Oil Diffusion Pump Research Articles

Potassium and sodium vapor diffusion pump development for fusion system

An alkali metal diffusion pump, which can meet many requirements for DT fusion system, was developed based on a commercial oil diffusion pump. Using sodium, potassium, and oil each as a vapor source, their evacuation behaviors were compared. The evacuation rate using potassium was comparable to that by original oil, and operation using sodium was found to require higher temperature. The compression ratio and evacuation of deuterium were also investigated. The diffusion pumping system was operated successfully, making this type of evacuation system a potential candidate for the fusion system.

An improved source of spin-polarized electrons based on spin exchange in optically pumped rubidium vapor

We have improved a polarized electron source in which unpolarized electrons undergo collisions with a mixture of buffer gas molecules and optically spin-polarized Rb atoms. With a nitrogen buffer gas, the source reliably provides spin polarization between 15% and 25% with beam currents >4 μA. Vacuum pump upgrades mitigate problems caused by denatured diffusion pump oil, leading to longer run times. A new differential pumping scheme allows the use of higher buffer gas pressures up to 800 mTorr. With a new optics layout, the Rb polarization is continuously monitored by a probe laser and improved pump laser power provides more constant high polarization. We have implemented an einzel lens to better control the energy of the electrons delivered to the target chamber and to preferentially select electron populations of higher polarization. The source is designed for studies of biologically relevant chiral molecule samples, which can poison photoemission-based GaAs polarized electron sources at very low partial pressures. It operates adjacent to a target chamber that rises to pressures as high as 10−4 Torr and has been implemented in a first experiment with chiral cysteine targets.

An in-situ study on surface coloring mechanism of a 12Cr ferrite/martensite stainless steel during vacuum heat treatment

Color changes during oxidation of a 12Cr ferrite/martensite stainless steel were investigated in-situ by using a high vacuum (5 × 10−3 Pa) heating stage where the high vacuum is provided by an oil diffusion pump. The color of the oxide film changed from initial metallic silver to brown, then consecutively to purple, liberty blue, blue-gray and finally to azure blue during the 90 min heat treatment at 690 °C in high vacuum. In contrast to the above changes, during oxidation at 1130 °C, the color changes from metallic silver to brown, then to various blue and finally changed back to metallic silver. The color as a result of thin-film interference mainly depended on the oxide film thickness. The significant reduction of the thickness of the oxide film on the sample vacuum heat-treated at 1130 ℃ is owing to the volatilization of oxide, which is a result of the reaction of the already formed Cr2O3 with residual water vapor and oxygen to generate CrO2(OH)2 and CrO3 gas, which evaporated from the surface at 1130 °C. Ferrite grains have a much lower oxidation kinetics than that of martensite.

Polychlorinated Biphenyl (PCB) in Environment: Contamination, Toxicity, and Carcinogenicity

Polychlorinated Biphenyl (PCB) compounds which are widely used in industry have become a widespread and sustainable environmental problem for decades. PCB is chemically stable, low volatility, non-flammable, and high dielectric constant. Its main uses include heat exchange and dielectric fluids in transformers and capacitors, hydraulic fluids and lubricants, diffusion pump oils, plasticizers for plastics, and so on. PCBs are biologically magnified in the food chain and found in fish, wildlife, and human tissues. PCBs have been identified as contaminants in water, air, and soil, and are distributed up to the polar regions. According to epidemiological studies reporting blood levels of PCBs, the higher the level of exposure, the higher the blood concentration of PCBs, and the higher the environmental concentration or the longer the exposure period (or both), the longer the blood levels of PCBs remain elevated. PCB levels also correlate with race, place of residence (geographical), age, and dietary intake of fish in humans. PCBs have a very low potential to produce acute toxic effects. PCB exposure has been linked to having a particular skin rash commonly referred to as “chloracne”. Liver damage was the most consistent finding among the many laboratory animal species tested. Yusho refers to the epidemic of poisoning by consumption of cooking oil contaminated with PCBs and polychlorinated dibenzofuran. Mothers with Yusho experience stillbirth, abnormal skin pigmentation, or babies tend to be small when compared to the national average. Some PCB compounds are carcinogenic in a number of rodent bioassays, producing liver tumors. Based on the available animal data, PCBs should be considered potential carcinogens for humans. Keywords: Polychlorinated Biphenyl, pollution, contamination, toxicity, carcinogenicity.

