Review of Current Nuclear Vacuum System Technologies

International Nuclear Information System (INIS)

Carroll, M.; McCracken, J.; Shope, T.

2003-01-01

Nearly all industrial operations generate unwanted dust, particulate matter, and/or liquid wastes. Waste dust and particulates can be readily tracked to other work locations, and airborne particulates can be spread through ventilation systems to all locations within a building, and even vented outside the building - a serious concern for processes involving hazardous, radioactive, or nuclear materials. Several varieties of vacuum systems have been proposed and/or are commercially available for clean up of both solid and liquid hazardous and nuclear materials. A review of current technologies highlights both the advantages and disadvantages of the various systems, and demonstrates the need for a system designed to address issues specific to hazardous and nuclear material cleanup. A review of previous and current hazardous/nuclear material cleanup technologies is presented. From simple conventional vacuums modified for use in industrial operations, to systems specifically engineered for such purposes, the advantages and disadvantages are examined in light of the following criteria: minimal worker exposure; minimal secondary waste generation;reduced equipment maintenance and consumable parts; simplicity of design, yet fully compatible with all waste types; and ease of use. The work effort reviews past, existing and proposed technologies in light of such considerations. Accomplishments of selected systems are presented, including identified areas where technological improvements could be suggested

Re-circulating linac vacuum system

International Nuclear Information System (INIS)

Wells, Russell P.; Corlett, John N.; Zholents, Alexander A.

2003-01-01

The vacuum system for a proposed 2.5 GeV, 10ΜA recirculating linac synchrotron light source [1] is readily achievable with conventional vacuum hardware and established fabrication processes. Some of the difficult technical challenges associated with synchrotron light source storage rings are sidestepped by the relatively low beam current and short beam lifetime requirements of a re-circulating linac. This minimal lifetime requirement leads directly to relatively high limits on the background gas pressure through much of the facility. The 10ΜA average beam current produces very little synchrotron radiation induced gas desorption and thus the need for an ante-chamber in the vacuum chamber is eliminated. In the arc bend magnets, and the insertion devices, the vacuum chamber dimensions can be selected to balance the coherent synchrotron radiation and resistive wall wakefield effects, while maintaining the modest limits on the gas pressure and minimal outgassing

Surface currents on the plasma-vacuum interface in MHD equilibria

Science.gov (United States)

Hanson, James

2017-10-01

The VMEC non-axisymmetric MHD equilibrium code can compute free-boundary equilibria. Since VMEC assumes that magnetic fields within the plasma form closed and nested flux surfaces, the plasma-vacuum interface is a flux surface, and the total magnetic field there has no normal component. VMEC imposes this condition of zero normal field using the potential formulation of Merkel, and solves a Neumann problem for the magnetic potential in the exterior region. This boundary condition necessarily admits the possibility of a surface current on the interface. While this surface current may be small in MHD equilibrium, it is readily computed in terms of the magnetic potentials in both the interior and exterior regions, evaluated on the surface. If only the external magnetic potential is known (as in VMEC), then the surface current can be computed from the discontinuity of the tangential field across the interface. Examples of the surface current for VMEC equilibria will be shown for a zero-pressure stellarator equilibrium. Field-line following of the vacuum magnetic field shows magnetic islands within the plasma region.

Vacuum-induced coherence in quantum dot systems

Science.gov (United States)

Sitek, Anna; Machnikowski, Paweł

2012-11-01

We present a theoretical study of vacuum-induced coherence in a pair of vertically stacked semiconductor quantum dots. The process consists in a coherent excitation transfer from a single-exciton state localized in one dot to a delocalized state in which the exciton occupation gets trapped. We study the influence of the factors characteristic of quantum dot systems (as opposed to natural atoms): energy mismatch, coupling between the single-exciton states localized in different dots, and different and nonparallel dipoles due to sub-band mixing, as well as coupling to phonons. We show that the destructive effect of the energy mismatch can be overcome by an appropriate interplay of the dipole moments and coupling between the dots which allows one to observe the trapping effect even in a structure with technologically realistic energy splitting of the order of milli-electron volts. We also analyze the impact of phonon dynamics on the occupation trapping and show that phonon effects are suppressed in a certain range of system parameters. This analysis shows that the vacuum-induced coherence effect and the associated long-living trapped excitonic population can be achieved in quantum dots.

Vacuum chamber eddy current correction coil for the AGS Booster

International Nuclear Information System (INIS)

Danby, G.; Jackson, J.

1988-01-01

The AGS Booster injector will perform a variety of functions. Heavy ion acceleration requires a bakeable, ultra-high vacuum system (VC). Acceleration for intense proton beams requires rapid cycling (B /preceq/ 10T/sec). If straight forward heavy walled VC are used, the field perturbations due to eddy currents are large. The state of the art lattice has highly distributed lumped sextupoles capable of substantially correcting the induced field nonlinearity. Nevertheless, for the very highest space charge-intensity limits, it is desirable to have the capability to remove eddy current fields at the source. Correction coils attached to the outside of the VC cancel its current aberrations over the required good field aperture. These can be passively powered by transformer action, using two turn windings around the magnet yoke. Programmed power supplies can also be used. This inexpensive additional correction option uses a three turn per quadrant coil which follows the local contour of the VC. Transverse movements of several mms of the VC will have no beam optical effect since the large field aberrations and their corrections have the same displaced coordinates. Experimental and computer studies will be presented, as well as mechanical and electrical design of a simple method of construction. 6 figs

Vacuum chamber eddy current correction coil for the AGS booster

International Nuclear Information System (INIS)

Danby, G.; Jackson, J.

1988-01-01

This paper reports on the AGS Booster injector that performs a variety of functions. Heavy ion acceleration requires a bakeable, ultra-high vacuum system (VC). Acceleration for intense proton beams requires rapid cycling (B ≤10T/sec). If straight forward heavy walled VC are used, the field perturbations due to eddy currents are large. The state of the art lattice has highly distributed lumped sextupoles capable of substantially correcting the induced field nonlinearity. Nevertheless, for the very highest space charge-intensity limits, it is desirable to have the capability to remove eddy current fields at the source. Correction coils attached to the outside of the VC cancel its current aberrations over the required good field aperture. These can be passively powered by transformer action, using two turn windings around the magnet yoke. Programmed power supplies can also be used. This inexpensive additional correction option uses a three turn per quadrant coil which follows the local contour of the VC. Transverse movements of several mms of the VC will have no beam optical effect since the large field aberrations and their corrections have the same displace coordinates. Experimental and computer studies will be presented, as well as mechanical and electrical design of a simple method of construction

High current vacuum arc ion source for heavy ion fusion

International Nuclear Information System (INIS)

Qi, N.; Schein, J.; Gensler, S.; Prasad, R.R.; Krishnan, M.; Brown, I.

1999-01-01

Heavy Ion fusion (HIF) is one of the approaches for the controlled thermonuclear power production. A source of heavy ions with charge states 1+ to 2+, in ∼0.5 A current beams with ∼20 micros pulse widths and ∼10 Hz repetition rates are required. Thermionic sources have been the workhorse for the HIF program to date, but suffer from sloe turn-on, heating problems for large areas, are limited to low (contact) ionization potential elements and offer relatively low ion fluxes with a charge state limited to 1+. Gas injection sources suffer from partial ionization and deleterious neutral gas effects. The above shortcomings of the thermionic ion sources can be overcome by a vacuum arc ion source. The vacuum arc ion source is a good candidate for HIF applications. It is capable of providing ions of various elements and different charge states, in short and long pulse bursts, with low emittance and high beam currents. Under a Phase-I STTR from DOE, the feasibility of the vacuum arc ion source for the HIF applications is investigated. An existing ion source at LBNL was modified to produce ∼0.5 A, ∼60 keV Gd (A∼158) ion beams. The experimental effort concentrated on beam noise reduction, pulse-to-pulse reproducibility and achieving low beam emittance at 0.5 A ion current level. Details of the source development will be reported

Radiation induced ion currents in vacuum due to residual He and H, and their expected effect on insulating surfaces

International Nuclear Information System (INIS)

Hodgson, E.R.; Morono, A.; Gonzalez de Vicente, S.M.

2006-01-01

Ceramic insulators and windows in ITER will be subjected to bombardment by energetic hydrogen isotopes and helium as a consequence of ionization of the residual gas by gamma radiation and acceleration of the ions by the local electric fields. Most of the energy carried by these particles will be deposited at or very near the surface giving rise to possible electrical and optical degradation. Severe surface electrical degradation has recently been observed when oxide materials are implanted to low doses (10 15 ions/cm 2 ) with protons and alpha particles at temperatures between 50 and 450 o C. In order to estimate the relevance to fusion applications and hence the lifetime of ceramic insulators in ITER it is necessary to quantify possible ion currents generated in the residual gas by measuring radiation induced electrical conductivity for hydrogen isotopes and helium gases at low pressures and then perform experiments in which ceramic candidate materials are subjected to ion bombardment at representative currents and energies. To determine the magnitude of radiation generated ion currents, experiments have been carried out in a special gas chamber mounted in the beam line of a 2 MeV Van de Graaff electron accelerator, with the gases being irradiated through an 0.05 x 10 -3 m thick aluminium window with 1.8 MeV electrons. A guarded volume was defined between two parallel square copper plate electrodes separated by 1.5 x 10 -2 m. The experimental set-up permitted an electric field to be applied to the irradiated volume of gas, and the electric current flowing through the ionized gas to be measured. For these experiments the radiation beam was perpendicular to the electric field direction. In this way radiation induced conductivity for helium and hydrogen has been measured at pressures between about 1000 and 10 -3 mbar (10 -5 to 10 -1 Pa), radiation dose rates of 30 Gy/s and applied voltages up to 1500 volts. The radiation induced electrical currents for low pressure

A high current metal vapour vacuum arc ion source for ion implantation studies

International Nuclear Information System (INIS)

Evans, P.J.; Noorman, J.T.; Watt, G.C.; Cohen, D.D.; Bailey, G.M.

1989-01-01

The main features of the metal vapour vacuum arc(MEVA) as an ion source are presented. The technology utilizes the plasma production capabilities of a vacuum arc cathode. Some of the ions produced in this discharge flow through the anode and the 3 extraction grids to form an extracted ion beam. The high beam current and the potential for generating broad beams, make this technology suitable for implantation of large surface areas. The composition of the vacuum arc cathode determines the particular ions obtained from the MEVA source. 3 refs., 1 tab., 2 figs

Vacuum surface flashover and high pressure gas streamers

International Nuclear Information System (INIS)

Elizondo, J.M.; Krogh, M.L.; Smith, D.; Stolz, D.; Wright, S.N.

1997-07-01

Pre-breakdown current traces obtained during high pressure gas breakdown and vacuum surface flashover show similar signatures. The initial pre-breakdown current spike, a flat constant current phase, and the breakdown phase with voltage collapse and current surge differ mostly in magnitude. Given these similarities, a model, consisting of the initial current spike corresponding to a fast precursor streamer (ionization wave led by a photoionizing front), the flat current stage as the heating or glow phase, and the terminal avalanche and gap closure, is applied to vacuum surface flashover. A simple analytical approximation based on the resistivity changes induced in the vacuum and dielectric surface is presented. The approximation yields an excellent fit to pre-breakdown time delay vs applied field for previously published experimental data. A detailed kinetics model that includes surface and gas contributions is being developed based in the initial approximation

Impact of mechanical stress induced in silica vacuum windows on laser-induced damage.

Science.gov (United States)

Gingreau, Clémence; Lanternier, Thomas; Lamaignère, Laurent; Donval, Thierry; Courchinoux, Roger; Leymarie, Christophe; Néauport, Jérôme

2018-04-15

At the interface between vacuum and air, optical windows must keep their optical properties, despite being subjected to mechanical stress. In this Letter, we investigate the impact of such stress on the laser-induced damage of fused silica windows at the wavelength of 351 nm in the nanosecond regime. Different stress values, from 1 to 30 MPa, both tensile and compressive, were applied. No effect of the stress on the laser-induced damage was evidenced.

Vacuum circuit breaker postarc current modelling based on the theory of Langmuir probes

NARCIS (Netherlands)

Lanen, van E.P.A.; Smeets, R.; Popov, M.; Sluis, van der L.

2007-01-01

High-resolution measurements on the postarc current in vacuum circuit breakers (VCBs) reveal a period, immediately following current-zero, in which the voltage remains practically zero. The most widely used model for simulating the interaction between the postarc current with the electrical circuit

Vacuum transitions in dual models

International Nuclear Information System (INIS)

Pashnev, A.I.; Volkov, D.V.; Zheltukhin, A.A.

1976-01-01

The investigation is continued of the spontaneous vacuum transition problem in the Neview-Schwartz dual model (NSDM). It is shown that vacuum transitions allow disclosing of supplementary degeneration in the resonance state spectrum. The dual amplitudes possess an internal structure corresponding to the presence of an infinite number of quarks with increasing masses and retained charges. The Adler principle holds. Analytic continuation on the constant of induced vacuum transitions makes it possible to establish the existence of spontaneous vacuum transitions in the NSDM. The consequence of this fact is the exact SU(2) symmetry of π, rho meson trajectories and the Higgs mechanism in the model. In this case the ratios of masses of particles leading trajectories are analogous to those obtained in the current algebra. It is shown that in the NSDM there arises chiral SU(2) x SU(2) x U(1) x U(1) x ... symmetry resulting from spontaneous vacuum transitions

High Charge State Ions Extracted from Metal Plasmas in the Transition Regime from Vacuum Spark to High Current Vacuum Arc

International Nuclear Information System (INIS)

Yushkov, Georgy Yu.; Anders, A.

2008-01-01

Metal ions were extracted from pulsed discharge plasmas operating in the transition region between vacuum spark (transient high voltage of kV) and vacuum arc (arc voltage ∼ 20 V). At a peak current of about 4 kA, and with a pulse duration of 8 (micro)s, we observed mean ion charges states of about 6 for several cathode materials. In the case of platinum, the highest average charge state was 6.74 with ions of charge states as high as 10 present. For gold we found traces of charge state 11, with the highest average charge state of 7.25. At currents higher than 5 kA, non-metallic contaminations started to dominate the ion beam, preventing further enhancement of the metal charge states

Cathode-constriction and column-constriction in high current vacuum arcs subjected to an axial magnetic field

Science.gov (United States)

Zhang, Zaiqin; Ma, Hui; Liu, Zhiyuan; Geng, Yingsan; Wang, Jianhua

2018-04-01

The influence of the applied axial magnetic field on the current density distribution in the arc column and electrodes is intensively studied. However, the previous results only provide a qualitative explanation, which cannot quantitatively explain a recent experimental data on anode current density. The objective of this paper is to quantitatively determine the current constriction subjected to an axial magnetic field in high-current vacuum arcs according to the recent experimental data. A magnetohydrodynamic model is adopted to describe the high current vacuum arcs. The vacuum arc is in a diffuse arc mode with an arc current ranged from 6 kArms to 14 kArms and an axial magnetic field ranged from 20 mT to 110 mT. By a comparison of the recent experimental work of current density distribution on the anode, the modelling results show that there are two types of current constriction. On one hand, the current on the cathode shows a constriction, and this constriction is termed as the cathode-constriction. On the other hand, the current constricts in the arc column region, and this constriction is termed as the column-constriction. The cathode boundary is of vital importance in a quantitative model. An improved cathode constriction boundary is proposed. Under the improved boundary, the simulation results are in good agreement with the recent experimental data on the anode current density distribution. It is demonstrated that the current density distribution at the anode is sensitive to that at the cathode, so that measurements of the anode current density can be used, in combination with the vacuum arc model, to infer the cathode current density distribution.

Analysis of an innovative solar water desalination system using gravity induced vacuum

International Nuclear Information System (INIS)

Ayhan, T.; Al-Madani, H.

2007-01-01

This study presents the theoretical analysis, design and appropriate models of a new desalination system using gravity induced vacuum. The system utilizes natural means (gravity and atmospheric pressure) to create a vacuum under which water can be rapidly evaporated at much lower temperatures with less energy than conventional techniques. This technique is developed to overcome water storage, in the areas where good solar radiation (or waste heat sources) and sea water (or waste water sources). The developed system consists of an evaporator connected to condenser by means of a vacuum tank. The vapour produced in the evaporator is driven to condenser through the vacuum tank, where it condenses and collected as a product. Vacuum equivalent to 7 kPa (abs) or less can be created depending on ambient temperature of Bahrain climatic conditions. The effect of various operating conditions, namely water levels in condensation and evaporating columns on the system performance were studied. The theoretical analysis and preliminary experimental results show that the performance of this system depends on the condensation temperature

Recent advances in high current vacuum arc ion sources for heavy ion fusion

CERN Document Server

Qi Nian Sheng; Prasad, R R; Krishnan, M S; Anders, A; Kwan, J; Brown, I

2001-01-01

For a heavy ion fusion induction linac driver, a source of heavy ions with charge states 1+-3+, approx 0.5 A current beams, approx 20 mu s pulse widths and approx 10 Hz repetition rates is required. Thermionic sources have been the workhorse for the Heavy Ion Fusion (HIF) program to date, but suffer from heating problems for large areas and contamination. They are limited to low (contact) ionization potential elements and offer relatively low ion fluxes with a charge state limited to 1+. Gas injection sources suffer from partial ionization and deleterious neutral gas effects. The above shortcomings of the thermionic ion sources can be overcome by a vacuum arc ion source. The vacuum arc ion source is a good candidate for HIF applications. It is capable of providing ions of various elements and different charge states in short and long pulse bursts and high beam current density. Under a Phase-I STTR from DOE, the feasibility of the vacuum arc ion source for the HIF applications was investigated. We have modifie...

High ion charge states in a high-current, short-pulse, vacuum ARC ion sources

International Nuclear Information System (INIS)

Anders, A.; Brown, I.; MacGill, R.; Dickinson, M.

1996-01-01

Ions of the cathode material are formed at vacuum arc cathode spots and extracted by a grid system. The ion charge states (typically 1-4) depend on the cathode material and only little on the discharge current as long as the current is low. Here the authors report on experiments with short pulses (several μs) and high currents (several kA); this regime of operation is thus approaching a more vacuum spark-like regime. Mean ion charge states of up to 6.2 for tungsten and 3.7 for titanium have been measured, with the corresponding maximum charge states of up to 8+ and 6+, respectively. The results are discussed in terms of Saha calculations and freezing of the charge state distribution

High ion charge states in a high-current, short-pulse, vacuum arc ion source

International Nuclear Information System (INIS)

Anders, A.; Brown, I.; MacGill, R.; Dickinson, M.

1995-09-01

Ions of the cathode material are formed at vacuum arc cathode spots and extracted by a grid system. The ion charge states (typically 1--4) depend on the cathode material and only little on the discharge current as long as the current is low. Here the authors report on experiments with short pulses (several micros) and high currents (several kA); this regime of operation is thus approaching a more vacuum spark-like regime. Mean ion charge states of up to 6.2 for tungsten and 3.7 for titanium have been measured, with the corresponding maximum charge states of up to 8+ and 6+, respectively. The results are discussed in terms of Saha calculations and freezing of the charge state distribution

Effects of vacuum ultraviolet irradiation on trapped charges and leakage currents of low-k organosilicate dielectrics

Energy Technology Data Exchange (ETDEWEB)

Zheng, H.; Guo, X.; Pei, D.; Shohet, J. L. [Plasma Processing and Technology Laboratory and Department of Electrical and Computer Engineering, University of Wisconsin-Madison, Madison, Wisconsin 53706 (United States); Ryan, E. T. [GLOBALFOUNDRIES, Albany, New York 12203 (United States); Nishi, Y. [Stanford University, Stanford, California 94305 (United States)

2015-05-11

Vacuum ultraviolet (VUV) photoemission spectroscopy is utilized to investigate the distribution of trapped charges within the bandgap of low dielectric constant (low-k) organosilicate (SiCOH) materials. It was found that trapped charges are continuously distributed within the bandgap of porous SiCOH and the center of the trapped states is 1.3 eV above the valence band of the tested sample. By comparing photoemission spectroscopic results before and after VUV exposure, VUV irradiation with photon energies between 7.6 and 8.9 eV was found to deplete trapped charge while UV exposure with photon energies less than 6.0 eV induces more trapped charges in tested samples. Current-Voltage (IV) characteristics results show that the reliability of dielectrics is improved after VUV irradiation with photon energies between 7.6 and 8.9 eV, while UV exposure results in an increased level of leakage current and a decreased breakdown voltage, both of which are harmful to the reliability of the dielectric. This work shows that VUV irradiation holds the potential to substitute for UV curing in microelectronic processing to improve the reliability of low-k dielectrics by mitigating the leakage currents and trapped charges induced by UV irradiation.

Reconstruction of vacuum magnetic flux in QUEST

International Nuclear Information System (INIS)

Ishiguro, Masaki; Hanada, Kazuaki; Nakamura, Kazuo

2010-01-01

It is important to determine the best method for reconstructing the magnetic flux when eddy currents are significantly induced during magnetic measurement in spherical tokamaks (STs). Four methods for this reconstruction are investigated, and the calculated magnetic fluxes are compared to those measured in the cavity of a vacuum vessel. The results show that the best method is the one that uses currents from virtual coils for reconstruction. In this method, the placement of the virtual coils is optimized with numerical simulations using the Akaike information criterion (AIC), which indicates the goodness of fit of models used to fit measured data. The virtual coils are set on a line 15 cm outside the vacuum vessel. (author)

Molecular density modulation type ultrahigh vacuum gauge

International Nuclear Information System (INIS)

Horikoshi, Gen-ichi; Komada, Kazutaka; Mizuno, Hajime

1978-01-01

When pressure is measured in ultrahigh vacuum region, with an ionization gauge one of the causes producing the measuring limit is its dark current due to so-called soft X-ray effect and ion desorption. A kind of the modulation gauge provided with a modulation electrode is described in this paper. If a plate is vibrating perpendicularly to its surface in the sufficiently low pressure gas to satisfy molecular conditions (molecular density n), the molecular density in the space in front of the plate is expected to vary with time, affected by the vibration of the plate. When the vacuum gauge is placed in this space, the modulated current is proportional to pressure P, which is not related to the current due to soft X-ray effect and ion desorption. The other cause of determining the pressure-measuring limit is noises, among which only the noise coherent with the vibration of the plate affects the measurement. To avoid the induced current by this type of noise, it is considered to use the pulse-counting technique using an electron multiplier. It is anticipated that the induced currents generated from electrical noises and mechanical vibrations can be avoided almost completely by this method. As a result, the theoretical measuring limit may be estimated at approximately 5 x 10 -13 Torr, if the mean residence time in the collision of molecules with the plate is assumed to be 1 sec, the sensitivity of the vacuum gauge S is 20 Torr -1 , electron current Ie is 2 x 10 -3 A and modulation coefficient m is 3 x 10 -3 . (Wakatsuki, Y.)

Vacuum interrupters used for the interruption of high dc currents

International Nuclear Information System (INIS)

Warren, R.W.

1977-01-01

Conventional ac vacuum interrupters are being used to interrupt currents in pulsed energy storage systems. They have been tested with dc currents of up to 37 kA. The limit to the current which can be successfully interrupted has been measured as a function of various parameters. Among these are (1) the size of the interrupter, (2) the magnitude of the counterpulse current, (3) the nature and flux rating of the saturable reactor used, and (4) the kind of ''snubber'' circuit used. Fragmentary data have also been collected on electrode erosion rates and on mechanical failure of the bellows. A description is given of the circuits used in these tests and of the results found for a representative selection of the commercially available domestic interrupters. More recently efforts have been made to increase the values found for the maximum interruptible current. The techniques used have included connecting interrupters in parallel and operating them in an impressed axial magnetic field. The results of this work are discussed

High current density M-type cathodes for vacuum electron devices

International Nuclear Information System (INIS)

Li Ji; Yu Zhiqiang; Shao Wensheng; Zhang Ke; Gao Yujuan; Yuan Haiqing; Wang Hui; Huang Kaizhi; Chen Qilue; Yan Suqiu; Cai Shaolun

2005-01-01

We investigated high current density emission capabilities of M-type cathodes used for vacuum electron devices (VEDs). The experimental results of emission and lifetime evaluating in both close-spaced diode structure and electron gun testing vehicles are given. Emission current densities measured in the diode structure at 1020 deg. C Br in the CW mode were above 10 A/cm 2 ; while in electron gun testing vehicles, emission current densities were above 8 A/cm 2 in CW mode and above 32 A/cm 2 in pulsed mode, respectively. The current density above 94 A/cm 2 has been acquired in no. 0306 electron gun vehicle while the practical temperature is 1060 deg. C Br . For a comparison some of the data from I-scandate cathodes are presented. Finally, several application examples in practical travelling wave tubes (TWTs) and multi beam klystrons (MBKs) are also reported

Eddy Current Effect of the BNL-AGS Vacuum Chamber on the Optics of the BNL-AGS Synchrotron

International Nuclear Information System (INIS)

Tsoupas, N.; Ahrens, L.; Brown, K. A.; Glenn, J. W.; Gardner, K.

1999-01-01

During the acceleration cycle of the AGS synchrotron, eddy currents are generated within the walls of the vacuum chambers of the AGS main magnets. The vacuum chambers have elliptical cross section, are made of inconel material with a wall thickness of 2 mm and are placed within the gap of the combined-function main magnets of the AGS synchrotron. The generation of eddy currents in the walls of the vacuum chambers, creates various magnetic multipoles, which affect the optics of the AGS machine. In this report these magnetic multipoles are calculated for various time interval starting at the acceleration cycle, where the magnetic field of the main magnet is ∼0.1 T, and ending before the beam extraction process, where the magnetic field of the main magnet is almost constant at ∼ 1.1 T. The calculations show that the magnetic multipoles generated by the eddy-currents affect the optics of the AGS synchrotron during the acceleration cycle and in particular at low magnetic fields of the main magnet. Their effect is too weak to affect the optics of the AGS machine during beam extraction at the nominal energies

Vacuum Chamber for the Booster Bending Magnets

CERN Multimedia

CERN PhotoLab

1974-01-01

To minimize eddy currents, induced by the rising magnetic field, the chamber was made from thin stainless steel of high specific electric resistance. For mechanical stength, it was corrugated in a hydro-forming process. The chamber is curved, to follow the beam's orbital path. Under vacuum, the chamber tends to staighten, the ceramic spacer along half of its length keeps it in place (see also 7402458).

Vacuum energy induced by an external magnetic field in a curved space

International Nuclear Information System (INIS)

Sitenko, Yu.A.; Rakityansky, D.G.

1998-01-01

The asymptotic expansion of the product of an operator raised to an arbitrary power and an exponential function of this operator is obtained. With the aid of this expansion, the density of vacuum energy induced by a static external magnetic field of an Abelian or a non-Abelian nature is expressed in terms of the DeWitt-Seeley-Gilkey coefficients

Radiation cleanup of vacuum systems (radiation-induced outgassing). Progress report, September 15, 1976--September 14, 1977

International Nuclear Information System (INIS)

Anno, J.N.

1977-06-01

A stainless steel-304 vacuum system has been designed and constructed to study radiation-induced outgassing when this material is exposed to cobalt-60 gamma radiation. The system is pumped with an ion pump and sorption roughing pump. No foreign materials have been introduced except for copper seals at the flanges. An analytical model has been developed which predicts the outgassing from SS-304 to be 8.27 x 10 -12 torr-liters/(cm 2 )(sec) per megarad/hr. Extrapolation of existing data for aluminum suggests a lower value of 1.0 x 10 -12 torr-liters/(cm 2 )(sec) per megarad/hr. Experiments to determine the value are currently in progress

Preliminary test of vacuum system of SPring-8 synchrotron

International Nuclear Information System (INIS)

Otsuka, Hideo; Yoneyama, Katsuji; Shimada, Taihei

1992-01-01

In this report, on the several points which it is desirable to be confirmed beforehand when the vacuum system of the synchrotron is designed, the results of the test by making the vacuum system for one normal cell simulating the actual machine are reported. Further by making three types of sample ducts, the ordinary type of 1.65 mm thickness, the rib-reinforced type of 0.3 mm thickness and bellows structure, the rate of released gas and the effect to eddy current were examined, for the purpose of taking the countermeasures to the eddy current accompanying the synchrotron operation. The mockup of the normal cell was composed of a duct of 10 m length, two ion pumps of 20 l/s, and a turbo molecular pump of 50 l/s, and the material of the ducts is SUS316L, and the sectional form is elliptic of 72 x 34. In the vacuum test of the normal cell, the exhaust characteristics at the time of rise and pressure distribution were verified. The measurement of the rate of released gas in the ducts and the measurement of current and voltage induced in the ducts are reported. The sufficient performance can be expected with the exhaust system used, and the time required for the rise of the vacuum system was clarified. (K.I.)

Comparison of direct and alternating current vacuum ultraviolet lamps in atmospheric pressure photoionization.

Science.gov (United States)

Vaikkinen, Anu; Haapala, Markus; Kersten, Hendrik; Benter, Thorsten; Kostiainen, Risto; Kauppila, Tiina J

2012-02-07

A direct current induced vacuum ultraviolet (dc-VUV) krypton discharge lamp and an alternating current, radio frequency (rf) induced VUV lamp that are essentially similar to lamps in commercial atmospheric pressure photoionization (APPI) ion sources were compared. The emission distributions along the diameter of the lamp exit window were measured, and they showed that the beam of the rf lamp is much wider than that of the dc lamp. Thus, the rf lamp has larger efficient ionization area, and it also emits more photons than the dc lamp. The ionization efficiencies of the lamps were compared using identical spray geometries with both lamps in microchip APPI mass spectrometry (μAPPI-MS) and desorption atmospheric pressure photoionization-mass spectrometry (DAPPI-MS). A comprehensive view on the ionization was gained by studying six different μAPPI solvent compositions, five DAPPI spray solvents, and completely solvent-free DAPPI. The observed reactant ions for each solvent composition were very similar with both lamps except for toluene, which showed a higher amount of solvent originating oxidation products with the rf lamp than with the dc lamp in μAPPI. Moreover, the same analyte ions were detected with both lamps, and thus, the ionization mechanisms with both lamps are similar. The rf lamp showed a higher ionization efficiency than the dc lamp in all experiments. The difference between the lamp ionization efficiencies was greatest when high ionization energy (IE) solvent compositions (IEs above 10 eV), i.e., hexane, methanol, and methanol/water, (1:1 v:v) were used. The higher ionization efficiency of the rf lamp is likely due to the larger area of high intensity light emission, and the resulting larger efficient ionization area and higher amount of photons emitted. These result in higher solvent reactant ion production, which in turn enables more efficient analyte ion production. © 2012 American Chemical Society

Laser induced damage and fracture in fused silica vacuum windows

International Nuclear Information System (INIS)

Campbell, J.H.; Hurst, P.A.; Heggins, D.D.; Steele, W.A.; Bumpas, S.E.

1996-11-01

Laser-induced damage, that initiates catastrophic fracture, has been observed in large (≤61 cm dia) fused silica lenses that also serve as vacuum barriers in Nova and Beamlet lasers. If the elastic stored energy in the lens is high enough, the lens will fracture into many pieces (implosion). Three parameters control the degree of fracture in the vacuum barrier window: elastic stored energy (tensile stress), ratio of window thickness to flaw depth, and secondary crack propagation. Fracture experiments were conducted on 15-cm dia fused silica windows that contain surface flaws caused by laser damage. Results, combined with window failure data on Beamlet and Nova, were used to develop design criteria for a ''fail-safe'' lens (that may catastrophically fracture but not implode). Specifically, the window must be made thick enough so that the peak tensile stress is less than 500 psi (3.4 MPa) and the thickness/critical flaw size is less than 6. The air leak through the window fracture and into the vacuum must be rapid enough to reduce the load on the window before secondary crack growth occurs. Finite element stress calculations of a window before and immediately following fracture into two pieces show that the elastic stored energy is redistributed if the fragments ''lock'' in place and thereby bridge the opening. In such cases, the peak stresses at the flaw site can increase, leading to further (i.e. secondary) crack growth

Vacuum treatment of CR-39 for the reduction of background in neutron induced autoradiography of boron

International Nuclear Information System (INIS)

Freyer, K.; Treutler, H.C.; Dietze, K.; Hunyadi, I.; Csige, I.; Somogyi, G.

1991-01-01

The influence of etching time and vacuum processing before, during, and after neutron irradiation on the ''signal/noise'' ratio of the neutron induced autoradiography of boron using CR-39 track detectors has been investigated. The neutron irradiation was carried out in a vacuum chamber using the Cf-252 neutron source of the Central Institute of Isotope and Radiation Research at Leipzig. Hungarian-made CR-39 type track detectors, MA-ND/p and MA-ND/α, produced in different years, are compared. After a few hours of 2 kPa (about 10 -2 Torr) vacuum treatment, the ''signal/noise'' ratio for boron determination is improved remarkably in most cases of the detector and etching-time combinations used. (author)

Vacuum Technology

Energy Technology Data Exchange (ETDEWEB)

Biltoft, P J

2004-10-15

The environmental condition called vacuum is created any time the pressure of a gas is reduced compared to atmospheric pressure. On earth we typically create a vacuum by connecting a pump capable of moving gas to a relatively leak free vessel. Through operation of the gas pump the number of gas molecules per unit volume is decreased within the vessel. As soon as one creates a vacuum natural forces (in this case entropy) work to restore equilibrium pressure; the practical effect of this is that gas molecules attempt to enter the evacuated space by any means possible. It is useful to think of vacuum in terms of a gas at a pressure below atmospheric pressure. In even the best vacuum vessels ever created there are approximately 3,500,000 molecules of gas per cubic meter of volume remaining inside the vessel. The lowest pressure environment known is in interstellar space where there are approximately four molecules of gas per cubic meter. Researchers are currently developing vacuum technology components (pumps, gauges, valves, etc.) using micro electro mechanical systems (MEMS) technology. Miniature vacuum components and systems will open the possibility for significant savings in energy cost and will open the doors to advances in electronics, manufacturing and semiconductor fabrication. In conclusion, an understanding of the basic principles of vacuum technology as presented in this summary is essential for the successful execution of all projects that involve vacuum technology. Using the principles described above, a practitioner of vacuum technology can design a vacuum system that will achieve the project requirements.

A high-current pulsed cathodic vacuum arc plasma source

International Nuclear Information System (INIS)

Oates, T.W.H.; Pigott, J.; Mckenzie, D.R.; Bilek, M.M.M.

2003-01-01

Cathodic vacuum arcs (CVAs) are well established as a method for producing metal plasmas for thin film deposition and as a source of metal ions. Fundamental differences exist between direct current (dc) and pulsed CVAs. We present here results of our investigations into the design and construction of a high-current center-triggered pulsed CVA. Power supply design based on electrolytic capacitors is discussed and optimized based on obtaining the most effective utilization of the cathode material. Anode configuration is also discussed with respect to the optimization of the electron collection capability. Type I and II cathode spots are observed and discussed with respect to cathode surface contamination. An unfiltered deposition rate of 1.7 nm per pulse, at a distance of 100 mm from the source, has been demonstrated. Instantaneous plasma densities in excess of 1x10 19 m -3 are observed after magnetic filtering. Time averaged densities an order of magnitude greater than common dc arc densities have been demonstrated, limited by pulse repetition rate and filter efficiency

X-ray induced gas desorption within a prototype LEP vacuum chamber

International Nuclear Information System (INIS)

Williams, E.M.; Le Normand, F.; Hilleret, N.; Dominichini, G.

1982-12-01

The present report is concerned with an experimental simulation of the process of photon induced desorption within an aluminium vacuum chamber of the same basic form as proposed for the LEP accelerator. The objectives in the work can be described in the following three-fold manner: Firstly, to establish the levels of photon induced desorption efficiency for identified gas species. Secondly, to examine the contribution of surface treatments as bakeout and glow discharge cleaning, and to correlate these responses with changes in surface activity induced by beam cleaning. Thirdly, to gain insight into the energy dependence of the desorption process so as to provide a reasonable basis for predicting conditions at the levels of critical energy in excess of 100 keV which are applicable at the full design energy of the LEP accelerator. (orig./HSI)

Vacuum treatment of CR-39 for the reduction of background in neutron induced autoradiography of boron

Energy Technology Data Exchange (ETDEWEB)

Freyer, K.; Treutler, H.C.; Dietze, K. (Central Inst. of Isotope and Radiation Research, Leipzig (Germany, F.R.)); Hunyadi, I.; Csige, I.; Somogyi, G. (Magyar Tudomanyos Akademia, Debrecen (Hungary). Atommag Kutato Intezete)

1991-01-01

The influence of etching time and vacuum processing before, during, and after neutron irradiation on the ''signal/noise'' ratio of the neutron induced autoradiography of boron using CR-39 track detectors has been investigated. The neutron irradiation was carried out in a vacuum chamber using the Cf-252 neutron source of the Central Institute of Isotope and Radiation Research at Leipzig. Hungarian-made CR-39 type track detectors, MA-ND/p and MA-ND/{alpha}, produced in different years, are compared. After a few hours of 2 kPa (about 10{sup -2} Torr) vacuum treatment, the ''signal/noise'' ratio for boron determination is improved remarkably in most cases of the detector and etching-time combinations used. (author).

Interpretation of secondary electron images obtained using a low vacuum SEM

International Nuclear Information System (INIS)

Toth, M.; Thiel, B.L.; Donald, A.M.

2003-01-01

Charging of insulators in a variable pressure environment was investigated in the context of secondary electron (SE) image formation. Sample charging and ionized gas molecules present in a low vacuum specimen chamber can give rise to SE image contrast. 'Charge-induced' SE contrast reflects lateral variations in the charge state of a sample caused by electron irradiation during and prior to image acquisition. This contrast corresponds to SE emission current alterations produced by sub-surface charge deposited by the electron beam. 'Ion-induced' contrast results from spatial inhomogeneities in the extent of SE signal inhibition caused by ions in the gaseous environment of a low vacuum scanning electron microscope (SEM). The inhomogeneities are caused by ion focusing onto regions of a sample that correspond to local minima in the magnitude of the surface potential (generated by sub-surface trapped charge), or topographic asperities. The two types of contrast exhibit characteristic dependencies on microscope operating parameters such as scan speed, beam current, gas pressure, detector bias and working distance. These dependencies, explained in terms of the behavior of the gaseous environment and sample charging, can serve as a basis for a correct interpretation of SE images obtained using a low vacuum SEM

Vacuum vessel for thermonuclear device

International Nuclear Information System (INIS)

Hagiwara, Koji; Imura, Yasuya.

1979-01-01

Purpose: To provide constituted method for easily performing baking of vacuum vessel, using short-circuiting segments. Constitution: At the time of baking, one turn circuit is formed by the vacuum vessel and short-circuiting segments, and current transformer converting the one turn circuit into a secondary circuit by the primary coil and iron core is formed, and the vacuum vessel is Joule heated by an induction current from the primary coil. After completion of baking, the short-circuiting segments are removed. (Kamimura, M.)

Enzymatic quantification of strand breaks of DNA induced by vacuum-UV radiation

International Nuclear Information System (INIS)

Ito, Takashi

1986-01-01

Hind3 digested plasmid DNA dried on an aluminum plate was irradiated by vacuum-UV at 160 and 195 nm using a synchrotron irradiation system. A change induced in the DNA, presumably a single strand break, was quantified by the aid of the strand break-derived stimulation of poly(ADP-ribose) synthetase activity. The end group of strand breaks so induced was recognized by the enzyme as effectively as that by DNase 1 treatment, suggesting a nicking as the major lesion inflicted on the DNA. The fluence (UV) dependent stimulation of poly(ADP-ribose) synthetase activity was much higher upon 160 nm irradiation than upon 195 nm irradiation. (Auth.)

Vacuum radiation induced by time dependent electric field

Directory of Open Access Journals (Sweden)

Bo Zhang

2017-04-01

Full Text Available Many predictions of new phenomena given by strong field quantum electrodynamics (SFQED will be tested on next generation multi-petawatt laser facilities in the near future. These new phenomena are basis to understand physics in extremely strong electromagnetic fields therefore have attracted wide research interest. Here we discuss a new SFQED phenomenon that is named as vacuum radiation. In vacuum radiation, a virtual electron loop obtain energy from time dependent external electric field and radiate an entangled photon pair. Features of vacuum radiation in a locally time dependent electric field including spectrum, characteristic temperature, production rate and power are given.

Vacuum radiation induced by time dependent electric field

Energy Technology Data Exchange (ETDEWEB)

Zhang, Bo, E-mail: zhangbolfrc@caep.cn [Department of High Energy Density Physics, Research Center of Laser Fusion, 621900, Mianyang, Sichuan (China); Laboratory of Science and Technology on Plasma Physics, Research Center of Laser Fusion, 621900, Mianyang, Sichuan (China); Zhang, Zhi-meng; Hong, Wei; He, Shu-Kai; Teng, Jian [Department of High Energy Density Physics, Research Center of Laser Fusion, 621900, Mianyang, Sichuan (China); Laboratory of Science and Technology on Plasma Physics, Research Center of Laser Fusion, 621900, Mianyang, Sichuan (China); Gu, Yu-qiu, E-mail: yqgu@caep.cn [Department of High Energy Density Physics, Research Center of Laser Fusion, 621900, Mianyang, Sichuan (China); Laboratory of Science and Technology on Plasma Physics, Research Center of Laser Fusion, 621900, Mianyang, Sichuan (China)

2017-04-10

Many predictions of new phenomena given by strong field quantum electrodynamics (SFQED) will be tested on next generation multi-petawatt laser facilities in the near future. These new phenomena are basis to understand physics in extremely strong electromagnetic fields therefore have attracted wide research interest. Here we discuss a new SFQED phenomenon that is named as vacuum radiation. In vacuum radiation, a virtual electron loop obtain energy from time dependent external electric field and radiate an entangled photon pair. Features of vacuum radiation in a locally time dependent electric field including spectrum, characteristic temperature, production rate and power are given.

Automatic electromagnetic valve for previous vacuum

International Nuclear Information System (INIS)

Granados, C. E.; Martin, F.

1959-01-01

A valve which permits the maintenance of an installation vacuum when electric current fails is described. It also lets the air in the previous vacuum bomb to prevent the oil ascending in the vacuum tubes. (Author)

Establishment of the laser induced breakdown spectroscopy in a vacuum atmosphere for a accuracy improvement

International Nuclear Information System (INIS)

Kim, Seung Hyun; Kim, H. D.; Shin, H. S.

2009-06-01

This report describes the fundamentals of the Laser Induced Breakdown Spectroscopy(LIBS), and it describes the quantitative analysis method in the vacuum condition to obtain a high measurement accuracy. The LIBS system employs the following major components: a pulsed laser, a gas chamber, an emission spectrometer, a detector, and a computer. When the output from a pulsed laser is focused onto a small spot on a sample, an optically induced plasma, called a laser-induced plasma (LIP) is formed at the surface. The LIBS is a laser-based sensitive optical technique used to detect certain atomic and molecular species by monitoring the emission signals from a LIP. This report was described a fundamentals of the LIBS and current states of research. And, It was described a optimization of measurement condition and characteristic analysis of a LIP by measurement of the fundamental metals. The LIBS system shows about a 0.63 ∼ 5.82% measurement errors and calibration curve for the 'Cu, Cr and Ni'. It also shows about a 5% less of a measurement errors and calibration curve for a Nd and Sm. As a result, the LIBS accuracy for a part was little improved than preexistence by the optimized condition

Advanced light source vacuum policy and vacuum guidelines for beamlines and experiment endstations

International Nuclear Information System (INIS)

Hussain, Z.

1995-08-01

The purpose of this document is to: (1) Explain the ALS vacuum policy and specifications for beamlines and experiment endstations. (2) Provide guidelines related to ALS vacuum policy to assist in designing beamlines which are in accordance with ALS vacuum policy. This document supersedes LSBL-116. The Advanced Light Source is a third generation synchrotron radiation source whose beam lifetime depends on the quality of the vacuum in the storage ring and the connecting beamlines. The storage ring and most of the beamlines share a common vacuum and are operated under ultra-high-vacuum (UHV) conditions. All endstations and beamline equipment must be operated so as to avoid contamination of beamline components, and must include proper safeguards to protect the storage ring vacuum from an accidental break in the beamline or endstation vacuum systems. The primary gas load during operation is due to thermal desorption and electron/photon induced desorption of contaminants from the interior of the vacuum vessel and its components. The desorption rates are considerably higher for hydrocarbon contamination, thus considerable emphasis is placed on eliminating these sources of contaminants. All vacuum components in a beamline and endstation must meet the ALS vacuum specifications. The vacuum design of both beamlines and endstations must be approved by the ALS Beamline Review Committee (BRC) before vacuum connections to the storage ring are made. The vacuum design is first checked during the Beamline Design Review (BDR) held before construction of the beamline equipment begins. Any deviation from the ALS vacuum specifications must be approved by the BRC prior to installation of the equipment on the ALS floor. Any modification that is incorporated into a vacuum assembly without the written approval of the BRC is done at the user's risk and may lead to rejection of the whole assembly

MHD Equilibrium with Reversed Current Density and Magnetic Islands Revisited: the Vacuum Vector Potential Calculus

Science.gov (United States)

L. Braga, F.

2013-10-01

The solution of Grad-Shafranov equation determines the stationary behavior of fusion plasma inside a tokamak. To solve the equation it is necessary to know the toroidal current density profile. Recent works show that it is possible to determine a magnetohydrodynamic (MHD) equilibrium with reversed current density (RCD) profiles that presents magnetic islands. In this work we show analytical MHD equilibrium with a RCD profile and analyze the structure of the vacuum vector potential associated with these equilibria using the virtual casing principle.

Post-arc current simulation based on measurement in vacuum circuit breaker with a one-dimensional particle-in-cell model

Science.gov (United States)

Jia, Shenli; Mo, Yongpeng; Shi, Zongqian; Li, Junliang; Wang, Lijun

2017-10-01

The post-arc dielectric recovery process has a decisive effect on the current interruption performance in a vacuum circuit breaker. The dissipation of residual plasma at the moment of current zero under the transient recovery voltage, which is the first stage of the post-arc dielectric recovery process and forms the post-arc current, has attracted many concerns. A one-dimensional particle-in-cell model is developed to simulate the measured post-arc current in the vacuum circuit breaker in this paper. At first, the parameters of the residual plasma are estimated roughly by the waveform of the post-arc current which is taken from measurements. After that, different components of the post-arc current, which are formed by the movement of charged particles in the residual plasma, are discussed. Then, the residual plasma density is adjusted according to the proportion of electrons and ions absorbed by the post-arc anode derived from the particle-in-cell simulation. After this adjustment, the post-arc current waveform obtained from the simulation is closer to that obtained from measurements.

Scalar field vacuum expectation value induced by gravitational wave background

Science.gov (United States)

Jones, Preston; McDougall, Patrick; Ragsdale, Michael; Singleton, Douglas

2018-06-01

We show that a massless scalar field in a gravitational wave background can develop a non-zero vacuum expectation value. We draw comparisons to the generation of a non-zero vacuum expectation value for a scalar field in the Higgs mechanism and with the dynamical Casimir vacuum. We propose that this vacuum expectation value, generated by a gravitational wave, can be connected with particle production from gravitational waves and may have consequences for the early Universe where scalar fields are thought to play an important role.

