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.

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.

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.

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.

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.

Using X-ray diffraction, there were determined the residual stresses on the surface of the AISI 310S stainless steel carrier tape used in manufacture of the second generation high temperature superconducting (2G HTS) wires at the National Research Center “Kurchatov Institute”, from delivery to deposition of the main buffer layer YSZ between the tape and the superconducting layer, and the residual stress in the buffer layer YSZ itself. The compressive stress of –0.8 GPa induced by rolling was found on the surface of the tape as-delivered. During processing, it varies from –0.5 to –1.1 GPa. At each stage, its depth distribution was found down to 10 μm, and the residual stresses caused by processing were determined. The residual stress in the YSZ layer deposited using the ABAD technology is compressive and amounts to –3.29 GPa. The layer has a defective single-crystal structure in type to radiation swelling with the unstressed lattice period of 5.1820 Å, 0.9% larger than in ordinary crystal. The results obtained are in agreement with the data of the earlier neutron diffraction study of residual stresses inside the carrier tape.

A new ECR ion source extraction system has been designed. The design is based on the extraction conditions of the JYFL 14 GHz ECRIS, and its performance is compared to the existing extractor via numerical modeling. The aim is to improve the formation and quality of high-intensity ion beams. The plasma and the puller electrodes shape were changed. The plasma electrode has a narrow tip extruding toward the puller. It causes the electric field to increase near the plasma meniscus and subsequent higher ion velocity growth rate, which leads to the beam space charge reduction at fixed current and acceleration voltage. The extractor was developed with the ion optical code IBSimu. The initial beam parameters were taken from the experimental data. The calculations showed that the new extraction system allows to increase the total extracted current without compromising the beam quality. The new design allows the beam formation optimization for lower extraction voltages overcoming the present space charge limit.

The advantages of using a gasdynamic proton source based on electron cyclotron resonance in a compact neutron source with a proton accelerator of the DARIA project are discussed. A gasdynamic source of protons has been shown to provide a beam with a current of ~100 mA and a duration more than 100 μs at a repetition rate up to 1000 pulse/s. Using the “pepper-pot” method, measurements of the emittance have been performed of a beam generated by a gasdynamic source of electron cyclotron resonance with two geometric configurations of electrodes forming the beam: “spherical” and plane-parallel. It is shown that the normalized 4-rms emittance for both variants of the beam-formation system electrodes in the extraction voltage ranges from 41 to 48 kV and does not exceed 2π mm mrad.

In this paper we report on a high current density ion beam profile diagnostics with a slit-based system as a reliable method, capable of high thermal load applications. The task arose in frames of a point-like neutron source development for neutron radiography. In previous research, it was suggested to construct such a system as a D-D neutron generator based on the high current gasdynamic ion source, which utilises the plasma of electron cyclotron resonance discharge sustained by powerful millimeter wave gyrotron radiation. This device is able to produce focused D+ beams with a characteristic diameter of 1 mm, total current above 100 mA, and current density at a level of several A/cm^2. Study of such intense beams profile to obtain the best focusing efficiency and minimize neutron producing area appeared to be a challenging task. The paper also demonstrates the possibility of fast neutron imaging with a point-like powerful neutron generator (neutron yield on the level of 10^10 1/s).