Ion Optical System Research Articles

Design and performance test of discharge chamber and grid for multi-mode ion thrusters

In view of the application requirements of electric propulsion system for China’s asteroid deep space exploration mission, the overall scheme is designed, an ion thruster prototype model is established by using a four-ring-cusp field discharge chamber, 30-cm beam current extraction diameter three-grid ion optics system. Reasonableness and compatibility of discharge chamber and grid design are verified experimentally and theoretically . The test results are shown below. The ion thruster can operate steadily over an input power envelope of 277–3120 W, thrust increases linearly from 9.9 to 117.2 mN, specific impulse rises from 1269 to 3492 s, the beam divergence angle drops from 30.7° to 26.8° and stabilizes above a certain power value, the thrust vector angle is less than 1.5° and beam flatness parameter is greater than 0.75 at different operating points. The maximum percentage reduction in grid gap aberration is 90% with the strain relief molybdenum mounting ring thermal design. This research provides a reference for multi-mode ion thruster design and in-orbit engineering applications.

Ion-Optical System with Ballistic Focusing of a Powerful Deuterium Atom Beam Injector for Plasma Heating

Ion-Optical System with Ballistic Focusing of a Powerful Deuterium Atom Beam Injector for Plasma Heating

Development of high-voltage negative ion based neutral beam injector for fusion devices

A prototype of a powerful high-voltage neutral beam injector, based on acceleration of negative hydrogen ions and their neutralization, is under development at Budker Institute of Nuclear Physics (BINP). The design of the BINP high-voltage injector includes several innovative components, important for injector operation stability and overall efficiency. It includes a multi-aperture long-pulse surface-plasma negative ion source with thermostabilized grid, ithe magnetic system with concaved field lines in the ion-optic system (IOS) and the distributed cesium deposition system. The injector scheme incorporates a wide-aperture low-energy beam transport (LEBT) section, plasma target for negative ionneutralization, and recuperators of non-neutralized ions. Several test stands were constructed at BINP for injector component studies. This paper describes the results of experiments on negative ion beam production, transport through LEBT, ion acceleration to energy up to 240 keV and transport through the high voltage beam transport (HEBT) section to the distance ∼10 m from the source. The parameters of the transported beam, which were measured at several points along the beam line and at the beam dump calorimeter, are presented. The beam transport efficiency as a function of various ion source, LEBT and HEBT parameters is measured and compared with the calculated values. The results dof plasma neutralization target study are presented as well.

Investigation of the ion-optical system of an ion thruster with a microwave plasma generator with a power of up to 10 W

A method for improving the tactical and technical characteristics of ion thrusters while maintaining the specified electrical characteristics of the power source is proposed. This method is considered on the example of increasing the accelerating voltage on the electrodes of the ion-optical system of the prototype ion thruster. The method is based on the creation of a dielectric layer on the electrodes of an ion-optical system. Experimental and theoretical studies of the operation of the ion-optical system as part of the ion thruster have shown that the presence of a layer of dielectric coating on the electrodes allows you to achieve a steady-state voltage of up to 740 V, and in the absence of this layer-no more than 570 V. The calculated values of the thrust for the prototypes of ion thrusters were 14 μN with an ion-optical system having a dielectric layer and 8.4 μN a dielectric on the electrodes. The presence of dielectric coatings on the electrodes of the ion-optical system makes it possible to improve the characteristics of ion thrusters without significant design changes.

Miniature source of accelerated ions with focusing ion-optical system

The paper describes a small-sized accelerated ion source developed on the basis of the KLAN-10M technological source. Record values of the ion current density (j ≈ 95 mA/cm2) were obtained, which made it possible to use this source for problems of deep correction of the shape of X-ray optical elements. Formation of small beam (FWHM ∼ 1.5 mm) with a Gaussian distribution of the ion current along the output aperture without cut-off diaphragms is the main feature of this source. A focusing ion-optical system makes it possible to change the beam size depending on the distance and the value of the accelerating voltage. Thus, this source allows deep final correction of the shape errors of the surfaces of optical elements and bringing it to subnanometer accuracy in terms of the RMS parameter in the range of spatial frequencies up to 1.3∗10−3μm−1 for the case of conductive and up to 9.5∗10−4μm−1 for the case of dielectric materials. The special design of the neutralizing unit allows to fully compensate for the positive ion flux, avoiding heating the sample to 50 degrees Celsius at a distance of 10 mm from the source, which is a necessary condition in a number of tasks. The influence of the thermal cathode-neutralizer on the ion density distribution of the beam is shown and explained.

