The control of fluctuations generated in an electron cyclotron resonance (ECR) plasma is attempted by changing microwave powers. It is found that when a cage is introduced in the vacuum chamber, the fluctuations change from turbulent state to chaotic state in the high microwave power region while it changes from chaotic state to periodic state in the low microwave power region. This result suggests that the geometry of the cage affects the state of the instability. Moreover it is found that the superposition of multicusped fields created by small permanent magnets reduces the chaotic dimension of the instability. When pulsed multipole magnetic fields are also added to external magnetic fields, the fluctuations are suppressed.
Energy distribution of electrons in the plasma sustained by the electron-cyclotron resonance (ECR) discharge has a complicated shape as a function of various parameters that still remains unknown. Meanwhile, it is an important plasma characteristic. Some methods and approaches give the possibility to estimate or measure the properties of the distributions of the electrons lost from the plasma. One of them, similar to the ion mass spectrometry, was used in this work to obtain such distributions in the non-classical continuous ECR ion source with high (up to $ 50-100$ W/cm$ ^ 3 $) energy input f…
Kinetic instabilities in a dense plasma of a continuous ECR discharge in a mirror magnetic trap at the GISMO setup are studied. We experimentally define unstable regimes and corresponding plasma parameters, where the excitation of electromagnetic emission is observed, accompanied by the precipitation of energetic electrons from the magnetic trap. Comprehensive experimental study of the precipitating electron energy distribution and plasma electromagnetic emission spectra, together with theoretical estimates of the cyclotron instability increment proves that under the experimental conditions th…
A numerical tool for analysing spatially anisotropic electron populations in electron cyclotron resonance (ECR) plasmas has been developed, using a trial-and-error electron energy distribution function (EEDF) fitting method. The method has been tested on space-resolved warm electrons in the energy range $2-20\,\mathrm{keV}$, obtained from self-consistent simulations modelling only electron dynamics in ECR devices, but lacked real-world validation. For experimentally benchmarking the method, we attempted to numerically reproduce the experimental X-ray emission spectrum measured from an argon pl…
We report experimental results of vacuum ultraviolet (VUV) emission from the plasma of an electron cyclotron resonance (ECR) discharge in hydrogen, sustained by powerful millimeter-wavelength radiation of a gyrotron. Distinctive features of the considered discharge are the high plasma density ($10^{13}$ cm$^{-3}$ order of magnitude) and, at the same time, the high electron average energy ($10 - 300$ eV), which makes it possible to significantly increase the efficiency of VUV re-emission of the energy deposited into the plasma by the microwave radiation. Experiments were performed with the plas…
Gasdynamic electron cyclotron resonance ion sources are known for their ability to produce huge currents of low to moderately charged ion beams with superior quality. This is achieved by means of tens of kW of microwave heating power, leading to high plasma density. Average power density in the plasma chamber may reach hundreds of W/cm$^3$, which poses very high thermal load to plasma chamber walls. A water-cooled plasma chamber has been developed for the GISMO gasdynamic ECRIS, which is able to handle 10 kW of input microwave power with average power density in the plasma of 250 W/cm$^3$. The…
A simplified and straightforward methodology that may be used to measure N(4 S) density by TALIF technique in strongly emissive plasmas is presented. The method makes use of the absorption peak intensities instead of the fully integrated absorption line intensity. The use of this method, along with a physics-based fitting/filtering procedure enables strongly reducing the experimental uncertainty and performing measurement even in strongly emitting discharges. After validation, the method was employed to investigate the transients of a strongly emissive pulsed microwave discharge. We especially…
A new method for determining plasma parameters from beam current transients resulting from short pulse 1+ injection into a Charge Breeder Electron Cyclotron Resonance Ion Source (CB-ECRIS) has been developed. The proposed method relies on few assumptions, and yields the ionisation times $1/n_e\left\langleσv\right\rangle^{\text{inz}}_{q\to q+1}$, charge exchange times $1/n_0\left\langleσv\right\rangle^{\text{cx}}_{q\to q-1}$, the ion confinement times $τ^q$, as well as the plasma energy contents $n_e\left\langle E_e\right\rangle$ and the plasma triple products $n_e \left\langle E_e\right\rangle…
The measurement of the axially lost electron energy distribution escaping from a minimum-B electron cyclotron resonance ion source in the range of 4-800 keV is reported. The experiments have revealed the existence of a hump at 150-300 keV energy, containing up to 15% of the lost electrons and carrying up to 30% of the measured energy losses. The mean energy of the hump is independent of the microwave power, frequency and neutral gas pressure but increases with the magnetic field strength, most importantly with the value of the minimum-B field. Experiments in pulsed operation mode have indicate…
