Alumina and 304 stainless steel were brazed with silver-copper-titanium filler+copper foil. The effect of adding copper foil to the filler on the microstructure of the alumina/304 joint was studied, and the reasons for the effect of adding copper foil with different thicknesses on the joint performance were also analyzed. The standard microstructure of alumina/304 joint with silver-copper-titanium+copper foil filler is alumina ceramic/copper compound with titanium and oxygen (3 : 3 : 1) (Cu3Ti3O) continuous layer+copper titanide (TiCu)/silver solid solution+copper solid solution/titanium compound with iron (1 : 2) (TiFe2)+iron-chromium compound/304 stainless steel. The added copper foil inhibits the diffusion of titanium elements, thereby reducing the formation of the brittle copper compound with titanium and oxygen (3 : 3 : 1) (Cu3Ti3O) and alleviating the residual stress. In addition, after adding copper foil, the copper solid solution is distributed in blocks in the joint, which also improves the plastic deformation ability of the joint. Under the synergistic effect of these two effects after adding copper foil, the joint strength is improved. When the copper foil was 200 mu m, the shear strength is 198.10 MPa. Alumina ceramic and 304 stainless steel were brazed using silver-copper-titanium+copper foil filler. The effect of copper thickness on the microstructure and properties of the joint was studied. The thickness of copper were 50 mu m, 100 mu m, 150 mu m, 200 mu m and 300 mu m. When the copper thickness is 200 mu m, the shear strength of the joint reaches 198.10 MPa.image

AbstractAlumina and 304 stainless steel were brazed with silver‐copper‐titanium filler+copper foil. The effect of adding copper foil to the filler on the microstructure of the alumina/304 joint was studied, and the reasons for the effect of adding copper foil with different thicknesses on the joint performance were also analyzed. The standard microstructure of alumina/304 joint with silver‐copper‐titanium+copper foil filler is alumina ceramic/copper compound with titanium and oxygen (3 : 3 : 1) (Cu3Ti3O) continuous layer+copper titanide (TiCu)/silver solid solution+copper solid solution/titanium compound with iron (1 : 2) (TiFe2)+iron‐chromium compound/304 stainless steel. The added copper foil inhibits the diffusion of titanium elements, thereby reducing the formation of the brittle copper compound with titanium and oxygen (3 : 3 : 1) (Cu3Ti3O) and alleviating the residual stress. In addition, after adding copper foil, the copper solid solution is distributed in blocks in the joint, which also improves the plastic deformation ability of the joint. Under the synergistic effect of these two effects after adding copper foil, the joint strength is improved. When the copper foil was 200 μm, the shear strength is 198.10 MPa.

The effect of initial heat-treated conditions on change of mechanical properties and microstructure evolution was investigated by caliber rolling of medium carbon alloy steel (ASTM 5140). Initial samples with two different kinds of microstructures of pearlite-ferrite and martensite were prepared, and then caliber rolling was conducted at 550 degrees C, 600 degrees C, 650 degrees C, respectively. It was found that the caliber rolling provides better strength-ductility balance and impact properties, when the rolling temperature is at 550 degrees C, the ultimate tensile strength of quenched steel can reach 1.3 GPa, and low-temperature impact energy of 140 J at -80 degrees C. In a word, the improvement of mechanical properties is attributed to the ultrafine elongated grain structures, dispersed nano-size carbides, and formation of distinct chromium segregation bands, furthermore, delamination crack is an effective measure to improve impact energy.

The heaviest actinide elements are only accessible in accelerator-based experiments on a one-atom-at-a-time level. Usually, fusion–evaporation reactions are applied to reach these elements. However, access to the neutron-rich isotopes is limited. An alternative reaction mechanism to fusion–evaporation is multinucleon transfer, which features higher cross-sections. The main drawback of this technique is the wide angular distribution of the transfer products, which makes it challenging to catch and prepare them for precision measurements. To overcome this obstacle, we are building the NEXT experiment: a solenoid magnet is used to separate the different transfer products and to focus those of interest into a gas-catcher, where they are slowed down. From the gas-catcher, the ions are transferred and bunched by a stacked-ring ion guide into a multi-reflection time-of-flight mass spectrometer (MR-ToF MS). The MR-ToF MS provides isobaric separation and allows for precision mass measurements. In this article, we will give an overview of the NEXT experiment and its perspectives for future actinide research.