The impact of neutralizer-free ignition of a radio frequency ion thruster on the lifetime of the ion optics system

In the initial stage of a radio frequency ion thruster (RIT) ignition, an influx of electrons is required from an external source into the discharge chamber and ionization of the neutral gas propellant. A neutralizer-free method for Townsend breakdown discharge ignition based on Paschen’s law was developed in this study. The feasibility of the ignition method was confirmed by performing thousands of ignition experiments. Metallic Molybdenum (Mo), pyrolytic graphite (PG) and Zr[Formula: see text]Ti[Formula: see text]Cu[Formula: see text]Ni[Formula: see text]Be[Formula: see text]alloy acceleration grids were prepared, and ignition-induced damage on the grids was investigated. A field-emission scanning electron microscope was used to inspect surface damage on the grids after multiple ignitions and to analyze the influence of the ignition method on the lifetime of the ion optical system. Grid materials for space missions that require multiple RIT ignitions (10[Formula: see text] should be high-strength blocks that are resistant to sputtering corrosion and high temperature.

Epigenetics, 1-Carbon Metabolism, and Homocysteine During Dysbiosis.

Although a high-fat diet (HFD) induces gut dysbiosis and cardiovascular system remodeling, the precise mechanism is unclear. We hypothesize that HFD instigates dysbiosis and cardiac muscle remodeling by inducing matrix metalloproteinases (MMPs), which leads to an increase in white adipose tissue, and treatment with lactobacillus (a ketone body donor from lactate; the substrate for the mitochondria) reverses dysbiosis-induced cardiac injury, in part, by increasing lipolysis (PGC-1α, and UCP1) and adipose tissue browning and decreasing lipogenesis. To test this hypothesis, we used wild type (WT) mice fed with HFD for 16 weeks with/without a probiotic (PB) in water. Cardiac injury was measured by CKMB activity which was found to be robust in HFD-fed mice. Interestingly, CKMB activity was normalized post PB treatment. Levels of free fatty acids (FFAs) and methylation were increased but butyrate was decreased in HFD mice, suggesting an epigenetically governed 1-carbon metabolism along with dysbiosis. Levels of PGC-1α and UCP1 were measured by Western blot analysis, and MMP activity was scored via zymography. Collagen histology was also performed. Contraction of the isolated myocytes was measured employing the ion-optic system, and functions of the heart were estimated by echocardiography. Our results suggest that mice on HFD gained weight and exhibited an increase in blood pressure. These effects were normalized by PB. Levels of fibrosis and MMP-2 activity were robust in HFD mice, and treatment with PB mitigated the fibrosis. Myocyte calcium-dependent contraction was disrupted by HFD, and treatment with PB could restore its function. We conclude that HFD induces dysbiosis, and treatment with PB creates eubiosis and browning of the adipose tissue.

An Ion-Optical Circuit of a Small-Sized Mass-Spectrometer for the Isotope Analysis of Hydrogen–Helium Mixtures

We discuss an ion-optical system (IOS) of a mass spectrometer designed for isotopic measurements of light gases, containing a magnetic prism with plane-parallel pole tips and two sector-wise, cylindrical-capacitor identical in geometry, symmetrically located relative to the prism. The relationships between the geometric parameters of the capacitors and the prism are given, which are necessary to ensure achromatic focusing of the ion beam in the plane of the detector receiving slit. We assessed numerically the effect of IOS aberrations on the mass resolution of the IOS and determined the optimal emittance of the ion beam at the source output, which enables achieving a resolution at the level of 3000–3500 with an output slit of the ion source of approximately 50 μm, high transmittance of the mass analyzer, small dimensions of the magnetic prism, and a moderate total length of the central ion trajectory (less than 1 m). The IOS is characterized by a high dispersion in masses, which is much larger than the dispersion of conventional sector magnetic mass spectrometers of the same dimensions. The IOS consists of simple geometry elements, which reduces the costs of its implementation and makes the mass spectrometer technologically advanced and convenient to set up and operate.

