G Q Xiao

The heavy ion cooler-storage-ring project (HIRFL-CSR) at Lanzhou

HIRFL-CSR, a new ion Cooler-Storage-Ring (CSR) project, is the post-acceleration system of the Heavy Ion Research Facility in Lanzhou (HIRFL). It consists of a main ring (CSRm) and an experimental ring (CSRe). From the HIRFL cyclotron system the heavy ions will be accumulated, cooled and accelerated in the CSRm, then extracted fast to produce radioactive ion beams (RIB) or highly charged heavy ions. Those secondary beams will be accepted and stored by the CSRe for many internal-target experiments with electron cooling.

RIBLL, the radioactive ion beam line in Lanzhou

A fragment separator, the Radioactive Ion Beam Line in Lanzhou, has been constructed at the Heavy Ion Research Facility of Lanzhou and in operation since January 1998. In this paper, the features of the structure and performance are described in detail. Some early stage results are presented also.

Properties and performance of two wide field of view Cherenkov/fluorescence telescope array prototypes

A wide field of view Cherenkov/fluorescence telescope array is one of the main components of the Large High Altitude Air Shower Observatory project. To serve as Cherenkov and fluorescence detectors, a flexible and mobile design is adopted for easy reconfiguring of the telescope array. Two prototype telescopes have been constructed and successfully run at the site of the ARGO-YBJ experiment in Tibet. The features and performance of the telescopes are presented

OVERVIEW ON THE HIRFL-CSR FACILITY

The status of the HIRFL (Heavy Ion Facility in Lanzhou) – Cooler Storage Ring (CSR) at the IMP is reported. The main physics goals at the HIRFL-CSR are the researches on nuclear structure and decay property, EOS of nuclear matter, hadron physics, highly charged atomic physics, high energy density physics, nuclear astrophysics, and applications for cancer therapy, space industries, materials and biology sciences. The HIRFL-CSR is the first ion cooler-storage-ring system in China, which consists of a main ring (CSRm), an experimental ring (CSRe) and a radioactive beam line (RIBLL2). The two existing cyclotrons SFC (K = 70) and SSC (K = 450) are used as its injectors. The 7 MeV/u 12C6+ ions were stored successfully in CSRm with the stripping injection in January 2006. After that, realized were the accelerations of 12C6+, 36Ar18+, 78Kr28+ and 129Xe27+ ions with energies of 1 GeV/u, 1 GeV/u, 450 MeV/u and 235 MeV/u, respectively, including accumulation, electron cooling and acceleration. In 2008, the first two isochronous mass measurement experiments with the primary beams of 36Ar18+ and 78Kr28+ were performed at CSRe with the Δp/p ~ 10-5.

A Progress Report of 320 kV Multi-discipline Research Platform for Highly Charged Ions

A dedicated platform for multi-disciplinary research with highly charged ions has been constructed, and an all-permanent magnet ECR ion source was built and installed in the beamline. Five experimental terminals are established for interdisciplinary Research. The high voltage supplied to the platform has reached 320 kV. The commissioning of the platform is successful, different ion beams have been provided for experimental studies, and the current status will be reported.

FIRST ISOCHRONOUS MASS MEASUREMENTS AT CSRe

With the commissioning of the Cooler Storage Ring at the Heavy Ion Research Facility in Lanzhou (HIRFL-CSR), a pilot experiment operating the CSRe in isochronous mode to test the power of HIRFL-CSR for measuring the mass of the short-lived nucleus was performed in December of 2007. The transition point γt of CSRe in isochronous mode is 1.395 which corresponds to the energy about 368 MeV/u for the ions with atomic number-to-charge ratio A/q = 2. The fragments with A/q = 2 of 36Ar were injected into CSRe and their revolution frequencies were measured with a fast time pick-up detector with a thin foil in the circulating path of the ions. A mass resolution of better than 105 for m/Δm was achieved.

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+.

The first test experiment performed at the electron cooler of storage rings in Lanzhou

The cooler storage ring (CSR) project was launched in 2000 at the Institute of Modern Physics, Chinese Academy of Sciences, Lanzhou. In 2007, the installation was completed and the commissioning of CSRs gained great success, a new highly precise generation of collision experiments will become accessible even for the heaviest ion species. A commissioning RR experiment was performed at the electron cooler with Ar18+ ions, the results are reported. And the further development of the experiments at cooler will be discussed.

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.

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.