In modern rare isotope facilities, ion cooling and bunching lies at the heart of the ion transfer along a low-energy beam line that consists of several differential pumping stages. We present a conceptual design of an ion guide as an alternative to the conventional linear Radio-Frequency Quadrupole (RFQ) for cooling and bunching rare isotopes. The ion guide is composed of stacked ring electrodes of varying apertures, to which a confining RF potential following a rectangular waveform is applied. The thicknesses of the rings and the gaps in between are varied accordingly to maximize the confining volume and to reduce ion losses. Ion transport within the ion guide is facilitated by a lower-frequency wave traveling on top of the higher-frequency confining field. The former is induced by locally adjusting the duty cycle of the rectangular waveform of the confining potential. Design parameters are first calculated by analytical studies and then optimized by ion trajectory simulations with SIMION®. The results show that the ion guide enables high ion transmission and produces well focused ion bunches. It will be used in the NEXT project—an experimental study of atomic masses of Neutron-rich EXotic nuclei produced in multi-nucleon Transfer reactions.

The effect of initial heat‐treated conditions on change of mechanical properties and microstructure evolution was investigated by caliber rolling of medium carbon alloy steel (ASTM 5140). Initial samples with two different kinds of microstructures of pearlite‐ferrite and martensite were prepared, and then caliber rolling was conducted at 550 °C, 600 °C, 650 °C, respectively. It was found that the caliber rolling provides better strength‐ductility balance and impact properties, when the rolling temperature is at 550 °C, the ultimate tensile strength of quenched steel can reach 1.3 GPa, and low‐temperature impact energy of 140 J at −80 °C. In a word, the improvement of mechanical properties is attributed to the ultrafine elongated grain structures, dispersed nano‐size carbides, and formation of distinct chromium segregation bands, furthermore, delamination crack is an effective measure to improve impact energy.

The penalized least squares (PLS) method with appropriate weights has proved to be a successful baseline estimation method for various spectral analyses. It can extract the baseline from the spectrum while retaining the signal peaks in the presence of random noise. The algorithm is implemented by iterating over the weights of the data points. In this study, we propose a new approach for assigning weights based on the Bayesian rule. The proposed method provides a self-consistent weighting formula and performs well, particularly for baselines with different curvature components. This method was applied to analyze Schottky spectra obtained in $$^{86}$$ Kr projectile fragmentation measurements in the experimental Cooler Storage Ring (CSRe) at Lanzhou. It provides an accurate and reliable storage lifetime with a smaller error bar than existing PLS methods. It is also a universal baseline-subtraction algorithm that can be used for spectrum-related experiments, such as precision nuclear mass and lifetime measurements in storage rings.

Isochronous mass spectrometry (IMS) of heavyion storage rings is a powerful tool for the mass measurements of short-lived nuclei. In IMS experiments, masses are determined through precision measurements of the revolution times of the ions stored in the ring. However, the revolution times cannot be resolved for particles with nearly the same mass-to-charge (m/q) ratios. To overcome this limitation and to extract the accurate revolution times for such pairs of ion species with very close m/q ratios, in our early work on particle identification, we analyzed the amplitudes of the timing signals from the detector based on the emission of secondary electrons. Here, the previous data analysis method is further improved by considering the signal amplitudes, detection efficiencies, and number of stored ions in the ring. A sensitive Z-dependent parameter is introduced in the data analysis, leading to a better resolution of ^34Ar^18+ and ^51Co^27+ with A/Z=17/9. The mean revolution times of ^34Ar^18+ and ^51Co^27+ are deduced, although their time difference is merely 1.8 ps. The uncorrected, overlapped peak of these ions has a full width at half maximum of 7.7 ps. The mass excess of ^51Co was determined to be -27332(41) keV, which is in agreement with the previous value of -27342(48) keV.

The interface characteristics, bending and impact behavior, as well as fracture characteristics of stainless steel clad plates fabricated by vacuum hot rolling at different rolling temperatures of 1100 degrees C, 1200 degrees C and 1300 degrees C are investigated in detail. The interface bonding strength is gradually increased with the increasing rolling temperature due to the sufficient diffusion behavior of alloy element. The bending toughness and impact toughness arc gradually decreased, while the bending strength increase with the increase of the rolling temperature, which is attributed to mechanisms of matrix softening and interface strengthening at high rolling temperature. Due to the weak interface at 1100 degrees C, the bending and impact crack propagation path was displaced by delamination cracks, which in turn lead to reduction in stress intensity of the main crack, playing an effective role in toughening the stainless steel clad plates. Moreover, the impact fracture morphologies of clad plates show a typical ductile-brittle transition phenomenon, which is attributed to the matrix softening behavior with the increasing rolling temperature.

