Vacuum Line Research Articles

Status of Sample Combustion and Graphitization Lines at INFN-LABEC, Florence

Since installation of the new accelerator at INFN-LABEC in Florence in 2004, the workload has progressively increased in the radiocarbon dating laboratory, requiring a faster sample preparation throughput and greater versatility to allow for a larger variety of treated materials. The “standard” sample preparation line is based on an elemental analyzer (EA) for the combustion of the pretreated samples, and a vacuum line where the CO2 is collected and then converted to graphite. This line has been recently redesigned while maintaining the EA, since this instrument provides us reliable and fast sample combustion and separation of gases. The volumes were optimized and all the mechanical parts (e.g. the fittings) were changed in order to improve the vacuum level, thus decreasing the possibility of contamination; finally, the number of graphitization reactors was doubled (from 4 to 8). In those rare cases involving samples characterized by a complex nearly graphitic structure (e.g. burnt residues), the EA might not guarantee a complete combustion. For these samples, we successfully tested the new sample preparation line that has been recently installed at LABEC and especially dedicated to aerosol samples. This line is equipped with a custom-made combustion oven able to heat to 1000 ×C. The subsequent gas separation is accomplished by chemical and thermal traps. As an example, the dating of organic matter collected from an Etruscan bronze statue will be presented and discussed. DOI: 10.2458/azu_js_rc.55.16256

Accelerator Vacuum Protection System

A new and elaborate automatic vacuum protection system using fast acting valve has been installed to avoid accidental venting of accelerator from experimental chamber side. To cover all the beam lines and to reduce the system cost, it has been installed at a common point from where all the seven beam lines originate. The signals are obtained by placing fast response pressure sensing gauges (HV SENSOR) near all the experimental stations. The closing time of the fast valve is 10 milli-second. The fast closing system protects only one vacuum line at a time. At IUAC, we have seven beam lines so one sensor was placed in each of the beam lines near experimental chamber and a multiplexer was incorporated into the fast closing system. At the time of experiment, the sensor of the active beam line is selected through the multiplexer and the Fast closing valve is interlocked with the selected sensor. As soon as the pressure sensor senses the pressure rise beyond a selected pressure, the signal is transferred and the fast valve closes within 10 to 12 millisecond.

Propagation of a magnetic insulation wave in a vacuum line with a bias current

An analytic model is developed and numerical simulation is performed for the operation of a vacuum coaxial line with a bias current. The results of computations make it possible to determine the bias current preventing electron leakage at the front of an incident voltage wave and to predict the “hot” line impedance. This model forms the basis of the method for determining the voltage across a vacuum load with the help of a short-circuited coaxial line with a bias current.

An Accessible Mercury-Free Vacuum Schlenk Line for Air-Free Techniques

A vacuum Schlenk line is essential for teaching some air-free laboratory techniques. Conventional variations of this apparatus in the inorganic laboratory employ mercury bubblers, which makes them unsuitable for institutions seeking to eliminate mercury. This communication describes an effective modification of a vacuum line system that can be set up with minimal time and effort.

7.3: Distinquished Paper: Ultra‐Thin Shadow‐Mask PDP Fabricated by Vacuum In‐line Sealing Technology

AbstractAn ultra‐thin shadow mask plasma display panel is put forward to meet the market demands of a much thinner, lighter and flexible display. Thanks to the ultra‐thin 70μm thick glass, a special vacuum in‐line sealing technology could be used to fabricate the novel device without a pumping tube. The sealed panel is only 300μm thick. The sealing characteristics and the discharge characteristics are investigated. The experimental results indicate that a high ratio of Xe in the gas mixture can be used, thereby improving the performance of the ultra‐thin SMPDP. In future applications AF32 type of foil glass will be used with a dielectric constant of 5.1. In addition a sealing temperature of 600 °C or higher will enable to exploit the full benefits of MgCaO protective layer. The ultra‐thin panel is well suited both for a double‐sided display and for 3D‐display.

