High-power Ion Beam Research Articles

Nanostructuring in a system consisting of a thin metal film on a dielectric substrate under irradiation with a high-power ion beam of nanosecond duration

The formation of metal nanoparticles in a system containing a thin metal film on a dielectric substrate and irradiated with a high-power ion beam of nanosecond duration is studied. The nanoparticle formation mechanism is discussed.

R&D progress at JAEA towards production of high power and large-area negative ion beams for ITER

This paper reports the progress of R&D towards the ITER neutral beam (NB) system at the Japan Atomic Energy Agency (JAEA) during 2004–2006. In the accelerator development, an H− ion beam of 146 A m−2 was accelerated up to 836 keV in a vacuum insulated accelerator with five acceleration stages. This is the first production of a high power density beam at MeV range energy, which is more than twice as high as those of the existing NB systems for large experimental reactors such as JT-60U and LHD. The ITER NB system requires a high voltage (HV) bushing as an electric feedthrough to the vacuum insulated accelerator from the gas insulated power supply. A full-size (1.56 m in diameter and 0.292 m in height) insulator ring made of alumina ceramic has been successfully fabricated for HV bushing, as a result of the technological development of a new cold iso-static press.Long pulse operations of JT-60U negative ion sources with a large extraction area of 0.45 × 1.1 m2 are in progress. From the two ion sources, D− ion beams of 21 A (90 A m−2), 320 keV have been produced for 21 s. As a consequence, injection of 3.2 MW D0 beams was achieved. Thus, the long pulse operation of the negative ion based NB system has been demonstrated with multi-tens of ampere of D− ions extracted from the ion extraction area relevant to the ITER NB design (0.6 × 1.5 m2). For long pulse operation of such powerful beams, the negative ion uniformity over the wide extraction area is an essential issue to avoid excess power loading on the accelerator grids. By adopting a new magnetic configuration with the so-called ‘tent-shaped filter’, the uniformity of the JAEA 10 A source (extraction area: 0.13 × 0.22 m2) was improved by 8%, which fulfilled the ITER requirement.

Effects of irradiation parameters on metal surface erosion by pulsed ion beams

Potential application of high-power ion beams of submicrosecond and microsecond durations with the initial particle energy from 50 to 1000 keV and power density 107–109 W/cm2 to ensure metal surface erosion are investigated. Evaporation is treated as a major erosion mechanism and the erosion coefficient is taken as an efficiency indicator. Dependences of the erosion coefficients of several metals on beam parameters obtained via calculations using a technique based on the solution of thermal conductivity equation with phase transitions are presented. The ion species, their initial energy, current pulse duration and power density are used as the beam parameters controlling the result of irradiation.

Erosion resistance of refractory alloys modified by ion beams

The objective of the present research is the critical analysis of test results, dedicated to the effect of ion-beam irradiation conditions upon the sand particle erosion resistance of refractory alloys. Gas turbine engine compressor blades, produced with titanium alloys (VT9 and VT18U) as well as refractory steels (EP866sh and EP718ID) were used as the study objects. The ion implantation and irradiation of targets for the high-power pulsed ion beam were accomplished by means of Delta, Raduga-2 and Temp-M accelerators. The irradiation conditions were varied within the following ranges: B, N, C, La, Pd, Sm and Hf ion implantation — E = 30–80 keV (ion energy), j = 40–5·10 3 μA/cm 2 (ion current density), f = 30 Hz (pulse frequency), D = 10 16–2 10 19 ion/cm 2 (irradiation dose); high-power pulsed ion-beam irradiation — ions of carbon (60–70%) and protons, E = 250–300 keV, j = 40–200 A/cm 2, τ = 50 ns (pulse duration), n = 3–10 pulses (number of pulses). After irradiation some targets were subjected to vacuum annealing for 2 h at their service temperature. Erosion tests of initial and irradiated blades were performed in vacuum on the gas-dynamical branches with a sand load to 200 mg/mm 2 at the particle velocity of 200 m/s. The average size of the sand particles was equal to 80–120 μm. The target surface state prior to and after erosion tests was studied by Auger electron spectroscopy, scanning electron microscopy, transmission electron microscopy, optical metallography and X-ray structural analysis. The fracture surface was studied by optical and electron fractography. The test results showed that the erosion resistance of blades, subjected to the ion-beam irradiation with post-process vacuum annealing at the optimum conditions, could be increased by 20–200% depending on the type of implanted ion. This positive effect of ion-beam treatment on the erosion resistance of refractory alloy blades is evidently connected with strengthening the material in the surface layer with thickness of 1 μm (ion implantation) up to 10 μm (high-power pulsed ion-beam irradiation). Using electron fractography it was found, that the erosion resistance increase was associated both with the type change of craters created during beginning stages of the erosion tests and with the decrease of erosion rate due to the surface microrelief formed during the fracture incubation period (“start–inertial” mechanism of fracture).

