Determination of the number of atoms of the long-lived nuclide 126Sn by γ-ray spectrometry

By using HPGe γ-ray spectrometry, the activity of the long-lived fission product 126Sn in a SnOB2 sample was measured. The number of 126Sn atoms and the ratio of 126Sn to Sn were calculated based on the half-life value of 2.35×105a and the chemical stoichiometry. The result of the ratio of 126Sn to Sn, （1.033±0.037）×10-8, is consistent with the results measured by the accelerator mass spectrometry （AMS） within uncertainty limits, which confirms our procedures in the measurement of 126Sn by AMS and lays a foundation for the AMS measurement of 126Sn at much lower levels.     

Measurement of the half-life of ~(79)Se with accelerator mass spectrometry

The accelerator mass spectrometry(AMS) is an effective method for the determination of the half-life of long-lived radionuclides. In this paper, we report a method for measurement of the half-life of79 Se. The number of79 Se atoms was determined from measured79Se/Se absolute ratios with the AMS system at the China Institute of Atomic Energy and the decay rate of79 Se was determined by counting the emitted β-rays with a liquid scintillation spectrometer. The major improvements of our measurements include using the high abundance of an79 Se sample which was cooled for many years to exclude the interference of short-lived nuclides, the extraction of SeO-2molecular ions, that results in a suppression of the79 Br background by as much as about five orders of magnitude. Also, an AMS measurement of the absolute ratio of79Se/Se was developed to avoid systematic errors. The results show that79Se/Se is(2.35±0.12)×10-7in the reference sample and the radioactivity of79 Se is(1.24±0.05) Bq/g, so the half-life of79 Se is(2.78±0.18)×105a.     

Preliminary study of ~(10)Be/~7Be in rainwater from Xi'an by Accelerator Mass Spectrometry

The ~(10)Be/~7Be ratio is a sensitive tracer for the study of atmospheric transport, particularly with regard to stratosphere-troposphere exchange. Measurements with high accuracy and efficiency are crucial to ~7Be and ~(10)Be tracer studies. This article describes sample preparation procedures and analytical benchmarks for ~7Be and ~(10)Be measurements at the Xi'an Accelerator Mass Spectrometry(Xi'an-AMS) laboratory for the study of rainwater samples. We describe a sample preparation procedure to fabricate beryllium oxide(Be O) AMS targets that includes co-precipitation, anion exchange column separation and purification. We then provide details for the AMS measurement of ~7Be and ~(10)Be following the sequence BeO~-→Be~(2+)→Be~(4+) in the Xi'an- AMS. The ~(10)Be/~7Be ratio of rainwater collected in Xi'an is shown to be about 1.3 at the time of rainfall. The virtue of the method described here is that both ~7Be and ~(10)Be are measured in the same sample, and it is suitable for routine analysis of large numbers of rainwater samples by AMS.     

Calibration of Membrane Viscosity of the Reconstituted Vesicles by Measurement of the Rotational DIffusion of Bacteriorhodopsin

Membrane viscosity of the reconstituted vesicles was calibrated by rotational diffusion of bacteriorhodopin(BR) in dimyristoylphosphatidylcholine(DMPC) and egg phosphatidylcholine(PC) vesicles.Rotational diffusion of BR in the vesicles was measured by flash-induced absorption anisotropy decay.BR was,for the first time ,reconstituted successfully into DMPC and egg PC vesicles,From the measurement of flash-induced absorption anisotropy decay of BR,the value of rotational diffusion coefficient D was obtained from each curve fitting by a global fitting procedure and ,in turn,membrane viscosity η was estimated from D.The results have shown that membrane viscosity is temperature-dependent,It was decreased as temperature increased,but a transition occurred in the region of the respective phase transition of DMPC and egg PC,respectively,The decrease of η was fast near the phase transition for DMPC and egg PC.Few effects of lipid/BR ratio and glycerol or sucrose in suspension medium on membrane viscosity were found.     

Measurement of Ξ_(cc)~(++) production in pp collisions at s~(1/2)=13 TeV

The production of Ξ_(cc)~(++) baryons in proton-proton collisions at a centre-of-mass energy of s~(1/2)=13 TeV is measured in the transverse-momentum range 4 pT15 GeV/c and the rapidity range 2.0 y4.5.The data used in this measurement correspond to an integrated luminosity of 1.7 fb~(-1),recorded by the LHCb experiment during2016.The ratio of the Ξ_(cc)~(++) production cross-section times the branching fraction of the Ξ_(cc)~(++)→Λ_c~+K~-π~+π~+ decay relative to the prompt Λ_c~+production cross-section is found to be(2.22±0.27±0.29)×10~(-4),assuming the central value of the measured Ξ_(cc)~(++) lifetime,where the first uncertainty is statistical and the second systematic.     

