Electron Cyclotron Resonance Ion Source Research Articles

Overall Concept Design of 2.45 GHz ECR Ion Source with Tunable Magnetic Field

The design of the ECR ion source was made for an operating frequency of 2.45 GHz. The ion source is considered to be used for producing protons and double charged helium ions. The source construction as well as the separate components design are presented in the study. The operating modes include both ECR and microwave operating regimes. The extraction system with the beamforming was developed. The beam adjustment is implemented by the longitudinal shifting of the electrodes against the plasma electrode position. The performance of the 2.45 GHz waveguide line to provide the stable power injection into the plasma chamber is considered. The numerical simulation of the waveguide line components was made and optimised.

Bias disk boost technique for pulsed-operation electron cyclotron resonance ion sources

A simple, effective technique to increase the intensity of multiply charged ions has been developed for pulsed-operation electron cyclotron resonance ion sources (ECRISs). The technique is realized simply by applying an additional boost voltage of about −1 kV to a negative constant voltage on the bias disk. The technique can be applied to general ECRISs by adding electric devices to the bias disk circuit, such as a high-voltage power supply, a fast high-voltage switch, and a diode. The effect of the technique depends on the ion species, and we obtained a maximum ion intensity increase of 66% for O6+ compared with the conventional bias disk method. In particular, the technique can be applied to the existing pulsed-operation ECRISs used at a heavy-ion cancer therapy facility where multi-ion treatment with multiply charged oxygen and neon ions is planned to be introduced.

C− generation by charge exchange with non-metallic gas for positive ion mass spectrometry

Carbon positive ion mass spectrometry technology(C-PIMS) is a new type of mass spectrometry technology using the opposite charge exchange process of accelerator mass spectrometry (AMS). There is a plan at Peking University to build 14C-PIMS with the study of a compact 2.45 GHz ECR ion source for C2+ production and a charge exchange cell (CXC) for C2+ to C− conversion. In this paper, the profile of carbon ion source and CXC is introduced and the generation of C− ions is investigated. In experiment, five non-metallic gas targets are tested. 19 μA@90 keV C− beam is obtained from C2+ using the ethylene target. It is found that gas targets with low first ionization energy favor the generation of C−. In addition, the charge exchange efficiency at different beam energies (25 keV–90 keV) is investigated. In terms of theory, the mechanisms of resonant and non-resonant charge exchange processes are introduced to analyze the experimental results. Moreover, the charge exchange from C+ to C− is studied and the feasibility of C+-PIMS is discussed since 2.45 GHz ECR ion source produce more C+ ions. It is found that 139 μA@45 keV C− beam can be obtained from C+ using the methane target.

Demonstration of high-efficiency microwave heating producing record highly charged xenon ion beams with superconducting electron cyclotron resonance ion sources

Intense highly charged ion beam production is essential for high-power heavy ion accelerators. A novel movable Vlasov launcher for superconducting high charge state electron cyclotron resonance ion source has been devised that can affect the microwave power effectiveness by a factor of about 4 in terms of highly charged ion beam production. This approach based on a dedicated microwave launching system instead of the traditional coupling scheme has led to new insight on microwave-plasma interaction. With this new understanding, the world record highly charged xenon ion beam currents have been enhanced by up to a factor of 2, which could directly and significantly enhance the performance of heavy ion accelerators and provide many new research opportunities in nuclear physics, atomic physics, and other disciplines. Published by the American Physical Society 2024

Erratum to: Optimization of Parameters of Hexapole Magnets for Electron Cyclotron Resonance Ion Sources

Erratum to: Optimization of Parameters of Hexapole Magnets for Electron Cyclotron Resonance Ion Sources

Design of the electron cyclotron resonance (ECR) plasma source for the space plasma environment research facility.

The Space Plasma Environment Research Facility (SPERF) was built in Harbin to study the three-dimensional magnetic reconnection and wave-particle interactions relevant to space physics in laboratory settings. A 2.45GHz Electron Cyclotron Resonance (ECR) plasma source is adopted in the device to simulate the Earth's magnetosphere and achieve the scientific goals. In this paper, the design of the ECR plasma source is presented. The structures of the microwave source, the microwave transfer system, and the antenna are introduced. Additionally, the resonant surfaces are computed to predict the locations of microwave absorption. The absorption mechanisms of the microwave in the SPERF are also discussed. The discharge experiment demonstrates the utility of the ECR source in simulating the Earth's magnetosphere. The successful operation of the source indicates that the ECR discharge is a powerful tool for creating a plasma environment in a large plasma experimental device.

