Direct mass measurements of the neutron-rich light isotopes of lithium through fluorine

The direct mass measurements of the neutron-rich nuclei¹¹Li,¹⁴Be,¹⁷B,^19–20C,^20–22N,^23–24O, and^25–27F have been performed using the Time-of-Flight Isochronous (TOFI) spectrometer. We observe a notable drop in the two-neutron separation energies for the oxygen and fluorine isotopes afterN=15. This behavior is interpreted using the shell model.     

Activation cross-sections for209Bi(n,α)206Tl reaction

Cross-section for²⁰⁹Bi(n, α)²⁰⁶Tl reaction at incident neutron energies 340±150 keV and 575±235 keV have been measured to be 1.26±0.18 μb and 1.55±0.23 μb, respectively. The activation technique was used for measuring the cross-sections. These values have been compared with theoretical values based on Hauser Feshbach Statistical Model.     

Small angle neutron scattering from micellar solutions of triton X-100

Micellar solutions of non-ionic surfactant triton X-100 (8% by weight) show phase separation at cloud pointT _cp ～ 335 K. This paper reports results of small angle neutron scattering (SANS) experiments from this solution as a function of temperature between 298 and 332 K. The range of wave-vector transferQ, covered in these experiments is from 0.02 to 0.15 Å^?1. It is seen that as one approachesT _cp, the neutron scattering cross section diverges in the region of lowQ (<0.06 Å^?1) while it is independent of temperature in region of largeQ(>0.06 Å^?1). We believe that the divergence of scattering at lowQ with an increase in temperature is because of changes in the structure factorS(Q) of the solution. The measured distributions have been analyzed using four different models for inter-micellar potential. The models used to calculate the structure factorS(Q) are (1) mean spherical approximation (MSA) with Yukawa tail for attractive potential, (2) MSA with an attractive square well potential, (3) random phase approximation (RPA) with an attractive square-well potential and (4) Sticky hard sphere model (attractive square-well potential with Percus-Yevick approximation). The strengths of the attractive potential required to fit the SANS data are (?6.6 to ? 14.4)/kt for model (1), (? 6.6 to ? 15.0)/kt for model (2), (? 3.8 to ? 7.3)/k _B T for model (3) and (?2 to ?2.7)/kt for model (4). On the basis of reasonableness of the derived strength of the potential near the phase separation temperature and its relative temperature dependence, it is concluded that present data favour the Sticky hard sphere model.     

New isotope159Lu and decay of158Lu,159,158Yb isotopes

Lutetium and ytterbium isotopes with masses A=159,158 have been produced by proton induced spallation reaction, and investigated by on-line mass separation and subsequent decay spectroscopy. A new isotope¹⁵⁹Lu (T_1/2=12.3±1 s) has been identified, and newγ-ray data have been obtained for the decay of¹⁵⁸Lu and^{159, 158}Yb.     

On the mechanism of (HI, α x n) reactions

An expression is obtained for the cross sections of (Heavy Ion,α x n) reactions by considering two possible mechanisms: compound nucleus formation and massive transfer. In the latter, an alpha particle is emitted in the very early stage of the reaction while the remnant of the projectile fuses into the target forming an excited nucleus which deexcites by neutron evaporation. A good agreement with the experimental excitation functions of¹⁵⁴Sm(¹⁶O,α x n) reactions is obtained which supports the massive transfer hypothesis.     

The neutron drip line in the region of <Emphasis Type="Italic">N</Emphasis>=20 and <Emphasis Type="Italic">N</Emphasis>=28 closures

Experimental studies of neutron drip line nuclei are introduced. The neutron drip line in the oxygen-magnesium region has been explored by the projectile fragmentation of a ⁴⁸Ca beam. New neutron-rich isotopes, ³⁴Ne and ³⁷Na, have been observed together with some evidence for the particle instability of ³³Ne and ³⁶Na. Recent data on mass measurements of neutron-rich nuclei at GANIL and some characteristics of binding energies in this region are discussed. Nuclear binding energies are very sensitive to the existence of nuclear shells, and together with the measurements of instability of doubly magic nuclide ²⁸O, they provide information on changes in neutron shell closures of very neutron-rich isotopes from carbon up to calcium. The conclusion about a rearrangement in neutron shell closures is given. The spectroscopic measurements can reveal details of the underlying microscopic structures; in-beam γ-ray spectroscopy is an effective tool to check for shell closures. The results on the γ-ray energies of the first 2⁺ level in even-even nuclei for the range N=12–32 are discussed. The strength of N=20 and N=28 shells is variable in the region from carbon up to magnesium.     