A novel multilayer maraging/CoCrNi composite with good mechanical properties was successfully fabricated by a vacuum hot-rolling and aging treatment. The yield strength, tensile strength, uniform elongation, and fracture elongation reached 1,151, 1,380 MPa, 15.7, and 24% respectively, realizing the aim of synergistic strengthening–toughening by effectively improving the yield strength of the CoCrNi alloy and strain-hardening capacity of the maraging steel. The vacuum state, high rolling reduction ratio, and alloy element diffusion are beneficial in strengthening the clad interface. The good work-hardening capacity of the CoCrNi alloy compensates for the poor strain-softening behavior of the maraging steel, effectively delaying the premature localized necking of the multilayer composites. The strengthening–toughening mechanism of the multilayer maraging/CoCrNi composites is mainly attributed to the strong interface, nanoscale precipitation, and strain-induced twinning.

Isochronous mass spectrometry (IMS) of heavy-ion storage rings is a powerful tool for the mass measurements of short-lived nuclei. In IMS experiments, masses are determined through precision measurements of the revolution times of the ions stored in the ring. However, the revolution times cannot be resolved for particles with nearly the same mass-to-charge (m/q) ratios. To overcome this limitation and to extract the accurate revolution times for such pairs of ion species with very close m/q ratios, in our early work on particle identification, we analyzed the amplitudes of the timing signals from the detector based on the emission of secondary electrons. Here, the previous data analysis method is further improved by considering the signal amplitudes, detection efficiencies, and number of stored ions in the ring. A sensitive Z-dependent parameter is introduced in the data analysis, leading to a better resolution of $$^{34}$$ Ar $$^{18+}$$ and $$^{51}$$ Co $$^{27+}$$ with $$A/Z=17/9$$ . The mean revolution times of $$^{34}$$ Ar $$^{18+}$$ and $$^{51}$$ Co $$^{27+}$$ are deduced, although their time difference is merely 1.8 ps. The uncorrected, overlapped peak of these ions has a full width at half maximum of 7.7 ps. The mass excess of $$^{51}$$ Co was determined to be $$-27{,}332(41)$$ keV, which is in agreement with the previous value of $$-27{,}342(48)$$ keV.

Due to the capability of non-perturbing detection of a Schottky resonator, it is one of the significant measuring instrument for nuclear mass and decay experiments. A new data acquisition (DAQ) system for the Schottky resonator at the experimental cooler storage ring (CSRe) in Lanzhou and its accompanying preliminary data analysis program has been developed. During the beam time in Dec. 2016, the new system succeeded in continual collection of hundreds of data files, which met the requirement of the planned nuclear decay experiments. Also, the preliminary data analysis program could correctly display the frequency spectra of the acquired data.

A remote control system of data acquisition for the Schottky resonator at Experimental Cooler Storage Ring(CSRe) in Lanzhou has been assembled as a part of the experimental platform for nuclear mass and lifetime measurements. It is the combination of a data acquisition program and a data monitor program, both of which are exhibited in graphical user interface(GUI). It provides a number of key fea-tures to assist the users for adjusting the acquisition settings according to the experimental requirements. It is also characterized by the full utilization of a spectrum analyzer and an IQ recorder. The automatic acquisition of data files in both large size and large amount can be realized with the supplementation of an independent trigger system and a remote button pusher to overcome the intrinsic defect of the IQ record-er. It fulfills the requirements by the nuclear mass and lifetime measurements as well as other beam exper-iments using the Schottky resonator as the main detector at the CSRe.

