Electron Cyclotron Resonance Ion Source Research Articles

Absolute measurement of the relativistic magnetic dipole transition in He-like sulfur

We have made an absolute, reference-free measurement of the $1s2s\phantom{\rule{0.28em}{0ex}}^{3}S_{1}\ensuremath{\rightarrow}1{s}^{2}\phantom{\rule{0.28em}{0ex}}^{1}S_{0}$ relativistic magnetic dipole transition in He-like sulfur. The highly charged sulfur ions were provided by an electron-cyclotron resonance ion source, and the x rays were analyzed with a high-precision double-crystal spectrometer. A transition energy of 2430.3685(97) eV was obtained and is compared to most advanced bound-state quantum electrodynamics calculations, providing an important test of two-electron QED effects and precision atomic structure methods in medium-$Z$ species. Thanks to the extremely narrow natural linewidth of this transition and to the large dispersion of the spectrometer at this energy, a complementary study is also performed to evaluate the impact of different silicon crystal atomic form-factor models in the transition-energy analysis. We find no significant dependence on the model used to determine the transition energy.

Ion source and low energy beam transport prototyping for a single-ended heavy ion ToF-ERDA facility

We present the status of the ion source and low energy beam transport prototyping activities for a heavy ion time-of-flight elastic recoil detection analysis (ToF-ERDA) equipment, designed to accelerate a flux of 1–10 particle nano-Ampere of 40Ar6-12+ ions to 3–6MeV energy for depth profiling of light elements. The prototype injector consists of a novel permanent magnet electron cyclotron resonance ion source CUBE-ECRIS with a minimum-B quadrupole field topology, and a 90° permanent magnet dipole with adjustable field strength for charge state selection. We report experimentally measured argon beam currents as a function of the applied microwave power and ion source potential to demonstrate the feasibility of the CUBE-ECRIS as an injector for a single-ended ToF-ERDA facility with the ion source and low energy beam transport on a 500kV platform without SF6 electrical insulation. Finally, we present the design and field measurement results of the dipole magnet prototype.

Design and Development of the 200-kW Beam Dump

The Chinese Accelerator Front end (CAFe) is a demo superconducting proton linac for an accelerator-driven subcritical system (ADS). It includes an electron-cyclotron resonance ion source, a low-energy transport line, a radio-frequency quadrupole, a medium-energy transport line, a superconducting section, a high-energy transport line, and a beam dump. The design energy and current are 20 MeV and 10 mA, with a beam power of 200 kW. The goal of the CAFe is to demonstrate the 10-mA ability of a full superconducting linac, especially in the low-energy region. In previous beam commissioning, the maximum beam power achieved was 34 kW, which was limited by the capacity of the beam dump. Thus, for the high-power beam commissioning of CAFe, a new 200-kW beam dump has been designed and developed. Based on the thermal analysis, a maximum power density of 200 W/cm2 is adopted for the dump. To avoid a high-level residual dose, the material of the dump is aluminum alloy (Al6063). The dump is a conical structure, with water flow in the interlayer. During beam commissioning, the dump withstood 200-kW proton beam power and collected a total charge of 2049 mAh.

Commissioning Results of the New Compact ECR Ion Source for Electrostatic Storage Ring at KACST

A compact microwave ECR ion source with low operating power was tested and commissioned for the ion injector line in the multipurpose low-energy ELASR storage ring facility at King Abdulaziz City for Science and Technology (KACST) in Riyadh. The compact ECR ion source can deliver singly charged ions with an energy of up to 50 keV and a beam current of up to 50 μA or up to 500 µA with a larger extraction aperture. The plasma in the ECR chamber is driven by a simple transmitter antenna, making the overall size of the ion source only 6 cm in diameter, which is relatively small when compared with other ECR systems. Additionally, the source operates without a high-voltage platform, which significantly reduces the overall footprint and simplifies the system operation. In this paper, the mechanical design and modeling of the ECR ion source are introduced, and the layout of the first part of the beam line is presented along with the numerical simulation results. In addition, the experimental results obtained for the first generated ion beam and commissioning of the ECR ion source are introduced and discussed.

