High-temperature Deuterium Plasma Research Articles

Effect of High-Temperature Pulsed Deuterium Plasma on the Structure and Mechanical Properties of the Surface of Cu–Ga and Cu–Ga–Ni Alloys

Effect of High-Temperature Pulsed Deuterium Plasma on the Structure and Mechanical Properties of the Surface of Cu–Ga and Cu–Ga–Ni Alloys

Multifractal analysis of high-temperature plasma irradiated tungsten surfaces

In this research, the irregular surface structure of 15 pure tungsten specimens that are irradiated respectively with 20, 40, 60, 80, and 100 shots of high-temperature deuterium plasma are under observation. The box-counting method is used to evaluate the scanning electron microscope (SEM) images taken from different locations within the same specimen. Obtained multifractal characteristics are then compared with the Fourier spectrum of stochastic relief. As a result, it is possible to determine the time dependence of surface damage with the box-counting method, but additional tests should be performed with the Fourier method to confirm this regularity. Besides, it has been studied further whether and how the fractal characteristics change with different magnifications within the same specimen. It was found that when selecting the appropriate magnification for SEM, X500 for a given specimen, the multifractal analysis of the arbitrarily selected image of surface damage well represents the average situation on the specimen.

Influence of Pulsed Beams of Deuterium Ions and Deuterium Plasma on the Aluminum Alloy of Al–Mg–Li System

The damage and structural state of the surface layer of Al–Li–Mg samples composed of Al–5% Mg–2% Li (wt %) under pulsed action of power streams of high-temperature deuterium plasma and high-energy deuterium ions in the Plasma Focus (PF) device have been investigated. The radiation power density was q ~ 106 W/cm2; the pulse duration was 50–100 ns. Pulsed thermal heating and rapid cooling is established to lead to the melting and solidification of a thin surface layer of the alloy for several tens of nanoseconds. At the same time, in the superheated surface layer of the alloy, microcavities of a spherical shape are formed which is associated with intense evaporation of lithium into micropores within the heated layer. Thermal stresses caused by abrupt heating, melting, and cooling of a thin surface layer of metal result in formation of microcracks in the near-surface zone of the samples. The evaporation by the power electron beam of the elements of the anode material of the PF device (copper and tungsten) and their subsequent deposition onto the irradiated surface of the investigated samples in the form of droplets of submicron size are noted. It is shown that the thermal and radiation-stimulated processes generated in the alloy under the action of pulsed energy fluxes in the implemented irradiation regime lead to the redistribution of elements in the surface layer of the aluminum solution, contributing to an increase in magnesium content and the formation of magnesium oxide on the surface.

Deuterium and helium retention in W with and without He-induced W ‘fuzz’ exposed to pulsed high-temperature deuterium plasma

In the present work, helium (He) was incorporated into tungsten (W) samples by inductively coupled plasma (ICP) source above the threshold of He-induced W ‘fuzz’ formation on W surface. Then, W samples with and without nano-structured W ‘fuzz’ were exposed to pulsed heat loads using deuterium (D) plasma in quasi-stationary high-current plasma gun QSPA-T. The pulse duration was 1 ms and number of pulses was varied from one to thirty to simulate ITER transient events with surface heat load parameters relevant to edge-localized-mode (ELM) impacts. The irradiation was performed below and above the W melting threshold. The D and He retention in each irradiated sample was measured by a method of thermal desorption spectroscopy. We examined the impact of (i) ELMs-like events and (ii) formation of He-induced nano-structured ‘fuzz’ on the D retention in W. We found that the D retention was the highest for samples irradiated by plasma gun above the melting threshold after thirty pulses. Moreover, the D retention after 10 pulses of deuterium plasma gun exposure was higher than that after stationary low-energy plasma exposure at sample temperature of either 600 or 700 K indicating the dominate influence of ELM's-like events on the D retention compared to normal operation regime. The D retention in W samples with the presence of He-induced W ‘fuzz’ was slightly smaller than without that after one pulse of plasma gun exposure with heat load below the W melting temperature. The W ‘fuzz’ was not disappear in this loading conditions, only the length and thickness of nano-structured W fibres were reduced by factors of ∼4 and ∼2, respectively. The He concentration in W with W ‘fuzz’ was decreased by a factor of about 3 after one pulse of plasma gun exposure. The results obtained give possibility to assess the particle retention in divertor areas subjected to high thermal loads at different operation regimes.