Status report of AMS sample preparation laboratory at GADAM Centre, Gliwice, Poland

The laboratory for 14C AMS sample preparation in the Gliwice Radiocarbon Laboratory has gradually evolved since its start in 1999 to cater for an increase in volume and variety of radiocarbon dating samples. To date, nearly 2000 graphite targets have been produced from materials such as plant macrofossils, charcoal, peat, bones, shells and wood. The equipment comprises a station for chemical preparation and high vacuum lines for production, purification and graphitization of sample carbon dioxide. The present capacity allows preparation of up to 400 targets annually for the needs of scientific projects and external orders for radiocarbon dating continuously received by the GADAM Centre of Excellence. The laboratory’s sample preparation protocols and recent improvements are described and its performance during the 10years of activity is discussed in terms of parameters obtained from reference materials prepared in this laboratory and demonstrated with a few science applications.

Analytical studies of the heat removal capability of a passive auxiliary feedwater system (PAFS)

As passive safety features for nuclear power plants receive increasing attention, various studies have been conducted to develop safety systems for third-generation (GEN-III) nuclear power plants that are driven by passive systems, such as natural circulation, gravity, and resistance to high temperatures. Thus, South Korea has designed the Advanced Power Reactor Plus (APR+) with a two-loop PWR and 1500 MWe by adding passive safety features to the Advanced Power Reactor 1400 MWe (APR1400). The Passive Auxiliary Feedwater System (PAFS) is one of several passive safety systems being designed for the APR+, and extensive studies are being conducted to complete its design and to verify its feasibility. Because the PAFS removes decay heat from the reactor core under transient and accident conditions, it is necessary to evaluate the heat removal capability of the PAFS under hypothetical accident conditions. Therefore, in this paper, after introducing the characteristics of the PAFS and its design requirements, a performance analysis of the PAFS is performed for two accident cases: Loss of Condenser Vacuum (LOCV) and Feedwater Line Break (FLB). For the analysis, the Multi-dimensional Analysis of Reactor Safety (MARS) code is used, and a MARS model is developed by adding the PAFS model to the existing APR1400 model. The analysis results show that the PAFS has enough capacity to remove decay heat under the postulated accident conditions. In addition, the adequacy of modified control logic for main steam isolation valve (MSIV) is validated by comparing the traditional control logic.

Study and Optimization on graft polymerization under normal pressure and air atmospheric conditions, and its application to metal adsorbent

Radiation-induced graft polymerization of glycidyl methacrylate (GMA) onto non-woven polyethylene (NWPE) fabric was achieved under normal pressure and air atmospheric conditions, without using unique apparatus such as glass ampoules or vacuum lines. To attain graft polymerization under normal pressure and air atmospheric conditions, the effects of the pre-irradiation dose, pre-irradiation atmosphere, pre-irradiation temperature, de-aeration of GMA-emulsion, grafting atmosphere in a reactor, and dissolved oxygen (DO) concentration in GMA-emulsion on the degree of grafting (Dg) were investigated in detail. It was found that the DO concentration had the strongest influence, the pre-irradiation dose, de-aeration of emulsion and grafting atmosphere had a relatively strong impact, and the pre-irradiation atmosphere and pre-irradiation temperature had the least effect on Dg. The optimum DO concentration before grafting was 2.0mg/L or less. When a polyethylene bottle was used as a reactor instead of a glass ampoule, graft polymerization under normal pressure and air atmospheric conditions could be achieved under the following conditions; the pre-irradiation dose was more than 50kGy, the volume ratio of GMA-emulsion to air was 50:1 or less, and the DO concentration in GMA-emulsion during grafting was below 2.0mg/L. Under these grafting conditions, Dg was controlled within a range of up to 362%. The prepared GMA–grafted NWPE (GMA–g-NWPE) fabric was modified with a phosphoric acid to obtain an adsorbent for heavy metal ions. In the column-mode adsorption tests of Pb(II), the adsorption performance of the produced phosphorylated GMA–g-NWPE fabric (fibrous metal adsorbent) was not essentially dependent on the flow rate of the feed. The breakthrough points of 200, 500, and 1000h−1 in space velocity were 483, 477 and 462 bed volumes, and the breakthrough capacities of the three flow rates were 1.16, 1.15 and 1.16mmol-Pb(II)/g-adsorbent.

