Effects of Metal Absorber Thermal Conductivity on Clear Plastic Laser Transmission Welding

In our previous study, metals have been used as absorbers in the clear plastic laser transmission welding. The effects of metal thermal conductivity on the welding quality are investigated in the present work. Four metals with distinctly different thermal conductivities, i.e., titanium, nickel, molybdenum, and copper, are selected as light absorbers. The lap welding is conducted with an 808 nm diode laser and simulation experiments are also conducted. Nickel electroplating test is carried out to minimize the side-effects from different light absorptivities of different metals. The results show that the welding with an absorber of higher thermal conductivity can accommodate higher laser input power before smoking, which produces a wider and stronger welding seam.The positive role of the higher thermal conductivity can be attributed to the fact that a desirable thermal field distribution for the molecular diffusion and entanglement is produced from the case with a high thermal conductivity.

Energy calibration of HPGe detector using the high-energy characteristic γ rays in 13C formed in 6Li + 12C reaction

An 6 Li+89Y experiment was conducted at the Laboratori Nazinali di Legnaro,INFN,Italy.The 550μg/cm^2 thick^89Y target was backed on a 340μg/cm^2 thick 12C foil.The severalγrays in the experiment with energies higher than 3000 keV can most likely be ascribed to the transitions in the 13C nuclei,which can be formed through various interactions between the 6 Li beam and the 12C foil.The high-energy properties ofγrays in 13C are employed for energy calibrating HPGe detectors,especially for the>3000 keV region,which is impossible to reach by common standard sources(152Eu,133Ba,etc.).Furthermore,γ-γand particle-γcoincidence measurements were performed to investigate the formation of 13C.

Comparative study of photoionization of atomic hydrogen by solving the one-and three-dimensional time-dependent Schrödinger equations

We develop a numerical scheme for solving the one-dimensional(1D)time-dependent Schrödinger equation(TDSE),and use it to study the strong-field photoionization of the atomic hydrogen.The photoelectron energy spectra obtained for pulses ranging from XUV to near infrared are compared in detail to the spectra calculated with our well-developed code for accurately solving the three-dimensional(3D)TDSE.For XUV pulses,our discussions cover intensities at which the ionization is in the perturbative and nonperturbative regimes.For pulses of 400 nm or longer wavelengths,we distinguish the multiphoton and tunneling regimes.Similarities and discrepancies between the 1D and 3D calculations in each regime are discussed.The observed discrepancies mainly originate from the differences in the transition matrix elements and the energy level structures created in the 1D and 3D calculations.

Stirring brazing of dissimilar Al/Mg alloy without flux in air

AZ31B magnesium alloy and 2024 aluminum alloy were successfully jointed at aid of mechanical stirring with Sn-Zn-Al filler metal. The microstructure, fracture morphologies, and mechanical properties of joint were investigated. The results show that Mg-Al intermetallic compounds can be avoided by the process. But, a small quantity of porosity is found in the joint. The sheafing strength of joint interface adjacent to magnesium alloy is 35.4 MPa for formation of Mg-Sn intermetallic compounds, which is about 46 % of that of filler metal. While, the shearing strength of joint interfaces adjacent to aluminum alloy is 70.4 MPa for formation of Zn-Sn-Al solid solution, which is about 92 % of that of filler metal.

Lifetime measurements in 138Nd

Lifetimes of the 2_(1)^(+),4_(1)^(+),7_(2)^(-),10_(2)^(+),12_(2)^(+),and 14_(1)^(+) states in 138 Nd populated via the 123 Sb(19 F,4n)138 Nd fusion–evaporation reaction were measured with the recoil distance Doppler shift technique in combination with the differential decay curve method.The B(E2;2_(1)^(+)→0_(1)^(+))value fit well with the systematic trend in the Nd isotope chain and Grodzins rule,which proved that 138Nd is a transitional nucleus.

Microstructure and properties of joint for stirring brazing of dissimilar Al/Mg alloy during heating processes

In this paper, 2024 Al alloy and AZ31B Mg alloy were brazed with aid of stirring without flux in air. The effects of the brazing temperature on microstructure and shear strength of the joint were investigated. The diffusion zone is found at joint interface near Al base metal, which consists of Al-Zn-Sn solid solution. At the same time, continuous intermetallic compounds （IMCs） phase and broken ones are found at joint interface near Mg base metal, which mainly consists of the Mg2Sn phase. With the increase of the brazing temperature, the shear strength at the joint interface near A1 base metal rises gradually. On the contrary, that of the joint interface near Mg base metal obviously decreases.

