Synthesis of C26 Crystallite Polyethylene by C2+ Ion Bombardment

A new form solid Carbon has been synthesized consisting of a hexagonal close packing of a26 molecules under energetic C₂₆ ion 2.4 MeV bombardment of ultra high molecular weight polyethylene. The beam current was about 150 mA and the total dose was 1×10¹⁶ ions cm^－2. The residual gas pressure in the irradiation chamber was 1.3×10^－4Pa during bombardment High-resolu-tion transmission electron microscopy, electron diffraction, and time-of-flight mass spectroscopy studies of the molecular packing confirm that the C₂₆ molecules have the Caged fullerene structure.     

RESEARCH ON SOME CHARACTERISTICS AND IMPROVEMENTS OF A 70cm STREAMER CHAMBER

In this paper the influence of various proportion of Ne-He gases and the time delay on the quality of streamer tracks has been studied. The diameterand density of streamers under these mixed-gas conditions have been measured.
The time resolution of this streamer chamber was determined to be 2.1μs in 69% Ne+31% He+8×10^－8 SF₆, and as 177μs in pure neon by using the exponentially decreasing relation of streamer desity with delay time. The spatial resolution was determined to be 0.32mm in Ne+3×10^－8 SF₆ by measuring the streamer diameters, and the method of track standard deviation was also used.
Some results show that the diameter and brightness increase with increasing high voltage, but become rather even when high voltage continues increasing.
Photographs were taken with domestically produced special film (32 DIN, 60 lines/mm), being similar to Kodak SO-143.
A special designed central electrode of the streamer chamber with its wires inlaid in lucite plate is successful for preventing gas from breakdown near wires. Besides, delay time has been reduced to 1.3μs, mainly by the Marx generator and its trigger system the parameters of which have been chosen by a series of experiments.     

Pure annihilation type decays B0→Ds- K2*+ and Bs→Da2 in perturbative QCD approach

We calculate the branching ratios of pure annihilation type decays B⁰→D_s^- K₂^*+ and B_s→Da₂ using the perturbative QCD approach based on k_T factorization. The branching ratios are predicted to be (60.6_{-16.5-10.4-2.1}^{+17.3+4.3+3.2} )× 10^-6 for B⁰→D_s^- K₂^*+, (1.1_-0.4-0.2-0.1^+0.4+0.1+0.1)×10^-6 for B_s→D⁰a₂⁰ and (2.3_-0.8-0.4-0.1^+0.8+0.2+0.1)×10^-6 for B_s→D^-a₂⁺. They are large enough to be measured in the ongoing experiment. Due to the shortage of contributions from penguin operators, there are no direct CP asymmetries for these decays in the Standard Model. We also derive simple relations among these decay channels to reduce theoretical uncertainties for the experiments to test the accuracy of theory and search of new physics signal.     

THE SYMMETRY BREAKING OF THE SUPERSTRING-INSPIRED MODEL

By considering the one-loop radiative corrections,we discussed the symmetry breaking of a specific superstringinspired model based on the gauge group SU(3)_C×SU(2)_L×SU(2)_R×U(1)^′×U(1)^′′ We discussed phenomenologically the neutrino mass problem,and the value of the soft breaking parameters A,m and M at the scale Mx were given.     

STUDY ON RADIATION DAMAGE OF CHINESE-MADE HIGH-Z SCINTILLATION CRYSTALS

Radiation damage effects of several Chinese-made high-Z scintillation crystals have been studied on a ⁶⁰Co irradiation unit of 100KCi Results on small size BGO crystals irradiated by 60Co γ rays with various doses from 5×10³ to 7.5×10⁵rad are presented.The decrease in scintillation light output depends non-linearly on the dose applied and saturation effects above 5×10⁴rad have been observed.The spontaneous recovery of the light output can be described by the sum of at least three exponential functions.The radiation damage effects of small size BaF₂,CsI(Tl) and ZnWO₄ crystals at 5×10⁵rad were also investigated.Serious damage to BaF₂ has been found.Preliminary analyses indicate that this may be attributed to the inclusion of certain critical elements in the crystal.CsI(T1) after irradiation does not exhibit strong afterglow of noticeable coloration as were reported in the literature.     

Photoluminescence Study of He ions hot-implanted Sapphire After 208Pb27+ of 230MeV Irradiation

In the present work the photoluminescence (PL)character of sapphire implanted with He ions and subsequently irradiated with ²⁰⁸Pb²⁷⁺ of 1.1MeV/u was studied. Sapphire single crystals were implanted with 110keV He ions at 600K temperature to fluences ranging from (0.5 to 2)×10¹⁷ ions/cm², some of them were subsequently irradiated with ²⁰⁸ Pb²⁷⁺.From experimental results we found PL spectra peaks at 375nm, 413nm, and 450nm, and it's intensity gets maximum at fluence of 5×10¹⁶ He ions/cm². Also we found a new peak at 390nm after subsequent ²⁰⁸ Pb²⁷⁺ irradiation, which is possibly due to the crystallized sediment containing nano crystal Al₂O₃ appeared on the sample surface.     