Dependence of Structure and Haemocompatibility of Amorphous Carbon Films on Substrate Bias Voltage

Tetrahedral amorphous hydrogenated carbon (ta-C:H) films on Si(lO0) substrates were prepared by using a magnetic-field-filter plasma stream deposition system. Samples with different ratios of sp^3-bond to sp^2-bond were obtained by changing the bias voltage applied to the substrates. The ellipsometric spectra of various carbon films in the photon energy range of 1.9-5.4eV were measured. The refractive index n and the relative sp^3 C ratio of these films were obtained by simulating their ellipsometric spectra using the Forouhi-Bloomer model and by using the Bruggeman effective medium approximation, respectively. The haemocompatibility of these ta-C:H films was analysed by observation of platelet adhesion and measurement of kinetic clotting time. The results show that the sp^3 C fraction is dependent on the substrate bias voltage, and the haemocompatibility is dependent on the ratio of sp^3-bond to sp^2-bond. A good haemocompatibility material of ta-C:H films with a suitable sp^3 C fraction can be prepared by changing the substrate bias voltage.     

Double sinusoidal phase modulating laser diode interferometer for thickness measurements of transparent plates

A double sinusoidal phase modulating (SPM) laser diode interferometer for thickness measurements of a transparent plate is presented. A carrier signal is given to the interference signal by using a piezoelectric transducer, and the SPM interferometry is applied to measure the thickness of a transparent plate. By combining the double-modulation technique with the Bessel function ratio method, the measurement error originating from Sight intensity fluctuations caused by the modulation current can be decreased greatly. The thicknesses of a glass parallel plate and a quartz glass are measured in real time, and the corresponding experimental results are also given.     

Measurement of a discontinuous object based on a dual-frequency grating

The dual-frequency grating measurement theory is proposed in order to carry out the measurement of a discontinuous object. Firstly, the reason why frequency spectra are produced by low frequency gratings and high frequency gratings in the field of frequency is analysed, and the relationship between the wrapped-phase and the unwrapping-phase is discussed. Secondly, a method to combine the advantages of the two kinds of gratings is proposed: one stripe is produced in the mutation part of the object measured by a suitable low frequency grating designed by MATLAB, then the phase produced by the low frequency grating need not be unfolded. The integer series of stripes is produced by a high frequency grating designed by MATLAB based on the frequency ratio of the two kinds of gratings and the high frequency wrapped-phase, and the high frequency unwrapping-phase is then obtained. In order to verify the correctness of the theoretical analysis, a steep discontinuous object of 600×600 pixels and 10.00~mm in height is simulated and a discontinuous object of ladder shape which is 32.00~mm in height is used in experiment. Both the simulation and the experiment can restore the discontinuous object height accurately by using the dual-frequency grating measurement theory.     

Application of ^41Ca Tracer and Its AMS Measurement in CIAE

The man-made calcium isotope ^41Ca is an ideal tracer for the study of calcium metabolism. We represent the first application of accelerator mass spectrometry (AMS) measurement of ^41Ca tracer in China. The technique is being applied to the research field of cell messenger at the China Institute of Atomic Energy (CLAE). The sample preparation methods and the AMS measurements are discussed and some interesting results are presented.     

Generalization of α-Decay Cluster-Model to Nuclei Near Spherical and Deformed Shell Closures

The cluster model of α-decay is extended to the regions around doubly magic spherical nucleus 208pb and around deformed shell closure 270Hs, respectively. The effects of spherical shell closures (N = 126 and Z = 82) on α-decay are investigated by introducing an N-dependent α-preformation factor and a Z-dependent one inspired by a microscopic model. Good agreement between the theoretical α-decay half-lives and the measured ones is obtained for the spherical nuclei near the doubly magic nucleus 208 Pb, where the nuclear shell effect is included in the expression of α-preformation factor. The cluster model is also generalized for the decay of deformed nuclei. The branching ratios of a-decays from the ground state of a parent nucleus to the ground state (0 ) of its deformed daughter nucleus and to the first excited state (2 ) are .calculated in the framework of the cluster model. The results indicate that a measurement of c spectroscopy is a feasible method to extract the information of nuclear deformation of superheavy nuclei around the deformed nucleus 270 Hs.     