Measurement of the^2H(^7Be,^6Li)^3He reaction rate and its contribution to the primordial lithium abundance

In the standard Big Bang nucleosynthesis （SBBN） model, the lithium puzzle has attracted intense interest over the past few decades, but still has not been solved. Conventionally, the approach is to include more reactions flowing into or out of lithium, and study the potential effects of those reactions which were not previously considered. 7Be（d, 3He）6Li is a reaction that not only produces 6Li but also destroys 7Be, which decays to 7Li, thereby affecting 7Li indirectly. Therefore, this reaction could alleviate the lithium discrepancy if its reaction rate is sufficiently high. However, there is not much information available about the 7Be（d, 3He）6Li reaction rate. In this work, the angular distributions of the 7Be（d, 3He）6Li reaction are measured at the center of mass energies Ecm=4.0 MeV and 6.7 MeV with secondary 7Be beams for the first time. The excitation function of the 7Be（d, 3He）6Li reaction is first calculated with the computer code TALYS and then normalized to the experimental data, then its reaction rate is deduced. A SBBN network calculation is performed to investigate its influence on the 6Li and 7Li abundances. The results show that the 7Be（d, 3He）6Li reaction has a minimal effect on 6Li and 7Li because of its small reaction rate. Therefore, the 7Be（d, 3He）6Li reaction is ruled out by this experiment as a means of alleviating the lithium discrepancy.

Low-lying states of 92,93Nb excited in the reactions induced by the weakly-bound nucleus 6Li near the Coulomb barrier

Excited states of odd-odd nucleus 92Nb and odd-A nucleus 93Nb were populated in the 6Li+ 89Y reaction with an incident energy of 34 MeV. The processes that produce 92,93Nb and can be measured by a combination of light charged particle and gamma ray measurements are discussed. Twenty new transitions are observed and eight new levels are constructed in 92Nb, and in addition two new transitions are added to the level scheme of 93Nb. Using shell model calculations, the low-lying structure of 92Nb is investigated and compared with the experimental results.

High spin states in ^(71)Ga

Excited states in the odd-A nucleus 71Ga have been studied via the ^(70)Zn(7Li,a2n)^(71)Ga fusion-evaporation reaction with incident beam energies of 30 and 35 MeV.The level scheme is established up to spin I^(n)=(29/2^(+))and an excitation energy-6.6 MeV.A previously known sequence built on the 9/2^(+) state is extended as a novel rotational band originating from the v(8^(2)_(9/2)alignment.Furthermore,a negative-parity sequence Is also reported.The observed energy levels of Ga have been interpreted in the framework of the nuclear shell model(SM).

Systematic study of the Woods-Saxon potential parameters between heavy-ions

Experimental elastic scattering angular distributions of 11B,2C,and 16O+heavy-ions are used to studythe Woods-Saxon potential parameters.Best fitted values of the diffuseness parameters are found for each system,and a linear relationship is expressed between the diffuseness parameters and A1/31+A1/32.The correlation of the po-tential depth and radius parameters with A1/31+A1/32is also revealed within the limitations of the diffuseness parameter formula.Because the incident energies of most of the analyzed reactions are below or around the Coulombbarrier,the energy dispersion relation between the real and imaginary potentials is considered in order to investigatethe ratio between the imaginary and real potential well depths,resulting in an expression of W/V.Within the limitation of the volume integrals calculated with the Sao Paulo potential,parameterized formulas for the depth and radius parameters are obtained.The systematic Woods-Saxon potential parameters derived in the present work can reproduce not only the experimental data of elastic scattering angular distributions induced by 11B,12C,and 16O butalso some elastic scattering induced by other heavy-ions.

Lifetime measurement for the 2^+1 state in^106Cd

The lifetime of the 2^+1 state in ^106Cd populated via the ^94Zr(^16O,4n)^106Cd reaction has been measured with the Recoil Distance Doppler Shift technique in combination with the Differential Decay Curve Method.By subtracting the contamination in the data,the mean lifetime of the I^π=2^+1633 keV state was determined as 9.9(12)ps.The B(E2)value calculated in this study is in good agreement with the experimental systematics and was compared to the shell model calculations.