On the determination of collision cross sections by nuclear Doppler shift

We report on measurements of the energy loss of ions in matter by “Inverted Doppler Shift Attenuation” (IDSA). This new method is an inversion of the “Doppler Shift Attenuation” (DSA) method for the determination of lifetimes of nuclear states. While in DSA the exact knowledge of the velocity dependent energy loss functiondE/ds is required, it is shown that in IDSA this function or the absolute collision cross section, respectively, can be determined from the Doppler spectrum of an excited nuclear fragment recoiling in matter, whose lifetime is known. No corrections or assumptions concerning the collision processes are necessary. ⁷Li^* fragments (E _γ=478 keV) from the¹⁰B(n, α)⁷Li^* reaction produce an easily observable and analysable Doppler spectrum. Here boron must be a constituent or an implanted impurity of the material to be investigated. The experimental set-up is described. An exact relativistic analysis of the Doppler spectrum is given. The measured collision cross sections turn out (a) to be proportional tov within the range 1.5 · 10⁸≦v≦4.8 · 10⁸ cm/sec, (b) are thus only due to pure “electronic” collisions, and (c) sensitively dependent on the charge distributions of the target atoms.     

The hyperfine structure of the ground state of Ho165

Using the atomic beam magnetic resonance method four hyperfine structure frequencies have been measured in the ground state⁴ I _15/2 of Ho¹⁶⁵ with high precision at magnetic fields of up to 800 Oersted. In the analysis of these measurements a possible electrical sedecimpole (16-pole) interaction was included. The following multipole interaction constants could be calculated:A=800.582 8 (14) MHzB=?1668.100 (91) MHzC=?2224 (7520) HzD=?398 (790) Hz. Thus within the limits of this experiment no octopole or sedecimpole interaction could be established.     

Study of the heavy-fermion compound CeRu<Subscript>2</Subscript>Si<Subscript>2</Subscript> by the small-angle neutron scattering method

In order to directly observe neutron scattering by heavy fermion quasiparticles at low temperatures, a CeRu₂Si₂ single crystal has been studied by the small-angle neutron scattering method. In the experiment, neutron scattering is observed at T = 0.85 K for momentum transfers q ≤ 0.04 Å^?1, which is treated as the orbital component of magnetic scattering by heavy fermion quasiparticles. It has been found that the application of a magnetic field H = 1 T leads to both an increase in the observed scattering and its anisotropy with respect to the field direction. Moreover, measurements in the magnetic field reveal additional scattering for q > 0.04 Å^?1, which is well described by a Lorentzian and is interpreted as neutron magnetic scattering by spin-density fluctuations with a correlation radius R_c ≈ 30 Å.     

Preparation of n-ZnO/p-Si solar cells by oxidation of zinc nanoparticles: effect of oxidation temperature on the photovoltaic properties

In this study, n-ZnO/p-Si solar cells were fabricated by spraying ZnO nanoparticles (NPs) film synthesised by dissolving of high purity zinc in hydrogen peroxide H₂O₂ followed by thermal oxidation in air on p-type silicon substrates. The oxidation was carried out at different temperatures (200–500) °C. The crystalline structure of the ZnO NPs films was investigated by X-ray diffraction which indicated wurtzite structure films along (100) plane. The morphology of the NPs was studied by atomic force microscopy and scanning electron microscopy. The result showed an average grain size of ZnO NPs in the range of (72.7–95.8) nm and the surface roughness increasing with oxidation temperature. Three peaks located at ultraviolet, violet and green emission regions were noticed in the photoluminescence spectra of ZnO NPs. From optical studies, it was shown that the direct optical band gap is found to be in the range of (3.85–3.96) eV depended on the oxidation temperature. The synthesised ZnO films have n-type conductivity, and the mobility was in the range of (7–24) cm² V^?1 s^?1. Current–voltage I–V and capacitance–voltage C–V of ZnO NPs/Si heterojunction solar cell were investigated as function of oxidation temperature. The spectral response of n-ZnO NPs/p-Si solar cell showed two peaks of response and its maximum value approaching 0.62 mA W^?1 at λ = 800 nm. Solar cell oxidized at 500 °C gave open circuit voltage V _OC of 375 mV, short circuit current density J _SC of 25 mA cm^?2, a fill factor FF of 0.72, and conversion efficiency η of 6.79 % under illumination of 100 mW cm^?2.     