Investigation of Chemomechanical Effects on Sapphire Surfaces Modified by Ion-Implantation-Induced Carbon Impurities

Modification of the chemomechanical behaviour of the surface of sapphire by ion implantation to improve its near-surface mechanical properties has been investigated. 300 keV Ti+ ions at various doses were implanted and the concentration and damage profiles characterised using Rutherford Backscattering (RBS). At high doses (≥ 3 × 1016 Ti+ cm−2), a surface amorphous layer is formed due to implantation-induced damage. Nanoindentation was used to determine the hardness behaviour of the ion-implanted layer. Hardness increases at low implantation doses, associated with implantation-induced damage, but it is also observed that chemomechanical softening of the surface is reduced due to the removal of adsorbed water. In situ Raman scattering measurements demonstrate this removal at low doses and the re-establishment of the adsorbed water layer at high doses. The adsorption process is changed due to the introduction of carbon into the sapphire surface during implantation. For the optimum-implanted dose, the water readsorption does not recur even several years after the implantation treatment was first carried out. The loss of water adsorption is related to the formation of a non-polar carbonaceous layer on the sapphire surface by cracking of back-streamed diffusion pump oil deposited on the sample surface by inelastic collisions with the ion beam. Based on this study, it is concluded that ion implantation with an appropriate ion species and dose can control the chemomechanical effect and improve the hardness of ceramics, such as sapphire.

Hydrogel bowls for cleaning oil spills on water

We demonstrate a hydrogel bowl capable of selectively and rapidly collecting spilled oil while floating on water. The bowl has macroscopic openings in its sidewall, and its surface is first coated with octadecyltrichlorosilane (OTS) and then with diffusion pump oil, which imparts exceptional hydrophobic, oleophilic, and high oil wettability properties. The use of a hydrogel makes it possible to obtain surface hydrophobicity and oleophilicity, while also being inexpensive, eco-friendly, and easy to fabricate. Using a prototype of the bowl and a small pump system, we demonstrate that oils with a broad range of viscosities (2.7–2000.0 cSt at 20–40 °C) are more rapidly and efficiently collected from the surface of both pure water and seawater than with any other reported technique. The hydrogel bowl can collect oil for more than one month without losing its efficiency and can be stored in oil for reuse. Therefore, such hydrogel bowls represent a new alternative to conventional oil spill remediation techniques.

Influence of Ingot and Powder Metallurgy Production Route on the Tensile Creep Behavior of Mo–9Si–8B Alloys with Additions of Al and Ge

Refractory metals and their alloys show potential for high temperature applications, due to the elevated melting points often paired with very good creep resistance. Spark plasma sintering (SPS) as well as arc‐melting is used here to prepare quaternary and quinternary Mo–9Si–8B–xAl–yGe (x is 0 or 2; y is 0 or 2, all numbers in at%) samples. All samples consist of a Mo solid solution (Moss) and two intermetallic phases: Mo3Si (A15) and Mo5SiB2 (T2). Aluminum and germanium reduce the melting point and slightly decrease the density of the material. The specimens are homogenized and coarsened by a subsequent heat‐treatment in vacuum at 1850 °C for 24 h. The resulting microstructure is investigated using scanning electron microscope (SEM), energy‐dispersive X‐ray spectroscopy (EDS), X‐ray diffraction (XRD), X‐ray fluorescence spectroscopy (XRF), and inductively coupled plasma optical emission spectrometry (ICP‐OES) analysis. A vacuum creep testing device for small tensile creep specimens is presented. It is heated by graphite radiation heaters usable up to 1500 °C in vacuum of 2 · 10‐4 Pa with an oil diffusion pump. Tensile creep tests are performed at 1250 °C and stresses from 50 MPa up to 250 MPa. Specimens produced by ingot metallurgy feature superior creep properties compared to powder metallurgy samples.

Generation and transportation of high-intensity pulsed ion beam at varying background pressures

AbstractHigh-intensity pulsed ion beam (HIPIB) technology is developed as an advanced manufacturing method for components with improved wear, corrosion and/or fatigue performance, etc. Robust HIPIB equipment with stable repetitive operation, long-lifetime, and easy maintenance are desired for industrial applications, on which stability of ion beam parameters is critical to achieve consistent result of reproducibility. Here, magnetically insulated ion diodes (MIDs) as ion source with durable graphite anode are investigated in a simple self-magnetic field configuration under repetitive operation. Influence of background pressure on ion beam generation and transportation is emphasized since ion beam sources were intrinsically a vacuum-based system. Comparative experiments were conducted on two types of HIPIB equipment, that is, TEMP-6 and TEMP-4M, differing in vacuum packages where turbo-molecular pump or oil diffusion pump was used. Both the HIPIB equipments are operated on a bipolar pulse mode, that is, a first negative pulse of 150–200 kV with pulse duration 450–500 ns to generate anode plasma on explosive electron emission, and a second positive pulse of 200–250 kV with 120 ns to accelerate the ions. Ion beam energy density up to 8 J/cm2 is achievable using MIDs of geometrical focusing configuration, and the total energy, energy density distribution along cross-section, deflection and divergence, and charge neutralization of the ion beams are assessed under background pressures in a wide range of two orders of magnitude, that is, 1–100 mPa. No appreciable change in the parameters is observed up to 50 mPa, and merely a slight increase in the beam deflection from about ±3 mm to about ±4 mm at the focal point over 50 mPa. The stability of ion beam at the varied pressure is mainly facilitated by the higher pressure up to several Pa in anode–cathode gap during plasma generation and good neutralizing effect for ion beam transportation.