Vacuum phonon tunneling.

Science.gov (United States)

Altfeder, Igor; Voevodin, Andrey A; Roy, Ajit K

2010-10-15

Field-induced phonon tunneling, a previously unknown mechanism of interfacial thermal transport, has been revealed by ultrahigh vacuum inelastic scanning tunneling microscopy (STM). Using thermally broadened Fermi-Dirac distribution in the STM tip as in situ atomic-scale thermometer we found that thermal vibrations of the last tip atom are effectively transmitted to sample surface despite few angstroms wide vacuum gap. We show that phonon tunneling is driven by interfacial electric field and thermally vibrating image charges, and its rate is enhanced by surface electron-phonon interaction.

Induced vacuum energy-momentum tensor in the background of a cosmic string

OpenAIRE

Sitenko, Yu. A.; Vlasii, N. D.

2011-01-01

A massive scalar field is quantized in the background of a cosmic string which is generalized to a static flux-carrying codimension-2 brane in the locally flat multidimensional space-time. We find that the finite energy-momentum tensor is induced in the vacuum. The dependence of the tensor components on the brane flux and tension, as well as on the coupling to the space-time curvature scalar, is comprehensively analyzed. The tensor components are holomorphic functions of space dimension, decr...

Cosmic vacuum

International Nuclear Information System (INIS)

Chernin, Artur D

2001-01-01

Recent observational studies of distant supernovae have suggested the existence of cosmic vacuum whose energy density exceeds the total density of all the other energy components in the Universe. The vacuum produces the field of antigravity that causes the cosmological expansion to accelerate. It is this accelerated expansion that has been discovered in the observations. The discovery of cosmic vacuum radically changes our current understanding of the present state of the Universe. It also poses new challenges to both cosmology and fundamental physics. Why is the density of vacuum what it is? Why do the densities of the cosmic energy components differ in exact value but agree in order of magnitude? On the other hand, the discovery made at large cosmological distances of hundreds and thousands Mpc provides new insights into the dynamics of the nearby Universe, the motions of galaxies in the local volume of 10 - 20 Mpc where the cosmological expansion was originally discovered. (reviews of topical problems)

Cosmic vacuum

Energy Technology Data Exchange (ETDEWEB)

Chernin, Artur D [P.K. Shternberg State Astronomical Institute at the M.V. Lomonosov Moscow State University, Moscow (Russian Federation)

2001-11-30

Recent observational studies of distant supernovae have suggested the existence of cosmic vacuum whose energy density exceeds the total density of all the other energy components in the Universe. The vacuum produces the field of antigravity that causes the cosmological expansion to accelerate. It is this accelerated expansion that has been discovered in the observations. The discovery of cosmic vacuum radically changes our current understanding of the present state of the Universe. It also poses new challenges to both cosmology and fundamental physics. Why is the density of vacuum what it is? Why do the densities of the cosmic energy components differ in exact value but agree in order of magnitude? On the other hand, the discovery made at large cosmological distances of hundreds and thousands Mpc provides new insights into the dynamics of the nearby Universe, the motions of galaxies in the local volume of 10 - 20 Mpc where the cosmological expansion was originally discovered. (reviews of topical problems)

ITER vacuum vessel design and electromagnetic analysis on in-vessel components

International Nuclear Information System (INIS)

Ioki, K.; Johnson, G.; Shimizu, K.; Williamson, D.; Iizuka, T.

1995-01-01

Major functional requirements for the vacuum vessel are to provide the first safety barrier and to support electromagnetic loads due to plasma disruptions and vertical displacement events, and to withstand plausible accidents without losing confinement. A double wall structure concept has been developed for the vacuum vessel due to its beneficial characteristics from the viewpoints of structural integrity and electrical continuity. An electromagnetic analysis of the blanket modules and the vacuum vessel has been performed to investigate force distributions on in-vessel components. According to the vertical displacement events (VDE) scenario, which assumes a critical q-value of 1.5, the total downward vertical force, induced by coupling between the eddy current and external fields, is about 110 MN. We have performed a stress analysis for the vacuum vessel using the VDE disruption forces acting on the blankets, and a maximum stress intensity of 112 MPa was obtained in the vicinity of the lower support of the vessel. (orig.)

Carbon nanotubes based vacuum gauge

Science.gov (United States)

Rudyk, N. N.; Il'in, O. I.; Il'ina, M. V.; Fedotov, A. A.; Klimin, V. S.; Ageev, O. A.

2017-11-01

We have created an ionization type Vacuum gauge with sensor element based on an array of vertically aligned carbon nanotubes. Obtained asymmetrical current-voltage characteristics at different voltage polarity on the electrode with the CNTs. It was found that when applying a negative potential on an electrode with the CNTs, the current in the gap is higher than at a positive potential. In the pressure range of 1 ÷ 103 Torr vacuum gauge sensitivity was 6 mV/Torr (at a current of 4.5·10-5 A) and in the range of 10-5 ÷ 1 Torr was 10 mV/Torr (at a current of 1.3·10-5 A). It is shown that the energy efficiency of vacuum gauge can be increased in the case where electrode with CNT operates as an emitter of electrons.

Vacuum anti-shielding of monopoles

International Nuclear Information System (INIS)

Goebel, D.J.

1984-01-01

This chapter examines the difficulties in calculating the vacuum polarization, or magnetization, induced in the vacuum by a monopole. The usual Lagrangian formalism and consequent Feynman rules do not apply. Another problem is that the interaction strength between the monopole and a charge is not small (unless it vanishes exactly) because it is quantized to half integer values. Perturbation theory is therefore not applicable. The discussed problems are solved by using the old fashioned method of calculating a vacuum expectation value as a sum over single particle modes

Ultra high vacuum technology

CERN Multimedia

CERN. Geneva

2001-01-01

A short introduction for some basic facts and equations. Subsquently, discussion about: Building blocks of an ultrahigh vacuum system - Various types of pumps required to reach uhv and methods to reduce these effects - Outgassing phenomena induced by the presence of a particle beam and the most common methods to reduce these effects It will be given some practical examples from existing CERN accelerators and discuss the novel features of the future LHC vacuum system.

Deformation of contact surfaces in a vacuum interrupter after high-current interruptions

Energy Technology Data Exchange (ETDEWEB)

Wang, Haoran; Wang, Zhenxing, E-mail: zxwang@xjtu.edu.cn; Zhou, Zhipeng; Jiang, Yanjun; Wang, Jianhua; Geng, Yingsan; Liu, Zhiyuan [State Key Laboratory of Electrical Insulation and Power Equipment, Xi' an Jiaotong University, Xi' an 710049 (China)

2016-08-07

In a high-current interruption, the contact surface in a vacuum interrupter might be severely damaged by constricted vacuum arcs causing a molten area on it. As a result, a protrusion will be initiated by a transient recovery voltage after current zero, enhancing the local electric field and making breakdowns occur easier. The objective of this paper is to simulate the deformation process on the molten area under a high electric field by adopting the finite element method. A time-dependent Electrohydrodynamic model was established, and the liquid-gas interface was tracked by the level-set method. From the results, the liquid metal can be deformed to a Taylor cone if the applied electric field is above a critical value. This value is correlated to the initial geometry of the liquid metal, which increases as the size of the liquid metal decreases. Moreover, the buildup time of a Taylor cone obeys the power law t = k × E{sup −3}, where E is the initial electric field and k is a coefficient related to the material property, indicating a temporal self-similar characteristic. In addition, the influence of temperature has little impact on the deformation but has great impact on electron emission. Finally, the possible reason to initiate a delayed breakdown is associated with the deformation. The breakdown does not occur immediately when the voltage is just applied upon the gap but is postponed to several milliseconds later when the tip is formed on the liquid metal.

Current-Voltage Characteristics of DC Discharge in Micro Gas Jet Injected into Vacuum Environment

International Nuclear Information System (INIS)

Matra, K; Furuta, H; Hatta, A

2013-01-01

A current-voltage characteristic of direct current (DC) gas discharge operated in a micro gas jet injected into a secondary electron microscope (SEM) chamber is presented. Ar gas was injected through a 30 μm orifice gas nozzle (OGN) and was evacuated by an additional pump to keep the high vacuum environment. Gas discharges were ignited between the OGN as anode and a counter electrode of Si wafer. The discharge was self-pulsating in most of the cases while it was stable at lower pressure, larger gap length, and larger time averaged current. The self-pulsating discharge was oscillated by the RC circuit consisting of a stray capacitor and a large ballast resistor. The real time plots of voltage and current during the pulsating was investigated using a discharge model.

Study of the influence of adsorption of oxygen, hydrogen and water on radiation-induced thermally activated currents of magnesium oxide

International Nuclear Information System (INIS)

Wysocki, S.

1985-01-01

Recently, radiation-induced thermally activated currents (RITAC) have been studied in purified and magnesium-doped lithium fluoride. In the RITAC method, the electric field is applied at low temperature, only during irradiation. The present paper deals with the dipolar complexes generated by γ-radiations in the surface region of magnesium oxide in vacuum and in the presence of oxygen, hydrogen and water. Spectrally pure MgO single crystal spectrally pure oxygen and hydrogen and doubly distilled water were used. The electrodes were deposited on the (100) surface of MgO single crystal by vacuum evaporation of gold. Experimental details are given. A figure shows the thermally activated depolarization (TAD) curve for MgO in vacuum. In a TAD experiment, the sample was subjected to a constant electric field at 700 K and cooled. Upon reaching room temperature the electric field was removed In this case we observed a single peak at Tsub(max) = 511 K. A figure shows RITAC curves for an MgO sample in vacuum after irradiation. The results are shown and discussed. (author)

A vacuum sealed high emission current and transmission efficiency carbon nanotube triode

Energy Technology Data Exchange (ETDEWEB)

Di, Yunsong [School of Electronic Science & Engineering, Southeast University, Nanjing 210096 (China); Jiangsu Key Laboratory of Optoelectronic Technology, Nanjing Normal University, Nanjing 210023 (China); Wang, Qilong; Zhang, Xiaobing, E-mail: bell@seu.edu.cn; Lei, Wei; Du, Xiaofei; Yu, Cairu [School of Electronic Science & Engineering, Southeast University, Nanjing 210096 (China)

2016-04-15

A vacuum sealed carbon nanotubes (CNTs) triode with a concave and spoke-shaped Mo grid is presented. Due to the high aperture ratio of the grid, the emission current could be modulated at a relatively high electric field. Totally 75 mA emission current has been obtained from the CNTs cathode with the average applied field by the grid shifting from 8 to 13 V/μm. Whilst with the electron transmission efficiency of the grid over 56%, a remarkable high modulated current electron beam over 42 mA has been collected by the anode. Also contributed by the high aperture ration of the grid, desorbed gas molecules could flow away from the emission area rapidly when the triode has been operated at a relative high emission current, and finally collected by a vacion pump. The working pressure has been maintained at ∼1 × 10{sup −7} Torr, seldom spark phenomena occurred. Nearly perfect I-V curve and corresponding Fowler-Nordheim (FN) plot confirmed the accuracy of the measured data, and the emission current was long term stable and reproducible. Thusly, this kind of triode would be used as a high-power electron source.

Bench measurement of vacuum chamber impedances with wires

International Nuclear Information System (INIS)

Shafer, R.E.

1979-01-01

Particle beams travelling in an accelerator or storage ring vacuum chamber produce electric and magnetic fields which interact with the walls of the chamber. The induced wall currents in turn generate secondary fields which can interact with the beam, giving rise to both energy loss and other effects which can cause beam instability. In many simple geometries these effects can be calculated. In more complex geometries the calculations are difficult and very approximate. For this reason it is important that the effects be measured if possible prior to installation. As accelerators become larger and the number of vacuum chamber components more numerous, and as more severe beam intensity and stability requirements are placing lower limits on the longitudinal and transverse impedances, a less than adequate component will be more likely to limit machine performance

Experimental Investigation on the Influence of Axial Magnetic Field Distribution on Resisting the Constriction of a High-Current Vacuum Arc

International Nuclear Information System (INIS)

Shi Zongqian; Liu Zhigang; Jia Shenli; Song Xiaochuan; Wang Lijun

2009-01-01

Effect of the axial magnetic field (AMF) on resisting the constriction of a high-current vacuum arc is studied in this paper. Two typical AMF distributions were investigated, i.e., the traditional bell-shaped AMF, and the saddle-shaped AMF. Experiments were conducted in a detachable vacuum chamber with a rms arc current in the range of 10 kA to 25 kA. The arc column was photographed by a high-speed digital camera with an exposure time of 2 microseconds. The constriction of the vacuum arc was compared by processing the images of the arc column under the two different field configurations and numerically determining the dimensions of the arc column near the electrodes. It was also confirmed that the AMF distribution had a significant influence on its effectiveness in resisting arc constriction. Furthermore, the AMF strength near the periphery of the arc is more influential than that at the centre of the electrodes in resisting arc constriction.

A vacuum-UV laser-induced fluorescence experiment for measurement of rotationally and vibrationally excited H2

NARCIS (Netherlands)

Vankan, P.J.W.; Heil, S.B.S.; Mazouffre, S.; Engeln, R.A.H.; Schram, D.C.; Döbele, H.F.

2004-01-01

An experimental setup is built to detect spatially resolved rovibrationally excited hydrogen molecules via laser-induced fluorescence. To excite the hydrogen molecules, laser radiation is produced in the vacuum UV part of the spectrum. The laser radiation is tunable between 120 nm and 230 nm and has

Eddy current analysis by the finite element circuit method

International Nuclear Information System (INIS)

Kameari, A.; Suzuki, Y.

1977-01-01

The analysis of the transient eddy current in the conductors by ''Finite Element Circuit Method'' is developed. This method can be easily applied to various geometrical shapes of thin conductors. The eddy currents on the vacuum vessel and the upper and lower support plates of JT-60 machine (which is now being constructed by Japan Atomic Energy Research Institute) are calculated by this method. The magnetic field induced by the eddy current is estimated in the domain occupied by the plasma. And the force exerted to the vacuum vessel is also estimated

Tunneling and traversal of ultracold three-level atoms through vacuum-induced potentials

Energy Technology Data Exchange (ETDEWEB)

Badshah, Fazal; Irfan, Muhammad; Qamar, Shahid [Department of Physics and Applied Mathematics, Pakistan Institute of Engineering and Applied Sciences, Nilore, Islamabad 45650 (Pakistan); Qamar, Sajid [Department of Physics, COMSATS Institute of Information Technology, Islamabad (Pakistan)

2011-09-15

The passage of ultracold three-level atoms through the potential induced by the vacuum cavity mode is discussed using cascade atomic configuration. We study the tunneling or traversal time of the ultracold atoms via a bimodal high-Q cavity. It is found that the phase time, which may be considered as a measure for the time required to traverse the cavity, exhibits superclassical and subclassical behaviors. Further, the dark states and interference effects in cascade atomic configuration may influence the passage time of the atom through the cavity.

Tunneling and traversal of ultracold three-level atoms through vacuum-induced potentials

International Nuclear Information System (INIS)

Badshah, Fazal; Irfan, Muhammad; Qamar, Shahid; Qamar, Sajid

2011-01-01

The passage of ultracold three-level atoms through the potential induced by the vacuum cavity mode is discussed using cascade atomic configuration. We study the tunneling or traversal time of the ultracold atoms via a bimodal high-Q cavity. It is found that the phase time, which may be considered as a measure for the time required to traverse the cavity, exhibits superclassical and subclassical behaviors. Further, the dark states and interference effects in cascade atomic configuration may influence the passage time of the atom through the cavity.

The Control System of CERN Accelerators Vacuum (Current Status and Recent Improvements)

CERN Document Server

Gomes, P; Blanchard, S; Boccioli, M; Girardot, G; Vestergard, H; Kopylov, L; Mikheev, M

2011-01-01

The vacuum control system of most of the CERN accelerators is based on Siemens PLCs and on PVSS SCADA. After the transition from the LHC commissioning phase to its regular operation, there has been a number of additions and improvements to the vacuum control system. They were driven by new technical requirements and by feedback from the accelerator operators and vacuum specialists. New control functions have been implemented in the PLCs; new tools have been developed for the SCADA, while its ergonomics and navigation have been enhanced.

Technical specification for vacuum systems

International Nuclear Information System (INIS)

Khaw, J.

1987-01-01

The vacuum systems at the Stanford Linear Accelerator Center (SLAC) are primarily of all-metal construction and operate at pressures from 10 -5 to 10 -11 Torr. The primary gas loads during operation result from thermal desorption and beam-induced desorption from the vacuum chamber walls. These desorption rates can be extremely high in the case of hydrocarbons and other contaminants. These specifications place a major emphasis on eliminating contamination sources. The specifications and procedures have been written to insure the cleanliness and vacuum integrity of all SLAC vacuum systems, and to assist personnel involved with SLAC vacuum systems in choosing and designing components that are compatible with existing systems and meet the quality and reliability of SLAC vacuum standards. The specification includes requirements on design, procurement, fabrication, chemical cleaning, clean room practices, welding and brazing, helium leak testing, residual gas analyzer testing, bakeout, venting, and pumpdown. Also appended are specifications regarding acceptable vendors, isopropyl alcohol, bakeable valve cleaning procedure, mechanical engineering safety inspection, notes on synchrotron radiation, and specifications of numerous individual components

The control system of CERN accelerators vacuum (current status and recent improvements)

International Nuclear Information System (INIS)

Gomes, P.; Antoniotti, F.; Blanchard, S.; Boccioli, M.; Girardot, G.; Vestergard, H.; Kopylov, L.; Mikheev, M.

2012-01-01

The vacuum control system of most of the CERN accelerators is based on Siemens PLCs and on PVSS SCADA. After the transition from the LHC commissioning phase to its regular operation, there has been a number of additions and improvements to the vacuum control system. They were driven by new technical requirements and by feedback from the accelerator operators and vacuum specialists. New control functions have been implemented in the PLCs; new tools have been developed for the SCADA, while its ergonomic and navigation have been enhanced. (authors)

Vacuum phenomenon in the metatarsophalangeal joint of a horse

International Nuclear Information System (INIS)

Specht, T.E.; Poulos, P.W.; Metcalf, M.R.; Robertson, I.D.

1990-01-01

Vacuum phenomenon was induced inadvertently during radiographic examination of a metatarsophalangeal joint of a lame horse. The phenomenon was recreated in a sound horse when a metacarpophalangeal joint was radiographed in a stress-flexed position. Distraction of apposing articular surfaces may induce the vacuum phenomenon, which could result in misdiagnosis of an osteochondral defect or fracture

Design of the ZTH vacuum liner

International Nuclear Information System (INIS)

Prince, P.P.; Dike, R.S.

1987-01-01

The current status of the ZTh vacuum liner design is covered by this report. ZTH will be the first experiment to be installed in the CPRF (Confinement Physics Research Facility) at the Los Alamos National Laboratory and is scheduled to be operational at the rated current of 4 MA in 1992. The vacuum vessel has a 2.4m major radius and a 40 cm minor radius. Operating parameters which drive the vacuum vessel mechanical design include a 300 C bakeout temperature, an armour support system capable of withstanding 25 kV, a high toroidal resistance, 1250 kPa magnetic loading, a 10 minute cycle time, and high positional accuracy with respect to the conducting shell. The vacuum vessel design features which satisfy the operating parameters are defined

Interaction of a relativistic charge with vacuum channel elements

International Nuclear Information System (INIS)

Tatarnikov, V.A.

1989-01-01

The problems of beam acceleration and transport require accounting for the effects connected with natural fields of charged particles. Flying along the accelerating structure elements the bunch induces charges and currents on the walls which, in their turn, affect the accelerating particles creating a secondary electromagnetic field. The effect of vacuum channel walls on the charged particle energy is considered. In the approximation of an assigned current the expressions for integral changes in the energy of relativistic charge, are obtained. The difference in the nature of charge interaction with the inhomogeneities of the diaphragm type and a semiinfinite waveguide, is shown

Calculation of the electromagnetic forces on the ASDEX upgrade vacuum vessel on disruption of the plasma current

International Nuclear Information System (INIS)

Preis, H.

1986-01-01

This study investigates the magnetic field diffusion through the vacuum vessel of the ASDEX Upgrade tokamak that occurs on sudden disruption of the plasma current. Eddy currents are thereby produced in the vessel wall. Their time behaviour and distribution are determined. Furthermore, the vessel is permeated by various magnetic fields which, together with the eddy currents, exert magnetic forces in the vessel wall. These are also calculated. These numerical analyses are performed for two of the modes of operation envisaged for ASDEX Upgrade: the so-called limiter and single-null magnetic field configurations. (orig.)

Electron-positron pair creation from vacuum induced by variable electric field

International Nuclear Information System (INIS)

Marinov, M.S.; Popov, V.S.

1977-01-01

Problem is considered of spontaneous creation of electron-positron pairs from the vacuum induced by external electric field, that is homogeneous and depends on time in an arbitrary way. The Heisenberg equations of motion are obtained for the creation-annihilation operators. The solution is a linear canonical transformation. The problem is reduced to a set of differential equations for the second-order matrices determining this transformation. A consequence of the CP symmetry of the Dirac equation with an external electric field is that the e + e - pair is created from the vacuum in a state with total spin 1. The case when the variating electric field conserves its direction, is considered in more detail. In this case the equations are much simplified and may be reduced to the Riccati equation or to problem of oscillator with variable frequency, so the problem is equivalent to the one-dimensional quantal problem of a barrier penetration. Two approximate methods to calculate the pair creation probabilities are discussed: the quasiclassical approach and the antidiabatical method, applicable for sharp variations of the external field. Numerical estimates are obtained for the number of e + e - pairs produced by the field E(t) = E cos ωt. Group-theoretical aspects of the problem are also considered. (author)

Influence of Gap Distance on Vacuum Arc Characteristics of Cup Type AMF Electrode in Vacuum Interrupters

International Nuclear Information System (INIS)

Cheng Shaoyong; Xiu Shixin; Wang Jimei; Shen Zhengchao

2006-01-01

The greenhouse effect of SF 6 is a great concern today. The development of high voltage vacuum circuit breakers becomes more important. The vacuum circuit breaker has minimum pollution to the environment. The vacuum interrupter is the key part of a vacuum circuit breaker. The interrupting characteristics in vacuum and arc-controlling technique are the main problems to be solved for a longer gap distance in developing high voltage vacuum interrupters. To understand the vacuum arc characteristics and provide effective technique to control vacuum arc in a long gap distance, the arc mode transition of a cup-type axial magnetic field electrode is observed by a high-speed charge coupled device (CCD) video camera under different gap distances while the arc voltage and arc current are recorded. The controlling ability of the axial magnetic field on vacuum arc obviously decreases when the gap distance is longer than 40 mm. The noise components and mean value of the arc voltage significantly increase. The effective method for controlling the vacuum arc characteristics is provided by long gap distances based on the test results. The test results can be used as a reference to develop high voltage and large capacity vacuum interrupters

Vacuum compatibility of 3D-printed materials

OpenAIRE

Povilus, AP; Wurden, CJ; Vendeiro, Z; Baquero-Ruiz, M; Fajans, J

2014-01-01

The fabrication fidelity and vacuum properties are tested for currently available 3D-printed materials including polyamide, glass, acrylic, and sterling silver. The silver was the only material found to be suitable to ultrahigh vacuum environments due to outgassing and sublimation observed in other materials. © 2014 American Vacuum Society.

Characteristics of the ISABELLE vacuum system

International Nuclear Information System (INIS)

Aggus, J.R.; Edwards, D. Jr.; Halama, H.J.; Herrera, J.C.

1977-01-01

A discussion is given of the complete vacuum system of ISABELLE, emphasizing those design characteristics dictated by high vacuum, the avoidance of beam current loss, and the reduction of background. The experimental and theoretical justifications for the design are presented

TPX vacuum vessel transient thermal and stress conditions

International Nuclear Information System (INIS)

Feldshteyn, Y.; Dinkevich, S.; Feng, T.; Majumder, D.

1995-01-01

The TPX vacuum vessel provides the vacuum boundary for the plasma and the mechanical support for the internal components. Another function of the vacuum vessel is to contain neutron shielding water in the double wall space during normal operation. This double wall space serves as a heat reservoir for the entire vacuum vessel during bakeout. The vacuum vessel and the internal components are subjected to thermal stresses induced by a nonuniform temperature distribution within the structure during bakeout. A successful Conceptual Design Review in March 1993 has established superheated steam as the heating source of the vacuum vessel. A transient bakeout mode of the vacuum vessel and in-vessel components has been analyzed to evaluate transient period duration, proper temperature level, actual thermal stresses and performance of the steam equipment. Thermally, the vacuum vessel structure may be considered as an adiabatic system because it is perfectly insulated by the strong surrounding vacuum and multiple layers of superinsulation. Important aspects of the analysis are described herein

Analysis of effective electrical parameters for CFETR vacuum vessel

Energy Technology Data Exchange (ETDEWEB)

Liu, Xufeng; Xu, Weiwei, E-mail: wwxu@ipp.ac.cn; Du, Shuangsong; Zheng, Jinxing

2016-11-15

Highlights: • The eddy current distribution and variation of CFETR vacuum vessel during plasma disruption have been calculated. • Effective electrical parameters can be derived from the eddy current characters. • The method for eddy current and effective electrical parameters is suit for the complex shell with arbitrary shape. - Abstract: The electrical parameters of CFETR (China Fusion Engineering Test Reactor) vacuum vessel are very important to the design of control system and power supply system. Effective electrical parameters are relevant to the dynamic of eddy current. For complex structure, the distribution of eddy current can’t be obtained by analytical form. A method is presented to solve the eddy current of the vacuum vessel in this paper. The effective electrical parameters can be got from the eddy current distribution and variation. The time constant of the CFETR vacuum vessel is derived from the decay characteristics of the eddy current. And the effective resistance and inductance can be derived from the viewpoint of energy for a certain distribution of eddy current.

Enhanced Photocatalytic Activity of Vacuum-activated TiO2 Induced by Oxygen Vacancies.

Science.gov (United States)

Dong, Guoyan; Wang, Xin; Chen, Zhiwu; Lu, Zhenya

2018-05-01

TiO 2 (Degussa P25) photocatalysts harboring abundant oxygen vacancies (Vacuum P25) were manufactured using a simple and economic Vacuum deoxidation process. Control experiments showed that temperature and time of vacuum deoxidation had a significant effect on Vacuum P25 photocatalytic activity. After 240 min of visible light illumination, the optimal Vacuum P25 photocatalysts (vacuum deoxidation treated at 330 °C for 3 h) reach as high as 94% and 88% of photodegradation efficiency for rhodamine B (RhB) and tetracycline, respectively, which are around 4.5 and 4.9 times as that of pristine P25. The XPS, PL and EPR analyses indicated that the oxygen vacancies were produced in the Vacuum P25 during the vacuum deoxidation process. The oxygen vacancy states can produce vacancy energy level located below the conduction band minimum, which resulting in the bandgap narrowing, thus extending the photoresponse wavelength range of Vacuum P25. The positron annihilation analysis indicated that the concentrations ratio of bulk and surface oxygen vacancies could be adjusted by changing the vacuum deoxidation temperature and time. Decreasing the ratio of bulk and surface oxygen vacancies was shown to improve photogenerated electron-hole pair separation efficiency, which leads to an obvious enhancement of the visible photocatalytic activities of Vacuum P25. © 2017 The American Society of Photobiology.

Vacuum Arc Ion Sources

CERN Document Server

Brown, I.

2013-12-16

The vacuum arc ion source has evolved into a more or less standard laboratory tool for the production of high-current beams of metal ions, and is now used in a number of different embodiments at many laboratories around the world. Applications include primarily ion implantation for material surface modification research, and good performance has been obtained for the injection of high-current beams of heavy-metal ions, in particular uranium, into particle accelerators. As the use of the source has grown, so also have the operational characteristics been improved in a variety of different ways. Here we review the principles, design, and performance of vacuum arc ion sources.

Vacuum alignment and radiatively induced Fermi scale

DEFF Research Database (Denmark)

Alanne, Tommi

2017-01-01

We extend the discussion about vacuum misalignment by quantum corrections in models with composite pseudo-Goldstone Higgs boson to renormalisable models with elementary scalars. As a concrete example, we propose a framework, where the hierarchy between the unification and the Fermi scale emerges ...

[The sequential use of local vacuum magnetotherapy and papaverine electrophoresis with sinusoidal modulated currents in impotence].

Science.gov (United States)

Karpukhin, I V; Bogomol'nyĭ, V A

1997-01-01

105 patients with chronic nonspecific prostatitis were examined and treated with papaverin electrophoresis using sinusoidal modulated currents (SMC) and local vacuum magnetotherapy (LVMT). Papaverin SMC electrophoresis and LVMT stimulated cavernous circulation. The highest stimulation was achieved at successive use of LVMT and the electrophoresis. LVMT followed by the electrophoresis maintained good cavernous circulation for 5-6 hours after the procedure in the course of which several spontaneous erections were observed.

Magnetic analysis including the field due to vacuum vessel eddy currents in the Hitachi Tokamak (HT-2)

International Nuclear Information System (INIS)

Abe, Mitsushi; Takeuchi, Kazuhiro; Fukumoto, Hideshi; Otsuka, Michio

1989-01-01

A magnetic analysis to determine plasma surface position is applied to the magnetic data of the Hitachi Tokamak (HT-2). The analysis takes account of toroidal eddy currents on the vacuum vessel wall. Magnetic probes in HT-2 are placed on both sides of the wall (plasma side and outside), making it possible to determine magnitudes of eddy currents which flow in the toroidal direction. The magnitudes of the coil currents and eddy currents are determined so as to reproduce the measured magnetic fields, and to reconstruct flux surfaces and plasma surface are reconstructed. Taking into account the eddy currents, the determination errors of the plasma surface position are reduced by up to 1/2.3 during start-up and terminating phases, compared with the case without eddy currents. (author)

Investigation of carbon cathode surface before and after the passage of combined dc vacuum arc with superimposed high-current arc pulses

International Nuclear Information System (INIS)

Zavaleyev, V.; Walkowicz, J.; Moszynski, D.

2016-01-01

The paper presents the results of studies of carbon cathode surface before and after the passage of the combined DC vacuum-arc with superimposed high-current arc pulses. Investigations of surface morphology of carbon cathode showed, that secondary nuclei of high-density are formed after passing of the combined DC-pulse vacuum-arc, which results in the formation of a globular structures. The phase structure analysis by Raman spectroscopy showed that even at a minimum operation time (5 s) of the combined DC-pulse vacuum-arc broadening of the peaks 1355 and 1583 cm-1 occurs, which means that the carbon cathode surface undergo phase transformation. Results obtained by XPS spectroscopy demonstrate that the globular structures formed on the cathode surface are composed of sp 3 -bonded carbon atoms and carbon-oxygen bonds.

Expansion of a multicomponent current-carrying plasma jet into vacuum

International Nuclear Information System (INIS)

Krasov, V. I.; Paperny, V. L.

2017-01-01

An expression for the ion−ion coupling in a multicomponent plasma jet is derived for an arbitrary ratio between the thermal and relative velocities of the components. The obtained expression is used to solve the problem on the expansion of a current-carrying plasma microjet emitted from the cathode surface into vacuum. Two types of plasmas with two ion components are analyzed: (i) plasma in which the ion components of equal masses are in the charge states Z 1 = +1 and Z 2 = +2 and (ii) plasma with ions in equal charge states but with the mass ratio m 1 /m 2 = 2. It is shown that, for such plasmas, the difference between the velocities of the plasma components remains substantial (about 10% of the average jet velocity in case (i) and 15% in case (ii)) at distances of several centimeters from the emission center, where it can be measured experimentally, provided that its initial value at the emitting cathode surface exceeds a certain threshold. This effect is investigated as a function of the mass ratio and charge states of the ion components.

Induced vacuum energy-momentum tensor in the background of a cosmic string

International Nuclear Information System (INIS)

Sitenko, Yu A; Vlasii, N D

2012-01-01

A massive scalar field is quantized in the background of a cosmic string which is generalized to a static flux-carrying codimension-2 brane in the locally flat multidimensional spacetime. We find that the finite energy-momentum tensor is induced in the vacuum. The dependence of the tensor components on the brane flux and tension, as well as on the coupling to the spacetime curvature scalar, is comprehensively analyzed. The tensor components are holomorphic functions of space dimension, decreasing exponentially with the distance from the brane. The case of the massless quantized scalar field is also considered, and the relevance of Bernoulli’s polynomials of even order for this case is discussed. (paper)

Induced vacuum energy-momentum tensor in the background of a cosmic string

Science.gov (United States)

Sitenko, Yu A.; Vlasii, N. D.

2012-05-01

A massive scalar field is quantized in the background of a cosmic string which is generalized to a static flux-carrying codimension-2 brane in the locally flat multidimensional spacetime. We find that the finite energy-momentum tensor is induced in the vacuum. The dependence of the tensor components on the brane flux and tension, as well as on the coupling to the spacetime curvature scalar, is comprehensively analyzed. The tensor components are holomorphic functions of space dimension, decreasing exponentially with the distance from the brane. The case of the massless quantized scalar field is also considered, and the relevance of Bernoulli’s polynomials of even order for this case is discussed.

Gain with and without population inversion via vacuum-induced coherence in a V-type atom without external coherent driving

International Nuclear Information System (INIS)

Xu Weihua; Wu Jinhui; Gao Jinyue

2006-01-01

In a three-level V-type atomic system without any external coherent driving, owing to the coherence that results from the vacuum of the radiation field, both the probe gain with and without population inversion can be achieved with very weak incoherent pumping. The gain is achieved in the absence of any external coherent driving field, so it is different from the gain without inversion in ordinary laser-driven schemes where a coherent driving field is necessary to create the coherence. The gain is also different from the conventional lasing gain because the population inversion is achieved via vacuum-induced coherence, which is dependent on the atomic coherence

Experimental tests of vacuum energy

CERN Multimedia

CERN. Geneva

2015-01-01

While the current vacuum energy of the Universe is very small, in our standard cosmological picture it has been much larger at earlier epochs. We try to address the question of what are possible ways to try to experimentally verify this. One direction is to look for systems where vacuum energy constitutes a non-negligible fraction of the total energy, and study the properties of those. Another possibility is to focus on the epochs around cosmic phase transitions, when the vacuum energy is of the same order as the total energy. Along these lines we investigate properties of neutron stars and the imprint of phase transitions on primordial gravitational waves.

Thermal behavior induced by vacuum polarization on causal horizons in comparison with the standard heat bath formalism

Energy Technology Data Exchange (ETDEWEB)

Schroer, Bert [Centro Brasileiro de Pesquisas Fisicas (CBPF), Rio de Janeiro, RJ (Brazil)]|[Institut fuer Theoretische Physik, Berlin (Germany); E-mail schroer@cbpf.br

2003-02-01

Modular theory of operator algebras and the associated K MS property are used to obtain a unified description for the thermal aspects of the standard heat bath situation and those caused by quantum vacuum fluctuations from localization. An algebraic variant of light front holography reveals that the vacuum polarization on wedge horizons is compressed into the light ray direction. Their absence in the transverse direction is the prerequisite to an area (generalized Banknotes-) behavior of entropy-like measures which reveal the loss of purity due to restrictions to wedges and their horizons. Besides the well-known fact that localization-induced (generalized Hawking-) temperature is fixed by the geometric aspects, this area behavior (versus the standard volume dependence) constitutes the main difference between localization-caused and standard thermal behavior. (author)

Vacuum fluctuations of the supersymmetric field in curved background

International Nuclear Information System (INIS)

Bilić, Neven; Domazet, Silvije; Guberina, Branko

2012-01-01

We study a supersymmetric model in curved background spacetime. We calculate the effective action and the vacuum expectation value of the energy momentum tensor using a covariant regularization procedure. A soft supersymmetry breaking induces a nonzero contribution to the vacuum energy density and pressure. Assuming the presence of a cosmic fluid in addition to the vacuum fluctuations of the supersymmetric field an effective equation of state is derived in a self-consistent approach at one loop order. The net effect of the vacuum fluctuations of the supersymmetric fields in the leading adiabatic order is a renormalization of the Newton and cosmological constants.

Vacuum fluctuations of the supersymmetric field in curved background

Energy Technology Data Exchange (ETDEWEB)

Bilic, Neven, E-mail: bilic@thphys.irb.hr [Rudjer Boskovic Institute, POB 180, HR-10002 Zagreb (Croatia); Domazet, Silvije, E-mail: sdomazet@irb.hr [Rudjer Boskovic Institute, POB 180, HR-10002 Zagreb (Croatia); Guberina, Branko, E-mail: guberina@thphys.irb.hr [Rudjer Boskovic Institute, POB 180, HR-10002 Zagreb (Croatia)

2012-01-16

We study a supersymmetric model in curved background spacetime. We calculate the effective action and the vacuum expectation value of the energy momentum tensor using a covariant regularization procedure. A soft supersymmetry breaking induces a nonzero contribution to the vacuum energy density and pressure. Assuming the presence of a cosmic fluid in addition to the vacuum fluctuations of the supersymmetric field an effective equation of state is derived in a self-consistent approach at one loop order. The net effect of the vacuum fluctuations of the supersymmetric fields in the leading adiabatic order is a renormalization of the Newton and cosmological constants.

Vacuum arc anode phenomena

International Nuclear Information System (INIS)

Miller, H.C.

1976-01-01

A brief review of anode phenomena in vacuum arcs is presented. Discussed in succession are: the transition of the arc into the anode spot mode; the temperature of the anode before, during and after the anode spot forms; and anode ions. Characteristically the anode spot has a temperature of the order of the atmospheric boiling point of the anode material and is a copious source of vapor and energetic ions. The dominant mechanism controlling the transition of the vacuum arc into the anode spot mode appears to depend upon the electrode geometry, the electrode material, and the current waveform of the particular vacuum arc being considered. Either magnetic constriction in the gap plasma or gross anode melting can trigger the transition; indeed, a combination of the two is a common cause of anode spot formation

Vacuum horizontal drainage for depressurization of uranium tailings

International Nuclear Information System (INIS)

Pakalnis, R.; Chedsey, G.; Robertson, A.M.; Follin, S.

1985-01-01

A recent advance in tailings slope depressurization is the application of vacuum assist horizontal drainage. Horizontal drains have been used for several decades to reduce water pressures in slopes in order to improve stability. The benefit from vacuum assist arises from an increased hydraulic gradient caused by induced negative atmospheric pressures. The vacuum assist system has, since its inception in 1982, been successfully employed at two soil and four rock slope projects located in Western Canada. This paper describes the first application of this system in the United States. The technical feasibility of employing vacuum assisted horizontal drains to depressurize a uranium tailings dam near Riverton, Wyoming has been evaluated. Two horizontal drains (300 ft.) were installed and their effect monitored by nine piezometers. The study was conducted over a three-week internal with vacuum being applied for three and four day periods. The drawdowns achieved through vacuum drainage was found to be approximately double that obtained by gravity alone. The volume of water exhausted under vacuum during the seven day interval was approximately double that obtained by gravity alone

The Studies of a Vacuum Gap Breakdown after High-Current Arc Interruption with Increasing the Voltage

Science.gov (United States)

Schneider, A. V.; Popov, S. A.; Batrakov, A. V.; Dubrovskaya, E. L.; Lavrinovich, V. A.

2017-12-01

Vacuum-gap breakdown has been studied after high-current arc interruption with a subsequent increase in the transient recovery voltage across a gap. The effects of factors, such as the rate of the rise in the transient voltage, the potential of the shield that surrounds a discharge gap, and the arc burning time, have been determined. It has been revealed that opening the contacts earlier leads to the formation of an anode spot, which is the source of electrode material vapors into the discharge gap after current zero moment. Under the conditions of increasing voltage, this fact results in the breakdown. Too late opening leads to the breakdown of a short gap due to the high electric fields.

Quantum electrodynamics with unstable vacuum

Energy Technology Data Exchange (ETDEWEB)

Fradkin, E.S. (P.N. Lebedev Physical Inst., USSR Academy of Sciences, Moscow (USSR)); Gitman, D.M. (Moscow Inst. of Radio Engineering Electronics and Automation (USSR)); Shvartsman, Sh.M. (Tomsk State Pedagogical Inst. (USSR))

1991-01-01

Intense external fields destabilize vacuum inducing the creation of particle pairs. In this book the formalism of quantum electrodynamics (QED), using a special perturbation theory with matrix propagators, is systematically analyzed for such systems. The developed approach is, however, general for any quantum field with unstable vacuum. The authors propose solutions for real pair-creating fields. They discuss the general form for the causal function and many other Green's functions, as well as methods for finding them. Analogies to the optical theorem and rules for computing total probabilities are given, as are solutions for non-Abelian theories. (orig.).

Correlation of photon beam motion with vacuum chamber cooling on the NSLS x-ray ring

International Nuclear Information System (INIS)

Johnson, E.D.; Fauchet, A.M.; Zhang, Xiaohao.

1991-01-01

The NSLS X-ray ring exhibits a direct correlation between photon beam motion, and distortion of the ring vacuum chamber induced by fluctuations in the cooling system. We have made long term measurements of photon beam vertical position, accelerator vacuum chamber motion, process water temperatures, and angular motions of the magnets around one superperiod of the NSLS x-ray ring. Short term transients in water temperature cause deflection of the ring vacuum chamber which have in turn been shown to induce very small angular rotations of the magnets, on the order of 10 micro-radians. A larger and more difficult to correct effect is the drift in beam position over the course of a fill. This problem has been shown to be related to the thermal gradients that develop across the vacuum chamber which, as a consequence of the configuration of the chamber cooling, depend upon stored current. Orbit simulations based upon the measured rotations are in agreement with the observed beam motions, and reveal that certain patterns of correlated motions of the magnets can produce much larger errors than random motion or concerted motion of all the magnets. During the course of these measurements global orbit feedback was installed, and found to significantly reduce the orbit errors which could not be corrected at their source

Waveguide quantum electrodynamics in squeezed vacuum

Science.gov (United States)

You, Jieyu; Liao, Zeyang; Li, Sheng-Wen; Zubairy, M. Suhail

2018-02-01

We study the dynamics of a general multiemitter system coupled to the squeezed vacuum reservoir and derive a master equation for this system based on the Weisskopf-Wigner approximation. In this theory, we include the effect of positions of the squeezing sources which is usually neglected in the previous studies. We apply this theory to a quasi-one-dimensional waveguide case where the squeezing in one dimension is experimentally achievable. We show that while dipole-dipole interaction induced by ordinary vacuum depends on the emitter separation, the two-photon process due to the squeezed vacuum depends on the positions of the emitters with respect to the squeezing sources. The dephasing rate, decay rate, and the resonance fluorescence of the waveguide-QED in the squeezed vacuum are controllable by changing the positions of emitters. Furthermore, we demonstrate that the stationary maximum entangled NOON state for identical emitters can be reached with arbitrary initial state when the center-of-mass position of the emitters satisfies certain conditions.

Modeling of the anode surface deformation in high-current vacuum arcs with AMF contacts

International Nuclear Information System (INIS)

Huang, Xiaolong; Wang, Lijun; Deng, Jie; Jia, Shenli; Qin, Kang; Shi, Zongqian

2016-01-01

A high-current vacuum arc subjected to an axial magnetic field is maintained in a diffuse status. With an increase in arc current, the energy carried by the arc column to the anode becomes larger and finally leads to the anode temperature exceeding the melting point of the anode material. When the anode melting pool is formed, and the rotational plasma of the arc column delivers its momentum to the melting pool, the anode melting pool starts to rotate and also flow outwards along the radial direction, which has been photographed by some researchers using high-speed cameras. In this paper, the anode temperature and melting status is calculated using the melting and solidification model. The swirl flow of the anode melting pool and deformation of the anode is calculated using the magneto-hydrodynamic (MHD) model with the volume of fraction (VOF) method. All the models are transient 2D axial-rotational symmetric models. The influence of the impaction force of the arc plasma, electromagnetic force, viscosity force, and surface tension of the liquid metal are all considered in the model. The heat flux density injected into the anode and the arc pressure are obtained from the 3D numerical simulation of the high-current vacuum arc using the MHD model, which gives more realistic parameters for the anode simulation. Simulation results show that the depth of the anode melting pool increases with an increase in the arc current. Some droplets sputter out from the anode surface, which is caused by the inertial centrifugal force of the rotational melting pool and strong plasma pressure. Compared with the previous anode melting model without consideration of anode deformation, when the deformation and swirl flow of the anode melting pool are considered, the anode temperature is relatively lower, and just a little more than the melting point of Cu. This is because of liquid droplets sputtering out of the anode surface taking much of the energy away from the anode surface. The

Vacuum alignment and radiatively induced Fermi scale

Directory of Open Access Journals (Sweden)

Alanne Tommi

2017-01-01

Full Text Available We extend the discussion about vacuum misalignment by quantum corrections in models with composite pseudo-Goldstone Higgs boson to renormalisable models with elementary scalars. As a concrete example, we propose a framework, where the hierarchy between the unification and the Fermi scale emerges radiatively. This scenario provides an interesting link between the unification and Fermi scale physics.

Expansion of a multicomponent current-carrying plasma jet into vacuum

Energy Technology Data Exchange (ETDEWEB)

Krasov, V. I.; Paperny, V. L., E-mail: paperny@math.isu.runnet.ru [Irkutsk State University (Russian Federation)

2017-03-15

An expression for the ion−ion coupling in a multicomponent plasma jet is derived for an arbitrary ratio between the thermal and relative velocities of the components. The obtained expression is used to solve the problem on the expansion of a current-carrying plasma microjet emitted from the cathode surface into vacuum. Two types of plasmas with two ion components are analyzed: (i) plasma in which the ion components of equal masses are in the charge states Z{sub 1}= +1 and Z{sub 2}= +2 and (ii) plasma with ions in equal charge states but with the mass ratio m{sub 1}/m{sub 2} = 2. It is shown that, for such plasmas, the difference between the velocities of the plasma components remains substantial (about 10% of the average jet velocity in case (i) and 15% in case (ii)) at distances of several centimeters from the emission center, where it can be measured experimentally, provided that its initial value at the emitting cathode surface exceeds a certain threshold. This effect is investigated as a function of the mass ratio and charge states of the ion components.

Change in carbon nanofiber resistance from ambient to vacuum

Directory of Open Access Journals (Sweden)

Shusaku Maeda

2011-06-01

Full Text Available The electrical properties of carbon nanofibers (CNFs can be affected by adsorbed gas species. In this study, we compare the resistance values of CNF devices in a horizontal configuration in air and under vacuum. CNFs in air are observed to possess lower current capacities compared to those in vacuum. Further, Joule heating due to current stressing can result in desorption of gas molecules responsible for carrier trapping, leading to lower resistances and higher breakdown currents in vacuum, where most adsorbed gaseous species are evacuated before any significant re-adsorption can occur. A model is proposed to describe these observations, and is used to estimate the number of adsorbed molecules on a CNF device.

