Practical 2.45-GHz microwave-driven Cs-free Hˉ ion source developed at Peking University

A practical 2.45-GHz microwave-driven Cs-free Hˉ source was improved based on the experimental Hˉ source at Peking University(PKU). Several structural improvements were implemented to meet the practical requirements of Xi'an Proton Application Facility(XiPaf). Firstly, the plasma chamber size was optimized to enhance the plasma intensity and stability. Secondly, the filter magnetic field and electron deflecting magnetic field were enhanced to reduce co-extracted electrons. Thirdly, a new two-electrode extraction system with farther electrode gap and enhanced water cooling ability to diminish spark and sputter during beam extraction was applied. At last, the direct Hˉ current measuring method was adopted by the arrangement of a new pair of bending magnets before Faraday cup(FC) to remove residual electrons. With these improvements, electron cyclotron resonance(ECR) magnetic field optimization experiments and operation parameter variation experiments were carried out on the Hˉ ion source and a maximum 8.5-mA pure Hˉ beam was extracted at 50 kV with the time structure of 100 Hz/0.3 ms. The root-mean-square(RMS) emittance of the beam is 0.25 Π·mm·mrad. This improved Hˉ source and extraction system were maintenance-free for more than 200 hours in operation.     

Laser-plasma extreme ultraviolet source at 6.7?nm using a rotating cryogenic Xe target

A laser-plasma source comprising a rotating cryogenic solid-state Xe target has been studied for use in extreme ultraviolet lithography (EUVL) systems equipped with La/B₄C mirrors. The laser-to-EUV power conversion efficiency (CE) of the cryogenic Xe target was improved to achieve a maximum CE of 0.15?% at 6.7?nm with 0.6?% bandwidth. We successfully demonstrated the continuous generation of EUV light with an average power of 80?mW at 6.7?nm with 0.6?% bandwidth using a Nd:YAG slab laser at a repetition rate of 320?Hz and an average power of 100?W. Scaling-up of the laser-plasma source for use as a future EUVL source is also discussed.     

Anisotropic intermolecular forces. I. Rare gas—hydrogen chloride systems

Anisotropic potential energy surfaces for Ne.HCl, Kr.HCl and Xe.HCl are obtained by simultaneous least squares fitting to molecular beam spectra and rotational line broadening cross sections. A revised potential surface for Ar.HCl is also presented. The potentials are all very similar in shape, with the absolute minimum at the linear rare gas-HCl geometry in each case. The absolute well depths and well depth anisotropies increase steadily as the size of the rare gas atom increases.

The potentials should be reliable in the region of the absolute minimum and on the repulsive wall of the potential. The molecular beam spectra for Ne.HCl can be fitted only by a potential with a significant secondary minimum at the linear Ne.Cl-H geometry, but the existing data for the more anisotropic Ar, Kr and Xe systems are not sensitive to the presence of this potential feature. The potential surfaces for these systems have accordingly been constrained to have a similar secondary minimum near the linear rare gas-ClH geometry. Experiments which would provide further information on the intermolecular potentials are suggested and predictions of the results are made.     

Accident at the Fukushima Dai-ichi Nuclear Power Stations of TEPCO —Outline & lessons learned—

The severe accident that broke out at Fukushima Dai-ichi nuclear power stations on March 11, 2011, caused seemingly infinite damage to the daily life of residents. Serious and wide-spread contamination of the environment occurred due to radioactive materials discharged from nuclear power stations (NPSs). At the same time, many issues were highlighted concerning countermeasures to severe nuclear accidents. The accident is outlined, and lessons learned are extracted with respect to the safety of NPSs, as well as radiation protection of residents under the emergency involving the accident. The materials of the current paper are those released by governmental agencies, academic societies, interim reports of committees under the government, and others.     

Anisotropic emission of charged mesons and structure characteristic of emission source in heavy ion collisions at 1-2A GeV

Angular distributions of pious and kaons produced in heavy ion collisions at the low-energy end of high energies （1-2 A GeV） have been investigated by using a multisource ideal gas model. The model covers the expansions and movements of the emission sources, and it is related to the collective flows. By using the analytic expression and the Monte Carlo method, the azimuthal and polar angle distributions of mesons are calculated by the model and compared with the experimental data of the KaoS Collaboration.     

Simulation of multiple scattering in argon ion collisions with an aluminum target at grazing angles of 5°–10°

A model for calculating the atom scattering from a polycrystalline surface consisting of randomly oriented single crystals is proposed. In the calculation it is possible to distinguish the contribution of scattering from any surface layer, and it also takes into account inelastic energy losses in primary ion collisions with target atoms. A comparison with the measurements shows that the proposed model well describes the peak positions in the energy spectra of the scattered atoms. A comparison of the calculated and experimental peak-to-background ratios for scattering from polycrystalline and amorphous targets allows a conclusion to be made about the degree of order of surface layers in the material under investigation.     