Geometric Aspects of Optimizing the Acceptance of a Static Mass Analyzer

The axial aberration of the ion-optical system of a static mass analyzer is one of the main factors limiting the transmission and sensitivity of the instrument. We described an algorithm for selecting the optimal collimating system for a mass analyzer, which makes it possible to decrease this aberration effectively, with minimal loss in the intensity of the mass spectral lines. The algorithm is based on the representation of the considered aberration in the phase space as an ellipse and the optimal approximation of this aberration ellipse by a polygon with a given number of vertices. In the absence of constraints, the solution of the corresponding optimization problems is in phase polygons generated by regular polygons inscribed in a unit circle or circumscribed around a unit circle with the same number of vertices. After that, the unit circle along with the polygons is “stretched” to the size of the specified aberration ellipse along its main axes. Additional freedom of the rotation of the original polygon around the center of the unit circle can be used to position auxiliary slits of the collimating system more conveniently.

Optimization of Vertical Acceptance of the Static Mass Analyzer

Axial aberration of the ion-optical system of a static mass analyzer is one of the factors limiting the transmittance and sensitivity of the device because of a need in significantly decreasing the vertical component of the ion beam emittance to get the required mass spectral resolution. We described an algorithm for selecting the optimal collimating system of the mass analyzer, which effectively decreases the contribution of axial aberration with minimal loss of the intensity of mass spectral lines.

Nanoscale ion implantation using focussed highly charged ions

We introduce a focussed ion beam (FIB) based ion implanter equipped with an electron beam ion source (EBIS), able to produce highly charged ions. As an example of its utilisation, we demonstrate the direct writing of nitrogen-vacancy centres in diamond using focussed, mask-less irradiation with Ar8+ ions with sub-micron three dimensional placement accuracy. The ion optical system was optimised and is characterised via secondary electron imaging. The smallest measured foci are below 200 nm, using objective aperture diameters of 5 and 10 µm, showing that nanoscale ion implantation using an EBIS is feasible.

Measuring the Emittance of a Charged-Particle Beam in a Small Linear Accelerator

A “non-contact” method for measuring the emittance of a corpuscular flow extracted from the Penning ion source of a small linear charged-particle accelerator has been developed and tested. The emittance is calculated by minimizing the difference between the theoretically calculated and experimentally measured beam sizes in the ion-optical system of the accelerator. The dimensions are measured during photographic recording of a luminous trace of a corpuscular flow in the ion-optical system. The results of applying the non-contact method for measuring the emittance of a particle beam flow are presented.

Computational and experimental investigation of a weakly diverging ion beam source

This paper presents the idea of space debris removal by the ion beam. The main part of this idea is the ion source on the board of the spacecraft. The ion beam should be narrow, with small half-angle of divergence - about 2°. Angle of divergence means that in there are 95% of ions in this angle. Authors show the concept of the slotted ion optic system. Based on calculation, the construction of the ion optic was designed and tested as part of the laboratory model of the ion source. The results obtained during the experimental testing verified the possibility of using an ion source of such type as an ion injector, which can be installed on board a next-generation spacecraft for the removal of space debris objects.

Experimental Study on the Effects of Discharge Chamber Length on 5 cm Radio-Frequency Ion Thruster

For keeping microgravity level of microgravity and space science satellites, a kind of electric thruster, the radio-frequency ion thruster (RIT) has been designed and applied. The RIT produces thrust through ionizing neutral particles in the discharge chamber and extracting ions by the ion optics system. The length of discharge chamber affects the ionization of neutral particles as well as the performance of RIT. In this paper, an experimental study has been carried out for analyzing the influence of discharge chamber length. In the experiment, the RIT-5 with various discharge chamber lengths, 27.6 mm, 30.0 mm, 31.9 mm, 35.5 mm, 40.0 mm, has different performances under the same condition. With the same radio frequency power and propellant flow rate, the RIT-5 has the optimal performance in beam current and efficiency when the discharge chamber length is 30.0 mm or 31.9 mm.

Update of ion-optical system of neutral beam of Tokamak à Configuration Variable.

An injector of fast deuterium atoms for plasma heating was designed and installed at the Tokamak à Configuration Variable (TCV). The neutral beam can deliver 1 MW power to the plasma in 2 s pulses. An ion beam of the injector is formed by a triode multislit ion-optical system with spherical electrodes which provide ballistic focusing. Tests at TCV revealed that the total angular divergence of the neutral beam across the slits exceeded the expected value more than twice. It was finally established that this increase in divergence was caused by the asymmetry of the chamfers at the slit edges of the plasma electrode. The redesigned shape of the slits of the plasma grid together with precise machining significantly improved the beam quality. Experimental testing proved that the neutral beam profile in the direction across the grid slits became very close to the expected value.

