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In this article, we present a multi-fluid numerical model developed for application on electron cyclotron resonance ion sources (ECRIS). The 1D-model is matured to compute the density of the ion species in the plasma sheath in the presence of an inhomogeneous magnetic field of a 2.45 GHz ECRIS. The multi-fluid model in cylindrical coordinates is focused on solving the continuity and momentum equations of hydrogen plasma particles to characterize their sheath properties. In addition, 28 important processes, including volume and surface collisions, have been included in the COMSOL Multiphysics package to simulate the ECR plasma. We study the elementary processes containing electron–atom, electron–molecule, atom–molecule, molecule–molecule, and particle–wall interactions. Then, the results of the model and the simulation of a 2D-hydrogen plasma are reported, and future perspectives are discussed throughout the paper. [ABSTRACT FROM AUTHOR]

Measurement of angular distribution (AD) of the bremsstrahlung spectral temperature from a full dimension of the Electron Cyclotron Resonance Ion Source (ECRIS) along the beam axis is challenging. To overcome some challenges, this paper presents the AD of the bremsstrahlung spectral temperature measured in a full dimension of the ECRIS along the beam axis using data obtained from the Busan Center of Korea Basic Science Institute (KBSI). The bremsstrahlung spectral temperature from 28-GHz ECR Ion source at the KBSI was measured in six, three, and nine azimuthal angles at the injection, centre, and extraction sides of the ECRIS using three round type thallium-activated sodium iodide (NaI(TI)) scintillation detectors. Monte Carlo simulation based on the Geant4 software package was performed to take the geometrical acceptance and energy-dependent detection efficiency into account due to large non-uniformity in the material budget. True bremsstrahlung energy spectra from the 28-GHz ECR ion source were obtained using the inverse-matrix deconvolution method. The unfolding method was based on a full geometry of the Geant4 model of the ECRIS plasma. The results show that in all three measurement locations, the highest value of the spectral temperature was at an angle of 30° coincident with one of the maximum angles of the ECRIS plasma shape. [ABSTRACT FROM AUTHOR]

In this paper, the method for synthesis of a quasi-optical transmission line (QOTL) for a 45-GHz/20-kW Electron Cyclotron Resonance (ECR) ion source is proposed. The QOTL consists of five quasi-optical elliptical mirrors which had successfully transmitted the microwave power of about 12.8 m from the output of the matching optical unit to the vacuum window of the corrugated waveguide. The lengths of the major and minor axes of the five elliptical mirrors are optimized by adopting the Nelder–Mead simplex algorithm to achieve the maximum power transmission efficiency. Meanwhile, analysis of the electromagnetic fields in the QOTL system has been developed in terms of the vector diffraction theory. The model of the QOTL system is built using the Altair Feko software to simulate the electromagnetic wave propagating in free space. After the optimized design and simulation verification, the QOTL system has been fabricated, installed, and measured. The experimental results reveal that the power transmission efficiency of the QOTL system is 86.5%, including diffractive and ohmic losses. Moreover, the correlation coefficient reaches 96.53% between the field pattern of the theoretical value and the measured value at the vacuum window of the 45-GHz/20-kW ECR ion source. [ABSTRACT FROM AUTHOR]

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 2.45 GHz 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. [ABSTRACT FROM AUTHOR]

The article presents a study on the performance of an ion source based on corona discharge which is used for the detection of gaseous sulfuric acid by chemical ionization mass spectrometry (CIMS). The study mentions that the design of the ion source is the same to the one of the radioactive Americium 214 ion source, which yields almost the same identical values. Results show that the low sensitivity of sulfur dioxide is achieved even with the addition of a hydroxide scavenger.

The Rare-isotope Accelerator complex for ON-line experiments is a heavy-ion accelerator facility that accelerates a stable or rare isotope beam up to 400 kW with an energy of 200 MeV/u. Various heavy-ion beams are generated from the Electron Cyclotron Resonance Ion Source, with an energy of 10 keV/u and separated according to A/Q at the first dipole magnet (DM). To measure beam transverse emittance at the Low Energy Beam Transport section, two Allison scanners are installed behind the DM for the X and Y directions. It consist of a servo motor for driving, a Faraday cup for current measurement, deflection plates, and electronic device. The measurable range of beam angle in of the Allison scanner is determined by the structure of the deflection plate and designed based on mathematical calculations. Experimental Physics and Industrial Control System (EPICS) is adopted to integrate and control a variety of devices. To control the complex measurement sequence of the Allison scanner, an EPICS sequencer module was used. Normalized emittance is calculated by python code with Pyepics module using phase space distribution data. In this paper, we present the detailed design of the Allison scanner, the configuration of the control system, and the experimental results using an Ar9+ 30 μA beam. [ABSTRACT FROM AUTHOR]

The Advanced Ion Source for Hadrontherapy (AISHa) is an electron cyclotron resonance ion source operating at 18 GHz, developed at the Istituto Nazionale di Fisica Nucleare-Laboratori Nazionali del Sud, with the aim of producing high intensity and low emittance highly charged ion beams for hadrontherapy purposes. Moreover, thanks to its unique peculiarities, AISHa is a suitable choice for industrial and scientific applications. In the framework of the INSpIRIT and IRPT projects, in collaboration with the Centro Nazionale di Adroterapia Oncologica, new candidates for cancer treatment are being developed. In particular, the paper presents the results of the commissioning of four ion beams of interest for hadrontherapy: H+, C4+, He2+, and O6+. Their charge state distribution in the best experimental conditions, their emittance, and brightness will be critically discussed, along with the role of ion source tuning and space charge effects in beam transport. Perspectives for further developments will also be presented. [ABSTRACT FROM AUTHOR]