Construction of Home-Made Tin Fixed-Point Cell at TUBITAK UME

TUBITAK UME Temperature Laboratory initiated a new study which focuses on the construction of a tin freezing-point cell as a primary temperature standard. The design is an open-cell type similar to the National Institute of Standards and Technology design. With this aim, a brand new vacuum and filling line employing an oil diffusion pump and two cold traps (liquid nitrogen and dry ice) was set-up. The graphite parts (crucible, thermometer well, etc.) have been baked at high temperature under vacuum. Each cell was filled with approximately 1 kg of high-purity tin (99.9999 %) in a three-zone furnace. Then several melting and freezing curves were obtained to assess the quality of the home-made cell, and also the new cell was compared with the existing reference cell of the laboratory. The results obtained are very close to the reference cell of UME, indicating that the method used for fabrication was promising and satisfactory and also seems to meet the requirements to have a primary level temperature standard.

Development of a standard gas generating vial comprised of a silicon oil–polystyrene/divinylbenzene composite sorbent

In this work, a highly reproducible standard gas generating vial is proposed. The vial is comprised of a silicon diffusion pump oil spiked with an appropriate calibration compound, such as modified McReynolds probes (benzene, 2-pentanone, pyridine, 1-nitropropane, 1-pentanol, and n-octane), and then mixed with polystyrene/divinylbenzene (PS/DVB) particles. The concentrations of these compounds in gaseous headspace were found to substantially decrease in comparison to previously developed hydrocarbon pump oil based vials; hence, the amount of standard loaded onto SPME fibers was at most, half that of the previous vial design. Depletion for all compounds after 208 successive extractions was shown to be less than 3.5%. Smaller quantities of standards being used resulted in a vial that depleted slower while remaining statistically repeatable over a wider number of runs. Indeed, it was found that depletion could be largely predicted by using a mass balance theoretical model. This behavior allowed a further increase in the number of loadings that could be performed repeatedly. At a 95% level of confidence, the ANOVA test demonstrated that the prepared vials were statistically identical, with no significant intra- or inter-batch differences. In addition, it was found that vials stored under different conditions (e.g. under light exposure, room temperature, and within a refrigerator) were stable over 10 weeks. Silicon based vials proved to be ideal for performing instrument quality control and loading of internal standards onto fibers, both of which are of great importance when performing on-site analysis using portable GC–MS instrumentation and high throughput determinations in laboratory.

Synthesis and Characterization of Fluorinated Alkyl Substituted Disiloxane

Alkyl substituted disiloxanes demonstrated promising applications as high performance hydraulic oil, diffusion pump oil, etc. In this study, fluorinated alkyl substituted disiloxane was synthesized via Grignard reaction followed by condensation reaction. Its chemical structure was verified by FTIR and NMR. Measurement results showed that this silicon oil exhibited good high temperature performance, oxidation resistance and rust resistance.

Electrical resistivity and its thermal coefficient of TiW alloy thin films prepared by two different sputtering systems

AbstractElectrical resistivity and its thermal coefficient (TCR) of TiW alloy thin films which were prepared by using two different sputtering systems have been investigated. System A is a DC‐magnetron sputtering system equipped with a single composite‐target that allows the contents controllable by an external field of solenoid as reported in previous papers (Sakurai and Takeda, Abstract of E‐MRS 2005 Fall Meeting [1] and Sakurai et al., Solid State Phenom. 154, 175 (2009) [2]). The system A prepared specimens with the range of 21.6 to 36.6 at% of W‐contents. The TCR varies from minus to plus at 32 at% of W‐content. On the other hand, System B is a RF‐magnetron sputtering system equipped with multi‐targets and multi‐sputtering‐sources. The system B covered the whole binary composition ranges by controlling power ratio for two independent sputtering sources. The resistivity characteristics show a parabolic curve with the maximum value on Ti‐rich contents. The TCR decreases at the contents that shows the maximum resistivity, but the TCR is always plus and does not cross zero. Difference of the properties by using the two systems will be discussed. In the system A, the background is exhausted by an oil diffusion pump and the pressure is higher (lower vacuum degree) than the background in the system B with a turbo molecular pump. This suggests that zero TCR would be achieved by introducing the controlled impurities (O2 or N2) into the binary alloy films. (© 2014 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