Luminescence evolution from alumina ceramic surface before flashover under direct and alternating current voltage in vacuum

Energy Technology Data Exchange (ETDEWEB)

Su, Guo-Qiang; Wang, Yi-Bo; Song, Bai-Peng; Mu, Hai-Bao, E-mail: haibaomu@xjtu.edu.cn, E-mail: gjzhang@xjtu.edu.cn; Zhang, Guan-Jun, E-mail: haibaomu@xjtu.edu.cn, E-mail: gjzhang@xjtu.edu.cn [State Key Laboratory of Electrical Insulation and Power Equipment, School of Electrical Engineering, Xi’an Jiaotong University, Xi’an, Shaanxi 710049 (China); Li, Feng; Wang, Meng [Institute of Fluid Physics, China Academy of Engineering Physics, Mianyang, Sichuan 621900 (China)

2016-06-15

The luminescence evolution phenomena from alumina ceramic surface in vacuum under high voltage of direct and alternating current are reported, with the voltage covering a large range from far below to close to the flashover voltage. Its time resolved and spatial distributed behaviors are examined by a photon counting system and an electron-multiplying charge-coupled device (EMCCD) together with a digital camera, respectively. The luminescence before flashover exhibits two stages as voltage increasing, i.e., under a relative low voltage (Stage A), the luminescence is ascribed to radiative recombination of hetero-charges injected into the sample surface layer by Schottky effect; under a higher voltage (Stage B), a stable secondary electron emission process, resulting from the Fowler-Nordheim emission at the cathode triple junction (CTJ), is responsible for the luminescence. Spectrum analysis implies that inner secondary electrons within the surface layer of alumina generated during the SSEE process also participate in the luminescence of Stage B. A comprehensive interpretation of the flashover process is formulated, which might promote a better understanding of flashover issue in vacuum.

2XIIB vacuum vessel: a unique design

International Nuclear Information System (INIS)

Hibbs, S.M.; Calderon, M.O.

1975-01-01

The 2XIIB mirror confinement experiment makes unique demands on its vacuum system. The confinement coil set encloses a cavity whose surface is comprised of both simple and compound curves. Within this cavity and at the core of the machine is the operating vacuum which is on the order of 10 -9 Torr. The vacuum container fits inside the cavity, presenting an inside surface suitable for titanium getter pumping and a means of removing the heat load imposed by incandescent sublimator wires. In addition, the cavity is constructed of nonmagnetic and nonconducting materials (nonmetals) to avoid distortion of the pulsed confinement field. It is also isolated from mechanical shocks induced in the machine's main structure when the coils are pulsed. This paper describes the design, construction, and operation of the 2XIIB high-vacuum vessel that has been performing successfully since early 1974

Probing the diffusion of vacuum ultraviolet ({lambda} = 172 nm) induced oxidants by nanoparticles immobilization

Energy Technology Data Exchange (ETDEWEB)

Khatri, Om P.; Hatanaka, Takeshi; Murase, Kuniaki [Department of Materials Science and Engineering, Kyoto University, Sakyo-ku, Kyoto 606-8501 (Japan); Sugimura, Hiroyuki, E-mail: hiroyuki.sugimura@materials.mbox.media.kyoto-u.ac.jp [Department of Materials Science and Engineering, Kyoto University, Sakyo-ku, Kyoto 606-8501 (Japan)

2009-09-30

Vacuum ultraviolet (VUV, {lambda} = 172 nm) patterning of alkyl monolayer on silicon surface has been demonstrated with emphasis on the diffusion of VUV induced oxygen-derived active species, which are accountable for the pattern broadening. The VUV photons photo-dissociates the atmospheric oxygen and water molecules into the oxygen-derived active species (oxidants). These oxidants photo-oxidize the hexadecyl (HD) monolayer in VUV irradiated regions (Khatri et al., Langmuir. 24 (2008) 12077), as well as the little concentration of oxidants diffuses towards the masked areas. In this study, we performed VUV patterning at a vacuum pressure of 10 Pa to track the diffusion pathways for the oxidants with help of gold nanoparticles (AuNPs; {phi} = 10 nm) immobilization. At VUV irradiated sites AuNPs are found as uniformly distributed, but adjacent to the pattern boundary we observed quasi-linear arrays of AuNPs, which are determined by diffusion pathways of the oxidants. The diffusion of oxidants plays vital role in pattern broadening. The site selective anchoring of AuNPs demonstrates the utility of VUV photons for the construction of functional materials with microstructural architecture.

Development of Low Surge Vacuum Contact with Te

Energy Technology Data Exchange (ETDEWEB)

Kim, B. S.; Lee, H. W.; Woo, B. C.; Kim, B. G. [Korea Electrotechnology Research Institute, Changwon (Korea, Republic of)

1996-12-01

The purpose of this study is to develop of low surge Te contact for vacuum circuit breaker. The vacuum circuit breaker have various advantages such that it is free from maintenance, does not bring about public pollution, is excellent in its current breaking property, and so forth, on account of which the extent of its application has become broadened rapidly. For the characteristics of the contact material for the vacuum circuit breaker to satisfy, there may be enumerated: (1)large current breaking capacity; (2)high voltage withstand; (3)small contact resistance; (4)small melt-adhesive force; (5)low chopping current value; (6)good workability; (7)sufficient mechanical strength; and so forth. In this study we used cobalt for based refractory material having high melting temperature and intermetallic material between tellurium and silver to reduce chopping current. The contact materials were produced in accordance with the powder metallurgy using the method of infiltration. Production of the contact material was carried out in such a method that cobalt powder having average particle size of 50{mu}m, pre sintered in H{sub 2} atmosphere, 900 degree C , 2 hour. Ag ingot and Te(Se) were alloyed using high frequency furnaced in vacuum. And then Ag-Te(Se) alloy was infiltrated to Co skeleton in H{sub 2} atmosphere, 1000 degree C , 1 hour. The melting of the alloy to be infiltrated was carried out in a vacuum sealed quartz tube and be analysed by X-ray diffraction, scanning electron microscope, optical microscope and energy dispersive energy spectrometer. In the alloying of silver and tellurium, tellurium does not exist in single element but Ag{sub 2}Te intermetallic compound. And In Ag and Se, Se does not exist in single element but Ag{sub 2}Se intermetallic compound. We also produced the test vacuum interruptor to evaluate the electrode properties in vacuum atmosphere. The electrical properties of Co-(Ag-Se) electrode have better value than that of Co-(Ag-Te) electrode

Heavy-ion induced current through an oxide layer

International Nuclear Information System (INIS)

Takahashi, Yoshihiro; Ohki, Takahiro; Nagasawa, Takaharu; Nakajima, Yasuhito; Kawanabe, Ryu; Ohnishi, Kazunori; Hirao, Toshio; Onoda, Shinobu; Mishima, Kenta; Kawano, Katsuyasu; Itoh, Hisayoshi

2007-01-01

In this paper, the heavy-ion induced current in MOS structure is investigated. We have measured the transient gate current in a MOS capacitor and a MOSFET induced by single heavy-ions, and found that a transient current can be observed when the semiconductor surface is under depletion condition. In the case of MOSFET, a transient gate current with both positive and negative peaks is observed if the ion hits the gate area, and that the total integrated charge is almost zero within 100-200 ns after irradiation. From these results, we conclude that the radiation-induced gate current is dominated by a displacement current. We also discuss the generation mechanism of the radiation-induced current through the oxide layer by device simulation

Investigations Of A Pulsed Cathodic Vacuum Arc

Science.gov (United States)

Oates, T. W. H.; Pigott, J.; Denniss, P.; Mckenzie, D. R.; Bilek, M. M. M.

2003-06-01

Cathodic vacuum arcs are well established as a method for producing thin films for coatings and as a source of metal ions. Research into DC vacuum arcs has been going on for over ten years in the School of Physics at the University of Sydney. Recently a project was undertaken in the school to design and build a pulsed CVA for use in the investigation of plasma sheaths and plasma immersion ion implantation. Pulsed cathodic vacuum arcs generally have a higher current and plasma density and also provide a more stable and reproducible plasma density than their DC counterparts. Additionally it has been shown that if a high repetition frequency can be established the deposition rate of pulsed arcs is equal to or greater than that of DC arcs with a concomitant reduction in the rate of macro-particle formation. We present here results of our investigations into the building of a center-triggered pulsed cathodic vacuum arc. The design of the power supply and trigger mechanism and the geometry of the anode and cathode are examined. Observations of type I and II arc spots using a CCD camera, and cathode spot velocity dependence on arc current will be presented. The role of retrograde motion in a high current pulsed arc is discussed.

Investigations Of A Pulsed Cathodic Vacuum Arc

International Nuclear Information System (INIS)

Oates, T.W.H.; Pigott, J.; Denniss, P.; Mckenzie, D.R.; Bilek, M.M.M.

2003-01-01

Cathodic vacuum arcs are well established as a method for producing thin films for coatings and as a source of metal ions. Research into DC vacuum arcs has been going on for over ten years in the School of Physics at the University of Sydney. Recently a project was undertaken in the school to design and build a pulsed CVA for use in the investigation of plasma sheaths and plasma immersion ion implantation. Pulsed cathodic vacuum arcs generally have a higher current and plasma density and also provide a more stable and reproducible plasma density than their DC counterparts. Additionally it has been shown that if a high repetition frequency can be established the deposition rate of pulsed arcs is equal to or greater than that of DC arcs with a concomitant reduction in the rate of macro-particle formation. We present here results of our investigations into the building of a center-triggered pulsed cathodic vacuum arc. The design of the power supply and trigger mechanism and the geometry of the anode and cathode are examined. Observations of type I and II arc spots using a CCD camera, and cathode spot velocity dependence on arc current will be presented. The role of retrograde motion in a high current pulsed arc is discussed

Magnetically enhanced vacuum arc thruster

International Nuclear Information System (INIS)

Keidar, Michael; Schein, Jochen; Wilson, Kristi; Gerhan, Andrew; Au, Michael; Tang, Benjamin; Idzkowski, Luke; Krishnan, Mahadevan; Beilis, Isak I

2005-01-01

A hydrodynamic model of the vacuum arc thruster and its plume is described. Primarily an effect of the magnetic field on the plume expansion and plasma generation is considered. Two particular examples are investigated, namely the magnetically enhanced co-axial vacuum arc thruster (MVAT) and the vacuum arc thruster with ring electrodes (RVAT). It is found that the magnetic field significantly decreases the plasma plume radial expansion under typical conditions. Predicted plasma density profiles in the plume of the MVAT are compared with experimental profiles, and generally a good agreement is found. In the case of the RVAT the influence of the magnetic field leads to plasma jet deceleration, which explains the non-monotonic dependence of the ion current density, on an axial magnetic field observed experimentally

Magnetically enhanced vacuum arc thruster

Energy Technology Data Exchange (ETDEWEB)

Keidar, Michael [University of Michigan, Ann Arbor 48109 MI (United States); Schein, Jochen [Alameda Applied Science Corporation, San Leandro, CA 94577 (United States); Wilson, Kristi [Alameda Applied Science Corporation, San Leandro, CA 94577 (United States); Gerhan, Andrew [Alameda Applied Science Corporation, San Leandro, CA 94577 (United States); Au, Michael [Alameda Applied Science Corporation, San Leandro, CA 94577 (United States); Tang, Benjamin [Alameda Applied Science Corporation, San Leandro, CA 94577 (United States); Idzkowski, Luke [Alameda Applied Science Corporation, San Leandro, CA 94577 (United States); Krishnan, Mahadevan [Alameda Applied Science Corporation, San Leandro, CA 94577 (United States); Beilis, Isak I [Tel Aviv University, Tel Aviv (Israel)

2005-11-01

A hydrodynamic model of the vacuum arc thruster and its plume is described. Primarily an effect of the magnetic field on the plume expansion and plasma generation is considered. Two particular examples are investigated, namely the magnetically enhanced co-axial vacuum arc thruster (MVAT) and the vacuum arc thruster with ring electrodes (RVAT). It is found that the magnetic field significantly decreases the plasma plume radial expansion under typical conditions. Predicted plasma density profiles in the plume of the MVAT are compared with experimental profiles, and generally a good agreement is found. In the case of the RVAT the influence of the magnetic field leads to plasma jet deceleration, which explains the non-monotonic dependence of the ion current density, on an axial magnetic field observed experimentally.

Fast photography of XeCl laser-induced plasma of graphite in vacuum and in nitrogen atmosphere

International Nuclear Information System (INIS)

Acquaviva, S; De Giorgi, M L

2003-01-01

Fast photography with a gated intensified close-coupled device camera was applied to provide a visualization of the temporal and spatial evolution of chemical species in a plasma induced by a 308 nm laser during graphite ablation, in vacuum and in nitrogen atmosphere. A sequence of frames of the luminous plume was recorded, using narrow interference filters, and plasma expansion velocity was estimated from the acquired images. Present observations agree with optical emission spectroscopic investigations performed under the same experimental conditions

Application of high speed photography for high current vacuum arcs

NARCIS (Netherlands)

Damstra, G.C.; Merck, W.F.H.; Vossen, J.W.G.L.; Janssen, M.F.P.; Bouwmeester, C.E.

1998-01-01

A high speed image detection system for 106 frames per second or 107 streaks per second has been developed for the testing of vacuum circuit breakers, using 10×16 optical fibres for light transfer to 160 fast photo diodes. The output of these diodes is multiplexed, AD converted in a 4 bit

Photoinduced current and emission induced by current in a ...

Indian Academy of Sciences (India)

... Refresher Courses · Symposia · Live Streaming. Home; Journals; Pramana – Journal of Physics; Volume 86; Issue 3. Photoinduced current and emission induced by current in a nanowire transistor: Temperature dependence. Darehdor Mahvash Arabi Shahtahmassebi Nasser. Regular Volume 86 Issue 3 March 2016 pp ...

Starobinsky-Like Inflation and Running Vacuum in the Context of Supergravity

Directory of Open Access Journals (Sweden)

Spyros Basilakos

2016-07-01

Full Text Available We describe the primeval inflationary phase of the early Universe within a quantum field theoretical (QFT framework that can be viewed as the effective action of vacuum decay in the early times. Interestingly enough, the model accounts for the “graceful exit” of the inflationary phase into the standard radiation regime. The underlying QFT framework considered here is supergravity (SUGRA, more specifically an existing formulation in which the Starobinsky-type inflation (de Sitter background emerges from the quantum corrections to the effective action after integrating out the gravitino fields in their (dynamically induced massive phase. We also demonstrate that the structure of the effective action in this model is consistent with the generic idea of re-normalization group (RG running of the cosmological parameters; specifically, it follows from the corresponding RG equation for the vacuum energy density as a function of the Hubble rate, ρ Λ ( H . Overall, our combined approach amounts to a concrete-model realization of inflation triggered by vacuum decay in a fundamental physics context, which, as it turns out, can also be extended for the remaining epochs of the cosmological evolution until the current dark energy era.

Plasma instability of a vacuum arc centrifuge

International Nuclear Information System (INIS)

Hole, M.J.; Dallaqua, R.S.; Simpson, S.W.; Del Bosco, E.

2002-01-01

Ever since conception of the vacuum arc centrifuge in 1980, periodic fluctuations in the ion saturation current and floating potential have been observed in Langmuir probe measurements in the rotation region of a vacuum arc centrifuge. In this work we develop a linearized theoretical model to describe a range of instabilities in the vacuum arc centrifuge plasma column, and then test the validity of the description through comparison with experiment. We conclude that the observed instability is a 'universal' instability, driven by the density gradient, in a plasma with finite conductivity

Tailored vacuum chambers for ac magnets

International Nuclear Information System (INIS)

Harvey, A.

1985-01-01

The proposed LAMPF-II accelerator has a 60-Hz booster synchrotron and a 3-Hz main ring. To provide a vacuum enclosure inside the magnets with low eddy-current losses and minimal field distortion, yet capable of carrying rf image currents and providing beam stabilization, we propose an innovative combination pipe. Structurally, the enclosure is high-purity alumina ceramic, which is strong, radiation resistant, and has good vacuum properties. Applied to the chamber are thin, spaced, silver conductors using adapted thick-film technology. The conductor design can be tailored to the stabilization requirements, for example, longitudinal conductors for image currents, circumferential for transverse stabilization. The inside of the chamber has a thin, resistive coating to avoid charge build-up. The overall 60-Hz power loss is less than 100 W/m

FRIB driver linac vacuum model and benchmarks

CERN Document Server

Durickovic, Bojan; Kersevan, Roberto; Machicoane, Guillaume

2014-01-01

The Facility for Rare Isotope Beams (FRIB) is a superconducting heavy-ion linear accelerator that is to produce rare isotopes far from stability for low energy nuclear science. In order to achieve this, its driver linac needs to achieve a very high beam current (up to 400 kW beam power), and this requirement makes vacuum levels of critical importance. Vacuum calculations have been carried out to verify that the vacuum system design meets the requirements. The modeling procedure was benchmarked by comparing models of an existing facility against measurements. In this paper, we present an overview of the methods used for FRIB vacuum calculations and simulation results for some interesting sections of the accelerator. (C) 2013 Elsevier Ltd. All rights reserved.

Current-induced runaway vibrations in dehydrogenated graphene nanoribbons

Directory of Open Access Journals (Sweden)

Rasmus Bjerregaard Christensen

2016-01-01

Full Text Available We employ a semi-classical Langevin approach to study current-induced atomic dynamics in a partially dehydrogenated armchair graphene nanoribbon. All parameters are obtained from density functional theory. The dehydrogenated carbon dimers behave as effective impurities, whose motion decouples from the rest of carbon atoms. The electrical current can couple the dimer motion in a coherent fashion. The coupling, which is mediated by nonconservative and pseudo-magnetic current-induced forces, change the atomic dynamics, and thereby show their signature in this simple system. We study the atomic dynamics and current-induced vibrational instabilities using a simplified eigen-mode analysis. Our study illustrates how armchair nanoribbons can serve as a possible testbed for probing the current-induced forces.

Radiation zoning for vacuum equipment of the CERN Large Hadron Collider

CERN Document Server

Mahner, E; Cruikshank, P; Forkel-Wirth, D; Jiménez, J M

2010-01-01

Beam losses in high-energy particle accelerators are responsible for beam lifetime degradation. In the LHC beam losses will create a shower of particles while interacting with materials from the beam pipes and surroundings, resulting in a partial activation of material in the tunnel. Efforts have been made during the accelerator design to monitor and to reduce the activation induced by beam losses. Traceability for all vacuum components has been established providing a tool to follow-up individually each component or subcomponents installed in the tunnel, regardless of their future destination e.g. recycling or disposal. In the latter case, the history of vacuum components will allow calculating the beam-induced activation and permit comparisons with in-situ and ex-situ measurements. This zoning will also help to reduce collective and individual radiation doses to personnel during interventions. The paper presents the vacuum system layout and describes the LHC vacuum zoning and its implementation using an ORA...

Effect of Coil Current on the Properties of Hydrogenated DLC Coatings Fabricated by Filtered Cathodic Vacuum Arc Technique

Science.gov (United States)

Liao, Bin; Ouyang, Xiaoping; Zhang, Xu; Wu, Xianying; Bian, Baoan; Ying, Minju; Jianwu, Liu

2018-01-01

We successfully prepared hydrogenated DLC (a-C:H) with a thickness higher than 25 μm on stainless steel using a filtered cathode vacuum arc (FCVA) technique. The structural and mechanical properties of DLC were systematically analyzed using different methods such as x-ray photoelectron spectroscopy, Raman spectroscopy, scanning electron microscopy, Vickers hardness, nanohardness, and friction and wear tests. The effect of coil current on the arc voltage, ion current, and mechanical properties of resultant films was systematically investigated. The novelty of this study is the fabrication of DLC with Vickers hardness higher than 1500 HV, in the meanwhile with the thickness higher than 30 μm through varying the coil current with FCVA technique. The results indicated that the ion current, deposition rate, friction coefficient, and Vickers hardness of DLC were significantly affected by the magnetic field inside the filtered duct.

Recent advances in vacuum arc ion sources

International Nuclear Information System (INIS)

Brown, I.G.; Anders, A.; Anders, S.; Dickinson, M.R.; MacGill, R.A.; Oks, E.M.

1995-07-01

Intense beams of metal ions can be formed from a vacuum arc ion source. Broadbeam extraction is convenient, and the time-averaged ion beam current delivered downstream can readily be in the tens of milliamperes range. The vacuum arc ion source has for these reasons found good application for metallurgical surface modification--it provides relatively simple and inexpensive access to high dose metal ion implantation. Several important source developments have been demonstrated recently, including very broad beam operation, macroparticle removal, charge state enhancement, and formation of gaseous beams. The authors have made a very broad beam source embodiment with beam formation electrodes 50 cm in diameter, producing a beam of width ∼35 cm for a nominal beam area of ∼1,000 cm 2 , and a pulsed Ti beam current of about 7 A was formed at a mean ion energy of ∼100 keV. Separately, they've developed high efficiency macroparticle-removing magnetic filters and incorporated such a filter into a vacuum arc ion source so as to form macroparticle-free ion beams. Jointly with researchers at the High Current Electronics Institute at Tomsk, Russia, and the Gesellschaft fuer Schwerionenforschung at Darmstadt, Germany, they've developed a compact technique for increasing the charge states of ions produced in the vacuum arc plasma and thus providing a simple means of increasing the ion energy at fixed extractor voltage. Finally, operation with mixed metal and gaseous ion species has been demonstrated. Here, they briefly review the operation of vacuum marc ion sources and the typical beam and implantation parameters that can be obtained, and describe these source advances and their bearing on metal ion implantation applications

Current-induced dynamics in carbon atomic contacts

DEFF Research Database (Denmark)

Lu, Jing Tao; Gunst, Tue; Brandbyge, Mads

2011-01-01

voltage, which can be used to explore current-induced vibrational instabilities due the NC/BP forces. Furthermore, using tight-binding and the Brenner potential we illustrate how Langevin-type molecular-dynamics calculations including the Joule heating effect for the carbon-chain systems can be performed...... be used to explore current-induced dynamics and instabilities. We find instabilities at experimentally relevant bias and gate voltages for the carbon-chain system. © 2011 Lü et al....... carbon chain connecting electrically gated graphene electrodes. This illustrates how the device stability can be predicted solely from the modes obtained from the Langevin equation, including the current-induced forces. We point out that the gate offers control of the current, independent of the bias...

Parametric Amplification of Vacuum Fluctuations in a Spinor Condensate

DEFF Research Database (Denmark)

Klempt, C.; Topic, O.; Gebreyesus, G.

2010-01-01

to correlated pair creation in the mF=±1 states from an initial mF=0 condensate, which acts as a vacuum for mF≠0. Although this pair creation from a pure mF=0 condensate is ideally triggered by vacuum fluctuations, unavoidable spurious initial mF=±1 atoms induce a classical seed which may become the dominant...... triggering mechanism. We show that pair creation is insensitive to a classical seed for sufficiently large magnetic fields, demonstrating the dominant role of vacuum fluctuations. The presented system thus provides a direct path towards the generation of nonclassical states of matter....

Relaxed plasma-vacuum systems

International Nuclear Information System (INIS)

Spies, G.O.; Lortz, D.; Kaiser, R.

2001-01-01

Taylor's theory of relaxed toroidal plasmas (states of lowest energy with fixed total magnetic helicity) is extended to include a vacuum between the plasma and the wall. In the extended variational problem, one prescribes, in addition to the helicity and the magnetic fluxes whose conservation follows from the perfect conductivity of the wall, the fluxes whose conservation follows from the assumption that the plasma-vacuum interface is also perfectly conducting (if the wall is a magnetic surface, then one has the toroidal and the poloidal flux in the vacuum). Vanishing of the first energy variation implies a pressureless free-boundary magnetohydrostatic equilibrium with a Beltrami magnetic field in the plasma, and in general with a surface current in the interface. Positivity of the second variation implies that the equilibrium is stable according to ideal magnetohydrodynamics, that it is a relaxed state according to Taylor's theory if the interface is replaced by a wall, and that the surface current is nonzero (at least if there are no closed magnetic field lines in the interface). The plane slab, with suitable boundary conditions to simulate a genuine torus, is investigated in detail. The relaxed state has the same double symmetry as the vessel if, and only if, the prescribed helicity is in an interval that depends on the prescribed fluxes. This interval is determined in the limit of a thin slab

Leybold vacuum handbook

CERN Document Server

Diels, K; Diels, Kurt

1966-01-01

Leybold Vacuum Handbook presents a collection of data sets that are essential for numerical calculation of vacuum plants and vacuum processes. The title first covers vacuum physics, which includes gas kinetics, flow phenomena, vacuum gauges, and vapor removal. Next, the selection presents data on vacuum, high vacuum process technology, and gas desorption and gettering. The text also deals with materials, vapor pressure, boiling and melting points, and gas permeability. The book will be of great interest to engineers and technicians that deals with vacuum related technologies.

Eddy current analysis in fusion devices

International Nuclear Information System (INIS)

Turner, L.R.

1988-06-01

In magnetic fusion devices, particularly tokamaks and reversed field pinch (RFP) experiments, time-varying magnetic fields are in intimate contact with electrically conducting components of the device. Induced currents, fields, forces, and torques result. This note reviews the analysis of eddy current effects in the following systems: Interaction of a tokamak plasma with the eddy currents in the first wall, blanket, and shield (FWBS) systems; Eddy currents in a complex but two-dimensional vacuum vessel, as in TFTR, JET, and JT-60; Eddy currents in the FWBS system of a tokamak reactor, such as NET, FER, or ITER; and Eddy currents in a RFP shell. The cited studies are chosen to be illustrative, rather than exhaustive. 42 refs

LEP vacuum chamber, prototype

CERN Multimedia

CERN PhotoLab

1983-01-01

Final prototype for the LEP vacuum chamber, see 8305170 for more details. Here we see the strips of the NEG pump, providing "distributed pumping". The strips are made from a Zr-Ti-Fe alloy. By passing an electrical current, they were heated to 700 deg C.

Induced current heating probe

International Nuclear Information System (INIS)

Thatcher, G.; Ferguson, B.G.; Winstanley, J.P.

1984-01-01

An induced current heating probe is of thimble form and has an outer conducting sheath and a water flooded flux-generating unit formed from a stack of ferrite rings coaxially disposed in the sheath. The energising coil is made of solid wire which connects at one end with a coaxial water current tube and at the other end with the sheath. The stack of ferrite rings may include non-magnetic insulating rings which help to shape the flux. (author)

Indian Vacuum Society: The Indian Vacuum Society

Science.gov (United States)

Saha, T. K.

2008-03-01

The Indian Vacuum Society (IVS) was established in 1970. It has over 800 members including many from Industry and R & D Institutions spread throughout India. The society has an active chapter at Kolkata. The society was formed with the main aim to promote, encourage and develop the growth of Vacuum Science, Techniques and Applications in India. In order to achieve this aim it has conducted a number of short term courses at graduate and technician levels on vacuum science and technology on topics ranging from low vacuum to ultrahigh vacuum So far it has conducted 39 such courses at different parts of the country and imparted training to more than 1200 persons in the field. Some of these courses were in-plant training courses conducted on the premises of the establishment and designed to take care of the special needs of the establishment. IVS also regularly conducts national and international seminars and symposia on vacuum science and technology with special emphasis on some theme related to applications of vacuum. A large number of delegates from all over India take part in the deliberations of such seminars and symposia and present their work. IVS also arranges technical visits to different industries and research institutes. The society also helped in the UNESCO sponsored post-graduate level courses in vacuum science, technology and applications conducted by Mumbai University. The society has also designed a certificate and diploma course for graduate level students studying vacuum science and technology and has submitted a syllabus to the academic council of the University of Mumbai for their approval, we hope that some colleges affiliated to the university will start this course from the coming academic year. IVS extended its support in standardizing many of the vacuum instruments and played a vital role in helping to set up a Regional Testing Centre along with BARC. As part of the development of vacuum education, the society arranges the participation of

A vacuum-UV laser-induced fluorescence experiment for measurement of rotationally and vibrationally excited H2

International Nuclear Information System (INIS)

Vankan, P.; Heil, S.B.S.; Mazouffre, S.; Engeln, R.; Schram, D.C.; Doebele, H.F.

2004-01-01

An experimental setup is built to detect spatially resolved rovibrationally excited hydrogen molecules via laser-induced fluorescence. To excite the hydrogen molecules, laser radiation is produced in the vacuum UV part of the spectrum. The laser radiation is tunable between 120 nm and 230 nm and has a bandwith of 0.15 cm -1 . The wavelength of the laser radiation is calibrated by simultaneous recording of the two-photon laser induced fluorescence spectrum of nitric oxide. The excited hydrogen populations are calibrated on the basis of coherent anti-Stokes Raman scattering measurements. A population distribution is measured in the shock region of a pure hydrogen plasma expansion. The higher rotational levels (J>5) show overpopulation compared to a Boltzmann distribution determined from the lower rotational levels (J≤5)

Design of the ZTH vacuum liner

International Nuclear Information System (INIS)

Prince, P.P.

1987-01-01

The current status of the ZTH vacuum liner design is covered by this report. ZTH will be the first experiment to be installed in the CPRF (Confinement Physics Research Facility) at the Los Alamos National Laboratory and is scheduled to be operational at 2 MA in 1990 and at the rated current of 4 MA in 1992. The vacuum vessel has a 2.4m major radius and a 40 cm minor radius. The vacuum vessel design features which satisfy the operating parameters are defined. The liner is constructed of Inconel 625 and has a geometry which alternates sections of thin walled bellows with rigid ribs. These composite sections span between pairs of the 16 diagnostic stations to complete the torus. The thin bellows sections maximize the liner toroidal resistance and the ribs provide support and positional accuracy for the armour in relation to the conducting shell. Heat transfer from the vessel is controlled by a blanket wrap of ceramic fiber insulation and the heat flux is dissipated to a water cooling jacket in the conducting shell. 7 figs., 1 tab

An in-vacuum wall current monitor and low cost signal sampling system

International Nuclear Information System (INIS)

Yin, Y.; Rawnsley, W.R.; Mackenzie, G.H.

1993-11-01

The beam bunches extracted from the TRIUMF cyclotron are usually about 4 ns long, contain ∼ 4 x 10 7 protons, and are spaced at 43 ns. A wall current monitor capable of giving the charge distribution within a bunch, on a bunch by bunch basis, has recently been installed together with a sampling system for routine display in the control room. The wall current monitor is enclosed in a vacuum vessel and no ceramic spacer is required. This enhances the response to high frequencies, ferrite rings extend the low frequency response. Bench measurements show a flat response between a few hundred kilohertz and 4.6 GHz. For a permanent display in the control room the oscilloscope will be replaced by a Stanford Research Systems fast sampler module, a scanner module, and an interface module made at TRIUMF. The time to acquire one 10 ns distribution encompassing the beam bunch is 30 ms with a sample width of 100 ps and an average sample spacing of 13 ps. The scan, sample, and retrace signals are buffered carried on 70 m differential lines to the control room. An analog scope in XYZ mode provides a real time display. Signal averaging can be performed by using a digital oscilloscope in YT mode. (author). 6 refs., 2 tabs., 7 figs

Variation of the poloidal field during a disruption and consequences on the vacuum chamber, the poloidal system and the toroidal magnet (Tore II)

International Nuclear Information System (INIS)

Gatineau, F.; Leloup, C.; Pariente, M.

1977-12-01

The currents induced into the vacuum vessel and into the poloidal field coils and the overvoltages on the generators during a plasma current disruption are calculated. The subsequent applied mechanical forces and the poloidal field variations at the toroidal field conductor are deduced. The current decrease rate considered, during a disruption, ranges from d Ip/dt=0.810 9 A/s to 0.410 11 A/s [fr

Design of the ZTH vacuum liner

International Nuclear Information System (INIS)

Prince, P.P.; Dike, R.S.

1987-01-01

The current status of the ZTH vacuum liner design is covered by this report. ZTH will be the first experiment to be installed in the CPRF (Confinement Physics Research Facility) at the Los Alamos National Laboratory and is scheduled to be operational at the rated current of 4 MA in 1992. The vacuum vessel has a 2.4 m major radius and a 40 cm minor radius. Operating parameters which drive the vacuum vessel mechanical design include a 300 C bakeout temperature, an armour support system capable of withstanding 25 kV, a high toroidal resistance, 1250 kPa magnetic loading, a 10 minute cycle time, and high positional accuracy with respect to the conducting shell. The vacuum vessel design features which satisfy the operating parameters are defined. The liner is constructed of Inconel 625 and has a geometry which alternates sections of thin walled bellows with rigid ribs. These composite sections span between pairs of the 16 diagnostic stations to complete the torus. The thin bellows sections maximize the liner toroidal resistance and the ribs provide support and positional accuracy for the armour in relation to the conducting shell. Heat transfer from the vessel is controlled by a blanket wrap of ceramic fiber insulation and the heat flux is dissipated to a water cooling jacket in the conducting shell

Accelerator tube vacuum conditions in the NSF tandem

International Nuclear Information System (INIS)

Groome, A.E.

1979-08-01

The Nuclear Structure Facility currently under construction at the Daresbury Laboratory contains a 30 MV tandem Van de Graaff accelerator with a modular design of accelerator tube. The vacuum system requirements are specified to limit beam loss due to charge-state-changing collisions in the residual gas. This report gives an assessment of some of the parameters affecting the vacuum pressure in an operational machine. Measurements are made of the vacuum conductance and outgassing rate of accelerator tube modules. An assessment is made of the effects of temperature rise, beam mis-steering and the presence of suppression magnets on the ultimate vacuum obtainable. Predictions are made of the pressure profile throughout the machine and consideration is given to operational problems such as tube conditioning and temporary loss of pumping. A schematic diagram of the tandem and its vacuum system is shown. (author)

Metastable electroweak vacuum. Implications for inflation

International Nuclear Information System (INIS)

Lebedev, Oleg; Westphal, Alexander

2012-10-01

Within the Standard Model, the current Higgs and top quark data favor metastability of the electroweak vacuum, although the uncertainties are still significant. The true vacuum is many orders of magnitude deeper than ours and the barrier separating the two is tiny compared to the depth of the well. This raises a cosmological question: how did the Higgs field get trapped in the shallow minimum and why did it stay there during inflation? The Higgs initial conditions before inflation must be fine-tuned to about one part in 10 8 in order for the Higgs field to end up in the right vacuum. In this note, we show that these problems can be resolved if there is a small positive coupling between the Higgs and the inflaton.

Dye laser spectrometer for the analysis of pulsed vacuum arcs

International Nuclear Information System (INIS)

Hargis, P.J. Jr.; Robertson, M.M.

1975-01-01

A pulsed dye laser spectrometer which is used to obtain detailed single shot spectroscopic measurements of the plasma in a pulsed vacuum arc was developed. The capabilities of this spectrometer are indicated by the detection of laser induced fluorescence signals from 10 6 neutral Ti atoms in the plasma of a pulsed vacuum arc with a Ti anode. (U.S.)

MEASUREMENTS AND MODELING OF EDDY CURRENT EFFECTS IN BNL'S AGS BOOSTER

International Nuclear Information System (INIS)

BROWN, K.A.; AHRENS, L.; GARDNER, C.; GLENN, J.W.; HARVEY, M.; MENG, W.; ZENO, K.

2006-01-01

Recent beam experiments at BNL's AGS Booster have enabled us to study in more detail the effects of eddy currents on the lattice structure and our control over the betatron tune. The Booster is capable of operating at ramp rates as high as 9 T/sec. At these ramp rates eddy currents in the vacuum chambers significantly alter the fields and gradients seen by the beam as it is accelerated. The Booster was designed with these effects in mind and to help control the field uniformity and linearity in the Booster Dipoles special vacuum chambers were designed with current windings to negate the affect of the induced eddy currents. In this report results from betatron tune measurements and eddy current simulations will be presented. We will then present results from modeling the accelerator using the results of the magnetic field simulations and compare these to the measurements

Study of the Magnetically Induced QED Birefringence of the Vacuum in experiment OSQAR

CERN Document Server

AUTHOR|(CDS)2083980

Classical electrodynamics in a vacuum is a linear theory and does not foresee photon-photon scattering or other nonlinear effects between electromagnetic fields. In 1936 Euler, Heisenberg and Weisskopf put framework, in the earliest development of quantum electrodynamics (QED), that vacuum can behave as a birefringent medium in the presence of the external transverse magnetic field. This phenomenon is known as Vacuum Magnetic Birefringence (VMB) and it is still challenging for optical metrology since the first calculations in 1970. When linearly polarized light travels through the strong transverse magnetic field in vacuum, the polarization state of the light would change to elliptical. The difference in the refraction indexes of the ordinary and extraordinary ray is directly related to fundamental constants, such as fine structure constant or Compton wavelength. Contributions to VMB could also arise from the existence of light scalar or pseudoscalar particles, such as axions or axions like particles. Axions ...

Giant Persistent Photoconductivity of the WO3 Nanowires in Vacuum Condition

Directory of Open Access Journals (Sweden)

Huang Kai

2011-01-01

Full Text Available Abstract A giant persistent photoconductivity (PPC phenomenon has been observed in vacuum condition based on a single WO3 nanowire and presents some interesting results in the experiments. With the decay time lasting for 1 × 104 s, no obvious current change can be found in vacuum, and a decreasing current can be only observed in air condition. When the WO3 nanowires were coated with 200 nm SiO2 layer, the photoresponse almost disappeared. And the high bias and high electric field effect could not reduce the current in vacuum condition. These results show that the photoconductivity of WO3 nanowires is mainly related to the oxygen adsorption and desorption, and the semiconductor photoconductivity properties are very weak. The giant PPC effect in vacuum condition was caused by the absence of oxygen molecular. And the thermal effect combining with oxygen re-adsorption can reduce the intensity of PPC.

Application of high power microwave vacuum electron devices

International Nuclear Information System (INIS)

Ding Yaogen; Liu Pukun; Zhang Zhaochuan; Wang Yong; Shen Bin

2011-01-01

High power microwave vacuum electron devices can work at high frequency, high peak and average power. They have been widely used in military and civil microwave electron systems, such as radar, communication,countermeasure, TV broadcast, particle accelerators, plasma heating devices of fusion, microwave sensing and microwave heating. In scientific research, high power microwave vacuum electron devices are used mainly on high energy particle accelerator and fusion research. The devices include high peak power klystron, CW and long pulse high power klystron, multi-beam klystron,and high power gyrotron. In national economy, high power microwave vacuum electron devices are used mainly on weather and navigation radar, medical and radiation accelerator, TV broadcast and communication system. The devices include high power pulse and CW klystron, extended interaction klystron, traveling wave tube (TWT), magnetron and induced output tube (IOT). The state of art, common technology problems and trends of high power microwave vacuum electron devices are introduced in this paper. (authors)

How does relativity affect magnetically induced currents?

Science.gov (United States)

Berger, R J F; Repisky, M; Komorovsky, S

2015-09-21

Magnetically induced probability currents in molecules are studied in relativistic theory. Spin-orbit coupling (SOC) enhances the curvature and gives rise to a previously unobserved current cusp in AuH or small bulge-like distortions in HgH2 at the proton positions. The origin of this curvature is magnetically induced spin-density arising from SOC in the relativistic description.

Experiments with vacuum interrupters used for large dc-current interruption

International Nuclear Information System (INIS)

Warren, R.W.

1977-10-01

Vacuum interrupters have been tested in circuits similar to those used in theta-pinch and Tokamak fusion devices. The effects on performance of auxiliary circuit components and axial magnetic fields have been determined, and limits to lifetime caused by mechanical and electrical wear have been measured. Results show that the upper reliable limit of interruption is independent of the auxiliary components but quite dependent on interrupter size and on the axial field

Vacuum system design for the PEP-II B Factory High-Energy Ring

International Nuclear Information System (INIS)

Perkins, C.; Bostic, D.; Daly, E.

1994-06-01

The design of the vacuum system for the PEP-II B Factory High-Energy Ring is reviewed. The thermal design and vacuum requirements are particularly challenging in PEP-II due to high stored beam currents up to 3.0 amps in 1658 bunches. The vacuum chambers for the HER arcs are fabricated by electron beam welding extruded copper sections up to 6 m long. Design of these chambers and the vacuum PumPing configuration is described with results from vacuum and thermal analyses

Simulation of VDE under intervention of vertical stability control and vertical electromagnetic force on the ITER vacuum vessel

International Nuclear Information System (INIS)

Miyamoto, S.; Sugihara, M.; Shinya, K.; Nakamura, Y.; Toshimitsu, S.; Lukash, V.E.; Khayrutdinov, R.R.; Sugie, T.; Kusama, Y.; Yoshino, R.

2012-01-01

Highlights: ► Taking account of intervention of VS control, VDE simulations were carried out. ► Malfunctioning of VS circuit (positive feedback) enhances the vertical force. ► The worst case was explored for vertical force on the ITER vacuum vessel. ► We confirmed the force is still within the design margin even if the worst case. - Abstract: Vertical displacement events (VDEs) and disruptions usually take place under intervention of vertical stability (VS) control and the vertical electromagnetic force induced on vacuum vessels is potentially influenced. This paper presents assessment of the force that arises from the VS control in ITER VDEs using a numerical simulation code DINA. The focus is on a possible malfunctioning of the ex-vessel VS control circuit: radial magnetic field is unintentionally applied to the direction of enhancing the vertical displacement further. Since this type of failure usually causes the largest forces (or halo currents) observed in the present experiments, this situation must be properly accommodated in the design of the ITER vacuum vessel. DINA analysis shows that although the ex-vessel VS control modifies radial field, it does not affect plasma motion and current quench behavior including halo current generation because the vacuum vessel shields the field created by the ex-vessel coils. Nevertheless, the VS control modifies the force on the vessel by directly acting on the eddy current carried by the conducting structures of the vessel. Although the worst case was explored in a range of plasma inductance and pattern of VS control in combination with the in-vessel VS control circuit, the result confirmed that the force is still within the design margin.

Direct-current cathodic vacuum arc system with magnetic-field mechanism for plasma stabilization.

Science.gov (United States)

Zhang, H-S; Komvopoulos, K

2008-07-01

Filtered cathodic vacuum arc (FCVA) deposition is characterized by plasma beam directionality, plasma energy adjustment via substrate biasing, macroparticle filtering, and independent substrate temperature control. Between the two modes of FCVA deposition, namely, direct current (dc) and pulsed arc, the dc mode yields higher deposition rates than the pulsed mode. However, maintaining the dc arc discharge is challenging because of its inherent plasma instabilities. A system generating a special configuration of magnetic field that stabilizes the dc arc discharge during film deposition is presented. This magnetic field is also part of the out-of-plane magnetic filter used to focus the plasma beam and prevent macroparticle film contamination. The efficiency of the plasma-stabilizing magnetic-field mechanism is demonstrated by the deposition of amorphous carbon (a-C) films exhibiting significantly high hardness and tetrahedral carbon hybridization (sp3) contents higher than 70%. Such high-quality films cannot be produced by dc arc deposition without the plasma-stabilizing mechanism presented in this study.

Direct-current cathodic vacuum arc system with magnetic-field mechanism for plasma stabilization

International Nuclear Information System (INIS)

Zhang, H.-S.; Komvopoulos, K.

2008-01-01

Filtered cathodic vacuum arc (FCVA) deposition is characterized by plasma beam directionality, plasma energy adjustment via substrate biasing, macroparticle filtering, and independent substrate temperature control. Between the two modes of FCVA deposition, namely, direct current (dc) and pulsed arc, the dc mode yields higher deposition rates than the pulsed mode. However, maintaining the dc arc discharge is challenging because of its inherent plasma instabilities. A system generating a special configuration of magnetic field that stabilizes the dc arc discharge during film deposition is presented. This magnetic field is also part of the out-of-plane magnetic filter used to focus the plasma beam and prevent macroparticle film contamination. The efficiency of the plasma-stabilizing magnetic-field mechanism is demonstrated by the deposition of amorphous carbon (a-C) films exhibiting significantly high hardness and tetrahedral carbon hybridization (sp 3 ) contents higher than 70%. Such high-quality films cannot be produced by dc arc deposition without the plasma-stabilizing mechanism presented in this study

Discharge modes at the anode of a vacuum arc

International Nuclear Information System (INIS)

Miller, H.C.

1982-01-01

The two most common anode modes in a vacuum arc are the low current mode, where the anode is basically inert; and the high current mode with a fully developed anode spot. This anode spot is very bright, has a temperature near the boiling point of the anode material, and is a copious source of vapor and energetic ions. However, other anode modes can exist. A low current vacuum arc with electrodes of readily sputterable material will emit a flux of sputtered atoms from the anode. An intermediate currents an anode footpoint can form. This footpoint is luminous, but much cooler than a true anode spot. Finally, a high current mode can exist where several small anode spots are present instead of a single large anode spot

Can vacuum decay in our universe?

International Nuclear Information System (INIS)

Wang Peng; Meng Xinhe

2005-01-01

We take a phenomenological approach to the study of the cosmological evolution of decaying vacuum cosmology (Λ(t)CDM) based on a simple assumption about the form of the modified matter expansion rate. In this framework, almost all current vacuum decaying models can be unified in a simple manner. We argue that the idea of letting vacuum decay to resolve the fine-tuning problem is inconsistent with cosmological observations. We also discuss some issues in confronting Λ(t)CDM with observation. Using the effective equation-of-state formalism, we indicate that Λ(t)CDM is a possible candidate for phantom cosmology. Moreover, confronted with a possible problem with the effective equation-of-state formalism, we construct the effective dark energy density. Finally, we discuss the evolution of linear perturbation

Metastable electroweak vacuum. Implications for inflation

Energy Technology Data Exchange (ETDEWEB)

Lebedev, Oleg; Westphal, Alexander [DESY Theory Group, Hamburg (Germany)

2012-10-15

Within the Standard Model, the current Higgs and top quark data favor metastability of the electroweak vacuum, although the uncertainties are still significant. The true vacuum is many orders of magnitude deeper than ours and the barrier separating the two is tiny compared to the depth of the well. This raises a cosmological question: how did the Higgs field get trapped in the shallow minimum and why did it stay there during inflation? The Higgs initial conditions before inflation must be fine-tuned to about one part in 10{sup 8} in order for the Higgs field to end up in the right vacuum. In this note, we show that these problems can be resolved if there is a small positive coupling between the Higgs and the inflaton.

High-energy limit of collision-induced false vacuum decay

Energy Technology Data Exchange (ETDEWEB)

Demidov, Sergei; Levkov, Dmitry [Institute for Nuclear Research of the Russian Academy of Sciences,60-th October Anniversary Prospect 7a, Moscow, 117312 (Russian Federation)

2015-06-17

We develop a consistent semiclassical description of field-theoretic collision-induced tunneling at arbitrary high collision energies. As a playground we consider a (1+1)-dimensional false vacuum decay initiated by a collision of N particles at energy E, paying special attention to the realistic case of N=2 particles. We demonstrate that the cross section of this process is exponentially suppressed at all energies. Moreover, the respective suppressesion exponent F{sub N}(E) exhibits a specific behavior which is significant for our semiclassical method and assumed to be general: it decreases with energy, reaches absolute minimum F=F{sub min}(N) at a certain threshold energy E=E{sub rt}(N), and stays constant at higher energies. We show that the minimal suppression F{sub min}(N) and threshold energy can be evaluated using a special class of semiclassical solutions which describe exponentially suppressed transitions but nevertheless evolve in real time. Importantly, we argue that the cross section at energies above E{sub rt}(N) is computed perturbatively in the background of the latter solutions, and the terms of this perturbative expansion stay bounded in the infinite-energy limit. Transitions in the high-energy regime proceed via emission of many soft quanta with total energy E{sub rt}; the energy excess E−E{sub rt} remains in the colliding particles till the end of the process.