Measurement of the pion form factor for M_(ππ)～2 between 0.1 and 0.85 GeV~2 with the KLOE detector

The KLOE experiment at the φ-factory DAΦNE has measured the pion form factor in the range between 0.1M_(ππ)～2 0.85 GeV2 using events taken at s～(1/2)=1 GeV with a photon emitted at large polar angles in the initial state.This measurement extends the M_(ππ)～2 region covered by KLOE ISR measurements of the pion form factor down to the two pion production threshold.The value obtained in this measurement of the dipion contribution to the muon anomalous magnetic moment of aμππ =(478.5±2.0stat±4.8syst±2.9theo)·10-10 further confirms the discrepancy between the Standard Model evaluation for aμ and the experimental value measured by the(g-2) collaboration at BNL.     

Improved measurement of the reactor antineutrino flux and spectrum at Daya Bay

A new measurement of the reactor antineutrino flux and energy spectrum by the Daya Bay reactor neutrino experiment is reported. The antineutrinos were generated by six 2.9 GWth nuclear reactors and detected by eight antineutrino detectors deployed in two near(560 m and 600 m flux-weighted baselines) and one far(1640 m flux-weighted baseline) underground experimental halls. With 621 days of data, more than 1.2 million inverse beta decay(IBD) candidates were detected. The IBD yield in the eight detectors was measured, and the ratio of measured to predicted flux was found to be 0.946±0.020(0.992±0.021) for the Huber+Mueller(ILL+Vogel) model. A 2.9σ deviation was found in the measured IBD positron energy spectrum compared to the predictions. In particular, an excess of events in the region of 4–6 MeV was found in the measured spectrum, with a local significance of 4.4σ. A reactor antineutrino spectrum weighted by the IBD cross section is extracted for model-independent predictions.     

Optimal design and experimental measurement of the subharmonic characterizations of encapsulated microbubble

Based on a theoretical motion equation of encapsulated microbubbles within an ultrasound field, the subharmonic characterizations of microbubbles are optimally designed and analyzed by a computer aided design system. The effects of size, shell elasticity and acoustic pressure on subharmonic response of microbubbles are calculated theoretically to obtain the optimal parameters for nondestructive subharmonic imaging. In addition, microbubbles with different shell elasticity are prepared, and their subharmonic responses are measured in vitro. The results of theoretical calculation and acoustic measurement show that good subharmonic enhancement can be obtained by using the encapsulated microbubbles with the mean size of 3 μm, which were prepared from the surfactant solution with the proper ratio of shell material. It is also shown that the best operating acoustic pressure is 200 to 400 kPa for nondestructive subharmonic imaging based on such kind of microbubbles.     

Effect of the annealing temperature on the long-term thermal stability of Pt/Si/Ta/Ti/4H–SiC contacts

The Pt/Si/Ta/Ti multilayer metal contacts on 4H–Si C are annealed in Ar atmosphere at 600°C–1100°C by a rapid thermal processor(RTP). The long-term thermal stability is evaluated by aging the annealed contact at 600°C in air. The contact's properties are determined by current–voltage measurement, and the specific contact resistance is calculated based on the transmission line model(TLM). Transmission electron microscope(TEM) and energy-dispersive x-ray spectrometry(EDX) are used to characterize the interface morphology, thickness, and composition. The results reveal that a higher annealing temperature is favorable for the formation of an Ohmic contact with a lower specific contact resistance, and causes the rapid degradation of the Ohmic contact in the aging process.     

Ultrafast nonlinear optical response of Ag:BaTiO_3 composite films at the near-ultraviolet wavelengths

The ultrafast nonlinear optical response of Ag:BaTiO3 composite films synthesized by pulse laser deposition (PLD) is studied at the near-ultraviolet (400 nm) wavelength. The pulse duration of the laser used in the measurement is 200 fs. The real and imaginary parts of the third-order nonlinear susceptibility X(3) of the composite materials are measured. The composite films indicate self-focusing effect and nonlinear saturation, the values of ReX(3) and ImX(3) are measured to be 3.42 × 10-10 and -1.37 × 10-10 esu respectively, which are much lower than those reported before. It is mainly because that the duration of the laser used in the measurements is too short to induce the hot electron excitation and the thermal effect. The ultrafast nonlinear saturated absorption response of the Ag:BaTiO3 composite films may have potential applications for femtosecond laser mode locking.     

