Intense beam production of highly charged heavy ions by the superconducting electron cyclotron resonance ion source SECRAL (invited)

There has been increasing demand to provide higher beam intensity and high enough beam energy for heavy ion accelerator and some other applications, which has driven electron cyclotron resonance (ECR) ion source to produce higher charge state ions with higher beam intensity. One of development trends for highly charged ECR ion source is to build new generation ECR sources by utilization of superconducting magnet technology. SECRAL (superconducting ECR ion source with advanced design in Lanzhou) was successfully built to produce intense beams of highly charged ion for Heavy Ion Research Facility in Lanzhou (HIRFL). The ion source has been optimized to be operated at 28 GHz for its maximum performance. The superconducting magnet confinement configuration of the ion source consists of three axial solenoid coils and six sextupole coils with a cold iron structure as field booster and clamping. An innovative design of SECRAL is that the three axial solenoid coils are located inside of the sextupole bore in order to reduce the interaction forces between the sextupole coils and the solenoid coils. For 28 GHz operation, the magnet assembly can produce peak mirror fields on axis of 3.6 T at injection, 2.2 T at extraction, and a radial sextupole field of 2.0 T at plasma chamber wall. During the commissioning phase at 18 GHz with a stainless steel chamber, tests with various gases and some metals have been conducted with microwave power less than 3.5 kW by two 18 GHz rf generators. It demonstrates the performance is very promising. Some record ion beam intensities have been produced, for instance, 810 e mu A of O7+, 505 e mu A of Xe20+ 306 e mu A of Xe27+, and so on. The effect of the magnetic field configuration on the ion source performance has been studied experimentally. SECRAL has been put into operation to provide highly charged ion beams for HIRFL facility since May 2007.

兰州重离子加速器团簇内靶装置控制系统设计；Design of a Control System for HIRFL-CSRe Internal Target Facility in Lanzhou

介绍了兰州重离子加速器冷却储存环(HIRFL-CSR)的实验环(CSRe)团簇内靶装置控制系统的设计。该内靶系统由多种设备构成,包括喷嘴测温与加热控制子系统、真空与阀门监测/控制子系统、分子泵监测与控制子系统、数据处理与流程软件子系统等部分。该系统在内靶实验中工作状态良好,满足了内靶实验的需求。在该控制系统的支持下,2010年1月第一轮辐射电子俘获物理实验顺利完成。

Role of five-quark components in radiative and strong decays of the Lambda(1405) resonance

Within an extended chiral constituent quark model, the three- and five-quark structure of the S-01 resonance Lambda(1405) is investigated. Helicity amplitudes for electromagnetic decays [Lambda(1405)->Lambda(1116)gamma, Sigma(1194)gamma] and transition amplitudes for strong decays [Lambda(1405)->Sigma(1194)pi, K- p] are derived, as well as the relevant decay widths. The experimental value for the strong decay width, Gamma(Lambda(1405)->(Sigma pi)degrees) = 50 +/- 2MeV, is well reproduced with about 50% of a five-quark admixture in the Lambda(1405). Important effects owing to the configuration mixing among Lambda P-2(1)A, Lambda P-2(8)M, and Lambda P-4(8)M are found. In addition, transitions between the three- and the five-quark components in the baryons turn out to be significant in both radiative and strong decays of the Lambda(1405) resonance.

CSRe团簇内靶温度闭环控制器设计；Design of Closed Loop Temperature Controller for CSRe Internal Target System

介绍了国家重大科学工程项目——兰州重离子加速器冷却存储环(HIRFL-CSR)的实验环(CSRe)团簇内靶温度闭环控制器的设计。该控制器给气体喷嘴处测温电阻提供长时间稳定度为0.1%的1mA恒定电流,通过12位ADC得到喷嘴温度,并通过混合信号处理器MSP430F149来实现制冷/加热闭环操作。在多种不同实验气体的情况下,该控制器的温度控制精度小于0.5K。目前,该控制器在现场工作良好。

New development of advanced superconducting electron cyclotron resonance ion source SECRAL (invited)

Superconducting electron cyclotron resonance ion source with advance design in Lanzhou (SECRAL) is an 18-28 GHz fully superconducting electron cyclotron resonance (ECR) ion source dedicated for highly charged heavy ion beam production. SECRAL, with an innovative superconducting magnet structure of solenoid-inside-sextupole and at lower frequency and lower rf power operation, may open a new way for developing compact and reliable high performance superconducting ECR ion source. One of the recent highlights achieved at SECRAL is that some new record beam currents for very high charge states were produced by 18 GHz or 18+14.5 GHz double frequency heating, such as 1 e mu A of Xe-129(43+), 22 e mu A of Bi-209(41+), and 1.5 e mu A of Bi-209(50+). To further enhance the performance of SECRAL, a 24 GHz/7 kW gyrotron microwave generator was installed and SECRAL was tested at 24 GHz. Some promising and exciting results at 24 GHz with new record highly charged ion beam intensities were produced, such as 455 e mu A of Xe-129(27+) and 152 e mu A of Xe-129(30+), although the commissioning time was limited within 3-4 weeks and rf power only 3-4 kW. Bremsstrahlung measurements at 24 GHz show that x-ray is much stronger with higher rf frequency, higher rf power. and higher minimum mirror magnetic field (minimum B). Preliminary emittance measurements indicate that SECRAL emittance at 24 GHz is slightly higher that at 18 GHz. SECRAL has been put into routine operation at 18 GHz for heavy ion research facility in Lanzhou (HIRFL) accelerator complex since May 2007. The total operation beam time from SECRAL for HIRFL accelerator has been more than 2000 h, and Xe-129(27+), Kr-78(19+), Bi-209(31+), and Ni-58(19+) beams were delivered. All of these new developments, the latest results, and long-term operation for the accelerator have again demonstrated that SECRAL is one of the best in the performance of ECR ion source for highly charged heavy ion beam production. Finally the future development of SECRAL will be presented.