Least squares adjustment of the coupling constants in nuclear beta-decay

Assuming theV-A theory, fully polarized neutrinos, and lepton conservation, best values of the vector and axial vector coupling constants are deduced from all available data on neutron decay and from theft- values of¹⁴O,^26mAl and³⁴C1. Special consideration is given to the treatment of errors and to radiative corrections. For the determination of the coupling constantratio, radiative corrections are, at present, unimportant. We find ¦G_A/G_V¦=1.250 + 0.009 with a phase angle φ=(181.1±1.3)⁰. From the weighted mean ?t-value, including charge dependent and “outer” radiative corrections, we find an effective coupling constant G′_V=(1.413±0.002)x 10⁴⁹erg cm³. The error is mainly due to the uncertainty of charge dependent corrections.     

Production of high energy deuterons in the reaction:3He+3He→4He+2H+e ++v

Experiments on the reaction:³He+³He→⁴He+²He using a single four detector telescope have shown evidence for the production of deuteron pulses, consistent with the²He→²H+e⁺+v fusion reaction in the final state. New measurements on the same reaction using improved techniques viz.A) a windowless³He gas target andB) α- d correlation detection with 5 ns resolving time and antipileup circuitry have been performed. Calibrations were obtained from the⁷Li+³He→²H+⁴He+⁴He reaction spectra. The correlation angles were 30° and 97° for the alphas and deuterons respectively. Deuteron pulses have been observed, correlated with alpha particles. A cross section of (1.7 ±0.5)nbsr^?1MeV^?1 was obtained consistent with previous measurements using a single telescope.     

Measuring fluence of fast neutrons with planar silicon detectors

The results of measurements of 1-MeV (Si) equivalent fast neutron fluence with silicon planar detectors are reported. The measurement method is based on the linear dependence of the reverse detector current increment on the neutron fluence: ΔI = α _I × Φ × V. This technique provides an opportunity to measure the equivalent fluence in a wide dynamic range from 108 to 10¹⁶ cm^–2 with an unknown neutron energy spectrum and without detector calibration. The proposed method was used for monitoring in radiation resistance tests of different detector types at channel no. 3 of IBR-2 and for determining the fluence of fission and leakage neutrons at the KVINTA setup.     

QCL-based TDLAS sensor for detection of NO toward emission measurements from ovarian cancer cells

The development of a sensitive sensor for detecting nitric oxide (NO) emissions from biological samples is reported. The sensor is based on tunable diode laser absorption spectroscopy (TDLAS) using a continuous wave, thermoelectrically cooled quantum cascade laser (QCL) and a 100-m astigmatic Herriot cell. A 2f-wavelength modulation spectroscopy technique was used to obtain QCL-based TDLAS NO emission measurements with an optimum signal-to-noise ratio. An absorption line at 1,900.076 cm^?1 was targeted to measure NO with a minimum detection limit of 124 ppt. Positive control measurements with the NO donor DETA NONOate were performed to determine and optimize the sensor performance for measurements of biological samples. Our measurements with NO donor show the potential suitability of the sensor for monitoring NO emission from cancer cells for biological investigations.     

Prototype of a large neutron detector based on MWPC

A prototype of large-area position sensitive neutron detector was designed and constructed according to the requirements of the Small-Angle Scattering spectrometer of China Spallation Neutron Source(CSNS).The detector was based on the 3He neutron convertor and MWPC with an effective area of 650 mm×650 mm.A prototype was completed and tested with 55Fe X-ray.The high-pressure vessel was designed and constructed with high-strength aluminum alloy.A position resolution of about 4.6mm×2.3 mm(FWHM)and efficiency65%for neutrons with wavelength of 1.8?was determined after the operational gas filled.     

