Abstract Gasdynamic ion sources are capable of producing high current ion beams with low-to-medium charge states. It is proposed to pre-accelerate tens of emA ion beams with low-to-medium charge states produced by a gasdynamic ion source, and then to strip them to high charge states to meet the increasing requirements of advanced heavy ion accelerators for high-intensity ion beams. As the first step to investigate this scheme, a 45 GHz gasdynamic ion source which operates in pulsed mode has been developed. It’s first ion beams with the intensity of several hundred mA/cm 2 have been extracted, which demonstrates its potential of intensive beam formation. The electron temperature and density were diagnosed with the measurements of the leaking electron current and the line intensity ratios of EUV spectra.

To investigate the radiation resistance of multilayer graphite (MLG) prepared by the methods of vacuum-assisted self-assembly (VASA) and graphitization of polyimide (PI), irradiation experiments were carried out using 3.9 MeV/u Xe ion beams at fluences up to 1 & times; 1015 ions/cm2, comparing with graphene oxide (GO) and diamondlike carbon (DLC). These materials are potential candidates for charge stripping in modern accelerators, where they must withstand increased beam intensities and provide reasonable service time. Characterization was carried out, including scanning electron microscopy to study surface morphologies, confocal Raman spectroscopy for bonding structures, X-ray photoelectron spectroscopy and X-ray diffraction for crystal structures. Additionally, high-resolution transmission electron microscopy was used to analyse crystallinity and micromorphology, tensile testing for mechanical properties, and laser flash analysis for thermal diffusivity. The MLG foils exhibit negligible change in D-peak intensity, indicating preservation of the graphite structure, with the graphitization degree remaining above 90% after irradiation. These foils also exhibit "ruck and tuck" defects and larger crystallites after irradiation, indicating exceptional radiation resistance relative to the GO and DLC foils. Furthermore, the much higher values of the elongation at break and in-plane thermal diffusivity of the MLG foils explain their superior radiation hardness from the perspective of macroscopic properties.

In the high-energy mode of Booster Ring (BRing) of the High Intensity heavy-ion Accelerator Facility (HIAF), the pre-accelerated ions from the iLinac will be stripped by a carbon foil to higher charge states and then injected into the BRing. The thermal deposition and irradiation damage caused by high beam intensity and high energy deposition limit the lifetime of the foil. To ensure the stable operation of HIAF, a long-lifetime stripper foil with excellent irradiation and high-temperature resistance is required. This report aims to reveal the irradiation damage evolution of several kinds of carbon foils and its impact on their physical properties. Irradiation experiments were performed at HIRFL-SFC using Xe beams with the energy loss close to that of U beams in HIAF. There were three kinds of foils from four producer irradiated in the experiments, including Multilayer graphene (MLG) produced by KANEKA Co. and the Institute of Coal Chemistry (SXICC), diamond-like carbon (DLC) foil by the Institiute of Modern Physics (IMP) and Graphene Oxide (GO) foil by TIMESNANO Co. Various characterization methods were used to study the changes in surface morphologies, microstructures, and physical properties of the foils. The results indicated that MLG has a tendency for amorphization, DLC has a tendency for graphitization, and the oxygen-containing functional groups on the GO surface are damaged. These structural changes are expected to significantly impact the mechanical properties of the foils.

The characteristics of laser-produced metal hydride plasmas have been investigated in this work. The charge state and velocity of ions were determined by employing a time-of-flight technique in conjunction with an electrostatic deflection method. The ion velocities were found to be supersonic with values in the range of 104 to 105 m/s. The proportion of hydrogen ions was found to be lower than that of titanium ions. The ion emission behavior was studied by using a Faraday cup. When the total integrated space was taken into account, the ns pulsed laser was capable of producing hydrogen ion currents greater than one hundred mA. In order to understand the plasma generation process, we performed a comparative analysis between laser-generated plasma and arc plasma, and also investigated the effect of laser power density on the composition and velocity of the ions, the ablation properties of metal hydrides, and the maintainability of hydrogen ion emission.