Kinetic whistler instability in a mirror-confined plasma of a continuous ECR ion source

Kinetic instabilities in a dense plasma of a continuous electron cyclotron resonance (ECR) discharge in a mirror magnetic trap at the Gasdynamic Ion Source for Multipurpose Operation (GISMO) setup are studied. We experimentally define unstable regimes and corresponding plasma parameters, where the excitation of electromagnetic emission is observed, accompanied by the precipitation of energetic electrons from the magnetic trap. A comprehensive experimental study of the precipitating electron energy distribution and plasma electromagnetic emission spectra, together with theoretical estimates of the cyclotron instability increment proves that under the experimental conditions, the observed instability is related to the excitation of whistler-mode waves, which are a driver of losses of energetic electrons from the magnetic trap. The results of this study are important for the further development of the GISMO electron cyclotron resonance ion source facility and for the improvement of its parameters as an ion source. Also, this research on plasma kinetic instabilities is of fundamental interest and provides experimental tools to simultaneously study plasma electromagnetic activity and corresponding changes in a resonant electron energy distribution.

Iodine electron cyclotron resonance plasma source for electric propulsion

With the rapid development of commercial space in recent years, the low-power and low-cost propulsion systems are needed more and more urgently. Compared with conventional chemical propulsion, electric propulsion has a higher specific impulse. Compared with the conventional xenon propellant, iodine propellant that does not require high pressure storage, is cheap and close to the relative atomic mass and ionization energy of xenon. Electron cyclotron resonance source has the advantages of no internal electrode, low pressure ionization, high plasma density and compact structure, which is suitable for low power electric propulsion. Therefore, the study of low power iodine propellant electron cyclotron resonance plasma source is of great significance. In this study, a set of corrosion-resistant feed system with balanced and stable output of iodine vapor is designed. Then the iodine-corrosion-resistant electron cyclotron resonance thruster is designed completely. A corrosion-resistant coaxial cavity structure is used to feed the microwave to the thruster, and the channel magnetic field is changed into a cusped field to generate more electron cyclotron resonance (ECR) layers. Finally, the combined ignition experiment is successfully conducted, showing the first plasma source using electron cyclotron resonance to ionize iodine propellant that can be used for electric propulsion in the world. The analyses of experiments, static magnetic field, microwave electric field distribution show that the unstable plasma plume scintillation at low power and low flow is caused by the conversion between ordinary wave electron plasmon resonance heating mode and extraordinary wave electron cyclotron resonance heating mode. The decrease of ionization rate at a high flow rate is caused by electron loss, wall loss and electronegativity of iodine propellant. Based on this principle, an improvement scheme is proposed. The plasma source has no obvious damage after discharge, which indicates that it has the potential of long life. This work preliminarily proves that the low power electron cyclotron resonance electric propulsion scheme of low power iodine propellant is feasible.

Overview of Numerical Simulations for Calculating In-Plasma β-Decay Rates in the Framework of PANDORA Project

β-decay rates are essential inputs in stellar nucleosynthesis models to explain observed nuclear abundances. While current models continue to use terrestrial values, experiments in storage rings indicate strong divergence between decay rates of neutral and ionised atoms [1], necessitating renewed investigations into stellar decay rates. The PANDORA project aims at measuring lifetimes of specific radio-isotopes trapped in an ECR plasma (which mimics astrophysical environments to some extent) and compare them with theoretical predictions [2], consequently verifying the models and allowing decay rate estimation for any isotope in the stellar interior. We present here a simulation scheme to characterise the space-resolved charge state and level population distribution of buffer and radio-isotope ions in ECR ion sources in order to calculate in-plasma decay rates. The algorithm is based on a Particle-in-Cell Monte Carlo (PIC-MC) routine that simultaneously models charge transport with collision-radiative processes. Preliminary results from the simulation are also shown, along with important takeaways for code-optimisation.

A newly developed ECR ion source with wide dynamic range of beam current

A newly developed ECR ion source with wide dynamic range of beam current

First results of a new quadrupole minimum-B permanent magnet electron cyclotron resonance ion source

The first experimental results of a novel permanent magnet electron cyclotron resonance ion source (ECRIS) with a minimum-B quadrupole magnetic field topology are presented. Bremsstrahlung measurements indicate that the electrons can reach energies of 150–200 keV. Ion charge states up to Ar11+ and Kr15+ were detected in the charge state distributions of the extracted beams. Measurements in pulsed operation mode reveal an afterglow peak, which implies that high charge state ions are confined electrostatically similar to a conventional ECRIS. The potential applications and future development of the ion source are discussed.