This paper presents the dry etching performance and expectation of highly conductive thin metal films that are hardly etched at low temperature with conventional plasma dry etching equipment. Dry etching is performed using a combination of H2 and HCl gases in a reactive ion etching system with low temperature susceptor and electron cyclotron resonance (ECR) plasma source. We could achieve high electron temperature enough to dissociate and ionize H and Cl radicals from H2 and HCl molecules. [ABSTRACT FROM AUTHOR]

In this paper, a 28 GHz TE01 mode 160° miter bend employing two plane mirrors is proposed based on the quasi-optical technique and the coupled wave theory to realize high-efficiency transmission for the electron cyclotron resonance ion source. First, the TE01 mode was converted to TE0n hybrid modes with Gaussian beam characteristics by means of the designed mode converter. Second, the phase shift section was implemented to eliminate the phase difference of the hybrid modes. Then, upon reflection of two plane mirrors, the propagation direction of a wave beam is deviated by 160°. Finally, the hybrid modes were converted to the TE01 mode using the same structures of the phase shift section and the mode converter. The simulation results reveal that the TE01 mode transmission efficiency reaches 95.22% at the central frequency of 28 GHz. Additionally, the designed 160° miter bend has been fabricated, installed, and measured. The experimental results show that the power transmission efficiency reaches 98.54% including diffraction losses and ohmic losses. [ABSTRACT FROM AUTHOR]

This paper presents Gen. 2 (370 mm * 470 mm) size thin copper film dry etching performance that is etched by high electron temperature plasma source with low temperature substrate. Dry etching is performed using HCl gas in a reactive ion etching mode. In addition, scanning low temperature susceptor and the electron cyclotron resonance (ECR) plasma produced by rectangular‐type microwave slot antenna (ReSLAN) are used. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

High-power, high-frequency gyrotrons are the only promising sources for the electron cyclotron resonance heating and current drive (ECRH&CD) in the present thermonuclear fusion plasma experiments and in future power plants. Compared to the hollow-cavity gyrotron design, the coaxial cavity gyrotron design facilitates improved mode competition control, which eventually increases the output power per tube. At KIT-IHM, the successful operation of a 170-GHz gyrotron has been demonstrated in the short-pulse regime, and the ongoing research activities are aiming to upgrade the existing coaxial cavity gyrotron from short-pulse (1–10 ms) to long-pulse (~ 1s) operation. In this paper, with the help of multiphysics simulations, the performance of the insert cooling system is verified for the continuous wave (CW) operation and the operating limits of the insert cooling systems are determined. The perfectly aligned coaxial Glidcop insert will be able to withstand operating conditions leading to a maximal heat flux of about 0.39 kW/cm2. The influence of insert misalignment on insert loading is also studied systematically in this paper. [ABSTRACT FROM AUTHOR]

Data from the Magnetospheric Multiscale (MMS) mission, in particular, the spacecraft potential measured with and without the ion beams of the active spacecraft potential control (ASPOC) instruments, plasma electron moments, and the electric field, have been employed for an improved determination of plasma density based on spacecraft potential. The known technique to derive plasma density from spacecraft potential sees the spacecraft behaving as a plasma probe which adopts a potential at which the ambient plasma current and one of photoelectrons produced at the surface and leaving into space are in equilibrium. Thus, the potential is a function of the plasma current, and plasma density can be determined using measurements or assumptions on plasma temperature. This method is especially useful during periods when the plasma instruments are not in operation or when spacecraft potential data have significantly higher time resolution than particle detectors. However, the applicable current–voltage characteristic of the spacecraft has to be known with high accuracy, particularly when the potential is actively controlled and shows only minor residual variations. This paper demonstrates recent refinements of the density determination coming from: 1) the reduction of artifacts in the potential data due to the geometry of the spinning spacecraft and due to effects of the ambient electric field on the potential measurements and 2) a calibration of the plasma current to the spacecraft surfaces which is only possible by comparison with the variable currents from the ion beams of ASPOC. The results are discussed, and plasma densities determined by this method are shown in comparison with measurements by the Fast Plasma Instrument (FPI) for some intervals of the MMS mission. [ABSTRACT FROM AUTHOR]

Beam diagnostic and especially beam current measurements represent a key aspect in the production of a high-quality beam. Due to the known interplay between beam current and beam and plasma properties, many solutions have been addressed to solve this need. Although precise beam current measuring systems exist, they cannot provide noninvasive solutions for the measurement of very low-frequency currents in electron cyclotron resonance ion source (ECRIS) beamline, with a range from tens to hundreds of microamperes. To address the above-mentioned needs, this paper proposes an indirect measurement methodology based on the estimation of the magnetic field produced by target current exploiting a residence time difference fluxgate and a flux concentrator (a mechanical structure able to constrain produced magnetic field in a given area). The main advantage of this approach is related to the possibility to perform a noninvasive current measurement. An optimal geometry for the flux concentrator has been investigated by using a finite-element method analysis that has led to the definition of a minimum value of the magnetic field generated by the minimum value of the target current, around $5.0~\mu \text{A}$ , equal to 3.07 nT. To assess the solution, an experimental setup, miming real magnetic flux intensity inside ECRIS beamlines, has been realized. The measuring strategy has a magnetic resolution of 1 nT and a current resolution of $1.6~\mu \text{A}$ , that is, in line with requirements. Results obtained demonstrate the suitability of the measurement system for the specific application addressed in this paper, both in terms of operating range and resolution. [ABSTRACT FROM AUTHOR]