Charge strippers play an essential role in heavy-ion accelerators by stripping the projectile ions to higher charge states to enhance the acceleration efficiency downstream of the stripper. In the high-energy mode of the booster ring (BRing) of the high-intensity heavy-ion accelerator facility, the pre-accelerated ions from the iLinac will be stripped by a carbon foil to higher charge states and then injected into the BRing. The key parameters of the stripper and stripped ions were calculated, and the influence of stripping on the beam quality was discussed. To get high stripping efficiencies, the foil thicknesses and resultant charge state distributions for the typical ions were determined by the code ETACHA. The equilibrium thickness was obtained for the U beam, while the stripper thicknesses for the Xe and Kr beams were determined based on a compromise between the stripped charge states and the stripping efficiency. The energy loss, energy straggling, and emittance growth due to stripping have a non-negligible impact on the transport of the stripped beams and the injection of the ring. Therefore, these parameters were simulated by GEANT4. In addition, the foil’s temperature evolution, which greatly affects the foil lifetime, was simulated by ANSYS. The maximum temperature of the foil bombarded by the U and Xe beams with the nominal parameters will exceed the safe value in terms of the impact of evaporation on the foil’s lifetime. Given the foil temperature constraint, the highest tolerable beam intensity and the injected ion number into the ring were derived for different beam sizes. The results of this paper will present important reference data for the optimization design and commissioning of the beamline and injection to the BRing for the stripped ions.

Based on KONUS dynamics,the beam dynamic design of a compact IH-DTL with built-in permanent magnet quadrupole lens was completed.The DTL consists 37 acceleration cells and two sets of permanent magnet quadrupole lenses,enabling the acceleration of C6+ion beam of 20 emA from 0.5 MeV/u to 4.0 MeV/u.Throughout the design process,signific-ant focus was placed on optimizing the voltage of the acceleration gap,the parameters of the quadrupole magnet,the phase set-ting of the beam injection,and the energy and phase setting of the 0-degree reference particle to control the transverse and lon-gitudinal emittance growth of the high-current ion beam in the low-energy range.Consequently,transverse normalized RMS acceptance of the IH-DTL reaches 0.37 πmm·mrad,and the transmission efficiency exceeds 95％.

The super τ-charm facility (STCF) is an electron–positron collider proposed by the Chinese particle physics community. It is designed to operate in a center-of-mass energy range from 2 to 7 GeV with a peak luminosity of 0.5 × 1035 cm−2·s−1 or higher. The STCF will produce a data sample about a factor of 100 larger than that of the present τ-charm factory — the BEPCII, providing a unique platform for exploring the asymmetry of matter-antimatter (charge-parity violation), in-depth studies of the internal structure of hadrons and the nature of non-perturbative strong interactions, as well as searching for exotic hadrons and physics beyond the Standard Model. The STCF project in China is under development with an extensive R D program. This document presents the physics opportunities at the STCF, describes conceptual designs of the STCF detector system, and discusses future plans for detector R D and physics case studies.

The C-12+C-12 fusion reaction was studied in the range of E-c.m.=8.9 to 21 MeV using the active-target Time Projection Chamber. With full information on all tracks of the reaction products, cross sections of the C-12(C-12, Be-8)O-16(g.s.) channel and the C-12(C-12, 3 alpha)C-12 channel could be measured down to the level of a few milibarns. The C-12(C-12, Be-8)O-16(g.s.) reaction channel was determined to be 10(-8)(+24) mb at E-c.m. = 11.1 MeV, supporting the direct alpha transfer reaction mechanism. The C-12(C-12, 3 alpha)C-12 reaction channel was studied for the first time using an exclusive measurement. Our result does not confirm the anomaly behavior reported in the previous inclusive measurement by Kolata et al. [Phys. Rev. C 21, 579 (1980)]. Our comparisons with statistical model calculations suggest that the 3 alpha channel is dominated by the fusion evaporation process at E-c.m. > 19 MeV. The additional contribution of the 3 alpha channel increases the fusion reaction cross section by 10% at energies above 20 MeV. We also find that an additional reaction mechanism is needed to explain the measured cross section at E-c.m. < 15 MeV at which point the statistical model prediction vanishes.