The capture of injected 1+ ions in charge breeder electron cyclotron resonance ion source plasma

The capture process of the 1+ ions in charge breeder electron cyclotron resonance ion sources has been attributed to cumulative small-angle scattering of the incident ions in ion–ion collisions with the buffer gas ions. The model results in controversy between the plasma potential and ion temperature values derived from simulations, and those found in the experiments. We demonstrate that the 1+ ion capture process is dominated by the slowing down of the incident ions by the ambipolar plasma potential, which has previously been assigned with a secondary importance. In this revised view, supported by experimental data, the 1+ capture does not depend on the mass of the injected and plasma ion species, or the ion temperature, which resolves the disagreement between modelling and experiments.

An extraction system design with a strongly inhomogeneous electric field for a JYFL electron cyclotron resonance ion source

A new ECR ion source extraction system has been designed. The design is based on the extraction conditions of the JYFL 14 GHz ECRIS, and its performance is compared to the existing extractor via numerical modeling. The aim is to improve the formation and quality of high-intensity ion beams. The plasma and the puller electrodes shape were changed. The plasma electrode has a narrow tip extruding toward the puller. It causes the electric field to increase near the plasma meniscus and subsequent higher ion velocity growth rate, which leads to the beam space charge reduction at fixed current and acceleration voltage. The extractor was developed with the ion optical code IBSimu. The initial beam parameters were taken from the experimental data. The calculations showed that the new extraction system allows to increase the total extracted current without compromising the beam quality. The new design allows the beam formation optimization for lower extraction voltages overcoming the present space charge limit.

Optimization of an Ecr Ion Source Beam Extraction and Formation System

Optimization of an Ecr Ion Source Beam Extraction and Formation System

LEBT Development for High-Current Multicharged Ion Injector Based on SC ECR Ion Source

LEBT Development for High-Current Multicharged Ion Injector Based on SC ECR Ion Source

Simulation as a Tool for Understanding Experimental Observations—Ion Beam Extraction from an ECRIS

A model for the simulation of ion beam extraction from an electron-cyclotron resonance ion source is proposed. It is based on the simple fact that charged particles follow magnetic field lines. Therefore, magnetic field lines are used to generate initial conditions for ray-tracing. This model reproduces in simulation experimentally obtained results. The importance of correlations in phase-space caused by the magnetic field is shown in the simulation. This model also describes the physics of space-charge and its compensation in the extracted (fast) ion beam by low-energy electrons. Simulation provides the possibility to test theoretical assumptions, as well as to optimize technical designs.

Diagnostics of highly charged plasmas with multicomponent 1+ ion injection.

We establish multicomponent 1+ injection into a charge breeder electron cyclotron resonance ion source and an associated computational procedure as a noninvasive probe of the electron density n_{e}, average electron energy 〈E_{e}〉, and the characteristic times of ionization, charge exchange, and ion confinement of stochastically heated, highly charged plasma. Multicomponent injection allows refining the n_{e}, 〈E_{e}〉 ranges, reducing experimental uncertainty. Na/K injection is presented as a demonstration. The 〈E_{e}〉 and n_{e} of a hydrogen discharge are found to be 600_{-300}^{+600}eV and 8_{-3}^{+8}×10^{11}cm^{-3}, respectively. The ionization, charge exchange, and confinement times of high charge state alkali ions are on the order of 1 ms-10 ms.

Studies of pure and nitrogen gas mixed xenon ECR plasma: Signature of abundance dependent unusual trends in isotope anomaly.

We report the effect of N2 gas-mixing in the xenon electron cyclotron resonance (ECR) plasma, and abundance-dependent novel, exciting and unusual trends of the isotope anomaly. The xenon plasma was produced using a 10 GHz all-permanent-magnet NANOGAN ECR ion source, and the charge state distributions of naturally abundant six stable xenon isotopes with and without N2 gas-mixing (at 25%, 50%, and 75%) were recorded. The intensity ratio of the heavier to lighter isotope, where the heavier isotope is less abundant, showed a clear signature of the isotope anomaly as explained by the linear Landau wave damping theory. Contrary to the theoretical prediction that the isotope anomaly should vanish with a relatively large fraction of the heavier isotope in mixed plasmas, the trends of intensity ratios observed in such cases are very unusual and have almost the mirror-symmetrical shapes of those trends recorded with less abundant heavier isotope. Further, the effect of relative mass difference on the isotope anomaly was also evidenced. The N2 gas-mixing of the xenon plasma at 25% and 50% shifted the entire charge state distribution toward the higher intensity side owing to the supply of additional electrons that caused high ionization efficiency. However, a prominent gas-mixing effect was observed at 75% of N2 mixing in the xenon plasma beyond the +7 charge state. The abundance-dependent unusual trends in isotope anomaly have been explained by considering different ionic temperatures, ion heating by the wave damping, and Coulomb scattering in the core of the plasma.