Test of High Temperature Superconducting REBCO Coil Assembly for a Multi-Frequency ECR Ion Source

Test of High Temperature Superconducting REBCO Coil Assembly for a Multi-Frequency ECR Ion Source

Progress in the Design of the ASTERICS 28 GHz ECR Ion Source Superconducting Magnet for the NEWGAIN Project at GANIL

Progress in the Design of the ASTERICS 28 GHz ECR Ion Source Superconducting Magnet for the NEWGAIN Project at GANIL

Mechanical Design of the Superconducting Magnet for the 28 GHz ECR Ion Source ASTERICS

Mechanical Design of the Superconducting Magnet for the 28 GHz ECR Ion Source ASTERICS

Phase space reconstruction technique for beam optimization in the Low Energy High Intensity Proton Accelerator (LEHIPA)

The Low Energy High Intensity Proton Accelerator (LEHIPA) has been commissioned to the design energy of 20 MeV at BARC, India. The low energy beam transport (LEBT) channel of LEHIPA consists of two solenoids and drift spaces for matching the 50 keV proton beam from the ECR ion source (ECR-IS) to the RFQ. The ion beam extracted from the ECR-IS also contains molecular species like H2 + and H3 +. Proton fraction in the beam is found to degrade slowly with time due to surface contamination of the plasma chamber and this reduction in proton beam current has implications for longitudinal and transverse beam dynamics. Hence, it becomes important to characterise the beam at different proton fraction levels to understand the end-to-end beam dynamics of LEHIPA. Computed Tomography (CT) technique has been used for the beam phase-space reconstruction in LEHIPA, using a Python program, incorporating the feature of filtering secondary species from the beam profiles measured using slit scanners in the LEBT. Simultaneous Algebraic Reconstruction Technique (SART) is used in the reconstruction since it is identified to be a better technique for a limited number of projections. The reconstruction program is benchmarked with the TraceWin beam dynamics code and implemented on the measured beam profiles to recreate the phase space distribution at the beginning of LEBT. Further, the tomographic reconstruction method is compared with the solenoid scan method and the rms emittance values are found to be in good agreement. The measured tomographic phase space distribution has then been used as TraceWin input for LEHIPA end-end beam dynamics simulations and the LEHIPA beam line parameters are re-optimized for minimum beam emittance growth. This paper presents the simulations of CT technique, benchmarking simulations with TraceWin, phase space reconstruction with measured beam profiles and beam dynamics studies of LEHIPA using the reconstructed beam distributions.

Energy-Resolving Time-of-Flight Mass Spectrometry for Bulk Plasma Analysis.

This work presents a newly designed energy-resolving time-of-flight mass spectrometer (E-TOFMS) for analysing the energy and mass of ions in bulk plasma. The system comprises an electrostatic sector analyser (ESA) for energy-to-charge (E/Q) ratio resolution and an orthogonal reflectron TOFMS for mass-to-charge (m/Q) ratio analysis. The design choices are explained, providing insight into electron and ion path simulations. The instrument was characterised using various ion generation sources, including an electron impact ion source, high power impulse magnetron sputtering, and microwave plasma electron cyclotron resonance sources. To validate its functionality, the energy-resolving data was compared with data obtained under the same conditions using a Langmuir probe and a retarding field energy analyser (RFEA). The benefits of the proposed E-TOFMS were demonstrated by sputtering highly alloyed steel with multiple isotope-rich elements, such as Mo or W. This technique offers an E/Q ratio resolution of up to 0.15 V for a range up to 125 V and a m/Q ratio resolution of at least 700 Th for a range up to 250 Th, with a temporal resolution of 10 μs.