Laser ablation plasma(LAP) can be used as an ion source for particle accelerators and for ion implantation. Although the too intensive current intensity of laser ion sources give them advantages over other ion sources, yet the minute duration of laser produced ion pulses limits their applications in accelerators. By introducing a solenoid into the plasma expansion region, the modulation of the plasma temporal structure had been achieved[ 1 - 3 ]. In order to study the effect of solenoid magnetic field on LAP, we used different laser energies (1~8 J) to produce LAP at different initial conditions and applied various magnetic field strengths to confine the plasma. The transverse distribution of the laser produced ions were measured with a movable faraday cup (FC) at the edge of the fringe field of the solenoid. The main parameters of the ion pulses, the total charge, the peak current, and the pulse duration, enhanced at first and then got saturated with the increasing magnetic field, no matter what the initial plasma conditions were. Unlike the nearly uniform transverse distribution of the plasma without magnetic confinement, the plasma got concentrated when the magnetic field was applied. The experimental results presented and discussed in the present work are of great significance for further understanding the characteristics of magnetically confined LAP.

In order to diagnose the electron cyclotron resonance (ECR) plasma, a high-efficiency collimation system has been developed at the Institute of Modern Physics, and the bremsstrahlung spectra in the range of 10 keV-300 keV were measured on a third generation superconducting ECR ion source, SECRAL-II, with a CdTe detector. Used as a comparative index of the mean energy of the high energy electron population, the spectral temperature, Ts, is derived through a linear fitting of the spectra in a semi-logarithmic representation. The influences of some main source parameters, such as the neutral gas pressure, extraction voltage, microwave power, and bias disk voltage, on the high energy electrons are systemically investigated.

Ion source development over the last 20 years at the IMP is reviewed. For versatile purposes, several types of ion sources have been involved in the research and development work at the IMP, i.e., the highly charged ECR (Electron Cyclotron Resonance) ion source, intense microwave ion source or the 2.45 GHz intense beam ECR ion source, and laser ion source (LIS). In the development of ECR ion sources, SECRAL (Superconducting ECR ion source with Advanced design in Lanzhou), Lanzhou ECR ion source, and Lanzhou all permanent magnet ECR ion source series have been made, which can cover the operation microwave frequency range of 10-28 GHz. The LIS with an Nd:YAG laser with a maximum output energy of 8 J in 8 ns pulse duration has been developed for very intense short pulse ion beams from solid materials such as C, Ti, Ni, Ag, and so on. Microwave ion sources have been built to produce intense pulsed or direct current beams from several mA to 100 mA for either high intensity accelerators or applications. This paper will give an overview of the high intensity ion source development at the IMP, especially on the recent progress and new results, such as the status of the fourth generation ECR ion source (first fourth generation ECR ion source), the production of recorded highly charged ion beams with SECRAL sources, key technology research studies, and so on.

