Electron Cyclotron Resonance Ion Source Research Articles

Experimental investigation of electrostatic capture of 1+ ions in charge breeder electron cyclotron resonance ion source plasma

We present comprehensive experimental data demonstrating that the capture process of the 1+ ions in charge breeder electron cyclotron resonance ion sources (ECRIS) is dominated by electrostatic deceleration by the ambipolar plasma potential, not by cumulative small-angle scattering of the incident ions in ion–ion collisions as postulated previously. To achieve this we varied the plasma potential of an ECRIS charge breeder by adjusting the microwave power applied to sustain the helium discharge and measured the corresponding shift in the optimum injection energy of the 1+ ions. The experiment was repeated with sodium, potassium, and cesium ions. It is shown that the optimum injection energy does not depend on the incident ion mass, which contradicts the collisional drag model. Conversely, the optimum injection energy (in eV) shifts in unison with the plasma potential (in V), which provides strong evidence for the electrostatic deceleration hypothesis.

Design and beam dynamics simulation of an 8 MeV compact accelerator-driven neutron source

A compact accelerator-driven neutron source is proposed at Sino-French Institute of Nuclear Engineering and Technology, Sun Yat-Sen University, called Sun Yat-Sen University Proton Accelerator Facility (SYSU-PAFA). The proton accelerator is composed of a proton electron cyclotron resonance source, a four-vane radio frequency quadrupole (RFQ), and an alternative phase focusing drift tube linac (APF-DTL). It can accelerate 10 mA proton beam to 8 MeV. Due to the high current, beam matching is particularly important. In order to achieve beam matching between various components, beam transport sections are needed. The beam transport line is divided into three segments. The Low Energy Beam Transport (LEBT) ensures that the beam parameters are matched before entering the RFQ. The Medium Energy Beam Transport (MEBT) segment efficiently transfers the beam between the RFQ and DTL. The High Energy Beam Transport (HEBT) focuses on transporting the beam to the targets. The design goal of beam transport line is as short as possible while ensuring high efficiency of beam transportation. SYSU-PAFA has an overall transmission efficiency of 99%, with optimal transverse matching conditions between beam transport and RFQ or DTL accelerators. The efficient use of solenoids and magnets allows for a compact transmission section, resulting in a total length of 13.6 meters, shorter than most accelerators at the same beam energy. This paper will provide the detailed beam dynamics of the compact accelerator.

Angular Distribution of Bremsstrahlung Spectral Temperature Measured in a Full Dimension of ECR Ion Source Using NaI(TI) Detector

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.

Characterization of hydrogen plasma bulk in 2.45 GHz ECR ion source

Electron cyclotron resonance ion source (ECRIS) as the front-end for the neutral beam injection (NBI) system has production potential of hydrogen ion beam in tokamaks. In this article, two methods are hired to evaluate the plasma ion fractions: H+, H2+ and H3+ with respect to the ECRIS operating parameters. The methods are matured by utilizing 28 important volume and surface collisions processes. We encrypted a global 0D numerical model (GM) based on solving the nonlinear equations of plasma species as the first method. Next, a 3D plasma simulation (PS) is applied through the finite element method (FEM) by COMSOL Multiphysics. Then, the results are compared to the experimental data.

Development of a 50kV hydrogen-helium mixed ion beam implanter.

Ion implanters have extensively been employed to simulate the irradiation effects of neutrons on relevant nuclear materials. In this study, a 50kV hydrogen-helium mixed ion beam implanter was developed to generate H2+ and He+ ion beams, with a beam current of 20 µA, while keeping the impurity ion content below 2%. The ions are generated by an antenna-type 2.45GHz electron cyclotron resonance ion source, and the hydrogen-to-helium ion beam ratio was controlled using two gas mass flow controllers to ensure long time stability of the beam current. As a result, the H2+/He+ ratio, beam size, and homogeneity of the beam spot can be maintained at a stable level. The beam line consisted of four Wien filters, a movable dual-slit plate, and an accelerator tube. The experimental results demonstrated successful transport of more than 20 µA of H2+ and He+ ion beams onto the target, with a beam axis deviation of less than 0.5mm.

