The STEMET 1108 grade (copper – tin – indium – nickel) of filler metal is currently used to braze bronze to tungsten plated with pure copper in divertors of the International Thermonuclear Experimental Reactor (or, ITER). Such filler metals are obtained as a result of rapid solidification of melt on a rapidly spinning copper wheel (melt spinning). When ingots are cast from which brazing ribbons are further produced, pores occur in them, through which indium evaporates. All this may affect the quality of the final product. The authors propose to alloy ingots with beryllium to stop the pore formation. This paper looks at the effect of beryllium on the quality of filler metal ingots and ribbons. The paper describes the results of a study that looked at the structural phase state of filler metals using electron microscopy and X-ray diffraction techniques, as well as a synchrotron radiation source. Both ingots and ribbons were found to have the same phase composition that consists of copper-based FCCsolid solutions and contains phosphide Cu3P. Beryllium containing ribbons are thinner than beryllium-free ribbons. In both cases, a dendritic structure is formed across the entire ribbon thickness. It is demonstrated that beryllium alloying in the range of 0.05 to 0.1 wt. % helps to significantly reduce the porosity of the initial ingots without compromising their structural phase state. In addition, it helps prevent the evaporation of indium. Hence, the difference in the structural phase state between beryllium alloyed and non-alloyed ribbons is insignificant and only concerns their dendritic structure, while there is no noticeable difference in their phase composition.

Two titanium alloys, OT4 and VT6-c, with a pseudo-α and α + β structure, respectively, were brazed using transient liquid phase (TLP) bonding. To obtain high strength joints an amorphous foil (Ti – 12Zr – 22Cu – 12Ni – 1.5 Be – 0.8V wt.%) was used. Based on microstructural studies and analysis of two- and three-component phase diagrams, the mechanism of the microstructural evolution of the brazed seams of titanium alloys OT4 and VT6-c is described. Brazing at 800 °C with exposure for 0.5 h leads to the formation of a heterogeneous structure consisting of Widmanstätten, eutectoid, and eutectic. Brazed OT4 and VT6-c joints with the presence of a eutectic layer in the centre show low mechanical properties; their ultimate strength lies in a range from 200 to 550 MPa. Increasing the brazing temperature to 840 °C and the exposure time to 2 h, leads to the disappearance of the brittle eutectic component from the seam. This structure typically consists of Widmanstätten with a small number of eutectoid fractions. Joints with the absence of a eutectic layer in the brazed seam demonstrate a strength equal to the base titanium alloys. In this case, failure occurs in the base metal. For brazed samples from the OT4 alloy, the tensile strength value is σb = 750 ± 3 MPa, and for samples from VT6-c, σb = 905 ± 3 MPa. This work was supported by Competitiveness Growth Programme of the Federal Autonomous Educational Institution of Higher Education National Research Nuclear University MEPhI (Moscow Engineering Physics Institute).

Methods of differential thermal analysis (DTA) and measurement of the melt viscosity are widely used in studying the properties of alloys at high temperatures. We have made an attempt to combine those two complementary methods of research. In contrast to the single-stranded Shvidkovskii viscometer, a bifilar suspension on two thermocouple wires is used in the proposed construction of the installation. The system based on the bifilar suspension provides using thermocouple in contact with the crucible with a sample, thus ensuring measurements of the crucible temperature like the measuring cell in DTA. The adjusting thermocouple located near the coil of a bifilar heater is used as a reference thermocouple. Since thermal analysis requires linear heating at a constant rate, and the viscosity is usually measured in a steady-state (steady-state) regime with long exposures at each measurement temperature, a series of dynamic viscosity determinations with a heating rate of 1, 2, 3 and 5 °C/min is carried out, the heating rates of 1 and 2 °C/min being approximately equal to the average heating rate under steady-state conditions. It is shown that when measuring in a dynamic mode at a heating rate up to 3 °C/min, the viscosity curves coincide with the measurement data in a steady-state mode, and the results of the thermal analysis (experimental setup) are consistent with the data of DTA (STA 409 setup). Results of measuring the logarithmic decrement of vibrations for Cu – 7.3% P alloy and data of thermal analysis are presented. Data of thermal analysis obtained on our experimental setup coincide completely with the DTA results obtained on a STA 409 unit. A model experiment carried out to explain the delay of growth of the logarithmic damping decrement at the beginning of melting and sharp decrease at the beginning of crystallization indicates to the effect of blocking free flow of the liquid melt component by the solid skeleton having a higher melting point.