F. M. Kröger, 2, 3, ∗ G. Weber, 2 M. O. Herdrich, 2, 3 J. Glorius, C. Langer, Z. Slavkovská, L. Bott, C. Brandau, 5 B. Brückner, K. Blaum, X. Chen, S. Dababneh, T. Davinson, P. Erbacher, S. Fiebiger, T. Gaßner, K. Göbel, M. Groothuis, A. Gumberidze, Gy. Gyürky, S. Hagmann, 4 C. Hahn, 2, 3 M. Heil, R. Hess, R. Hensch, P. Hillmann, P.-M. Hillenbrand, O. Hinrichs, B. Jurado, T. Kausch, A. Khodaparast, 4 T. Kisselbach, N. Klapper, C. Kozhuharov, D. Kurtulgil, G. Lane, C. Lederer-Woods, M. Lestinsky, S. Litvinov, Yu. A. Litvinov, B. Löher, 13 F. Nolden, N. Petridis, U. Popp, M. Reed, R. Reifarth, M. S. Sanjari, H. Simon, U. Spillmann, M. Steck, J. Stumm, T. Szücs, 14 T. T. Nguyen, A. Taremi Zadeh, B. Thomas, S. Yu. Torilov, H. Törnqvist, 13 C. Trageser, 5 S. Trotsenko, M. Volknandt, M. Weigand, C. Wolf, P. J. Woods, V. P. Shevelko, I. Yu. Tolstikhina, and Th. Stöhlker 2, 3 1Helmholtz-Institut Jena, Jena, Germany 2GSI Helmholtzzentrum für Schwerionenforschung GmbH, Darmstadt, Germany 3Institut für Optik und Quantenelektronik, Friedrich-Schiller-Universität, Jena, Germany 4Goethe-Universität, Frankfurt am Main, Germany 5Justus-Liebig Universität, Gießen, Germany 6Max-Planck-Institut für Kernphysik (MPIK), Heidelberg, Germany 7Institute of Modern Physics, Lanzhou, China 8Al-Balqa’ Applied University, Salt, Jordan 9University of Edinburgh, Edinburgh, United Kingdom 10Institute for Nuclear Research (Atomki), Debrecen, Hungary 11CENBG, CNRS-IN2P3, Gradignan, France 12Australian National University, Canberra, Australia 13Technische Universität Darmstadt, Darmstadt, Germany 14Helmholtz-Zentrum Dresden-Rossendorf (HZDR), Dresden, Germany 15St. Petersburg State University, St. Petersburg, Russia 16P.N. Lebedev Physical Institute, Moscow, Russia (Dated: May 12, 2020)

The electron capture process was studied for Xe$^{54+}$ colliding with H$_2$ molecules at the internal gas target of the ESR storage ring at GSI, Darmstadt. Cross section values for electron capture into excited projectile states were deduced from the observed emission cross section of Lyman radiation, being emitted by the hydrogen-like ions subsequent to the capture of a target electron. The ion beam energy range was varied between 5.5 MeV/u and 30.9 MeV/u by applying the deceleration mode of the ESR. Thus, electron capture data was recorded at the intermediate and in particular the low collision energy regime, well below the beam energy necessary to produce bare xenon ions. The obtained data is found to be in reasonable qualitative agreement with theoretical approaches, while a commonly applied empirical formula significantly overestimates the experimental findings.

Luminosity is a measure of the colliding frequency between beam and target and it is a crucial parameter for the measurement of absolute values, such as reaction cross sections. In this paper, we make use of experimental data from the ESR storage ring to demonstrate that the luminosity can be precisely determined by modelling the measured Rutherford scattering distribution. The obtained results are in good agreement with an independent measurement based on the x-ray normalization method. Our new method provides an alternative way to precisely measure the luminosity in low-energy stored-beam configurations. This can be of great value in particular in dedicated low-energy storage rings where established methods are difficult or impossible to apply.

Nuclear mass measurements by means of Schottky mass spectrometry critically rely on an accurate determination of revolution frequencies of the circulating ions in a storage ring. Such a harmonic retrieval problem is conventionally tackled via the periodogram of the Schottky data, where the ion peaks are identified and their spectral locations are obtained by fittings. However, the discrete frequency grid of the periodogram has unfortunately hampered a fine resolution of two closely spaced harmonics. We thereby propose a method based on the state space representation in the frequency domain to overcome this limit. Moreover, its frequency-selective merit has allowed the method to focus only on a narrow band and thus greatly reduced the computational cost while still retaining superb accuracy. With the real Schottky data from an isochronous-Schottky beam time at the experimental cooler-storage ring in Lanzhou, the accuracy of the retrieved harmonics is demonstrated to be around 1 ppm, as limited by the anisochronism effect of the ion optics.

A series of multilayer SUS304/Cr17 steels is successfully fabricated by roll bonding and subsequent annealing treatment. The results show that vacuum hot rolling can provide uniform layer thickness, a straight interface and strong metallurgical bonding, whereas cold-rolling deformation induces a laminate/network wave clad interface and weak bonding properties; this is attributed to the severe work-hardening behavior of the SUS304 layer and residual stress of the clad interface at the high cold-rolling reduction ratio, leading to a decrease of fracture elongation and interface bonding strength. Annealing treatment can effectively adjust the grain characteristics, texture distribution and alloying element diffusion behavior as well as dislocation plugging level. The grains change from a nanoscale laminate structure to an ultrafine fibrous structure and two-scale grain distribution with the increase of annealing temperature. Herein, high strength of 960 MPa and excellent fracture elongation of 28 pct can be obtained at the annealing temperature of 650 °C for 6 min. High-temperature annealing treatment can prompt the alloy element diffusion and relieve the residual stress of the cold-rolled clad interface. Moreover, bimodal grain distribution can be obtained by adjusting the annealing temperature, which is beneficial to strengthen and toughen multilayer steel.