Progress in heavy ion cancer therapy at IMP and future development

AbstractBasic research on heavy ion cancer therapy such as radiobiology, medical physics, and therapeutic technique has been conducted at the Institute of Modern Physics (IMP), Chinese Academy of Sciences since 1995. Based on the achievements acquired in the basic research and the requirements for a heavy ion accelerator for radiotherapy purposes, a dedicated heavy ion therapy facility named Heavy Ion Medical Machine (HIMM) was designed at IMP and constructed in Wuwei, China. The HIMM facility consists of two electron cyclotron resonance ion sources, one cyclotron as the injector and one synchrotron as the main accelerator, and four different treatment rooms equipped with passive or active beam delivery systems, and accelerates carbon ions up to 400 MeV/u. After the performance inspection of HIMM organized by the National Medical Device Inspection Center, preclinical tests like cell and animal radiobiological experiments and dosimetric verification using anthropomorphic phantoms for elucidating the biophysical properties of the carbon ion beams provided by HIMM were carried out. According to the Chinese medical device regulations, a clinical trial in which 46 tumor patients were recruited and two hospitals participated was conducted in the HIMM facility, aiming at evaluating the treatment safety and short‐term efficacy of the medical device. The success of the clinical trial helped the HIMM facility be authorized by the Chinese government as a class III medical device. In this paper, all the aspects mentioned above are introduced and discussed, and implications for future improvements are also given.

Characterization and modeling of plasma sheath in 2.45 GHz hydrogen ECR ion sources

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.

Development of a high current electron beam facility for compact accelerator neutron source target thermal tests

Target thermal capabilities are one of the major key points for CANS (Compact Accelerator-based Neutron Source) developments. Indeed, high energy (few MeV) and high average current (few tens of mA) proton or deuteron beams are required to produce high thermal neutron flux of 101³ n.cm⁻2.s⁻1 or greater. The targets must therefore absorb and dissipate a high thermal power. In order to make progress on their designs without deuteron or proton beams, we developed a compact electron beamline based on an Electron Cyclotron Resonance (ECR) source that permits testing of targets under relevant thermal conditions at power densities up 3 kW. cm⁻2.

The research progress of an E//B neutral particle analyzer

An // neutral particle analyzer (NPA) has been designed and is under development at Sichuan University and Southwestern Institute of Physics. The main purpose of the // NPA is to measure the distribution function of fast ions in the HL-2A/3 tokamak. The // NPA contains three main units, i.e. the stripping unit, the analyzing unit and the detection unit. A gas stripping chamber was adopted as the stripping unit. The results of the simulations and beam tests for the stripping chamber are presented. Parallel electric and magnetic fields provided by a NdFeB permanent magnet and two parallel electric plates were designed and constructed for the analyzing unit. The calibration of the magnetic and electric fields was performed using a 50 kV electron cyclotron resonance ion source (ECRIS) platform. The detection unit consists of 32 lutetium-yttrium oxyorthosilicate (LYSO) detector modules arranged in two rows. The response functions of , hydrogen ions ( , and ) and for a detector module were measured with Am, Cs and Eu sources together with the 50 kV ECRIS platform. The overall results indicate that the designed // NPA device is capable of measuring the intensity of neutral hydrogen and deuteron atoms with energy higher than 20 keV.

Metal evaporation dynamics in electron cyclotron resonance ion sources: plasma role in the atom diffusion, ionisation, and transport

We present a numerical study of metals dynamics evaporated through resistively heated ovens in electron cyclotron resonance (ECR) plasma traps, used as metal ion beam injectors for accelerators and multi-disciplinary research in plasma physics. We use complementary numerical methods to perform calculations in the framework of the PANDORA trap. The diffusion and deposition of metal vapours at the plasma chamber’s surface are explored under molecular flow regime, with stationary and time-dependent particle fluid calculations via COMSOL Multiphysics®. The ionisation of vapours is then studied in the strongly energised ECR plasma. We have developed a Monte Carlo (MC) code to simulate the in-plasma metal ions’ dynamics, coupled to particle-in-cell simulations of the plasma physics in the trap. The presence of strongly inhomogeneous plasmas leads to charge-exchange and electron-impact ionisations of metals, in turn affecting the deposition rate/pattern of the metal on the walls of the trap. Results show how vapours dynamics depends both on evaporated metals and the plasma target. The 134Cs, 176Lu, and 48Ca isotopes were investigated, the first two being radioisotopes interesting for the PANDORA project, and the third as one of the most required rare isotope by the nuclear physics community. We present an application of the study: MC computing the γ activity due to the deposited radioactive neutral nuclei during the measurement time, we quantitatively estimated the overall γ-detection system’s efficiency using GEANT4, including the poisoning γ-signal from the walls of the trap, relevant for the γ-tagging of short-lived nuclei’s decay rate in the PANDORA experiment. This work can give valuable support both to the evaporation technique and plasma source optimisation, for improving the metal ion beam production, avoiding huge deposit/waste of metals known to affect the long-term source stability, as well as for radio-safety aspects and reducing material waste in case of rare isotopes.