Laser-produced plasmas (LPP) have been known to possess great application potential under extreme ultraviolet (EUV) lithography, soft X-ray micrography, and heavy ion accelerator, highly charged ion optical frequency standards, pulsed laser deposition, astrophysics and nuclear fusion. The applications in these fields require a clearer understanding of the evolutionary behavior of the LPP. However, LPP is neither homogeneous nor static during their expanding and cooling process, which involves complex physical processes. For a deep understanding of the LPP, many diagnostic methods and techniques have been developed, such as spectroscopy, fast imaging, time-of-flight (TOF), laser interferometry and Thomson scattering. Among these methods, spectroscopy has been the most widely used diagnostic method, which can be used to obtain relatively more state information. However, the diagnosis results of charge-state distribution obtained by spatio-temporally resolved spectroscopy are local and transient, and cannot therefore obtain the overall distribution. In order to have a more comprehensive understanding of charge-state distribution and its evolutionary behavior of the LPP, other diagnostic methods are needed. The TOF method is used for the measurement of highly charged ions of the LPP, which can be used to obtain the overall charge-state distribution information. Therefore, in this work, spectrometry and TOF method were used for the diagnosis of charge-state distribution of the LPP in a vacuum. The EUV emission spectra of laser-produced Al plasmas were measured by using spatio-temporally resolved laser-produced plasmas spectroscopy technique. The charge-state distributions with different delay times at the distance of 2.0 mm from target surface were diagnosed by spectral simulation and their evolution behavior were also analyzed. The TOF spectra of laser-produced Al plasmas were measured by the TOF method, and the overall charge-state distribution of ions in laser-produced Al plasmas was obtained. The results revealed that spectroscopy can diagnose the local and transient charge-state distribution of ions in the laser-produced plasmas, and the TOF method can be used to diagnose its overall distribution, and the two diagnostic methods therefore complement each other. This work aims to clarify the complementarity of the two methods, and to provide a method support for the comprehensive and accurate understanding of the charge-state distribution and evolution evolutionary behavior during the expansion process of the LPP, and also provides a reference for further optimization and modification of the radiation hydrodynamics model of the LPP.

The Ion Source Group at IMP has been undertaking a series of high intensity ion beam R&D projects. The first project is the development of the intense proton source and its low energy beam transport system (LEBT) for China Initiative Accelerator Driven Sub-Critical reactor (CiADS). The specific characteristics of the proton source are long-term reliability and flexible beam manipulation for the commissioning need of the Superconducting radio-frequency (SRF) accelerators. The LEBT is used to deliver 35 keV H+ beam to the entrance of a 2.1 MeV RFQ. And then the 2.1 MeV proton beam is further accelerated by the superconducting cavities to 25 MeV and eventually goes into a high power beam dumper. Another project is the development of the intense ion source for Jinping Underground Nuclear Astrophysics experiments (JUNA). The ion source was expected to provide 10 emA H+, 10 emA He+ or 2.5 emA He2+ beams for the study of (p, gamma), (p, alpha), (alpha, p) and (alpha, gamma) reactions in the first phase of the JUNA project. The main challenges of the ion source for JUNA project are production of intense He2+ beam, control of the beam contaminations and beam commissioning a wide beam energy range (70 similar to 800 keV). In this paper, the studies of these intense beam injector systems, for instance, beam intensities, species and ratio, beam transmission efficiency in the LEBT and also the beam optics matching to the downstream accelerator systems will be presented.

The injection of the electron beam into the ECR (Electron Cyclotron Resonance)plasma by electron gun is a new method for the additional supplementary of the plasma electron, following the aluminum chamber wall and the bias plate, we are expecting for the higher current and charge state of the ion beam with it. However, because of the controllable parameter's variety, the lack of the accumulation of experience and data, and the shortage of convenience in designing and experimental practicing compared by biased disk and other means,it has always not been intensively studied. In this article, we take the 18 GHz ECR Ion Source using evaporative cooling technique as experimental platform, do the experiment of injecting electron into ECR plasma base on the simulation result of the electron beam's path in ECR's chamber by the 3D simulation software CST the particle studio. It shows that a pulsing leap of the current of the extracting ion beam appears when the injecting electron's energy is above 1800 eV. In the mean time, the top of the pulse and the average current of the ion beam rises, the ionization state moves to a higher level. This phenomenon can be turned on and off by controlling the experimental condition. At the last part of the article, we discuss this improvement of the current and charge state of the ion beam despite of the position's missing between the injection of electron beam and the resonance surface, and hold the opinion that this phenomenon is positive to both pulsed and direct beam.