Deuterium ion beam formation in a vacuum arc discharge system with a deuterated cathode

The formation of deuterium ion beams in a vacuum arc with a deuterium-saturated zirconium cathode was studied using a MevvaV.Ru vacuum arc ion source. The multi-aperture ion-optical system of the source was replaced by a string ion-optical system to measure and compare the current–voltage characteristics and current density distributions over the beam cross-section obtained with the two systems. The study shows that the string system with a deuterated cathode provides a beam current 1.4–1.5 times higher than the multi-aperture system does, all other things being equal, and that the beam divergence with the string system is also higher. The total pulse current of deuterium ions in the beam ranges to about 1 A.

Features of using plasma flows to compensate the aerodynamic drag of mini-satellites moving in the ionosphere

The possibilities of using plasma flows formed in electric jet engines (EJE) are considered. One of the variants of the EJE construction are ion sources with multi-cell ion-optical systems used to compensate the aerodynamic drag of mini-satellites in the Earth’s ionosphere with the aim of ensuring long-term operation of the latter at low flight altitudes (∼180–220 km). The analysis of methods of simulation of the operation of such engines together with air intakes under ground conditions is given. The possibility of using plasma-ion sources producing molecular beams of nitrogen or air ions with low (orbital) flight speeds as a source of the free flow in the simulations is considered. A source with volumetric ionization of the working gas and electron oscillation in the magnetic field in a chamber between the walls held at the cathode potential and a large multi-cell aperture of the ion–optical system is used to create the flow. The results of the studies of the operation of a plasma–ion engine (PIE) together with air intake obtained by the gas-dynamic simulation method are presented. The possibility of a high performance of the engine under non-standard conditions is shown. It is found that a stable operation of the PIE can be realized at pressures of 6⋅10−5–10−4 Torr in its chamber, which is important for matching the engine with the air intake.

Conceptual design of the heavy ion beam probe diagnostic for the T-15MD tokamak

The conceptual design of the heavy ion beam probe (HIBP) for T-15MD tokamak (R = 1.5 m, a = 0.67 m, Bt = 2 T, Ipl = 2 MA) is presented. The location of the HIBP injection and detection points is chosen based on the probing beam trajectory calculations. Observation area covers the whole radial interval 0 < r < a for Bt = 1 T, Ipl = 1 MA with the beam energy Eb <260 keV for Tl+ probing ions. It allows to measure two-dimensional maps of plasma parameters in an area which covers a large fraction in the upper right quarter of the plasma cross-section. In order to provide the measurements in a wide range of plasma density, high intensity long-focusing probing beam is needed. To develop such a beam a high voltage test bench is designed. It will allow to study the ion-optics system of the HIBP injector and the properties of the thermionic emitters and their lifetime.

Mechanical analysis of C/C composite grids in ion optical system

The ion thruster is an engine with high specific impulse for satellites and spacecrafts, which uses electric energy to boost the spacecraft. The ion optical system, also known as gate assemblies which consist of acceleration and screen grids, is the key component of the ion thruster. In this paper, the static mechanical properties of the C/C composite grids are evaluated based on the structural design. Representative volume element (RVE) is adopted to simplify the braded composite structure as a continuum material. The dynamical behavior of the 100mm ion thruster optics in the launch environment (1 000g shock-load) is numerically modeled and simulated with the half-sine pulse method. The impact response of the C/C and molybdenum gate assemblies on the stress distribution and deformation is investigated. The simulated results indicate that the magnitudes of the normal displacement of the composite grids subject to the uniformly distributed load are on the same level as molybdenum grids although the normal stiffness of the composite grids is much smaller. When subject to impact loading, the stress distribution in the C/C composite grids is similar to molybdenum grids while the stress magnitude is much smaller. This finding shows that the C/C gate assemblies outperform molybdenum grids and meet the requirement of long lifetime service in space travel.

Rapid MALDI‐TOF molecular imaging: Instrument enhancements and their practical consequences

A new high performance linear MALDI-TOF mass spectrometer provides both high spatial resolution and high speed. This instrument employs a new ion optics system with a grounded ion source and efficient transfer and detection of ions over a broad mass range. This provides very high sensitivity, precision, and an extended dynamic range for both positive and negative ion detection. Here we demonstrate the capabilities of this system by imaging pancreatic tissue samples from rats and mice.