Intrabeam scattering of heavy ions at HIRFL-CSR

Small-angle multiple intrabeam scattering (IBS) is an important effect for heavy-ion storage rings with electron cooling, because the cooling time is determined by the equilibrium between cooling and IBS process. All usually used numerical algorithms of IBS growth rate calculations are based on the model of the collisions proposed by A.Piwinski, but this result is a multidimensional integral. In this paper, the IBS growth rates are simulated for HIRFL-CSR using symmetric elliptic integral method, and compared with several available IBS code results.

Probing the high density behavior of the symmetry energy by using the free neutron-proton ratio

Based on the isospin- and momentum-dependent transport model IBUU04, the transverse momentum distributions of the free neutron-proton ratio in the Sn-132+(124) Sn reaction system at mid-central collisions with beam energies of 400/A MeV, 600/A MeV and 800/A MeV are studied by using two different symmetry energies. It is found that the free neutron-proton ratio as a function of the transverse momentum at the mid-rapidity is very sensitive to the density dependency of the symmetry energy especially at incident energies around 400/AMeV.

Probing the high density behavior of the symmetry energy by using proton elliptic flow

Based on the isospin- and momentum-dependent transport model IBUU04, we calculated the reaction of the Sn-132+Sn-124 systems in semi-central collisions at beam energies of 400/A MeV, 600/A MeV and 800/A MeV by adopting two different density dependent symmetry energies. It was found that the proton differential elliptic flow as a function of transverse momentum is quite sensitive to the density dependence of symmetry energy, especially for the considered beam energy range. Therefore the proton differential elliptic flow may be considered as a robust probe for investigating the high density behavior of symmetry energy in intermediate energy heavy ion collisions.

Optimization of the HIRFL-CSR cluster target

A new gas delivery system is designed and installed for HIRFL-CSR cluster target. The original blocked nozzle is replaced by a new one with the throat diameter of 0.12mm. New test of hydrogen and argon gases are performed. The stable jets can be obtained for these two operation gases. The attenuation of the jet caused by the collision with residual gas is studied. The maximum achievable H-2 target density is 1.75x10(13) atoms/cm(3) with a target thickness of 6.3x10(12) atoms/cm(2) for HIRFL-CSR cluster target. The running stability of the cluster source is tested both for hydrogen and argon. The operation parameters for obtaining hydrogen jet are optimized. The results of long time running for H-2 and Ar cluster jets look promising. The jet intensity has no essential change during the test for H-2 and Ar.

Temperature effects of CsI(Tl) crystal detector with APD readout

The temperature dependences of the light output of CsI(Tl) crystal grown at IMP and of the gain of the Hamamatsu S8664-1010 avalanche photodiode (APD) have been investigated systematically. The light output of the CsI(Tl) crystal increases with temperature by 0.67%/degrees C in the region from -2 degrees C to 8 degrees C, and by 0.33%/degrees C in the region from 8 degrees C to 25 degrees C, while the gain of the tested APD decreases by -3.68%/degrees C (working voltage 400V) on average in the room temperature range. The best energy resolution 5.1% of the CsI(Tl) with APD was obtained for the 662keV gamma ray from Cs-137 radiation source.

First results of SECRAL at 18GHz for intense beam production of highly charged ions

A Superconducting ECR ion source with Advanced design in Lanzhou (SECRAL) was successfully built to produce intense beams of highly charged ions for Heavy Ion Research Facility in Lanzhou (HIRFL). The ion source has been optimized to be operated at 28GHz 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. For 28GHz operation, the magnet assembly can produce peak mirror fields on axis 3.6T at injection, 2.2T at extraction and a radial sextupole field of 2.0T at plasma chamber wall. A unique feature 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. During the ongoing commissioning phase at 18GHz with a stainless steel chamber, tests with various gases and some metals have been conducted with microwave power less than 3.2kW and it turned out the performance is very promising. Some record ion beam intensities have been produced, for instance, 810e mu A of O7+, 505e mu A of Xe20+, 306e mu A of Xe27+, 21e mu A of Xe34+, 2.4e mu A of Xe38+ and so on. To reach better results for highly charged ion beams, further modifications such as an aluminium chamber with better cooling, higher microwave power and a movable extraction system will be done, and also emittance measurements are being prepared.

Structure analysis of the SECRAL superconducting magnet system

An advanced superconducting ECR ion source named SECRAL has been constructed at Institute of Modern Physics of Chinese Academy of Sciences, whose superconducting magnet assembly consists of three axial solenoid coils and six sextupole coils with a cold iron structure as field booster and clamp. In order to investigate the structure of sextupole coils and to increase the structural reliabilities of the magnet system, global and local structural analysis have been performed in various operation scenarios. Winding pack and support structure design of magnet system, mechanical calculation and stress analysis are given in this paper. From the analysis results, it has been found that the magnet system is safe in the referential operation scenarios and the configuration of the magnet complies with design requirements of the SECRAL.

