X.D. Yang

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.

COMMISSION OF ELECTRON COOLER EC-300 FOR HIRFL-CSR

HIRFL-CSR, a new ion accelerator complex, is under construction at IMP, Lanzhou, China. It is equipped with two electron cooling devices. This article describes the commissioning of cooler at electron energy 300 keV. The cooler is one of the new coolers with some unique manufactured in BINP, Russia. It has a new electron gun producing a hollow electron beam, electrostatic bending and a new structure of solenoid coils at the cooling section. The test results of cooler obtained in Novosibirsk and Lanzhou are reported.

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.

Upgrade of Beijing IR-FEL project

Beijing IR Free-Electron laser facility has been under upgrade in several aspects. For system modification, a new undulator beam line parallel to the old one that permits BFEL to simultaneously operate at two different wavelengths and a beam line to produce coherent synchrotron radiation and Compton back-scattering soft X-ray are being added. Optical beam pipe from undulator output to the experiment rooms is under fabrication. For improvement of the stability of operation, much work had been done to reduce the fluctuations of the electron beam parameters and the time jitter of the RF pulses. For extension of wavelength of operation, Au plated copper mirrors with axial out-coupling hole were used instead of the original multi-layer dielectric mirrors. For improving the laser performance, a new 31/2 cavity RF gun is pending installation, and a self-adaptive, feed-forward control system for beam loading compensation of the microwave electron gun to avoid longitudinal emittance blow-up has been successfully tested. Separate, independent RF power feeds of the RF gun and linac section will be implemented to facilitate the optimization of the operating conditions

Compositional change in human enamel irradiated with MIR free electron laser

The purpose of this study was to investigate compositional changes in human enamel irradiated with the free electron laser (FEL). The exposure on dental enamel at the wavelength of 9.64 μm was observed with the Beijing free electron laser. The distribution of elements in the irradiated or non-irradiated enamel was measured by scanning electron microscope (SEM) with energy-dispersive spectroscopy and synchrotron radiation X-ray fluorescence (SRXRF) in Beijing Synchrotron Radiation Facility (BSRF). The results showed that the P/Ca ratio in the ablation region of enamel at the maximum wavelength of infrared absorption was obviously smaller than that at the non-maximum wavelength. In the ablation region the ratios of P/Ca and Ca/Sr were smaller than those in the non-ablation region. The distributions of P, Ca and Sr in the ablation region were heterogeneous due to the element change caused by FEL irradiation.

Lattice of the CSR

CSR, a new Cooler-Storage-Ring 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 and injected into the CSRe for many internal-target experiments with electron cooling. The experimental ring (CSRe) will be operated with three lattice modes for different experiments. The details of the lattice for the two rings will be described in this paper.

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.

Progress of dielectronic recombination experiment at CSRm

The storage ring equipped with an electron cooler is an ideal platform for dielectronic recombination (DR) experiments. In order to fulfil the requirement of DR measurements at the main Cooler Storage Ring, a detuning system for the precision control of the relative energy between the ion beam and the electron beam has been installed on the electron cooler device. The test run using 7.0 MeV/u C6+ beam was performed to examine the influence of this system on the performance of the stored ion beam. The Schottky spectra and the ion beam currents were recorded to monitor the beam status. The influence of pulse heights and widths of the detuning voltage on the ion beam was investigated. For the small pulse height, the experimental results from the Schottky spectrum were in good agreement with the theoretical results. The frequency shift in the Schottky spectrum is significantly reduced for the short pulse width. For the large pulse height, an oscillation phenomenon was observed. From the Schottky spectrum, we found the oscillation amplitude is dependent on the pulse width of detuning and the ion beam intensity. The detailed description of the phenomenon and the theoretical model based on the plasma oscillation was discussed in this paper.

News from the CSR storage ring

Testing runs of experiments were performed at the Cooler Storage Ring in Lanzhou. The recombination of bare argon ions and electron was observed at the electron. The masses of radioactive nuclei produced by projectile fragmentation were measured in isochronous mode. An overview of the most recent experiments will be presented.

Free electron laser induced two-photon photoconductivity in Hg1-xCdxTe

The Beijing free electron laser ( BFEL) has been employed for the first time to study the nonlinear photoconductivity characteristics of the typical infrared photoelectronic material Hg1-xCdxTe Taking advantage of the high photon flux density of BFEL, we have investigated the photoconductivity characteristics in Hg1-xCdx Te induced by two-photon absorption by means of the photoconductivity technique, observed the photoconductivity signals saturation, and studied the two-photon photoconductivity characteristics on different bias voltages across the sample.