Cooler Storage Ring Research Articles

A tracking system for the external target facility of CSR

A tracking system composed of three multi-wires proportional chambers (MWPCs) for the external target facility of the Cooler Storage Ring is reported in this paper. The active areas of the MWPCs are 518 mm × 400 mm, 582 mm × 450 mm, and 710 mm × 500 mm. Each MWPC consists of a series of alternately placed cathode and anode wire planes and can measure position along the directions of −30°, 0°, and 30° relative to horizontal. The construction and operation of the detectors are described, and a method for track reconstruction is introduced. A track-finding efficiency of about 62% and a spatial resolution of 1.21 mm have been achieved. The pion and proton can be identified clearly with the tracking system combined with a time-of-flight system.

K-shell X-ray emission from high energy pulsed C6+ ion beam impacting on Ni target

Accurate measurement of the ionization cross section of the target atom induced by collision between ions and atoms is of great significance for studying the atomic shell process and establishing a suitable theoretical model. The experimental data and the theoretical models mostly concentrate on the cases in the low energy region at present. Only a few experimental data of high energy region are reported due to the limitation of experimental conditions. Which theory is more suitable to describe the ionization cross section of the inner shell of the target atom caused by the high energy heavy ions, is necessarily studied experimentally. The C6+ ions provided by the Heavy Ion Research Facility in Lanzhou Electron Cooling Storage Ring, are used to bombard the Ni target, in which the K-shell X-ray of Ni is measured. The incident energies of C6+ ions are 165, 300, 350 and 430 MeV/u respectively. Through analyzing the intensity ratio of K/K X-ray of Ni, it is found that the influence of incident energy on the intensity ratio of K/K X-ray is not obvious. The intensity ratios of this experiment are greater than the experimental values of incident proton and the calculated values based on the Hartree-Slater theory, which may be caused by the multiple-ionization of the L shell. The production cross sections of Ni K-shell X-ray are calculated by the binary encounter approximation (BEA) model, the plane wave Born approximation (PWBA) model and the energy-loss coulomb-repulsion perturbed-stationary-state relativistic (ECPSSR) theory respectively, which are compared with the experimental results in this paper. It is found that the experimental cross section increases with the increasing incident energy, which is consistent with the trend of BEA model estimation, but the experimental value is obviously lower than the theoretical value. We think that BEA model needs to be modified when describing the ionization process in the high energy region.

Status and prospects of the injection complex of the Budker Institute of Nuclear Physics

This article presents the basic systems of the VEPP-5 injection complex of Budker Institute of Nuclear Physics, Siberian Branch, Russian Academy of Sciences. The system of injection–extraction of electron and positron beams is described. The results of measurements of the bunch length made in the electron linear accelerator and the storage–cooler ring by a streak camera are provided. The development of assemblies of a prospective positron conversion system based on a liquid-lead target is also described.

A Flash-ADC data acquisition system developed for a drift chamber array and a digital filter algorithm for signal processing**Supported by National Basic Research Program of China (973) (2015CB856903 and 2014CB845405), partly by National Science Foundation of China (U1332207 and 11375094), and by Tsinghua University Initiative Scientific Research Program

A Flash-ADC data acquisition (DAQ) system has been developed for the drift chamber array designed for the External-Target-Experiment at the Cooling Storage Ring at the Heavy Ion Research Facility, Lanzhou. The simplified readout electronics system has been developed using the Flash-ADC modules and the whole waveform in the sampling window is obtained, with which the time and energy information can be deduced with an offline processing. A digital filter algorithm has been developed to discriminate the noise and the useful signal. With the digital filtering process, the signal to noise ratio (SNR) is increased and a better time and energy resolution can be obtained.

The trigger system for the external target experiment in the HIRFL cooling storage ring**Supported by the National Natural Science Foundation of China (11079003), the Knowledge Innovation Program of the Chinese Academy of Sciences (KJCX2-YW-N27), and the CAS Center for Excellence in Particle Physics (CCEPP).

A trigger system was designed for the external target experiment in the Cooling Storage Ring (CSR) of the Heavy Ion Research Facility in Lanzhou (HIRFL). Considering that different detectors are scattered over a large area, the trigger system is designed based on a master-slave structure and fiber-based serial data transmission technique. The trigger logic is organized in hierarchies, and flexible reconfiguration of the trigger function is achieved based on command register access or overall field-programmable gate array (FPGA) logic on-line reconfiguration controlled by remote computers. We also conducted tests to confirm the function of the trigger electronics, and the results indicate that this trigger system works well.