The Effects of Surface Modification on Spacecraft Charging Parameters

Charging of materials by incident radiation is affected by both environmental and physical conditions. Modifying a material's physical surface will change its reflection, transmission, and absorption of the incident radiation which are integrally related to the accumulation of charge and energy deposition in the material. General arguments for incident and emitted photons, electrons, and ions are considered. An optical analysis of the effects of surface modification on spacecraft charging parameters on prototypical polyimide Kapton HN and Cu samples is presented. Samples were roughened with abrasive compounds ranging from 0.5 to 10 μm in size, comparable to the range of incident wavelengths. They were also contaminated with thin layers of DC 704 diffusion pump oil. Using a UV/VIS/NIR light source and a diffraction grating spectrometer, measurements were performed on pristine and modified materials. The measured spectra confirmed that surface modifications induce expected changes in optical reflection, transmission, and absorption. The generally increased absorption observed results in increased photon energy deposited in the material, leading to increased charge emission through the photoelectric effect.

Tribological properties of nitrogen ion implanted steel

Abstract Nitrogen ions (N + ) with three different doses were implanted on the AISI 304 LN steel samples under high vacuum at room temperature. Dose dependent morphological and structural changes were observed in the specimen. Structural changes were triggered by formation of nitrides; irradiation induced surface segregation of carbon and deposition of amorphous carbon (a-C) by the cracking of hydrocarbons during implantation from oil diffusion pump. Morphological and structural changes were found to influence nano-mechanical and tribological properties of ion implanted surfaces. The nano-indentation hardness was found to increase to 10.26 GPa with highest N + ion dose due to formation of surface nitrides and amorphous carbon. Frictional force was found to decrease with increase in N + ion dose and a minimum value of 0.078 N was obtained at higher dose presumably due to the formation of amorphous graphite like phase. In addition, amorphous diamond like carbon on the implanted surface can be contributing facts for high hardness. At higher dose, both deformation induced damage and wear rate (2.4 × 10 −7 mm 3 /Nm) were found to be minimum.

Virus electron microscopy

Since the introduction of the first electron microscope in 1939, the development of the field of ultra-structure, in both the physical and biological sciences, has been dramatic in its elucidation of problems in both fields. Although the theoretical limit of the resolving power of the instrument 2 o A was achieved early in its development, further refinements followed rapidly. Modern instruments are capable of reaching high vacuum levels in relatively short time periods and computerisation has made these instruments remarkably user friendly. The development of oil diffusion pump technology led to the ability to attain extremely high vacuum levels, an essential feature in allowing a beam of electrons to travel in a focused stream, through the use of condenser, objective and projector lenses striking a fluorescent screen, thus producing an image of the specimen to be examined.

A study on vacuum aspects of electron cyclotron resonance ion source plasma

The electron cyclotron resonance (ECR) ion source is special type hot plasma machine where the high temperature electrons co-exist with multiply charge state ions and neutrals. A few years ago 6.4 GHz. ECR ion source (VEC-ECR) was developed indigenously at VECC. This multiply charged ion source is being used continuously to inject heavy ion beams into the cyclotron. Vacuum plays the major role in ECR ion source. The water cooled plasma chamber is made from an oxygen free high conductivity copper billet to meet the suitable surface condition for vacuum purpose. The entire volume of the ion source is pumped by two 900 1/s special type oil diffusion pumps to achieve 5×10−8 Torr. Usually main plasma chamber is pumped by the plasma itself. Moreover a few 1/s additional pumping speed is provided through extraction hole and pumping slot on the extraction electrode. A study has been carried out to understand the role of vacuum on the multiply charged heavy ion production process. Considering the ion production and loss criteria, it is seen that for getting Ar18+ better vacuum is essential for lower frequency operation. So, an ECR ion source can give better charge state current output operating at higher frequency and stronger confining magnetic field under a specific vacuum condition. The low pressure condition is essential to minimize charge exchange loss due to recombination of multiply charged ions with the neutral atoms. A fixed ratio of neutral to electron density must be maintained for optimizing a particular charge state in the steady state condition. As the electron density is proportional to square of the injected microwave frequency (ne∝f2) a particular operating pressure is essential for a specific charge state. From the study, it has been obtained that the production of Ar18+ ions needs a pressure ∼ 9.6×10−8 Torr for 6.4 GHz. ECR ion source. It is also obtained that an ECR ion source, works at a particular vacuum level, can give better charge state production performance, if it operates at higher frequency and stronger magnetic confinement.