Development of a gas jet coupled electron cyclotron resonance ion source for radioactive ion beam

A 2.45 GHz electron cyclotron resonance (ECR) ion source coupled to a gas-jet skimmer system has been developed for the online production of radioactive ion beams (RIBs). Using radial injection of gas jet in the ion source, RIBs of 11C1+, 11CO21+, and 11CO1+ have been produced online with beam intensity up to about 9 × 103 particles per second for a 1 µA primary proton beam bombarding a nitrogen gas target. The details of the gas jet coupled ECR ion source and the results for stable isotope beams and RIBs are reported.

A very low energy ion beam extraction system design of the GTS ECR ion source at GANIL

The GTS ion source, operated at 14.5GHz, provides multiply charged heavy ion beams for the ARIBE facility at GANIL. The facility variety is limited by the efficiency of the extraction especially in the few keV/q domain. In order to improve the ion source, the extraction system was upgraded numerically using IBSimu. The shape of the plasma and the puller electrodes was changed. It causes the increase of the electric field near the plasma meniscus and allows the use of lower extraction voltages at constant total ion beam current. The required beam parameters were taken from the experimental data. The opportunity of effective low energy beam formation (at a few keV/q or several hundreds eV/q beam energy) was studied. The high current and low energy ion beam production will provide new possibilities for ARIBE facility users.

Characterization of the energy response of a LYSO+SiPM detector module for E//B NPA using [formula omitted] and hydrogen ions

This article presents a novel application of the lutetium-yttrium oxyorthosilicate (LYSO) scintillator in a newly constructed neutral particle analyzer with a parallel electric and magnetic fields structure (E//B NPA). The LYSO scintillator, coupled to the silicon photomultiplier (SiPM) without a reflector, serves as the detector module in the E//B NPA. The LYSO+SiPM configuration offers numerous advantages for the NPA application, including high efficiencies, compact size, low voltage operation, and exceptional resistance to magnetic fields. The performance of a prototype detector module was studied using a radioactive source in conjunction with the 50 kV electron cyclotron resonance (ECR) ion source platform. The crosstalk of optical photons from adjacent detector modules was examined with two detectors, and it was determined to be negligible. The high-energy α spectra exhibited a distinctive two-shoulder structure, which arises from α particles impinging on different positions of the LYSO crystal surface. This observation was further investigated through Geant4 simulations. The detector module was found to have a low-energy limit of 10 keV for hydrogen ions. In the comprehensive measurements, linear energy responses were observed for α particles and hydrogen ions within the error bars. The relative light yield of α and hydrogen ions exhibited a different trend compared to that of γ rays or electrons, providing valuable insights for the study of non-proportionality of light yield for light ions in the LYSO scintillator.

Metallic Neutral Vapours Diffusion in Electron Cyclotron Resonance Ion Sources: Fluid Dynamics and Particle Tracing Simulations

Resistive oven technique is used to inject vapours of metallic species in electron cyclotron resonance (ECR) plasma traps, where plasma provides step-wise ionization of neutral metals, producing charged ion beams for accelerators. We present a numerical survey of metallic species suitable for oven injection in ECR ion sources, studying neutrals diffusion and deposition under molecular flow regime. These aspects depend on geometry of the evaporation inlet, thermodynamics, and plasma parameters, which strongly impact on ionization and charge-exchange rate, thus on the fraction of reacting neutrals. We considered diffusion of metals with and without plasma. The plasma and its parameters have been modelled considering an established self-consistent particle-in-cell model. Numerical predictions might be relevant to reduce the metal consumption, to increase the overall efficiency, and to improve the plasma ion source performances. As test case, we studied the 134Cs isotope, as one of the alkali metals of interest for the modern nuclear physics.

Upgrades and developments related to stable ion beams injectors at INFN-LNL

The LNL accelerator complex is equipped with two stable ion beams injectors, employing respectively negative and positive ion sources. In particular, a sputtering-type negative ion source and an Electron Cyclotron Resonance Ion Source (ECRIS) are installed on high voltage platforms, to provide the optimum injection energy in the downstream accelerators. Recently, the two injectors have been object of upgrades and developments, in order to improve the overall safety and reliability of the two systems, as well as the beams available for the users. This contribution describes the work related to the above-mentioned activities, the technical choices employed and the latest results on ion beams production.