Quasi-point incoherent ArF<Superscript>∗</Superscript> excimer emission source at 193 nm using a laser-produced plasma

We have demonstrated proof-of-principle of an incoherent ArF^∗ emission source with a quasi-point emission geometry using a laser-produced plasma in an Ar/F₂/He/Ne mixed gas. The VUV emission characteristics, such as the emission size, were dependent on those of the plasma-initiating laser. The average emission power was 10 μW at a repetition rate of 10 Hz at 193 nm. The average power conversion efficiency of the 193-nm emission from the plasma-initiating Nd:YAG laser was 6.3×10⁻⁶. The average emission power at 193 nm was proportional to that of the plasma-initiating laser, indicating the scaling of the emission source.     

A narrow linewidth and frequency-stable probe laser source for the <Superscript>88</Superscript>Sr<Superscript>+</Superscript> single ion optical frequency standard

In this paper, we describe in detail a narrow linewidth and frequency-stable laser source used to probe the 5s ² S _1/2–4d ² D _5/2 clock transition of the ⁸⁸Sr⁺ optical frequency standard. The performance of the laser system is investigated with studies of its frequency drift rates and with high resolution spectra of the ⁸⁸Sr⁺ clock transition. The observed short-term drift rates are typically in the range of 10 to 23 mHz/s, and the current long-term drift rate is 13.9(3) mHz/s. The laser stability, after subtraction of linear drifts, reaches 5×10⁻¹⁶ at an averaging time of 3000 s. This high level of stability is attributed for the most part to stabilization of the reference cavity at the temperature where the coefficient of linear thermal expansion crosses zero. An upper bound for the laser linewidth is given by the observation of a Fourier-transform limited resonance of 4.3 Hz (Δν/ν=1×10⁻¹⁴) on the ⁸⁸Sr⁺ clock transition. The effective averaging time during the linewidth measurements was about 100 s.     

Calculations of O2 absorption and fluorescence at elevated temperatures for a broadband argon—fluoride laser source at 193 nm

Calculations have been made of O₂ absorption and fluorescence in the Schumann-Runge B³Σ^-_u←X³Σ^-_g band system for excitation by a broadband argon fluoride excimer laser at 193 nm. Results are presented for line strengths, spectral absorption coefficients, relative fluorescence spectra, total fluorescence and integrated absorption coefficients. The calculations have been performed for 300, 500, 1000, 1500 and 2000 K, a range of temperatures typically found in combustion flows. The absorption coefficients and fluorescence yields found are large enough to encourage use of argon fluoride lasers for O₂ measurements in a variety of flows.     

Atlas TRT—Research & design B-type module mass production

Collaboration efforts of the JINR TRT group, Russian institutions and the international scientific organizations in constructing the ATLAS Inner Detector TRT for LHC is summarized. R&D and TRT construction were accomplished during 1994–2007 at the Laboratory of Particle Physics of the Joint Institute for Nuclear Research (LPP JINR) and CERN.     

Radio frequency source power-induced ion energy impact on SiN films deposited by using a pulsed-PECVD in SiH4–N2 plasma at room temperature

Using a radio frequency (rf) pulsed-plasma enhanced chemical vapor deposition system, silicon nitride (SiN) films were deposited in a SiH₄–N₂ inductively coupled plasma. Effect of duty ratio and rf source powers on deposition rate at room temperature were investigated in the ranges 50–90% and 600–900 W, respectively. Plasma diagnostics on ion energy was conducted and rf source power-induced ion energy impact on SiN films were studied as well as some correlations between deposition rate and ion energy. High and low energies ranged from 17.8 to 22.6 eV, and from 23.6 to 33.8 eV, respectively. Higher ion energies observed at lower duty ratios or lower rf powers was attributed to a lower plasma density. Ion energy flux variation was opposite to that for ion energy. Meanwhile, the deposition rate increased with decreasing the duty ratio at all powers but 900 W. This was not clear as a function of rf source power. The deposition rate ranged from 17.0 to 26.5 nm/min.     