High-energy-density physics researches based on heavy ion accelerator and pulse power devices

Plasmas at high density and/or high-temperature state are produced using pulse power devices. Dense, cylindrically evolving plasmas are produced using pulse- power-driven exploding discharges in water. Shock-heated, high-temperature plasmas are produced also in a compact pulse power device. In contrast to the pulse-powered plasmas, properly moderated high-power ion beams can make a well-defined plasma over a wider range of density–temperature space. Their advantages and attainable parameter region are comparatively discussed as a driver for making the high-energy-density states.

Erosion of the GaAs target under irradiation by a high-power pulsed ion beam

The results of examination of the GaAs-target erosion under irradiation by a high-power pulsed ion beam are reported. In the experiments, use was made of a high-power pulsed ion source with the following parameters: ion energy — 250 keV, target current density — 350 A/cm2, pulse duration — 80 ns, target energy density — up to 7 J/cm2. The target erosion coefficient and its dependence on the number of successive pulses are measured. It is found that the surface roughness parameter is increased with the number of successive beam pulses. A regular structure of surface relief is observed to form in the case where the number of pulses > 20–40.

Superconductivity in MgB2 films synthesized by ablation from high-power ion beam

MgB2 thin films with Tc=19K were fabricated by the ion ablation technique utilizing a high-energy pulsed ion beam. A target remains pure MgB2 after ablation, proving the excellent capability of ablation by the high-power ion beam. Chemical compositions of the deposited material, however, may vary with positions of the substrates from the beam axis. X-ray diffraction patterns exhibit only (001) and (002) peaks, which indicate a c-axis orientation of the films. Scanning electron microscopy images show a possible growth of single crystals with hexagonal shape and 1μm size.

Iron distribution in the implanted silicon under the action of high-power pulsed ion and laser beams

The results of the investigation of the phase composition, microstructure and dopant depth distribution in silicon layers implanted with iron ions and annealed with pulsed ion and laser beams are given. X-ray diffraction data indicate the phase transition FeSi→β-FeSi2 with increasing of the pulse energy density. After ion implantation and pulsed treatments, silicon layers have a cellular structure related with the low solubility of iron in silicon. Depending on the iron atomic concentration, either segregation of the dopant to the surface or diffusion into silicon takes place. This dependence is explained by rapid diffusion of iron in liquid silicon and increase of the dopant distribution coefficient when increasing dopant concentration. The results of the computer simulation agree well with experimental data on the iron depth distribution and give the segregation co-efficient close to 1 at the highest dopant concentration.

Energy spectra of high-power ion beams measured with a pile of thin films on FLASH Ⅱ

The preliminary experimental results obtained for the energy spectra of high-power ion beam(HPIB) with a pile of thin films on FLASH Ⅱ accelerator are reported. Code was developed to calculate the theoretical energy-loss of proton and C ion beams transmited through the Mylar films with different thickness. T he apertures of Faraday Cups are covered with Mylar films of different thicknes s, and then the signal attenuations can be recorded with oscilloscope. The energ y spectra of HPIB and the diode voltage are obtained according to the signal al lenuations. The diode voltage measured with a pile of thin films agrees with the voltage measured with a differential ring. And the ion number versus time curv e was given. In addition, the ion energy of HPIB is also measured with Thomson spectrometer and time of flight method and the results agree with those measured with a pile of thin films.

Preliminary Research Results for the Generation and Diagnostics of High Power Ion Beams on FLASH II Accelerator

The preliminary experimental results of the generation and diagnostics of high-power ion beams of FLASH II accelerator are reported. The high-power ion beams presently are being produced in a pinched diode. The method for enhancing the ratio of ion to electron current is to increase the electron residing time by pinching the electron flow. Furthermore, electron beam pinching can be combined with electron reflexing to achieve ion beams with even higher efficiency and intensity. The anode plasma is generated by anode foil bombarded with electron and anode foil surface flashover. In recent experiments on FLASH II accelerator, ion beams have been produced with a current of 160 kA and an energy of 500 keV corresponding to an ion beam peak power of about 80 GW. The ion number and current of high power ion beams were determined by monitoring delayed radioactivity from nuclear reactions induced in a 12C target by the proton beams. The prompt γ-rays and diode bremsstrahlung x-rays were measured with a PIN semi-conductor detector and a plastic scintillator detector. The current density distribution of ion beam were measured with a biased ion collector array. The ion beams were also recorded with a CR-39 detector.