Using laser-induced breakdown spectroscopy on vacuum alloys-production process for elements concentration analysis

Science.gov (United States)

Zhao, Tianzhuo; Fan, Zhongwei; Lian, Fuqiang; Liu, Yang; Lin, Weiran; Mo, Zeqiang; Nie, Shuzhen; Wang, Pu; Xiao, Hong; Li, Xin; Zhong, Qixiu; Zhang, Hongbo

2017-11-01

Laser-induced breakdown spectroscopy (LIBS) utilizing an echelle spectrograph-ICCD system is employed for on-line analysis of elements concentration in a vacuum induction melting workshop. Active temperature stabilization of echelle spectrometer is implemented specially for industrial environment applications. The measurement precision is further improved by monitoring laser parameters, such as pulse energy, spatial and temporal profiles, in real time, and post-selecting laser pulses with specific pulse energies. Experimental results show that major components of nickel-based alloys are stable, and can be well detected. By using internal standard method, calibration curves for chromium and aluminum are obtained for quantitative determination, with determination coefficient (relative standard deviation) to be 0.9559 (< 2.2%) and 0.9723 (< 2.8%), respectively.

Heavy-heavy and heavy-light quarks interactions generated by QCD vacuum

Directory of Open Access Journals (Sweden)

Musakhanov Mirzayusuf

2017-01-01

Full Text Available The QCD vacuum is populated by instantons that correspond to the tunneling processes in the vacuum. This mechanism creates the strong vacuum gluon fields. As result, the QCD vacuum instantons induce very strong interactions between light quarks, initially almost massless. Such a strong interactions bring a large dynamical mass M of the light quarks and bound them to produce almost massless pions in accordance with the spontaneous breaking of the chiral symmetry (SBCS. On the other hand, the QCD vacuum instantons also interact with heavy quarks and responsible for the generation of the heavy-heavy and heavy-light quarks interactions, with a traces of the SBCS. If we take the average instanton size ρ¯=0.33$\\bar \\rho = 0.33$ fm, and the average inter-instanton distance R¯=1$\\bar R = 1$ fm we obtain the dynamical light quark mass to be M = 365 MeV and the instanton media contribution to the heavy quark mass ΔM=70 MeV. These factors define the coupling between heavy-light and heavy-heavy quarks induced by the QCD vacuum instantons. We consider first the instanton effects on the heavy-heavy quarks potential, including its spin-dependent part. We also discuss those effects on the masses of the charmonia and their hyperfine mass splittings. At the second part we discuss the interaction between a heavy and light quarks generated by instantons and it’s effects.

Current-induced switching in a magnetic insulator

Science.gov (United States)

Avci, Can Onur; Quindeau, Andy; Pai, Chi-Feng; Mann, Maxwell; Caretta, Lucas; Tang, Astera S.; Onbasli, Mehmet C.; Ross, Caroline A.; Beach, Geoffrey S. D.

2017-03-01

The spin Hall effect in heavy metals converts charge current into pure spin current, which can be injected into an adjacent ferromagnet to exert a torque. This spin-orbit torque (SOT) has been widely used to manipulate the magnetization in metallic ferromagnets. In the case of magnetic insulators (MIs), although charge currents cannot flow, spin currents can propagate, but current-induced control of the magnetization in a MI has so far remained elusive. Here we demonstrate spin-current-induced switching of a perpendicularly magnetized thulium iron garnet film driven by charge current in a Pt overlayer. We estimate a relatively large spin-mixing conductance and damping-like SOT through spin Hall magnetoresistance and harmonic Hall measurements, respectively, indicating considerable spin transparency at the Pt/MI interface. We show that spin currents injected across this interface lead to deterministic magnetization reversal at low current densities, paving the road towards ultralow-dissipation spintronic devices based on MIs.

Vacuum mechatronics

Science.gov (United States)

Hackwood, Susan; Belinski, Steven E.; Beni, Gerardo

1989-01-01

The discipline of vacuum mechatronics is defined as the design and development of vacuum-compatible computer-controlled mechanisms for manipulating, sensing and testing in a vacuum environment. The importance of vacuum mechatronics is growing with an increased application of vacuum in space studies and in manufacturing for material processing, medicine, microelectronics, emission studies, lyophylisation, freeze drying and packaging. The quickly developing field of vacuum mechatronics will also be the driving force for the realization of an advanced era of totally enclosed clean manufacturing cells. High technology manufacturing has increasingly demanding requirements for precision manipulation, in situ process monitoring and contamination-free environments. To remove the contamination problems associated with human workers, the tendency in many manufacturing processes is to move towards total automation. This will become a requirement in the near future for e.g., microelectronics manufacturing. Automation in ultra-clean manufacturing environments is evolving into the concept of self-contained and fully enclosed manufacturing. A Self Contained Automated Robotic Factory (SCARF) is being developed as a flexible research facility for totally enclosed manufacturing. The construction and successful operation of a SCARF will provide a novel, flexible, self-contained, clean, vacuum manufacturing environment. SCARF also requires very high reliability and intelligent control. The trends in vacuum mechatronics and some of the key research issues are reviewed.

Current identification in vacuum circuit breakers as a least squares problem*

Directory of Open Access Journals (Sweden)

Ghezzi Luca

2013-01-01

Full Text Available In this work, a magnetostatic inverse problem is solved, in order to reconstruct the electric current distribution inside high voltage, vacuum circuit breakers from measurements of the outside magnetic field. The (rectangular final algebraic linear system is solved in the least square sense, by involving a regularized singular value decomposition of the system matrix. An approximated distribution of the electric current is thus returned, without the theoretical problem which is encountered with optical methods of matching light to temperature and finally to current density. The feasibility is justified from the computational point of view as the (industrial goal is to evaluate whether, or to what extent in terms of accuracy, a given experimental set-up (number and noise level of sensors is adequate to work as a “magnetic camera” for a given circuit breaker. Dans cet article, on résout un problème inverse magnétostatique pour déterminer la distribution du courant électrique dans le vide d’un disjoncteur à haute tension à partir des mesures du champ magnétique extérieur. Le système algébrique (rectangulaire final est résolu au sens des moindres carrés en faisant appel à une décomposition en valeurs singulières regularisée de la matrice du système. On obtient ainsi une approximation de la distribution du courant électrique sans le problème théorique propre des méthodes optiques qui est celui de relier la lumière à la température et donc à la densité du courant. La faisabilité est justifiée d’un point de vue numérique car le but (industriel est d’évaluer si, ou à quelle précision, un dispositif expérimental donné (nombre et seuil limite de bruit des senseurs peut travailler comme une “caméra magnétique” pour un certain disjoncteur.

Effects of the fermionic vacuum polarization in QED

Energy Technology Data Exchange (ETDEWEB)

Medeiros, M.F.X.P.; Barone, F.A. [IFQ-Universidade Federal de Itajuba, Itajuba, MG (Brazil); Barone, F.E.

2018-01-15

Some effects of vacuum polarization in QED due to the presence of field sources are investigated. We focus on effects with no counter-part in Maxwell electrodynamics. The Uehling interaction energy between two stationary point-like charges is calculated exactly in terms of Meijer-G functions. Effects induced on a hydrogen atom by the vacuum polarization in the vicinity of a Dirac string are considered. We also calculate the interaction between two parallel Dirac strings and corrections to the energy levels of a quantum particle constrained to move on a ring circumventing a solenoid. (orig.)

A transparent vacuum window for high-intensity pulsed beams

CERN Document Server

Monteil, M; Veness, R

2011-01-01

The HiRadMat (High-Radiation to Materials) facility Ill will allow testing of accelerator components, in particular those of the Large Hadron Collider (LHC) at CERN, under the impact of high-intensity pulsed beams. To reach this intensity range, the beam will be focused on a focal point where the target to be tested is located. A 60 mm aperture vacuum window will separate the vacuum of the beam line which is kept under high vacuum 10(-8) mbar, from the test area which is at atmospheric pressure. This window has to resist collapse due to beam passage. The high-intensity of the beam means that typical materials used for standard vacuum windows (such as stainless steel, aluminium and titanium alloy) cannot endure the energy deposition induced by the beam passage. Therefore, a vacuum window has been designed to maintain the differential pressure whilst resisting collapse due to the beam impact on the window. In this paper, we will present calculations of the energy transfer from beam to window, the design of the ...

Multiple (Two) Met Bel 601 In Series Ultimate Vacuum Testing

Energy Technology Data Exchange (ETDEWEB)

Restivo, M. [Savannah River Site (SRS), Aiken, SC (United States). Savannah River National Lab. (SRNL)

2016-09-30

SRNL Environmental and Chemical Process Technology (E&CPT) was requested to perform testing of vacuum pumps per a verbal request from the Customer, SRNL Hydrogen Processing Technology. Tritium Operations is currently having difficulties procuring the Normetex™® Model 15 m³/hr (9 CFM) vacuum pump (formerly Normetex Pompes, now Eumeca_SARL). One possible solution proposed by Hydrogen Processing Technology personnel is to use two Senior Aerospace Metal Bellows MB-601 vacuum pumps piped with the heads in series, and the pumps in series (Figure 1 below). This memorandum documents the ultimate vacuum testing that was performed to determine if this concept was a viable alternate vacuum pump strategy. This testing dovetails with previous pump evaluations documented in references 1 and 2.

Dark Current and Multipacting in the Photocathode RF Guns at PITZ

CERN Document Server

Hui-Han, Jang; Flöttmann, Klaus; Grabosch, H J; Hartrott, Michael; Krasilnikov, Mikhail; Michelato, Paolo; Miltchev, Velizar; Monaco, Laura; Oppelt, Anne; Petrosyan, Bagrat; Riemann, S; Roensch, Juliane; Schreiber, Siegfried; Sertore, Daniele; Staykov, Lazar; Stephan, Frank

2005-01-01

For photocathode rf guns, the amount of dark current depends on the cavity surface and the photocathodes. Smooth conditioning reduces the amount of dark current. Mechanical damages of the cathodes induce high dark current and chemical pollution changes emission properties of the cathode. Multipacting in the gun cavity changes the surface status of the cathodes and sometimes makes the gun operation impossible due to vacuum interlocks. In this paper, dark current and multipacting features of the rf gun are presented including experimental and simulation studies.

Evaluating operational vacuum for landfill biogas extraction.

Science.gov (United States)

Fabbricino, Massimiliano

2007-01-01

This manuscript proposes a practical methodology for estimating the operational vacuum for landfill biogas extraction from municipal landfills. The procedure is based on two sub-models which simulate landfill gas production from organic waste decomposition and distribution of gas pressure and gas movement induced by suction at a blower station. The two models are coupled in a single mass balance equation, obtaining a relationship between the operational vacuum and the amount of landfill gas that can be extracted from an assigned system of vertical wells. To better illustrate the procedure, it is applied to a case study, where a good agreement between simulated and measured data, within +/- 30%, is obtained.

Electrical strength of vacuum gap at repetitive breakdown

International Nuclear Information System (INIS)

Dubinin, N.P.; Chistyakov, N.P.

1983-01-01

The investigation of repetitive pulse breakdown of vacuum space, which electrodes have been subjected to various treatment in vacuum and inert gas, is carried out. In case of electrode warm-up in vacuum up to 400 deg C as well as electronic heating up to 900 deg C the voltage in case of repetitive breakdown hasncreased approximately twice and in case of a through treatment, which is accomplished by a high-current glow discharge in inert gas, the maximum high voltage in case of the first breakdown at repetitive breakdown has decreased by 30...40%, remaining 2-3 times higher than in the first case

Current-induced atomic dynamics, instabilities, and Raman signals

DEFF Research Database (Denmark)

Lu, Jing Tao; Brandbyge, Mads; Hedegard, Per

2012-01-01

We derive and employ a semiclassical Langevin equation obtained from path integrals to describe the ionic dynamics of a molecular junction in the presence of electrical current. The electronic environment serves as an effective nonequilibrium bath. The bath results in random forces describing Joule...... heating, current-induced forces including the nonconservative wind force, dissipative frictional forces, and an effective Lorentz-type force due to the Berry phase of the nonequilibrium electrons. Using a generic two-level molecular model, we highlight the importance of both current-induced forces...... and Joule heating for the stability of the system. We compare the impact of the different forces, and the wide-band approximation for the electronic structure on our result. We examine the current-induced instabilities (excitation of runaway "waterwheel" modes) and investigate the signature...

Electromagnetic forces on a metallic Tokamak vacuum vessel following a disruptive instability

International Nuclear Information System (INIS)

Eckhartt, D.

1979-04-01

During a 'hard' disruptive instability of a Tokamak plasma the current-carrying plasma is lost within a very short time, typically few milliseconds. If the plasma is contained in a metallic vacuum vessel, electric currents are set up in the vessel following the disappearance of the plasma current. These vessel currents together with the magnetic fields intersecting the vessel generate electromagnetic forces which appear as mechanical loads on the vessel. In the following note it is assumed that the vacuum vessel is surrounded by an 'outer equivalent' or 'flux-conserving' shell having a characteristic time of magnetic field penetration which is long compared to the time of existence of the vessel currents. This property defines the distribution of vessel current densities (and hence the load distribution) without referring to the exact mechanism or time sequence of events by which the plasma current is lost. Numerical examples of the electromagnetic force distribution from this model refer to parameters of the JET-device with the simplifying assumption of circular cross-sections for plasma current, vacuum vessel, and outer equivalent shell. (orig.)

Vacuum system of SST-1 Tokamak

International Nuclear Information System (INIS)

Khan, Ziauddin; Pathan, Firozkhan; George, Siju; Semwal, Pratibha; Dhanani, Kalpesh; Paravastu, Yuvakiran; Thankey, Prashant; Ramesh, Gattu; Himabindu, Manthena; Pradhan, Subrata

2013-01-01

�C deviation was achieved with a net mass flow rate of 0.8 kg/s at 1.5 bar gauge inlet pressure and supply temperature of 230 °C at the heater end. Also during gas feed system installation, the pressure inside the VV was raised from 3.01 × 10 −5 mbar to 1.72 × 10 −4 mbar by triggering a pulse of lower amplitude of 25 voltage direct current (VDC) for 100 s to piezoelectric valve. This paper describes in detail the design and implementation of the various vacuum subsystems including relevant experimental results

Molecular weight changes induced in an anionic polydimethylsiloxane by gamma irradiation in vacuum

International Nuclear Information System (INIS)

Satti, Angel J.; Andreucetti, Noemi A.; Ciolino, Andres E.; Vitale, Cristian; Sarmoria, Claudia; Valles, Enrique M.

2010-01-01

An anionic almost monodisperse linear polydimethylsiloxane (PDMS) was subjected to gamma irradiation under vacuum at room temperature. The molecular weight changes induced by the radiation process have been investigated using size exclusion chromatography (SEC) with refraction index (RI) and multi angle laser light scattering (MALLS) detectors, to obtain the number and weight average molecular weights of the irradiated samples. The analysis of the data indicates that crosslinking reactions predominated over scission reactions. The results obtained by an SEC-RI have confirmed the presence of small, but measurable amounts of scission. A previously developed mathematical model of the irradiation process that accounts for simultaneous scission and crosslinking and allows for both H- and Y-crosslinks, fitted well the measured molecular weight data. This prediction is in accordance with the experimental data obtained by 29 Si-Nuclear Magnetic Resonance spectroscopy (NMR) and previously reported data for commercial linear PDMS ().

The vacuum system for the PEP II high energy ring straight sections

International Nuclear Information System (INIS)

Wienands, U.; Daly, E.; Heifets, S.A.; Kulikov, A.; Kurita, N.; Nordby, M.; Perkins, C.; Reuter, E.; Seeman, J.T.; Belser, F.C.; Berg, J.; Holdener, F.R.; Kerns, J.A.; McDaniel, M.R.; Stoeffl, W.

1995-01-01

The six straight sections of the PEP II High Energy Ring (HER) serve various functions: lattice tuning, beam injection and abort, providing space for rf cavities, longitudinal and transverse feedback, beam diagnostics and the interaction point. A stainless steel vacuum system has been designed; prototypes are currently being built. Cooling is required due to radiation coming from the last arc dipole and resistive losses in the vacuum chamber. Although the nominal beam current of the HER is 1 A the vacuum system is designed for 3 A to provide margin and an upgrade path. 5 refs., 7 figs

HIGH PRODUCTIVITY VACUUM BLASTING SYSTEM

International Nuclear Information System (INIS)

McPhee, William S.

2001-01-01

The Department of Energy (DOE) needs improved technologies to decontaminate large areas of both concrete and steel surfaces. The technology should have high operational efficiency, minimize exposures to workers, and produce low levels of secondary waste. In order to meet the DOE's needs, an applied research and development project for the improvement of a current decontamination technology, Vacuum Blasting, is proposed. The objective of this project is to improve the productivity and lower the expense of the existing vacuum blasting technology which has been widely used in DOE sites for removing radioactive contamination, PCBs, and lead-based paint. The proposed work would increase the productivity rate and provide safe and cost-effective decontamination of the DOE sites

Influences of arc current on composition and properties of MgO thin films prepared by cathodic vacuum arc deposition

International Nuclear Information System (INIS)

Zhu Daoyun; Zheng Changxi; Wang Mingdong; Liu Yi; Chen Dihu; He Zhenhui; Wen Lishi; Cheung, W.Y.

2010-01-01

MgO thin films with high optical transmittances (more than 90%) were prepared by cathodic vacuum arc deposition technique. With the increase of arc current from 40 to 80 A, the deposition pressure decreases and the film thickness increases; the atomic ratio of Mg/O in MgO thin films (obtained by RBS) increases from 0.97 to 1.17, giving that deposited at 50 A most close to the stoichiometric composition of the bulk MgO; the grains of MgO thin films grow gradually as shown in SEM images. XRD patterns show that MgO (1 1 0) orientation is predominant for films prepared at the arc currents ranged from 50 to 70 A. The MgO (1 0 0) orientation is much enhanced and comparable to that of MgO (1 1 0) for films prepared at the arc current of 80 A. The secondary electron emission coefficient of MgO thin film increases with arc current ranged from 50 to 70 A.

Vacuum system design and performance for the Daresbury HBL

International Nuclear Information System (INIS)

Reid, R.J.

1988-01-01

This paper reports on the vacuum performance of an electron storage ring dedicated to the production of synchrotron radiation which is characterized in terms of the single parameter electron beam lifetime at the working current of the machine. The Daresbury SRS had performed satisfactorily in this respect over much of its working life, with lifetimes in excess of 10 hours at 300 mA stored current at a beam energy of 2 GeV. When the decision was taken to upgrade the performance of the machine by increasing the source brilliance, it was important that this performance should continue. However, it was clear that apertures - and hence gas flow conductances - in some of the new vacuum chambers were very restricted. Thus it was by no means obvious that the requisite vacuum levels (approx. 10 -7 Pascal) could be obtained given the engineering constraints on the possible location and physical size of suitable vacuum pumps. Extensive and detailed calculations were therefore carried out using a finite-element type of analysis to compute pressure profiles in the proposed machine, with the vacuum pumps being treated as semi-free parameters. A suitable scheme was evolved, and has proved satisfactory, with beam lifetimes of 24 hours at 200 mA stored beam at 2 GeV being regularly achieved. These lifetimes are in excess of the anticipated values, and this is discussed

Note: Ultra-low birefringence dodecagonal vacuum glass cell

Energy Technology Data Exchange (ETDEWEB)

Brakhane, Stefan, E-mail: brakhane@iap.uni-bonn.de; Alt, Wolfgang; Meschede, Dieter; Robens, Carsten; Moon, Geol; Alberti, Andrea [Institut für Angewandte Physik, Universität Bonn, Wegelerstr. 8, D-53115 Bonn (Germany)

2015-12-15

We report on an ultra-low birefringence dodecagonal glass cell for ultra-high vacuum applications. The epoxy-bonded trapezoidal windows of the cell are made of SF57 glass, which exhibits a very low stress-induced birefringence. We characterize the birefringence Δn of each window with the cell under vacuum conditions, obtaining values around 10{sup −8}. After baking the cell at 150 °C, we reach a pressure below 10{sup −10} mbar. In addition, each window is antireflection coated on both sides, which is highly desirable for quantum optics experiments and precision measurements.

MEA vacuum system

International Nuclear Information System (INIS)

Stroo, R.; Schwebke, H.; Heine, E.

1984-01-01

This report describes construction and operation of the MEA vacuum system of NIKHEF (Netherlands). First, the klystron vacuum system, beam transport system, diode pump and a triode pump are described. Next, the isolation valve and the fast valves of the vacuum system are considered. Measuring instruments, vacuum system commands and messages of failures are treated in the last chapter. (G.J.P.)

Neutron induced current pulses in fission chambers

International Nuclear Information System (INIS)

Taboas, A.L.; Buck, W.L.

1978-01-01

The mechanism of neutron induced current pulse generation in fission chambers is discussed. By application of the calculated detector transfer function to proposed detector current pulse shapes, and by comparison with actually observed detector output voltage pulses, a credible, semi-empirical, trapezoidal pulse shape of chamber current is obtained

Scaling of rotation and isotope separation in a vacuum-arc centrifuge

International Nuclear Information System (INIS)

Prasad, R.R.; Krishnan, M.

1987-01-01

Scaling is described of rotation, plasma column size and separation in a vacuum-arc centrifuge. The vacuum-arc centrifuge is a magnetized, fulled ionized, quasineutral column of plasma. The source of plasma is a vacuum-arc discharge between a negatively biased cathode and a grounded mesh anode. Rigid-body rotation, induced by the J x B force, causes radial, centrifugal separation of isotopes in the plasma column. Salient features of a fluid model that provides an understanding of rotation and the concomitant isotope separation in the vacuum-arc centrifuge are described. Scaling of rotation and plasma column size is found be consistent with the model. Measurements of isotope separation, also found to agree with the predictions of the model, are presented. Results of a parametric analysis of isotope separation in such a vacuum-arc centrifuge, using the fluid model and the observed scaling laws, are described. An analysis of the energy cost of separation of the vacuum-arc centrifuge shows that it typically requires only 70 keV/separated atom. (orig.)

Early counterpulse technique applied to vacuum interrupters

International Nuclear Information System (INIS)

Warren, R.W.

1979-01-01

Interruption of dc currents using counterpulse techniques is investigated with vacuum interrupters and a novel approach in which the counterpulse is applied before contact separation. Important increases have been achieved in this way in the maximum interruptible current and large reductions in contact erosion. The factors establishing these new limits are presented and ways are discussed to make further improvements to the maximum interruptible current

Insulation vacuum and beam vacuum overpressure release

CERN Document Server

Parma, V

2009-01-01

There is evidence that the incident of 19th September caused a high pressure build-up inside the cryostat insulation vacuum which the existing overpressure devices could not contain. As a result, high longitudinal forces acting on the insulation vacuum barriers developed and broke the floor and the floor fixations of the SSS with vacuum barriers. The consequent large longitudinal displacements of the SSS damaged chains of adjacent dipole cryo-magnets. Estimates of the helium mass flow and the pressure build- up experienced in the incident are presented together with the pressure build-up for an even more hazardous event, the Maximum Credible Incident (MCI). The strategy of limiting the maximum pressure by the installation of addition pressure relieve devices is presented and discussed. Both beam vacuum lines were ruptured during the incident in sector 3-4 giving rise to both mechanical damage and pollution of the system. The sequence, causes and effects of this damage will be briefly reviewed. We will then an...

On Current Drive and Wave Induced Bootstrap Current in Toroidal Plasmas

International Nuclear Information System (INIS)

Hellsten, T.; Johnson, T.

2008-01-01

A comprehensive treatment of wave-particle interactions in toroidal plasmas including collisional relaxation, applicable to heating or anomalous wave induced transport, has been obtained by using Monte Carlo operators satisfying quasi-neutrality. This approach enables a self-consistent treatment of wave-particle interactions applicable to the banana regime in the neoclassical theory. It allows an extension into a regime with large temperature and density gradients, losses and transport of particles by wave-particle interactions making the method applicable to transport barriers. It is found that at large gradients the relationship between radial electric field, parallel velocity, temperature and density gradient in the neoclassical theory is modified such that coefficient in front of the logarithmic ion temperature gradient, which in the standard neoclassical theory is small and counteracts the electric field caused by the density gradient, now changes sign and contributes to the built up of the radial electric field. The possibility to drive current by absorbing the waves on trapped particles has been studied and how the wave-particle interactions affect the bootstrap current. Two new current drive mechanisms are studied: current drive by wave induced bootstrap current and selective detrapping into passing orbits by directed waves.

Vacuum-induced stationary entanglement in radiatively coupled three-level atoms

International Nuclear Information System (INIS)

Derkacz, Lukasz; Jakobczyk, Lech

2008-01-01

We consider a pair of three-level atoms interacting with a common vacuum and analyse the process of entanglement production due to spontaneous emission. We show that in the case of closely separated atoms collective damping can generate robust entanglement of the asymptotic states

Vacuum-induced stationary entanglement in radiatively coupled three-level atoms

Energy Technology Data Exchange (ETDEWEB)

Derkacz, Lukasz; Jakobczyk, Lech [Institute of Theoretical Physics, University of Wroclaw, Plac Maxa Borna 9, 50-204 Wroclaw (Poland)], E-mail: ljak@ift.uni.wroc.pl

2008-05-23

We consider a pair of three-level atoms interacting with a common vacuum and analyse the process of entanglement production due to spontaneous emission. We show that in the case of closely separated atoms collective damping can generate robust entanglement of the asymptotic states.

Perturbation-polynomial expansion formulation of 3-D eddy current problems

International Nuclear Information System (INIS)

Yeh, H.T.

1977-01-01

A pulsed magnetic field is required in Tokamak fusion machines. Eddy currents produced by the pulsed field may produce undesirable effects, e.g., in the mechanical loading of the vacuum vessel, heating in the magnet and structure, and field ripple in the plasma region. A method has been developed earlier to calculate the eddy current produced in a thin object by the linear ramping of a magnetic dipole. We report here extension of the method to calculate the eddy current induced in three-dimensional objects and by pulse coils of general shape. Examples are given

Ultra-high vacuum system of the Brookhaven National Synchrotron Light Source

Energy Technology Data Exchange (ETDEWEB)

Foerster, C.L.

1995-12-31

The rings of the National Synchrotron Light Source (NSLS) have been supplying light to numerous users for approximately a decade and we recently enjoyed a fully conditioned machine vacuum at design currents. A brief description of the X-Ray storage ring, the VUV storage ring and their current supply is given along with some of their features. The ultra-high vacuum system employed for the storage rings and their advantages for the necessary stored beam environments are discussed including, a brief history of time. After several hundred amp hours of stored beam current operation, very little improvement in machine performance was seen due to conditioning. Sections of the rings were vented, to dry nitrogen and replacement components were pre-baked and pre-argon glow conditioned prior to installation. Very little machine conditioning was needed to return to operation after recovering vacuum due to well established conditioning procedures. All straight sections in the X-Ray ring and the VUV ring have been filled with various insertion devices and most are fully operational. Each storage ring has a computer controlled total pressure and partial pressure monitoring system for the ring and its beam ports, to insure good vacuum.

Vacuum Simulations in High Energy Accelerators and Distribution Properties of Continuous and Discrete Particle Motions

OpenAIRE

Aichinger, Ida; Larcher, Gerhard; Kersevan, Roberto

2017-01-01

The underlying thesis on mathematical simulation methods in application and theory is structured into three parts. The first part sets up a mathematical model capable of predicting the performance and operation of an accelerator’s vacuum system based on analytical methods. A coupled species-balance equation system describes the distribution of the gas dynamics in an ultra-high vacuum system considering impacts of conductance limitations, beam induced effects (ion-, electron-, and photon-induc...

Vacuum system of SST-1 Tokamak

Energy Technology Data Exchange (ETDEWEB)

Khan, Ziauddin, E-mail: ziauddin@ipr.res.in [Institute for Plasma Research, Near Indira Bridge, Bhat, Gandhinagar 382 428 (India); Pathan, Firozkhan; George, Siju; Semwal, Pratibha; Dhanani, Kalpesh; Paravastu, Yuvakiran; Thankey, Prashant; Ramesh, Gattu; Himabindu, Manthena; Pradhan, Subrata [Institute for Plasma Research, Near Indira Bridge, Bhat, Gandhinagar 382 428 (India)

2013-10-15

vacuum vessel up to 110 °C with ±10 °C deviation was achieved with a net mass flow rate of 0.8 kg/s at 1.5 bar gauge inlet pressure and supply temperature of 230 °C at the heater end. Also during gas feed system installation, the pressure inside the VV was raised from 3.01 × 10{sup −5} mbar to 1.72 × 10{sup −4} mbar by triggering a pulse of lower amplitude of 25 voltage direct current (VDC) for 100 s to piezoelectric valve. This paper describes in detail the design and implementation of the various vacuum subsystems including relevant experimental results.

Structural Analysis of the NCSX Vacuum Vessel

International Nuclear Information System (INIS)

Fred Dahlgren; Art Brooks; Paul Goranson; Mike Cole; Peter Titus

2004-01-01

The NCSX (National Compact Stellarator Experiment) vacuum vessel has a rather unique shape being very closely coupled topologically to the three-fold stellarator symmetry of the plasma it contains. This shape does not permit the use of the common forms of pressure vessel analysis and necessitates the reliance on finite element analysis. The current paper describes the NCSX vacuum vessel stress analysis including external pressure, thermal, and electro-magnetic loading from internal plasma disruptions and bakeout temperatures of up to 400 degrees centigrade. Buckling and dynamic loading conditions are also considered

Time and space resolved spectroscopic investigation during anode plume formation in a high-current vacuum arc

Science.gov (United States)

Khakpour, A.; Methling, R.; Uhrlandt, D.; Franke, St.; Gortschakow, S.; Popov, S.; Batrakov, A.; Weltmann, K. D.

2017-05-01

This paper presents time and space resolved results of spectroscopic measurements during the formation of an anode plume in the late current pulse phase of a high-current vacuum arc. The formation of the anode plume is investigated systematically based on the occurrence of high-current anode spots, depending on gap distance and current for AC 100 Hz and CuCr7525 butt contacts with a diameter of 10 mm. The anode plume is observed after the extinction of anode spot type 2 in which both the anode and cathode are active. It is concluded from the spatial profiles of the atomic and ionic radiation, parallel and perpendicular to anode surface, that the inner part of the plume is dominated by Cu I radiation, whereas a halo of light emitted by Cu II covers the plume. The radiation intensity of Cu III lines is quite low across the whole anode plume. Upper level excited state densities corresponding to Cu I lines at 510.55, 515.32, 521.82, 578.21 nm are determined. The temporal evolution of the resulting excitation temperature in the centre of the plume varies from 8500 K to 6000 K at 500 µs to 100 µs before current zero, respectively. The density calculated for Cu I at position in the plume is in the range of 1-5  ×  1019 m-3.

Vacuum solutions of a gravity model with vector-induced spontaneous Lorentz symmetry breaking

International Nuclear Information System (INIS)

Bertolami, O.; Paramos, J.

2005-01-01

We study the vacuum solutions of a gravity model where Lorentz symmetry is spontaneously broken once a vector field acquires a vacuum expectation value. Results are presented for the purely radial Lorentz symmetry breaking (LSB), radial/temporal LSB and axial/temporal LSB. The purely radial LSB result corresponds to new black hole solutions. When possible, parametrized post-Newtonian parameters are computed and observational boundaries used to constrain the Lorentz symmetry breaking scale

Beam induced vacuum measurement error in BEPC II

Institute of Scientific and Technical Information of China (English)

无

2011-01-01

When the beam in BEPCII storage ring aborts suddenly, the measured pressure of cold cathode gauges and ion pumps will drop suddenly and decrease to the base pressure gradually. This shows that there is a beam induced positive error in the pressure measurement during beam operation. The error is the difference between measured and real pressures. Right after the beam aborts, the error will disappear immediately and the measured pressure will then be equal to real pressure. For one gauge, we can fit a non-linear pressure-time curve with its measured pressure data 20 seconds after a sudden beam abortion. From this negative exponential decay pumping-down curve, real pressure at the time when the beam starts aborting is extrapolated. With the data of several sudden beam abortions we have got the errors of that gauge in different beam currents and found that the error is directly proportional to the beam current, as expected. And a linear data-fitting gives the proportion coefficient of the equation, which we derived to evaluate the real pressure all the time when the beam with varied currents is on.

Investigation on a new inducer of pulsed eddy current thermography

Directory of Open Access Journals (Sweden)

Min He

2016-09-01

Full Text Available In this paper, a new inducer of pulsed eddy current thermography (PECT is presented. The use of the inducer can help avoid the problem of blocking the infrared (IR camera’s view in eddy current thermography technique. The inducer can also provide even heating of the test specimen. This paper is concerned with the temperature distribution law around the crack on a specimen when utilizing the new inducer. Firstly, relative mathematical models are provided. In the following section, eddy current distribution and temperature distribution around the crack are studied using the numerical simulation method. The best separation distance between the inducer and the specimen is also determined. Then, results of temperature distribution around the crack stimulated by the inducer are gained by experiments. Effect of current value on temperature rise is studied as well in the experiments. Based on temperature data, temperature features of the crack are discussed.

Essence of the Vacuum Quark Condensate

International Nuclear Information System (INIS)

Brodsky, Stanley

2010-01-01

We show that the chiral-limit vacuum quark condensate is qualitatively equivalent to the pseudoscalar meson leptonic decay constant in the sense that they are both obtained as the chiral-limit value of well-defined gauge-invariant hadron-to-vacuum transition amplitudes that possess a spectral representation in terms of the current-quark mass. Thus, whereas it might sometimes be convenient to imagine otherwise, neither is essentially a constant mass-scale that fills all spacetime. This means, in particular, that the quark condensate can be understood as a property of hadrons themselves, which is expressed, for example, in their Bethe-Salpeter or light-front wavefunctions.

Vacuum system for LHC

International Nuclear Information System (INIS)

Groebner, O.

1995-01-01

The Large Hadron Collider (LHC) which is planned at CERN will be housed in the tunnel of the Large Electron Positron collider (LEP) and will store two counter-rotating proton beams with energies of up to 7 TeV in a 27 km accelerator/storage ring with superconducting magnets. The vacuum system for the LHC will be at cryogenic temperatures (between 1.9 and 20 K) and will be exposed to synchrotron radiation emitted by the protons. A stringent limitation on the vacuum is given by the energy deposition in the superconducting coils of the magnets due to nuclear scattering of the protons on residual gas molecules because this may provoke a quench. This effect imposes an upper limit to a local region of increased gas density (e.g. a leak), while considerations of beam lifetime (100 h) will determine more stringent requirements on the average gas density. The proton beam creates ions from the residual gas which may strike the vacuum chamber with sufficient energy to lead to a pressure 'run-away' when the net ion induced desorption yield exceeds a stable limit. These dynamic pressure effects will be limited to an acceptable level by installing a perforated 'beam screen' which shields the cryopumped gas molecules at 1.9 K from synchrotron radiation and which also absorbs the synchrotron radiation power at a higher and, therefore, thermodynamically more efficient temperature. (author)

Composite plastic coatings and face rolled materials technology, energy- and environment-saving, based on irradiation of liquid monomers by broad and high-current electron beams in vacuum

Science.gov (United States)

Vaisburd, David

1994-05-01

The technology is based on the well-known process of hardening some organic liquid monomers and oligomers (resins and lacquers) under the action of ionizing radiation, i.e. electron, ion, ultra-violet, laser, and X-ray beams. The main mechanism of hardening is 3D polymerization of initial monomers induced by irradiation. First of all 1D polymer chains are created. And the next stage is cross-linking of them. Numerical attempts to apply such a process for plastic materials production met some earnest difficulties. Our decision to perform the whole processing in vacuum changed radically the main properties of radiation induced hardening technology. The inhibition of polymerization by reactive oxygen became unessential. The output window foil of accelerator became unnecessary. Application of super broad beams such as 1 sq.m became possible. The entire efficiency of grid electricity was increased to 60% and it was not the limit. One of the main advantages is that the processing carried out in vacuum may satisfy the highest ecological standards. The technology developed is contamination free and environment-saving.

Mechanics of vacuum-enhanced recovery of hydrocarbons

International Nuclear Information System (INIS)

Barnes, D.L.; McWhorter, D.B.

1995-01-01

A growing body of field data demonstrates the enhancement of product recovery that can be achieved by applying a partial vacuum to recovery wells. Typical explanations for the observed improvement in performance invoke an increased slope of the cone of depression created in the water-table surface. Explanations related to water-table slope do not consider the gradient induced in the hydrocarbon by virtue of the airflow. Also, the airflow may induce a gradient in the aqueous phase that is not reflected in a water-table drawdown. The equations for steady-state flow of three immiscible fluids elucidate the fundamental mechanics of vacuum-enhanced recovery or bioslurping. Airflow to the recovery well causes hydrocarbon to migrate toward the well, independent of any gravity effects that may be created. Also, the relative permeability to hydrocarbon is affected by both water and airflow in the vicinity of the recovery well. Two critical airflow rates delineate the conditions for which only air is recovered, air and hydrocarbon are recovered, and all three phases are recovered

Dynamics of the Vacuum and Casimir Analogs to the Hydrogen Atom

Science.gov (United States)

White, Harold; Vera, Jerry; Bailey, Paul; March, Paul; Lawrence, Tim; Sylvester, Andre; Brady, David

2015-01-01

This paper will discuss the current viewpoint of the vacuum state and explore the idea of a "natural" vacuum as opposed to immutable, non-degradable vacuum. This concept will be explored for all primary quantum numbers to show consistency with observation at the level of Bohr theory. A comparison with the Casimir force per unit area will be made, and an explicit function for the spatial variation of the vacuum density around the atomic nucleus will be derived. This explicit function will be numerically modeled using the industry multi-physics tool, COMSOL(trademark), and the eigenfrequencies for the n = 1 to n = 7 states will be found and compared to expectation.

Melting the vacuum

International Nuclear Information System (INIS)

Rafelski, J.

1998-01-01

Results presented at the Quark Matter 97 conference, held in December in Tsukuba, Japan, have provided new insights into the confinement of quarks in matter. The current physics paradigm is that the inertial masses of protons and neutrons, and hence of practically all of the matter around us, originate in the zero-point energy caused by the confinement of quarks inside the small volume of the nucleon. Today, 25 years after Harald Fritzsch, Heinrich Leutwyler and Murray Gell-Mann proposed quantum chromodynamics (QCD) as a means for understanding strongly interacting particles such as nucleons and mesons, our understanding of strong interactions and quark confinement remains incomplete. Quarks and the gluons that bind them together have a ''colour'' charge that may be red, green or blue. But quarks are seen in particles that are white: baryons such as protons and neutrons consist of three quarks with different colour charges, while mesons consist of a quark and an antiquark, and again the colour charge cancels out. To prove that confinement arises from quark-gluon fluctuations in the vacuum that quantum theories dictate exists today, we need to find a way of freeing the colour charge of quarks. Experiments must therefore ''melt'' the vacuum to deconfine quarks and the colour charge. By colliding nuclei at high energies, we hope to produce regions of space filled with free quarks and gluons. This deconfined phase is known as the quark-gluon plasma. At the Tsukuba meeting, Scott Pratt of Michigan State University in the US discussed measurements that show that the hot dense state of matter created in these collisions exists for only 2x10 -23 s. So does the quark gluon plasma exist? No-one doubts that it did at one time, before the vacuum froze into its current state about 20 into the life of the universe, causing the nucleons to form as we know them today. The issue is whether we can recreate this early stage of the universe in laboratory experiments. And if we did

Electrical and optical investigations on the low voltage vacuum arc

International Nuclear Information System (INIS)

Braic, M.; Braic, V.; Pavelescu, G.; Balaceanu, M.; Pavelescu, D.; Dumitrescu, G.; Gherendi, F.

2002-01-01

Preliminary investigations of a low voltage circuit breaker, adapted from a real industrial device, were carried out by electrical and optical methods. Electrical, parameters were measured in the high current arc period and in zero current moment (C.Z) and corroborated with the arc plasma spectroscopic investigations. For the first time in vacuum arc diagnostics, the paper presents results based on single shot time resolved emission spectroscopy around C.Z. The short-circuit current was produced in a special high power installation in order to reproduce exactly the short-circuit regimes developing in low voltage distribution networks. A stainless steel vacuum chamber with classical Cu-Cr electrodes was used. Tests were performed for different current values in the range 3 - 20 kA rms , the voltages being varied between 200 and 1000 V ac . Interruption processes in the different arc regimes (from the diffuse arc mode to the constricted column mode) were analyzed. The success of the arc interruption was analyzed in terms of electric arc energy achieved in the first current halfperiod. The results obtained were corroborated with arc plasma spectroscopic investigations. The emission spectroscopy setup, using an Acton spectrograph and an intensified CCD camera, allowed the spatial and time-resolved investigation of spectra emitted by the vacuum arc plasma. The first truly time-resolved spectroscopic measurements on a single half-period was proven to be a good method to investigate the vacuum arc. Using single shot time resolved spectroscopy around zero current on partial unsuccessful interruption we concluded that the Cu ions, more that Cr ions were responsible for the arc reignition. The financial support for this work comes from NATO-STI SfP /974083 and CORINT-Romania projects. (authors)

Properties of DLC coatings deposited by dc and dc with superimposed pulsed vacuum arc

International Nuclear Information System (INIS)

Zavaleyev, V.; Walkowicz, J.; Aksyonov, D.S.; Luchaninov, A.A.; Reshetnyak, E.N.; Strel'nitskij, V.E.

2014-01-01

Comparative studies of the structure, mechanical and tribological properties of DLC coatings deposited in DC and DC with superimposed high current pulse modes of operation vacuum-arc plasma source with the graphite cathode are presented. Imposition the pulses of high current on DC vacuum-arc discharge allows both increase the deposition rate of DLC coating and reduce the residual compressive stress in the coatings what promotes substantial improvement the adhesion to the substrate. Effect of vacuum arc plasma filtration with Venetian blind filter on the deposition rate and tribological characteristics of the coatings analyzed.

Vacuum mechatronics first international workshop

Energy Technology Data Exchange (ETDEWEB)

Belinski, S.E.; Shirazi, M.; Hackwood, S.; Beni, G. (eds.) (California Univ., Santa Barbara, CA (USA))

1989-01-01

This report contains papers on the following topics: proposed epitaxial thin film growth in the ultra-vacuum of space; particle monitoring and control in vacuum processing equipment; electrostatic dust collector for use in vacuum systems; materials evaluation of an electrically noisy vacuum slip ring assembly; an overview of lubrication and associated materials for vacuum service; the usage of lubricants in a vacuum environment; guidelines and practical applications for lubrication in vacuum; recent development in leak detector and calibrator designs; the durability of ballscrews for ultrahigh vacuum; vacuum-compatible robot for self-contained manufacturing systems; the design, fabrication, and assembly of an advanced vacuum robotics system for space payload calibration; design criteria for mechanisms used in space; and concepts and requirements for semiconductor multiprocess integration in vacuum. These papers are indexed separately elsewhere.

Effects of mode profile on tunneling and traversal of ultracold atoms through vacuum-induced potentials

Science.gov (United States)

Badshah, Fazal; Irfan, Muhammad; Qamar, Sajid; Qamar, Shahid

2016-04-01

We consider the resonant interaction of an ultracold two-level atom with an electromagnetic field inside a high-Q micromaser cavity. In particular, we study the tunneling and traversal of ultracold atoms through vacuum-induced potentials for secant hyperbolic square and sinusoidal cavity mode functions. The phase time which may be considered as an appropriate measure of the time required for the atoms to cross the cavity, significantly modifies with the change of cavity mode profile. For example, switching between the sub and superclassical behaviors in phase time can occur due to the mode function. Similarly, negative phase time appears for the transmission of the two-level atoms in both excited and ground states for secant hyperbolic square mode function which is in contrast to the mesa mode case.

Radiation induced leakage current and stress induced leakage current in ultra-thin gate oxides

International Nuclear Information System (INIS)

Ceschia, M.; Paccagnella, A.; Cester, A.; Scarpa, A.

1998-01-01

Low-field leakage current has been measured in thin oxides after exposure to ionizing radiation. This Radiation Induced Leakage Current (RILC) can be described as an inelastic tunneling process mediated by neutral traps in the oxide, with an energy loss of about 1 eV. The neutral trap distribution is influenced by the oxide field applied during irradiation, thus indicating that the precursors of the neutral defects are charged, likely being defects associated to trapped holes. The maximum leakage current is found under zero-field condition during irradiation, and it rapidly decreases as the field is enhanced, due to a displacement of the defect distribution across the oxide towards the cathodic interface. The RILC kinetics are linear with the cumulative dose, in contrast with the power law found on electrically stressed devices

LHC vacuum system

CERN Document Server

Gröbner, Oswald

1999-01-01

The Large Hadron Collider (LHC) project, now in the advanced construction phase at CERN, comprises two proton storage rings with colliding beams of 7-TeV energy. The machine is housed in the existing LEP tunnel with a circumference of 26.7 km and requires a bending magnetic field of 8.4 T with 14-m long superconducting magnets. The beam vacuum chambers comprise the inner 'cold bore' walls of the magnets. These magnets operate at 1.9 K, and thus serve as very good cryo-pumps. In order to reduce the cryogenic power consumption, both the heat load from synchrotron radiation emitted by the proton beams and the resistive power dissipation by the beam image currents have to be absorbed on a 'beam screen', which operates between 5 and 20 K and is inserted inside the vacuum chamber. The design of this beam screen represents a technological challenge in view of the numerous and often conflicting requirements and the very tight mechanical tolerances imposed. The synchrotron radiation produces strong outgassing from the...

Electric-current-induced step bunching on Si(111)

International Nuclear Information System (INIS)

Homma, Yoshikazu; Aizawa, Noriyuki

2000-01-01

We experimentally investigated step bunching induced by direct current on vicinal Si(111)'1x1' surfaces using scanning electron microscopy and atomic force microscopy. The scaling relation between the average step spacing l b and the number of steps N in a bunch, l b ∼N -α , was determined for four step-bunching temperature regimes above the 7x7-'1x1' transition temperature. The step-bunching rate and scaling exponent differ between neighboring step-bunching regimes. The exponent α is 0.7 for the two regimes where the step-down current induces step bunching (860-960 and 1210-1300 deg. C), and 0.6 for the two regimes where the step-up current induces step bunching (1060-1190 and >1320 deg. C). The number of single steps on terraces also differs in each of the four temperature regimes. For temperatures higher than 1280 deg. C, the prefactor of the scaling relation increases, indicating an increase in step-step repulsion. The scaling exponents obtained agree reasonably well with those predicted by theoretical models. However, they give unrealistic values for the effective charges of adatoms for step-up-current-induced step bunching when the 'transparent' step model is used

Early counterpulse technique applied to vacuum interrupters

International Nuclear Information System (INIS)

Warren, R.W.

1979-11-01

Interruption of dc currents using counterpulse techniques is investigated with vacuum interrupters and a novel approach in which the counterpulse is applied before contact separation. Important increases have been achieved in this way in the maximum interruptible current as well as large reductions in contact erosion. The factors establishing these new limits are presented and ways are discussed to make further improvements

Fabrication of the vacuum vessel for JT-60 machine upgrade

International Nuclear Information System (INIS)

Uchikawa, T.; Takanabe, K.; Tsujimura, S.; Ue, K.; Oka, K.; Kuri, S.; Ioki, K.; Namiki, K.; Suzuki, Y.; Horliike, H.; Ninomiya, H.; Yamamoto, M.; Neyatani, Y.; Ando, T.; Matsukawa, M.