Plasma characterization in CW and pulsed mode and its effect on beam current in 2.45 GHz ECR Ion source

Electron Cyclotron Resonance Ion Source (ECRIS) is used as a front end for Low Energy High Intensity Proton Accelerator (LEHIPA) at BARC. A 50 keV ECRIS is designed and developed for the proton ion beam for this accelerator. The key requirements of the ion source are beam current ∼ 10 – 15 mA and beam emittance ∼ 0.2 π mm-mrad. In the commissioning phase of LEHIPA, the ion source is operated in pulsed mode to mitigate the effect of thermal and radiation load. Measurements have been carried out to understand the behavior of pulsed plasma and its effect on ion beam. An Automated Langmuir Probe (ALP) and its associated circuit are designed and developed for this purpose. The ALP circuit consists of a voltage sweep generator, current sense circuit, and voltage sense circuit. The effect of microwave power and pulsed plasma duration on the plasma and the ion beam parameters have been studied. The plasma parameters are correlated with the beam parameters.

Shell-Based Support Structure for the 45 GHz ECR Ion Source MARS-D

Superconducting electron cyclotron resonance ion sources (ECRISs) using NbTi coils and optimized for 28 GHz resonant heating have been successfully operated for almost two decades. Moving to higher heating frequencies requires increased magnetic fields, but traditional racetrack-and-solenoid ECRIS structures are at their limit using NbTi. Rather than moving to a superconductor untested in this field, the Mixed Axial and Radial field System (MARS) being developed at Lawrence Berkeley National Laboratory employs a novel closed-loop-coil design that more efficiently utilizes conductor fields and will allow the use of NbTi in a next-generation, 45 GHz ECRIS. This article presents the design of the shell-based support structure central to the MARS-D magnet design, as well as structural analysis of its components and optimization of pre-load parameters that will guarantee its successful operation.

Mechanical Analysis and Validation of the Prototype of Nb3Sn Superconducting Magnet Structure With Dummy Coils for FECR Ion Source

The Fourth-generation Electron Cyclotron Resonance (ECR) ion source (FECR) Nb <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> Sn superconducting magnet is being developed by Institute of Modern Physics (IMP), Chinese Academy of Sciences. In order to reduce the risk of development and address key technical challenges, a half-length prototype is designed. The prototype consists of six sextupole coils and two solenoid coils. To validate the assembly and loading procedures, the structure was assembled with dummy sextupole coils (Al 6061 cylinder) and dummy solenoid coils (extend solenoid stainless-steel formers) that replaced the brittle Nb <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> Sn coils, then cooled-down to 77 K with liquid nitrogen and warmed up. The dummy coils are different from Nb <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> Sn coils, the mechanical behavior of the structure in each step is analyzed with finite element software ANSYS. The numerical analysis model must be cross-checked with the tests and validate it. The evolution of the mechanical behavior was monitored via strain gauges located on different components of the structure (Al shell, dummy sextupole coils, and axial rods). We focus on the expected stresses within the structure after assembly and pre-loading, cool down, warm up and thermal cycle. The expected stresses were determined from the 3D finite element model (FEM) of the structure. Some low-temperature strain gauges, were used to monitor strain of the structure during the pre-load control performance and thermal cycle process. A comparison of the 3D model strain/stress predictions with the strain gauge data measurements is made. The coherence between the predicted contact pressure/strain/stresses with Fuji paper and the experimental gauge measurements will validate the FEM model of the structure. Once robust finite element analysis (FEA) numerical results are available, we can estimate and improve the final results of the real assembly with Nb <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> Sn coils. So as to realize the stress management of the magnet.

Superconducting Magnet Development for the HIAF Accelerator Complex

The High Intensity Heavy-ion Accelerator Facility (HIAF) is a new project under construction in China, which will provide beams of stable and unstable heavy ions with high energies, high intensities, and high quality. This paper discusses the superconducting magnet system for this accelerator complex. It will consist of a Nb <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> Sn magnet with the peak field of 12 Tesla for the ECR ion source operated at 45 GHz, 52 solenoids typically 676 mm long with an operating field of 7.5 Tesla for the superconducting Linac called iLinac, 11 superferric dipoles with 320 mm wide good field region, 13 coil-dominated multiplets with an aperture of 320 mm, gradient 13 T/m for the fragment separator HFRS. This paper reports the design and prototype development status of the main components.