An automated procedure for the analysis of time-resolved Schottky spectra

The unique combination of facilities and instrumentation available at the GSI Helmholtzzentrum für Schwerionenforschung in Darmstadt, Germany allows us to investigate the decay modes of highly charged ions by Schottky Mass Spectrometry. In single-ion decay spectrometry the fate of single ions cruising in the cooler-storage ring ESR can be followed and their exact decay time is determined. For a fast and repeated analysis of such data sets a highly automated procedure has been developed. The method is demonstrated with a measurement of the He-like 142Pm59+ which decays by electron-capture and β+ decay to 142Nd. For the total decay constant we find a value of λ=0.0164±0.0010s−1 in the rest frame of the ions and the branching ratio λβ+/λEC=3.68±0.014.

Recent results on mass measurements of exotic nuclides in storage rings

Storage ring mass spectrometry allows for simultaneous measurements of masses of a large amount of nuclides. Two measurement techniques, isochronous and Schottky mass spectrometry, are applied. The clear advantage of the storage ring mass spectrometry is that only a few particles are required to measure their mass with high accuracy. In this contribution we address the most recent results obtained at the two presently operating facilities, namely the Experimental Storage Ring (ESR) in Darmstadt and the Experimental Cooler-Storage Ring (CSRe) in Lanzhou.

Side-effects of the space charge field introduced by a hollow electron beam in the electron cooler of CSRm**Supported by National Natural Science Foundation of China (11375245)

An electron cooler is used to improve the quality of the ion beam in a synchrotron; however it also introduces a nonlinear electromagnetic field to the accelerator, which causes tune shift, tune spread and may drive resonances leading to ion beam loss. In this paper the tune shift and the tune spread caused by the nonlinear electromagnetic field of a hollow electron beam is investigated, and the resonance driving terms of the nonlinear electromagnetic field are analysed. The differences are presented compared with a solid electron beam. Calculations are performed for 238U32+ ions of energy 1.272 MeV stored in the main Cooler Storage Ring (CSRm) at the Institute of Modern Physics, Lanzhou. It is found that in this situation the nonlinear field caused by the hollow electron beam does not lead to serious resonances.

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+.

First isochronous mass measurements with two time-of-flight detectors at CSRe

Isochronous mass spectrometry (IMS) established in heavy-ion storage rings has proven to be a powerful tool for mass measurements of short-lived nuclides. In IMS, the revolution times of stored ions should be independent of their velocity spread. However, this isochronous condition is fulfilled only in the first order and in a small range of revolution times. To correct for non-isochronicity, an additional measure of the velocity or magnetic rigidity of each stored ion is required. For this purpose two new time-of-flight (TOF) detectors were installed in one of the straight sections of the experimental cooler storage ring in Lanzhou. It is expected that the resolving power of the IMS will significantly be improved with such a double-TOF arrangement. The double-TOF system was tested in a recent experiment with the 78Kr fragments. Some of the experimental results are presented in this contribution.

Heavy Ions Research Facility in Lanzhou (HIRFL)

Heavy ions accelerator has greatly scientific significance in nuclear physics, atomic physics and astrophysics. It is also of great social needs in many application fields, such as nuclear detection, radiation medicine and medical physics. In addition, Heavy ions accelerator has important application prospects in the interdisciplinary fields of nuclear physics, nuclear technology, radiation biology, material science, biology and agriculture. Therefore, heavy ions accelerator makes great contributions to the promotion of human development and social progress. At present, there are more than 30 large scale heavy ions accelerators. And the main overseas heavy ions accelerators are the BNL-RHIC in the United States, the RIKEN-RIBF in Japan, the MSU-FRIB in the United States, the GANIL-SPIRAL2 in France and the FAIR in Europe which is under construction. In China, however, there are the BRIF in Beijing and the HIRFL in Lanzhou being operation and High Intensity heavy-ion Accelerator Facility (HIAF) which will be built in Huizhou. Heavy Ions Research Facility in Lanzhou (HIRFL), one of the most important research facilities for nuclear physics in the world, is the largest scale heavy-ion accelerator facility with the most ion species and the highest ion energy in China at present. And its main parameters have reached international advanced level. HIRFL is composed of ECR ion source, sector focused cyclotron (SFC), separated sector cyclotron (SSC), radioactive ion beam lines RIBLL1 and RIBLL2, cooler storage rings CSRm and CSRe, and many terminals. HIRFL can accelerate all ion species and provide high quality stable beams and radioactive beams with many ion species and broad energy ranges to carry on the heavy-ion physics and crossing discipline research. This paper is mainly to present the status of HIRFL and its progress, and the development of heavy-ion accelerator facilities at home and abroad are also introduces briefly.