Structural Changes in the Vanadium Sample Surface Induced by Pulsed High-Temperature Deuterium Plasma and Deuterium Ion Fluxes

The structural changes in the vanadium sample surface are studied as functions of the conditions of irradiation by pulsed high-temperature deuterium plasma and deuterium ion fluxes in the Plasma Focus installation. It is found that processes of partial evaporation, melting, and crystallization of the surface layer of vanadium samples take place in the plasma flux power density range q = 108–1010 W/cm2 and the ion flux density range q = 1010–1012 W/cm2. The surface relief is wavelike. There are microcracks, gas-filled bubbles (blisters), and traces of fracture on the surface. The blisters are failed in the solid state. The character of blister fracture is similar to that observed during usual ion irradiation in accelerators. The samples irradiated at relatively low power density (q = 107–108 W/cm2) demonstrate the ejection of microparticles (surface fragments) on the side facing plasma. This process is assumed to be due to the fact that the unloading wave formed in the sample–target volume reaches its irradiated surface. Under certain irradiation conditions (sample–anode distance, the number of plasma pulses), a block microstructure with block sizes of several tens of microns forms on the sample surfaces. This structure is likely to form via directional crack propagation upon cooling of a thin melted surface layer.

Distribution of deuterium and hydrogen in Zr and Ti foil assemblies under the action of a pulsed deuterium high-temperature plasma

Deuteron and proton elastic recoil detection analysis is used to study the accumulation and redistribution of deuterium and hydrogen in assemblies of two high-pure zirconium or titanium foils upon pulsed action of high-temperature deuterium plasma (PHTDP) in a plasma-focus installation PF-4. It is noted that, under the action of PHTDP, an implanted deuterium and hydrogen gas impurity are redistributed in the irradiated foils in large depths, which are significantly larger than the deuterium ion free paths (at their maximum velocity to ~108 cm/s). The observed phenomenon is attributed to the carrying out of implanted deuterium and hydrogen under the action of powerful shock waves formed in the metallic foils under the action of PHTDP and/or the acceleration of diffusion of deuterium and hydrogen atoms under the action of a compression–rarefaction shock wave at the shock wave front with the redistribution of deuterium and hydrogen to large depths.

Hydrogen and deuterium distribution in tungsten foils irradiated with high-temperature deuterium plasma in H2O- or D2O-filled hermetic chambers

Processes of deuterium and hydrogen accumulation and redistribution are studied via the elastic recoil detection method with the help of a Plasma Focus (PF-4) setup. These processes proceed when high-temperature pulsed deuterium plasma acts on two external tungsten foils used as the main elements of hermetic chambers filled with distilled or heavy water and one internal tungsten foil inserted into an aqueous medium. It is established that, under the action of pulsed deuterium plasma on the heavy water-filled chamber, implanted deuterium atoms and those existing in the heavy water, as well as hydrogen contained in the tungsten foils, are redistributed over the entire thicknesses of the three foils. When the distilled water-filled chamber is irradiated with pulsed deuterium plasma, implanted hydrogen is observed across the whole thickness of the external tungsten foils with a depth distribution maximum. Hydrogen and deuterium reach their maxima on the foil surface immersed in liquid. The revealed phenomenon can be explained by the fact that chemical bonds in the heavy and distilled water are broken and, afterward, free hydrogen and deuterium atoms are transferred to tungsten foils under the action of intense shock waves excited in the chamber.

Low energy ion distribution measurements in Madison Symmetric Torus plasmas

Charge-exchange neutrals contain information about the contents of a plasma and can be detected as they escape confinement. The Florida A&M University compact neutral particle analyzer (CNPA), used to measure the contents of neutral particle flux, has been reconfigured, calibrated, and installed on the Madison Symmetric Torus (MST) for high temperature deuterium plasmas. The energy range of the CNPA has been extended to cover 0.34–5.2 keV through an upgrade of the 25 detection channels. The CNPA has been used on all types of MST plasmas at a rate of 20 kHz throughout the entire discharge (∼70 ms). Plasma parameter scans show that the ion distribution is most dependent on the plasma current. Magnetic reconnection events throughout these scans produce stronger poloidal electric fields, stronger global magnetic modes, and larger changes in magnetic energy all of which heavily influence the non-Maxwellian part of the ion distribution (the fast ion tail).