Ion beam stability prediction of ECR ion source based on TCN-DTW network

The Electron Cyclotron Resonance (ECR) ion source is an irreplaceable apparatus for producing high-intensity, highly charged heavy ion beams, representing a critical component for heavy ion accelerators. The operation of the ECR ion source is inherently influenced by various factors, leading to fluctuations in beam intensity. Such instability not only diminishes the efficacy of accelerator operations but also introduces distortions in terminal experimental data. Addressing these challenges, this study proposes the application of a Temporal Convolutional Network (TCN) based on a Dynamic Time Warping (DTW) loss function (TCN-DTW) for predicting the stability of the ion beams. Prior to constructing the prediction network, raw data undergoes preprocessing through an Interquartile Range (IQR) anomaly detection mechanism and the Savitzky-Golay (SG) filtering algorithm with an adaptive window. Experimental results demonstrate a substantial enhancement in prediction performance when employing the TCN network with the DTW loss function compared to traditional alternatives. This approach facilitates effective forecasting of the ion source beam current trend, offering a basis for the control and correction of long-term stability. Consequently, it provides valuable insights for optimizing the ECR ion source and enhancing overall accelerator operational performance.

Optimization of Parameters of Hexapole Magnets for Electron Cyclotron Resonance Ion Sources

Optimization of Parameters of Hexapole Magnets for Electron Cyclotron Resonance Ion Sources

64‐4: ECR Plasma Source for Copper Thin Film Dry Etching

Dry etching process of thin copper films using high electron temperature ECR (electron cyclotron resonance) plasma source is developed. With ECR source and RIE (reactive ion etching) mode, etching rate of 175 nm/min is achieved. Dry etching is performed under high electron temperature plasma source with low temperature substrate and employing a reactive ion etching mode. To compensate the large area etching uniformity, scanning low temperature susceptor is adopted. Rectangular‐type microwave slot antenna (ReSLAN) is used to generate ECR plasma.

Space-resolved electron density and temperature evaluation by x-ray pinhole camera method in an ECR plasma

X-ray emission characterization provides valuable insights about electron cyclotron resonance (ECR) plasmas. In principle, space-resolved spectroscopic techniques can be used to reveal spatial distributions of electron density and temperature. In the PANDORA (Plasma for Astrophysics, Nuclear Decay Observation, and Radiation for Archaeometry) project framework, and within the collaboration between the Atomki and INFN-LNS laboratories, we developed a high-resolution full-field x-ray pinhole setup. This setup incorporates advanced analysis techniques for single photon counted imaging in high dynamical range mode, enabling x-ray imaging and space-resolved spectroscopy at high spatial and energy resolution (560 μm and 242 eV @ 8.1 keV, respectively). Here, we introduce an innovative technique for quantitatively evaluating the local electron density and temperature of plasma, as the first application of such a method in an ECR setup. Specifically, we examine an argon plasma heated by 200 W microwave power at 14 GHz. Our analysis includes a retrospective comparison with past x-ray data collected from other ECR ion source setups. Our findings clearly reveal the formation of a plasmoid–halo structure within the plasma chamber, characterized by a dense and hot plasma almost totally enclosed inside the ECR magnetic iso-surface (the plasmoid). This plasmoid exhibits nearly uniform distribution of electron density and temperature, with only gentle gradients of both the parameters toward its edges. Inside the halo, x-ray emission is minimal or even negligible. Notably, cusp structures correspond to magnetic branches where deconfined electrons impinge upon the plasma chamber walls and endplates. The average values of temperature and density measured inside the plasmoid are 12.44±1.84 keV and (1.66±0.15)×1017 m−3, respectively.

Beam Commissioning of the Heavy-ion Accelerator RAON

RAON (Rare-isotope Accelerator complex for ON-line experiments) is the superconducting linac (SCL3 and SCL2) facility in Korea. It consists of an injector, a superconducting linac, and user facilities. It is designed to accelerate various ion beams from proton (A/Q=1) to uranium (A/Q=7.2). The ECR ion source in the injector system generates ion beams with the energy of 10 keV/u. They are accelerated to the energy of 500 keV/u by the RFQ (Radio-Frequency Quadrupole) in the injector. The superconducting linac (SCL3) includes 22 QWR (Quater-Wave Resonator) cavities and 102 HWR (Half-Wave Resonator) cavities. The energy becomes 18.5 MeV/u for uranium beams after the linac. The beam commissioning of the injector started from August 2021. The first beam commissioning of the superconducting linac was performed from October 2022 to June 2, 2023. Research and development of the cavities for the high-energy part (SCL2) of the superconducting linac is in progress. This work explains some characteristic features of the beam dynamics for RAON linac and some beam commissioning results.