A restraining multipath effect method for the measurement of insertion loss of underwater acoustic materials

A method suppressing multipath effect when measuring the underwater acoustic materials in a reverberant field is proposed, which is called "virtual end-fire array method".To weaken the coherence of the same-frequency reflection interference of each path, signal of different phases at different positions was transmitted by a single transducer in the simulation design, and a sharp directionality in the direction of the array length was formed. All signals at the above positions were superimposed to eliminate the clutters. The insertion loss(IL) of the material was finally calculated by extracting the desired waveforms. In the measured frequency range of 3–20 k Hz, the aluminum plate with size of 1.1 m × 1.0 m × 8 mm and the round aluminum plate with 0.5 m in diameter and 8 mm in thickness were measured in a reverberant tank with size of 5.5 m × 3.5 m × 3.5 m. Results showed the measured lowest effective frequency limit can be reduced by the virtual end-fire array technique compared with the conventional method.In the measurement of round aluminum plate and rectangular aluminum plate, errors in the effective measurement band was less than 0.5 d B and the interference of the acoustic multipath propagation effects was reduced effectively. The ability of the transducer in reverberant tank to measure acoustic materials has been improved after implementing this method.     

Generalization of α-Decay Cluster-Model to Nuclei Near Spherical and Deformed Shell Closures

The cluster model of a-decay is extended to the regions around doubly magic spherical nucleus ^208Pb and around deformed shell closure ^270Hs, respectively. The effects of spherical shell closures (N=126 and Z=82) on α-decay are investigated by introducing an N-dependent α-preformation factor and a Z-dependent one inspired by a microscopic model. Good agreement between the theoretical a-decay half-lives and the measured ones is obtained for the spherical nuclei near the doubly magic nucleus ^208Pb, where the nuclear shell effect is included in the expression of α-preformation factor. The cluster model is also generalized for the decay of deformed nuclei. The branching ratios of α-decays from the ground state of a parent nucleus to the ground state (0^ ) of its deformed daughter nucleus and to the first excited state (2^ ) are calculated in the framework of the cluster model. The results indicate that a measurement of α spectroscopy is a feasible method to extract the information of nuclear deformation of superheavy nuclei around the deformed nucleus ^270Hs.     

Tuning the focusing spot of plasmonic nanolens by aspect ratio under linear polarization

A new plasmonic nanolens that can be tuned by varying the circular structure into an elliptical annulus and the aspect ratio from 1 to 0.1 and 1 to 2,respectively,is proposed.Using the rigorous finite-difference and time-domain algorithm,we find that when the aspect ratio ranges from 1 to 0.1,a good linear relationship exists between the aspect ratio and focusing spot size at the full-width at half-maximum in the x- and y-directions,respectively.The corresponding calculated FWHM ranges from 96×126(nm) to 15×52(nm)(Full Width at Half Maximum).     

Measurement of sensitivity of transducer in the field of NDT by the reciprocity technique

The sensitivity of a transducer should be an important characteristic inthe field of NDT.But so far,no method for this measurement of the sensitivity of atransducer applied to the ultrasonic flaw detection is available.In this paper thetransducer is regarded as a plane source and the reciprocity parameter under thecondition of the far field is derived.We have calibrated the sensitivity of ultrasonictransducers with the reciprocity technique in the solid sample.The experimentsshow and confirm that the transmitting and receiving sensitivities of the transducerapplied to NDT can be exactly measured.The precision of the measurement is with-in ± 1dB under a certain coupling condition.     

Study of the production of Λ_b~0 band ~0 hadrons in pp collisions and first measurement of the Λ_b~0→J/ψpK~- branching fraction

The product of the A_b~0(B~0) differential production cross-section and the branching fraction of the decay A_b~0→J/ψpK~-(B~0→J/ψK~*(892)~0) is measured as a function of the beauty hadron transverse momentum,p_T,and rapidity,y.The kinematic region of the measurements is p_T 20 GeV/c and 2.0y4.5.The measurements use a data sample corresponding to an integrated luminosity of 3fb~(-1) collected by the LHCb detector in pp collisions at centre-of-mass energies s~(1/2)=7 TeV in 2011 and s~(1/2)= 8TeV in 2012.Based on previous LHCb results of the fragmentation fraction ratio,f_∧_b~0/f_d,the branching fraction of the decay ∧_b~0→J/ψpK~- is measured to be B(∧_b~0→J/ψpK~-)=(3.17±0.04±0.07±0.34_(-0.28)~(+0.45)×10~(-4)where the first uncertainty is statistical,the second is systematic,the third is due to the uncertainty on the branching fraction of the decay B~0→J/ψK~*(892)~0,and the fourth is due to the knowledge of f_∧_b~0/f_d.The sum of the asymmetries in the production and decay between A_b and A_b~0 is also measured as a function of p_T and y.The previously published branching fraction of A_b~0→J/φpπ~-,relative to that of A_b~0→J/ψpK~-,is updated.The branching fractions of∧_b~0→P_c~+(→J/ψp)K~- are determined.