Lithography: A Portable, Benchtop Photolithography System Based on a Solid‐State Light Source (Small 22/2011)

Solid-state photolithography (SSP) enables the capabilities of one of the most important tools in nano- and microfabrication, the mask aligner, to be performed on the benchtop. SSP can create patterns over a wide range of different length scales (down to several hundred nanometers) and over macroscale areas at a fraction of the cost of current instruments. The design of the SSP system alleviates the need for dedicated power supplies, vacuum lines, and cooling systems, and thus makes SSP a compact and portable photolithography option. The cover image is a close-up of the ultraviolet light-emitting diode (LED) array that is used as the solid-state light source for SSP. It is anticipated that SSP will expedite the integration of sub-wavelength patterns and microscale devices such as microfluidic channels into diverse research areas. For more information, please read the Communication “A Portable, Benchtop Photolithography System Based on a Solid-State Light Source” by M. D. Huntington and T. W. Odom,* beginning on page 3144.

Thermal Analyses of Blends of Hyperbranched Linear Low-density Polyethylene (LLDPE) with High-density Polyethylene and LLDPE Prepared by Dissolving Method

Blends of high-density polyethylene (HDPE), moderate and hyper-branched LLDPEs (LLDPE and HbPE, respectively) have attained widespread commercial applications, though the understanding of the mechanical and melt-flow properties of such blends has been handicapped by the absence of a consensus concerning the degrees of mixing of the components. Moreover, usually the blends are obtained by melt blending, which may not ensure the initial homogeneity of the components. In our work the mixtures were prepared by dissolving the conventional LLDPE having branching content 7.2 wt% with HbPE with comonomer content 17.8 wt% in xylene at 130 °C and stirring for 2 hours. The same procedure was applied for the blending of HDPE with HbPE. After dissolving the mixtures were cooled in liquid nitrogen and after that freeze dried in vacuum line. The ratio of components in the blends was varied. Differential scanning calorimetry has been used to investigate the miscibility and thermal behavior of the blends. For this purpose isothermal and non-isothermal treatment of prepared blends were conducted. By preliminary study the double melting peaks in non-isothermal endotherms have been observed in all the studied blends. The presence of two peaks in DSC scan can be attributed to the formation of separated crystals from both the high density/linear low density and highly branched components. However, certain limited degree of co-crystallization is detected in all the LLDPE/HbPE blends and HDPE/HbPE blend rich in HbPE component.http://dx.doi.org/10.5755/j01.ms.17.3.589

Pyrolytic Decomposition of Ammonia Borane to Boron Nitride

The thermal decomposition of ammonia borane was studied using a variety of methods to qualitatively identify gas and remnant solid phase species after thermal treatments up to 1500 °C. At about 110 °C, ammonia borane begins to decompose yielding H(2) as the major gas phase product. A two step decomposition process leading to a polymeric -[NH═BH](n)- species above 130 °C is generally accepted. In this comprehensive study of decomposition pathways, we confirm the first two decomposition steps and identify a third process initiating at 1170 °C which leads to a semicrystalline hexagonal phase boron nitride. Thermogravimetric analysis (TGA) was used to identify the onset of the third step. Temperature programmed desorption-mass spectroscopy (TPD-MS) and vacuum line methods identify molecular aminoborane (H(2)N═BH(2)) as a species that can be released in appreciable quantities with the other major impurity, borazine. Attenuated total reflectance Fourier transform infrared spectroscopy (ATR-FTIR) was used to identify the chemical states present in the solid phase material after each stage of decomposition. The boron nitride product was examined for composition, structure, and morphology using scanning Auger microscopy (SAM), powder X-ray diffraction (XRD), and field emission scanning electron microscopy (FESEM). Thermogravimetric Analysis-Mass Spectroscopy (TGA-MS) and Differential Scanning Calorimetry (DSC) were used to identify the onset temperature of the first two mass loss events.