1992-01-01

The JT-60 tokamak was upgraded to double the plasma current to 6 MA. In the JT-60 machine upgrade (JT-60U), the vacuum vessel and poloidal field (PF) coils were renewed. The new vacuum vessel features a three-dimensionally curved, thin double-skin torus with multi-arc D-shaped cross section. The double-skin structure is strengthened with square pipes placed in between the outer and inner skins. Fabrication and site installation of the vessel was smoothly completed in February, 1991. This paper describes an overview of the JT-60U vacuum vessel construction

Electric current distribution of a multiwall carbon nanotube

Energy Technology Data Exchange (ETDEWEB)

Chen, Li-Ying; Chang, Chia-Seng, E-mail: jasonc@phys.sinica.edu.tw [Department of Physics, National Taiwan University, Taipei 10617, Taiwan (China); Institute of Physics, Academia Sinica, Taipei 11529, Taiwan (China); Nano Science and Technology Program, Taiwan International Graduate Program, Academia Sinica and National Taiwan University, Taiwan (China); Chen, Yu-Jyun [Institute of Physics, Academia Sinica, Taipei 11529, Taiwan (China)

2016-07-15

The electric current distribution in a multiwall carbon nanotube (MWCNT) was studied by in situ measuring the electric potential along an individual MWCNT in the ultra-high vacuum transmission electron microscope (TEM). The current induced voltage drop along each section of a side-bonded MWCNT was measured by a potentiometric probe in TEM. We have quantitatively derived that the current on the outermost shell depends on the applied current and the shell diameter. More proportion of the total electronic carriers hop into the inner shells when the applied current is increased. The larger a MWCNT’s diameter is, the easier the electronic carriers can hop into the inner shells. We observed that, for an 8 nm MWCNT with 10 μA current applied, 99% of the total current was distributed on the outer two shells.

R&D ERL: Vacuum

Energy Technology Data Exchange (ETDEWEB)

Mapes, M.; Smart, L.; Weiss, D.; Steszyn, A.; Todd, R.

2010-01-01

The ERL Vacuum systems are depicted in a figure. ERL has eight vacuum volumes with various sets of requirements. A summary of vacuum related requirements is provided in a table. Five of the eight volumes comprise the electron beamline. They are the 5-cell Superconducting RF Cavity, Superconducting e-gun, injection, loop and beam dump. Two vacuum regions are the individual cryostats insulating the 5-cell Superconducting RF Cavity and the Superconducting e-gun structures. The last ERL vacuum volume not shown in the schematic is the laser transport line. The beamline vacuum regions are separated by electropneumatic gate valves. The beam dump is common with loop beamline but is considered a separate volume due to geometry and requirements. Vacuum in the 5-cell SRF cavity is maintained in the {approx}10{sup -9} torr range at room temperature by two 20 l/s ion pumps and in the e-gun SRF cavity by one 60 l/s ion pump. Vacuum in the SRF cavities operated at 2{sup o}K is reduced to low 10{sup -11} torr via cryopumping of the cavity walls. The cathode of the e-gun must be protected from poisoning, which can occur if vacuum adjacent to the e-gun in the injection line exceeds 10-11 torr range in the injection warm beamline near the e-gun exit. The vacuum requirements for beam operation in the loop and beam dump are 10-9 torr range. The beamlines are evacuated from atmospheric pressure to high vacuum level with a particulate free, oil free turbomolecular pumping cart. 25 l/s shielded ion pumps distributed throughout the beamlines maintain the vacuum requirement. Due to the more demanding vacuum requirement of the injection beamline proximate to the e-gun, a vacuum bakeout of the injection beamline is required. In addition, two 200 l/s diode ion pumps and supplemental pumping provided by titanium sublimation pumps are installed in the injection line just beyond the exit of the e-gun. Due to expected gas load a similar pumping arrangement is planned for the beam dump. The

Preliminary structural assessment of DEMO vacuum vessel against a vertical displacement event

International Nuclear Information System (INIS)

Mozzillo, Rocco; Tarallo, Andrea; Marzullo, Domenico; Bachmann, Christian; Di Gironimo, Giuseppe; Mazzone, Giuseppe

2016-01-01

Highlights: • The paper focuses on a preliminary structural analysis of the current concept design of DEMO vacuum vessel. • The Vacuum Vessel was checked against the VDE in combinations with the weight force of all components that the vessel shall bear. • Different configurations for the vacuum vessel supports are considered, showing that the best solution is VV supported at the lower port. • The analyses evaluated the “P damage” according to RCC-MRx code. - Abstract: This paper focuses on a preliminary structural analysis of the current concept design of DEMO vacuum vessel (VV). The VV structure is checked against a vertical load due to a Vertical Displacement Event in combination with the weight force of all components that the main vessel shall bear. Different configurations for the supports are considered. Results show that the greatest safety margins are reached when the tokamak is supported through the lower ports rather than the equatorial ports, though all analyzed configurations are compliant with RCC-MRx design rules.

Preliminary structural assessment of DEMO vacuum vessel against a vertical displacement event

Energy Technology Data Exchange (ETDEWEB)

Mozzillo, Rocco, E-mail: rocco.mozzillo@unina.it [CREATE, University of Naples Federico II, DII, P.le Tecchio 80, 80125, Naples (Italy); Tarallo, Andrea; Marzullo, Domenico [CREATE, University of Naples Federico II, DII, P.le Tecchio 80, 80125, Naples (Italy); Bachmann, Christian [EUROfusion PMU, Boltzmannstraße 2, 85748 Garching (Germany); Di Gironimo, Giuseppe [CREATE, University of Naples Federico II, DII, P.le Tecchio 80, 80125, Naples (Italy); Mazzone, Giuseppe [Unità Tecnica Fusione - ENEA C.R. Frascati, Via E. Fermi 45, 00044 Frascati (Italy)

2016-11-15

Highlights: • The paper focuses on a preliminary structural analysis of the current concept design of DEMO vacuum vessel. • The Vacuum Vessel was checked against the VDE in combinations with the weight force of all components that the vessel shall bear. • Different configurations for the vacuum vessel supports are considered, showing that the best solution is VV supported at the lower port. • The analyses evaluated the “P damage” according to RCC-MRx code. - Abstract: This paper focuses on a preliminary structural analysis of the current concept design of DEMO vacuum vessel (VV). The VV structure is checked against a vertical load due to a Vertical Displacement Event in combination with the weight force of all components that the main vessel shall bear. Different configurations for the supports are considered. Results show that the greatest safety margins are reached when the tokamak is supported through the lower ports rather than the equatorial ports, though all analyzed configurations are compliant with RCC-MRx design rules.

Electroweak vacuum instability and renormalized Higgs field vacuum fluctuations in the inflationary universe

Energy Technology Data Exchange (ETDEWEB)

Kohri, Kazunori [Institute of Particle and Nuclear Studies, KEK, 1-1 Oho, Tsukuba 305-0801 (Japan); Matsui, Hiroki, E-mail: kohri@post.kek.jp, E-mail: matshiro@post.kek.jp [The Graduate University for Advanced Studies (SOKENDAI), 1-1 Oho, Tsukuba 305-0801 (Japan)

2017-08-01

In this work, we investigated the electroweak vacuum instability during or after inflation. In the inflationary Universe, i.e., de Sitter space, the vacuum field fluctuations < δ φ {sup 2} > enlarge in proportion to the Hubble scale H {sup 2}. Therefore, the large inflationary vacuum fluctuations of the Higgs field < δ φ {sup 2} > are potentially catastrophic to trigger the vacuum transition to the negative-energy Planck-scale vacuum state and cause an immediate collapse of the Universe. However, the vacuum field fluctuations < δ φ {sup 2} >, i.e., the vacuum expectation values have an ultraviolet divergence, and therefore a renormalization is necessary to estimate the physical effects of the vacuum transition. Thus, in this paper, we revisit the electroweak vacuum instability from the perspective of quantum field theory (QFT) in curved space-time, and discuss the dynamical behavior of the homogeneous Higgs field φ determined by the effective potential V {sub eff}( φ ) in curved space-time and the renormalized vacuum fluctuations < δ φ {sup 2} >{sub ren} via adiabatic regularization and point-splitting regularization. We simply suppose that the Higgs field only couples the gravity via the non-minimal Higgs-gravity coupling ξ(μ). In this scenario, the electroweak vacuum stability is inevitably threatened by the dynamical behavior of the homogeneous Higgs field φ, or the formations of AdS domains or bubbles unless the Hubble scale is small enough H < Λ {sub I} .

Vacuum therapy for chronic wounds

Directory of Open Access Journals (Sweden)

Ekaterina Leonidovna Zaytseva

2012-09-01

Full Text Available Chronic wound in patients with diabetes mellitus (DM is one of the most urgent problems of modern diabetology and surgery. Numberof patients suffering from different types of chronic wounds follows increase in DM incidence. Vacuum therapy is a novel perspectivemethod of topical treatment for non-healing chronic wounds of various etiology. Current review addresses experimental and clinicalevidence for this method.

Vacuum system for ISABELLE

International Nuclear Information System (INIS)

Hobson, J.P.

1975-01-01

An analysis is presented of the proposed vacuum system for the planned ISABELLE storage rings with respect to acceptability and practicality from the vacuum viewport. A comparison is made between the proposed vacuum system and the vacuum system at the CERN ISR, and some comments on various design and operational parameters are made

Upgraded vacuum arc ion source for metal ion implantation

International Nuclear Information System (INIS)

Nikolaev, A. G.; Oks, E. M.; Savkin, K. P.; Yushkov, G. Yu.; Brown, I. G.

2012-01-01

Vacuum arc ion sources have been made and used by a large number of research groups around the world over the past twenty years. The first generation of vacuum arc ion sources (dubbed ''Mevva,'' for metal vapor vacuum arc) was developed at Lawrence Berkeley National Laboratory in the 1980s. This paper considers the design, performance parameters, and some applications of a new modified version of this kind of source which we have called Mevva-V.Ru. The source produces broad beams of metal ions at an extraction voltage of up to 60 kV and a time-averaged ion beam current in the milliampere range. Here, we describe the Mevva-V.Ru vacuum arc ion source that we have developed at Tomsk and summarize its beam characteristics along with some of the applications to which we have put it. We also describe the source performance using compound cathodes.

Determining the mode of high voltage breakdowns in vacuum devices

International Nuclear Information System (INIS)

Miller, H.C.; Furno, E.J.; Sturtz, J.P.

1980-01-01

Devices were constructed which were essentially vacuum diodes equipped with windows allowing observation of high voltage breakdowns. The waveform of the applied voltage was photographed, and the x-ray output was monitored to investigate electrical breakdown in these vacuum diodes. Results indicate that breakdowns may be divided into two types: (1) vacuum (interelectrode) breakdown - characterized by a diffuse moderately bright discharge, a relative slow and smooth voltage collapse, and a large burst of x-rays, and (2) surface (insulator) flashover - characterized by a bright discharge with a very bright filamentary core, a relatively fast and noisy voltage collapse and no x-ray burst. Useful information concerning the type of breakdown in a vacuum device can be obtained by monitoring the voltage (current) waveform and the x-ray output

Vacuum extraction

DEFF Research Database (Denmark)

Maagaard, Mathilde; Oestergaard, Jeanett; Johansen, Marianne

2012-01-01

Objectives. To develop and validate an Objective Structured Assessment of Technical Skills (OSATS) scale for vacuum extraction. Design. Two-part study design: Primarily, development of a procedure-specific checklist for vacuum extraction. Hereafter, validation of the developed OSATS scale for vac...

Pion Susceptibilities of the Vacuum in a Modified Global Colour Symmetry Model

Institute of Scientific and Technical Information of China (English)

ZONG Hong-Shi; WU Xiao-Hua; DING Xiao-Ping; L0 Xiao-Fu; ZHAO En-Guang

2001-01-01

Based on a modified version of the global color symmetry model, the pion susceptibilities of vacuum needed in the QCD sum rule external-field method for the coupling of pseudoscalar current to hadron have bean calculated beyond the vacuum saturation approximation. Comparison with the previous estimations has been given.

Protection of power transformers against geomagnetically induced currents

Directory of Open Access Journals (Sweden)

Gurevich Vladimir

2011-01-01

Full Text Available The article examines the problem of saturation and failure of power transformers under geomagnetically induced currents and currents of the E3 component of high-altitude nuclear explosions. It also describes a special protective relay reacting on DC component in the transformer neutral current.

Ultra-high vacuum system of the Brookhaven National Synchrotron Light Source

International Nuclear Information System (INIS)

Foerster, C.L.

1995-01-01

The rings of the National Synchrotron Light Source (NSLS) have been supplying light to numerous users for approximately a decade and recently a fully conditioned machine vacuum at design currents was obtained. A brief description of the x-ray storage ring, the VUV storage ring and their current supply is given along with some of their features. The ultra-high vacuum system employed for the storage rings and their advantages for the necessary stored beam environments are discussed including, a brief history of time. 15 refs., 2 tabs., 8 figs

The interaction of vacuum arcs with magnetic fields and applications

International Nuclear Information System (INIS)

Gorman, J.G.; Kimblin, C.W.; Slade, P.G.; Voshall, R.E.; Wien, R.E.

1983-01-01

Vacuum arc/magnetic field interactions are reviewed and extended. An axial magnetic field (parallel to current flow) produces a stable and diffuse vacuum arc. These properties have been used to build a reliable dc switch for the Tokamak Fusion Test Reactor at Princeton. The switching duty for this Ohmic Heating Interrupter involves repetitive interruption of 24kA dc against a 27kV recovery voltage. A transverse magnetic field (perpendicular to current flow) produces an unstable arc with an ensuing high arc voltage. This property has been used to complete a metallic return transfer breaker for the Pacific HVDC Intertie, here the switching duty involves interruption of currents up to 2200A dc against an 80kV recovery voltage

Induced Current Characteristics Due to Laser Induced Plasma and Its Application to Laser Processing Monitoring

International Nuclear Information System (INIS)

Madjid, Syahrun Nur; Idris, Nasrullah; Kurniawan, Koo Hendrik; Kagawa, Kiichiro

2011-01-01

In laser processing, suitable conditions for laser and gas play important role in ensuring a high quality of processing. To determine suitable conditions, we employed the electromagnetic phenomena associated with laser plasma generation. An electrode circuit was utilised to detect induced current due to the fast electrons propelled from the material during laser material processing. The characteristics of induced current were examined by changing parameters such as supplied voltage, laser pulse energy, number of laser shots, and type of ambient gas. These characteristics were compared with the optical emission characteristics. It was shown that the induced current technique proposed in this study is much more sensitive than the optical method in monitoring laser processing, that is to determine the precise focusing condition, and to accurately determine the moment of completion of laser beam penetration. In this study it was also shown that the induced current technique induced by CW CO 2 laser can be applied in industrial material processing for monitoring the penetration completion in a stainless steel plate drilling process.

Vacuum arc ion charge state distributions

International Nuclear Information System (INIS)

Brown, I.G.; Godechot, X.

1990-06-01

We have measured vacuum arc ion charge state spectra for a wide range of metallic cathode materials. The charge state distributions were measured using a time-of-flight diagnostic to monitor the energetic ion beam produced by a metal vapor vacuum arc ion source. We have obtained data for 48 metallic cathode elements: Li, C, Mg, Al, Si, Ca, Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Ge, Sr, Y, Zr, Nb, Mo, Pd, Ag, Cd, In, Sn, Ba, La, Ce, Pr, Nd, Sm, Gd, Dy, Ho, Er, Yb, Hf, Ta, W, Ir, Pt, Au, Pb, Bi, Th and U. The arc was operated in a pulsed mode with pulse length 0.25 msec; arc current was 100 A throughout. This array of elements extends and completes previous work by us. In this paper the measured distributions are cataloged and compared with our earlier results and with those of other workers. We also make some observations about the performance of the various elements as suitable vacuum arc cathode materials

Vacuum arc ion charge-state distributions

International Nuclear Information System (INIS)

Brown, I.G.; Godechot, X.

1991-01-01

The authors have measured vacuum arc ion charge-state spectra for a wide range of metallic cathode materials. The charge-state distributions were measured using a time-of-flight diagnostic to monitor the energetic ion beam produced by a metal vapor vacuum arc ion source. They have obtained data for 48 metallic cathode elements: Li, C, Mg, Al, Si, Ca, Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Ge, Sr, Y, Zr, Nb, Mo, Pd, Ag, Cd, In, Sn, Ba, La, Ce, Pr, Nd, Sm, Gd, Dy, Ho, Er, Yb, Hf, Ta, W, Ir, Pt, Au, Pb, Bi, Th, and U. The arc was operated in a pulsed mode with pulse length 0.25 ms; arc current was 100 A throughout. This array of elements extends and completes previous work by the authors. In this paper the measured distributions are cataloged and compared with their earlier results and those of other workers. They also make some observations about the performance of the various elements as suitable vacuum arc cathode materials

Vessel eddy current characteristics in SST-1 tokamak

Energy Technology Data Exchange (ETDEWEB)

Jana, Subrata; Pradhan, Subrata, E-mail: pradhan@ipr.res.in; Dhongde, Jasraj; Masand, Harish

2016-11-15

Highlights: • Eddy current distribution in the SST-1 vacuum vessel. • Circuit model analysis of eddy current. • A comparison of the field lines with and without the plasma column in identical conditions. • The influence of eddy current in magnetic NULL dynamics. - Abstract: Eddy current distribution in the vacuum vessel of the Steady state superconducting (SST-1) tokamak has been determined from the experimental data obtained using an array of internal voltage loops (flux loop) installed inside the vacuum vessel. A simple circuit model has been employed. The model takes into account the geometric and constructional features of SST-1 vacuum vessel. SST-1 vacuum vessel is a modified ‘D’ shaped vessel having major axis of 1.285 m and minor axis of 0.81 m and has been manufactured from non-magnetic stainless steel. The Plasma facing components installed inside the vacuum vessel are graphite blocks mounted on Copper Chromium Zirconium (CuCrZr) heat sink plates on inconel supports. During discharge of the central solenoid, eddy currents get generated in the vacuum vessel and passive supports on it. These eddy currents influence the early magnetic NULL dynamics and plasma break-down and start-up characteristics. The computed results obtained from the model have been benchmarked against experimental data obtained in large number of SST-1 plasma shots. The results are in good agreement. Once bench marked, the calculated eddy current based on flux loop signal and circuit equation model has been extended to the reconstruction of the overall B- field contours of SST-1 tokamak in the vessel region. A comparison of the field lines with and without the plasma column in identical conditions of the central solenoid and equilibrium field profiles has also been done with an aim to quantify the diagnostics responses in vacuum shots.

Beam tube vacuum in future superconducting proton colliders

International Nuclear Information System (INIS)

Turner, W.

1994-10-01

The beam tube vacuum requirements in future superconducting proton colliders that have been proposed or discussed in the literature -- SSC, LHC, and ELN -- are reviewed. The main beam tube vacuum problem encountered in these machines is how to deal with the magnitude of gas desorption and power deposition by synchrotron radiation while satisfying resistivity, impedance, and space constraints in the cryogenic environment of superconducting magnets. A beam tube vacuum model is developed that treats photodesorption of tightly bound H, C, and 0, photodesorption of physisorbed molecules, and the isotherm vapor pressure of H 2 . Experimental data on cold tube photodesorption experiments are reviewed and applied to model calculations of beam tube vacuum performance for simple cold beam tube and liner configurations. Particular emphasis is placed on the modeling and interpretation of beam tube photodesorpiion experiments at electron synchrotron light sources. The paper also includes discussion of the constraints imposed by beam image current heating, the growth rate of the resistive wall instability, and single-bunch instability impedance limits

LHC vacuum upgrade during LS1

International Nuclear Information System (INIS)

Jimenez, J.M.; Baglin, V.; Chiggiato, P.; Cruikshank, P.; Gallilee, M.; Garion, C.; Gomes, P.

2012-01-01

The last two years of LHC operation have highlighted concerns on the levels of the dynamic vacuum in the long straight sections in presence of high intensity beams. The analysis of the existing data has shown relationship between pressures spikes and beam screen temperature oscillations or micro-sparking in the RF fingers of the bellows on one side and coincidence of pressure bumps with stimulated desorption by electron cloud, beam losses and/or thermal out gassing stimulated by higher order modes (HOM) losses. The electron cloud mitigation solutions will be adapted to the different configurations: cold/warm transitions, non-coated surfaces in direct view of beams, photoelectrons, etc. All scenarios will be presented together with their efficiencies. Additional pumping and re-engineering of components will reduce the sensitivity of the vacuum system to beam losses or HOM inducing out gassing. The expected margin at nominal intensity and energy resulting from these consolidations will be summarized. Finally, the challenges of the Experimental areas will be addressed, more specifically the status of the new Beryllium pipes (ATLAS and CMS) which are in the critical path and the consolidation of vacuum instrumentation, pumping and electron cloud mitigation. The risk corresponding to the proposed consolidations will be shown and the margins with respect to the schedule analysed. (authors)

Construction of vacuum system for Tristan accumulation ring

International Nuclear Information System (INIS)

Ishimaru, H.; Horikoshi, G.; Kobayashi, M.; Kubo, T.; Mizuno, H.; Momose, T.; Narushima, K.; Watanabe, H.; Yamaguchi, H.

1983-01-01

An all aluminum-alloy vacuum system for the TRISTAN accumulation ring is now under construction. Aluminum and aluminum alloys are preferred materials for ultrahigh vacuum systems of large electron storage rings because of their good thermal conductivity, extremely low outgassing rate, and low residual radioactivity. Vacuum beam chambers for the dipole and quadrupole magnets are extruded using porthole dies. The aluminum alloy 6063-T6 provides superior performance in extrusion. For ultrahigh vacuum performance, a special extrusion technique is applied which, along with the outgassing procedure used, is described in detail. Aluminum alloy 3004 seamless elliptical bellows are inserted between the dipole and quadrupole magnet chambers. These bellows are produced by the hydraulic forming of a seamless tube. The seamless bellows and the beam chambers are joined by fully automatic welding. The ceramic chambers for the kicker magnets, the fast bump magnets, and the slow beam intensity monitor are inserted in the aluminum alloy beam chambers. The ceramic chamber (98% alumina) and elliptical bellows are brazed with brazing sheets (4003-3003-4003) in a vacuum furnace. The brazing technique is described. The inner surface of the ceramic chamber is coated with a TiMo alloy by vacuum evaporation to permit a smooth flow of the RF wall current. Other suitable aluminum alloy components, including fittings, feedthroughs, gauges, optical windows, sputter ion pumps, turbomolecular pumps, and valves have been developed; their fabrication is described

Milking performance evaluation and factors affecting milking claw vacuum levels with flow simulator.

Science.gov (United States)

Enokidani, Masafumi; Kawai, Kazuhiro; Shinozuka, Yasunori; Watanabe, Aiko

2017-08-01

Milking performance of milking machines that matches the production capability of dairy cows is important in reducing the risk of mastitis, particularly in high-producing cows. This study used a simulated milking device to examine the milking performance of the milking system of 73 dairy farms and to analyze the factors affecting claw vacuum. Mean claw vacuum and range of fluctuation of claw vacuum (claw vacuum range) were measured at three different flow rates: 5.7, 7.6 and 8.7 kg/min. At the highest flow rate, only 16 farms (21.9%) met both standards of mean claw vacuum ≥35 kPa and claw vacuum range ≤ 7 kPa, showing that milking systems currently have poor milking performance. The factors affecting mean claw vacuum were claw type, milk-meter and vacuum shut-off device; the factor affecting claw vacuum range was claw type. Examination of the milking performance of the milking system using a simulated milking device allows an examination of the performance that can cope with high producing cows, indicating the possibility of reducing the risk of mastitis caused by inappropriate claw vacuum. © 2016 Japanese Society of Animal Science.

Laboratory Experiments on Propagating Plasma Bubbles into Vacuum, Vacuum Magnetic Field, and Background Plasmas

Science.gov (United States)

Lynn, Alan G.; Zhang, Yue; Gilmore, Mark; Hsu, Scott

2014-10-01

We discuss the dynamics of plasma ``bubbles'' as they propagate through a variety of background media. These bubbles are formed by a pulsed coaxial gun with an externally applied magnetic field. Bubble parameters are typically ne ~1020 m-3, Te ~ 5 - 10 eV, and Ti ~ 10 - 15 eV. The structure of the bubbles can range from unmagnetized jet-like structures to spheromak-like structures with complex magnetic flux surfaces. Some of the background media the bubbles interact with are vacuum, vacuum with magnetic field, and other magnetized plasmas. These bubbles exhibit different qualitative behavior depending on coaxial gun parameters such as gas species, gun current, and gun bias magnetic field. Their behavior also depends on the parameters of the background they propagate through. Multi-frame fast camera imaging and magnetic probe data are used to characterize the bubble evolution under various conditions.

Development of a Modified Vacuum Cleaner for Lunar Surface Systems

Science.gov (United States)

Toon, Katherine P.; Lee, Steve A.; Edgerly, Rachel D.

2010-01-01

The National Aeronautics and Space Administration (NASA) mission to expand space exploration will return humans to the Moon with the goal of maintaining a long-term presence. One challenge that NASA will face returning to the Moon is managing the lunar regolith found on the Moon's surface, which will collect on extravehicular activity (EVA) suits and other equipment. Based on the Apollo experience, the issues astronauts encountered with lunar regolith included eye/lung irritation, and various hardware failures (seals, screw threads, electrical connectors and fabric contamination), which were all related to inadequate lunar regolith mitigation. A vacuum cleaner capable of detaching, transferring, and efficiently capturing lunar regolith has been proposed as a method to mitigate the lunar regolith problem in the habitable environment on lunar surface. In order to develop this vacuum, a modified "off-the-shelf' vacuum cleaner will be used to determine detachment efficiency, vacuum requirements, and optimal cleaning techniques to ensure efficient dust removal in habitable lunar surfaces, EVA spacesuits, and air exchange volume. During the initial development of the Lunar Surface System vacuum cleaner, systematic testing was performed with varying flow rates on multiple surfaces (fabrics and metallics), atmospheric (14.7 psia) and reduced pressures (10.2 and 8.3 psia), different vacuum tool attachments, and several vacuum cleaning techniques in order to determine the performance requirements for the vacuum cleaner. The data recorded during testing was evaluated by calculating particulate removal, relative to the retained simulant on the tested surface. In addition, optical microscopy was used to determine particle size distribution retained on the surface. The scope of this paper is to explain the initial phase of vacuum cleaner development, including historical Apollo mission data, current state-of-the-art vacuum cleaner technology, and vacuum cleaner testing that has

TFCX pumped limiter and vacuum pumping system design and analysis

International Nuclear Information System (INIS)

Haines, J.R.

1985-04-01

Impurity control system design and performance studies were performed in support of the Tokamak Fusion Core Experiment (TFCX) pre-conceptual design. Efforts concentrated on pumped limiter and vacuum pumping system design configuration, thermal/mechanical and erosion lifetime performance of the limiter protective surface, and helium ash removal performance. The reference limiter design forms a continuous toroidal belt at the bottom of the device and features a flat surface with a single leading edge. The vacuum pumping system features large vacuum ducts (diameter approximately 1 m) and high-speed, compound cryopumps. Analysis results indicate that the limiter/vacuum pumping system design provides adequate helium ash removal. Erosion, primarily by disruption-induced vaporization and/or melting, limits the protective surface lifetime to about one calendar year or only about 60 full-power hours of operation. In addition to evaluating impurity control system performance for nominal TFCX conditions, these studies attempt to focus on the key plasma physics and engineering design issues that should be addressed in future research and development programs

Cassette blanket and vacuum building: key elements in fusion reactor maintenance

International Nuclear Information System (INIS)

Werner, R.W.

1977-01-01

The integration of two concepts important to fusion power reactors is discussed. The first concept is the vacuum building which improves upon the current fusion reactor designs. The second concept, the use of the cassette blanket within the vacuum building environment, introduces four major improvements in blanket design: cassette blanket module, zoning concept, rectangular blanket concept, and internal tritium recovery

Can observations inside the Solar System reveal the gravitational properties of the quantum vacuum?

CERN Document Server

Hajdukovic, Dragan Slavkov

2013-01-01

The understanding of the gravitational properties of the quantum vacuum might be the next scientific revolution.It was recently proposed that the quantum vacuum contains the virtual gravitational dipoles; we argue that this hypothesis might be tested within the Solar System. The key point is that quantum vacuum ("enriched" with the gravitational dipoles) induces a retrograde precession of the perihelion. It is obvious that this phenomenon might eventually be revealed by more accurate studies of orbits of planets and orbits of the artificial Earth satellites. However, we suggest that potentialy the best "laboratory" for the study of the gravitational properties of the quantum vacuum is the Dwarf Planet Eris and its satellite Dysnomia; the distance of nearly 100AU makes it the unique system in which the precession of the perihelion of Dysnomia (around Eris) is strongly dominated by the quantum vacuum.

Vacuum level effects on gait characteristics for unilateral transtibial amputees with elevated vacuum suspension.

Science.gov (United States)

Xu, Hang; Greenland, Kasey; Bloswick, Donald; Zhao, Jie; Merryweather, Andrew

2017-03-01

The elevated vacuum suspension system has demonstrated unique health benefits for amputees, but the effect of vacuum pressure values on gait characteristics is still unclear. The purpose of this study was to investigate the effects of elevated vacuum levels on temporal parameters, kinematics and kinetics for unilateral transtibial amputees. Three-dimensional gait analysis was conducted in 9 unilateral transtibial amputees walking at a controlled speed with five vacuum levels ranging from 0 to 20inHg, and also in 9 able-bodied subjects walking at self-preferred speed. Repeated ANOVA and Dunnett's t-test were performed to determine the effect of vacuum level and limb for within subject and between groups. The effect of vacuum level significantly affected peak hip external rotation and external knee adduction moment. Maximum braking and propulsive ground reaction forces generally increased for the residual limb and decreased for the intact limb with increasing vacuum. Additionally, the intact limb experienced an increased loading due to gait asymmetry for several variables. There was no systematic vacuum level effect on gait. Higher vacuum levels, such as 15 and 20inHg, were more comfortable and provided some relief to the intact limb, but may also increase the risk of osteoarthritis of the residual limb due to the increased peak external hip and knee adduction moments. Very low vacuum should be avoided because of the negative effects on gait symmetry. A moderate vacuum level at 15inHg is suggested for unilateral transtibial amputees with elevated vacuum suspension. Copyright © 2017 Elsevier Ltd. All rights reserved.

Decay of the de Sitter vacuum

Science.gov (United States)

Anderson, Paul R.; Mottola, Emil; Sanders, Dillon H.

2018-03-01

The decay rate of the Bunch-Davies state of a massive scalar field in the expanding flat spatial sections of de Sitter space is determined by an analysis of the particle pair creation process in real time. The Feynman definition of particle and antiparticle Fourier mode solutions of the scalar wave equation and their adiabatic phase analytically continued to the complexified time domain show conclusively that the Bunch-Davies state is not the vacuum state at late times. The closely analogous creation of charged particle pairs in a uniform electric field is reviewed and Schwinger's result for the vacuum decay rate is recovered by this same real time analysis. The vacuum decay rate in each case is also calculated by switching the background field on adiabatically, allowing it to act for a very long time, and then adiabatically switching it off again. In both the uniform electric field and de Sitter cases, the particles created while the field is switched on are verified to be real, in the sense that they persist in the final asymptotic flat zero-field region. In the de Sitter case, there is an interesting residual dependence of the rate on how the de Sitter phase is ended, indicating a greater sensitivity to spatial boundary conditions. The electric current of the created particles in the E -field case and their energy density and pressure in the de Sitter case are also computed, and the magnitude of their backreaction effects on the background field estimated. Possible consequences of the Hubble scale instability of the de Sitter vacuum for cosmology, vacuum dark energy, and the cosmological "constant" problem are discussed.

Fermionic vacuum polarization by a cylindrical boundary in the cosmic string spacetime

International Nuclear Information System (INIS)

Bezerra de Mello, E. R.; Bezerra, V. B.; Saharian, A. A.; Tarloyan, A. S.

2008-01-01

The vacuum expectation values of the energy-momentum tensor and the fermionic condensate are analyzed for a massive spinor field obeying the MIT bag boundary condition on a cylindrical shell in the cosmic string spacetime. Both regions inside and outside the shell are considered. By applying to the corresponding mode sums a variant of the generalized Abel-Plana formula, we explicitly extract the parts in the expectation values corresponding to the cosmic string geometry without boundaries. In this way the renormalization procedure is reduced to that for the boundary-free cosmic string spacetime. The parts induced by the cylindrical shell are presented in terms of integrals rapidly convergent for points away from the boundary. The behavior of the vacuum densities is investigated in various asymptotic regions of the parameters. In the limit of large values of the planar angle deficit, the boundary-induced expectation values are exponentially suppressed. As a special case, we discuss the fermionic vacuum densities for the cylindrical shell on the background of the Minkowski spacetime.

Sewerage force adjustment technology for energy conservation in vacuum sanitation systems

Science.gov (United States)

Guo, Zhonghua; Li, Xiaoning; Kagawa, Toshiharu

2013-03-01

The vacuum sanitation is the safe and sound disposal approach of human excreta under the specific environments like flights, high speed trains and submarines. However, the propulsive force of current systems is not adjustable and the energy consumption does not adapt to the real time sewerage requirement. Therefore, it is important to study the sewerage force adjustment to improve the energy efficiency. This paper proposes an energy conservation design in vacuum sanitation systems with pneumatic ejector circuits. The sewerage force is controlled by changing the systematic vacuum degree according to the amount of the excreta. In particular, the amount of the excreta is tested by liquid level sensor and mass sensor. According to the amount of the excreta, the relationship between the excreta amount and the sewerage force is studied to provide proper propulsive force. In the other aspect, to provide variable vacuum degrees for different sanitation requirements, the suction and discharge system is designed with pneumatic vacuum ejector. On the basis of the static flow-rate characteristics and the vacuum generation model, the pressure response in the ejector circuit is studied by using the static flow rate characteristics of the ejector and air status equation. The relationship is obtained between supplied compressed air and systematic vacuum degree. When the compressed air is supplied to the ejector continuously, the systematic vacuum degree increases until the vacuum degree reaches the extreme value. Therefore, the variable systematic vacuum degree is obtained by controlling the compressed air supply of the ejector. To verify the effect of energy conservation, experiments are carried out in the artificial excreta collection, and the variable vacuum-degree design saves more than 30% of the energy supply. The energy conservation is realized effectively in the new vacuum sanitation systems with good application prospect. The proposed technology provides technological

Introduction to vacuum technology: supplementary study material developed for IVS sponsored vacuum courses

International Nuclear Information System (INIS)

Bhusan, K.G.

2008-01-01

Vacuum technology has advanced to a large extent mainly from the demands of experimental research scientists who have more than ever understood the need for clean very low pressure environments. This need only seems to increase as the lowest pressures achievable in a laboratory setup are dropping down by the decade. What is not usually said is that conventional techniques of producing ultrahigh vacuum have also undergone a metamorphosis in order to cater to the multitude of restrictions in modern day scientific research. This book aims to give that practical approach to vacuum technology. The basics are given in the first chapter with more of a definition oriented approach - which is practically useful. The second chapter deals with the production of vacuum and ultrahigh vacuum with an emphasis on the working principles of several pumps and their working pressure ranges. Measurement of low pressures, both total and partial is presented in the third chapter with a note on leak detection and mass spectrometric techniques. Chapter 4 gives an overview of the materials that are vacuum compatible and their material properties. Chapter 5 gives the necessary methods to be followed for cleaning of vacuum components especially critical if ultrahigh vacuum environment is required. The practical use of a ultrahigh vacuum environment is demonstrated in Chapter 6 for production of high quality thin films through vapour deposition

Micromagnetic Simulation of Strain-Assisted Current-Induced Magnetization Switching

Directory of Open Access Journals (Sweden)

H. B. Huang

2016-01-01

Full Text Available We investigated the effect of substrate misfit strain on the current-induced magnetization switching in magnetic tunnel junctions by combining micromagnetic simulation with phase-field microelasticity theory. Our results indicate that the positive substrate misfit strain can decrease the critical current density of magnetization switching by pushing the magnetization from out-of-plane to in-plane directions, while the negative strain pushes the magnetization back to the out-of-plane directions. The magnetic domain evolution is obtained to demonstrate the strain-assisted current-induced magnetization switching.

Comparison of cold and warm vacuum systems for intersecting storage rings

International Nuclear Information System (INIS)

Halama, H.J.; Herrera, J.C.

1975-01-01

In storage rings employing superconducting magnets, the use of a cold bore as a cryopump appears, at first glance, as simple and economical. Since the selection of a cold or warm vacuum system has far-reaching implications on the basic design, each system is considered in some detail. The theoretical and practical limitations imposed on the maximum beam current by the gas desorption from the chamber walls are discussed. A realistic design of a cold vacuum chamber is developed and then compared with the proposed warm ISABELLE vacuum system. The comparison shows that the warm approach is preferable. (U.S.)

Use of the vacuum ultraviolet spectral region for laser-induced breakdown spectroscopy-based Martian geology and exploration

International Nuclear Information System (INIS)

Radziemski, Leon; Cremers, David A.; Benelli, Katharine; Khoo, Cynthia; Harris, Ronny D.

2005-01-01

Several elements important to planetary geology (e.g. Br, C, Cl, P, S) and the human exploration of Mars (e.g. toxic elements such as As) have strong emission lines in the purge and vacuum ultraviolet (VUV) spectral region (100-200 nm). This spectral region has not been extensively studied for space applications using geological samples. We studied emissions from the laser-induced breakdown spectroscopy (LIBS) plasma in this region using a sample chamber filled with 7 torr (930 Pa) of CO 2 to simulate the Martian atmosphere. Pressures down to 0.02 torr were also used to evaluate the effect of the residual CO 2 on the spectra and to begin investigating the use of VUV-LIBS for airless bodies such as asteroids and the Moon. Spectra were recorded using a 0.3-m vacuum spectrometer with an intensified CCD (ICCD) camera. The effects of time delay and laser energy on LIBS detection at reduced pressure were examined. The effect of ambient CO 2 on the detection of C in soil was also evaluated. Lines useful for the spectrochemical analysis of As, Br, C, Cl, P, and S were determined and calibration curves were prepared for these elements. Although LIBS is being developed for stand-off analysis at many meters distance, the experiments reported here were aimed at in-situ (close-up) analysis

Metal vapor vacuum arc ion sources

International Nuclear Information System (INIS)

Brown, I.G.; Dickinson, M.R.; Galvin, J.E.; Godechot, X.; MacGill, R.A.

1990-06-01

We have developed a family of metal vapor vacuum are (MEVVA) high current metal ion sources. The sources were initially developed for the production of high current beams of metal ions for heavy ion synchrotron injection for basic nuclear physics research; more recently they have also been used for metal ion implantation. A number of different embodiments of the source have been developed for these specific applications. Presently the sources operate in a pulsed mode, with pulse width of order 1 ms and repetition rate up to 100 pps. Beam extraction voltage is up to 100 kV, and since the ions produced in the vacuum arc plasma are in general multiply ionized the ion energy is up to several hundred keV. Beam current is up to several Amperes peak and around 10 mA time averaged delivered onto target. Nearly all of the solid metals of the Periodic Table have been use to produce beam. A number of novel features have been incorporated into the sources, including multiple cathodes and the ability to switch between up to 18 separate cathode materials simply and quickly, and a broad beam source version as well as miniature versions. here we review the source designs and their performance. 45 refs., 7 figs

Vacuum infusion manufacturing and experimental characterization of Kevlar/epoxy composites

International Nuclear Information System (INIS)

Ricciardi, M. R.; Giordano, M.; Antonucci, V.; Langella, A.; Nele, L.

2014-01-01

Epoxy/Kevlar composites have been manufactured by conventional Vacuum Infusion process and the Pulse Infusion technique. Pulse Infusion allows to control the pressure of the vacuum bag on the dry fiber reinforcement by using a proper designed pressure distributor that induces a pulsed transverse action and promotes the through thickness resin flow. The realized composite panel have been mechanically characterized by performing tensile and short beam shear tests according with the ASTM D3039 and ASTM D2344/D 2344M standard respectively in order to investigate the effect of Pulse Infusion on the tensile strength and ILSS

Vacuum infusion manufacturing and experimental characterization of Kevlar/epoxy composites

Science.gov (United States)

Ricciardi, M. R.; Giordano, M.; Langella, A.; Nele, L.; Antonucci, V.

2014-05-01

Epoxy/Kevlar composites have been manufactured by conventional Vacuum Infusion process and the Pulse Infusion technique. Pulse Infusion allows to control the pressure of the vacuum bag on the dry fiber reinforcement by using a proper designed pressure distributor that induces a pulsed transverse action and promotes the through thickness resin flow. The realized composite panel have been mechanically characterized by performing tensile and short beam shear tests according with the ASTM D3039 and ASTM D2344/D 2344M standard respectively in order to investigate the effect of Pulse Infusion on the tensile strength and ILSS.

Simulation Research of Magnetic Constriction Effect and Controlling by Axial Magnetic Field of Vacuum Arc

Institute of Scientific and Technical Information of China (English)

王立军; 贾申利; 史宗谦; 荣命哲

2005-01-01

Based on magnetohydrodynamic (MHD) model of vacuum arc, the computer simulation of vacuum arc was carried out in this paper. In the MHD model, mass conservation equation,momentum conservation equations, energy conservation equations, generalized ohm's law and Maxwell equation were considered. MHD equations were calculated by numerical method, and the distribution of vacuum arc plasma parameters and current density were obtained. Simulation results showed that the magnetic constriction effect of vacuum arc is primarily caused by the Hall effect. In addition, the inhibition of axial magnetic field (AMF) on constriction of vacuum arc was calculated and analyzed.

Vacuum fluctuations in an ancestor vacuum: A possible dark energy candidate

Science.gov (United States)

Aoki, Hajime; Iso, Satoshi; Lee, Da-Shin; Sekino, Yasuhiro; Yeh, Chen-Pin

2018-02-01

We consider an open universe created by bubble nucleation, and study possible effects of our "ancestor vacuum," a de Sitter space in which bubble nucleation occurred, on the present universe. We compute vacuum expectation values of the energy-momentum tensor for a minimally coupled scalar field, carefully taking into account the effect of the ancestor vacuum by the Euclidean prescription. We pay particular attention to the so-called supercurvature mode, a non-normalizable mode on a spatial slice of the open universe, which has been known to exist for sufficiently light fields. This mode decays in time most slowly, and may leave residual effects of the ancestor vacuum, potentially observable in the present universe. We point out that the vacuum energy of the quantum field can be regarded as dark energy if mass of the field is of order the present Hubble parameter or smaller. We obtain preliminary results for the dark energy equation of state w (z ) as a function of the redshift.

QCD contributions to vacuum polarization

International Nuclear Information System (INIS)

Reinders, L.J.; Rubinstein, H.R.; Yazaki, S.

1980-01-01

We have computed to lowest non-trivial order the perturbative and non-perturbative contributions to the vacuum polarization from all currents up to and including spin 2 ++ . These expressions are important, for example to evaluate QCD sum rules for heavy and light quark systems as shown by Shifman, Vainshtein and Zakharov. Most of the known ones are verified, one slightly changed, and many new ones are displayed. (orig.)

Current-Induced Spin Polarization at a Single Heterojunction

NARCIS (Netherlands)

Silov, A.; Blajnov, P.; Wolter, J.H.; Hey, R.; Ploog, K.; Averkiev, N.S.; Menendez, J.; Walle, van der C.G.

2005-01-01

We have experimentally achieved spin-polarization by a lateral current in a single non-magnetic semiconductor heterojunction. The effect does not require an applied magnetic field or ferromagnetic contacts. The current-induced spin orientation can be seen as the inverse of the circular

Design and performance of main vacuum pumping system of SST-1 Tokamak

Energy Technology Data Exchange (ETDEWEB)

Khan, Ziauddin, E-mail: ziauddin@ipr.res.in; Pathan, Firozkhan; George, Siju; Dhanani, Kalpesh; Paravastu, Yuvakiran; Semwal, Pratibha; Pradhan, Subrata

2014-01-15

Highlights: •SST-1 Tokamak was successfully commissioned. •Vacuum vessel and cryostat were pumped down to 6.3 × 10{sup −7} mbar and 1.3 × 10{sup −5} mbar. •Leaks developed during baking were detected in-situ by RGA and confirmed later on. •Cryo-pumping effect was observed when LN2 thermal shields reached below 273 K. •Non-standard aluminum wire-seals have shown leak tightness < 1.0 × 10{sup −9} mbar l/s. -- Abstract: Steady-state Superconducting Tokamak (SST-1) was installed and it is commissioning for overall vacuum integrity, magnet systems functionality in terms of successful cool down to 4.5 K and charging up to 10 kA current was started from August 2012. Plasma operation of 100 kA current for more than 100 ms was also envisaged. It is comprised of vacuum vessel (VV) and cryostat (CST). Vacuum vessel, an ultra-high (UHV) vacuum chamber with net volume of 23 m{sup 3} was maintained at the base pressure of 6.3 × 10{sup −7} mbar for plasma confinement. Cryostat, a high-vacuum (HV) chamber with empty volume 39 m{sup 3} housing superconducting magnet system, bubble thermal shields and hydraulics for these circuits, maintained at 1.3 × 10{sup −5} mbar in order to provide suitable environment for these components. In order to achieve these ultimate vacuums, two numbers of turbo-molecular pumps (TMP) are installed in vacuum vessel while three numbers of turbo-molecular pumps are installed in cryostat. Initial pumping of both the chambers was carried out by using suitable Roots pumps. PXI based real time controlled system is used for remote operation of the complete pumping operation. In order to achieve UHV inside the vacuum vessel, it was baked at 150 °C for longer duration. Aluminum wire-seals were used for all non-circular demountable ports and a leak tightness < 1.0 × 10{sup −9} mbar l/s were achieved.