Effect of irradiation with pulsed fluxes of high-temperature deuterium plasma and fast ions on the structure of the surface layer of W-1% La2O3 alloy

Scanning electron microscopy, X-ray electron probe analysis, and X-ray phase analysis are used to investigate the surface structure of W-1% La2O3 alloy after irradiation with submicrosecond pulses of deuterium ions and high-temperature deuterium plasma in a Plasma Focus installation for simulation of a plasma disruption in the ITER tokamak. It is established that melting of the tungsten surface and formation of micro-cracks take place under irradiation with a power flux density up to 1012 W/cm2. Introduction of La2O3 particles in the alloy leads to the formation of complex La-W-O oxides with lower melting points, which results in the formation of a nonuniform structure affecting the high-temperature response of the material.

Deuterium accumulation in an assembly of nickel foils irradiated by high-temperature deuterium plasma

The accumulation of deuterium in an assembly of nickel foils by the pulsed irradiation of a deuterium plasma is studied. It is established that implanted deuterium is transferred to a much greater depth than that corresponding to the projective range of deuterium plasma ions with a maximum velocity of 108 cm/s. The maximum concentration (up to 4 at % deuterium) is observed in the second Ni foil. The observed phenomenon can be explained by the action of shock waves and concomitant stresses on the transport and redistribution of deuterium to greater depths.

Superdeep hydrogen and deuterium penetration into metals upon exposure to high-temperature hydrogen and deuterium plasma

Superdeep hydrogen and deuterium penetration into metals upon exposure to high-temperature hydrogen and deuterium plasma

Status and prospect of the JT-60SA project

The mission of the JT-60SA project is to contribute to the early realization of fusion energy by supporting the exploitation of ITER and research towards DEMO by addressing key physics issues associated with these machines. The JT-60SA will be capable of confining break-even equivalent class high-temperature deuterium plasmas at a plasma current I p of 5.5 MA and a major radius of ∼3 m lasting for a duration longer than the timescales characteristic of plasma processes, pursue full non-inductive steady-state operation with high plasma beta close to and exceeding no-wall ideal stability limits, and establish ITER-relevant high density plasma regimes well above the H-mode power threshold. Re-baselining of the project was completed in late 2008 which has been worked on since late 2007, where all the scientific missions are preserved with the newly designed machine to meet the cost objectives. The JT-60SA project made a large step forward towards its construction, which now foresees the first plasma in 2016. Construction of JT-60SA begins at Naka in Japan with launching the procurement of PF magnet, vacuum vessel and in-vessel components by Japan. In this year, the procurement of TF magnet, cryostat and power supply will be launched by Europe.

Influence of temperature and plasma composition on deuterium retention in refractory metals

Abstract Refractory materials are being considered potential candidates to build the first wall of the fusion reactor chamber. This work reports on the results of the study of tungsten and molybdenum metals exposed to high flux densities (∼1024 D/m2 s) and low temperature (Te ∼ 3 eV) deuterium plasmas in Pilot-PSI irradiation facility. The hydrogenic retention in poly-crystalline W and Mo targets was studied with 3He nuclear reaction analyses (NRA). The NRA results clearly show a two-dimensional radial distribution of the deuterium with a minimum at the center and a maximum close to the edge. These distribution correlates well with the thermal profile of the sample surface, where a maximum of ∼1600 K was measured at the center decreasing to ∼1000 K in the edges. A maximum deuterium fluence retention of 5 × 1015 D/cm2 was measured. The values of the retained fractions ranging from 10−5 to 10−6 Dretained/Dincident were measured with thermal desorption spectroscopy (TDS) and compares well with IBA results. Moreover, the presence of C in the plasma and its co-deposition increases the D retention in the region where a C film is formed. Both NRA and TDS results show no clear dependence of retention on incident fluence suggesting the absence of plasma related traps in W under these conditions.

Application of SSNTDs for measurements of fusion reaction products in high-temperature plasma experiments

The paper describes the application of SSNTDs of the PM-355 type to diagnostics of reaction products emitted from high-temperature deuterium plasmas produced in Plasma Focus (PF) facilities. Acceleration processes occurring in plasma lead often to the generation of high-energy ion beams. Such beams induce nuclear reactions and contribute to the emission of fast neutrons, fusion protons and alpha particles from PF discharges with a deuterium gas. Ion measurements are of primary importance for understanding the mechanisms of the physical processes which drive the charged-particle acceleration. The main aim of the present studies was to perform measurements of spatial- and energy-distributions of fusion-reaction protons (about 3 MeV) within a PF facility. Results obtained from energy measurements were compared with the proton-energy spectra computed theoretically. The protons were measured by means of a set of ion pinhole cameras equipped with PM-355 detectors, which were placed at different angles relative to the electrode axis of the PF facility.