Commissioning test of LAPECR2 source on the 320kV HV platform

The high charge state all permanent Electron Cyclotron Resonance Ion Source (ECRIS) LAPECR2 (Lanzhou All Permanent magnet ECR ion source No.2) has been successfully put on the 320kV HV platform at IMP and also has been connected with the successive LEBT system. This source is the largest and heaviest all permanent magnet ECRIS in the world. The maximum mirror field is 1.28T (without iron plug) and the effective plasma chamber volume is as large as circle divide 67mm x 255mm. It was designed to be operated at 14.5GHz and aimed to produce medium charge state and high charge state gaseous and also metallic ion beams. The source has already successfully delivered some intense gaseous ion beams to successive experimental terminals. This paper will give a brief overview of the basic features of this permanent magnet ECRIS. Then commissioning results of this source on the platform, the design of the extraction system together with the successive LEBT system will be presented.

Research on metallic ion beam production at IMP

Since 1998, many experiments for metallic ion production have been done on LECR2 (Lanzhou ECR ion source NO.2), LECR3 (Lanzhou ECR ion source NO.3) and SECRAL (Superconductiong ECR ion source Advanced design in Lanzhou) at Institute of Modern Physics. The very heavy metallic ion beams such as those of uranium were also produced by the plasma sputtering method, and supplied for HIRFL (Heavy Ion Research Facility in Lanzhou) accelerators successfully. During the test, 11.5e mu AU(28+), 9e mu AU(24+) were obtained. Some ion beams of the metal having lower melting temperature such as Ni and Mg ion beams were produced by oven method on LECR3 too. The consumption rate was controlled to be lower for Mg-26 ion beams production, and the minimum consumption was about 0.3mg per hour. In this paper, the main experimental results are given. Some discussions are made for some experimental phenomena and results, and some conclusions are drawn.

Lanzhou all permanent ECR ion source No.1 - LAPECR1

The Lanzhou All Permanent magnet ECR ion source NO. 1 (LAPECR1) is the first all permanent magnet multiple ECRIS made in IMP. This ECRIS is running at 14.5GHz and can provide intense low charge state ion beams (varying from several to hundreds of e mu A) or medium charge state ion beams (varying from several to tens of e mu A). The size of source body is circle divide 102mmx296mm, the compactness and economical features enable the source suitable to be put on a HV platform or equipped by a small laboratory. This article gives the main parameters of the ion source.

Preliminary results of the updated LECR2 source-LECR2M

The Latest developed LECR2M (Lanzhou ECR No. 2 Modified) source is the updated one of LECR2 (Lanzhou ECR No. 2) source at IMP. It has been assembled on the low energy ion beam experimental platform to produce MCI beams for atomic physics and material physics experimental research. In our updating program, the structure of injection and extraction components has been modified to make the source structure more simple and effective. The hexapole magnet has also been replaced by a new hexapole magnet with higher radial field and larger inner diameter. With this updating, stronger magnetic field confinement of the ECR plasma is possible and better base vacuum condition is also achieved. LECR2M was designed to be operated at 14.5GHz. During the preliminary test, 1.3emA O6+ beam was extracted with the injected rf power of 1.1kW. The source has been used to deliver intense MCI beams for different experiments. After some discussion of the main features of this newly updated source, some of the typical commissioning test results of LECR2M will be presented.

Measurements of bremsstrahlung spectra on SECRAL

The axial emitted bremsstrahlung spectra were measured on SECRAL (Superconducting ECR ion source with Advanced design in Lanzhou) using an HPGe detector. The spectral temperature T-spe was obtained from the linear fit of the spectra in the semi-log present. The evolution of T-spe with microwave power and magnetic field configuration is investigated in this paper.

A compact proton source for space simulation

A compact proton beam source for space simulation has been developed. A compact structure was designed in order to meet the special requirements of miniaturization. Some particular means have been adopted for improving the proton portion and beam transmission at a long distance. The experimental results showed that 8mA/80keV proton beam can be successfully obtained from this source at about 700W input microwave power.

Production of EUV power with SECRAL

The high power EUV source is one of key issues in the development of EUV lithography which is considered to be the most promising technology among the next generation lithography. However neither DPP nor LPP seems to meet the requirements of the commercial high-volume product. Insufficiency of DPP and LPP motivate the investigation of other means to produce the EUV radiation required in lithography. ECR plasma seems to be one of the alternatives. In order to investigate the feasibility of ECR plasma as a EUV light source, the EUV power emitted by SECRAL was measured. A EUV power of 1.03W in 4 pi sr solid angle was obtained when 2000W 18GHz rf power was launched, and the corresponding CE was 0.5%. Considering that SECRAL is designed to produce very high charge state ions, this very preliminary result is inspiring. Room-temperature ECR plasma and Sn plasma are both in the planned schedule.

Influence of isospin dependence of nucleon-nucleon cross section and momentum dependent interaction on the isoscaling in intermediate energy collisions

The influences of the isospin dependent in-medium nucleon-nucleon cross section and the MomentumDependent Interaction(MDI) on the isotope scaling have been investigated within the Isospin dependent Quantum Molecular Dynamics Model(IQMD). The results show that both the isospin dependent in-medium nucleon-nucleon cross section and the momentum interaction reduce the isoscaling parameter a appreciably, which means they decrease the dependence of yield ratios of two systems on the isospin difference between two systems.