The Dipole Magnets Temperature Monitoring and Interlocking Protection System of HIRFL-CSRm

HIRFL-CSRm is a heavy ion synchrotron, named the main Cooling Storage Ring of Heavy Ion Research Facility of Lanzhou. Its role is to cool and accumulate the injected low energy ion beam, and then accelerate to high energy and extract. So, requirements for performance and safety of the magnet which directly affect the intensity and stability of ion beam is very high. This paper mainly state temperature monitoring and interlocking protection for the dipole magnets of HIRFL-CSRm to protect magnets, reduce the economic loss, and ultimately ensure safe running of HIRFL.

Particle tracking simulation in the CSRe stochastic cooling system**Supported by Innovation Community of National Fund Committee (11221064) and National Key Basic Research and Development Project (2014CB845500)

A stochastic cooling system is under design and construction at HIRFL-CSRe (Heavy Ion Research Facility in Lanzhou - experimental Cooling Storage Ring), with the aim of cooling secondary particles produced at HIRFL-RIBLL2 (2nd Radioactive Ion Beam Line in Lanzhou). The optical layout of CSRe has been optimized to meet the requirements of a stochastic cooling system. In this paper, a particle tracking method is used to investigate both transverse and longitudinal cooling on the basis of the modified optical layout, demonstrating how it can be used to optimize stochastic cooling parameters. Simulation results indicate that the particle tracking method is an innovative and reasonable method to study stochastic cooling. It also has the advantage of discovering the influence of Twiss parameters at the pickups and kickers, which will be explored in further studies.

Simulation of loss of uranium ions due to charge changing processes in the CSRm ring**Supported by National Natural Science Foundation of China (11305227)

Significant beam loss caused by the charge exchange processes and ion impact-induced outgassing may restrict the maximum number of accelerated heavy ions during the high intensity operation of an accelerator. In order to control beam loss due to charge exchange processes and confine the generated desorption gas, tracking of the beam loss distribution and installation of absorber blocks with low-desorption rate material at appropriate locations in the main Cooler Storage Ring (CSRm) at the Institute of Modern Physics, Lanzhou, will be performed. The loss simulation of uranium ions with electron-loss is presented in this report and the conclusion is that most charge changed particles are lost in the second dipole of the super-period structure. The calculation of the collimation efficiency of the CSRm ring will be continued in the future.

RF-bunching of relativistic 12C3+ ion beam for laser cooling experiment at the CSRe

To prepare the upcoming experiment of laser cooling of relativistic 12C3+ ion beams at the experimental cooler storage ring (CSRe), a test experiment was performed with 12C3+ ion beams at an energy of 122 MeV/u on the CSRe, at the Institute of Modern Physics, Lanzhou, China. In this experiment, the main storage ring of CSRm was employed to accumulate and accelerate the ion beam which was injected into the CSRe for the experiments. The number of 12C3+ ions at the CSRe reached 5×108 for every injection, which satisfied the experimental requirement. To fulfil the laser cooling experiment, the 12C3+ ion beams were bunched by sinusoidal waveforms with fixed and sweeping frequencies, respectively. A resonant Schottky pick-up was employed to record the Schottky spectra of these ion beams. The test experimental results demonstrated that the RF-buncher and diagnostic systems at the CSRe worked well and the CSRe was very stable with 12C3+ ion beams, hereby the CSRe is suitable for laser cooling experiment.

Prototype studies on the forward MWDC tracking array of the external target experiment at HIRFL-CSR

A prototype of the forward tracking array consisting of three multiwire drift chambers (MWDC) for the external target experiment (CEE) at the Heavy Ion Research Facility at the Lanzhou -Cooling Storage Ring (HIRFL-CSR) has been assembled and tested using cosmic rays. The signals from the anode wires are amplified and fed to a Flash-ADC to deliver the drift time and charge integration. The performances of the array prototype are investigated under various high voltages. For the tracking performances, after the space-time relation (STR) calibration and the detector displacement correction, the standard deviation of 223 μm of the residue is obtained. The performances of the forward MWDCs tracking array meets the requirements of CEE in design.