Experimental study on 800 nm femtosecond laser ablation of fused silica in air and vacuum

Energy Technology Data Exchange (ETDEWEB)

Xu, Shi-zhen, E-mail: xusz@uestc.edu.cn [School of Physical Electronics, University of Electronic Science and Technology of China, Chengdu 610054 (China); Research Center of Laser Fusion, China Academy of Engineering Physics, Mianyang 621900 (China); Yao, Cai-zhen; Liao, Wei [Research Center of Laser Fusion, China Academy of Engineering Physics, Mianyang 621900 (China); Yuan, Xiao-dong, E-mail: yxd66my@163.com [Research Center of Laser Fusion, China Academy of Engineering Physics, Mianyang 621900 (China); Wang, Tao [School of Physical Electronics, University of Electronic Science and Technology of China, Chengdu 610054 (China); Research Center of Laser Fusion, China Academy of Engineering Physics, Mianyang 621900 (China); Zu, Xiao-tao [School of Physical Electronics, University of Electronic Science and Technology of China, Chengdu 610054 (China)

2016-10-15

Ablation rates of fused silica were studied as a function of femtosecond laser pulse fluences (0.7–41 J/cm{sup 2}) in air and vacuum. The experiment was conducted by using a Ti:sapphire laser that emits radiation at 800 nm with a pulse width of 35 fs and a repetition rate of 10 Hz. The morphology and ablation depth of laser-induced damage crater were evaluated by using optical microscopy and scanning electron microscopy (SEM). Ablation rates were calculated from the depth of craters induced by multiple laser pulses. Results showed that two ablation regimes, i.e. non-thermal and thermal ablation co-existed in air and vacuum at low and moderate fluences. A drop of ablation rate was observed at high fluence (higher than 9.5 J/cm{sup 2}) in air. While in vacuum, the ablation rate increased continuously with the increasing of laser fluence and much higher than that in air. The drop of ablation rate observed at high fluence in air was due to the strong defocusing effects associated with the non-equilibrium ionization of air. Furthermore, the laser-induced damage threshold (LIDT), which was determined from the relationship between crater area and the logarithm of laser energy, was found to depend on the number of incident pulses on the same spot, and similar phenomenon was observed in air and vacuum.

Optical binding of two microparticles levitated in vacuum

Science.gov (United States)

Arita, Yoshihiko; Wright, Ewan M.; Dholakia, Kishan

2017-04-01

Optical binding refers to an optically mediated inter-particle interaction that creates new equilibrium positions for closely spaced particles [1-5]. Optical binding of mesoscopic particles levitated in vacuum can pave the way towards the realisation of a large scale quantum bound array in cavity-optomechanics [6-9]. Recently we have demonstrated trapping and rotation of two mesoscopic particles in vacuum using a spatial-light-modulator-based approach to trap more than one particle, induce controlled rotation of individual particles, and mediate interparticle separation [10]. By trapping and rotating two vaterite particles, we observe intensity modulation of the scattered light at the sum and difference frequencies with respect to the individual rotation rates. This first demonstration of optical interference between two microparticles in vacuum has lead to a platform to explore optical binding. Here we demonstrate for the first time optically bound two microparticles mediated by light scattering in vacuum. We investigate autocorrelations between the two normal modes of oscillation, which are determined by the centre-of-mass and the relative positions of the two-particle system. In situ determination of the optical restoring force acting on the bound particles are based on measurement of the oscillation frequencies of the autocorrelation functions of the two normal modes, thereby providing a powerful and original platform to explore multiparticle entanglement in cavity-optomechanics.

HIGH PRODUCTIVITY VACUUM BLASTING SYSTEM

International Nuclear Information System (INIS)

McPhee, William S.

1999-01-01

The objective of this project is to improve the productivity and lower the expense of existing vacuum blasting technology. This technology is used to remove radioactive contamination, PCBs, and lead-based paint and provides worker protection by continuously recycling the material and dust for the decontamination tasks. The proposed work would increase the cleaning rate and provide safe and cost-effective decontamination of the DOE sites. This work focuses on redesigning and improving existing vacuum blasting technology including blast head nozzles, ergonomic handling of the blast head by reducing its weight; brush-ring design, vacuum level regulator, efficiency of the dust separator, and operational control sensors. The redesign is expected to enhance the productivity and economy of the vacuum blasting system by at least 50% over current vacuum blasting systems. There are three phases in the project. Phase I consists of developing and testing mathematical models. Phase II consists of pre-prototype design and fabrication and pre-prototype unit testing. Phase III consists of prototype design and field verification testing. In phase I, mathematical models are developed and analyzed for the nozzle, blast head, wind curtain, and dust separator, first as individual devices and then combined as an integrated model. This allows study of respective airflow and design parameters. The Contractor shall, based on the results of the mathematical modeling studies, design experimental models of the components and test these models. In addition, the Contractor shall develop sensors to detect the relationship of the blast head to the blast surfaces and controls to minimize the dependency on an operator's skill and judgment to obtain optimum positioning, as well as real-time characterization sensors to determine as the blast head is moving the depth to which coatings must be removed, thereby improving production and minimizing waste. In phase II, the Contractor shall design and

The problem with false vacuum Higgs inflation

International Nuclear Information System (INIS)

Fairbairn, Malcolm; Grothaus, Philipp; Hogan, Robert

2014-01-01

We investigate the possibility of using the only known fundamental scalar, the Higgs, as an inflaton with minimal coupling to gravity. The peculiar appearance of a plateau or a false vacuum in the renormalised effective scalar potential suggests that the Higgs might drive inflation. For the case of a false vacuum we use an additional singlet scalar field, motivated by the strong CP problem, and its coupling to the Higgs to lift the barrier allowing for a graceful exit from inflation by mimicking hybrid inflation. We find that this scenario is incompatible with current measurements of the Higgs mass and the QCD coupling constant and conclude that the Higgs can only be the inflaton in more complicated scenarios

Hamiltonian description of toroidal magnetic fields in vacuum

International Nuclear Information System (INIS)

Lewis, H.R.; Bates, J.W.

1996-01-01

An investigation of vacuum magnetic fields in toroidal geometry has been initiated. Previously, the general form of the magnetic scalar potential for fields regular at the poloidal axis was given. Here, these results have been expanded to obtain the magnetic scalar potential in a vacuum region that may surround a toroidal current distribution. Using this generalized magnetic scalar potential in conjunction with Boozer's canonical representation of a magnetic field, a field-line Hamiltonian for nonaxisymmetric vacuum fields has been derived. These fields axe being examined using a novel, open-quotes time-dependentclose quotes perturbation theory, which permits the iterative construction of invariants associated with magnetic field-line Hamiltonians that consist of an axisymmetric zeroth-order term, plus a nonaxisymmetric perturbation. By choosing appropriate independent variables, an explicit constructive procedure is developed which involves only a single canonical transformation. Such invariants are of interest because they provide a means of investigating the topology of magnetic field lines. Our objective is to elucidate the existence of magnetic surfaces for nonaxisymmetric vacuum configurations, as well as to provide an approach for studying the onset of stochastic behavior

Current-Induced Membrane Discharge

DEFF Research Database (Denmark)

Andersen, Mathias Bækbo; van Soestbergen, M.; Mani, A.

2012-01-01

. Salt depletion leads to a large electric field resulting in a local pH shift within the membrane with the effect that the membrane discharges and loses its ion selectivity. Since salt co-ions, H+ ions, and OH- ions contribute to OLC, CIMD interferes with electrodialysis (salt counterion removal...... neglects chemical effects and remains to be quantitatively tested. Here, we show that charge regulation and water self-ionization can lead to OLC by "current-induced membrane discharge'' (CIMD), even in the absence of fluid flow, in ion-exchange membranes much thicker than the local Debye screening length...

Wave-induced current considering wave-tide interaction in Haeundae

Science.gov (United States)

Lim, Hak Soo

2017-04-01

The Haeundae, located at the south eastern end of the Korean Peninsula, is a famous beach, which has an approximately 1.6 km long and 70 m wide coastline. The beach has been repeatedly eroded by the swell waves caused by typhoons in summer and high waves originating in the East Sea in winter. The Korean government conducted beach restoration projects including beach nourishment (620,000 m3) and construction of two submerged breakwaters near both ends of the beach. To prevent the beach erosion and to support the beach restoration project, the Korean government initiated a R&D project, the development of coastal erosion control technology since 2013. As a part of the project, we have been measuring waves and currents at a water depth of 22 m, 1.8 km away from the beach using an acoustic wave and current meter (AWAC) continuously for more than three years; we have also measured waves and currents intensively near the surf-zone in summer and winter. In this study, a numerical simulation using a wave and current coupled model (ROMS-SWAN) was conducted for determining the wave-induced current considering seasonal swell waves (Hs : 2.5 m, Tp: 12 s) and for better understanding of the coastal process near the surf-zone in Haeundae. By comparing the measured and simulated results, we found that cross-shore current during summer is mainly caused by the eddy produced by the wave-induced current near the beach, which in turn, is generated by the strong waves coming from the SSW and S directions. During other seasons, longshore wave-induced current is produced by the swell waves coming from the E and ESE directions. The longshore current heading west toward Dong-Back Island, west end of the beach, during all the seasons and eddy current toward Mipo-Port, east end of the beach, in summer which is well matched with the observed residual current. The wave-induced current with long-term measurement data is incorporated in simulation of sediment transport modeling for developing

A vacuum pressure sensor based on ZnO nanobelt film

International Nuclear Information System (INIS)

Zheng, X J; Cao, X C; Sun, J; Yuan, B; Zhu, Z; Zhang, Y; Li, Q H

2011-01-01

A vacuum pressure sensor was fabricated by assembling ZnO nanobelt film on the interdigital electrodes, and the current-voltage characteristics were measured with an Agilent semiconductor parameter tester. Under different pressures of 1.0 x 10 3 , 6.7 x 10 -3 , 8.2 x 10 -4 and 9.5 x 10 -5 mbar, the currents are 8.71, 28.1, 46.1 and 89.6 nA, and the pressure sensitive resistances are 1150, 356, 217 and 112 MΩ, respectively. In the range of 10 -5 -10 3 mbar the smaller the pressure is, the higher the current is. The pressure sensitive resistance of the vacuum pressure sensor increases linearly with the logarithmic pressure, and the measurement range is at least one order of magnitude wider than that of the previous sensors. Under the final pressure, the vacuum pressure sensor has maximum sensitivity (9.29) and power consumption of 0.9 μW. The sensitivity is larger than that of the previous sensor based on a ZnO single nanowire at that pressure, and the power consumption is much lower than that for the sensor based on a ZnO nanowire array. The pressure sensitive mechanism is reasonably explained by using oxygen chemisorption and energy band theory.

Current-induced energy barrier suppression for electromigration from first principles

KAUST Repository

Zhang, Ruoxing

2011-08-01

We present an efficient method for evaluating current-induced forces in nanoscale junctions, which naturally integrates into the nonequilibrium Green\\'s function formalism implemented within density functional theory. This allows us to perform dynamic atomic relaxation in the presence of an electric current while evaluating the current-voltage characteristics. The central idea consists of expressing the system energy density matrix in terms of Green\\'s functions. To validate our implementation, we perform a series of benchmark calculations, both at zero and at finite bias. First we evaluate the current-induced forces acting over an Al nanowire and compare them with previously published results for fixed geometries. Then we perform structural relaxation of the same wires under bias and determine the critical voltage at which they break. We find that although a perfectly straight wire does not break at any of the voltages considered, a zigzag wire is more fragile and snaps at 1.4 V, with the Al atoms moving against the electron flow. The critical current density for the rupture is estimated to be 9.6 × 1010 A/cm2, in good agreement with the experimentally measured value of 5 × 1010 A/cm2. Finally, we demonstrate the capability of our scheme to tackle the electromigration problem by studying the current-induced motion of a single Si atom covalently attached to the sidewall of a (4,4) armchair single-walled carbon nanotube. Our calculations indicate that if Si is attached along the current path, then current-induced forces can induce migration. In contrast, if the bonding site is away from the current path, then the adatom remains stable regardless of the voltage. An analysis based on decomposing the total force into a wind and an electrostatic component, as well as on a detailed evaluation of the bond currents, shows that this remarkable electromigration phenomenon is due solely to the position-dependent wind force. © 2011 American Physical Society.

Vacuum-assisted delivery

Science.gov (United States)

... medlineplus.gov/ency/patientinstructions/000514.htm Vacuum-assisted delivery To use the sharing features on this page, ... through the birth canal. When is Vacuum-assisted Delivery Needed? Even after your cervix is fully dilated ( ...

Realisation of a ultra-high vacuum system and technique development of microscopical emitters preparation in silicium. First measurements of field emission current and field photoemission

International Nuclear Information System (INIS)

El Manouni, A.

1990-12-01

The development of research in the domain of photocathode (electron sources) illuminated by laser light to produce intense multiple bunches of electrons in short time is needed by many applications as linear collider e + e - , free electron laser, lasertron, etc... In this way, after a study of field emission, of photoemission and of photofield emission, we prepared microscopical emitters in silicium heavy and weakly doped a boron using a technique of microlithography. Then, we realized a system of ultra-high vacuum of studying property of emission from photocathodes realized. The experiment results obtained in field emission and photofield emission have shown that a behaviour unexpected for P-silicium tips array compared to P + -silicon tips array. With P-type silicon, a quantum yield of 21 percent has been measured for laser power of 140 mW and for applied field of 1.125 x 10 7 V/m and an instantaneous response to laser light beam has been observed. It has been noted that presence of oxyde at the surface of photocathode limits extensively the emission current. The fluctuations of emission current are due to quality of vacuum [fr

R and D ERL: Vacuum

International Nuclear Information System (INIS)

Mapes, M.; Smart, L.; Weiss, D.; Steszyn, A.; Todd, R.

2010-01-01

The ERL Vacuum systems are depicted in a figure. ERL has eight vacuum volumes with various sets of requirements. A summary of vacuum related requirements is provided in a table. Five of the eight volumes comprise the electron beamline. They are the 5-cell Superconducting RF Cavity, Superconducting e-gun, injection, loop and beam dump. Two vacuum regions are the individual cryostats insulating the 5-cell Superconducting RF Cavity and the Superconducting e-gun structures. The last ERL vacuum volume not shown in the schematic is the laser transport line. The beamline vacuum regions are separated by electropneumatic gate valves. The beam dump is common with loop beamline but is considered a separate volume due to geometry and requirements. Vacuum in the 5-cell SRF cavity is maintained in the ∼10 -9 torr range at room temperature by two 20 l/s ion pumps and in the e-gun SRF cavity by one 60 l/s ion pump. Vacuum in the SRF cavities operated at 2 o K is reduced to low 10 -11 torr via cryopumping of the cavity walls. The cathode of the e-gun must be protected from poisoning, which can occur if vacuum adjacent to the e-gun in the injection line exceeds 10-11 torr range in the injection warm beamline near the e-gun exit. The vacuum requirements for beam operation in the loop and beam dump are 10-9 torr range. The beamlines are evacuated from atmospheric pressure to high vacuum level with a particulate free, oil free turbomolecular pumping cart. 25 l/s shielded ion pumps distributed throughout the beamlines maintain the vacuum requirement. Due to the more demanding vacuum requirement of the injection beamline proximate to the e-gun, a vacuum bakeout of the injection beamline is required. In addition, two 200 l/s diode ion pumps and supplemental pumping provided by titanium sublimation pumps are installed in the injection line just beyond the exit of the e-gun. Due to expected gas load a similar pumping arrangement is planned for the beam dump. The cryostat vacuum thermally

Automation of Aditya vacuum control system based on CODAC Core System

Energy Technology Data Exchange (ETDEWEB)

Raulji, Vismaysinh D., E-mail: vismay@ipr.res.in; Pujara, Harshad; Arambhadiya, Bharat; Jadeja, Kumarpalsinh; Bhatt, Shailesh; Rajpal, Rachana

2016-11-15

Highlights: • Monitor and control of vacuum control system based on CODAC Core System. • Communication between SIEMENS PLC and open source software EPICS. • With CODAC Core easy to configure and programming of slow controller. - Abstract: The main objective of vacuum control system is to provide ultrahigh vacuum for Aditya Tokamak operations. Aditya Vacuum vessel is having four vacuum pumping lines. To demonstrate implementation of automation; a study case is under taken by automating single Pumping Line of the Aditya vacuum system using CODAC Core System (CCS). Currently, vacuum system is operated manually. The CCS based control system allows remote control, monitoring, alarm handling of vacuum parameters. The CODAC Core System is the Linux based software package that is distributed by ITER Organization for the development of Plant System I&C software. CODAC Core System includes EPICS, CSS (Control System Studio) etc. CSS is used for HMI (Human Machine Interface), alarms and archives. SDD (Self Description Data) tool is used to configure plant system I&C. SDD Editor is an Eclipse based application to define the plant system, interface, I&C component, interfaced signals, configure variable. SCADA (Supervisory Control and Data Acquisition) system is developed in CSS. Data is transferred between PLC and CSS through EPICS. The complete system is tested with Aditya Vacuum Control System with process interlocks. Operator interface is also developed using Lab VIEW as a choice of the user. This paper will describe the salient features of the developed control system in detail.

Long-Term Geomagnetically Induced Current Observations From New Zealand: Peak Current Estimates for Extreme Geomagnetic Storms

Science.gov (United States)

Rodger, Craig J.; Mac Manus, Daniel H.; Dalzell, Michael; Thomson, Alan W. P.; Clarke, Ellen; Petersen, Tanja; Clilverd, Mark A.; Divett, Tim

2017-11-01

Geomagnetically induced current (GIC) observations made in New Zealand over 14 years show induction effects associated with a rapidly varying horizontal magnetic field (dBH/dt) during geomagnetic storms. This study analyzes the GIC observations in order to estimate the impact of extreme storms as a hazard to the power system in New Zealand. Analysis is undertaken of GIC in transformer number six in Islington, Christchurch (ISL M6), which had the highest observed currents during the 6 November 2001 storm. Using previously published values of 3,000 nT/min as a representation of an extreme storm with 100 year return period, induced currents of 455 A were estimated for Islington (with the 95% confidence interval range being 155-605 A). For 200 year return periods using 5,000 nT/min, current estimates reach 755 A (confidence interval range 155-910 A). GIC measurements from the much shorter data set collected at transformer number 4 in Halfway Bush, Dunedin, (HWB T4), found induced currents to be consistently a factor of 3 higher than at Islington, suggesting equivalent extreme storm effects of 460-1,815 A (100 year return) and 460-2,720 A (200 year return). An estimate was undertaken of likely failure levels for single-phase transformers, such as HWB T4 when it failed during the 6 November 2001 geomagnetic storm, identifying that induced currents of 100 A can put such transformer types at risk of damage. Detailed modeling of the New Zealand power system is therefore required to put this regional analysis into a global context.

Assessment of eddy current effects on compression experiments in the TFTR tokamak

International Nuclear Information System (INIS)

Wong, K.L.; Park, W.

1986-05-01

The eddy current induced on the TFTR vacuum vessel during compression experiments is estimated based on a cylindrical model. It produces an error magnetic field that generates magnetic islands at the rational magnetic surfaces. The widths of these islands are calculated and found to have some effect on electron energy confinement. However, resistive MHD simulation results indicate that the island formation process can be slowed down by plasma rotation

Plasma modeling of MFTF-B and the sensitivity to vacuum conditions

International Nuclear Information System (INIS)

Porter, G.D.; Rensink, M.

1984-01-01

The Mirror Fusion Test Facility (MFTF-B) is a large tandem mirror device currently under construction at Lawrence Livermore National Laboratory. The completed facility will consist of a large variety of components. Specifically, the vacuum vessel that houses the magnetic coils is basically a cylindrical vessel 60 m long and 11 m in diameter. The magnetics system consists of some 28 superconducting coils, each of which is located within the main vacuum vessel. Twenty of these coils are relatively simple solenoidal coils, but the remaining eight are of a more complicated design to provide an octupole component to certain regions of the magnetic field. The vacuum system is composed of a rough vacuum chain, used to evacuate the vessel from atmospheric pressure, and a high vacuum system, used to maintain good vacuum conditions during a plasma shot. High vacuum pumping is accomplished primarily by cryogenic panels cooled to 4.5 0 K. The MFTF-B coil set is shown together with typical axial profiles of magnetic field (a), electrostatic potential (b), and plasma density (c). The plasma is divided into nine regions axially, as labelled on the coil set in Figure 1. The central cell, which is completely azimuthally symmetric, contains a large volume plasma that is confined by a combination of the magnetic fields and the electrostatic potentials in the yin-yang cell

Motion-induced eddy current thermography for high-speed inspection

Directory of Open Access Journals (Sweden)

Jianbo Wu

2017-08-01

Full Text Available This letter proposes a novel motion-induced eddy current based thermography (MIECT for high-speed inspection. In contrast to conventional eddy current thermography (ECT based on a time-varying magnetic field created by an AC coil, the motion-induced eddy current is induced by the relative motion between magnetic field and inspected objects. A rotating magnetic field created by three-phase windings is used to investigate the heating principle and feasibility of the proposed method. Firstly, based on Faraday’s law the distribution of MIEC is investigated, which is then validated by numerical simulation. Further, experimental studies are conducted to validate the proposed method by creating rotating magnetic fields at different speeds from 600 rpm to 6000 rpm, and it is verified that rotating speed will increase MIEC intensity and thereafter improve the heating efficiency. The conclusion can be preliminarily drawn that the proposed MIECT is a platform suitable for high-speed inspection.

Probe transparency in a two-level medium embedded by a squeezed vacuum

International Nuclear Information System (INIS)

Swain, S.; Zhou, P.

1994-08-01

Effect of the detuning on the probe absorption spectra of a two-level system with and without a classically driven field in a squeezed vacuum is investigated. For a strong squeezing, there is a threshold which determines the positions and widths of the absorption peaks, for the squeezed parameter M. In a large detuning, the spectra exhibit some resemblance to the Fano spectrum. The squeezing-induced transparency occurs at the frequency 2ω L - ω A in the minimum-uncertainty squeezed vacuum. This effect is not phase-sensitive. (author). 15 refs, 8 figs

Increasing of charge of uranium ion beam in vacuum-arc-type source (MEVVA)

CERN Document Server

Kulevoj, T V; Petrenko, S V; Seleznev, D N; Pershin, V I; Batalin, V A; Kolomiets, A A

2002-01-01

Research efforts with MEVVA type source (Metal Vapor Vacuum Arc) and with its modifications are in progress now in the ITEP. In the course of research one revealed possibility to increase charge state of generated beam of uranium ions. Increase of charge results from propagation of high-current vacuum-arc charge from the source cathode to the extra anode located in increasing axial magnetic field. One obtained uranium ion beam with 150 mA output current 10% of which were contributed by U sup 7 sup + uranium ions

Vacuum considerations: summary

International Nuclear Information System (INIS)

Blechschmidt, D.; Halama, H.J.

1978-01-01

A summary is given of the efforts of a vacuum systems study group of the workshop on a Heavy Ion Demonstration Experiment (HIDE) for heavy ion fusion. An inadequate knowledge of cross-sections prevents a more concrete vacuum system design. Experiments leading to trustworthy numbers for charge exchange, stripping and capture cross-sections are badly needed and should start as soon as possible. In linacs, beam loss will be almost directly proportional to the pressure inside the tanks. The tanks should, therefore, be built in such a way that they can be baked-out in situ to improve their vacuum, especially if the cross-sections turn out to be higher than anticipated. Using standard UHV techniques and existing pumps, an even lower pressure can be achieved. The vacuum system design for circular machines will be very difficult, and in some cases, beyond the present state-of-the-art

Design for ANL 7 GeV storage ring vacuum system

International Nuclear Information System (INIS)

Wehrle, R.B.; Nielsen, R.W.

1988-01-01

The 7-GeV Advanced Photon Source (APS) design includes a storage ring having a 1060-m circumference with the capability of accommodating 34 insertion devices (ID) and their associated photon beam lines. An additional 35 photon lines can be provided from bending magnets. The vacuum system for the storage ring is designed to maintain a beam-on operating pressure of 1n Torr or less to achieve a positron beam lifetime of approximately 20 hours. The vacuum system and it's current developmental status are described

Probing the Vacuum Decay Hypothesis with Growth Function Data

Directory of Open Access Journals (Sweden)

Edésio M. Barboza

2018-02-01

Full Text Available In this paper, we present a method to probe the vacuum decay hypothesis by searching for deviations of the uncoupled dark matter density evolution formula. The method consists of expanding the dark matter density in a Taylor series and then comparing the series coefficients obtained from the observational analysis with its uncoupled values. We use the growth rate data to put constraints on the series coefficients. The results obtained are consistent with the Λ CDM model, but it is shown that the possibility of vacuum decay cannot be ruled out by current growth rate data.

Research and Development on the Storage Ring Vacuum System for the APS Upgrade Project

Energy Technology Data Exchange (ETDEWEB)

Stillwell, B.; Brajuskovic, B.; Carter, J.; Cease, H.; Lill, R.; Navrotski, G.; Noonan, J.; Suthar, K.; Walters, D.; Wiemerslage, G.; Zientek, J.; Sangroula, M.

2016-01-01

A number of research and development activities are underway at Argonne National Laboratory to build confidence in the designs for the storage ring vacuum system required for the Advanced Photon Source Up-grade project (APS-U) [1]. The predominant technical risks are: excessive residual gas pressures during operation; insufficient beam position monitor stability; excessive beam impedance; excessive heating by induced electrical surface currents; and insufficient operational reliability. Present efforts to mitigate these risks include: building and evaluating mockup assemblies; performing mechanical testing of chamber weld joints; developing computational tools; investigating design alternatives; and performing electrical bench measurements. Status of these activities and some of what has been learned to date will be shared.

Modern vacuum physics

CERN Document Server

Chambers, Austin

2005-01-01

Modern Vacuum Physics presents the principles and practices of vacuum science and technology along with a number of applications in research and industrial production. The first half of the book builds a foundation in gases and vapors under rarefied conditions, The second half presents examples of the analysis of representative systems and describes some of the exciting developments in which vacuum plays an important role. The final chapter addresses practical matters, such as materials, components, and leak detection. Throughout the book, the author''s explanations are presented in terms of first principles and basic physics, augmented by illustrative worked examples and numerous figures.

Gravitation and vacuum field

International Nuclear Information System (INIS)

Tevikyan, R.V.

1986-01-01

This paper presents equations that describe particles with spins s = 0, 1/2, 1 completely and which also describe 2s + 2 limiting fields as E → ∞. It is shown that the ordinary Hilbert-Einstein action for the gravitation field must be augmented by the action for the Bose vacuum field. This means that one must introduce in the gravitational equations a cosmological term proportional to the square of the strength of the Bose vacuum field. It is shown that the theory of gravitation describes three realities: matter, field, and vacuum field. A new form of matter--the vacuum field--is introduced into field theory

Surge-damping vacuum valve

International Nuclear Information System (INIS)

Bullock, J.C.; Kelley, B.E.

1977-01-01

A valve for damping out flow surges in a vacuum system is described. The surge-damping mechanism consists of a slotted, spring-loaded disk adjacent to the valve's vacuum port (the flow passage to the vacuum roughing pump). Under flow surge conditions, the differential pressure forces the disk into a sealing engagement with the vacuum port, thereby restricting the gas flow path to narrow slots in the disk's periphery. The increased flow damps out the flow surge. When pressure is equalized on both sides of the valve, the spring load moves the disk away from the port to restore full flow conductance through the valve

arXiv Analytical methods for vacuum simulations in high energy accelerators for future machines based on LHC performances

CERN Document Server

Aichinger, Ida; Chiggiato, Paolo

The Future Circular Collider (FCC), currently in the design phase, will address many outstanding questions in particle physics. The technology to succeed in this 100 km circumference collider goes beyond present limits. Ultra-high vacuum conditions in the beam pipe is one essential requirement to provide a smooth operation. Different physics phenomena as photon-, ion- and electron- induced desorption and thermal outgassing of the chamber walls challenge this requirement. This paper presents an analytical model and a computer code PyVASCO that supports the design of a stable vacuum system by providing an overview of all the gas dynamics happening inside the beam pipes. A mass balance equation system describes the density distribution of the four dominating gas species $\\text{H}_2, \\text{CH}_4$, $\\text{CO}$ and $\\text{CO}_2$. An appropriate solving algorithm is discussed in detail and a validation of the model including a comparison of the output to the readings of LHC gauges is presented. This enables the eval...

Comparison of vacuum rise time, vacuum limit accuracy, and occlusion break surge of 3 new phacoemulsification systems.

Science.gov (United States)

Han, Young Keun; Miller, Kevin M

2009-08-01

To compare vacuum rise time, vacuum limit accuracy, and occlusion break surge of 3 new phacoemulsification machines. Jules Stein Eye Institute and Department of Ophthalmology, David Geffen School of Medicine at UCLA, Los Angeles, California, USA. The vacuum rise time under normal and enhanced aspiration modes, vacuum limit accuracy, and occlusion break surge of the Infiniti Vision System, Stellaris Vision Enhancement System, and WhiteStar Signature Phacoemulsification System were tested. Vacuum rise time and limit accuracy were measured at limit settings of 400 mm Hg and 600 mm Hg. Surge area was recorded at vacuum limit settings of 200 mm Hg, 300 mm Hg, 400 mm Hg, and 500 mm Hg. The Infiniti had the fastest vacuum rise times under normal and enhanced aspiration modes. At 4 seconds, the vacuum limit accuracy was greatest with the Infiniti at the 400 mm Hg limit and the Signature at the 600 mm Hg limit. The Stellaris did not reach either vacuum target. The Infiniti performed better than the other 2 machines during testing of occlusion break surge at all vacuum limit settings above 200 mm Hg. Under controlled laboratory test conditions, the Infiniti had the fastest vacuum rise time, greatest vacuum limit accuracy at 400 mm Hg, and least occlusion break surge. These results can be explained by the lower compliance of the Infiniti system.

Current-induced forces: a new mechanism to induce negative differential resistance and current-switching effect in molecular junctions

Science.gov (United States)

Gu, Lei; Fu, Hua-Hua

2015-12-01

Current-induced forces can excite molecules, polymers and other low-dimensional materials, which in turn leads to an effective gate voltage through Holstein interaction. Here, by taking a short asymmetric DNA junction as an example, and using the Langevin approach, we find that when suppression of charge transport by the effective gate voltage surpasses the current increase from an elevated voltage bias, the current-voltage (I-V) curves display strong negative differential resistance (NDR) and perfect current-switching characteristics. The asymmetric DNA chain differs in mechanical stability under inverse voltages and the I-V curve is asymmetric about inverse biases, which can be used to understand recent transport experiments on DNA chains, and meanwhile provides a new strategy to realize NDR in molecular junctions and other low-dimensional quantum systems.

Current-induced forces: a new mechanism to induce negative differential resistance and current-switching effect in molecular junctions

International Nuclear Information System (INIS)

Gu, Lei; Fu, Hua-Hua

2015-01-01

Current-induced forces can excite molecules, polymers and other low-dimensional materials, which in turn leads to an effective gate voltage through Holstein interaction. Here, by taking a short asymmetric DNA junction as an example, and using the Langevin approach, we find that when suppression of charge transport by the effective gate voltage surpasses the current increase from an elevated voltage bias, the current-voltage (I–V) curves display strong negative differential resistance (NDR) and perfect current-switching characteristics. The asymmetric DNA chain differs in mechanical stability under inverse voltages and the I–V curve is asymmetric about inverse biases, which can be used to understand recent transport experiments on DNA chains, and meanwhile provides a new strategy to realize NDR in molecular junctions and other low-dimensional quantum systems. (paper)

Radiation-induced off-state leakage current in commercial power MOSFETs

International Nuclear Information System (INIS)

Dodd, Paul Emerson; Shaneyfelt, Marty Ray; Draper, Bruce Leroy; Felix, James Andrew; Schwank, James Ralph; Dalton, Scott Matthew

2005-01-01

The total dose hardness of several commercial power MOSFET technologies is examined. After exposure to 20 krad(SiO 2 ) most of the n- and p-channel devices examined in this work show substantial (2 to 6 orders of magnitude) increases in off-state leakage current. For the n-channel devices, the increase in radiation-induced leakage current follows standard behavior for moderately thick gate oxides, i.e., the increase in leakage current is dominated by large negative threshold voltage shifts, which cause the transistor to be partially on even when no bias is applied to the gate electrode. N-channel devices biased during irradiation show a significantly larger leakage current increase than grounded devices. The increase in leakage current for the p-channel devices, however, was unexpected. For the p-channel devices, it is shown using electrical characterization and simulation that the radiation-induced leakage current increase is related to an increase in the reverse bias leakage characteristics of the gated diode which is formed by the drain epitaxial layer and the body. This mechanism does not significantly contribute to radiation-induced leakage current in typical p-channel MOS transistors. The p-channel leakage current increase is nearly identical for both biased and grounded irradiations and therefore has serious implications for long duration missions since even devices which are usually powered off could show significant degradation and potentially fail.

The physics of ''vacuum'' breakdown

International Nuclear Information System (INIS)

Schwirzke, F.

1993-01-01

Many discharges form small cathode spots which provide such a high energy density that the cathode material explodes into a dense plasma cloud within a very short time. Despite the fundamental importance of cathode spots for the breakdown process and the formation of a discharge, the structure of the cathode spot plasma and the source of the high energy density were not yet well defined. One model, the whisker explosive emission model, assumes that joule heating by field emitted electrons provides the energy. Current densities of j FE = 10 12 - 10 13 A/m 2 would be required. However, the pre-breakdown j FE is self-limiting. The negative space charge caused by j FE in the cathode-anode gap reduces the effective electric field E on the cathode surface. The maximum current density j CL is space charge limited by Child-Langmuir's law. The field emitting spot cannot deliver j CL without turning itself off, since the negative space charge caused by j CL reduces E congruent 0 at the cathode surface. Hence, it must be that the vacuum j FE CL . The development of a current with j > j FE (vacuum) requires that ions exist in front of the electron emitting spot. Ions cannot be emitted from the surface of the field emitting spot, the enhanced electric field would hold them back. The initial ionization must occur in the cathode-anode gap near the electron emitting spot. Ionization of desorbed neutrals provides the mechanism. This ionization process requires considerably less current than the ionization of solid material by joule heating. Field emission and the impact of ions stimulate desorption of weakly bound adsorbates from the surface of the electron emitting spot. The cross section for ionization of the neutrals has a maximum for ∼ 100 eV electrons

Economical evaluation of damaged vacuum insulation panels in buildings

Science.gov (United States)

Kim, Y. M.; Lee, H. Y.; Choi, G. S.; Kang, J. S.

2015-12-01

In Korea, thermal insulation standard of buildings have been tightened annually to satisfy the passive house standard from the year 2009. The current domestic policies about disseminating green buildings are progressively conducted. All buildings should be the zero energy building in the year 2025, obligatorily. The method is applied to one of the key technologies for high-performance insulation for zero energy building. The vacuum insulation panel is an excellent high performance insulation. But thermal performance of damaged vacuum insulation panels is reduced significantly. In this paper, the thermal performance of damaged vacuum insulation panels was compared and analyzed. The measurement result of thermal performance depends on the core material type. The insulation of building envelope is usually selected by economic feasibility. To evaluate the economic feasibility of VIPs, the operation cost was analyzed by simulation according to the types and damaged ratio of VIPs

Vacuum type D initial data

Science.gov (United States)

García-Parrado Gómez-Lobo, Alfonso

2016-09-01

A vacuum type D initial data set is a vacuum initial data set of the Einstein field equations whose data development contains a region where the space–time is of Petrov type D. In this paper we give a systematic characterisation of a vacuum type D initial data set. By systematic we mean that the only quantities involved are those appearing in the vacuum constraints, namely the first fundamental form (Riemannian metric) and the second fundamental form. Our characterisation is a set of conditions consisting of the vacuum constraints and some additional differential equations for the first and second fundamental forms These conditions can be regarded as a system of partial differential equations on a Riemannian manifold and the solutions of the system contain all possible regular vacuum type D initial data sets. As an application we particularise our conditions for the case of vacuum data whose data development is a subset of the Kerr solution. This has applications in the formulation of the nonlinear stability problem of the Kerr black hole.

Vacuum pumping concepts for ETF

International Nuclear Information System (INIS)

Homeyer, W.G.

1980-09-01

The Engineering Test Facility (ETF) poses unique vacuum pumping requirements due to its large size and long burn characteristics. These requirements include torus vacuum pumping initially and between burns and pumping of neutralized gas from divertor collector chambers. It was found that the requirements could be met by compound cryopumps in which molecular sieve 5A is used as the cryosorbent. The pumps, ducts, and vacuum valves required are large but fit with other ETF components and do not require major advances in vacuum pumping technology. Several additional design, analytical, and experimental studies were identified as needed to optimize designs and provide better design definition for the ETF vacuum pumping systems

Structure of Nonlocal quark vacuum condensate in non-perturbative QCD vacuum

International Nuclear Information System (INIS)

Xiang Qianfei; Ma Weixing; Zhou Lijuan; Jiang Weizhou

2014-01-01

Based on the Dyson-Schwinger Equations (DSEs) with the rainbow truncation, and Operator Product Expansion, the structure of nonlocal quark vacuum condensate in QCD, described by quark self-energy functions A_f and B_f given usually by the solutions of the DSEs of quark propagator, is predicted numerically. We also calculate the local quark vacuum condensate, quark-gluon mixed local vacuum condensate, and quark virtuality. The self-energy functions A_f and B_f are given by the parameterized quark propagator functions σ_v"f (p"2) and σ_s"f (p"2) of Roberts and Williams, instead of the numerical solutions of the DSEs. Our calculated results are in reasonable agreement with those of QCD sum rules, Lattice QCD calculations, and instanton model predictions, although the resulting local quark vacuum condensate for light quarks, u, d, s, are a little bit larger than those of the above theoretical predictions. We think the differences are caused by model dependence. The larger of strange quark vacuum condensate than u, d quark is due to the s quark mass which is more larger than u, d quark masses. Of course, the Roberts-Williams parameterized quark propagator is an empirical formulism, which approximately describes quark propagation. (authors)

Tests of a vacuum breaker for the FTU commutation system

International Nuclear Information System (INIS)

Andreani, R.; Lovisetto, L.; Cornago, F.

1984-01-01

A two poles vacuum breaker, equipped with saturable inductances and capacitor banks to produce an artificial current zero, appears the most suitable solution to satisfy these requirements with high reliability of operation and limited maintenance. Two series of tests have been conducted to evaluate the performance and reliability of the system and in particular the erosion of the electrodes as a function of number of operations. The test results have been very satisfactory. At least 1000 full power pulses can be envisaged before replacing the vacuum bottles. (author)

Nonconservative current-induced forces: A physical interpretation

Directory of Open Access Journals (Sweden)

Tchavdar N. Todorov

2011-10-01

Full Text Available We give a physical interpretation of the recently demonstrated nonconservative nature of interatomic forces in current-carrying nanostructures. We start from the analytical expression for the curl of these forces, and evaluate it for a point defect in a current-carrying system. We obtain a general definition of the capacity of electrical current flow to exert a nonconservative force, and thus do net work around closed paths, by a formal noninvasive test procedure. Second, we show that the gain in atomic kinetic energy over time, generated by nonconservative current-induced forces, is equivalent to the uncompensated stimulated emission of directional phonons. This connection with electron–phonon interactions quantifies explicitly the intuitive notion that nonconservative forces work by angular momentum transfer.

Vacuum in the presence of electromagnetic fields and rotating boundaries

International Nuclear Information System (INIS)

Manogue, C.A.

1984-01-01

Two investigations of the properties of the vacuum are made. The first is a reconsideration of the classic Klein paradox, particle creation due to the presence of very strong external electromagnetic potentials. Expectation values of the current, momentum, and number operators, each of which is a measure of particle creation, are calculated for both massive spin zero and massive spin one half fields. The relationship between super-radiance and pair creation is explained. A review of past work by other authors is included and common conceptual errors are pointed out. The second investigation concerns the rotation of the vacuum caused by the rotation of boundaries. Just as the presence of boundaries can create a change in the vacuum expectation value of the energy density (the Casimir effect), the rotation of such boundaries can create changes in the vacuum expectation value of the momentum density. Calculations of the Casimir effect are made for a massless scalar field confined to an infinitely long square box. The change in the vacuum expectation value of the momentum density is calculated if this same box is rotating around its long central axis. In contrast, it is shown that for an infinitely long circular cylinder there is no change in the momentum density

Spent Nuclear Fuel Cold Vacuum Drying facility comprehensive formal design review report

International Nuclear Information System (INIS)

HALLER, C.S.

1999-01-01

The majority of the Cold Vacuum Drying Facility (CVDF) design and construction is complete; isolated portions are still in the design and fabrication process. The project commissioned a formal design review to verify the sufficiency and accuracy of current design media to assure that: (1) the design completely and accurately reflects design criteria, (2) design documents are consistent with one another, and (3) the design media accurately reflects the current design. This review is a key element in the design validation and verification activities required by SNF-4396, ''Design Verification and Validation Plan For The Cold Vacuum Drying Facility''. This report documents the results of the formal design review

A low loss Faraday isolator for squeezed vacuum injection in Advanced LIGO

Science.gov (United States)

Goetz, Ryan; Tanner, David; Mueller, Guido

2016-03-01

Using conventional interferometry, the strain sensitivity of Advanced LIGO is limited by a quantum noise floor known as the standard quantum limit (SQL). Injecting squeezed vacuum states into the output port of the interferometer allows for detector sensitivities below the SQL at frequencies within a band of observational interest. The effectiveness of squeezing in reducing quantum noise is strongly dependent upon the optical loss in the squeezed path. Thus, to combine the squeezed vacuum state with the interferometer output we require a Faraday isolator with both high power-throughput efficiency and high isolation ratio. A prototype isolator is currently being developed, and we will discuss the design goals and current status.

Safety considerations to avoid current-induced skin burns in MRI

International Nuclear Information System (INIS)

Knopp, M.V.; Metzner, R.; Kaick, G. van; Brix, G.; Bundesamt fuer Strahlenschutz, Oberschleissheim

1998-01-01

The safety aspects of radiological methods continue to evolve. In this paper we report on two cases of skin burns in MRI caused by induced electrical current. A second- and a third-degree skin burn occurred during imaging in a 1.5 T system. The electromagnetic radiofrequency field inadvertently led to electrical currents caused by a conducting loop through the extremities and trunk. Skin burns induced by electrical current may occur in extremely rare cases even with standard MR imaging protocols operating within all current safety guidelines by inadvertently forming a closed conducting loop. By avoiding focal skin to skin contact of the extremities, this extremely rare adverse event can be avoided. (orig.) [de

Simulation study of induced EMFs and the suppression during SST-1 start-up

Energy Technology Data Exchange (ETDEWEB)

Jain, V., E-mail: vishal@ipr.res.in; Sharma, D.; Vardhrajulu, A.; Gupta, C.N.; Srinivasan, R.; Daniel, R.

2015-11-15

Highlights: • Induced EMFs study in PF coils during SST-1 start up using MATlab simulink. • Integration of wave shaping network to generate practical OT current profile. • This study would protect coil insulation with identifying RC circulating network. • Study of MOV technique for circulation of current through RC. - Abstract: Steady State Superconducting Tokamak (SST-1) comprises of various copper and superconducting coils for generating magnetic field for initiation, providing equilibrium and shaping of plasma in tokamak. In this paper, an attempt is made to study the induced EMF in superconducting poloidal field coils (PF coils) due to fast ramp down of current in ohmic transformer copper coils (OT coils) for SST-1 plasma initiation. The fast ramp down of current, from few kA to zero amperes in just 50–100 ms in OT coils, is required to achieve plasma breakdown and ramp up of plasma current in tokamak. However, it induces nearly 5 kV EMF in one of the SST-1 PF coils that can damage the coil insulation and also bias negatively the electronic switching of power supply. It is necessary to maintain induced EMF below 1 kV in all PF coils for safe operation of SST-1. The induced EMF up to 1 kV can be clamped without any need of protection and circulating current. If the induced EMF is in excess of 1 kV, then it has to allow the circulation of current through RC network for coil protection from overvoltage. These circulating currents in PF coils will affect the shaping of plasma. In this paper, the induced EMF in PF coils are simulated using MATlab simulink for a typical SST-1 current profile of OT coils. Further, this simulation study is used to design the protection system for PF coils. In this paper, the worst-case induced EMF scenario is considered by excluding the effect of passive elements like vacuum vessel and cryostat on mutual coupling parameters. However, the implementation of the EMF suppression scheme need more elaborated study with considering

Vacuum-Flex Figuring of Primary Telescope Mirrors

Science.gov (United States)

Albin, E. F. M.

2004-12-01

In the current investigation, details on the construction and performance of a vacuum-flexed (i.e., figured) 51 cm (20-inch) mirror, with a fast f/4 focal ratio, are presented. A vacuum has the chief advantage of being able to pull with a uniform or isotropic stress across a large surface area, which will naturally form a parabolic surface. The essence of the idea is to grind and polish a spherical mirror and then warp or flex it into a near perfect paraboloid, thus avoiding tedious figuring altogether. To date, telescope makers around the globe have experimented with small flexed mirrors with considerable success. In these instances, mirrors have been flexed by exerting tension on a bolt or sponge-pad adhered to the back of the mirror. The prototype mirror consists of two 51 cm disks of plate glass -- each slumped to an f/4 focal ratio. The front-plate (19 mm in thickness) is separated from the back-plate (13 mm in thickness) back a flexible 9.5 mm air filled gasket. Although the rubber gasket makes a fairly good vacuum seal, silicon cement was placed about the outer edge in order to produce a perfectly tight seal. A vacuum of 8 kPa on the back of the mirror resulted in approximately 164 kilograms of negative pressure, which is required to flex the mirror into the required paraboloid. Ronchi test show a nice smooth paraboloid free from astigmatism while foucault zonal measurements display a figure better than 1/20 wave. Preliminary star testing show promising results as well. Vacuum-flexed mirrors may have benefits for both amateur and professional telescope makers alike. A US patent is pending on the aforementioned design.

Shiva and Argus target diagnostics vacuum systems

International Nuclear Information System (INIS)

Glaros, S.S.; Mayo, S.E.; Campbell, D.; Holeman, D.

1978-09-01

The normal operation of LLL's Argus and Shiva laser irradiation facilities demand a main vacuum system for the target chamber and a separate local vacuum system for each of the larger appendage dianostics. This paper will describe the Argus and Shiva main vacuum systems, their respective auxiliary vacuum systems and the individual diagnostics with their respective special vacuum requirements and subsequent vacuum systems. Our latest approach to automatic computer-controlled vacuum systems will be presented

CERN Vacuum-System Activities during the Long Shutdown 1: The LHC Beam Vacuum

CERN Document Server

Baglin, V; Chiggiato, P; Jimenez, JM; Lanza, G

2014-01-01

After the Long Shutdown 1 (LS1) and the consolidation of the magnet bus bars, the CERN Large Hadron Collider (LHC) will operate with nominal beam parameters. Larger beam energy, beam intensities and luminosity are expected. Despite the very good performance of the beam vacuum system during the 2010-12 physics run (Run 1), some particular areas require attention for repair, consolidation and upgrade. Among the main activities, a large campaign aiming at the repair of the RF bridges of some vacuum modules is conducted. Moreover, consolidation of the cryogenic beam vacuum systems with burst disk for safety reasons is implemented. In addition, NEG cartridges, NEG coated inserts and new instruments for the vacuum system upgrade are installed. Besides these activities, repair, consolidation and upgrades of other beam equipment such as collimators, kickers and beam instrumentations are carried out. In this paper, the motivation and the description for such activities, together with the expected beam vacuum performa...