Extensive studies are being carried out to develop a divertor (Divertor: a device in a thermonuclear reactor, intended for receiving of particle flows and radiation from the periphery of the plasma column. It is the most heavily loaded part of the reactor chamber surfaces with energy fluxes.) for tokamaks with a container for supplying liquid metal to the reception surface, with the construction of actual structures with high reliability and long service life. In this case, it is necessary to develop methods for joining dissimilar materials. In the transition section, molybdenum and steel (12Cr18Ni10Ti) pipes are joined by brazing. In this work, the method of producing a strong, heat resisting and hermetic joint between molybdenum and 12Cr18Ni10Ti corrosion-resisting steel is developed. Brazing is carried out using a paste based on CTEMET-1301 brazing alloy. The method of assembling the components in order to produce optimum gaps in brazing resulting in the homogeneous brazed joint without the formation of a brittle eutectic interlayer is developed. The brazed specimens were tested for heat resistance, leak tightness and service life at the given load. All the specimens withstood the tests. The mechanical properties of the brazed joints were determined by measuring the microhardness of the region of the welded joint and by shear tests. The results show that the strength characteristics depend strongly on the size of the gap between the brazed components. For the specimens assembled with the optimum gap the ultimatum shear strength was 500 ± 50 MPa.

As applied to the manufacture of the ITER first wall, a rapidly quenched copper-based filler metal for brazing chromium-zirconium copper alloy (CuCrZr) with beryllium (Be) at temperatures below 720 degrees C has been selected. The composition of the given filler metal has been optimized by varying the concentration of alloying elements, such as Sn, Ni, and P. improving the filler functional properties and quality. Rapidly quenched ribbon-type filler metals with various contents of alloying elements were investigated by differential thermal and X-ray phase analysis, atomic force microscopy, and scanning electron microscopy. To improve the casting performance of the filler metal and obtain high-quality ribbons, the kinematic viscosity of brazing alloys with various contents of Ni, Sn, and P has been investigated. The chromium-zirconium copper alloy has been brazed with Be using the filler metals obtained (by furnace brazing and fast brazing by passing an electric current).Based on the results of complex research, an ultrafast (quenching rate of similar to 10(5 degrees) C/s) quenched brazing alloy STEMET 1101M (Cu-9.1Ni-3.6Sn-8.0P, in weight percent) has been selected and manufactured in the form of a ribbon that is 50 mm in width and 50,urn in thickness.An experimental mock-up of the ITER first wall has been made in D.V. Efremov SRIEA by rapid brazing (by passing a current) using the filler metal STEMET 1101M. The brazed joint has withstood 15 000 cycles of thermocycling under a thermal load of 0.5 to 5.9 MW/m(2) without breaking.

The work shows the main results on the development at NRNU MEPhI of rapidly quenched amorphous and nanocrystalline ribbon-type and powder brazing filler metals based on Al, Cu, Ni, Ti and Zr and their application for brazing of a wide range of materials in nuclear, thermonuclear, aerospace, automotive, aircraft and other industries: from steels, alloys and refractory metals to various ceramics without metallization of their surfaces.

A search for the 10Li formation was performed in missing mass spectra measured in stopped pion absorption reactions 14C(π −, pt)X and 14C(π −, dd)X. Three excited states of 10Li were found. The broad state with a resonance energy of E R = 6.13 ± 0.11 MeV has the highest excitation energy in comparison with levels observed earlier.

A method for calibrating a multilayer spectrometer using α particles is presented. This spectrometer is composed of successive semiconductor Si(Li) detectors and is used for precision detection of long-range charged particles (p, d, and t) with energies of ∼100 MeV. The factors affecting the accuracy of calibration are analyzed. This method is shown to guarantee high accuracy in measuring charged-particle energies.

. The superheavy hydrogen isotopes 4 H and 5 H have been investigated in the stopped pion absorption on 9 Be. Three states of 4 H were proposed in the reaction channel 9 Be( π { - } , dt) X . Four states of 5 H were proposed in the reaction channels 9 Be(π { - } , pt) X and 9 Be(π { - } , dt) X . The excited states of 5 H can decay into free nucleons.