ChemInform Abstract: 1H-Bicyclo(3.1.0)hexa-3,5-dien-2-one. A Strained 1,3-Bridged Cyclopropene.

and CD3C6D5 (0.100 M) in benzene were prepared in an inert atmosphere box, placed in a vacuum transfer tube, degassed, and stored under argon. Weighed samples of (TMP)Rh-CH, were placed into vacuumadapted NMR tubes, dissolved in benzene, and irradiated in a Rayonnet photoreactor for 6 h (A 2 350 nm) to form (TMP)Rh'. The solvent was then pumped off and 0.5 mL of the toluene stock solution syringed in under argon. The NMR tubes were then attached to a vacuum line and subjected to three freeze-pumpthaw cycles and sealed under vacuum. The samples were subsequently heated in a constant-temperature oil bath, and the concentration of the constituents was periodically monitored by 'H NMR. Linearity of plots for [(TMP)Rh']-' versus time and variation of the toluene concentration indicate that the rate law for reaction 5 is second order in [(TMP)Rh'] and first order in toluene (ratef(,) = k5[(TMP)Rh*]2[CH~C6H,]). [(TXP)Rh], with CH,. Relative concentrations of [(TXP)Rh],,

Temperature-Dependent Density and Viscosity of the Ionic Liquids 1-Alkyl-3-methylimidazolium Iodides: Experiment and Molecular Dynamics Simulation

The density and viscosity of synthesized 1-alkyl-3-methylimidazolium iodide ([Cnmim]I, n = 4, 6, 8) were measured in the wide range of temperature of (298 to 393) K. Using a vacuum line, measurements of the viscosity were made under a water-vapor free atmosphere. The viscosity decreases sharply with temperature and increases as the alkyl chain length increases. The molecular dynamics simulation was performed for the densities of these ionic liquids to remedy the lack of literature experimental data. The results are quite in agreement with the experiments, with a maximum deviation of 3.00 % due to [C8mim]I at 358 K. The viscosities fit best in the modified Arrhenius, Vogel−Fulcher−Tammann (VFT), and Litovitz equations. The viscosities also fit in the simple linear equation we proposed recently with accuracies comparable with Litovitz and VFT.

Experiments and geochemical modelling of CO2 sequestration by olivine: Potential, quantification

Aqueous solutions equilibrated with supercritical CO(2) (150 degrees C and total pressure of 150 bar) were investigated in order to characterize their respective conditions of carbonation. Dissolution of olivine and subsequent precipitation of magnesite with a net consumption of CO(2) were expected. A quantified pure mineral phase (powders with different olivine grain diameter [20-80 mu m], [80-125 mu m], [125-200 mu m] and [>200 mu m]), CO(2) (as dried ice) were placed in closed-batch reactors (soft Au tubes) in the presence of solutions. Different salinities (from 0 to 3400 mM) and different ratios of solution/solid (mineral phase) (from 0.1 to 10) were investigated. Experiments were performed over periods from 2 to 8 weeks. Final solid products were quantified by the Rock-Eval 6 technique, and identified using X-ray diffraction, Raman spectroscopy, electron microprobe and scanning electron microscopy. Gaseous compounds were quantified by a vacuum line equipped with a Toepler pump and identified and measured by gas chromatography (GC). Carbon mass balances were calculated. Olivine reacted completely with CO(2), trapping up to 57 +/- 2% (eqC of initial CO(2)) as magnesite; some amorphous silica also formed. Olivine grain diameter and solution/mineral ratios appeared to be the primary controls on the reaction, salinity acting as a second order parameter. During the experiments, fluid analyses may not be performed with approach adopted but, geochemical modelling was attempted to give information about the solution composition. This showed an interesting mineral matrix evolution. Under the experimental conditions, olivine appeared to be a good candidate for CO(2) trapping into a geologically stable carbonate, magnesite. The possible use of mafic and ultramafic rocks for CO(2) sequestration is discussed.

