Design of the low energy beam transport line for the China spallation neutron source

The design of the China Spallation Neutron Source (CSNS) low-energy beam transport (LEBT) line, which locates between the ion source and the radio-frequency quadrupole (RFQ), has been completed with the TRACE3D code. The design aims at perfect matching, primary chopping, a small emittance growth and sufficient space for beam diagnostics. The line consists of three solenoids, three vacuum chambers, two steering magnets and a pre-chopper. The total length of LEBT is about 1.74 m. This LEBT is designed to transfer 20 mA of H-pulsed beam from the ion source to the RFQ. An induction cavity is adopted as the pre-chopper.The electrostatic octupole steerer is discussed as a candidate. A four-quadrant aperture for beam scraping and beam position monitoring is designed.     

Multiple penetrating particles with narrow separation associated with extensive air showers (EAS)

An experiment has been carried out at a vertical depth of 580 m.w.e. at Kolar Gold Fields, to investigate various characteristics of energetic muons (E _mln ⋍ 150 GeV) associated with extensive air showers (EAS). Double parallel penetrating particles with narrow separations (<1m) have an exponential decoherence distribution withe-folding separation of ⋍ 25 cm.     

环境监测分析中校准曲线可靠性和检验方法的探讨

介绍了环境监测分析中校准曲线的分类、拟合方法和应用范围,提出了对拟合校准曲线进行可靠性检验的设想和建议的经验指标。如相对剩余标准差、截距、斜率检验、失拟方差检验等,这些方法在实际监测分析中具有一应用价值。     

New dynamic axial compression columns with means for monitoring floating adapter position. Column design and utilisation in low pressure LC on soft packings

Summary The design of new dynamic, axial-compression columns with a system for continous packed bed adjustment and monitoring of the floating adapter position is described. The columns are meant for liquid chromatography at low pressures (up to 8 bar) in aqueous and organic media with stationary phases of all types. The columns have adapter position pickups for continuous automatic monitoring of the bed height (original “swellographic” monitoring). The column described with gas pressurisation was tested with soft Sephadex G-10 and G-25. In spite of the reduction in external porosity there was no dramatic increase in back-pressure. The column proved to provide long-term stability of the packed bed and improvement in resolution. Presented at the 21^st ISC held in Stuttgart, Germany, 15^th–20^th September, 1996     

Membrane introduction mass spectrometry

An overview of membrane introduction mass spectrometry (MIMS) is presented and comparisons are made with other direct sample introduction techniques. Special attention is given to the unique advantages and the limitations of newer variants on the MIMS technique, including affinity MIMS, reverse-phase and trap MIMS. The salient features of the interfaces used in MIMS are summarized and the various membrane materials commonly used are delineated. The applicability of MIMS is illustrated via discussion of

1. (i) bioreactor monitoring (represented by yeast fermentation),

2. (ii) environmental monitoring (illustrated by analysis of contaminated ground water samples) and

3. (iii) on-line chemical reaction monitoring (exemplified by the photolysis of aryl esters).

The applicability of MIMS to the analysis of environmental samples, including complex mixtures in water, air and soil, is noted.     

Capillary gas chromatography of lower aliphatic C2?C5 aldehydes in the free form as a group of pungent odorants in air

The capillary gas chromatography of the C₂-C₅ lower aliphatic aldehydes (e.g.,acetaldehyde, propionaldehyde, n- and i-butyraldehydes, n- and i-valeraldehydes) which, in the free form in air, have unpleasant odors and low threshold odor values, has been studied using cold-trap preconcentration with liquid oxygen. The capillary column outlet was connected to enable simultaneous detection by FID, ECD, FPD AND FTD (SID).     

Proficiency testing schemes for therapeutics and toxicology

 This report addresses the proposition: current proficiency testing (PT) schemes for therapeutics and toxicology can easily engender complacency. The proposition was based on the premise that there are substantial between-laboratory differences and objectives in the supply of services for the measurement of drugs, as a result of which it is difficult to design PT schemes which adequately cover the requirements of all laboratories. Thus, acceptable performance in a PT scheme may lead participants to consider that they have tested their procedures more rigorously than is the case. Four areas, validity of the PT scheme, PT material, frequency of testing and acceptance criteria are examined. Received: 15 April 2000 · Accepted: 15 April 2000     

Chemical Kinetics Database and Predictive Schemes for Humid Air Plasma Chemistry. Part I: Positive Ion–Molecule Reactions

Reliable kinetic and thermodynamic data are required to model the evolution of electric discharge or electron-beam decomposition chemistry of gases in humid air streams. In this first segment of a continuing series, we provide a core database describing the initially dominant ion-neutral molecule reactions in humid air plasmas. Recommended reaction rate data and extrapolation tools are presented in a manner to facilitate prediction of reactivities and reaction channels as a function of temperature, pressure, and applied electric field.     

Sol-Gel Nanosized Semiconducting Titania-Based Powders for Thick-Film Gas Sensors

Pure, 5 at%, and 10 at% Ta- or Nb-doped TiO₂ nanosized powders were prepared by the sol-gel method. The powders heated to 400°C have the crystalline anatase structure. While the pure TiO₂ powder heated to 850°C has the rutile structure, the addition of Ta and Nb inhibited the anatase-to-rutile phase transformation at this temperature. Ta was soluble in the titania lattice up to the concentration of 10 at%, while the solubility of Nb was 5 at%. Thick films were fabricated with these powders by screen printing technology and then fired at 650°C and 850°C for 1 h. SEM observations showed that the anatase-to-rutile phase transformation induces a grain growth of about one order of magnitude for pure TiO₂. The addition of Ta and Nb is effective to keep the TiO₂ grain size at the nanometric level even at 850°C. Conductance measurements showed that a good gas response is observed only for the nanostructured titania-based films. The CO response of these materials is only slightly affected by humidity.