Effects of vacuum annealing on the optical and electrical properties of p-type copper-oxide thin-film transistors

International Nuclear Information System (INIS)

Sohn, Joonsung; Song, Sang-Hun; Kwon, Hyuck-In; Nam, Dong-Woo; Cho, In-Tak; Lee, Jong-Ho; Cho, Eou-Sik

2013-01-01

We have investigated the effects of vacuum annealing on the optical and electrical properties of the p-type copper-oxide thin-film transistors (TFTs). The vacuum annealing of the copper-oxide thin-film was performed using the RF magnetron sputter at various temperatures. From the x-ray diffraction and UV-vis spectroscopy, it is demonstrated that the high-temperature vacuum annealing reduces the copper-oxide phase from CuO to Cu 2 O, and increases the optical transmittance in the visible part of the spectrum. The fabricated copper-oxide TFT does not exhibit the switching behavior under low-temperature vacuum annealing conditions. However, as the annealing temperature increases, the drain current begins to be modulated by a gate voltage, and the TFT exhibits a high current on–off ratio over 10 4 as the vacuum annealing temperature increases over 450 °C. These results show that the vacuum annealing process can be an effective method of simultaneously improving the optical and electrical performances in p-type copper-oxide TFTs. (paper)

The AGS Booster vacuum systems

International Nuclear Information System (INIS)

Hseuh, H.C.

1989-01-01

The AGS Booster is a synchrotron for the acceleration of both protons and heavy ions. The design pressure of low 10 -11 mbar is required to minimize beam loss of the partially stripped heavy ions. To remove contaminants and to reduce outgassing, the vacuum chambers and the components located in them will be chemically cleaned, vacuum fired, baked then treated with nitric oxide. The vacuum sector will be insitu baked to a minimum of 200 degree C and pumped by the combination of sputter ion pumps and titanium sublimation pumps. This paper describes the design and the processing of this ultra high vacuum system, and the performance of some half-cell vacuum chambers. 9 refs., 7 figs

Vacuum design for a superconducting mini-collider

International Nuclear Information System (INIS)

Barletta, W.A.; Monteiro, S.

1991-01-01

The phi factory (Superconducting Mini-Collider or SMC) proposed for construction at UCLA is a single storage ring with circulating currents of 2 A each of electrons and positrons. The small circumference exacerbates the difficulties of handling the gas load due to photodesorption from the chamber walls. The authors analyze the vacuum system for the phi factory to specify design choices

Vacuum space charge effects in sub-picosecond soft X-ray photoemission on a molecular adsorbate layer.

Science.gov (United States)

Dell'Angela, M; Anniyev, T; Beye, M; Coffee, R; Föhlisch, A; Gladh, J; Kaya, S; Katayama, T; Krupin, O; Nilsson, A; Nordlund, D; Schlotter, W F; Sellberg, J A; Sorgenfrei, F; Turner, J J; Öström, H; Ogasawara, H; Wolf, M; Wurth, W

2015-03-01

Vacuum space charge induced kinetic energy shifts of O 1s and Ru 3d core levels in femtosecond soft X-ray photoemission spectra (PES) have been studied at a free electron laser (FEL) for an oxygen layer on Ru(0001). We fully reproduced the measurements by simulating the in-vacuum expansion of the photoelectrons and demonstrate the space charge contribution of the high-order harmonics in the FEL beam. Employing the same analysis for 400 nm pump-X-ray probe PES, we can disentangle the delay dependent Ru 3d energy shifts into effects induced by space charge and by lattice heating from the femtosecond pump pulse.

Explaining Electromagnetic Plane Waves in a Vacuum at the Introductory Level

Science.gov (United States)

Allred, Clark L.; Della-Rose, Devin J.; Flusche, Brian M.; Kiziah, Rex R.; Lee, David J.

2010-01-01

A typical introduction to electromagnetic waves in vacuum is illustrated by the following quote from an introductory physics text: "Maxwell's equations predict that an electromagnetic wave consists of oscillating electric and magnetic fields. The changing fields induce each other, which maintains the propagation of the wave; a changing electric…

The symmetries of the vacuum

International Nuclear Information System (INIS)

Fleming, H.

1985-01-01

The vacuum equation of state required by cosmological inflation is taken seriously as a general property of the cosmological vacuum. This correctly restricts the class of theories which admit inflation. A model of such a vacuum is presented that leads naturally to the cosmological principle. (Author) [pt

Regulating vacuum pump speed with feedback control

International Nuclear Information System (INIS)

Ludington, D.C.; Aneshansley, D.J.; Pellerin, R.; Guo, F.

1992-01-01

Considerable energy is wasted by the vacuum pump/motor on dairy farms. The output capacity (m 3 /min or cfm) of the vacuum pump always exceeds the capacity needed to milk cows and wash pipelines. Vacuum pumps run at full speed and load regardless of actual need for air. Excess air is admitted through a controller. Energy can be saved from electrical demand reduced by regulating vacuum pump speed according to air based on air usage. An adjustable speed drive (ASD) on the motor and controlled based upon air usage, can reduce the energy used by the vacuum pump. However, the ASD unit tested could not maintain vacuum levels within generally accepted guidelines when air usage changed. Adding a high vacuum reserve and a dual vacuum controller between the vacuum pump and the milking pipeline brought vacuum stability within guidelines. The ASD/dual vacuum system can reduce energy consumption and demand by at least 50 percent during milking and provide better vacuum stability than conventional systems. Tests were not run during washing cycles. Using 1990 costs and only the energy saved during milking, the simple payback on investment in new equipment for a 5 hp motor, speed controller and vacuum regulator would be about 5 years

The Source of the Quantum Vacuum

Directory of Open Access Journals (Sweden)

Daywitt W. C.

2009-01-01

Full Text Available The quantum vacuum consists of virtual particles randomly appearing and disappearing in free space. Ordinarily the wavenumber (or frequency spectrum of the zero-point fields for these virtual particles is assumed to be unbounded. The unbounded nature of the spectrum leads in turn to an infinite energy density for the quantum vacuum and an infinite renormalization mass for the free particle. This paper argues that there is a more fundamental vacuum state, the Planck vacuum, from which the quantum vacuum emerges and that the “graininess” of this more fundamental vacuum state truncates the wavenumber spectrum and leads to a finite energy density and a finite renormalization mass.

The Source of the Quantum Vacuum

Directory of Open Access Journals (Sweden)

Daywitt W. C.

2009-01-01

Full Text Available The quantum vacuum consists of virtual particles randomly appearing and disappearing in free space. Ordinarily the wavenumber (or frequency spectrum of the zero-point fields for these virtual particles is assumed to be unbounded. The unbounded nature of the spectrum leads in turn to an infinite energy density for the quantum vacuum and an infinite renormalization mass for the free particle. This paper argues that there is a more fundamental vacuum state, the Planck vacuum, from which the quantum vacuum emerges and that the "graininess" of this more fundamental vacuum state truncates the wavenumber spectrum and leads to a finite energy density and a finite renormalization mass.

Discharge behavior of vacuum arc ion source working in pulse mode

International Nuclear Information System (INIS)

Tang Pingying; Dai Jingyi; Tan Xiaohua; Jin Dazhi; Liu Tie; Ding Bonan

2005-01-01

Discharge behavior of the vacuum arc ion source working in pulse mode was investigated using high-speed photography and spectrum diagnosis. The evolvement of cathode spot on hydrogen-impregnated electrode was captured by high-speed photography, and the emission spectra of cathode spot at different pulse currents were analyzed. The experimental results show that in most cases, only one cathode spot can be found in the discharge zone of vacuum arc ion source, and the spot moves a little during the same discharge. Temperature of the cathode spot may rise while the discharge current increases, and ultimately the density of hydrogen ion will be increased. At the same time, sputtering of the electrode is enhanced and the quality of ion plasma will be reduced. (authors)

Vacuum Bloch-Siegert shift in Landau polaritons with ultra-high cooperativity

Science.gov (United States)

Li, Xinwei; Bamba, Motoaki; Zhang, Qi; Fallahi, Saeed; Gardner, Geoff C.; Gao, Weilu; Lou, Minhan; Yoshioka, Katsumasa; Manfra, Michael J.; Kono, Junichiro

2018-06-01

A two-level system resonantly interacting with an a.c. magnetic or electric field constitutes the physical basis of diverse phenomena and technologies. However, Schrödinger's equation for this seemingly simple system can be solved exactly only under the rotating-wave approximation, which neglects the counter-rotating field component. When the a.c. field is sufficiently strong, this approximation fails, leading to a resonance-frequency shift known as the Bloch-Siegert shift. Here, we report the vacuum Bloch-Siegert shift, which is induced by the ultra-strong coupling of matter with the counter-rotating component of the vacuum fluctuation field in a cavity. Specifically, an ultra-high-mobility two-dimensional electron gas inside a high-Q terahertz cavity in a quantizing magnetic field revealed ultra-narrow Landau polaritons, which exhibited a vacuum Bloch-Siegert shift up to 40 GHz. This shift, clearly distinguishable from the photon-field self-interaction effect, represents a unique manifestation of a strong-field phenomenon without a strong field.

Current-induced torques and interfacial spin-orbit coupling

KAUST Repository

Haney, Paul M.; Lee, Hyun-Woo; Lee, Kyung-Jin; Manchon, Aurelien; Stiles, M. D.

2013-01-01

In bilayer systems consisting of an ultrathin ferromagnetic layer adjacent to a metal with strong spin-orbit coupling, an applied in-plane current induces torques on the magnetization. The torques that arise from spin-orbit coupling are of particular interest. Here we use first-principles methods to calculate the current-induced torque in a Pt-Co bilayer to help determine the underlying mechanism. We focus exclusively on the analog to the Rashba torque, and do not consider the spin Hall effect. The details of the torque depend strongly on the layer thicknesses and the interface structure, providing an explanation for the wide variation in results found by different groups. The torque depends on the magnetization direction in a way similar to that found for a simple Rashba model. Artificially turning off the exchange spin splitting and separately the spin-orbit coupling potential in the Pt shows that the primary source of the “fieldlike” torque is a proximate spin-orbit effect on the Co layer induced by the strong spin-orbit coupling in the Pt.

Current-induced torques and interfacial spin-orbit coupling

KAUST Repository

Haney, Paul M.

2013-12-19

In bilayer systems consisting of an ultrathin ferromagnetic layer adjacent to a metal with strong spin-orbit coupling, an applied in-plane current induces torques on the magnetization. The torques that arise from spin-orbit coupling are of particular interest. Here we use first-principles methods to calculate the current-induced torque in a Pt-Co bilayer to help determine the underlying mechanism. We focus exclusively on the analog to the Rashba torque, and do not consider the spin Hall effect. The details of the torque depend strongly on the layer thicknesses and the interface structure, providing an explanation for the wide variation in results found by different groups. The torque depends on the magnetization direction in a way similar to that found for a simple Rashba model. Artificially turning off the exchange spin splitting and separately the spin-orbit coupling potential in the Pt shows that the primary source of the “fieldlike” torque is a proximate spin-orbit effect on the Co layer induced by the strong spin-orbit coupling in the Pt.

Scroll vacuum pump

Energy Technology Data Exchange (ETDEWEB)

Morishita, Etsuo; Suganami, Takuya; Nishida, Mitsuhiro; Kitora, Yoshihisa; Yamamoto, Sakuei; Fujii, Kosaburo

1988-02-25

An effort is made to apply a scroll machine to development of a vacuum pump. In view of mechanical simplification and load patterns, the vacuum pump uses a rotating mechanism to produce paired vortices rotating around each center. Chip seal and atmospheric pressure are utilized for axial gap sealing while a spring and atmospheric pressure for the radial gap sealing. In both gaps, the sealing direction is stationary relative to the environment during rotation, making it much easier to achieve effective sealing as compared to oscillating pumps. Since the compression ratio is high in vacuum pumps, a zero top clearance form is adopted for the central portion of vortices and an gas release valve is installed in the rotating axis. A compact Oldham coupling with a small inertia force is installed behind the vortices to maintain the required phase relations between the vortices. These improvements result in a vacuum of 1 Pa for dry operation and 10/sup -2/ Pa for oil flooded operation of a single-stage scroll machine at 1800 rpm. (5 figs, 1 tab, 4 refs)

Cosmological constant problem and renormalized vacuum energy density in curved background

Energy Technology Data Exchange (ETDEWEB)

Kohri, Kazunori [Theory Center, IPNS, KEK, Tsukuba 305-0801, Ibaraki (Japan); Matsui, Hiroki, E-mail: kohri@post.kek.jp, E-mail: matshiro@post.kek.jp [The Graduate University of Advanced Studies (Sokendai), Tsukuba 305-0801, Ibaraki (Japan)

2017-06-01

The current vacuum energy density observed as dark energy ρ{sub dark}≅ 2.5×10{sup −47} GeV{sup 4} is unacceptably small compared with any other scales. Therefore, we encounter serious fine-tuning problem and theoretical difficulty to derive the dark energy. However, the theoretically attractive scenario has been proposed and discussed in literature: in terms of the renormalization-group (RG) running of the cosmological constant, the vacuum energy density can be expressed as ρ{sub vacuum}≅ m {sup 2} H {sup 2} where m is the mass of the scalar field and rather dynamical in curved spacetime. However, there has been no rigorous proof to derive this expression and there are some criticisms about the physical interpretation of the RG running cosmological constant. In the present paper, we revisit the RG running effects of the cosmological constant and investigate the renormalized vacuum energy density in curved spacetime. We demonstrate that the vacuum energy density described by ρ{sub vacuum}≅ m {sup 2} H {sup 2} appears as quantum effects of the curved background rather than the running effects of cosmological constant. Comparing to cosmological observational data, we obtain an upper bound on the mass of the scalar fields to be smaller than the Planck mass, m ∼< M {sub Pl}.

Cosmology with decaying vacuum energy

International Nuclear Information System (INIS)

Freese, K.; Adams, F.; Frieman, J.; Mottola, E.

1987-09-01

Motivated by recent attempts to solve the cosmological constant problem, we examine the observational consequences of a vacuum energy density which decays in time. For all times later than t ∼ 1 sec, the ratio of the vacuum to the total energy density of the universe must be small. Although the vacuum cannot provide the ''missing mass'' required to close the universe today, its presence earlier in the history of the universe could have important consequences. We discuss restrictions on the vacuum energy arising from primordial nucleosynthesis, the microwave and gamma ray background spectra, and galaxy formation. A small vacuum component at the era of nucleosynthesis, 0.01 5, but in some cases would severely distort the microwave spectrum. 9 refs., 3 figs

Development of multi-channel high power rectangular RF window for LHCD system employing high temperature vacuum brazing technique

International Nuclear Information System (INIS)

Sharma, P K; Ambulkar, K K; Parmar, P R; Virani, C G; Thakur, A L; Joshi, L M; Nangru, S C

2010-01-01

A 3.7 GHz., 120 kW (pulsed), lower hybrid current drive (LHCD) system is employed to drive non-inductive plasma current in ADITYA tokamak. The rf power is coupled to the plasma through grill antenna and is placed in vacuum environment. A vacuum break between the pressurized transmission line and the grill antenna is achieved with the help of a multi (eight) channel rectangular RF vacuum window. The phasing between adjacent channels of 8-channel window (arranged in two rows) is important for launching lower hybrid waves and each channel should have independent vacuum window so that phase information is retained. The geometrical parameter of the grill antenna, like periodicity (9mm), channel dimensions (cross sectional dimension of 76mm x 7mm), etc. is to be maintained. These design constraint demanded a development of a multi channel rectangular RF vacuum window. To handle rf losses and thermal effects, high temperature vacuum brazing techniques is desired. Based on the above requirements we have successfully developed a multi channel rectangular rf vacuum window employing high temperature vacuum brazing technique. During the development process we could optimize the chemical processing parameters, brazing process parameters, jigs and fixtures for high temperature brazing and leak testing, etc. Finally the window is tested for low power rf performance using VNA. In this paper we would present the development of the said window in detail along with its mechanical, vacuum and rf performances.

Development of multi-channel high power rectangular RF window for LHCD system employing high temperature vacuum brazing technique

Energy Technology Data Exchange (ETDEWEB)

Sharma, P K; Ambulkar, K K; Parmar, P R; Virani, C G; Thakur, A L [Institute for Plasma Research, Bhat, Gandhinagar 382428 (India); Joshi, L M; Nangru, S C, E-mail: pramod@ipr.res.i [Central Electronics Engineering Research Institute, Pilani, Rajasthan 333 031 (India)

2010-02-01

A 3.7 GHz., 120 kW (pulsed), lower hybrid current drive (LHCD) system is employed to drive non-inductive plasma current in ADITYA tokamak. The rf power is coupled to the plasma through grill antenna and is placed in vacuum environment. A vacuum break between the pressurized transmission line and the grill antenna is achieved with the help of a multi (eight) channel rectangular RF vacuum window. The phasing between adjacent channels of 8-channel window (arranged in two rows) is important for launching lower hybrid waves and each channel should have independent vacuum window so that phase information is retained. The geometrical parameter of the grill antenna, like periodicity (9mm), channel dimensions (cross sectional dimension of 76mm x 7mm), etc. is to be maintained. These design constraint demanded a development of a multi channel rectangular RF vacuum window. To handle rf losses and thermal effects, high temperature vacuum brazing techniques is desired. Based on the above requirements we have successfully developed a multi channel rectangular rf vacuum window employing high temperature vacuum brazing technique. During the development process we could optimize the chemical processing parameters, brazing process parameters, jigs and fixtures for high temperature brazing and leak testing, etc. Finally the window is tested for low power rf performance using VNA. In this paper we would present the development of the said window in detail along with its mechanical, vacuum and rf performances.

On the problem of vacuum energy in brane theories

International Nuclear Information System (INIS)

Gurwich, Ilya; Rubin, Shimon; Davidson, Aharon

2009-01-01

We point out that modern brane theories suffer from a severe vacuum energy problem. To be specific, the Casimir energy associated with the matter fields confined to the brane, is stemming from the one and the same localization mechanism which forms the brane itself, and is thus generically unavoidable. Possible practical solutions are discussed, including in particular spontaneously broken supersymmetry, and quantum mechanically induced brane tension.

Approximated calculation of the vacuum wave function and vacuum energy of the LGT with RPA method

International Nuclear Information System (INIS)

Hui Ping

2004-01-01

The coupled cluster method is improved with the random phase approximation (RPA) to calculate vacuum wave function and vacuum energy of 2 + 1 - D SU(2) lattice gauge theory. In this calculating, the trial wave function composes of single-hollow graphs. The calculated results of vacuum wave functions show very good scaling behaviors at weak coupling region l/g 2 >1.2 from the third order to the sixth order, and the vacuum energy obtained with RPA method is lower than the vacuum energy obtained without RPA method, which means that this method is a more efficient one

Cold Vacuum Drying (CVD) Facility Vacuum Purge System Chilled Water System Design Description. System 47-4

International Nuclear Information System (INIS)

IRWIN, J.J.

2000-01-01

This system design description (SDD) addresses the Vacuum Purge System Chilled Water (VPSCHW) system. The discussion that follows is limited to the VPSCHW system and its interfaces with associated systems. The reader's attention is directed to Drawings H-1-82162, Cold Vacuum Drying Facility Process Equipment Skid PandID Vacuum System, and H-1-82224, Cold Vacuum Drying Facility Mechanical Utilities Process Chilled Water PandID. Figure 1-1 shows the location and equipment arrangement for the VPSCHW system. The VPSCHW system provides chilled water to the Vacuum Purge System (VPS). The chilled water provides the ability to condense water from the multi-canister overpack (MCO) outlet gases during the MCO vacuum and purge cycles. By condensing water from the MCO purge gas, the VPS can assist in drying the contents of the MCO

Vacuum science, technology, and applications

CERN Document Server

Naik, Pramod K

2018-01-01

Vacuum plays an important role in science and technology. The study of interaction of charged particles, neutrals and radiation with each other and with solid surfaces requires a vacuum environment for reliable investigations. Vacuum has contributed immensely to advancements made in nuclear science, space, metallurgy, electrical/electronic technology, chemical engineering, transportation, robotics and many other fields. This book is intended to assist students, scientists, technicians and engineers to understand the basics of vacuum science and technology for application in their projects. The fundamental theories, concepts, devices, applications, and key inventions are discussed.

Vacuum leak detector and method

Science.gov (United States)

Edwards, Jr., David

1983-01-01

Apparatus and method for detecting leakage in a vacuum system involves a moisture trap chamber connected to the vacuum system and to a pressure gauge. Moisture in the trap chamber is captured by freezing or by a moisture adsorbent to reduce the residual water vapor pressure therein to a negligible amount. The pressure gauge is then read to determine whether the vacuum system is leaky. By directing a stream of carbon dioxide or helium at potentially leaky parts of the vacuum system, the apparatus can be used with supplemental means to locate leaks.

Azimuthal Current Density Distribution Resulting from a Power Feed Vacuum Gap in Metallic Liner Experiments at 1 MA

Science.gov (United States)

Bott-Suzuki, Simon; Cordaro, S. W.; Caballero Bendixsen, L. S.; Atoyan, L.; Byvank, T.; Potter, W.; Kusse, B. R.; Greenly, J. B.; Hammer, D. A.; Chittenden, J. P.; Jennings, C. A.

2015-11-01

We present a study investigating the initiation of plasma in solid, metallic liners where the liner thickness is large compared to the collisionless skin depth. A vacuum gap is introduced in the power feed and we investigate the effect of this on the azimuthal initiation of plasma in the liner. We present optical emission data from aluminum liners on the 1 MA, 100ns COBRA generator. We use radial and axial gated imaging and streak photography, which show a dependence of onset of emission with the size of a small power-feed vacuum gap. The evolution of ``hot-spots'' generated from breakdown vacuum gap evolves relatively slowly and azimuthal uniformity is not observed on the experimental time-scale. We also show measurements of the B-field both outside and inside the liner, using miniature Bdot probes, which show a dependence on the liner diameter and thickness, and a correlation to the details of the breakdown. These data will be compared to magneto-hydrodynamic simulations to infer how such non-uniformities may affect full liner implosion experiments.

A Study on the Development of Nonglass Solar Vacuum Tube Collector

International Nuclear Information System (INIS)

Oh, Seung Jin

2008-02-01

Nature has been providing us energy from the beginning of the world. However human has hardly used it wisely. Solar energy is a kind of renewable energy from the nature. This study has been carried out to study the use of solar energy as it is harnessed in the form of thermal energy. Solar energy is one of the most promising energy resources such as hydrogen, biomass, wind and geothermal energy, because it is clean and inexhaustible. Space heating in buildings can be provided from solar energy by systems that are similar in many respects to water heater systems. By tapping into solar energy, we can not only solve the problem of energy shortage, but also can protect the environment and benefit the human beings. There are currently two types of evacuated tube; a single glass tube and a double glass tube. The former consists of a single glass tube which contains a flat or curved aluminium plate attached to a copper heat pipe or water flow pipe. The latter consists of rows of parallel transparent glass tubes, each of which contains an absorber tube. Evacuated tube collectors introduced above, however, pose some problems as they break rather easily under mechanical stresses. This paper introduces some preliminary results in design and fabrication of a non-glass solar vacuum tube collector in which the thermosyphon(heat pipe)made of copper is used as a heat transfer device. A series of tests have been performed to assess the ability of a non-glass solar vacuum tube collector. The series of experiments are as follows: 1)Vacuum level inside a vacuum tube. 2)Effects of the air remaining inside a vacuum tube on the temperature on the absorber plate. 3)Comparison of a non-glass vacuum solar collector with a single glass evacuated tube(SEIDO 5). Different vacuum levels inside non-glass vacuum tubes were applied to check any leakage or unexpected physical or chemical developments with time. The vacuum level changed from 10 -2 torr to 5torr in 5 days due to air infiltration from

QCD vacuum tensor susceptibility and properties of transversely polarized mesons

International Nuclear Information System (INIS)

Bakulev, A.P.; Mikhajlov, S.V.

1999-01-01

We re-estimate the tensor susceptibility of QCD vacuum, χ, and to this end, we re-estimate the leptonic decay constants for transversely polarized ρ-, ρ'- and b 1 -mesons. The origin of the susceptibility is analyzed using duality between ρ- and b 1 -channels in a 2-point correlator of tensor currents and disagree with [2] on both OPE expansion and the value of QCD vacuum tensor susceptibility. Using our value for the latter we determine new estimations of nucleon tensor charges related to the first moment of the transverse structure functions h 1 of a nucleon

Evaporation under vacuum condition

International Nuclear Information System (INIS)

Mizuta, Satoshi; Shibata, Yuki; Yuki, Kazuhisa; Hashizume, Hidetoshi; Toda, Saburo; Takase, Kazuyuki; Akimoto, Hajime

2000-01-01

In nuclear fusion reactor design, an event of water coolant ingress into its vacuum vessel is now being considered as one of the most probable accidents. In this report, the evaporation under vacuum condition is evaluated by using the evaporation model we have developed. The results show that shock-wave by the evaporation occurs whose behavior strongly depends on the initial conditions of vacuum. And in the case of lower initial pressure and temperature, the surface temp finally becomes higher than other conditions. (author)

Gauge field vacuum structure in geometrical aspect

International Nuclear Information System (INIS)

Konopleva, N.P.

2003-01-01

Vacuum conception is one of the main conceptions of quantum field theory. Its meaning in classical field theory is also very profound. In this case the vacuum conception is closely connected with ideas of the space-time geometry. The global and local geometrical space-time conceptions lead to different vacuum definitions and therefore to different ways of physical theory construction. Some aspects of the gauge field vacuum structure are analyzed. It is shown that in the gauge field theory the vacuum Einstein equation solutions describe the relativistic vacuum as common vacuum of all gauge fields and its sources. Instantons (both usual and hyperbolical) are regarded as nongravitating matter, because they have zero energy-momentum tensors and correspond to vacuum Einstein equations

Applying inversion techniques to derive source currents and geoelectric fields for geomagnetically induced current calculations

Directory of Open Access Journals (Sweden)

J. S. de Villiers

2014-10-01

Full Text Available This research focuses on the inversion of geomagnetic variation field measurement to obtain source currents in the ionosphere. During a geomagnetic disturbance, the ionospheric currents create magnetic field variations that induce geoelectric fields, which drive geomagnetically induced currents (GIC in power systems. These GIC may disturb the operation of power systems and cause damage to grounded power transformers. The geoelectric fields at any location of interest can be determined from the source currents in the ionosphere through a solution of the forward problem. Line currents running east–west along given surface position are postulated to exist at a certain height above the Earth's surface. This physical arrangement results in the fields on the ground having the magnetic north and down components, and the electric east component. Ionospheric currents are modelled by inverting Fourier integrals (over the wavenumber of elementary geomagnetic fields using the Levenberg–Marquardt technique. The output parameters of the inversion model are the current strength, height and surface position of the ionospheric current system. A ground conductivity structure with five layers from Quebec, Canada, based on the Layered-Earth model is used to obtain the complex skin depth at a given angular frequency. This paper presents preliminary and inversion results based on these structures and simulated geomagnetic fields. The results show some interesting features in the frequency domain. Model parameters obtained through inversion are within 2% of simulated values. This technique has applications for modelling the currents of electrojets at the equator and auroral regions, as well as currents in the magnetosphere.

Time response of protection in event of vacuum failure based on Nude ionization gauge controller

Science.gov (United States)

Gao, Hui; Wang, Qiuping; Wang, Weibin; Wu, Qinglin; Chen, Wentong; Sheng, Liusi; Zhang, Yunwu

2001-10-01

This article describes the design and application of fast-response vacuum protection sensor module, based on the Nude ionization gauge and a homemade controller named GH07X. A simulative test indicated that the controller's response time was less than 200 μs when 1 atm air rushed into the vacuum system through a pulsed valve with 0.8 mm orifice nozzle and the emitting current of the Nude gauge was 4 mA. The experiment result showed that the response time mainly depended on the gas density as well as the electron emitting current of the Nude gauge filament. Compared with the vacuum protection sensors based on sputter ion pump and cold-cathode gauge, GH07X is faster and reliable besides, GH07X can be used as an ultrahigh-vacuum slow valve interlock controller with response time of 100 ms, which is faster than other gauge controllers. The widely used field-bus interface CAN and common serial interface RS232/RS485 are embedded in GH07X controller system.

Historical review of the vacuum chamber technology for INS-ES

International Nuclear Information System (INIS)

Yoshida, Katsuhide

2006-01-01

The INS (Institute for Nuclear Study), University of Tokyo, was founded in 1955. Construction of the ES (electron synchrotron) was approved in 1956 and finished in 1961. 1.3 GeV INS-ES consists of 8 electric magnets with 3.14m length at intervals of 1.2m. It used resonant exciting current. The vacuum chamber was called donut made of ceramics at first and changed by araldite in 1964, and metal in 1970's. 53% of troubles were caused by the vacuum system in 1966. The metal donut with stainless steel welding bellows was changed by the stainless steel from SUS304 to SUS316L. These improvement methods solved the vacuum problems. The donut made of araldite, a trial piece of stainless steel welding bellows, increase of beam intensity of INS-ES and position of stainless steel welding bellows in section are shown. (S.Y.)

Vacuum metastability with black holes

Energy Technology Data Exchange (ETDEWEB)

Burda, Philipp [Centre for Particle Theory, Durham University,South Road, Durham, DH1 3LE (United Kingdom); Gregory, Ruth [Centre for Particle Theory, Durham University,South Road, Durham, DH1 3LE (United Kingdom); Perimeter Institute, 31 Caroline Street North,Waterloo, ON, N2L 2Y5 (Canada); Moss, Ian G. annd [School of Mathematics and Statistics, Newcastle University,Newcastle Upon Tyne, NE1 7RU (United Kingdom)

2015-08-24

We consider the possibility that small black holes can act as nucleation seeds for the decay of a metastable vacuum, focussing particularly on the Higgs potential. Using a thin-wall bubble approximation for the nucleation process, which is possible when generic quantum gravity corrections are added to the Higgs potential, we show that primordial black holes can stimulate vacuum decay. We demonstrate that for suitable parameter ranges, the vacuum decay process dominates over the Hawking evaporation process. Finally, we comment on the application of these results to vacuum decay seeded by black holes produced in particle collisions.

Vacuum metastability with black holes

International Nuclear Information System (INIS)

Burda, Philipp; Gregory, Ruth; Moss, Ian G. annd

2015-01-01

We consider the possibility that small black holes can act as nucleation seeds for the decay of a metastable vacuum, focussing particularly on the Higgs potential. Using a thin-wall bubble approximation for the nucleation process, which is possible when generic quantum gravity corrections are added to the Higgs potential, we show that primordial black holes can stimulate vacuum decay. We demonstrate that for suitable parameter ranges, the vacuum decay process dominates over the Hawking evaporation process. Finally, we comment on the application of these results to vacuum decay seeded by black holes produced in particle collisions.

Comparison of occlusion break responses and vacuum rise times of phacoemulsification systems.

Science.gov (United States)

Sharif-Kashani, Pooria; Fanney, Douglas; Injev, Val

2014-07-30

Occlusion break surge during phacoemulsification cataract surgery can lead to potential surgical complications. The purpose of this study was to quantify occlusion break surge and vacuum rise time of current phacoemulsification systems used in cataract surgery. Occlusion break surge at vacuum pressures between 200 and 600 mmHg was assessed with the Infiniti® Vision System, the WhiteStar Signature® Phacoemulsification System, and the Centurion® Vision System using gravity-fed fluidics. Centurion Active FluidicsTM were also tested at multiple intraoperative pressure target settings. Vacuum rise time was evaluated for Infiniti, WhiteStar Signature, Centurion, and Stellaris® Vision Enhancement systems. Rise time to vacuum limits of 400 and 600 mmHg was assessed at flow rates of 30 and 60 cc/minute. Occlusion break surge was analyzed by 2-way analysis of variance. The Centurion system exhibited substantially less occlusion break surge than the other systems tested. Surge area with Centurion Active Fluidics was similar to gravity fluidics at an equivalent bottle height. At all Centurion Active Fluidics intraoperative pressure target settings tested, surge was smaller than with Infiniti and WhiteStar Signature. Infiniti had the fastest vacuum rise time and Stellaris had the slowest. No system tested reached the 600-mmHg vacuum limit. In this laboratory study, Centurion had the least occlusion break surge and similar vacuum rise times compared with the other systems tested. Reducing occlusion break surge may increase safety of phacoemulsification cataract surgery.

Is it safe to disturb the vacuum

International Nuclear Information System (INIS)

Hut, P.

1984-01-01

Ultra-relativistic U 238 -U 238 collisions, which are now being envisioned for the next generation of heavy ion accelerators, do not occur in large quantities anywhere in the universe at present. Nor have they ever occurred abundantly in the past. When U 238 nuclei were first synthesized the universe had grown already for too cold. This raises the question whether such a novel type of experiment could trigger a catastrophic phase transition of the vacuum to a lower energy state, a possibility naturally occurring in many spontaneously broken quantum field theories. Theoretical calculations of the collisionally induced nucleation rate of critical bubbles precipitating such phase transitions are not yet available, and nothing is known about the parameters describing the barrier separating our vacuum from a possibly lower energy state. Fortunately, available cosmic ray evidence suggests that sporadic individual U 238 -U 238 collisions have indeed occurred at ultra-relativistic energies inside our past light cone, which would imply that the proposed experiments do not tread potentially dangerous new ground. Direct confirmation of the predicted small abundance of U 238 and other actinides in cosmic rays at energies in the interesting range 10 13 -10 15 eV, corresponding to 40 GeV/n-4 TeV/n, is not feasible at present. Nevertheless, even indirect detection of at least some ultra-heavy nuclei in the actinide group (Z>88) in this energy range would more affirmatively answer the question: 'Do we dare disturb the vacuum. (orig.)

Vacuum exhaust duct used for thermonuclear device

International Nuclear Information System (INIS)

Tachikawa, Nobuo; Kondo, Mitsuaki; Honda, Tsutomu.

1990-01-01

The present invention concerns a vacuum exhaust duct used for a thermonuclear device. A cylindrical metal liners is lined with a gap to the inside of a vacuum exhaust duct main body. Bellows are connected to both ends of the metal liners and the end of the bellows is welded to the vacuum exhaust duct main body. Futher, a heater is mounted to the metal liner on the side of the vacuum exhaust duct main body, and the metal liner is heated by the heater to conduct baking for the vacuum exhaust duct main body. Accordingly, since there is no requirement for elevating the temperature of the vacuum exhaust duct upon conducting baking, the vacuum exhaust duct scarcely suffers substantial deformation due to heat expansion. Further, there is also no substantial deformation for the bellows disposed between the outer circumference of the vacuum vessel and a portion of a vacuum exhaust duct, so that the durability of the bellows is greatly improved. (I.S.)

VACUUM THERAPY – PREVENTION OF HYPOXIA OF CAVERNOUS TISSUE PATIENTS AFTER RADICAL PROSTATECTOMY

Directory of Open Access Journals (Sweden)

A. E. Osadchinskii

2018-01-01

Full Text Available Patients, after radical prostatectomy with the use of nerve-sparing techniques, without carrying out penile rehabilitation, are at risk of forming cavernous fibrosis with the emergence of subsequent persistent erectile dysfunction. In order to minimize damage to cavernous tissue and early restoration of erectile function during the period of neuropraxia, it is necessary to ensure a sufficient level of oxygenation. The role of applying vacuum in penile rehabilitation for the prevention of hypoxia of cavernous tissue is not fully understood, due to the lack of data on the gaseous composition of the blood at the time of reaching the vacuum of erection. The purpose of this work was to review the scientific studies devoted to the study of vacuum induced penile erection in animals or humans, which indicates high results due to increased oxygenation of cavernous tissue.

Vacuum magnetic field and modular coil system of the advanced stellarator Wendelstein VII-AS

International Nuclear Information System (INIS)

Rau, F.; Kisslinger, J.; Wobig, H.

1982-06-01

The vacuum field and the modular coils of the advanced stellarator WENDELSTEIN VII-AS are described. Each of the five field periods contains 9 different twisted coils, one of them with increased dimensions and current in order to provide sufficient access. The standard vacuum field configuration (B=3 T, t=0.39, aspect ratio approx. equal to 10, low shear, and magnetic well) can be varied by toroidal and vertical fields, or by changing independently the current in the large special coils. From a study of magnetic field perturbations some estimates are derived for the admissible coil tolerances. (orig.)

INFLUENCE OF VACUUM ARC PLASMA EVAPORATOR CATHODE GEOMETRY OF ON VALUE OF ADMISSIBLE ARC DISCHARGE CURRENT

Directory of Open Access Journals (Sweden)

I. A. Ivanou

2015-01-01

Full Text Available An analysis of main design parameters that determine a level of droplet formation intensity at the generating stage of plasma flow has been given in the paper. The paper considers the most widely used designs of water cooled consumable cathodes. Ti or Ti–Si and Fe–Cr alloys have been taken as a material for cathodes. The following calculated data: average ionic charge Zi for titanium plasma +1.6; for «titanium–silicon plasma» +1.2, an electronic discharge 1.6022 ⋅ 10–19 C, an ion velocity vi = 2 ⋅ 104 m/s, an effective volt energy equivalent of heat flow diverted in the cathode Uк = 12 V, temperature of erosion cathode surface Тп = 550 К; temperature of the cooled cathode surface То = 350 К have been accepted in order to determine dependence of a maximum admissible arc discharge current on cathode height. The calculations have been carried out for various values of the cathode heights hк (from 0.02 to 0.05 m. Diameter of a target cathode is equal to 0.08 m for a majority of technological plasma devices, therefore, the area of the erosion surface is S = 0.005 m2.A thickness selection for a consumable target cathode part in the vacuum arc plasma source has been justified in the paper. The thickness ensures formation of minimum drop phase in the plasma flow during arc cathode material evaporation. It has been shown that a maximum admissible current of an arc discharge is practically equal to the minimum current of stable arcing when thickness of the consumable cathode part is equal to 0.05 m. The admissible discharge current can be rather significant and ensure high productivity during coating process with formation of relatively low amount of droplet phase in the coating at small values of hк.

MODEL OF HYDRODYNAMIC MIXING OF CARBONIC POWDERS IN VACUUMATOR, USED IN STEEL-MAKING OF RUP “BMZ”

Directory of Open Access Journals (Sweden)

A. N. Chichko

2005-01-01

Full Text Available The mathematical model of the mixing and dissolving process of carbonic powder in a system '"vacuumator-bowl” under influence of circulating argon is offered. The spatial distribution of hydrodynamic currents at mixing of carbonic powder, received on the basis of computer calculations is presented. The character of distribution of hydrodynamic speeds of melt (circulating currents in industrial bowl and vacuumator for different time slots of mixing is determined. 

Soft X-ray beam induced current technique

Energy Technology Data Exchange (ETDEWEB)

Watts, B; Ade, H [Department of Physics, North Carolina State University, Raleigh, NC 27695 (United States); Queen, D; Hellman, F [Department of Physics, University of California, Berkeley, CA 94720 (United States); Kilcoyne, A L D; Tyliszczak, T, E-mail: benjamin.watts@gmail.co [Advanced Light Source, Lawrence Berkeley Nat. Lab., Berkeley, CA 94720 (United States)

2009-09-01

Direct mapping of the charge transport efficiency of polymer solar cell devices using a soft X-ray beam induced current (SoXBIC) method is described. By fabricating a polymer solar cell on an x-ray transparent substrate, we demonstrate the ability to map polymer composition and nanoscale structure within an operating solar cell device and to simultaneously measure the local charge transport efficiency via the short-circuit current. A simple model is calculated and compared to experimental SoXBIC data of a PFB:F8BT bulk-heterojunction device in order to gain greater insight into the device operation and physics.

Ambipolarity reduction in DMG asymmetric vacuum dielectric Schottky Barrier GAA MOSFET to improve hot carrier reliability

Science.gov (United States)

Kumar, Manoj; Haldar, Subhasis; Gupta, Mridula; Gupta, R. S.

2017-11-01

An explicit surface potential and subthreshold current model for novel Dual Metal Gate (DMG) Asymmetric Vacuum (AV) as gate dielectric Schottky Barrier (SB) Cylindrical Gate All Around (CGAA) MOSFET with the incorporation of localized charges (Nf) is developed to provide excellent immunity against threshold voltage (Vth) degradation due to hot carriers. Hot carrier induced Localized Charges (LC) either positive or negative leads to degrade the threshold of the device. The major advantage of the proposed DMG-AV-SB-CGAA MOSFET is that it mitigates the ambipolar behavior thus offering very good on current to off current ratio; and also reduces the electron temperature which leads to less hot carrier generation thus lesser degradation in Vth and improved Hot Carrier reliability. The surface potential is determined for three different regions by solving 1-D Poisson's and 2-D Laplace equation through separation of variable method to facilitate an optimal model for calculating the subthreshold drain current from Si-SiO2 interface boundary. The developed model results are in good agreement with that of ATLAS-TCAD simulation.

Development of vacuum brazing furnace

International Nuclear Information System (INIS)

Singh, Rajvir; Yedle, Kamlesh; Jain, A.K.

2005-01-01

In joining of components where welding process is not possible brazing processes are employed. Value added components, high quality RF systems, UHV components of high energy accelerators, carbide tools etc. are produced using different types of brazing methods. Furnace brazing under vacuum atmosphere is the most popular and well accepted method for production of the above mentioned components and systems. For carrying out vacuum brazing successfully it is essential to have a vacuum brazing furnace with latest features of modern vacuum brazing technology. A vacuum brazing furnace has been developed and installed for carrying out brazing of components of copper, stainless steel and components made of dissimilar metals/materials. The above furnace has been designed to accommodate jobs of 700mm diameter x 2000mm long sizes with job weight of 500kgs up to a maximum temperature of 1250 degC at a vacuum of 5 x 10 -5 Torr. Oil diffusion pumping system with a combination of rotary and mechanical booster pump have been employed for obtaining vacuum. Molybdenum heating elements, radiation shield of molybdenum and Stainless Steel Grade 304 have been used. The above furnace is computer controlled with manual over ride facility. PLC and Pentium PC are integrated together to maneuver steps of operation and safety interlocks of the system. Closed loop water supply provides cooling to the system. The installation of the above system is in final stage of completion and it will be ready for use in next few months time. This paper presents insights of design and fabrication of a modern vacuum brazing furnace and its sub-system. (author)

In-vacuum scattered light reduction with black cupric oxide surfaces for sensitive fluorescence detection.

Science.gov (United States)

Norrgard, E B; Sitaraman, N; Barry, J F; McCarron, D J; Steinecker, M H; DeMille, D

2016-05-01

We demonstrate a simple and easy method for producing low-reflectivity surfaces that are ultra-high vacuum compatible, may be baked to high temperatures, and are easily applied even on complex surface geometries. Black cupric oxide (CuO) surfaces are chemically grown in minutes on any copper surface, allowing for low-cost, rapid prototyping, and production. The reflective properties are measured to be comparable to commercially available products for creating optically black surfaces. We describe a vacuum apparatus which uses multiple blackened copper surfaces for sensitive, low-background detection of molecules using laser-induced fluorescence.

Current-induced runaway vibrations in dehydrogenated graphene nanoribbons

DEFF Research Database (Denmark)

Christensen, Rasmus Bjerregaard; Lu, Jing Tao; Hedegard, Per

2016-01-01

We employ a semi-classical Langevin approach to study current-induced atomic dynamics in a partially dehydrogenated armchair graphene nanoribbon. All parameters are obtained from density functional theory. The dehydrogenated carbon dimers behave as effective impurities, whose motion decouples from...

Current-induced runaway vibrations in dehydrogenated graphene nanoribbons

DEFF Research Database (Denmark)

Christensen, Rasmus Bjerregaard; Lu, Jing Tao; Hedegard, Per

2016-01-01

We employ a semi-classical Langevin approach to study current-induced atomic dynamics in a partially dehydrogenated armchair graphene nanoribbon. All parameters are obtained from density functional theory. The dehydrogenated carbon dimers behave as effective impurities, whose motion decouples fro...

Gases and vacua handbook of vacuum physics

CERN Document Server

Beck, A H

2013-01-01

Handbook of Vacuum Physics, Volume 1: Gases and Vacua provides information on the many aspects of vacuum technology, from material on the quantum theoretical aspects of the complex semi-conductors used for thermionic and photo-electric emission to data on the performance of commercially available pumps, gauges, and high-vacuum materials. The handbook satisfies the need of workers using vacuum apparatuses or works on the diverse applications of high-vacuum technology in research and industry. The book is a compilation of long articles prepared by experts in vacuum technology. Sufficient theoret

Hadron Contribution to Vacuum Polarisation

CERN Document Server

Davier, M; Malaescu, B; Zhang, Z

2016-01-01

Precision tests of the Standard Theory require theoretical predictions taking into account higher-order quantum corrections. Among these vacuum polarisation plays a predominant role. Vacuum polarisation originates from creation and annihilation of virtual particle–antiparticle states. Leptonic vacuum polarisation can be computed from quantum electrodynamics. Hadronic vacuum polarisation cannot because of the non-perturbative nature of QCD at low energy. The problem is remedied by establishing dispersion relations involving experimental data on the cross section for e+ e− annihilation into hadrons. This chapter sets the theoretical and experimental scene and reviews the progress achieved in the last decades thanks to more precise and complete data sets. Among the various applications of hadronic vacuum polarisation calculations, two are emphasised: the contribution to the anomalous magnetic moment of the muon, and the running of the fine structure constant α to the Z mass scale. They are fundamental ingre...

Helical type vacuum container

International Nuclear Information System (INIS)

Owada, Kimio.

1989-01-01

Helical type vacuum containers in the prior art lack in considerations for thermal expansion stresses to helical coils, and there is a possibility of coil ruptures. The object of the present invention is to avoid the rupture of helical coils wound around the outer surface of a vacuum container against heat expansion if any. That is, bellows or heat expansion absorbing means are disposed to a cross section of a helical type vacuum container. With such a constitution, thermal expansion of helical coils per se due to temperature elevation of the coils during electric supply can be absorbed by expansion of the bellows or absorption of the heat expansion absorbing means. Further, this can be attained by arranging shear pins in the direction perpendicular to the bellows axis so that the bellows are not distorted when the helical coils are wound around the helical type vacuum container. (I.S.)

Current methodologies for assessing seismically induced settlements in soil

International Nuclear Information System (INIS)

Ledbetter, R.

1983-08-01

Earthquake-induced surface settlements have ranged from 0.7 to 10 percent of layer thickness for the relatively few incidences where reliable estimates have been made of settlement magnitudes and soil conditions. Standard penetration test results obtained for pre-earthquake and postearthquake conditions in Japan show that relative densities have changed from 188 percent increase to 44 percent decrease. At present, there are no verified methods of seismic settlement analysis. However, there are current methods of analysis ranging from empirical to fully theoretical, which take into account a few to all of the major variables affecting seismically induced settlement behavior. This report reviews pertinent current knowledge and methodologies related to this subject. 69 references, 9 figures

PDX vacuum vessel stress analysis

International Nuclear Information System (INIS)

Nikodem, Z.D.

1975-01-01

A stress analysis of PDX vacuum vessel is described and the summary of results is presented. The vacuum vessel is treated as a toroidal shell of revolution subjected to an internal vacuum. The critical buckling pressure is calculated. The effects of the geometrical discontinuity at the juncture of toroidal shell head and cylindrical outside wall, and the concavity of the cylindrical wall are examined. An effect of the poloidal field coil supports and the vessel outside supports on the stress distribution in the vacuum vessel is determined. A method evaluating the influence of circular ports in the vessel wall on the stress level in the vessel is outlined

Ultrafast terahertz control of extreme tunnel currents through single atoms on a silicon surface

DEFF Research Database (Denmark)

Jelic, Vedran; Iwaszczuk, Krzysztof; Nguyen, Peter H.