Swelling behaviour of alginate-chitosan microcapsules prepared by external gelation or internal gelation technology

Swelling behaviour is one of the important properties for microcapsules made by hydrogels, which always affects the diffusion and release of drugs when the microcapsules are applied in drug delivery systems. In this paper, alginate-chitosan microcapsules were prepared by different technologies called external or internal gelation process respectively. With the volume swelling degree (S-w) as an index, the effect of properties of chitosan on the swelling behaviour of both microcapsules was investigated. It was demonstrated that the microcapsules with low molecular weight and high concentration of chitosan gave rise to low S-w. Considering the need of maintaining drug activity and drug loading, neutral pH and short gelation time were favorable. It was also noticed that S-w of internal gelation microcapsules was lower than that of external gelation microcapsules, which was interpreted by the structure analysis of internal or external gelation Ca-alginate beads with the aid of confocal laser scanning microscope. (C) 2004 Elsevier Ltd. All rights reserved.

Photodissociation dynamics of the methyl radical at 212.5 nm: Effect of parent internal excitation

Photodissociation dynamics of the CH3 radical at 212.5 nm has been investigated using the H atom Rydberg tagging time-of-flight method with a pure CH3 radical source generated by the photolysis of CH3I at 266 nm. Time-of-flight spectra of the H atom products from the photolysis of both cold and hot methyl radicals have been measured at different photolysis polarizations. Experimental results indicate that the photodissociation of the methyl radical in its ground vibrational state at 212.5 nm excitation occurs on a very fast time scale in comparison with its rotational period, indicating the CH3 dissociation at 212.5 nm occurs on the excited 3s Rydberg state surface. Experimental evidence also shows that the photodissociation of the methyl radical in the nu(2)=1 state of the umbrella mode at 212.5 nm excitation is characteristically different from that in the ground vibrational state. (C) 2004 American Institute of Physics.

Autler-townes splitting in the multiphoton resonance ionization spectrum of molecules produced by ultrashort laser pulses

We report for the first time the proper conditions to observe Autler-Townes splitting (ac-Stark splitting) from vibrationally coherent states belonging to the different electronic terms of a diatomic molecule. Wave packet dynamics simulations demonstrate that such a process is feasible by multiphoton resonance ionization of the molecule Na-2 with a single ultrashort intense laser pulse. With the ultrahigh time resolution of a femtosecond laser pulse, one can directly measure the absolute value of the transition dipole moment between any kinds of molecular states by this kind of Autler-Townes splitting, which is a function of the internuclear distance R.

Identifying the isolated transition metal ions/oxides in molecular sieves and on oxide supports by UV resonance Raman spectroscopy

Isolated transition metal ions/oxides in molecular sieves and on surfaces are a class of active sites for selective oxidation of hydrocarbons. Identifying the active sites and their coordination structure is vital to understanding their essential role played in catalysis and designing and synthesizing more active and selective catalysts. The isolated transition metal ions in the framework of molecular sieves (e.g., TS-1, Fe-ZSM-5, and V-MCM-41) or on the surface of oxides (e.g., MoO3/Al2O3 and TiO2/SiO2) were successfully identified by UV resonance Raman spectroscopy. The charge transfer transitions between the transition metal ions and the oxygen anions are excited by a UV laser and consequently the UV resonance Raman effect greatly enhances the Raman signals of the isolated transition metal ions. The local coordination of these ions in the rigid framework of molecular sieves or in the relatively flexible structure on the surface can also be differentiated by the shifts of the resonance Raman bands. The relative concentration of the isolated transition metal ion/oxides could be estimated by the intensity ratio of Raman bands. This study demonstrates that the UV resonance Raman spectroscopy is a general technique that can be widely applied to the in-situ characterization of catalyst synthesis and catalytic reactions. (C) 2003 Elsevier Science (USA). All rights reserved.

Preparation of uniform calcium alginate gel beads by membrane emulsification coupled with internal gelation

With the objective of making calcium alginate gel beads with small and uniform size, membrane emulsification coupled with internal gelation was proposed. Spherical gel beads with mean size of about 50 mum, and even smaller ones in water, and with narrow size distribution were successfully obtained. Experimental studies focusing mainly on the effect of process parameters on bead properties were performed. The size of the beads was mainly dependent on the diameter of the membrane pores. High transmembrane pressure made for large gel beads with wide size distribution. Low sodium alginate concentration produced nonspherical beads, whereas a high concentration was unsuitable for the production of small beads with narrow distribution. Thus 1.5% w/v was enough. A high surfactant concentration favored the formation of small beads, but the adverse effect on mass transfer should be considered in this novel process. (C) 2002 Wiley Periodicals, Inc.