Surface modification of polytetrafluoroethylene (PTFE) is performed by nitrogen ion implantation for improving the PTFE surface flashover voltage in vacuum. In this paper, nitrogen ions are produced by an electron cyclotron resonance ion source. The properties of the samples are investigated with X-ray photoelectron spectroscopy, electrometer, microhardness tester, surface potential measurement, and surface flashover system. The Stopping and Range of Ions in Matter software is used to simulate the ion implantation. Experimental results show that the surface flashover voltage of treated samples improves remarkably and increases with the injection energy. After ion implantation, the content of fluorine in the treated samples decreases, and the content of oxygen increases. The surface conductivity increases from $1.15\times 10^{{-15}}$ to 1.36 10−13 S/m, the surface potential decreases faster, and the trap density and energy increase with the implantation energy. The process of electron avalanche and the accumulation of surface charges have been suppressed, thus hindering the development of flashover and improving the surface flashover voltage. [ABSTRACT FROM AUTHOR]

The work is devoted to the development of a low-energy beam transport (LEBT) system for a high-current multicharged ion injector based on a superconducting ECR ion source. ECR ion sources are under development at the Joint Institute for Nuclear Research as part of a superheavy element research program. The LEBT includes a beam analysis system. The paper describes results of simulation of ion beam dynamics in the LEBT with the ideal field approximation for optic elements. [ABSTRACT FROM AUTHOR]

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Forward modeling is used to interpret inversion patterns of the pedestal–Scrape of Layer (SOL) Electron Cyclotron Emission (ECE) in DIII-D H-mode experiments. The modeling not only significantly improves the ECE data interpretation quality but also leads to the potential measurements of (1) the magnetic field strength |B| at the separatrix, (2) the pedestal |B| evolution during an inter-Edge Localized Mode (ELM) period, and (3) the pedestal Magnetohydrodynamics (MHD) radial structure. The ECE shine-through effect leads to three types of pedestal–SOL radiation inversions that are discussed in this paper. The first type of inversion is the non-monotonic Te,rad profile with respect to the major radius. Using the ECE frequency at the minimum Te,rad, the inversion can be applied to measure the magnetic field |B| at the separatrix and calibrate the mapping of the ECE channels with respect to the separatrix. The second type of inversion refers to the opposite phase between the radiation fluctuations δTe,rad at the pedestal and SOL. This δTe,rad phase inversion is sensitive to density and temperature fluctuations at the pedestal foot and, thus, can be used to qualitatively measure the MHD radial structure. The third type of inversion appears when the pedestal and SOL Te,rad evolve in an opposite trend, which can be used to infer the pedestal |B| field change during an inter-ELM period. The bandwidth effect on measuring δTe,rad due to pedestal MHD is also investigated in the radiation modeling. [ABSTRACT FROM AUTHOR]

An overview is given of the papers presented at the 17th JointWorkshop on Electron Cyclotron Emission (ECE) and Electron Cyclotron Resonance Heating (ECRH). The meeting covered all aspects of the research field ranging from theory to enabling technologies. From the workshop, advanced control by electron cyclotron heating and current drive is emerging as probably the main application of ECRH in fusion devices. Large progress is reported from various experiments on real-time control applications. At the same time ECE is developing into a multi-dimensional plasma diagnostic taking advantage of new technological developments. The resulting multi-dimensional ECE data reveal exciting new details of the complicated plasma dynamics in fusion devices. [ABSTRACT FROM AUTHOR]

Gyrotron oscillator, as one kind of efficient terahertz (THz) source, is developed with the capability of frequency and power tuning to meet diverse application demands. Due to system nonlinearity, it is quite difficult to achieve high frequency stabilization (FS) during power tuning without using external auxiliary components. This paper proposes an FS scheme with simultaneous power tuning in gyrotron backward-wave oscillator state. This is realized by compensating the detuning electron cyclotron frequency during the electronic tuning process. The required quasi-linear relationship between the electron-beam pitch factor and the accelerating voltage is numerically verified by using the SLAC EGUN code. The investigation focuses on a Watt-level open-cavity gyrotron oscillator. The tens-of-Watts-level output power can be tuned by over 40% at the FS point, and especially the self-adaptive FS reaches the accuracy of about 10-MHz level. The proposed scheme would be attractive for the high-stability THz-wave heating in material sciences and biomedicines. [ABSTRACT FROM AUTHOR]

Two blackbody sources permanently located within the international thermonuclear experimental reactor (ITER) diagnostic shield module at equatorial port 9 will operate in conjunction with two remotely retractable mirrors to generate and direct blackbody radiation to calibrate the radial and oblique views of the ITER electron cyclotron emission diagnostic. The main calibration requirements include a high-emissivity surface heated to 700 °C or higher, the ability to perform the calibration in high vacuum and in the presence of a magnetic field, and 5000-h operational lifetime over 20 years. Major constraints include a heater current limit of 40 A, no direct fluid cooling to mitigate failure risks, small size to avoid compromising neutron shielding, and adequate structural support to mitigate vibration loads. This paper describes the preliminary design of a hot calibration source supported by analysis and test results of a calibration source test prototype developed to address the calibration source requirements and its constraints. [ABSTRACT FROM AUTHOR]

