resonance spectrum of the Ar15+.

Proposal for precision determination of 7.8 eV isomeric state in 229Th at heavy ion storage ring

The ultraviolet optical transition of the isomeric state in 229Th has attracted much attention recently due to its potential application to building an atomic/nuclear clock with ultra-high precision. However, the lowest nuclear excitation energy and the lifetime of the first excited state of 229Th were not measured directly and precisely until now, and how to precisely determine this isomer state of the 229Th is an urgent requirement. Here an experimental approach of using a technique similar to that of dielectronic recombination to measure the transition energy of the isomer state of 229Th at heavy ion storage rings is described. It is expected that the resonant transition can be found and determined with a precision better than several milli-eV.

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.

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.

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.

Progress of laser cooling of relativistic Li-like C 3+ ion beams at the CSRe*

Laser cooling is one of the most promising techniques to reach high phase-space densities for relativistic heavy ion beams. Realizing a crystalline ion beam is one of the ultimate goals of laser cooling of heavy ion beams at storage rings [1]. Preparations for laser cooling of relativistic lithium-like C are being made at the experimental cooler storage ring (CSRe) in Lanzhou, China [2]. In September 2014 a test experiment was performed with C ion beams at an energy of 122 MeV/u on the CSRe with a pulsed laser system. A schematic view of the experimental setup is shown in figure 1. In the experiment C ions were produced by an Electron Cyclotron Resonance ion source (ECR). In the ECR, a significant fraction of O was produced alongside. Then the ions were accelerated by a Sector Focused Cyclotron (SFC), and injected into the main Cooler Storage Ring (CSRm). After accumulation and acceleration in the CSRm, the ion beams were extracted and injected into the CSRe at the energy of 122 MeV/u (at a velocity of 47% of the speed of light). Since the circumference of the CSRe is 128.8 m, this beam energy lead to the revolution frequency of 1.087 MHz. A pulsed UV laser system from HZDR was employed for this test laser cooling experiment. The closed 2s1/2―2p1/2 optical transition at a wavelength of 0 155.07 uf06c uf03d nm of the Li-like carbon ions was Doppler-