Main linac lattice design and optimization for E_(cm)=1 TeV CLIC

The Compact Linear Collider(CLIC) is a future e+e- linear collider. The CLIC study concentrated on a design of center-of-mass energy of 3 TeV and demonstrated the feasibility of the technology. However, the physics also demands lower energy collision. To satisfy this, CLIC can be built in stages. The actual stages will depend on LHC results. Some specific scenarios of staged constructions have been shown in CLIC Concept Design Report(CDR). In this paper, we concentrate on the main linac lattice design for Ecm=1 TeV CLIC aiming to upgrade from Ecm=500 GeV CLIC and then to Ecm=3 TeV one. This main linac accelerates the electron or positron beam from9 GeV to 500 GeV. A primary lattice design based on the 3 TeV CLIC main linac design and its optimization based on the beam dynamics study will be presented. As we use the same design principles as 3TeV CLIC main linac, this optimization is basically identical to the 3 TeV one. All the simulations results are obtained using the tracking code PLACET.     

ON STRUCTURE OF MULTIPARTICLES IN QUARK JETS FOR e+e- COLLIDING

Inclusive distributions of longitudinal momentum and energy ((S/β) (dσ/dx_p⁾and (S/β) (dσ/dx_E⁾) in a quark jat for e⁺ e^- collidiny is calculated (√S～7GeV), fased onrandomly producing wee quarks and phase-space eonsideration. Excellent fits areobtained. In addition, a two-particle correlation dσ/(dx_IEdx_2E⁾ is also given, which ex-pects experimental tests.     

BEPCⅡ Positron Source

BEPCⅡ— an upgrade project of the Beijing Electron Positron Collider (BEPC) is a factory type of e^＋e^－ collider. The fundamental requirements for its injector linac are the beam energy of 1.89GeV for on-energy injection and a 40mA positron beam current at the linac end with a low beam emittance of 1.6μm and a low energy spread of ±0.5% so as to guarantee a higher injection rate (≥50mA/min) to the storage ring. Since the positron flux is proportional to the primary electron beam power on the target, we will increase the electron gun current from 4A to 10A by using a new electron gun system and increase the primary electron energy from 120MeV to 240MeV. The positron source itself is an extremely important system for producing more positrons, including a positron converter target chamber, a 12kA flux modulator, the 7m focusing module with DC power supplies and the support. The new positron production linac from the electron gun to the positron source has been installed into the tunnel. In what follows, we will emphasize the positron source design, manufacture and tests.     

Doublet bands in 128La and systematic features of energy separationof doublet bands observed in the A～130 mass region

High spin states of ¹²⁸La have been studied through the fusion-evaporation reaction ¹¹⁸Sn(¹⁴N, 4n)¹²⁸La at a beam energy of 69 MeV. A positive-parity side band with the same configuration as that of the yrast band has been identified. Moreover, it is noted that the energy separation ΔE(I)=E(I)_side-E(I)_yrast of all doublet bands reported in odd-odd nuclei in the A～130 mass region exhibit a staggering pattern systematically, and they stagger up at even-spin and stagger down at odd-spin.     

Yields of Charmed and Beautiful Mesons in e+e－ Annihilation at s=10—178GeV 的e+e-

Based on the electroweak unified standard model,the probability P_i for the production of i-quark jet (i=u,d,c and b)in e⁺e^－ annihilation has been studied.The probability P_i is a function of energy s.The calculated component ratios of P_u:P_d:P_s:P_c:P_b are 4:1:1:4:1 for s<30GeV.7:9:9:7:9 for s=m_z=91.16GeV and 1:1:1:1:1 for s=78 and 117GeV,respectively.Using P_c and P_b,we whave calculated the yields of charmed and beautiful mesons in e⁺e^－ annihilation at s=10—178GeV.     

New band structures in 107Ag

High spin states in ¹⁰⁷Ag are studied via the ¹⁰⁰Mo(¹¹B, 4n)¹⁰⁷Ag reaction at an incident beam energy of 60 MeV. Prompt γ-γ coincidence and DCO ratios are measured by the detector arrays in CIAE. The level scheme has been updated and a new negative band belonging to ¹⁰⁷Ag is identified. The new negative side band has been constructed and its configuration is tentatively assigned to πg_9/2 νh_11/2(g_7/2/d_5/2).     

Measurement of Michel Parameter in τ Decay

We have analysed the e⁺e^－ collision data collected with Beijing Spectrometer at the center-of-mass energy 4.03 GeV and selected e⁺e^－→τ^±τ⁺→e^±X⁺v's events, X^± required as μ^±、π^± and ρ^±. From fitting electron energy spectrum in τ→ev's decay, the measurement value of Michel parameter is given as ρ_τ→e=0.705, this result is in good agreement with the prediction of standrd Model.     