The structure of levels of superheavy hydrogen isotopes 4–6 H is analyzed on the basis of a record statistics of experimental data on the absorption of negatively charged pions by light nuclei. Qualitatively new experimental data are obtained for the spectroscopy of the superheavy hydrogen isotopes 5 H and 6 H. Peaks due to four resonance states of 5 H are observed in the missing-mass spectra for the reaction channels 9 Be( π − , pt ) X and 9 Be(π − , dd ) X . A structure that is associated with four resonance states of 6 H is observed in the missing-mass spectra for the reaction channels 9 Be(π − , pd ) X and 11 B(π − , p 4 He) X . On the basis of the results presented for ground-state parameters, it can be concluded that the binding energy of superheavy hydrogen isotopes decreases as the number of neutrons increases. Excited levels of the isotopes 5 H and 6 H are observed for the first time. On the energy scale, all of these states lie above the threshold for decay to free nucleons.

An experimental search for the superheavy hydrogen isotope 6 H was conducted through studying the absorption of stopped π − -mesons by 9 Be and 11 B nuclei. A structure in the missing mass spectrum caused by the resonance states of 6 H was observed in three reaction channels, namely, 9 Be(π − , pd )X, 11 B(π − , d 3 He)X, and 11 B(π − , p 4 He)X. The parameters of the lowest state E r =6.6±0.7 MeV and Γ=5.5±2.0 MeV ( E r is the resonance energy with respect to the disintegration into the triton and three neutrons) are evidence that 6 H is a more weakly bound system than 4 H and 5 H. Three excited states of 6 H were observed. Their resonance levels ( E 1 r =10.7±0.7 MeV, Γ 1 r =4±2 MeV, E 2 r =15.3±0.7 MeV, Γ 2 r =3±2 MeV, and E 3 r =21.3±0.4 MeV, Γ 3 r =3.5±1.0 MeV) are energetically capable of disintegrating into six free nucleons.

The formation of the 5 H superheavy hydrogen isotope was experimentally sought in the reactions induced by stopped π − mesons absorbed by 9 Be nuclei. Peaks in missing-mass spectra were observed in two reaction channels, 9 Be(π − , pt )X and 9 Be(π − , dd )X, and were attributed to the 5 H resonance states. The lowest state has parameters Er =5.5±0.2 MeV and Г=5.4±0.5 MeV [ E r is the resonance energy measured from the (triton + two neutrons) threshold]. Therefore, 5 H is bound more weakly than 4 H. Excited states of 5 H were also observed. All three resonance levels ( E 1r =10.6±0.3 MeV, Г 1r =6.8±0.5 MeV; E 2r =18.5±0.4 MeV, Г 2r =4.8±1.3 MeV; E 3r =26.7±0.4 MeV, Г 3r =3.6±1.3 MeV) can decay into five free nucleons.

The influence of the charge collection time in silicon detectors on the accuracy of charged particle energy measurements is considered. Calculation and experimental data show that this parameter exerts a significant effect on the selection of the shaping time constants τ of multilayer silicon spectrometers. This is especially important for systems based on Si(Li) detectors, which are designed for detecting long-range charged particles (p, d, t) with energies E ∼ 100 MeV. It is shown that the time constant τ = 1.5 μs ensures a high accuracy in the absolute energy calibration.

The excited states of the ``halo'' nucleus, ${}^{11}\mathrm{Li}$, have been investigated by means of the pion capture reaction, $^{14}C({\ensuremath{\pi}}^{\ensuremath{-}},pd{)}^{11}\mathrm{Li}$. Excited states have been identified at $1.02\ifmmode\pm\else\textpm\fi{}0.07$, $2.07\ifmmode\pm\else\textpm\fi{}0.12$, and $3.63\ifmmode\pm\else\textpm\fi{}0.13\mathrm{MeV}$. The continuum part of the ${}^{11}\mathrm{Li}$ missing mass spectrum is found to contain a major component which is consistent with ${}^{11}\mathrm{Li}$ breakup into one of the ${}^{9}\mathrm{Li}$ excited states and two strongly correlated neutrons.

An automated electronic system for measuring basic electric parameters (reverse currents, strip and interstrip capacitances) of strip semiconductor detectors is described. An operational amplifier with a complex feedback loop is used in the measuring channel of the system, thus combining the functions of current and capacitance measurements. A 32-channel system provides for measurements of reverse currents from 0.1 to 500 nA and capacitance above 0.03 pF.