The exploration of the unique properties of stored and cooled beams of highly-charged ions as provided by heavy-ion storage rings has opened novel and fascinating research opportunities in the realm of atomic and nuclear physics research. Since the late 1980s, pioneering work has been performed at the CRYRING at Stockholm (Abrahamsson et al. 1993) and at the Test Storage Ring (TSR) at Heidelberg (Baumann et al. 1988). For the heaviest ions in the highest charge-states, a real quantum jump was achieved in the early 1990s by the commissioning of the Experimental Storage Ring (ESR) at GSI Helmholtzzentrum für Schwerionenforschung (GSI) in Darmstadt (Franzke 1987) where challenging experiments on the electron dynamics in the strong field regime as well as nuclear physics studies on exotic nuclei and at the borderline to atomic physics were performed. Meanwhile also at Lanzhou a heavy-ion storage ring has been taken in operation, exploiting the unique research opportunities in particular for medium-heavy ions and exotic nuclei (Xia et al. 2002).

An accelerator with low injection energy has been designed and constructed based on direct plasma injection scheme (DPIS); a pulsed C6+ beam with peak current of 11.28 mA, energy of 593 keV/u has been successfully achieved after accelerated with DPIS method. It is because that the beam produced by laser ion source is a pulsed one with large energy spread, high intensity and the design of a low energy transport line (LEBT) is also complicated, while the DPIS method is simple to achieve and improve the injection e?ciency effectively;so, the laser ion source is directly connected to the RFQ without a LEBT in this equipment and then the laser produced plasma will be injected into RFQ with DPIS. In addition, the DPIS method is simulated by IGUN code and the parameters of extracted beam and its injection e?ciency are obtained from simulation, which is well agreed with the measured one in our experiment.

A hybrid single cavity (HSC) linac, combined with radio frequency quadrupole and drift tube structure in a single interdigital-H cavity, operates with high rf power as a prototype injector for cancer therapy synchrotron. The HSC adopts a direct plasma injection scheme (DPIS) with a laser ion source. The input beam current of the HSC is designed to be 20 mA ${\mathrm{C}}^{6+}$ ions. According to simulations, the HSC can accelerate a 6-mA ${\mathrm{C}}^{6+}$ beam which meets the requirement of the particle number for cancer therapy ($1{0}^{8\ensuremath{\sim}9}\text{ }\text{ions}/\text{pulse}$). The HSC injector with DPIS makes the existing multiturn injection system and stripping system unnecessary; what is more, it can also bring down the size of the beam pipe in existing synchrotron magnets, which can reduce the whole cost of the synchrotron. Details of the field measurements of the HSC linac and results of the high power test are reported in this paper.

A double-pulse laser irradiating scheme has been designed and established for the production of highly charged ion beams at Institute of Modern Physics (IMP), Chinese Academy of Sciences. The laser beam output by a Nd:YAG laser is split and combined by a double of beam splitters, between which the split laser beams are transmitted along different optical paths to get certain time delay between each other. With the help of a quarter-wave plate before the first splitter, the energy ratio between the two laser pulses can be adjusted between 3:8 to 8:3. To testify its feasibility, a preliminary experiment was carried out with the new-developed double-pulse irradiating scheme to produce highly charged carbon ions. Comparing the results with those got from the previous single-pulse irradiating scheme, the differences in the time structure and Charge State Distribution (CSD) of the ion pulse were observed, but its mechanisms and optimization require further studies.

A novel hybrid single cavity (HSC) linac, formed by combining a radio frequency quadrupole (RFQ) structure and a drift tube (DT) structure into one interdigital-H (IH) cavity, was fabricated, assembled and tested as a proof of principle type injector for cancer therapy synchrotron. The HSC linac is a power-efficient cavity. The low power test and the high power acceleration test were carried out. The low power test results are in good agreement with the calculation results. The high power test results show that the HSC linac can meet the high power test in the next step. ©, 2015, Atomic Energy Press. All right reserved.(5 refs)

In this paper, we report on measurements of bremsstrahlung in laser ion acceleration experiments from ultra-thin, polymer-based target foils. The influence of laser polarization on the generated \(\gamma\) radiation, the maximum achievable proton energy and the total proton number is investigated. A clear benefit in terms of \(\gamma\) radiation reduction by the use of circular polarized light can be observed. At the same time, the total number of accelerated protons was increased.