立方氮化硼的振动光谱及反射光谱的研究

 将黑色、黄色、棕色三种小于50 μm立方氮化硼粉末为样品，研究了其红外光谱、拉曼光谱、反射光谱，结果表明：（1）样品的红外光谱中，1 818 cm^-1和1 548 cm^-1属于cBN的晶格本征振动，而立方氮化硼的晶格本征振动外的晶体缺陷吸收则发生在~800 cm^-1，1 580 cm^-1~1 740 cm^-1和大于2 400 cm^-1处。（2）拉曼光谱测试表明，在1 052 cm^-1和1 304 cm^-1附近出现的散射与cBN不具有反演中心及cBN具有立方结构这样的事实相一致，并且这种散射伴随着布里渊区中心声子的横向和纵向发射。144 cm^-1附近出现的散射，被认为是由于局部振荡模式的出现，在反斯托克斯区造成的信号，这与晶格中杂质缺陷有关。（3）依据得到的反射光谱，计算了cBN单晶禁带宽度，发现这三种cBN都具有大于金刚石的禁带宽度值，分别为：E_g(黑)=6.21 eV，E_g(黄)=5.73 eV，E_g(棕)=5.71 eV。     

PROTOTYPE OF END CAP SHOWER COUNTERAND ITS BEAM TEST

A gas sampling Em Shower counter of the lead-SQS tube sandwich type was constructed and tested. The Shower counter uses Aluminium tubes and anode readout. Energy resolution σ/E is 15.5% at E_e=1GeV. Range of the energy response linearity is 0—2GeV. This paper describes the beam test and the performance studied under various conditions.     

Mixing between the 23S1 and 13D1 Ds

Mixing between the 2³S₁ and 1³D₁ D_s is studied within the ³P₀ model. If mixing between these two 1^- states exists, D_s1^*(2700)^± and D_sJ^*(2860)^± could be interpreted as the two orthogonal mixed states with mixing angle θ≈ -80° in the case of a special β for each meson. However, in the case of a universal β for all mesons, D_s1^*(2700)^± could be interpreted as the mixed state of 2³S₁ and 1³D₁ with mixing angle 12° < θ < 21° but D_sJ^*(2860)^± seems difficult to interpret as the orthogonal partner of D_s1^*(2700)^±.     

Scale for the Production of Jets in High Energy e+e－ Collisions

The scale for visible jets produced in e⁺e^－ Collisions is studied in some details using Monte Carlo method. It is demonstrated, based on the historical fact that the 3-jet events were firstly observed in e+ e- experiments at √S=17—30GeV,and the relative transverse momentum for visible jets is in the region k_t,～5—10GeV/c. It is further shown, using a concrete example, that the number of jets in an event could be correctly evaluated only when k_t is in this region. The dynamical fluctuations inside jets determined through different values of k_t are compared carefully. It turns out that only when k_t,～5—10GeV/c the dynamical fluctuations inside jets will possess the best anomalous scaling property. The relation between the scale 5-10GeV/c of visible jets and the scale 1-2GeV of perturbative QCD is discussed.     

Raman Investigation of Sodium Titanate Nanotubes under Hydrostatic Pressures up to 26.9GPa

High pressure behavior of sodium titanate nanotubes （Na2Ti2O5） is investigated by Raman spectroscopy in a diamond anvil cell （DAC） at room temperature. The two pressure-induced irreversible phase transitions are observed under the given pressure. One occurs at about 4.2 GPa accompanied with a new Raman peak emerging at 834 cm-1 which results from the lattice distortion of the Ti-O network in titanate nanotubes. It can be can be assigned to Ti-O lattice vibrations within lepidocrocite-type （H0.7Ti1.825V0.175O4＆#12539;H2O）TiO6 octahedral host layers with V being vacancy. The structure of the nanotubes transforms to orthorhombic lepidocrocite structure. Another amorphous phase transition occurs at 16.7 GPa. This phase transition is induced by the collapse of titanate nanotubes. All the Raman bands shift toward higher wavenumbers with a pressure dependence ranging from 1.58-5.6 cm-1/GPa.     

SHAPE MEASUREMENT OF SYNCHROTRON RADIATION WITH HIGH TIME RESOLUTION

By using BWS-5k II streak camera made in China,we have measured the time structure of Synchrotron Radiation (SR) from the relatrivistic electron and positron beam bunches of Beijing Electron Positron Collider (BEPC).The dependence of SR width to the intensity of beam current and the voltage of RF source was also measured.The main data taken with 30ps time resolution in the experiment are as follows: The length of VR at E_e=1.549GeV is changed from 220ps to 670ps when the average beam current from 2mA to 30mA,the variation range of CR length at 20mA beam current is 500—700ps with RF source voltage varying between 250kV and 500kV.The time calibration uncertainty of the experiment is ±15%.The trigger jitter is less than ±200ps.     

Upper limit to the cross-section for the process νμ + e− → νμ + e−

An upper limit of 3 × 10^?42E_ν cm² per electron, at 90% confidence level, has been obtained for the cross section of the process ν_μ + e^? → ν_μ + e^?, interpreted in the usual V-A framework, for an electron recoil energy larger than 0.3 GeV. This estimate is based on the observation of one candidate event in exposures of Gargamelle to the CERN PS neutrino beam.     