This paper describes advances performed towards the realization of the ARGITU compact neutron source. The first part of the accelerator developed by ESS-BILBAO is made of a 2.7 GHz ECR proton source, a two-solenoid Low Energy Transport Section (LEBT) and a 352.2 MHz Radio Frequency Quadrupole (RFQ). We describe the main advances performed over the last year. The Ion source and LEBT have been in operation since 2019. On the installed part, some improvements have been implemented in the ion source such as a new RF coupler, RF stability loop, and a new RF source based on Solid State technology. On the RFQ side, the tuning algorithm has been validated in the cold model, the new coupler is being manufactured, the RF testing facility is being installed and the machining of the remaining segments is in good progress. [ABSTRACT FROM AUTHOR]

An isotope enrichment system for 39Ar has been developed at the Institute of Modern Physics, which is designed to increase the abundance of 39Ar in the incident sample gas. With intense Ar+ beams produced by a 2.45 GHz electron cyclotron resonance ion source and a high mass resolution spectrometer system, Ar isotopes are evidently separated on the target plane and selectively collected by an Al target. The separated Ar isotopes have been identified on the target plane, which is consistent with the simulations. According to the recent cross-checked results with atom trap trace analysis, a high enrichment factor of 39Ar has been successfully achieved. This paper will present the design and test results of this system. [ABSTRACT FROM AUTHOR]

To ensure further progress in the development of electron cyclotron resonance ion sources (ECRISs), deeper understanding of the underlying physics is required. The electron energy distribution (EED), which is crucial for the performance of an ECRIS, still remains obscure. The present paper focuses on the details of a well-developed technique of measuring the EED of electrons escaping axially from the magnetically confined plasma of an ECRIS. The method allows for better than 500 eV energy resolution over a range of electron energies from 4 keV to over 1 MeV. We present detailed explanation of the experimental procedure and the following data processing peculiarities with examples and discuss possible reasons of energetic electron losses from the magnetic trap, in particular the role of RF pitch angle scattering. Finally, an experimental method of approximating the confined EED based on the measurement of escaping electrons is described. [ABSTRACT FROM AUTHOR]

A new facility called CAFE2 (Chinese Accelerator Facility for super heavy Elements) has been constructed and put into routine operation at Institute of Modern Physics (IMP) in 2021. To meet the requirement of metallic ions, we assembled a room-temperature ECR ion source-LECR5 (Lanzhou Electron Cyclotron Resonance ion source No.5) as its injector. This paper mainly introduces the results of optimization of metallic ions, including 40Ca, 48Ca, 54Cr and 55Mn, with inductive heating metal oven. Calcium ions was produced by direct heating of the mixture powder of calcium oxide and aluminum. Chromium and manganese ions were obtained by heating of isotopic pure elemental materials. With different supporting gas, 1–5 puA of metallic ions have been produced and delivered to the accelerator successfully. Beam emittance and transmission efficiency will also be discussed in this paper. [ABSTRACT FROM AUTHOR]

The performance of a minimum-B Electron Cyclotron Resonance Ion Source (ECRIS) is traditionally quantified by measuring the beam current and quality of the extracted ion beams of different charge state ions. The stability of the extracted ion beam currents has drawn more attention recently as the technology is pushing its limits toward higher ion charge states and beam intensities. The stability of the extracted beam is often compromised by plasma instabilities manifesting themselves as rapid oscillations of the beam currents in millisecond scale. This paper focuses on practical aspects of diagnostics techniques of the instabilities, showcases examples of instability-related diagnostics signals, and links them to the plasma physics of ECR ion sources. The reviewed techniques include time-resolved microwave emission diagnostics, bremsstrahlung measurements, direct measurement of electron and ion fluxes, measurement of the ion beam energy spread, and optical emission diagnostics. We list the advantages and disadvantages of each technique and outline the development needs of further diagnostics. Finally, we discuss the implications of the instabilities in both historical and forward-looking context of ECRIS development. [ABSTRACT FROM AUTHOR]

Within the framework of the BELA (Based on the ECR ion source Linear Accelerator) project, designed to solve various problems, an injection complex based on several ion sources is being created. One of the tasks is multi-beam irradiation of structural materials of nuclear and thermonuclear power plants to analyze their radiation resistance. Heavy (Fe) and light (H/He) ion beams will irradiate the target in the same chamber simultaneously. To generate beams of light ions, a compact ion source based on electron cyclotron resonance (ECR source) is being developed. This paper contains a description of the design of the ECR, that is, the source of light ions and preliminary results on the generation of a helium ion beam. [ABSTRACT FROM AUTHOR]

This paper presents a description of the magnetic system of the developed electron cyclotron resonance (ECR) ion source with an operating frequency of 2.45 GHz for producing protons and doubly charged helium ions. The results of numerical simulations of the magnetic system of the ECR source built on permanent magnets are presented. A configuration with the possibility of moving the ring magnets of the injection and extraction area to adjust the magnetic field distribution, in particular, the maximum values of Binj and Bext at the plasma chamber axis, and with the possibility of moving the bars of the sextupole magnet in the radial direction to adjust the magnetic field Brad at the chamber boundary is presented. To obtain the magnetic field profile corresponding to the mode of the microwave source, the design of the magnetic system with the use of additional solenoids providing adjustment of Binj and Bext values within the required limits as well as adjustment of the minimum magnetic field Bmin on the chamber axis at fixed position of all ring magnets is considered. [ABSTRACT FROM AUTHOR]