Surface modification of Ti–6Al–4V alloy by nitrogen ion implantation

Surface modification of titanium alloy (Ti–6Al–4V) by nitrogen implantation at the energy 120 keV with doses ranging from 1 × 10 16 to 1 × 10 18 N +/cm 2 have been investigated from the tribological point of view. Implantation of nitrogen ions was performed in two different ways: (a) when no carbon deposition on the samples (produced from the oil diffusion pump and using a liquid nitrogen trap) took place and (b) when carbon atoms were doped into the nitrogen implanted layer (due to recoiling implantation). The depth distribution of the nitrogen implanted atoms was performed by using the RBS technique. The surface characterization of the implanted samples was carried out by means of XRD. It was shown that recoiling implantation reduces significantly the friction coefficient and the wear rates. The maximum decrease in these parameters was pronounced in the nitrogen implanted layer doped with carbon at the dose 1 × 10 18 N +/cm 2. In this case, TiC, or Ti(C, N) layers could be produced. On the other hand, the hardness measurements have shown an improvement at the surface layer of the titanium sample dependent on the nitrogen dose compared with the unimplanted sample.

Reliable and reproducible determination of work function and ionization potentials of layers and surfaces relevant to organic light emitting diodes

Ultra violet photoelectron spectroscopy has been used in most of the research related to determination of the energy levels of the materials in multilayer devices, such as organic light emitting diodes, to measure the Fermi and HOMO levels of conductors and organic materials, respectively. The variation in the values reported in the literature often remains unexplained despite apparently similar experimental conditions. We report (i) on the methods that we have found are required to achieve reproducible and stable values of work function (WF) and ionization potentials (IP) of ITO and common organic layers, and (ii) on the origin of the variations. Not unexpectedly, we have found that hydrocarbon contamination arising from vacuum pumps (e.g. oil diffusion pumps) can cause significant changes in WF or IP. Of greater possible significance is the observation that continuous exposure to ultraviolet light can enhance these effects and can change the work function of an interface much faster than would occur in the absence of UV light. The major effect probably arises from effects of the secondary electrons produced by the 21.22 eV photons of the He resonance lamp. By dealing with these problems, we have been able to measure stable values for WF and IP over extended periods of time ranging from hours to days.

Reliable and reproducible determination of work function and ionization potentials of layers and surfaces relevant to organic light emitting diodes

Ultra violet photoelectron spectroscopy has been used in most of the research related to determination of the energy levels of the materials in multilayer devices, such as organic light emitting diodes, to measure the Fermi and HOMO levels of conductors and organic materials, respectively. The variation in the values reported in the literature often remains unexplained despite apparently similar experimental conditions. We report (i) on the methods that we have found are required to achieve reproducible and stable values of work function (WF) and ionization potentials (IP) of ITO and common organic layers, and (ii) on the origin of the variations. Not unexpectedly, we have found that hydrocarbon contamination arising from vacuum pumps (e.g. oil diffusion pumps) can cause significant changes in WF or IP. Of greater possible significance is the observation that continuous exposure to ultraviolet light can enhance these effects and can change the work function of an interface much faster than would occur in the absence of UV light. The major effect probably arises from effects of the secondary electrons produced by the 21.22 eV photons of the He resonance lamp. By dealing with these problems, we have been able to measure stable values for WF and IP over extended periods of time ranging from hours to days.

ミニマスからマイクロマスヘ

The recent development of the silicon technology effects the stream of the miniaturized mass spectrometry and its system. Trend of oil less also accelerated at the same time. Old oil pump and oil diffusion pump turned to dry pump and turbo molecular pump for example. In the program of Mars exploration and other space program, mass spectrometry is one of the useful techniques to analyze the chemical components of environments. In this paper the recent development of mini size mass spectrometry, which is handy type, and micro mass spectrometry is reviewed. The improvement toward compact size mass has been taken place in the every part of mass spectrometry system from soft ionization system, mass spectrometer to pumping system. Also this improvement wipes out contamination from the overflowed sample and oil system. As the result when higher sensitivity with less sample system overcomes the detection limit of dog nose, new era for mass spectrometer will be created as one of sensors, intelligent nose.