Grafting of polymer brushes from nanopore surface via atom transfer radical polymerization with activators regenerated by electron transfer

It is shown that atom transfer radical polymerization (ATRP) with activators regenerated by electron transfer (ARGET) is a powerful approach for grafting of polymer brushes from surfaces of high-surface-area nanoporous hosts, allowing one to achieve controlled polymer loadings and film thicknesses while maintaining the pore accessibility and moderate or high surface area. The approach was illustrated on SBA-15 silicas with cylindrical pores of diameter 22 and 14 nm as the nanoporous supports, and poly(methyl methacrylate) (PMMA) and polystyrene (PS) as the grafted polymers. The polymer loadings up to 36 wt.% and the grafted layer thicknesses of up to at least 2 nm were achieved in the polymerization process carried out in small vials without using a vacuum line. The specific surface areas of the obtained silica-polymer composites were 60–190 m2 g−1. The polymer chains exhibited quite low polydispersity (1.18–1.32) for polymer loadings up to 29 wt.%, while a higher polydispersity was observed for higher loadings, in which case the pores of the support were filled to a significant extent with the polymer graft. Due to its simplicity, ARGET ATRP emerges as a powerful and yet surprisingly straightforward way to synthesize well-defined polymer brushes in nanopores, opening a convenient avenue to a wide range of porous high-surface-area silica-polymer composites.

Developing Ultra Small-Scale Radiocarbon Sample Measurement at the University of Tokyo

We have developed accelerator mass spectrometry (AMS) measurement techniques for ultra small-size samples ranging from 0.01 to 0.10 mg C with a new type of MC-SNICS ion source system. We can generate 4 times higher ion beam current intensity for ultra-small samples by optimization of graphite position in the target holder with the new ionizer geometry. CO2 gas graphitized in the newly developed vacuum line is pressed to a depth of 1.5 mm from the front of the target holder. This is much deeper than the previous position at 0.35 mm depth. We measured 12C4+ beam currents generated by small standards and ion beam currents (15–30 μA) from the targets in optimized position, lasting 20 min for 0.01 mg C and 65 min for 0.10 mg C. We observed that the measured 14C/12C ratios are unaffected by the difference of ion beam currents ranging from 5 to 30 μA, enabling measurement of ultra-small samples with high precision. Examination of the background samples revealed 1.1 μg of modern and 1 μg of dead carbon contaminations during target graphite preparation. We make corrections for the contamination from both the modern and background components. Reduction of the contamination is necessary for conducting more accurate measurement.

A New Automated Extraction System for 14C Measurement for Atmospheric Co2

The radiocarbon content of atmospheric CO2 (Δ14CO2) has long been of interest to atmospheric and Earth system researchers. Recent improvements in 14C measurement precision and reduction in sample size requirements have now made it possible to measure Δ14CO2 within existing trace gas sampling networks, most notably as a method to quantify recently added fossil-fuel-derived CO2 in the atmosphere. At INSTAAR, in collaboration with NOAA/ESRL, ∼600 atmospheric samples from around the globe are prepared each year, and that number is anticipated to grow in connection with various monitoring and data assimilation efforts. To accommodate the growing demand and reduce per sample costs, we developed an automated extraction system to quantitatively isolate CO2 from whole air for AMS 14C analysis. Twenty samples can be extracted in 1 fully automated run, taking 10–12 hr to complete and requiring only about 1 hr of operator time, a substantial improvement over the manual extraction system. CO2 is extracted cryogenically by flowing the whole air over a liquid nitrogen trap, after first removing water in a trap at –85 °C. Large volume vacuum lines are used to extract ∼30 μmol of CO2 in less than 10 min, keeping contamination from leaks to a minimum and allowing rapid processing and greater throughput. δ13C measurements on the resultant CO2 demonstrate that extraction is quantitative, and extractions of 14C-free air show that no significant modern contamination occurs. Replicate analyses of standard materials indicate that both mean values and precision are comparable to those for the manual extraction system.