CONFINEMENT PROPERTIES OF THE PURE GAUGE FIELDS ON COSET SPACE OF AN ABELIAN CHIRAL GROUP

In this paper the lattice current-current propagator is calculated and the influence of coset pure gauge fields of an Abelian chiral group G=U₁×U⁵ on confinement properties of a quark system is discussed by virtue of the Wilson's criterion of lattice gauge theory. When subgroup H is U₁, the coset pure gauge fields only contribute a perimeter law factor to the current-current propagator which has no influence on confinement properties of the system. When subgroup H is U⁵, the coset pure gauge fields also have no influence on confinement properties of the system.     

A STRUCTURE MODEL OF STRATONS AND LEPTONS

A subquark model is proposed. According to this model, stratons and leptons are consisted of rishons T and V, which are multiplets of group SU_H(3)×SU_C(3)×SU_G(2)×SU(2)×U(1). Three generations of both stratons and leptons are obtained naturally. In this model, proton decay modes are μ^－e⁺e⁺ or e^－μ⁺μ⁺.     

TRIPLET TO SINGLET CONVERSION OF POSITRONIUM IN OXYGEN

Using a aerogel sample with introduced oxygen gas as a variable energy positronium source,the triplet to singlet conversion of positronium in the elastic and inelastic collisions between positronium atoms and oxygen molecules has been investigated with a time selecting energy spectrometer.We have found that the conversion cross section σ_0—p is proportional to 1/v for slow positronium in the elastic collisons,where v is the mean velocity of positronium,and for the inelastic processes,the cross sections are estimated to be σ_0—p=2.1×10^－17cm² and 6.6×10^－18cm² respectively at kinetic energies of positronium near two thresholds.     

U(B)(6)×U(v)(12)×U(π)(4) DYNAMICAL SYMMETRY IN ODD-ODD NUCLEI

SO^(Bvπ)(6) limit of U^(B)(6)×U^(v)(12)×U^(π)(4) dynamical symmetry in odd-odd nuclei is discussed Energy formula and wave functions are obtained,and exaetd expressions for E₂ trasition rates and and one-nucleon transfer intensities are derived.The spectra of ¹⁹⁸Au₁₁₉ and ¹⁸⁸Ir₁₁₁ are compared with the exprimental values.     

Developments of a 2D position sensitiveneutron detector

China Spallation Neutron Source (CSNS), one project of the 12^th Five-Year-Plan scheme of China, is under construction in Guangdong province. Three neutron spectrometers will be installed during the first phase of the project, and two-dimensional position sensitive thermal neutron detectors are required. Before the construction of the neutron detectors, a prototype of a two-dimensional 200 mm×200 mm Multi-wire Proportional Chamber (MWPC) with Ar/CO₂ (90/10) flowing gas has been constructed. In 2009, the prototype was tested with the ⁵⁵Fe X-ray using part of the electronics, and performed well.
Following the test in 2009, the neutron detector was constructed with the complete electronics and filled with the 6 atm. ³He+2.5 atm. C₃H₈ gas mixture in 2010. The neutron detector has been primarily tested with an Am-Be source. In this paper, new developments of the neutron detector including the design of the high pressure chamber, the optimization of the gas purifying system and the gas filling process will be reported. The results and discussion are also presented in this paper.     

Integrability of AdS3×S3 Superstring

From the κ symmetric action of IIB string in AdS₃×S³ background given by Rahmfeld and Rajaraman, we derive the equations of motion. Then using the twisted dual transformation which was introduced by Hou et al. We construct the flat currents, and hence conserved non-local charge with one free parameter, for the Green-Schwarz superstring in AdS₃×S³. Thus we show the AdS₃×S³ string is integrable.     

Constraint on the warped space from B→X_sγ

We analyze the theoretical prediction on the branching ratio of B→X_sγ to order Λ_EW²/Λ_KK² in extension of the standard model with a warped extra dimension and the custodial symmetry SU(3)_c×SU(2)_L×SU(2)_R×U(1)_X×P_LR, where Λ_KK denotes the energy scale of low-lying Kaluze-Klein excitations and Λ_EW denotes the electroweak energy scale. Contributions from the in nite series of Kaluze-Klein excitations are summed over through the residue theorem. The numerical result indicates that the present experimental data constrain the parameter space of the concerned model strongly.     

Large Storage Window in a-SiNx/nc-Si/a-SiNx Sandwiched Structure for Nanocrystalline Silicon Floating Gate Memory Application

An a-SiNx/nanocrystalline silicon [（nc-Si）/a-SiNx] sandwiched structure is fabricated in a plasma enhanced chemical vapour deposition （PECVD） system at low temperature （250℃）. The nc-Si layer is fabricated from a hydrogen-diluted silane mixture gas by using a layer-by-layer deposition technique. Atom force microscopy measurement shows that the density of nc-Si is about 2 ×10^11 cm^-2. By the pretreatment of plasma nitridation, low density of interface states and high-quality interface between the Si substrate and a-SiNs insulator layer are obtained. The density of interface state at the midgap is calculated to be 1 ×10^10 cm^-2eV^-1 from the quasistatic and high frequency C - V data. The charging and discharging property of nc-Si quantum dots is studied by capacitance-voltage （C- V） measurement at room temperature. An ultra-large hysteresis is observed in the C - V characteristics, which is attributed to storage of the electrons and holes into the nc-Si dots. The long-term charge-loss process is studied and ascribed to low density of interface states at SiNx/Si substrate.     