Initial Experimental Results on Ion Cyclotron Resonance Heating Selectively Mixed Low Z Ions to Enhance Production Efficiency of Multicharged Ions on Electron Cyclotron Resonance Ion Source

According to the accessibility conditions of wave propagation in the magnetized plasma of an electron cyclotron resonance (ECR) ion source (ECRIS), it is speculated that the essential factor that determines the limitations in the multiply charged ion currents is the left-hand polarization wave cutoff (L-cutoff). It is necessary to overcome this limitation, we proposed the introduction of ion cyclotron resonance (ICR) or lower hybrid resonance (LHR) by lower frequency waves. We conduct heating low-mass ions selectively in enhanced producing multiply charged ion by mixing low-mass element gas, which has been conventionally performed in ECRIS, or relaxation of the potential well based on the existence of resonant electron particles by ECR. This paper will describe the initial experimental results of ICR application by introducing low-frequency RF electromagnetic waves in the ECRIS.

Initial Experimental Results of Producing Multicharged Ions Efficiently by Lower Hybrid Resonance Heating with Exciting Helicon Waves on Electron Cyclotron Resonance Ion Source

Based on experimental results, we considered the accessibility conditions for wave propagation in the magnetized plasma in an electron cyclotron resonance (ECR) ion source (ECRIS), and proposed introducing electromagnetic waves with frequencies lower than those of ECR. We generate the lower hybrid resonance (LHR) in the ECRIS by the electric field of the extra-ordinary mode (X-mode) on the helicon wave which additionally heat the electrons, and then it was conducted to improve the efficiency of multicharged ion generation successfully in over density condition. The electron energy distribution function obtained by the probe measurement shows an increase in the high-energy region in the corresponding LHR region. In this paper, for the first time we describe the initial experimental results on enhanced production of multicharged ions by the LHR of the low-frequency RF electromagnetic waves into the ECRIS.

Gas mixing and double frequency operation of the permanent magnet quadrupole minimum-B electron cyclotron resonance ion source CUBE-ECRIS

CUBE-ECRIS is a recently commissioned permanent magnet electron cyclotron resonance (ECR) ion source developed at the university of Jyväskylä accelerator laboratory. The special features of the new ion source design include an unconventional quadrupole minimum-B magnetic field structure and a slit beam extraction system necessitated by the line-shaped plasma loss fluxes. Gas mixing and double frequency operation are widely used methods to optimize high charge state ion production of conventional ECR ion sources. The work presented here demonstrates the applicability of these methods for boosting the high charge state beam currents of argon, krypton and xenon extracted from CUBE-ECRIS. Oxygen and helium were used as mixing gases and microwave frequencies between 10 and 11 GHz were used for single and double frequency operation. Gas mixing has a strong impact on the high charge state beam currents. For example, the highest observed charge state increased from 15+ to 19+ for krypton and from 16+ to 23+ for xenon with oxygen gas mixing. Double frequency operation provides an additional performance improvement, for example the currents of argon 9+ and 11+ beams, produced with gas mixing, increased 30% and 100% in double frequency operation at the same total power.

Application of Optical Emission Spectroscopy to Electron Cyclotron Resonance Ion Sources

Electron Cyclotron Resonance Ion Sources (ECRIS) are widely used for production of highly charged high intensity ion beams for research, medical and industrial applications.ECRIS performances, especially the charge state distribution and beam intensity, depend significantly on the electron energy distribution function that ranges from a few eV to hundreds of keV. Further improvements of ECRIS performances require a deeper and deeper understanding of the plasma heating mechanisms and ion generation by means of opportune plasma diagnostics. Amongst others, optical emission spectroscopy (OES) is the most remarkable for application in ECRIS: it is a non-invasive diagnostics able to operate also in high-voltage conditions and it requires small room for operation. OES has been already tested for plasma diagnostics in proton sources.This work presents the experimental set-up developed for the plasma diagnostics of the Advanced Ion Source for Hadrontherapy (AISHa), an ECRIS for medical applications, together with the strategy applied to relate plasma emission lines in the visible and near-infrared domain to plasma parameters for some ions of interest. Preliminary results and perspectives will be also discussed.