Wenlong Zhan

PRESENT STATUS OF HIRFL IN LANZHOU

HIRFL has been upgraded for basic research on nuclear physics, atomic physics, irradiative material and biology from beginning of this decade. So far, the main performances of HIRFL have improved in the beam species from light ion to uranium and the maximum beam intensities reaching ~10μA from SFC, 1.5 μA from SSC. Therefore, some experiments have been performed during this period, especially, on new isotope synthesis and unstable nuclear physics. The new upgrading project Cooling Storage Ring (CSR) is under commissioning by ~2p μA carbon beam stripping injection. About 109 C ion have stored inside CSRm, and part of them have been cooling down by the electron cooler. The acceleration of CSRm also has been test successful. Some future experiment are under development.

Radioactive ion beam line in Lanzhou

Radioactive ion beam line in Lanzhou (RIBLL) has been constructed for the production of short-lived radioactive nuclei and studies of exotic nuclei far from the β-stability line. It has been put into operation recently at the National Laboratory of Heavy Ion Accelerator Lanzhou. RIBLL consists of two doubly achromatic parts with a solid acceptance ΔΩ⩾6.5 msr, momentum acceptance Δp/p=±5% and maximum magnetic rigidityBpmax=4.2 Tm. The second part of RIBLL serving as a spectrometer gives an element resolutionZ/ΔZ>150 and mass resolutionA/ΔA>300. The polarized secondary beams can be obtained by using a swinger dipole magnet to change the incident direction of primary projectile from 0° to 5°. The shortest lift time for secondary beams on RIBLL is less than 1 μs. First experiments were performed with neutron rich nuclei for understanding the properties of halo nuclei and exotic nuclear reactions.

Commissioning of HIRFL‐CSR and its Electron Coolers

The brief achievements of HIRFL‐CSR commissioning and the achieved parameters of its coolers were presented. With the help of electron cooling code, the cooling time of ion beam were extensive simulated in various parameters of the ion beam in the HIRFL‐CSR electron cooling storage rings respectively, such as ion beam energy, initial transverse emittance, and momentum spread. The influence of the machine lattice parameters‐betatron function, and dispersion function on the cooling time was investigated. The parameters of electron beam and cooling devices were taken into account, such as effective cooling length, magnetic field strength and its parallelism in cooling section, electron beam size and density. As a result, the lattice parameters of HIRFL‐CSR were optimal for electron cooling, and the parameters of electron beam can be optimized according to the parameters of heavy ion beam.

A latest developed all permanent magnet ECRIS for atomic physics research at IMP

Electron cyclotron resonance (ECR) ion sources have been used for atomic physics research for a long time. With the development of atomic physics research in the Institute of Modern Physics (IMP), additional high performance experimental facilities are required. A 300kV high voltage (HV) platform has been under construction since 2003, and an all permanent magnet ECR ion source is supposed to be put on the platform. Lanzhou all permanent magnet ECR ion source No. 2 (LAPECR2) is a latest developed all permanent magnet ECRIS. It is a 900kg weight and ∅650mm×562mm outer dimension (magnetic body) ion source. The injection magnetic field of the source is 1.28T and the extraction magnetic field is 1.07T. This source is designed to be running at 14.5GHz. The high magnetic field inside the plasma chamber enables the source to give good performances at 14.5GHz. LAPECR2 source is now under commissioning in IMP. In this article, the typical parameters of the source LAPECR2 are listed, and the typical results of the ...

The Progress of the HIRFL-CSR Project and the Commissioning of the Cluster Target

HIRFL-CSR, a new cooler-storage-ring project, is the post-acceleration system of the Heavy Ion Research Facility in Lanzhou (HIRFL) consisting of a main ring (CSRm) and an experimental ring (CSRe). The construction of the HIRFL-CSR complex is nearing completion. The stored beam in the CSRm has been observed. Recently, the stored beam was accelerated from 7 MeV/u to 30 MeV/u. The cluster target is located in one straight section of the CSRe providing cluster jet targets of inert gases and small molecular gases. The cluster target has been finished and the results of the test running are presented.

Breakup of 33.4 MeV/u 17N on a 9Be Target

Correlation measurements of neutrons and fragments have been performed in a reaction of 33.4 MeV/u 17N on a 9Be target. Energy spectra of n and nitrogen fragments were obtained at different angles. Based on the nuclear diffraction dissociation model, the measured energy spectra and the neutron angular distributions were reproduced quite well assuming that 17N was composed of 16N and n or 15N and 2n interacting with the nonlocal separable potential. The satisfactory agreement between the theoretical calculations and the experimental data shows that the contribution of Coulomb dissociation is negligible in the reaction concerned.

Detector calibration by Monte Carlo simulation based on the energy-range relationship of energetic ions

The experimental measurement of the total interaction cross sections of N, C, B, and Be isotopes on C-12 target at medium energies is described. A new formula that gives a good description of the energy-range relationship of energetic ions over a wide energy range is presented. The energy calibration of detectors is made by a Monte Carlo simulation method based on this new formula.

The commissioning progress of the cooler storage ring HIRFL-CSR in Lanzhou

HIRFL-CSR is a multi-purpose cooler-storage-ring system constructed at the Institute of Modern Physics, Chinese Academy of Sciences in Lanzhou, China. Construction of the HIRFL-CSR storage ring complex has been finished, and passed the government check and acceptance, recently. The first stored beam in the CSRm was obtained in January 2006 using stripping injection. The commissioning got great progress in 2007. In early January 2007 electron cooling in CSRm was successfully done, and the multiple multi-turn injection was successively realized for 12C6+, 36Ar18+ and 129Xe27+ beams, respectively. The 129Xe27+ beams was extracted from the main ring by fast extraction. The 660MeV/u 12C6+ was injected into the experimental ring and reached an intensity of 15mA there. The first two physics experiments were done in December 2007 including the mass measurement in isochronous mode in the experimental ring. The 300MeV/u 12C4+ ions were successfully slow-extracted from the main ring in early 2008. This paper presents the main commissioning results.

Possible proton halo and skin in light proton-rich nucleus

Measurements of reaction cross section (sigma(R)) for some proton-rich nuclei (N = 8, 10, 12 isotones) on carbon target at intermediate energies have been performed on RIBLL of HIRFL by a transmission method. The experimental sigma(R) values for Al-23 and P-27 are abnormally large compared with its neighboring nuclei and that of F-17 has an enhancement compared with neighboring isotopes. The calculation of relativistic density-dependent Hartree (RDDH) approach shows there is proton-halo structure in Al-23 and P-27 and there is a proton-skin in F-17. The significance of these measurements was discussed.

The design and structure of the ultra-high vacuum system of HIRFL-CSR

To minimize the beam loss due to charge exchange of very heavy ions with the residual gas molecules, ultra-high vacuum of 6×10−9u2009Pa is required for the HIRFL-CSR facility, which is the lowest pressure in a large vacuum system in China up to now. The total length of the system is about 450 meters and the total inner surface is about 263 square meters. More than 500 standard vacuum components are needed and more than 400 different chambers have to be manufactured. A lot of researches have been down to try to find out the experiences to obtain the required pressure. In this article the following contents are described: the layout of the system; the structure of main vacuum chambers; the treatment metherd to reduce the outgassing rate of the chamber wall surfaces; vacuum equipment; pressure distribution and the progress of the system.