A variety of plasma waves have been observed in the separatrix region during magnetic reconnection, and their roles on reconnection and exciting mechanisms are still controversial. In this paper, we report the whistler wave with a very narrow frequency band just above half of the electron cyclotron frequency in the separatrix region. This whistler wave is accompanied with the electron cyclotron harmonic (ECH) waves. The ECH waves have frequencies between the first and fifth harmonic of electron cyclotron frequency fce. The wave normal angle of the whistler waves is ∼20°–∼40°, meaning the quasi‐parallel propagation, while the ECH waves propagate perpendicular to the background magnetic field with θ∼87°±2°. In the separatrix region, the electrons have a loss‐cone distribution while these two kinds of waves are observed. Based on the linear theory, such an electron distribution is unstable for both whistler waves and ECH waves. It indicates that these two kinds of waves are generated by the electron loss‐cone instability. Key Points: A very narrow band whistler wave and electron cyclotron harmonic waves are simultaneously observed in the magnetosphere separatrix regionThe electron loss‐cone distributions are continuously detected while the two kinds of waves are observedThe two kinds of waves are probably excited by the electron loss‐cone instability [ABSTRACT FROM AUTHOR]

In this paper, we present the current status and both the ongoing investigation and the continuous improvements to the operational performance of a unique gyrotron, which is built using a 20 T superconducting magnet and holds a world record of 10-W terahertz wave generation at the highest frequency (1.08 THz) in the continuous wave (CW) operation. In addition, it has demonstrated high-purity single-mode generation on a sequence of modes that cover a wide range from subterahertz to terahertz frequencies at both the fundamental and second-harmonic resonances of the electron cyclotron frequency. As an illustration, the measurements of the observed radiation patterns of eight output modes radiated from a currently used resonant cavity with a linear up-taper are presented and compared with the corresponding patterns simulated by scattering matrix calculations. A new design of an optimized cavity with a nonlinear up-taper, which further improves the mode purity of the generated output radiation has been proposed and is being currently implemented as a replacement of the existing resonator. The overall operational performance and the output characteristics of this gyrotron (called FU CW III in accordance with the nomenclature adopted at FIR UF Center) make it a versatile and appropriate source of coherent CW radiation for many novel applications in the fields of high-power terahertz science and technologies. [ABSTRACT FROM AUTHOR]

We insert two probes in the upstream and the downstream regions with respect to the electron cyclotron resonance (ECR) zone which is formed at the center of mirror fields. We measure simultaneously plasma parameters in those regions by each of them under the same operating condition. We measure ion saturation currents Iis and electron energy distribution functions at two positions. We obtain measurement results that suggest the more efficient ECR on the side closer to the microwave-launchings than those on the other side. It is consistent with the accessibility condition of the right-hand polarization wave. We also compare the charge state distributions of Ar ion beams extracted in the case of launching microwaves from the coaxial semi-dipole antenna and those from the rod antenna. We observe the higher multicharged ion beam currents at the low microwave powers in the case of the rod antenna than those in the case of the coaxial semi-dipole antenna. We also confirm stable increasements of ion beam currents at considerably high microwave powers in the case of the coaxial semi-dipole antenna. Based on the experimental results, we propose a new microwave-launching method, "dual-ECR heating" and report its preferable preliminary experimental results in this paper. [ABSTRACT FROM AUTHOR]

Within the framework of the BELA project (Based on ECR ion source Linear Accelerator), designed to solve various problems, an injection complex based on several ion sources is being created. One of the tasks is multibeam irradiation of structural materials of nuclear and thermonuclear power plants to analyze their radiation resistance. Heavy (Fe) and light (H2/He) ion beams will irradiate the target in the same chamber simultaneously. To generate beams of light ions, a compact ion source based on electron cyclotron resonance (ECR source) is being developed. The paper contains description of the studies of the dependences of the operation of an ECR source of light ions with a resonant discharge chamber on the pressure of the working gas, the magnitude and distribution of the magnetic field, as well as the mass-charge spectrum of a helium-ion beam. [ABSTRACT FROM AUTHOR]

The spectral temperature Ts obtained from bremsstrahlung spectra emitted from electron cyclotron resonance (ECR) ion sources (ECRISs), in which the plasma is confined in a minimum-B magnetic field, is used as a relative indication of the temperature of the plasma hot electrons. Past bremsstrahlung measurements taken on ECRISs indicate that Ts is strongly dependent on the magnetic field gradient at the resonance zone or (B\mathrm{ min}/{B\mathrm{ ECR}}) . However, this dependence was never fully proven or explained. To further our understanding a more detailed study of the bremsstrahlung radiation for X-rays above 10 keV is underway using VENUS, a third-generation ECRIS at Lawrence Berkeley National Laboratory. Initial analysis of previous and new data has revealed that Ts appears to be dependent solely on the minimum magnetic field B\mathrm{ min} rather than (B\mathrm{ min}/{B\mathrm{ ECR}}) and the microwave frequency \omega . Decoupling Ts from (B\mathrm{ min}/{B\mathrm{ ECR}}) , mainly B_{\mathrm{ ECR}} , implies that \omega . While it certainly appears to be true that plasma density n_{e}(\propto \omega ^{2}\propto B^{2}) increases with heating frequency, as was postulated by Geller in 1987, a more careful consideration into the heating mechanism of the plasma electrons is warranted. The disassociation of Ts from the heating frequency \omega$ , while an interesting discovery, implies that we must change the way we understand how ECRISs operate. This paper presents new bremsstrahlung measurements, analyses, and discussions of the results. [ABSTRACT FROM AUTHOR]