THE U(90) DYNAMICAL SYMMETRY IN LIGHT NUCLEI

In the IBM4,when s.d.g bosons are presented,the symmetry group of the system is U(90) In this paper,the group chain.U₉₀ U₁₅(sdg)×U₆(ST) SU₁₅(sdg)×U₆(ST) SU₅(sdg)× O₆(ST) SO₅(dg)×O₃(S)×O₃(T) O₃(dg)×O₃(S)×O₃(T) O₃(J)×O₃(T) is discussed,the reduction rules and the typical energy spectra are obtained.An example of a spectrum with this dynamical symmetry is found out,where the even-even nucleus ³⁴S and odd-odd nucleus ³⁴Cl are in one multiplet.     

Observation of Heavy Cluster Emission From Radioactive 230U Nuclei

230Pa was produced with the reaction ²³²TH (p, 3n)230Pa in the irradiation powder targets of ThO₂ with 35 MeV Proton beam. Sources of ²³⁰Pa -²³⁰U were prepared by radiochemical method. Using solid-state track registration detectors, two events of ²³⁰U decay with heavy cluster emission have been observed. The preliminary branching ratio to decay comes out to be B=λ_Ne/λ_α=(1.3±1.8)×10^－14.     

Investigation of the Scintillation Properties of Domestic BaF2(La) Crystal

BaF₂(La) crystal has been grown with 1% mole of BaF₃ doped in BaF₂ and the scintillation properties of the new crystal have been investigated before and after a γ irradiation of ⁶⁰Co source.The radiation resistance of the domestic crystal can be up to a dose of 10⁶ rad.Comparing with a pure BaF₂ scintillator,it was found that the fast component of the BaF₂(La) scintillator was almost no change but its slow component was suppressed to a factor of 4.     

Nanocrystalline growth and diagnostics of TiC and TiB2 hard coatings by pulsed laser deposition

Nanocrystalline coatings of TiC and TiB₂ were grown by pulsed laser deposition on Si(100) and on X155 steel at low substrate temperatures ranging from 40 °C to 650 °C. A pulsed KrF excimer laser was used with the deposition chamber at a base pressure of 10^-6 mbar. The morphology and structure of the films, studied with SEM, XRD, and TEM, showed that nanocrystalline films with a fine morphology of TiC and TiB₂ were deposited with a grain size of 10 nm-70 nm at all substrate temperatures. The growth of the polycrystalline coatings possessed a columnar morphology with a 𘜄¢ preferred orientation. The hardness of the coatings was determined to be 40 GPa and the elastic modulus, 240 GPa. The composition and the kinetics of the plume produced during the pulsed laser deposition of TiC and TiB₂ was studied under film growth conditions. The mass analysis of ions of the ejected material was performed by time-of-flight mass spectroscopy (TOF-MS) and showed the presence of Ti⁺ and C⁺ during TiC ablation and B⁺, B₂⁺, and Ti⁺ during TiB₂ ablation. The kinetic energies (KE) of the ions depended on the laser fluence which was between 0.5 eV and 340 eV. The kinetic energy and the evolution of the plasma was studied with a streak camera. The velocity of the plasma was of the order of 10⁶ cm/sec and was linearly dependent on the energy fluence of the laser. The emission spectroscopy of the plasma plume confirmed the atomic neutral and single excited species of Ti. These results show that coating growth basically occurs by the recombination of the ionic species at the surface of the substrate.     

Evolution of Structural Defects in SiOx Films Fabricated by Electron Cyclotron Resonance Plasma Chemical Vapour Deposition upon Annealing Treatment

We study the structural defects in the SiO, film prepared by electron cyclotron resonance plasma chemical vapour deposition and annealing recovery evolution. The photoluminescence property is observed in the as-deposited and annealed samples. [-SiO3]^2- defects are the luminescence centres of the ultraviolet photoluminescence （PL） from the Fourier transform infrared spectroscopy and PL measurements. [-SiO3]^2- is observed by positron annihilation spectroscopy, and this defect can make the S parameters increase. After 1000℃ annealing, [-SiO3]^2- defects still exist in the films.     

Resummation Study on Decay ρ→ππ in U(2)L×U(2)R Chiral Theory of Mesons

We improve O(p⁴) calculation in U(2)_L×U(2)_R chiral theory of mesons by resummation calculation for vector mesons physics and restudy decay ρ→ππ. We obtain a complete and compact expression for f_ρππ(p²) (up to O(p^∞)), from which an important non-perturbative conclusion is drawn from convergence and unitarity consideration.