Radiation-induced change of polyimide properties under high-fluence and high ion current density implantation

Polyimide (PI) films were implanted with 40-keV Ar+ and 80-keV Ar(2+) ions in a fluence range of 5.0*10^14-1.5*10^17 cm-2 at ion-current densities of 1-16 uA*cm2. It is shown that the conductivity of the samples rises with the ion-current density at a fixed fluence. Electrophysical parameters of the polyimide change stepwise with the implantation fluence when it exceeds a certain value. The change of electrical parameters of the implanted PI correlates with that of the optical and paramagnetic characteristics. The phenomenon of complete volatilisation of argon implanted with an energy of 40 keV due to surface heating and disordering under the high-power beam is found. It is shown that the change of ion charge and energy at constant beam-power density causes only a quantitative change in the polymer characteristics. A model of PI alteration and carbonised phase formation, taking into account the action of the high-power ion beam and the peculiarities of PI chemical structure, is developed to explain the observed effects. Implantation at high ion-current density can be suggested as an efficient practical means to control polymer conductivity and other parameters

Features of the morphology, defect substructure, and phase composition of metal and alloy surfaces upon high-power ion beam irradiation

Optical metallography, transmission electron microscopy, and phase analysis were used to study the mechanisms of structural transformations in the surface layer of thickness Δ h≈0.2 μm for single crystals and polycrystals of metals and alloys irradiated with high-power ion beams (HPIB's). Characteristic features of the formation of the surface relief and variations in phase constitution and defect substructure of pure metals (Ni, Mo) and single-phase (Mo–Re, Ni 3Al) and double-phase (V–ZrO 2) alloys have been found in relation to the ion beam power density Q=(1–10)×10 7 W/cm 2. Common features and distinctions in the formation of the microstructure of metallic materials belonging to different classes under HPIB irradiation have been revealed. Based on the predictions of a numerical simulation of the time-dependent temperature fields and the melting and evaporation processes in the surface layer, the mechanisms for the phase-structure modification of metal and alloy surfaces are analyzed.

Preliminary research results for generation and application of high power ion beams on FLASH II accelerator

Preliminary results for the generation and application of the high power ion beam(HPIB) on the FLASH Ⅱ accelerator are reported. The structure and principle of the pinch reflex ion beam diode are introduced. The equation of parapotential flow is corrected for the reduction of diode A-K gap due to the motion of cathode and anode plasma. The HPIB peak current of ～160kA is obtained with a peak energy of ～500keV. Experimental investigations of generating 6—7MeV quasi-monoenergetic pulsed γ-rays with high power ion(proton) beams striking 19F target are presented. In addition, the results of the thermal-mechanical effects on the material irradiated with HPIB, which are applied to the simulation of 1keV black body radiation x-rays, are also discussed.

The Intense Pulsed Ion Beam Treatment and the Titanium Nitride Coating of Hard Alloy for Cutting Tool

The aim of this work was to investigate adhesion increasing of titanium nitride coating deposited at hard alloy tool’s surface pretreated by intense pulsed ion beam of different energy density. Two alloys were treated by high-power pulsed ion beam of 1÷3.75 J/cm2 energy density. Analyzing the data obtained from tunnel microscopy, X-ray spectrum and measurements of surface relief geometry characteristics, such as roughness and profile length, we came to the following conclusion. First, the value of energy density of ion beam plays the key role in the formation of the relief and phase structure of the surface. Second, these two characteristics are almost independent of the initial characteristics of the irradiated alloys.Also, the article touches the results of scratch-test of the titanium nitride coating. The results demonstrate changes in wearing and destruction mode of the coating deposited at the tool treated by ion beam.

Modeling of the Interaction of High-Power Pulsed Ion Beams with Cadmium-Mercury-Tellurium Semiconductor Targets

A mathematical model for describing the interaction between high-power pulsed ion beams and semiconductor CdxHg1–xTe (cadmium–mercury–tellurium or CMT) targets is developed, the results of numerical simulation are reported, and the comparison with experiment is performed.

Formation of cubic silicon carbide layers on silicon under the action of continuous and pulsed carbon ion beams

The structure and infrared absorption of cubic silicon carbide (β-SiC) layers produced by the continuous high-dose implantation of carbon ions (C+) into silicon (E=40 keV and D=5×1017 cm−2), followed by the processing of the implanted layers with a high-power nanosecond pulsed ion beam (C+, τ=50 ns, E=300 keV, and W=1.0–1.5 J/cm2), are investigated. Transmission electron microscopy and electron diffraction data indicate the formation of a coarse-grained polycrystalline β-SiC layer with grain sizes of up to 100 nm. A characteristic feature of such a layer is the dendritic surface morphology, which is explained by crystallization from the melt supercooled well below the melting point of β-SiC.