In negative ion sources, a cusped magnetic field is generated by magnets placed around each aperture of the extraction grid in order to limit the co-extracted electron current. In spite of this suppression magnetic field, the co-extracted electron current is large, on the same order as the negative ion current extracted from the plasma. In this paper, we study the mechanisms of electron extraction from the plasma through a cusped aperture in a simplified situation, in the absence of negative ions, with the help of a three-dimensional Particle-In-Cell Monte Carlo Collisions model. The calculation results show that the electron current extracted from the plasma is small for an infinite slit aperture with a suppressed (cusped) magnetic field and significantly increases in the case of finite slit or circular grid apertures. We find that the E × B electron drift plays an important role in the extraction of electrons through a finite slit grid aperture and that current driven micro instabilities are present in the aperture region. This work is relevant to negative ion sources and micro-ECR neutralizers designed for space propulsion. [ABSTRACT FROM AUTHOR]

Plasma thrusters are required for deep space applications for reducing the fuel payload. This paper evaluates the capability of a compact ECR plasma source (CEPS) as a standalone plasma thruster in space. The unique magnetic field profile of CEPS' ring magnets enables very efficient plasma production and electron heating within the CEPS plasma source section (ID ≈ 8.5 cm, length ≈ 11.6 cm) resulting in high plasma potentials. Experiments were undertaken with the CEPS attached coaxially to a larger expansion chamber (ID ≈ 48.2 cm, length ≈ 75 cm). Diagnostics included specially designed Langmuir probes (LP) and ion energy analyzers (IEA) that are capable of withstanding the harsh plasma conditions in front of and within the CEPS. LP measurements reveal high-density argon plasma (≈1012 cm−3), with high bulk electron temperatures (≈20 eV) and plasma potentials (≈100 V) at very modest microwave power (≈600 W) over a wide range of pressures (0.3–1 mTorr). An important observation is the fall of almost the full plasma potential inside the CEPS within a short distance close to its exit, giving rise to strong ambipolar electric fields suitable for accelerating ions. IEA measurements confirmed the presence of streaming ions with energies ≈87 eV at ≈2 cm in front of the CEPS. Estimates based on the IEA results yield thrust values ≈50 mN at ≈0.5 mTorr. A 2-zone, global model was developed to determine the steady state plasma parameters (including plasma flow velocity) in the geometry of the experimental system (without magnetic field). The model reproduced the key experimental plasma parameters and was extended to compute plasma thrust under actual space-like conditions. The computed thrust values for xenon are higher (≈80 mN) than that for argon (≈40–45 mN) at ≈600 W of microwave power. [ABSTRACT FROM AUTHOR]

In this paper, we propose a collective Thomson scattering (CTS) diagnostic for fast ion measurements for the GDT (gas-dynamic trap) facility at the Budker Institute. The diagnostic utilizes the 54.5 GHz gyrotron usually used for electron cyclotron resonance heating as a source of probe radiation and is aimed at reconstruction of distributions over transverse and longitudinal velocities of NBI-driven ions in the plasma core. Here we present a feasibility study of this concept showing a possibility to receive a strong CTS signal of several hundred eVs for a wide range of GDT parameters. The main limitations come from the refraction of the probe and scattered radiation propagating in inhomogeneous plasma: to provide well-resolved CTS measurements the on-axis plasma density should be kept less than 1.5 · 1013 cm−3 while usual GDT discharges correspond to the density of (0.9 − 1.3)· 1013 cm−3. [ABSTRACT FROM AUTHOR]

Neutron beams are used in a wide range of applications, mainly aimed at determining and understanding the properties of condensed matter. This paper describes one such proposed compact neutron source, ARGITU, a unique and versatile accelerator-driven neutron source being proposed by ESS Bilbao. As aforementioned, the neutron source configured with beryllium target will produce ~10 SP 14 sp n s SP -1 sp , being therefore considered as a medium flux neutron source. [Extracted from the article]

Production of high charge state ions in electron cyclotron resonance ion sources (ECRISs) is dependent on the electron energy distribution (EED) within the source plasma. In order to better understand the EED, a measurement of electrons escaping axially from an ECRIS device has been performed at the National Superconducting Cyclotron Laboratory. Electrons were measured escaping from the Superconducting Source for Ions, driven at 18 GHz. Dependencies of the observed EED on the confining magnetic field strength and injected microwave power are reported. This paper focuses on large peaks of electrons in the 400–1200 keV energy range. Measurements of the axial bremsstrahlung spectrum have been simultaneously carried out to provide a direct comparison between both techniques. A comparison between the energy associated with the peak of the electron distribution and the spectral temperature of the bremsstrahlung distribution is shown. [ABSTRACT FROM AUTHOR]

The Space Environment Simulation and Research Infrastructure project, which uses various ion beams as irradiated materials in life science research, is being built at the Harbin Institute of Technology. A new room temperature electron cyclotron resonance ion source, the Lanzhou Electron Cyclotron Resonance Ion Source No. 5 (LECR5), has been designed and constructed. It is an intense, highly charged, heavy ion beam injector which generates ion beams from H to Bi, typically ∼50 eμA 209Bi32+. The LECR5 is designed to operate at microwave frequencies in the range of 14.5–18 GHz. The typical magnetic parameters are designed based on those optimized for SECRAL, which operates at 18 GHz. This paper presents the LECR5 ion source, its test bench, and the preliminary beam results. [ABSTRACT FROM AUTHOR]