Synthesis and Microwave Spectrum of (2-Chloroethyl)phosphine (ClCH2CH2PH2)

The synthesis of a 2-halogenoethylphosphine, (2-chloroethyl)phosphine (ClCH(2)CH(2)PH(2)), is reported for the first time. This compound was prepared by a chemoselective reduction of diethylchloroethylphosphonate with dichloroalane using a vacuum line. (2-Chloroethyl)phosphine has been studied by microwave spectroscopy at room temperature, or at -20 degrees C, in the 22-80 GHz spectral interval. The experimental study has been augmented by quantum chemical calculations at the MP2/6-311++(3df,3pd) and B3LYP/6-311++(3df,3pd) levels of theory. The spectra of two rotameric forms, denoted I and II have been assigned. These conformers both have an antiperiplanar arrangement for the Cl-C-C-P chain of atoms, but with different orientation of the phosphine group. Conformer I was found to be 5.2(6) kJ/mol more stable than II by relative intensity measurements. The spectra of the first excited states of the C-C torsional vibration of both I and II were assigned. The torsional frequency was determined to be 63(20) cm(-1) for conformer I by relative intensity measurements, and it has a similar value in II. It was found that this normal vibration deviates from a near-harmonic behavior. The quantum chemical calculations produce rotational and centrifugal distortion constants that are in satisfactory agreement with observations, but fail to predict correctly low-frequency fundamental frequencies. The quantum chemical calculations indicate that three additional conformers characterized by a synclinal orientation for the Cl-C-C-P link of atoms and with different orientation of the phosphine group are high-energy forms of ClCH(2)CH(2)PH(2). Searches for these forms were unsuccessful.

Vapor Pressure Measurements of Hydroxyacetaldehyde and Hydroxyacetone in the Temperature Range (273 to 356) K

Vapor pressures of ethylene glycol, hydroxyacetaldehyde, and hydroxyacetone were measured by using a standard closed system equipped with a vacuum line, built recently in our laboratory. First, our vapor pressures measurements of ethylene glycol and their excellent agreement with the literature in the studied temperature range, that is, (308 to 385) K, permitted us to validate our experimental setup and procedure. The data obtained in the temperature ranges of (296 to 356) K and (273 to 304) K were very satisfactorily (absolute relative deviations (ARD) < 2.5 %) fitted according to the Antoine’s equation: log10(P°hydroxyacetaldehyde/Pa) = 12.96 ± 0.82 − (3657 ± 238)/(T/K) and log10(P°hydroxyacetone/Pa) = 10.13 ± 0.06 − (2201 ± 153)/(T/K). Then, the resulting vapor pressures of both hydroxyacetaldehyde and hydroxyacetone at 293 K were P° = (3.0 ± 0.2) Pa and P° = (415 ± 20) Pa for hydroxyacetaldehyde and hydroxyacetone, respectively. The quoted errors correspond to 2σ obtained from the least-squares fit analysis and the estimated systematic relative error of 5 %. Finally, these experimental expressions of temperature dependences of P° then permitted the derivation of the enthalpy of vaporization for both compounds.

A microcasted PDMS vacuum pad and its application for stacking thin ceramic layers

A PDMS vacuum pad for stacking very thin green sheets with a 3 µm thick dielectric layer is introduced and fabricated. Its applicability for producing multi-layer ceramic capacitors (MLCCs) is evaluated. Five micro-holes with a diameter and depth of 70 µm are formed on a single vacuum-line unit that is of 120 µm width, 100 µm depth and 2 mm length. Each vacuum-line unit with five micro-holes is deployed at 6 mm intervals on a PDMS vacuum pad of size 166 mm × 166 mm. To fabricate the PDMS vacuum pads, a mold with an obverse structure to that of the PDMS vacuum pad is needed. The metal mold has a two-stage nickel microstructure, the first stage for forming the vacuum lines and the second stage for forming the micro-holes. To fabricate the mold, micromachining processes, including photolithography, nickel/copper electroforming and chemical mechanical polishing, were conducted twice on a precision-machined SUS substrate with a size of 210 mm × 210 mm. The PDMS vacuum pads were fabricated through a microcasting process. Using the PDMS vacuum pad, 320 layers of green sheets, upon which nickel electrodes were patterned on 3 µm thick dielectric layers, were consecutively stacked. It has been observed that the stacked green sheets were very flat and uniform without any distortion or wrinkles. It is believed that the uniform stacking will greatly help to improve the production yield as well as enhance the reliability of MLCCs.