Measurements of fusion-produced protons by means of SSNTDs

The paper describes applications of solid-state nuclear track detectors (SSNTDs) of the PM-355 type for diagnostics of fusion-reaction protons emitted from high-temperature deuterium plasmas. The results of our calibration studies of SSNTDs and fusion-proton measurements, carried out within two plasma-focus facilities (PF-360 and PF-1000), are presented. The main aim of those studies was to perform time-integrated measurements of 3 MeV fusion-reaction protons by means of ion-pinhole cameras equipped with the PM-355 detectors, placed at different angles relative to the axis of PF-360 and PF-1000 facilities.

Investigation of fusion-reaction protons from PF-discharges

The paper describes results of the recent measurements of fusion-reaction protons, which were performed within the large PF-1000 facility operated at IPPLM in Warsaw. The main aim of those studies was to perform time-integrated measurements of fast (about 3-MeV) protons by means of ion-pinhole cameras, which were equipped with nuclear track detectors (of the PM-355 type) and appropriate absorption filters. To determine the angular distribution of fusion protons the use was made of seven miniature pinhole cameras placed at different angles to the PF-1000 axis. The irradiated and etched detectors were analyzed with an optical microscope. To gain more information about fusion processes occurring inside the high-temperature deuterium plasma, the results were compared with those provided by other diagnostics. The most important result is a comparison of the fusion-reaction protons characteristics with the results of neutron and hard X-ray measurements. Fusion-reaction neutron measurements, which were performed by means of a few scintillation-probes placed at different distances from the PF facility electrode outlet, delivered some complementary information.

Plasmadynamic hypervelocity dust injector for the National Spherical Torus Experiment

The design and construction of a plasmadynamic device to accelerate dust to hypervelocities is presented. High speed dust will be used to measure magnetic field lines in the National Spherical Torus Experiment. The plasma gun produces a high density (ne≈1018cm−3) and low temperature (a few eV) deuterium plasma, ejected by J×B forces which provide drag on the dust particles in its path. The dust will be entrained by the plasma to velocities of 1–30km∕s, depending on the dust mass. Carbon dust particles will be used, with diameters from 1to50μm. The key components of the plasmadynamic accelerator are a coaxial plasma gun operated at 10kV (with an estimated discharge current of 200kA), a dust dispenser activated by a piezoelectric transducer, and power and remote-control systems.

Changes of internal properties of vanadium and structure of its surface under the effect of pulsed high-temperature deuterium plasma

The work presents experimental research of the influence of a pulse of high-temperature dense plasma on materials, which as are supposed, will be used in future thermonuclear power stations. The experiments were made on 4 kJ Plasma Focus installation. Such type of installations is capable to form pulse of axial plasma flows moving with velocity approximately 108 cm/s and plasma density is about 1018 cm−3. Pure vanadium was chosen in our researches, because it can be used as a basic element at the creation of low-activated alloys. We found that due to a pulse irradiation of vanadium by deuterium plasma, shock waves arises, which result in super-deep penetration of deuterium into a volume of the studied sample. This process is accompanied with the change of vanadium structure, the occurrence of pores in it, and changes of its mechanical properties. The break-away of vanadium particles from the backside surface of the sample and forming of craters were also observed.

Interaction of high temperature deuterium plasma streams and fast ion beams with stainless steels in dense plasma focus device

Interaction of deuterium plasma of streams and shock-waves (velocities up to 5×107 cm s−1) and fast ion beams (50–150 keV) generated in a dense plasma focus (DPF) device with low-activated austenitic steel, 25Cr12Mn20W, and ferritic steel, 10Cr9W, specimens positioned in the cathode part of DPF chamber has been investigated. If the power flux density of both types of irradiation is about q = 105–107 W cm−2, then ion implantation into a surface layer of the materials was observed. An increase of this parameter till q = 107–108 W cm−2 results in the so-called `detachment' effect (screening of the specimen surface by a cold plasma cloud). When the power flux density is increased up to q = 109–1010 W cm−2, the evaporated plasma cloud becomes of the same temperature as the plasma of the shock-wave, and melting and evaporation of material from the specimen surface appears to be very strong, thus the so-called `broken-implantation' takes place.

Diagnostics of high temperature deuterium and tritium plasmas by spectrometry of radiative capture reactions

The high resolution gamma ray spectrometry of the ground state radiative capture reactions d(p, γ) 3He, t(p, γ) 4He, d(t, γ) 5He and d(d, γ) 4He is proposed as a temperature diagnostic of energetic hydrogen plasmas. Counting rates for these reactions for temperatures and densities characteristic of current CTR research are estimated.