Electron cyclotron resonance ion sources (ECRISs) are widely applied for ion beam applications, e.g., plasma processing, cancer therapy, and ion engine of an artificial satellite. In our ECRIS, we aim at producing and extracting various ion beams from this device, in particular, Xeq+ ion beams at low energy. In the aerospace engineering field, there are problems of accumulated damages on various component materials caused by low energy of Xe ions from the engine. There are not enough experimental sputtering data for satellite materials at the Xeq+ in the low energy region. Then, we are trying to investigate the sputtering yield experimentally by irradiating the low energy Xe ion beams. To perform this experiment, it is necessary to acquire a certain amount of beam current with low energy. Then, we generate the low energy ion beams by the following steps: First, the ion beams are extracted from the ECRIS at high voltage. Next, these are transported to an ion beam irradiation system (IBIS). Finally, the ion beams are decelerated by the deceleration voltage in the IBIS. We adjusted the beamline. We measure the characteristics of the transport efficiency and decelerated ion beam currents. In this paper, we describe the experimental setup using an existing ECRIS for decelerated heavy ion beams and the results of decelerated ion beam currents. [ABSTRACT FROM AUTHOR]

A 2.45 GHz microwave-driven ion source for the generation of multicharged ions has been designed and built at Peking University recently. The magnetic field configuration of this ion source is a minimum-B type with a combination of a hexapole field and an axial mirror field. Argon was selected as the first tested beam generated by this ion source. A 63 µA Ar4+ ion beam at 35 kV extraction voltage was obtained in the pulsed mode (50 Hz/500 µs). Without the hexapole magnetic field, the highest charge state was only Ar2+, and no Ar4+ ion beam was detected. The comparison between the two sets of experimental results with different magnetic configurations has proven the rationality of the production of multicharged ions with this ion source. Both experimental results and discussion will be presented in this paper. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

An innovative 18 GHz HIISI (Heavy Ion Ion Source Injector) room temperature Electron Cyclotron Resonance (ECR) ion source (ECRIS) has been designed and constructed at the Department of Physics, University of Jyväskylä (JYFL), for the nuclear physics program of the JYFL Accelerator Laboratory. The primary objective of HIISI is to increase the intensities of medium charge states (M/Q ≅ 5) by a factor of 10 in comparison with the JYFL 14 GHz ECRIS and to increase the maximum usable xenon charge state from 35+ to 44+ to serve the space electronics irradiation testing program. HIISI is equipped with a refrigerated permanent magnet hexapole and a noncylindrical plasma chamber to achieve very strong radial magnetic confinement with Brad = 1.42 T. The commissioning of HIISI began in Fall 2017, and in Spring 2019, it has met the main objectives. As an example, the intensity of the Xe27+ ion beam has improved from 20 μA to 230 μA. In addition, the beam intensity of the Xe44+ ion beam has exceeded the requirement set by the irradiation testing program. The performance of HIISI is comparable to superconducting ECR ion sources with the same maximum microwave frequency of 18 GHz and a total power of 3 kW. For example, Ar16+ and Xe30+ ion beam intensities of 130 μA and 106 μA, respectively, have been obtained with a total microwave power of 3 kW distributed between 18, 17.4, and 14.5 GHz frequencies. The ion beams have been extracted through an 8 mm plasma electrode aperture using 15–17 kV extraction voltage. The latest development work, extracted ion beam intensities, special features, and future prospects of HIISI are presented in this paper. [ABSTRACT FROM AUTHOR]

The paper presents recent results of a "pointlike" neutron source development based on a D-D fusion in a D-loaded target caused by its bombardment with a sharply focused deuterium ion beam. These developments are undergoing at the Institute of Applied Physics of Russian Academy of Sciences in order to study a possibility to create an effective and compact device for fast-neutron radiography. The last experiments with a beam produced by a gasdynamic high-current ECR ion source and its focusing with a magnetic lens demonstrated that 60 mA of deuterium ions may be constricted to a transversal size of ∼1 mm at the focal plane. With a purpose to improve this result in terms of the beam current and its size, a combined electrostatic and magnetic focusing system is proposed and analyzed. It is shown that the combined system may enhance the total beam current and reduce its footprint down to 0.13 mm. All numerical analysis was performed using the IBSimu code. [ABSTRACT FROM AUTHOR]

The GTS-LHC ECR ion source (named after the Grenoble Test Source and the Large Hadron Collider) at CERN provides heavy ion beams for the chain of accelerators from Linac3 up to the LHC for high energy collision experiments and to the Super Proton Synchrotron for fixed target experiments. During the standard operation, the oven technique is used to evaporate lead into the source plasma to produce multiple charged lead ion beams. Intensity and stability are key parameters for the beam, and the operational experience is that some of the source instabilities can be linked to the oven performance. Over long operation periods of several weeks, the evaporation is not stable which makes the tuning of the oven unpredictable and nonreproducible. A dedicated test stand is used to study the oven performance and possible improvements independently of the source operation. It was observed that the measured evaporation rate of the oven can vary spontaneously in a wide range even when stable operating conditions are applied to the oven controls. Data collected at the test stand hint that these fluctuations are caused by temperature instabilities of the oven itself. Several ways to improve the oven stability were tested, including insulation changes and modifications of the oven crucible. Some of the most promising results regarding the stability of the evaporation will be presented in this paper. [ABSTRACT FROM AUTHOR]

According to the requirements of ion beams extracted from an electron cyclotron resonance ion source transverse phase space coupling research and the afterglow beam property effective measurement, a pepper pot type meter called PEMiL (Pepper Pot Emittance Meter in Lanzhou) has been designed, fabricated, and commissioned to obtain the emittance of high intensity highly charged heavy ion beams. The direct current beam emittance measurement results verify the coupling property caused by the semisolenoid field. This paper also describes the scheme of multiple exposure accumulation which was applied to measure the afterglow beam property, and the transverse phase space distribution of the oxygen afterglow beam which was measured for the first time is presented. [ABSTRACT FROM AUTHOR]

