This article is devoted to measurement of proton beam parameters as one of the stages of proton injector for linear accelerator of compact neutron source DARIA development. Experimental results of ion source operating modes investigation are presented in this work. Gasdynamic electron-cyclotron resonance ion source GISMO is used as a proton injector. The plasma of the ion source is characterized as dense (the electron density is about 1013 cm–3) and hot (the electron temperature is about 30 eV). High volumetric energy input in plasma (up to 250 W cm–3) is achieved by the use of powerful “technological” gyrotron radiation to the plasma heating. The total ion beam current and beam emittance measurements were conducted during experiment at different facility parameters: inlet gas pressure, microwave power, magnetic lens current, and extraction voltage. The beam emittance was measured using pepper-pot method. The optimal ion source operation mode was found. The total beam current was above 100 mA at the proton beam energy of 40 keV, and the root-mean square normalized emittance was 0.21 π mm mrad. The obtained results of measurements are beneficial from the point of view of possibilities to control the ion source operating modes.

The key elements of the compact accelerator-driving neutron source (CANS) dedicated to academic research and industrial applications (DARIA) have been developed. A pulsed proton linear accelerator with an energy of 13 MeV, a current of 100 mA, a pulse length of 100 μs, and a repetition rate of 100 pulses/s is under development for the DARIA CANS. An improved version of the GISMO ion source has been developed to generate the beam. The parameters of the accelerator line consisting of the RF quadrupole (RFQ) linac and the drift tube linac (DTL) have been determined by numerical simulation. The parameters and model of a hybrid magnetic lens for beam focusing are presented. A Faraday cup for diagnosing a high-intensity beam has been manufactured and tested. The developed prototypes of the target assembly based on beryllium and mesitylene moderator have confirmed the correctness of the selected engineering solutions. The physical parameters of the neutron-guiding systems have been determined in terms of the maximum luminosity of the device at a good instrumental resolution.

This article is devoted to a stage of pulsed proton injector development which is conducted at the Gaponov-Grekhov Institute of Applied Physics, Russian Academy of Sciences. The result of electrostatic chopper numerical modeling is presented. It is a part of proton injector for linear accelerator of compact neutron source DARIA. A continuous wave mode gasdynamic electron cyclotron resonance ion source GISMO is used as an injector. The ion source has high volumetric energy input into plasma due to the use of “technological” gyrotron radiation to maintain and heat the plasma. The optimal geometric parameters (deflecting plates size and distance between them) of electrostatic chopper are determined during the calculations of proton beam propagation through the injector. The minimal voltage, which is enough for full beam deflection without losses inside chopper, is achieved at the optimal chopper geometry. Also, the output beam current dependence on chopper plate voltage is studied. The calculations allow for determining temporal characteristics of pulsed proton beam which escapes the injector at known pulse parameters of chopper voltage supply source.

Modern gyrotrons provide radiation in a wide range of frequencies and powers, which is used in a variety of areas of fundamental and applied research connected with the problem of plasma formation and heating.The A.V. Gaponov-Grekhov Institute of Applied Physics of the Russian Academy of Sciences is conducting a wide range of studies of gas discharge in a magnetic field under electron cyclotron resonance conditions. For these studies, gyrotron radiation with frequencies from 24 to 75 GHz and a peak power of up to 200 kW is used. The use of such high-frequency and powerful microwave systems has made it possible to obtain original results in the development of sources of intense ion beams of different types, to build compact and powerful neutron generators, to study fundamental kinetic processes in highly nonequilibrium plasma with hot electrons, and to simulate a number of astrophysical phenomena in the magnetospheres of the Earth and other planets.Studies of atmospheric pressure discharge in focused beams of gyrotron radiation with a frequency of up to 1 THz have shown significant prospects for creating of effective sources of extreme ultraviolet radiation with 13.5 and 11.2 nm wavelength based on such plasma, as well as plasma-chemical complexes, for example, for the decomposition of carbon dioxide and other compounds that require innovative methods for effective processing.The brief overview of the recent plasma studies using high power gyrotron radiation in frequency range from 24 GHz to 1 THz are presented, the future prospects of proposed technologies are discussed.