Active Plasma Resonance Spectroscopy (APRS) is a well-established plasma diagnostic method: a radio frequency signal is coupled into the plasma via a probe or antenna, excites it to oscillate, and the response is evaluated through a mathematical model. The majority of APRS probes are invasive and perturb the plasma by their physical presence. The planar Multipole Resonance Probe (pMRP) solves this problem: it can be integrated into the chamber wall and minimizes the perturbation. Previous work has studied the pMRP in the frame of the Drude model, but it misses important effects like collision-…
Active plasma resonance spectroscopy (APRS) refers to a class of plasma diagnostic methods that use the ability of plasma to resonate at or near the electron plasma frequency for diagnostic purposes. The planar multipole resonance probe (pMRP) is an optimized realization of APRS. It has a non-invasive structure and allows simultaneous measurement of the electron density, electron temperature, and electron-neutral collision frequency. Previous work has investigated the pMRP through the Drude model and collision-less kinetic model. The Drude model misses important kinetic effects such as collisi…
Active plasma resonance spectroscopy (APRS) is a process-compatible plasma diagnostic method which utilizes the natural ability of plasmas to resonate on or near the electron plasma frequency. The Multipole Resonance Probe (MRP) is a particular design of APRS that has a high degree of geometric and electric symmetry. The principle of the MRP can be described on the basis of an idealized geometry that is particularly suited for theoretical investigations. In a pressure regime of a few Pa or lower, kinetic effects become important, which can not be predicted by the Drude model. Therefore, in thi…
We investigate in stationary regime on the linear plasma device OMT-2 the methods of plasma heating by electromagnetic waves, interaction of electromagnetic waves with magnetoactive plasma and plasma turbulence and transport processes in the trap. We use ultra-high frequency (UHF) contactless method to fill the open magnetic trap by plasma. We have proposed new method of open magnetic trap filling with plasma. Namely, plasma is injected in the trap along the magnetic field from independent stationary UHF source where plasma is formed in ECR regime. In this paper we present the results of inves…
Methods of plasma heating by electromagnetic waves, interaction of electro-magnetic waves with magnetoactive plasma, plasma turbulence and transport processes are investigated in the trap of the linear plasma device OMT2. An ultrahigh frequency (UHF) contactless method is used to fill the open magnetic trap by plasma. We propose a new method of open magnetic trap filling with plasma whereby plasma is injected in the trap along the magnetic field from an independent stationary UHF source. The source is located outside the trap and plasma formation in it takes place in the strongly nonuniform ma…
Fundamental studies of excitation and non-linear evolution of kinetic instabilities of strongly nonequlibrium hot plasmas confined in open magnetic traps suggest new opportunities for fine-tuning of conventional electron cyclotron resonance (ECR) ion sources. These devices are widely used for the production of particle beams of high charge state ions. Operating the ion source in controlled turbulence regime allows increasing the absorbed power density and therefore the volumetric plasma energy content in the dense part of the discharge surrounded by the ECR surface, which leads to enhanced bea…
In a grid-less Electron Cyclotron Resonance (ECR) plasma thruster with a diverging magnetic nozzle, the magnitude of the ambipolar field accelerating the positive ions depends of the perpendicular energy gained by the electrons. This work investigates the heating of the electrons by electromagnetic waves, taking their bouncing motion into account in a confining well formed by the magnetic mirror force and the electrostatic potential of the thruster. An electromagnetic Particle-In-Cell (PIC) code is used to simulate the plasma in a magnetic field tube. The code's Maxwell solver is based on a se…
Wake Perturbations in Laser- and Beam-Driven Plasma Wakefield Accelerators: A Symmetry-Based Multipole Classification
Extreme Light Infrastructure – Nuclear Physics (ELI-NP)（极光大设施核物理部）；Horia Hulubei National Institute for R&D in Physics and Nuclear Engineering (IFIN-HH)（霍里亚·胡利贝伊物理与核工程研发国家研究所）；INFN – Laboratori Nazionali di Frascati（意大利国家核物理研究所弗拉斯卡蒂国家实验室）
The three-dimensional particle-in-cell model NAM-ECRIS is used for investigation of how the DECRIS-PM Electron Cyclotron Resonance Ion Source is reacting to changes in the source magnetic configuration. The accent is made on changes in the magnetic field at the magnetic trap center, the minimum-B value. It is calculated that the optimal normalized value of the field is ~0.8, close to the experimental observations. The reasons for existence of the optimum are discussed. It is observed that the electron energies are increasing with the increased minimum-B values due to enhanced confinement of th…