An experimental investigation of the proton fraction in a three electrode 2.45 GHz ECR ion source

The ion beam extracted from a proton ion source contains H+ ion along with H2 + and H3 + molecular ions. In this work, the ionic fractions in the extracted beam of ECR ion source were measured using an analyzing magnet. A computerized proton fraction measurement setup is described in detail with instrumentation and control for pulsed operation of the ECR ion source. A timing diagram has been incorporated for trigger synchronization illustrating the process of pulsing the plasma, controlling the analyzing magnet parameters and acquiring data about the magnetic field and beam current. The proton fraction was measured in two cases, in the first case using SS304 plasma chamber and in the second case incorporating aluminium (Al) cylinder and boron nitride (BN) plates inside the plasma chamber. In the first case, the proton fraction was found to be in the range of ∼60% and in the second case because of the presence of secondary electron donors it increased to 93%. In order to understand the enhancement of H+ fraction in the hydrogen plasma, plasma parameters (ne , Te and EEDF) and its dependence on microwave power and neutral gas pressure were investigated.

AISHa: an ECRIS for nuclear-physics, new clinical protocols and material experiments

The Advanced Ion Source for Hadrontherapy (AISHa) is an ECR ion source operating at 18 GHz, developed with the aim to produce multiply charged ion beams with low ripple, high stability and reproducibility. Due to its unique peculiarity, it is the most suitable choice for medical applications, but also for nuclear-physics and material experiments. Two sources have been realized: the first at INFN-LNS and the second at the Centro Nazionale di Adroterapia Oncologica (CNAO). The first one, fully commissioned at INFN-LNS, will be used as test-bench for development of new beams and several R&D activities are planned within the IONS experiment to increase plasma confinement and to refine techniques of non-invasive plasma diagnostics to correlate plasma and beam parameters. The second one recently produced the first beam and it will allow to increase the CNAO potential in the field of experimental and industrial research, with the long-term goal of introducing new ionic species into clinical practice such as helium, oxygen and later also iron and lithium, useful for bio-spatial research. In this work, the key peculiarities and the experimental results of the two Aisha ion sources will be presented.

Development of a 1/2-length prototype high field Nb3Sn magnet for the 4th generation ECR ion source

Development of a 1/2-length prototype high field Nb3Sn magnet for the 4th generation ECR ion source

Beam commissioning of the SARAF Injector and MEBT (protons)

The SARAF Phase II cryogenic linear accelerator (linac) is currently under construction and will be commissioned through collaborative efforts between SNRC and CEA. The linac will accelerate a 5 mA pulsed/continuous wave (CW) proton and deuteron beam, reaching energies of up to 35 MeV and 40 MeV, respectively. The linac injector consists of Phase I components, including an ECR ion source, a Low-Energy Beam Transport (LEBT) line, and a 4-rod Radio Frequency Quadruple (RFQ). Additionally, a new Medium Energy Beam Transport (MEBT) line has been installed and integrated into the injector infrastructure. The MEBT includes three rebuncher resonators, magneto-optical elements, and beam diagnostics. The MEBT beam diagnostics, as well as the Phase I D-plate installed downstream, were used for beam characterization. The downstream-installed Temporary Beam Line (TBL) and a prototype of the Gallium Indium Liquid Target (GALIT) were used for commissioning, operating at high beam duty cycles, including CW mode. The report describes the proton beam commissioning process of the injector prior to the delivery of the cryomodules, scheduled for the second half of 2023.

Development and validation of the E parallel B type neutral particle analyzer on the HL-3 tokamak

An E parallel B type neutral particle analyzer (E∥B NPA) that simultaneously provides energy and mass resolved measurements of confined fast ions has been developed on the HL-3 tokamak. To verify the operation and modeling of the diagnostic design, the analyzer was validated with H+ and H2+ beams from an electron cyclotron resonance (ECR) ion source platform with a maximum energy of 50 keV. Results show that it approaches a satisfactory degree of consistency with the simulation results using COMSOL, according to the strike positions of particles hitting the scintillator detector which are registered from the viewing window. The obtained data from the last HL-3 experimental campaign allow us to conclude that the E∥B NPA successfully detected the fast neutrals. Furthermore, the observed dependence of counts on detector channels are corresponding to the injection of neutral beam (deuterium, E = 40 keV). Therefore, the measurement capabilities of different energies and mass of fast ions of this E∥B NPA are validated.