High energy density physics research at IMP, Lanzhou, China

Abstract Recent research activities relevant to high energy density physics (HEDP) driven by the heavy ion beam at the Institute of Modern Physics, Chinese Academy of Sciences are presented. Radiography of static objects with the fast extracted high energy carbon ion beam from the Cooling Storage Ring is discussed. Investigation of the low energy heavy ion beam and plasma interaction is reported. With HEDP research as one of the main goals, the project HIAF (High Intensity heavy-ion Accelerator Facility), proposed by the Institute of Modern Physics as the 12th five-year-plan of China, is introduced.

Conceptional design of a heavy ion linac injector for HIRFL-CSRm

A room temperature heavy ion linac has been proposed as a new injector of the main Cooler Storage Ring (CSRm) at the Heavy Ion Research Facility in Lanzhou (HIRFL), which is expected to improve the performance of HIRFL. The linac injector can supply heavy ions with a maximum mass to charge ratio of 7 and an injection kinetic energy of 7.272 MeV/u for CSRm; the pulsed beam intensity is 3 emA with the duty factor of 3%. Compared with the present cyclotron injector, the Sector Focusing Cyclotron (SFC), the beam current from linac can be improved by 10–100 times. As the pre-accelerator of the linac, the 108.48 MHz 4-rod Radio Frequency Quadrupole (RFQ) accelerates the ion beam from 4 keV/u to 300 keV/u, which achieves the transmission efficiency of 95.3% with a 3.07 m long vane. The phase advance has been taken into account in the analysis of the error tolerance, and parametric resonances have been carefully avoided by adjusting the structure parameters. Kombinierte Null Grad Struktur Interdigital H-mode Drift Tube Linacs (KONUS IH-DTLs), which follow the RFQ, accelerate ions up to the energy of 7.272 MeV/u for CSRm. The resonance frequency is 108.48 MHz for the first two cavities and 216.96 MHz for the last 5 Drift Tube Linacs (DTLs). The maximum accelerating gradient can reach 4.95 MV/m in a DTL section with the length of 17.066 m, and the total pulsed RF power is 2.8 MW. A new strategy, for the determination of resonance frequency, RFQ vane voltage and DTL effective accelerating voltage, is described in detail. The beam dynamics design of the linac will be presented in this paper.

Beam loss distribution calculation and collimation efficiency simulation of a cooler storage ring in a heavy ion research facility

The Heavy Ion Research Facility in Lanzhou is an ion cooler storage ring facility in China's Institute of Modern Physics. The beams are accumulated, electron cooled, accelerated, and extracted from the main cooler storage ring (CSRm) to the experimental ring or different terminals. The heavy ion beams are easily lost at the vacuum chamber along the CSRm when it is used to accumulate intermediate charge state particles. The vacuum pressure bump due to the ion-induced desorption in turn leads to an increase in beam loss rate. In order to avoid the complete beam loss, the collimation system is investigated and planned to be installed in the CSRm. First, the beam loss distribution is simulated considering the particle charge exchanged process. Then the collimation efficiency of the lost particles is calculated and optimized under different position and geometry of the collimators and beam emittance and so on. Furthermore, the beam orbit distortion that is caused by different types of errors in the ring will affect the collimation efficiency. The linearized and inhomogeneous equations of particle motion with these errors are derived and solved by an extended transfer matrix method. Actual magnet alignment errors are adopted to investigate the collimation efficiency of the lost particles in the CSRm. Estimation of the beam loss positions and optimization of the collimation system is completed by a newly developed simulation program.

The prototype readout electronics system for the External Target Experiment in CSR of HIRFL

A prototype readout electronics system was designed for the External Target Experiment in the Cooling Storage Ring (CSR) of the Heavy Ion Research Facility in Lanzhou (HIRFL). The kernel parts include the 128-channel 100 ps high-resolution time digitization module, the 16-channel 25 ps high-resolution time and charge measurement module, and the trigger electronics, as well as the clock generation circuits, which are all integrated within the PXI-6U crate. The laboratory test results indicate that a good resolution is achieved, better than the requirement. We also have conducted initial commissioning tests with the detectors to confirm the functions of the system. Through the research of this prototype electronics, preparation for the future extended system is made.