Defect generation in polycrystalline Cu(In,Ga)Se2 by high-energy electron irradiation

We investigate the degradation of ZnO/CdS/ Cu(In,Ga)Se₂ heterojunction solar cells for space applications and the defect generation in polycrystalline Cu(In,Ga)Se₂ thin films by irradiation with 1-MeV electrons with fluences J_e up to J_e=5᎒¹⁸ cm^-2. Notable degradation of the solar cell performance starts at fluences of J_e=10¹⁷ cm^-2 where the open circuit voltage decreases by about 5% while short circuit current and fill factor remain essentially unaffected. Thus, Cu(In,Ga)Se₂ solar cells withstand electron fluences which are higher by one order of magnitude or more when compared to other technologies. A model describes the absolute open circuit voltage loss considering the increase of space charge recombination by electron irradiation-induced defects. Defect analysis by admittance spectroscopy shows that acceptor defects with an energy distance of approximately 300 meV from the valence band are generated at a rate %=0.017 (ǂ.01) cm^-1.     

Dielectronic Recombination of Sn^10＋ Ions and Related Satellite Spectra

Based on the multi-configuration Dirac-Fock method, theoretical calculations are carried out for the dielectronic recombination （DR） rate coefficients and the collision excitation rate coefficients of Sn^10＋ ions. It is found that the total DR rate coefficient has its maximum value between 10eV and 100eV and is greater than either the radiative recombination or three-body recombination rate coefficients （the number of free electrons per unit is 10^21 cm^3） for the ease of Te 〉 1 eV. Therefore, DR can strongly influence the ionization balance of laser produced multi-charged tin ions. The related dieleetronie satellite cannot be ignored at low temperature Te 〈 5 eV.     

Lifetime measurement of the first excited state of 64Ga

The half-life of the first excited state of ⁶⁴Ga has been measured with a pulsed beam technique. The half-life was determined to be T_1/2 = 21.9 - 0.7 7s. The corresponding B(E2) = 13.6 - 0.4 e²fm⁴ shows good agreement with the Weisskopf estimate, i.e., 15.2 e²fm⁴, thereby establishing the 2⁺ assignment to this state and the single particle nature of the 42.89 keV transition.     

An overview of design for CSNS/RCS and beam transport

The China Spallation Neutron Source (CSNS) is the first accelerator-based pulsed neutron source in China. Its accelerators are made up of an 80 MeV H⁻ linac, a Rapid Cycling Synchrotron (RCS) and two beam transport lines. RCS accumulates and accelerates protons to the design energy of 1.6 GeV, and extracts high energy beam to strike the target. The overview of RCS is presented, and the key problems of the physics design are discussed. The two beam transport lines, from linac to RCS and from RCS to the target, are also introduced.

     

ANALYSIS OF HADRONIC EVENTS

In this paper I summarize some results obtained from analyses of hadronic final state events. The analyzed data sample comes from Mark-J collaboration and covers an energy range from √S=12GeV to √S =46.78GeV. The integrated luminosity is 128.06Pb^－1. We can search for production of open top quarks and toponium by measuring the total hadronic crossection R =3.85±0.02±0.12 was measured in the above mentioned energy range. It is consistent with R≈3.9 as expected from QCD for five different quark flavors. We search for the narrow bound states of the toponium from 39.79GeV to 46.78GeV. The most prominent resonance signal is at a c.m. energy √S=45.12±0.04GeV and results in an upper limit of B_h.Γ_ee≤3.00keV(95% C.L.).     

Atomic Diffusion in Cu/Si （111） and Cu/SiO2/Si （111） Systems by Neutral Cluster Beam Deposition

The Cu films are deposited on two kinds of p-type Si （111） substrates by ionized duster beam （ICB） technique. The interface reaction and atomic diffusion of Cu/Si （111） and Cu/SiO2/Si （111） systems are studied at different annealing temperatures by x-ray diffraction （XRD） and Rutherford backscattering spectrometry （RBS）. Some significant results are obtained： For the Cu/Si （111） samples prepared by neutral dusters, the interdiffusion of Cu and Si atoms occurs when annealed at 230℃. The diffusion coefficients of the samples annealed at 230℃ and 500℃ are 8.5 ×10^-15 cm^2.s^-1 and 3.0 ×10^-14 cm^2.s^-1, respectively. The formation of the copper-silicide phase is observed by XRD, and its intensity becomes stronger with the increase of annealing temperature. For the Cu/SiO2//Si （111） samples prepared by neutral dusters, the interdiffusion of Cu and Si atoms occurs and copper silicides are formed when annealed at 450℃. The diffusion coefficients of Cu in Si are calculated to be 6.0 ×10^-16 cm^2.s^-1 at 450℃, due to the fact that the existence of the SiO2 layer suppresses the interdiffusion of Cu and Si.