Modified fragmentation function in heavy ion collisions at RHIC via direct <Emphasis Type="Italic">γ</Emphasis>-jet measurements

The presented results are the first measurements at RHIC for direct γ-charged hadron azimuthal correlations in heavy ion collisions. We use these correlations to study the color charge density of the medium through the medium-induced modification of high-p _T parton fragmentation. Azimuthal correlations of direct photons at high transverse energy (8<p _T <16 GeV) with away-side charged hadrons of transverse momentum (3<p _T <6 GeV/c) have been measured over a broad range of centrality for Au+Au collisions and p+p collisions at  GeV in the STAR experiment. A transverse shower shape analysis in the STAR Barrel Electromagnetic Calorimeter Shower Maximum Detector is used to discriminate between the direct photons and photons from the decays of high p _T π ⁰. The per-trigger away-side yield of direct γ is smaller than from π ⁰ trigger at the same centrality class. Within the current uncertainty the I _CP of direct γ and π ⁰ are similar.     

<Emphasis FontCategory=NonProportional>WHIZARD</Emphasis>—simulating multi-particle processes at LHC and ILC

We describe the universal Monte-Carlo (parton-level) event generator WHIZARD (), version 2. The program automatically computes complete tree-level matrix elements, integrates them over phase space, evaluates distributions of observables, and generates unweighted partonic event samples. These are showered and hadronized by calling external codes, either automatically from within the program or via standard interfaces. There is no conceptual limit on the process complexity; using current hardware, the program has successfully been applied to hard scattering processes with up to eight particles in the final state. Matrix elements are computed as helicity amplitudes, so spin and color correlations are retained. For event generation, processes can be concatenated with full spin correlation, so factorized approximations to cascade decays are possible when complete matrix elements are not desired. The Standard Model, the MSSM, and many alternative models such as Little Higgs, anomalous couplings, or effects of extra dimensions or noncommutative SM extensions have been implemented. Using standard interfaces to parton shower and hadronization programs, WHIZARD covers physics at hadron, lepton, and photon colliders.     

From holes to sponge at irradiated Ge surfaces with increasing ion energy—an effect of defect kinetics?

We show that hole patterns and sponge-like layers at irradiated Ge surfaces originate from the same driving force, namely the kinetics of ion beam induced defects in the amorphous Ge surface layer. Ge hole patterns reported earlier for irradiation with low energy (5 keV) Ga⁺ ions were reproduced for low energy Bi⁺ but also for Ge⁺ self-irradiation, which proves that the dominating driving force for morphology evolution cannot originate from the implanted impurities. At higher ion energies the well-known formation of sponge-like Ge surface layers after heavy ion irradiation was found for Bi⁺ irradiation and Ge⁺ self-irradiation, also. The transition from smooth surfaces via hole patterns to sponge-like morphologies with increasing ion energies was studied in detail. A model based on the kinetics of ion beam induced defects was developed and implemented in 3D kinetic Monte Carlo simulations, which reproduce the transition from hole patterns to sponge-like layers with increasing ion energy.     

Investigation of the spatial profile of stimulated Raman scattering beams in D<Subscript>2</Subscript> and H<Subscript>2</Subscript> gases using a pulsed Nd:YAG laser at 266 nm

The stimulated Raman scattering (SRS) beam spatial mode structure is studied in H₂ and D₂ gases, in a 60 cm-long high-pressure Raman cell, using a pulsed Nd:YAG laser at 266 nm. The conversion efficiencies of the first and second Stokes in H₂, D₂ and H₂/D₂ mixtures have been measured precisely in the 1–14 atm range. The SRS beam profiles were recorded for different gas pressures in the high-pressure Raman cell and interesting behaviour is revealed. Homogeneous SRS spatial profiles were obtained only for pressures higher than 7 atm. For lower pressures the profiles are either in the form of a ring or of a more complicated shape. The results are explained in terms of nonlinear self-focusing processes during the pump beam propagation in the Raman cell. Also, from our measurements, a more precise value of the nonlinear index of refraction for the H₂ and D₂ at 266 nm is proposed. PACS 42.65.Dr; 42.60.Jf; 42.60.Lh; 42.65.Jx     

Charged <Emphasis Type="Italic">ρ</Emphasis>-meson production in neutrino-induced reactions at &lt;<Emphasis Type="Italic">E</Emphasis><Subscript><Emphasis Type="Italic">ν</Emphasis></Subscript>&gt;≈ 10 GeV

The production of charged ρ mesons on nuclei and nucleons is investigated in charged current neutrino interactions at moderate energies (〈E _〉 ≈ 10 GeV), using the data obtained with SKAT bubble chamber. No strong nuclear effects are observed in ρ ⁺ and ρ ^? production. The fractions of charged and neutral pions originating from ρ decays are obtained and compared with higher-energy data. From analysis of the obtained and available data on ρ ⁺ and K*⁺(892) neutrino production, the strangeness suppression factor is extracted: λ _s = 0.18 ± 0.03. Estimation is obtained for cross section of coherent ρ ⁺ neutrino production on nuclei.