A Matrix Carbon Detector for Measuring the Energy Flux of a High-Power Beam of Hydrogen Ions

A matrix detector consisting of small calorimeters based on УПВ-1 pyrolytic carbon is described. The detector allows measurements of the spatial distribution of the energy flux of a high-power hydrogen ion beam to be taken over its cross section. Each calorimeter occupies an area of 4 cm2, and the area of its working body is 0.25 cm2. An unambiguous relation between the heat flux value, the irradiation time, and the calorimeter temperature is established by calculations. The calorimeter measurement error was estimated at ∼4%, and the spread of the sensitivity coefficients between the calorimeters was 5–6% (1σ). The detector was used to measure the distribution of the energy flux of hydrogen ions over the cross section of the “scanned” beam 10 cm in diameter from a high-current accelerator of the НГ-12И facility.

Fatigue strength of metals and alloys modified by ion beams

The objective of the present research is the critical analysis of test results, dedicated to the effect of ion-beam irradiation conditions upon the fatigue strength of metallic materials. The shaped specimens, simulating the gas turbine engine blade operation and directly the blades, produced of titanium and nickel alloys as well as refractory steels by machining method are used as the study objects. The arc-pulsed ion implantation and irradiation of targets by the high-power pulsed ion beam were realised by means of Raduga-2, Temp-M and MUK accelerators. The irradiation conditions were varied within the following ranges: La, B, Sm and Hf ion implantation— E=30–80 keV (ion energy), j=1–5 mA/cm 2 (ion current density), f=30 Hz (pulse frequency), D=10 16–5×10 17 ion/cm 2 (irradiation dose); high-power pulsed ion beam irradiation—ions of carbon (60–70%) and protons, E=120–300 keV, j=30–200 A/cm 2, τ=50–100 ns (pulse duration), n=3–20 pulses (number of pulses). After irradiation, some targets were subjected to vacuum annealing for 2 h at their service temperature. Fatigue tests of initial and irradiated samples and blades were performed in air at the operating temperatures (450–650 °C) on the magneto-strictional vibrobanches with the loading frequency to 5000 Hz and low-frequency vibrobenches (50–80 Hz). The target surface state prior to and after tests was studied by electron Auger spectroscopy, scanning electron microscopy and X-ray structural analysis. The fracture surface was studied by optical and electron fractography. The test results showed that the endurance limit of samples and blades, subjected to the ion-beam irradiation with the post-process vacuum annealing at the optimum conditions, could be increased by 30–180% depending on an alloy type. Using the electron fractography, it was stated that the fatigue strength increase was associated both with the crack nucleation mechanism change and its growth rate deceleration. The extremely high endurance limit values were observed for patterns and VT8M titanium alloy blades with sharp edges after the high-power ion beam irradiation (pulse number: 15–20 at not high current density, j=60±10 A/cm 2) and vacuum annealing at 500 °C for 2 h.

The effect of crater creation on the fatigue strength and corrosion resistance of steels and titanium alloys irradiated by high-power pulsed ion beams

The effect of high-power pulsed ion-beam (HPPIB) irradiation and various methods of the surface treatment on the crater creation phenomenon (cratering) was examined with the use of Auger electron spectroscopy, X-ray diffraction analysis, and scanning electron microscopy. The crater distribution density, sizes and shape, along with the microhardness and chemical composition inside and outside them were determined. It was shown that cratering on the surface of refractory alloys is due to the cathode material erosion and the nonstability in the physical and chemical state of the irradiated targets. The samples were treated with HPPIB. The irradiated samples were subjected to fatigue and corrosion tests. It was established that cratering leads to catastrophic fracture of the irradiated targets under the cycle load. For example, as a result of crater creation, the fatigue strength of VT18U alloy was decreased from 380 to 240 MPa. In this case the nucleation of fracture lies near the craters. Furthermore, the titanium alloys irradiated by HPPIB are subjected to pitting corrosion in seawater. It was shown that according to the test results, adjacent and dent-shape craters are the most dangerous defects under the cycle load.

Research on materials surface layers element structure formation under combined treatment with pulsed ion beams of different powers

The investigation results are presented for some processes occurring at different stages of strong adhesion coating and modified layer creation with the use of high-dose implantation and deep diffusive doping of elements under pulsed energetic impact. The investigations have been carried out on installation, providing the possibility of combined materials treatment with pulsed ion beams of power density ranged from 10 3 to 10 8 W/cm 2. The facility includes an accelerator of high-power ion beams and sources of repetitively-pulsed metal ion beams and metal plasma flows. The possibility of the application of a high power ion beam pulsed energetic impact to intensify mass transfer and increase the depth of doping for a preliminary implanted impurity has been demonstrated. The results are presented concerning the formation of high quality thin coatings with wide buffer layers determining their adhesive strength by means of the method of combined treatment using a high power ion beam.