A method has been developed for studying the dielectric parameters of materials of plant origin i.e., high and low-lying peat, microcrystalline cellulose, lignin, as well as peat processing products using microwave radiation at a frequency of 2.45GHz. Based on this method, the dependences of the reflection coefficient on the thickness of the layer of the material under study were obtained. As a result, the values of dielectric constant and loss tangent of plant materials of various types were determined. These studies are focused on the development of complexes for microwave processing of organic fuel in the process of pyrolysis.

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.

The results of the ion source of the neutron generator upgrade, which makes it possible to operate in a CW mode, are presented. A magnetic trap consisting of permanent magnets (NdFeB) was developed. A 3-electrode extraction system equipped with a magnetic lens was used to extract the deuterium ion beam. Calculations are made for the formation of a deuterium ion beam with a current over 500 mA and an energy of 100 keV with practically no losses in the extraction system. Keywords: extraction system, magnetic trap, neutron generator, ion beam.

The use of the powerful millimeter wavelength range gyrotron radiation for the plasma heating allowed us to create a concept of a unique gasdynamic ion sources at IAP RAS. The gasdynamic electron cyclotron resonance (ECR) ion source is a type of the device in which the ionization efficiency is achieved primarily due to a high plasma density. Because of a high particle collision rate, the confinement is determined by a gasdynamic plasma outflow from a magnetic trap. Due to high efficiency of resonant heating, electrons gain energy significantly higher than that in inductively or capacitively coupled plasmas. As a consequence of such a parameter combination, the gasdynamic ECR plasma can be a unique source of low to medium charged ions, providing a high current and an ultimate quality of an ion beam. One of the most demanded directions of its application today is a development of high-current proton injectors for modern accelerators and neutron sources of different intensities.

Приводятся результаты первых экспериментов по изучению объемной генерации отрицательных ионов водорода при использовании плотной газодинамической плазмы ЭЦР-разряда, который поддерживался непрерывным микроволновым излучением гиротрона (28 ГГц/5 кВт). ЭЦР водородный разряд зажигался в вакуумной камере, помещенной в магнитное поле, создаваемое системой из двух последовательно соединенных магнитных ловушек. Была проведена оптимизация параметров системы с целью получения максимальной средней плотности тока отрицательных ионов j = 25 мА/см 2 . Определена область генерации отрицательных ионов, измерены зависимости плотности их тока от давления газа и мощности микроволнового излучения, показана перспективность дальнейшей оптимизации по напряжению экстракции.

The results of the first experiments on studying the volume production of negative hydrogen ions using a dense gasdynamic plasma of an electron cyclotron resonance (ECR) discharge sustained by continuous wave (CW) microwave radiation from a gyrotron (28 GHz/5 kW) are described. The ECR hydrogen discharge is ignited in a vacuum chamber placed in a magnetic field created by a system of two consecutive magnetic traps. The system parameters are optimized to obtain the maximum average current density of negative ions at the level of j = 25 mA/cm2. The study involves the determination of the negative ion production area, me-asurement of the current density dependences on gas pressure and microwave radiation power, and demonstration of potential optimization opportunities for extraction voltage.

We present the results of experimental studies of the intensity of vacuum ultraviolet self-radiation (VUV) of the discharge in hydrogen sustained in an open magnetic trap by the high-power radiation of a gyrotron (frequency f = 28 GHz and power P gyr = 5 kW) under conditions of electron cyclotron resonance (ECR) in the continuous regime. The optimum system parameters were determined for the generation of VUV radiation by the plasma of the ECR discharge. It was shown that the radiation power in the wavelength range λ = 120–160 nm reaches W = 0.75 kW, which corresponds to an efficiency of η = 20%.

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

The energy distribution of hot electrons escaping from the plasma of the ion source based on the discharge ignited under conditions of electron cyclotron resonance (ECR) was studied experimentally. The measurements were performed in wide ranges of microwave heating powers and neutral gas pressures. The facility under study is capable of providing uniquely high unit energy input into the plasma confined in the quasi-gas-dynamic (collisional) regime. In the course of the experiments, the diagnostics was performed of microwave radiation generated by the hot fraction of electrons escaping from the plasma. The regimes were discovered, in which the conditions are satisfied for the development of kinetic instabilities in the ECR discharge plasma. The energies are determined of electrons that cause the development of instabilities of this type, which are characterized by bursts of microwave radiation.