Principle component analysis of the spectroscopic and neutron parameters characterizing PF-1000 device plasmas

Principal Component Analysis has been employed in order to find correlations between different quantities (related to spectroscopy in visible range, neutron yield and the time derivative of the current) describing Z-pinch plasma in the PF-1000 installation. Set of measurements in various plasma conditions has been taken into account. Strong correlation between level of impurity content and neutron yield has been found.     

Discovery of a <Emphasis Type="Italic">P</Emphasis>-odd effect in triton emission from the reaction <Superscript>6</Superscript>Li(<Emphasis Type="Italic">n</Emphasis>, α)<Superscript>3</Superscript>H

The results of measuring the P-odd asymmetry (S_n · P_t) for triton emission from the reaction ⁶Li(n, α)³H are presented. Here, S_n is the neutron spin and P_t is the triton momentum. Three series of measurements were performed, one at the Petersburg Nuclear Physics Institute (Gatchina, Russia) in a vertical neutron beam from the PWR reactor and two in the PF1B beam from the reactor at the Institute Laue-Langevin (Grenoble, France). On the basis of all three experiments, the P-odd asymmetry coefficient was found to be α_PN = ?(8.6 ± 2.0) × 10^?8. The results of zero experiments and calculations give every reason to believe that the above P-odd asymmetry is due to the reaction being studied.     

A comparative study on the effects of salt and filler on transport and structural properties of organic–inorganic hybrid electrolytes

Organic–inorganic hybrid electrolytes based on the reaction of tri-block copolymer poly(propylene glycol)-block-poly(ethylene glycol)-block-poly(propylene glycol) bis(2-aminopropyl ether), poly(ethylene glycol diglycidyl ether, and (3-glycidyloxypropyl)trimethoxysilane doped with LiClO₄ and SiO₂ nanoparticles were synthesized by a sol–gel process. The structural and dynamic properties of the materials thus obtained were systematically investigated by Fourier transform infrared spectroscopy, differential scanning calorimetry, thermogravimetric analysis, alternate current impedance, and ¹³C solid-state NMR measurements. A maximum ionic conductivity of 3.2?×?10^?5 S cm^?1 was obtained at 30 °C for the solid hybrid electrolyte with a [O]/[Li] ratio of 16 and 7 wt% of SiO₂ nanoparticles. A Vogel–Tamman–Fulcher-like temperature dependence of ionic conductivity was observed for the hybrid electrolytes, implying that the diffusion of charge carriers was assisted by the segmental motions of the polymer chains.     

The27Al(n,d)26Mg reaction at 22 MeV

Deuteron spectra from the reaction²⁷Al(n, d)²⁶Mg has been measured at reaction angles 0°→60°, with a spectrometer comprising three multiwire proportional counters followed by a curved plastic scintillator. Spectra were obtained with an energy resolution of ～0.7 MeV and an angle resolution of ～5°. Angular distributions for transitions to the ground state and excited states at 1.81, 2.93 and 4.3 MeV in²⁶Mg were obtained. Distorted waves analysis of the angular distributions yield spectroscopic factors of 0.29(8), 0.9(3), 0.18(7) and 1.9(6) for the ground and excited states, respectively. The results are compared with previous (d,³He) and (n, d) measurements, and with theoretical predictions.     

Z–Z' mixing effects in W boson pair production processes at hadron and lepton high-energy colliders

Potential possibilities to detect the effects of Z–Z' mixing in the W-pair production process in proton-proton and electron–positron collisions at the Large Hadron Collider (LHC) and International Linear Collider (ILC) have been studied. It has been established that the processes of W boson pair production are very sensitive to the angle of Z–Z' mixing and their measurements in current and future experiments will make it possible to improve modern restrictions on the angle of Z–Z' mixing in the models with extended gauge sector. At a nominal energy of 14 TeV and an integral luminosity of 100 fb^–1, the LHC collider can offer much more precise information on the parameter of Z–Z' mixing and the mass M ₂ than can be obtained using the ILC leptonic collider (0.5 TeV).