We have considered the accessibility condition of electromagnetic and electrostatic waves propagating in an electron cyclotron resonance (ECR) ion source (ECRIS) plasma and then investigated experimentally their correspondence relationships with production of multicharged ions. It has been clarified that there exists an efficient configuration of ECR zones for producing multicharged ion beams and has been suggested that a new resonance, i.e., upper hybrid resonance (UHR), must have occurred. We have been trying to perform advanced experiments with 4–6 GHz X-mode microwaves to the 2.45 GHz ECRIS plasma, and we have succeeded in enhancing the production of multicharged ions by launching X-mode microwaves of these bands. Furthermore, at the same time, we have observed sharp increases in electron energy distribution functions in the ECRIS plasma by means of probe methods. It has been concluded that the UHRs must have occurred when applying multiplex microwaves with their frequencies away from those frequencies for ECR in the ECRIS. In this paper, we will describe in brief the theoretical background and the results of these new experiments. [ABSTRACT FROM AUTHOR]

LAPECR3 (Lanzhou All Permanent magnet Electron cyclotron Resonance ion source No. 3) had been developed as an ion injector of Heavy Ion Medical Machine (HIMM) accelerator facility since 2009. The first HIMM accelerator facility was built in Wuwei city in 2015, and the LAPCER3 ion source has delivered C5+ ion beam to HIMM for more than 1000 days in the past four years. In order to improve the performance of the LAPECR3 ion source for intense carbon beams production, continuous research and development work has been made. The recently developed LAPECR3 ion source together with the new low-energy beam transportation can provide better performance in terms of both beam intensity and quality. This paper will generally review the LAPECR3 ion source operation status for HIMM, and the recent improvement will be presented, especially the stable beams production of C4+ and C5+. [ABSTRACT FROM AUTHOR]

The electron confinement in an electron cyclotron resonance ion source is considered a critical factor that has a great influence on the working efficiency. In this paper, a three-dimensional electromagnetic particle-in-cell code is presented for simulations of the electron confinement in minimum-B structures. Electron dynamics under the effect of electromagnetic fields is modeled through a leapfrog scheme by solving Maxwell's equations and the particle equations of motion iteratively. Some characteristics of electron magnetic confinement are obtained through a benchmarking example. Preliminary results of the simulation show good agreement with the well-known effects. [ABSTRACT FROM AUTHOR]

This paper presents a review of the experimental achievements related to the development of high-power gyrotron oscillators for long-pulse or CW operation and pulsed gyrotrons for many applications. In addition, this work gives a short overview on the present development status of frequency step-tunable and multi-frequency gyrotrons, coaxial-cavity multi-megawatt gyrotrons, gyrotrons for technological and spectroscopy applications, relativistic gyrotrons, large orbit gyrotrons (LOGs), quasi-optical gyrotrons, fast- and slow-wave cyclotron autoresonance masers (CARMs), gyroklystrons, gyro-TWT amplifiers, gyrotwystron amplifiers, gyro-BWOs, gyro-harmonic converters, gyro-peniotrons, magnicons, free electron masers (FEMs), and dielectric vacuum windows for such high-power mm-wave sources. Gyrotron oscillators (gyromonotrons) are mainly used as high-power millimeter wave sources for electron cyclotron resonance heating (ECRH), electron cyclotron current drive (ECCD), stability control, and diagnostics of magnetically confined plasmas for clean generation of energy by controlled thermonuclear fusion. The maximum pulse length of commercially available 140 GHz, megawatt-class gyrotrons employing synthetic diamond output windows is 30 min (CPI and European KIT-SPC-THALES collaboration). The world record parameters of the European tube are as follows: 0.92 MW output power at 30-min pulse duration, 97.5% Gaussian mode purity, and 44% efficiency, employing a single-stage depressed collector (SDC) for energy recovery. A maximum output power of 1.5 MW in 4.0-s pulses at 45% efficiency was generated with the QST-TOSHIBA (now CANON) 110-GHz gyrotron. The Japan 170-GHz ITER gyrotron achieved 1 MW, 800 s at 55% efficiency and holds the energy world record of 2.88 GJ (0.8 MW, 60 min) and the efficiency record of 57% for tubes with an output power of more than 0.5 MW. The Russian 170-GHz ITER gyrotron obtained 0.99 (1.2) MW with a pulse duration of 1000 (100) s and 53% efficiency. The prototype tube of the European 2-MW, 170-GHz coaxial-cavity gyrotron achieved in short pulses the record power of 2.2 MW at 48% efficiency and 96% Gaussian mode purity. Gyrotrons with pulsed magnet for various short-pulse applications deliver Pout = 210 kW with τ = 20 μs at frequencies up to 670 GHz (η ≅ 20%), Pout = 5.3 kW at 1 THz (η = 6.1%), and Pout = 0.5 kW at 1.3 THz (η = 0.6%). Gyrotron oscillators have also been successfully used in materials processing. Such technological applications require tubes with the following parameters: f > 24 GHz, Pout = 4–50 kW, CW, η > 30%. The CW powers produced by gyroklystrons and FEMs are 10 kW (94 GHz) and 36 W (15 GHz), respectively. The IR FEL at the Thomas Jefferson National Accelerator Facility in the USA obtained a record average power of 14.2 kW at a wavelength of 1.6 μm. The THz FEL (NOVEL) at the Budker Institute of Nuclear Physics in Russia achieved a maximum average power of 0.5 kW at wavelengths 50–240 μm (6.00–1.25 THz). [ABSTRACT FROM AUTHOR]