In the quasi-gasdynamic high-current ion source described in this work, the plasma is sustained by high-power millimeter-wave radiation under the electron cyclotron resonance (ECR) condition. In such facilities, it is possible to achieve high volumetric energy input of up to $250$ $W/cm^3$ and obtain pure proton beams with a minimum amount of impurities and molecular ions. Experiments conducted on the GISMO facility demonstrated the possibility of a proton beam formation with a current of $50$ mA and an extremely high ($99.9$\%) content of atomic ions.

Plasma parameters in a 28 GHz gasdynamic continuous electron cyclotron resonance discharge (ECR) with a high volumetric energy input were investigated with a Langmuir probe. The knowledge of the dependencies of plasma density and temperature on external parameters is useful for tuning the ECR source to the desired mode of operation. The design features of the plasma chamber and the configuration of the magnetic field made it possible to use the approximation a non-magnetized flat probe to calculate the temperature and electron density at various gas pressures and power of the heating microwave. A movable tungsten probe was used, allowing for studying plasma parameters along the magnetic field at various distances from the plasma electrode. At high powers, the electron density in the plug turned out to be close to the cutoff density (about 10 13 cm − 3). A fraction of warm ( > 30 eV) electrons, appearing at high powers, was found, which explains the formation of a pure proton beam in a number of experiments at the same facility. The abrupt increase in the temperature of the warm fraction with power was also found, which makes it of great interest to perform experiments on a multi-charged ions production in heavy gases.

This work describes improvement of the magnetic trap and beam-formation system of the GISMO (Gas-Dynamic Ion Source for Multipurpose Operation) electron-cyclotron-resonance ion source for its application as a proton injector, which is an integral part of the linear accelerator of a compact neutron source. The magnetic trap is improved and now uses an open design consisting of permanent magnets based on a Nd–Fe–B alloy. This design is optimized to accommodate the extraction system in the part of the plasma chamber with a larger inner diameter compared to the GISMO source. Then, the three-electrode beam-formation system is optimized. The design parameters of the system are developed in such a way that an additional solenoid-shaped magnetic lens can effectively produce a proton beam with a small divergence at the output. Computer simulation proves that this magnetic trap and the extraction system can be used as part of a proton injector for the DARIA project. The next steps in the construction of a proton source are discussed.

Electron energy distribution function (EEDF) is an important characteristic that defines the processes of plasma confinement and ionization. Understanding such processes is crucial for the proper tuning of ion sources. In the ECR plasma, the EEDF is significantly non-Maxwellian, and the exact shape remains still unknown. As the initial step towards the EEDF resolving, the energy distribution of the electrons lost from the magnetic mirror trap was directly measured in a wide range of neutral gas pressures and gyrotron powers along with bremsstrahlung spectra. A series of experiments were performed on the newly constructed Gasdynamic Ion Source for Multipurpose Operation (GISMO) facility allowing record-breaking specific energy input into the plasma. Obtained distributions showed unconventional behavior as the function of source parameters. The EEDF shape and the bremsstrahlung spectra showed a threshold qualitative change with the gyrotron power presumably as a result of the development of kinetic instabilities.

The results of the investigation of the dense ECR discharge hydrogen plasma flux formation in the magnetic field of a single solenoid are presented in this work. The transversal flux profile obtained at the optimal system parameters is shown. The possibility of the formation of homogeneous plasma fluxes with density of 750 mA/cm 2 and total current of 5 A is demonstrated. The results of the first experiments of the hydrogen ion beam extraction from the ECR discharge plasma in the single magnetic coil are presented. The record values of the ion current density higher than 1.5 A/cm 2 were obtained. The results of the research presented in this paper show the prospects of the proposed system for applications such as the neutral beam injector development for the plasma heating in the controlled fusion facilities.

Project of the proton accelerator-driven compact neutron source DARIA (Dedicated for Academic Research and Industrial Application) is developed in order to replace small and middle flux neutron sources based on the nuclear reactors. DARIA has a uniquely high ratio of efficiency to cost due to deep optimization of each key element of the system (proton injector and accelerator, target, neutron moderator and neutron instruments. A unique ECR ion source, developed at the IAP RAS, would be used as a proton beam injector. In such device the plasma is heated by the powerful 28 GHz gyrotron radiation, providing a record level of volumetric energy input for such systems over 100 W/cm(3). The high plasma density and the optimal electron temperature provide proton beams formation with a current of up to several hundred mA and an emittance that meets the requirements of modern accelerators. The paper discusses the advantages of using such an ion source, its scheme and design performance.