2017-01-01

scanning tunnelling microscopy (THz-STM) in ultrahigh vacuum as a new platform for exploring ultrafast non-equilibrium tunnelling dynamics with atomic precision. Extreme terahertz-pulse-driven tunnel currents up to 10(7) times larger than steady-state currents in conventional STM are used to image...... terahertz-induced band bending and non-equilibrium charging of surface states opens new conduction pathways to the bulk, enabling extreme transient tunnel currents to flow between the tip and sample.......Ultrafast control of current on the atomic scale is essential for future innovations in nanoelectronics. Extremely localized transient electric fields on the nanoscale can be achieved by coupling picosecond duration terahertz pulses to metallic nanostructures. Here, we demonstrate terahertz...

Atom Interferometry for Dark Contents of the Vacuum Searches

Energy Technology Data Exchange (ETDEWEB)

Burrow, O. [Liverpool U.; Carroll, A. [Liverpool U.; Chattopadhyay, S. [Northern Illinois U.; Coleman, J. [Liverpool U.; Elertas, G. [Teddington, Natl. Phys. Lab; Heffer, J. [Liverpool U.; Metelko, C. [Liverpool U.; Moore, R. [Teddington, Natl. Phys. Lab; Morris, D. [Liverpool U.; Perl, M. [SLAC; Ralph, J. [Liverpool U.; Tinsley, J. [Teddington, Natl. Phys. Lab

2017-05-25

A cold atom interferometer is being developed using 85Rb atoms towards a search for the dark contents of the vacuum, and as a test stand for inertial sensing applications. Here we outline the current status of the experiment and report the observation of Ramsey interference fringes in the apparatus.

Life cycle environmental impacts of vacuum cleaners and the effects of European regulation.

Science.gov (United States)

Gallego-Schmid, Alejandro; Mendoza, Joan Manuel F; Jeswani, Harish Kumar; Azapagic, Adisa

2016-07-15

Energy efficiency of vacuum cleaners has been declining over the past decades while at the same time their number in Europe has been increasing. The European Commission has recently adopted an eco-design regulation to improve the environmental performance of vacuum cleaners. In addition to the existing directive on waste electrical and electronic equipment (WEEE), the regulation could potentially have significant effects on the environmental performance of vacuum cleaners. However, the scale of the effects is currently unknown, beyond scant information on greenhouse gas emissions. Thus, this paper considers for the first time life cycle environmental impacts of vacuum cleaners and the effects of the implementation of these regulations at the European level. The effects of electricity decarbonisation, product lifetime and end-of-life disposal options are also considered. The results suggest that the implementation of the eco-design regulation alone will reduce significantly the impacts from vacuum cleaners (37%-44%) by 2020 compared with current situation. If business as usual continued and the regulation was not implemented, the impacts would be 82%-109% higher by 2020 compared to the impacts with the implementation of the regulation. Improvements associated with the implementation of the WEEE directive will be much smaller (impacts would be 2%-21% higher by 2020 relative to the impacts with the implementation of the directive. Further improvements in most impacts (6%-20%) could be achieved by decarbonising the electricity mix. Therefore, energy efficiency measures must be accompanied by appropriate actions to reduce the environmental impacts of electricity generation; otherwise, the benefits of improved energy efficiency could be limited. Moreover, because of expected lower life expectancy of vacuum cleaners and limited availability of some raw materials, the eco-design regulation should be broadened to reduce the impacts from raw materials, production and end

New baking system for the RFX vacuum vessel

Energy Technology Data Exchange (ETDEWEB)

Collarin, P.; Luchetta, A.; Sonato, P.; Toigo, V.; Zaccaria, P.; Zollino, G. [Universita di Padova (Italy)

1996-12-31

A heating system based on eddy currents has been developed for the vacuum vessel of the RFX Reversed Field Pinch device. After a testing phase, carried out at low power, the final power supply system has been designed and installed. It has been used during last year to bake out the vessel and the graphite first wall up to 320{degree}C. Recently the heating system has been completed with a control system that allows for baking sessions with an automatic control of the vacuum vessel temperature and for pulse sessions with a heated first wall. After the description of the preliminary analyses and tests, and of the main characteristics of the power supply and control systems, the experimental results of the baking sessions performed during last year are presented. 6 refs., 7 figs.

New baking system for the RFX vacuum vessel

International Nuclear Information System (INIS)

Collarin, P.; Luchetta, A.; Sonato, P.; Toigo, V.; Zaccaria, P.; Zollino, G.

1996-01-01

A heating system based on eddy currents has been developed for the vacuum vessel of the RFX Reversed Field Pinch device. After a testing phase, carried out at low power, the final power supply system has been designed and installed. It has been used during last year to bake out the vessel and the graphite first wall up to 320 degree C. Recently the heating system has been completed with a control system that allows for baking sessions with an automatic control of the vacuum vessel temperature and for pulse sessions with a heated first wall. After the description of the preliminary analyses and tests, and of the main characteristics of the power supply and control systems, the experimental results of the baking sessions performed during last year are presented. 6 refs., 7 figs

Electrospray ionization deposition of BSA under vacuum conditions

Science.gov (United States)

Hecker, Dominic; Gloess, Daniel; Frach, Peter; Gerlach, Gerald

2015-05-01

Vacuum deposition techniques like thermal evaporation and CVD with their precise layer control and high layer purity often cannot be applied for the deposition of chemical or biological molecules. The molecules are usually decomposed by heat. To overcome this problem, the Electrospray ionization (ESI) process known from mass spectroscopy is employed to transfer molecules into vacuum and to deposit them on a substrate. In this work, a homemade ESI tool was used to deposit BSA (Bovine serum albumin) layers with high deposition rates. Solutions with different concentrations of BSA were prepared using a methanol:water (MeOH:H2O) mixture (1:1) as solvent. The influence of the substrate distance on the deposition rate and on the transmission current was analyzed. Furthermore, the layer thickness distribution and layer adhesion were investigated.

Quark and gluon condensate in vacuum

International Nuclear Information System (INIS)

Vajnshtejn, A.I.; Zakharov, V.I.; Shifman, M.A.

1979-01-01

The mechanism of quark confinement has been reviewed. The fact that coloured particles in a free state cannot be observed is connected with specific properties of vacuum in quantum chromodynamics. The basic hypothesis consists in the existence of vacuum fields, quark and gluon condensates, which affect the coloured objects. The vacuum transparent relative to noncharged ''white'' states serves as a source of the force acting upon the coloured particles. It has been a sucess to examine strictly the action of the vacuum fields on quarks when the distance between them is relatively small and the force of the vacuum fields on quarks is relatively small too. It is shown that the interaction with the vacuum fields manifests itself earlier than the forces connected with the gluon exchange do. It is assumed that the vacuum condensate of quarks and gluons and its relation to properties of resonances and to the bag model exist in reality. The dispersion sum rules are used for calculating masses and lepton widths of resonances

CAS CERN Accelerator School vacuum technology. Proceedings

International Nuclear Information System (INIS)

Turner, S.

1999-01-01

These proceedings present the lectures given at the twelfth specialized course organized by the CERN Accelerator School (CAS), the topic this time being 'Vacuum Technology'. Despite the importance of vacuum technology in the design and operation of particle accelerators at CERN and at the many other accelerators already installed around the world, this was the first time that CAS has organized a course devoted entirely to this topic. Perhaps this reflects the facts that vacuum has become one of the more critical aspects of future accelerators, and that many of the pioneers in the accelerator field are being replaced by new, younger personnel. The lectures start with the basic concepts of the physics and technology of vacuum followed by detailed descriptions of the many different types of gas-pumping devices and methods to measure the pressures achieved. The outgassing characteristics of the different materials used in the construction of vacuum systems and the optimisation of cleaning methods to reduce this outgassing are then explained together with the effects of the residual gases on the particle beams. Then follow chapters on leak detection, materials and vacuum system engineering. Finally, seminars are presented on designing vacuum systems, the history of vacuum devices, the LHC (large hadron collider) vacuum system, vacuum systems for electron storage rings, and quality assurance for vacuum. (orig.)

Microwave and RF vacuum electronic power sources

CERN Document Server

Carter, Richard G

2018-01-01

Do you design and build vacuum electron devices, or work with the systems that use them? Quickly develop a solid understanding of how these devices work with this authoritative guide, written by an author with over fifty years of experience in the field. Rigorous in its approach, it focuses on the theory and design of commercially significant types of gridded, linear-beam, crossed-field and fast-wave tubes. Essential components such as waveguides, resonators, slow-wave structures, electron guns, beams, magnets and collectors are also covered, as well as the integration and reliable operation of devices in microwave and RF systems. Complex mathematical analysis is kept to a minimum, and Mathcad worksheets supporting the book online aid understanding of key concepts and connect the theory with practice. Including coverage of primary sources and current research trends, this is essential reading for researchers, practitioners and graduate students working on vacuum electron devices.

Theory of pressure-induced islands and self-healing in three-dimensional toroidal magnetohydrodynamic equilibria

International Nuclear Information System (INIS)

Bhattacharjee, A.; Hayashi, T.; Hegna, C.C.; Nakajima, N.; Sato, T.

1994-11-01

The role of singular currents in three-dimensional toroidal equilibria and their resolution by magnetic island formation is discussed from both analytical and computational points of view. Earlier analytical results are extended to include small vacuum islands which may, in general, have different phases with respect to pressure-induced islands. In currentless stellarators, the formation of islands is shown to depend on the resistive parameter D R as well as the integrated effect of global Pfirsch-Schlueter currents. It is demonstrated that the pressure-induced 'self-healing' effect, recently discovered computationally, is also predicted by analytical theory. (author)

ULTRARAPID VACUUM-MICROWAVE HISTOPROCESSING

NARCIS (Netherlands)

KOK, LP; BOON, ME

A novel histoprocessing method for paraffin sections is presented in which the combination of vacuum and microwave exposure is the key element. By exploiting the decrease in boiling temperature under vacuum, the liquid molecules in the tissues have been successfully extracted and exchanged at

The JET vacuum interspace system

International Nuclear Information System (INIS)

Orchard, J.; Scales, S.

1999-01-01

In the past JET has suffered from a number of vacuum leaks on components such as bellows, windows and feedthroughs due, in part, to the adverse conditions, including high mechanical forces, which may prevail during plasma operation. Therefore before the recent Tritium experiments on JET it was deemed prudent to manufacture and install items with a secondary containment or interspace in order to minimise the effect of failure of the primary vacuum barrier on both the leak integrity of the machine and the outcome of the experiments. This paper describes the philosophy, logistics, method and implementation of an integrated connection and monitoring system on the 330 interspaces currently in position on the JET machine. Using the JET leak database comparisons are drawn of leak failure rates of the components allied to the number of operational hours, prior to the system being present and after installation and commissioning, and the case of detection compared to the previous situation. An argument is also presented on the feasibility and adaptability of this system to any large complex machine and the benefits to be obtained in reduction of leaks and operational down time. (author)

An anisotropic universe due to dimension-changing vacuum decay

International Nuclear Information System (INIS)

Scargill, James H.C.

2015-01-01

In this paper we consider the question of observational signatures of a false vacuum decay event in the early universe followed by a period of inflation; in particular, motivated by the string landscape, we consider decays in which the parent vacuum has a smaller number of large dimensions than the current vacuum, which leads to an anisotropic universe. We go beyond previous studies, and examine the effects on the CMB temperature and polarisation power spectra, due to both scalar and tensor modes, and consider not only late-time effects but also the full cosmological perturbation theory at early times. We find that whilst the scalar mode behaves as one would expect, and the effects of anisotropy at early times are sub-dominant to the late-time effects already studied, for the tensor modes in fact the the early-time effects grow with multipole and can become much larger than one would expect, even dominating over the late-time effects. Thus these effects should be included if one is looking for such a signal in the tensor modes

DC switch power supply for vacuum-arc coatings deposition

International Nuclear Information System (INIS)

Zalesskij, D.Yu.; Volkov, Yu.Ya.; Vasil'ev, V.V.; Kozhushko, V.V.; Luchaninov, A.A.; Strel'nitskij, V.E.

2008-01-01

Special DC Switch Power Supply for vacuum-arc deposition was developed and tested in the mode of depositing Al and AlN films. Maximum output power was 6 kW, maximum output current - 120 A, open-circuit voltage - 150 V. The Power Supply allows to adjust and stabilize output current in a wide range. Testing of the Power Supply revealed an advantages over the standard 'Bulat-6' power supply, especially for deposition of non-conductive AlN films.

Atmospheres and spectra of strongly magnetized neutron stars - II. The effect of vacuum polarization

Science.gov (United States)

Ho, Wynn C. G.; Lai, Dong

2003-01-01

We study the effect of vacuum polarization on the atmosphere structure and radiation spectra of neutron stars with surface magnetic fields B= 1014-1015 G, as appropriate for magnetars. Vacuum polarization modifies the dielectric property of the medium and gives rise to a resonance feature in the opacity; this feature is narrow and occurs at a photon energy that depends on the plasma density. Vacuum polarization can also induce resonant conversion of photon modes via a mechanism analogous to the Mikheyev-Smirnov-Wolfenstein (MSW) mechanism for neutrino oscillation. We construct atmosphere models in radiative equilibrium with an effective temperature of a few ×106 K by solving the full radiative transfer equations for both polarization modes in a fully ionized hydrogen plasma. We discuss the subtleties in treating the vacuum polarization effects in the atmosphere models and present approximate solutions to the radiative transfer problem which bracket the true answer. We show from both analytic considerations and numerical calculations that vacuum polarization produces a broad depression in the X-ray flux at high energies (a few keV <~E<~ a few tens of keV) as compared to models without vacuum polarization; this arises from the density dependence of the vacuum resonance feature and the large density gradient present in the atmosphere. Thus the vacuum polarization effect softens the high-energy tail of the thermal spectrum, although the atmospheric emission is still harder than the blackbody spectrum because of the non-grey opacities. We also show that the depression of continuum flux strongly suppresses the equivalent width of the ion cyclotron line and therefore makes the line more difficult to observe.

Optimal Operation of a Josephson Parametric Amplifier for Vacuum Squeezing

Science.gov (United States)

Malnou, M.; Palken, D. A.; Vale, Leila R.; Hilton, Gene C.; Lehnert, K. W.

2018-04-01

A Josephson parametric amplifier (JPA) can create squeezed states of microwave light, lowering the noise associated with certain quantum measurements. We experimentally study how the JPA's pump influences the phase-sensitive amplification and deamplification of a coherent tone's amplitude when that amplitude is commensurate with vacuum fluctuations. We predict and demonstrate that, by operating the JPA with a single current pump whose power is greater than the value that maximizes gain, the amplifier distortion is reduced and, consequently, squeezing is improved. Optimizing the singly pumped JPA's operation in this fashion, we directly observe 3.87 ±0.03 dB of vacuum squeezing over a bandwidth of 30 MHz.

Selection of vacuum seals for EBT-P

International Nuclear Information System (INIS)

Dillow, C.F.; Adlon, G.L.; Stubblefield, V.E.

1981-01-01

Elmo Bumpy Torus Proof of Principle (EBT-P) is a magnetic fusion RandD facility being constructed by McDonnell Douglas Astronautics Company - St. Louis Division of Oak Ridge National Laboratory (ORNL). EBT-P is a truly unique fusion device requiring careful consideration in selecting both the primary vacuum seals on the toroidal vessel and the secondary vacuum seals in components such as vacuum pumps and and valves. The vacuum seal environment is described and the considerations in vacuum seal selection fully discussed. Methods for protecting vacuum seals in pumps and valves from the microwave environments are also presented

Methods for the improvement of electrical insulation in vacuum in the presence of transverse magnetic field

International Nuclear Information System (INIS)

Hara, Masanori; Suehiro, Junya; Shigematsu, Hidetaka; Yano, Shinsuke

1989-01-01

At present in electrical energy field, aiming at the development and operation of new energy sources for the future, the research on nuclear fusion reactors, MHD electricity generation, and electromagnetic energy storage is in progress, and in ordeer to form strong magnetic fields over wide space, large superconducting magnets are expected to be employed. In these magnets, when exciting current changes, voltage is induced internally, therefore, the operation sequence is deeply related to coil insulation, in pulse operation, coil insulation is one of the important factors determining the rating, and the withstand voltage design against the abnormal voltage at the time of quenching is related to the protection of coils. Therefore, the electrical insulation design of large superconducting magnets is an important subject of study. Their electrical insulation system is the compound system of liquid helium, gaseous helium, vacuum and solid insulators. When a cross magnetic field is applied, insulation breakdown characteristics are aggravated. The mechanism of vacuum insulation breakdown and characteristics, the method of improving withstand voltage using spacers or the electrodes for controlling electric field and so on are reported. (K.I.)

Vacuum maintenance in vacuum insulation panels exemplified with a staggered beam VIP

Energy Technology Data Exchange (ETDEWEB)

Kwon, Jae-Sung; Jang, Choong Hyo; Jung, Haeyong; Song, Tae-Ho [Department of Mechanical Engineering, Korea Advanced Institute of Science and Technology, Guseong-dong 373-1, Yuseong-gu, Daejeon (Korea, Republic of)

2010-05-15

Thermal insulation performance of a vacuum insulation panel (VIP) is highly dependent on the inner pressure of the VIP. Long-term vacuum maintenance characteristics are investigated in this study for a VIP with an example of polymer staggered beam structure as the core material. Various gas sources deteriorating the vacuum level in the VIP are investigated based on theoretical models and experiments. Gas permeation occurring through heat-sealed flanges and pinholes in the barrier envelope is the largest gas leakage source. The calculated gas permeation rate is in accordance with the experimental result. To reduce these permeations, a three-side sealing envelope and double enveloping are proposed. Outgassing from the core material and inner surface of the envelope is also critical. It is significantly reduced by a baking pre-treatment in vacuum. When the estimated total gas load exceeds the allowable limit within a few years, a getter material may be applied. Double enveloping structure with a getter is promising as it ensures a lifetime of more than 20 years. (author)

Vacuum guidelines for ISA insertions

International Nuclear Information System (INIS)

Edwards, D. Jr.

1976-01-01

Vacuum requirements place design restrictions on the ISA insertions. The vacuum tube diameter, given a distance L between pumps, is determined by the desorption of molecules from the wall under the impact of ions created by the beam, whereas the thickness of the tube must be sufficient to prevent collapse. In addition, the entire vacuum chamber must be able to be baked out at approximately 200 0 C

Particle contamination in vacuum systems

International Nuclear Information System (INIS)

Martignac, J.; Bonin, B.; Henriot, C.; Poupeau, J.P.; Koltchakian, I.; Kocic, D.; Herbeaux, Ch.; Marx, J.P.

1996-01-01

Many vacuum devices, like RF cavities, are sensitive to particle contamination. This fact has motivated a considerable effort of cleanliness from the SRF community. The present paper reports the first results of a general study trying to identify the most contaminating steps during assembly and vacuum operation of the cavity. The steps investigated here are gasket assembly, evacuation and venting of the vacuum system, and operation of sputter ion pumps. (author)

Particle contamination in vacuum systems

International Nuclear Information System (INIS)

Martignac, J.; Bonin, B.; Henriot, C.; Poupeau, J.P.; Koltchakian, I.; Kocic, D.; Herbeaux, Ch.; Marx, J.P.

1996-01-01

Many vacuum devices, like RF cavities, are sensitive to particle contamination. This fact has motivated a considerable effort of cleanliness from the SRF community. The first results of a general study trying to identify the most contaminating steps during assembly and vacuum operation of the cavity is reported. The steps investigated here are gasket assembly, evacuation and venting of the vacuum system, and operation of sputter ion pumps. (author)

Research on vacuum insulation for cryocables

International Nuclear Information System (INIS)

Graneau, P.

1974-01-01

Vacuum insulation, as compared with solid insulation, simplifies the construction of both resistive or superconducting cryogenic cables. The common vacuum space in the cable can furnish thermal insulation between the environment and the cryogenic coolant, provide electrical insulation between conductors, and establish thermal isolation between go- and return-coolant streams. The differences between solid and vacuum high voltage insulation are discussed, and research on the design, materials selection, and testing of vacuum insulated cryogenic cables is described

Vacuum-insulated catalytic converter

Science.gov (United States)

Benson, David K.

2001-01-01

A catalytic converter has an inner canister that contains catalyst-coated substrates and an outer canister that encloses an annular, variable vacuum insulation chamber surrounding the inner canister. An annular tank containing phase-change material for heat storage and release is positioned in the variable vacuum insulation chamber a distance spaced part from the inner canister. A reversible hydrogen getter in the variable vacuum insulation chamber, preferably on a surface of the heat storage tank, releases hydrogen into the variable vacuum insulation chamber to conduct heat when the phase-change material is hot and absorbs the hydrogen to limit heat transfer to radiation when the phase-change material is cool. A porous zeolite trap in the inner canister absorbs and retains hydrocarbons from the exhaust gases when the catalyst-coated substrates and zeolite trap are cold and releases the hydrocarbons for reaction on the catalyst-coated substrate when the zeolite trap and catalyst-coated substrate get hot.

Current-induced changes of migration energy barriers in graphene and carbon nanotubes

Science.gov (United States)

Obodo, J. T.; Rungger, I.; Sanvito, S.; Schwingenschlögl, U.

2016-05-01

An electron current can move atoms in a nanoscale device with important consequences for the device operation and breakdown. We perform first principles calculations aimed at evaluating the possibility of changing the energy barriers for atom migration in carbon-based systems. In particular, we consider the migration of adatoms and defects in graphene and carbon nanotubes. Although the current-induced forces are large for both the systems, in graphene the force component along the migration path is small and therefore the barrier height is little affected by the current flow. In contrast, the same barrier is significantly reduced in carbon nanotubes as the current increases. Our work also provides a real-system numerical demonstration that current-induced forces within density functional theory are non-conservative.An electron current can move atoms in a nanoscale device with important consequences for the device operation and breakdown. We perform first principles calculations aimed at evaluating the possibility of changing the energy barriers for atom migration in carbon-based systems. In particular, we consider the migration of adatoms and defects in graphene and carbon nanotubes. Although the current-induced forces are large for both the systems, in graphene the force component along the migration path is small and therefore the barrier height is little affected by the current flow. In contrast, the same barrier is significantly reduced in carbon nanotubes as the current increases. Our work also provides a real-system numerical demonstration that current-induced forces within density functional theory are non-conservative. Electronic supplementary information (ESI) available. See DOI: 10.1039/C6NR00534A

Identification of radiation induced dark current sources in pinned photodiode CMOS image sensors

International Nuclear Information System (INIS)

Goiffon, V.; Virmontois, C.; Magnan, P.; Cervantes, P.; Place, S.; Estribeau, M.; Martin-Gonthier, P.; Gaillardin, M.; Girard, S.; Paillet, P.

2012-01-01

This paper presents an investigation of Total Ionizing Dose (TID) induced dark current sources in Pinned Photodiodes (PPD) CMOS Image Sensors based on pixel design variations. The influence of several layout parameters is studied. Only one parameter is changed at a time enabling the direct evaluation of its contribution to the observed device degradation. By this approach, the origin of radiation induced dark current in PPD is localized on the pixel layout. The PPD peripheral shallow trench isolation does not seem to play a role in the degradation. The PPD area and a transfer gate contribution independent of the pixel dimensions appear to be the main sources of the TID induced dark current increase. This study also demonstrates that applying a negative voltage on the transfer gate during integration strongly reduces the radiation induced dark current. (authors)

REQUIREMENTS AND GUIDELINES FOR NSLS EXPERIMENTAL BEAM LINE VACUUM SYSTEMS-REVISION B

International Nuclear Information System (INIS)

FOERSTER, C.

1999-01-01

Typical beam lines are comprised of an assembly of vacuum valves and shutters referred to as a ''front end'', optical elements to monochromatize, focus and split the photon beam, and an experimental area where a target sample is placed into the photon beam and data from the interaction is detected and recorded. Windows are used to separate sections of beam lines that are not compatible with storage ring ultra high vacuum. Some experimental beam lines share a common vacuum with storage rings. Sections of beam lines are only allowed to vent up to atmospheric pressure using pure nitrogen gas after a vacuum barrier is established to protect ring vacuum. The front end may only be bled up when there is no current in the machine. This is especially true on the VUV storage ring where for most experiments, windows are not used. For the shorter wavelength, more energetic photons of the x-ray ring, beryllium windows are used at various beam line locations so that the monochromator, mirror box or sample chamber may be used in a helium atmosphere or rough vacuum. The window separates ring vacuum from the environment of the downstream beam line components. The stored beam lifetime in the storage rings and the maintenance of desirable reflection properties of optical surfaces depend upon hydrocarbon-free, ultra-high vacuum systems. Storage ring vacuum systems will operate at pressures of ∼ 1 x 10 -10 Torr without beam and ∼ 1 x 10 -9 Torr with beam. Systems are free of hydrocarbons in the sense that no pumps, valves, etc. containing organics are used. Components are all-metal, chemically cleaned and bakeable. To the extent that beam lines share a common vacuum with the storage ring, the same criteria will hold for beam line components. The design philosophy for NSLS beam lines is to use all-metal, hydrocarbon-free front end components and recommend that experimenters use this approach for common vacuum hardware downstream of front ends. O-ring-sealed valves, if used, are not

Spent nuclear fuel project cold vacuum drying facility vacuum and purge system design description

Energy Technology Data Exchange (ETDEWEB)

IRWIN, J.J.

1998-11-30

This document provides the System Design Description (SDD) for the Cold Vacuum Drying Facility (CVDF) Vacuum and Purge System (VPS) . The SDD was developed in conjunction with HNF-SD-SNF-SAR-O02, Safety Analysis Report for the Cold Vacuum Drying Facility, Phase 2, Supporting Installation of Processing Systems (Garvin 1998), The HNF-SD-SNF-DRD-002, 1998, Cold Vacuum Drying Facility Design Requirements, and the CVDF Design Summary Report. The SDD contains general descriptions of the VPS equipment, the system functions, requirements and interfaces. The SDD provides references for design and fabrication details, operation sequences and maintenance. This SDD has been developed for the SNFP Operations Organization and shall be updated, expanded, and revised in accordance with future design, construction and startup phases of the CVDF until the CVDF final ORR is approved.

Spent nuclear fuel project cold vacuum drying facility vacuum and purge system design description

International Nuclear Information System (INIS)

IRWIN, J.J.

1998-01-01

This document provides the System Design Description (SDD) for the Cold Vacuum Drying Facility (CVDF) Vacuum and Purge System (VPS) . The SDD was developed in conjunction with HNF-SD-SNF-SAR-O02, Safety Analysis Report for the Cold Vacuum Drying Facility, Phase 2, Supporting Installation of Processing Systems (Garvin 1998), The HNF-SD-SNF-DRD-002, 1998, Cold Vacuum Drying Facility Design Requirements, and the CVDF Design Summary Report. The SDD contains general descriptions of the VPS equipment, the system functions, requirements and interfaces. The SDD provides references for design and fabrication details, operation sequences and maintenance. This SDD has been developed for the SNFP Operations Organization and shall be updated, expanded, and revised in accordance with future design, construction and startup phases of the CVDF until the CVDF final ORR is approved

Color-magnetic permeability of QCD vacuum

Energy Technology Data Exchange (ETDEWEB)

Saito, T [Kyoto Prefectural Univ. of Medicine (Japan); Shigemoto, K

1980-03-01

In the very strong background gauge field the QCD true vacuum has been shown to have lower energy than the ''perturbative vacuum.'' The color-magnetic permeability of the QCD true vacuum is then calculated to be 1/2 within the quark-one-loop approximation.

Vacuum vessel for thermonuclear device

International Nuclear Information System (INIS)

Kikuchi, Mitsuru; Kurita, Gen-ichi; Onozuka, Masaki; Suzuki, Masaru.

1997-01-01

Heat of inner walls of a vacuum vessel that receive radiation heat from plasmas by way of first walls is removed by a cooling medium flowing in channels for cooling the inner walls. Nuclear heat generation of constitutional materials of the vacuum vessel caused by fast neutrons and γ rays is removed by a cooling medium flowing in cooling channels disposed in the vacuum vessel. Since the heat from plasmas and the nuclear heat generation are removed separately, the amount of the cooling medium flowing in the channels for cooling inner walls is increased for cooling a great amount of heat from plasmas while the amount of the cooling medium flowing in the channels for cooling the inside of the vacuum vessel is reduced for cooling the small amount of nuclear heat generation. Since the amount of the cooling medium can thus be optimized, the capacity of the facilities for circulating the cooling medium can be reduced. In addition, since the channels for cooling the inner walls and the channels of cooling medium formed in the vacuum vessel are disposed to the inner walls of the vacuum vessel on the side opposite to plasmas, integrity of the channels relative to leakage of the cooling medium can be ensured. (N.H.)

Vacuum vessel for thermonuclear device

Energy Technology Data Exchange (ETDEWEB)

Kikuchi, Mitsuru; Kurita, Gen-ichi [Japan Atomic Energy Research Inst., Tokyo (Japan); Onozuka, Masaki; Suzuki, Masaru

1997-07-31

Heat of inner walls of a vacuum vessel that receive radiation heat from plasmas by way of first walls is removed by a cooling medium flowing in channels for cooling the inner walls. Nuclear heat generation of constitutional materials of the vacuum vessel caused by fast neutrons and {gamma} rays is removed by a cooling medium flowing in cooling channels disposed in the vacuum vessel. Since the heat from plasmas and the nuclear heat generation are removed separately, the amount of the cooling medium flowing in the channels for cooling inner walls is increased for cooling a great amount of heat from plasmas while the amount of the cooling medium flowing in the channels for cooling the inside of the vacuum vessel is reduced for cooling the small amount of nuclear heat generation. Since the amount of the cooling medium can thus be optimized, the capacity of the facilities for circulating the cooling medium can be reduced. In addition, since the channels for cooling the inner walls and the channels of cooling medium formed in the vacuum vessel are disposed to the inner walls of the vacuum vessel on the side opposite to plasmas, integrity of the channels relative to leakage of the cooling medium can be ensured. (N.H.)

Current-induced domain wall motion in magnetic nanowires with spatial variation

International Nuclear Information System (INIS)

Ieda, Jun'ichi; Sugishita, Hiroki; Maekawa, Sadamichi

2010-01-01

We model current-induced domain wall motion in magnetic nanowires with the variable width. Employing the collective coordinate method we trace the wall dynamics. The effect of the width modulation is implemented by spatial dependence of an effective magnetic field. The wall destination in the potential energy landscape due to the magnetic anisotropy and the spatial nonuniformity is obtained as a function of the current density. For a nanowire of a periodically modulated width, we identify three (pinned, nonlinear, and linear) current density regimes for current-induced wall motion. The threshold current densities depend on the pulse duration as well as the magnitude of wire modulation. In the nonlinear regime, application of ns order current pulses results in wall displacement which opposes or exceeds the prediction of the spin transfer mechanism. The finding explains stochastic nature of the domain wall displacement observed in recent experiments.

Ultra high vacuum systems for accelerators

International Nuclear Information System (INIS)

Loefgren, P.

2001-01-01

Full text: In order to perform controlled, stable, and reproducible experiments, several research areas today require very low pressures. Maybe the most important example is the research that is performed in storage rings and accelerators where the lifetime and stability of particle beams depends critically on the vacuum conditions. Although the vacuum requirements ultimately depend on the kind of experiments that is performed, the studies of more and more rare and exotic species in storage rings and accelerators today pushes the demands on the vacuum conditions towards lower and lower pressures. The final pressure obtained in the vacuum system can often be the key factor for the outcome of an experiment. Pioneering work in vacuum technology has therefore often been performed at storage rings and accelerator facilities around the world. In order to reach pressures in the low UHV regime and lower (below 10 -11 mbar), several aspects have to be considered which implies choosing the proper materials, pumps and vacuum gauges. In the absence of gases inleaking from the outside, the rate of gas entering a vacuum system is determined by the release of molecules adsorbed on the surfaces and the outgassing from the bulk of the vacuum chamber walls. This means that the choice of material and, equally important, the pre treatment of the material, must be such that these rates are minimised. Today the most widely used material for vacuum applications are stainless steel. Besides its many mechanical advantages, it is resistant to corrosion and oxidation. If treated correctly the major gas source in a stainless steel chamber is hydrogen outgassing from the chamber walls. The hydrogen outgassing can be decreased by vacuum firing at 950 deg. C under vacuum. In addition to choosing the right materials the choice of vacuum pumps is important for the final pressure. Since no vacuum pump is capable of taking care of all kinds of gases found in the rest gas at pressures below 10 -11

Wireless Integrated Microelectronic Vacuum Sensor System

Science.gov (United States)

Krug, Eric; Philpot, Brian; Trott, Aaron; Lawrence, Shaun

2013-01-01

NASA Stennis Space Center's (SSC's) large rocket engine test facility requires the use of liquid propellants, including the use of cryogenic fluids like liquid hydrogen as fuel, and liquid oxygen as an oxidizer (gases which have been liquefied at very low temperatures). These fluids require special handling, storage, and transfer technology. The biggest problem associated with transferring cryogenic liquids is product loss due to heat transfer. Vacuum jacketed piping is specifically designed to maintain high thermal efficiency so that cryogenic liquids can be transferred with minimal heat transfer. A vacuum jacketed pipe is essentially two pipes in one. There is an inner carrier pipe, in which the cryogenic liquid is actually transferred, and an outer jacket pipe that supports and seals the vacuum insulation, forming the "vacuum jacket." The integrity of the vacuum jacketed transmission lines that transfer the cryogenic fluid from delivery barges to the test stand must be maintained prior to and during engine testing. To monitor the vacuum in these vacuum jacketed transmission lines, vacuum gauge readings are used. At SSC, vacuum gauge measurements are done on a manual rotation basis with two technicians, each using a handheld instrument. Manual collection of vacuum data is labor intensive and uses valuable personnel time. Additionally, there are times when personnel cannot collect the data in a timely fashion (i.e., when a leak is detected, measurements must be taken more often). Additionally, distribution of this data to all interested parties can be cumbersome. To simplify the vacuum-gauge data collection process, automate the data collection, and decrease the labor costs associated with acquiring these measurements, an automated system that monitors the existing gauges was developed by Invocon, Inc. For this project, Invocon developed a Wireless Integrated Microelectronic Vacuum Sensor System (WIMVSS) that provides the ability to gather vacuum

Baking results of KSTAR vacuum vessel

International Nuclear Information System (INIS)

Kim, S. T.; Kim, Y. J.; Kim, K. M.; Im, D. S.; Joung, N. Y.; Yang, H. L.; Kim, Y. S.; Kwon, M.

2009-01-01

The Korea Superconducting Tokamak Advanced Research (KSTAR) is an advanced superconducting tokamak designed to establish a scientific and technological basis for an attractive fusion reactor. The fusion energy in the tokamak device is released through fusion reactions of light atoms such as deuterium or helium in hot plasma state, of which temperature reaches several hundreds of millions Celsius. The high temperature plasma is created in the vacuum vessel that provides ultra high vacuum status. Accordingly, it is most important for the vacuum condition to keep clean not only inner space but also surface of the vacuum vessel to make high quality plasma. There are two methods planned to clean the wall surface of the KSTAR vacuum vessel. One is surface baking and the other is glow discharge cleaning (GDC). To bake the vacuum vessel, De-Ionized (DI) water is heated to 130 .deg. C and circulated in the passage between double walls of the vacuum vessel (VV) in order to bake the surface. The GDC operation uses hydrogen and inert gas discharges. In this paper, general configuration and brief introduction of the baking result will be reported

Baking results of KSTAR vacuum vessel

Energy Technology Data Exchange (ETDEWEB)

Kim, S. T.; Kim, Y. J.; Kim, K. M.; Im, D. S.; Joung, N. Y.; Yang, H. L.; Kim, Y. S.; Kwon, M. [National Fusion Research Institute, Daejeon (Korea, Republic of)

2009-05-15

The Korea Superconducting Tokamak Advanced Research (KSTAR) is an advanced superconducting tokamak designed to establish a scientific and technological basis for an attractive fusion reactor. The fusion energy in the tokamak device is released through fusion reactions of light atoms such as deuterium or helium in hot plasma state, of which temperature reaches several hundreds of millions Celsius. The high temperature plasma is created in the vacuum vessel that provides ultra high vacuum status. Accordingly, it is most important for the vacuum condition to keep clean not only inner space but also surface of the vacuum vessel to make high quality plasma. There are two methods planned to clean the wall surface of the KSTAR vacuum vessel. One is surface baking and the other is glow discharge cleaning (GDC). To bake the vacuum vessel, De-Ionized (DI) water is heated to 130 .deg. C and circulated in the passage between double walls of the vacuum vessel (VV) in order to bake the surface. The GDC operation uses hydrogen and inert gas discharges. In this paper, general configuration and brief introduction of the baking result will be reported.

All-metal vacuum chamber for the ZT-40 experiment

International Nuclear Information System (INIS)

Dike, R.S.; Downing, J.N.

1981-10-01

We discuss the design and fabrication of the all-metal vacuum chamber presently in use in the ZT-40 device. ZT-40 is the current experiment in the Los Alamos Reversed-Field Pinch (RFP) program. The new vessel, which replaces a ceramic one, is made of Inconel 625 and has major and minor diameters of 228 cm and 40 cm, respectively. It consists of 24 convoluted and straight sections welded into a single toroidal geometry. Presented are several design features showing diagnostic and vacuum port tubulations and thermal-electrical insulation isolating the unit from its conducting shell. We also discuss fabrication techniques and our procedure for cleaning and heat treatment designed to eliminate residual gas contamination in the Inconel material

Climate-Induced Boreal Forest Change: Predictions versus Current Observations

Science.gov (United States)

Soja, Amber J.; Tchebakova, Nadezda M.; French, Nancy H. F.; Flannigan, Michael D.; Shugart, Herman H.; Stocks, Brian J.; Sukhinin, Anatoly I.; Parfenova, E. I.; Chapin, F. Stuart, III; Stackhouse, Paul W., Jr.

2007-01-01

For about three decades, there have been many predictions of the potential ecological response in boreal regions to the currently warmer conditions. In essence, a widespread, naturally occurring experiment has been conducted over time. In this paper, we describe previously modeled predictions of ecological change in boreal Alaska, Canada and Russia, and then we investigate potential evidence of current climate-induced change. For instance, ecological models have suggested that warming will induce the northern and upslope migration of the treeline and an alteration in the current mosaic structure of boreal forests. We present evidence of the migration of keystone ecosystems in the upland and lowland treeline of mountainous regions across southern Siberia. Ecological models have also predicted a moisture-stress-related dieback in white spruce trees in Alaska, and current investigations show that as temperatures increase, white spruce tree growth is declining. Additionally, it was suggested that increases in infestation and wildfire disturbance would be catalysts that precipitate the alteration of the current mosaic forest composition. In Siberia, five of the last seven years have resulted in extreme fire seasons, and extreme fire years have also been more frequent in both Alaska and Canada. In addition, Alaska has experienced extreme and geographically expansive multi-year outbreaks of the spruce beetle, which had been previously limited by the cold, moist environment. We suggest that there is substantial evidence throughout the circumboreal region to conclude that the biosphere within the boreal terrestrial environment has already responded to the transient effects of climate change. Additionally, temperature increases and warming-induced change are progressing faster than had been predicted in some regions, suggesting a potential non-linear rapid response to changes in climate, as opposed to the predicted slow linear response to climate change.

Influence of Joule heating on current-induced domain wall depinning

Energy Technology Data Exchange (ETDEWEB)

Moretti, Simone, E-mail: simone.moretti@usal.es; Raposo, Victor; Martinez, Eduardo [University of Salamanca, Plaza de los Caidos, 37008 Salamanca (Spain)

2016-06-07

The domain wall depinning from a notch in a Permalloy nanostrip on top of a SiO{sub 2}/Si substrate is studied theoretically under application of static magnetic fields and the injection of short current pulses. The influence of Joule heating on current-induced domain wall depinning is explored self-consistently by coupling the magnetization dynamics in the ferromagnetic strip to the heat transport throughout the system. Our results indicate that Joule heating plays a remarkable role in these processes, resulting in a reduction in the critical depinning field and/or in a temporary destruction of the ferromagnetic order for typically injected current pulses. In agreement with experimental observations, similar pinning-depinning phase diagrams can be deduced for both current polarities when the Joule heating is taken into account. These observations, which are incompatible with the sole contribution of spin transfer torques, provide a deeper understanding of the physics underlying these processes and establish the real scope of the spin transfer torque. They are also relevant for technological applications based on current-induced domain-wall motion along soft strips.

Sequestration of vacuum energy and the end of the universe.

Science.gov (United States)

Kaloper, Nemanja; Padilla, Antonio

2015-03-13

Recently, we proposed a mechanism for sequestering the standard model vacuum energy that predicts that the Universe will collapse. Here we present a simple mechanism for bringing about this collapse, employing a scalar field whose potential is linear and becomes negative, providing the negative energy density required to end the expansion. The slope of the potential is chosen to allow for the expansion to last until the current Hubble time, about 10^{10} years, to accommodate our Universe. Crucially, this choice is technically natural due to a shift symmetry. Moreover, vacuum energy sequestering selects radiatively stable initial conditions for the collapse, which guarantee that immediately before the turnaround the Universe is dominated by the linear potential which drives an epoch of accelerated expansion for at least an e fold. Thus, a single, technically natural choice for the slope ensures that the collapse is imminent and is preceded by the current stage of cosmic acceleration, giving a new answer to the "why now?"

Probing wavenumbers of current-induced excitations in point-contact experiments

Directory of Open Access Journals (Sweden)

Z Wei

2010-06-01

Full Text Available Z Wei, M TsoiDepartment of Physics, Center for Nano and Molecular Science and Technology, and Texas Materials Institute, The University of Texas at Austin, Austin, TX, USAAbstract: We demonstrate how a mechanical point-contact technique can provide information on the wavenumber of spin waves excited by high-density electrical current in magnetic multilayers. By varying the size of point-contacts, we have been able to control the size of the excitation volume and therefore the wavelength of current-induced spin waves. This leads to a technique with in situ sensitivity to wavenumbers of current-induced excitations. Our detailed size-dependent measurements support the prediction that the excited wavelength is determined by the contact size.Keywords: spin transfer torque, giant magnetoresistance, spin waves, point contact

Evacuation of the NET vacuum chamber

International Nuclear Information System (INIS)

Muller, R.A.

1987-01-01

Parametric calculations of the evacuation process were carried out for the NET-vacuum chamber involving two blanket designs. The results show that with an acceptable vacuum pumping capacity the required start vacuum conditions can be realized within reasonable time. The two blanket concepts do not differ remarkably in their evacuation behaviour. The remaining large pressure differences between the different locations of the vacuum chamber can be reduced if approximately 30% of the total gas flow is extracted from the heads of the blanket replacement ports

Evacuation of the NET vacuum chamber

International Nuclear Information System (INIS)

Mueller, R.

1986-01-01

Parametric calculations of the evacuation process were carried out for the NET-vacuum chamber involving two blanket designs. The results show that with an acceptable vacuum pumping capacity the required start vacuum conditions can be realized within reasonable time. The two blanket concepts do not differ remarkably in their evacuation behaviour. The remaining large pressure differences between the different locations of the vacuum chamber can be reduced if approximately 30% of the total gas flow is extracted from the heads of the blanket replacement ports. (author)

Vacuum Bellows, Vacuum Piping, Cryogenic Break, and Copper Joint Failure Rate Estimates for ITER Design Use

Energy Technology Data Exchange (ETDEWEB)

L. C. Cadwallader

2010-06-01

The ITER international project design teams are working to produce an engineering design in preparation for construction of the International Thermonuclear Experimental Reactor (ITER) tokamak. During the course of this work, questions have arisen in regard to safety barriers and equipment reliability as important facets of system design. The vacuum system designers have asked several questions about the reliability of vacuum bellows and vacuum piping. The vessel design team has asked about the reliability of electrical breaks and copper-copper joints used in cryogenic piping. Research into operating experiences of similar equipment has been performed to determine representative failure rates for these components. The following chapters give the research results and the findings for vacuum system bellows, power plant stainless steel piping (amended to represent vacuum system piping), cryogenic system electrical insulating breaks, and copper joints.

Is there Still a Place for Vacuum Extraction (Ventouse) in Modern ...

African Journals Online (AJOL)

2nd stage of labor and other common clinical problems.[2] Thus, instrumental ... an “air tractor vacuum extractor” was devised by the developer ... Currently, about 4‑13% of maternal deaths in Africa, Asia, ..... behavior or health care outcomes?

Scientific basis and engineering design to accommodate disruption and halo current loads for the DIII-D tokamak

Energy Technology Data Exchange (ETDEWEB)

Anderson, P.M.; Bozek, A.S.; Hollerbach, M.A.; Humphreys, D.A.; Luxon, J.L.; Reis, E.E.; Schaffer, M.J.

1996-10-01

Plasma disruptions and halo current events apply sudden impulsive forces to the interior structures and vacuum vessel walls of tokamaks. These forces arise when induced toroidal currents and attached poloidal halo currents in plasma facing components interact with the poloidal and toroidal magnetic fields respectively. Increasing understanding of plasma disruptions and halo current events has been developed from experiments on DIII-D and other machines. Although the understanding has improved, these events must be planned for in system design because there is no assurance that these events can be eliminated in the operation of tokamaks. Increased understanding has allowed an improved focus of engineering designs.

Scientific basis and engineering design to accommodate disruption and halo current loads for the DIII-D tokamak

International Nuclear Information System (INIS)

Anderson, P.M.; Bozek, A.S.; Hollerbach, M.A.; Humphreys, D.A.; Luxon, J.L.; Reis, E.E.; Schaffer, M.J.

1996-10-01

Plasma disruptions and halo current events apply sudden impulsive forces to the interior structures and vacuum vessel walls of tokamaks. These forces arise when induced toroidal currents and attached poloidal halo currents in plasma facing components interact with the poloidal and toroidal magnetic fields respectively. Increasing understanding of plasma disruptions and halo current events has been developed from experiments on DIII-D and other machines. Although the understanding has improved, these events must be planned for in system design because there is no assurance that these events can be eliminated in the operation of tokamaks. Increased understanding has allowed an improved focus of engineering designs

Function and operation of the Doublet III E-coil vacuum breaker system

International Nuclear Information System (INIS)

Callis, R.W.; Jackson, G.; DeGrassie, J.; Peterson, P.; LeVine, F.

1979-11-01

The ohmic heating system for the Doublet III fusion research device at General Atomic is required to provide the voltage for the initial breakdown phase (there is no preionization) along with the energy to drive the plasma current to a value of 2.5 MA or greater. This requires a peak one turn voltage of 250 volts (16 kV across coil terminals) and a magnetic flux swing of 5 volt-seconds (peak coil current of 110 kA). This voltage and flux swing is accomplished by reverse biasing the ohmic heating coil (E-coil) where, upon reaching a value of 110 ka the coil current is interrupted and commutated into a RC network producing 16 kV across the coil. The interrruption of the E-coil current is accomplished by the use of an array of vacuum circuit breakers (VCB's) and a counter plus network. A description is given of the ohmic heating circuit and the performance of the vacuum circuit breaker array and its counter pulse system

The vacuum vessel for the FTU device: design constraints and stress analysis

International Nuclear Information System (INIS)

Andreani, R.; Cecchini, A.; Gasparotto, M.; Lovisetto, L.; Migliori, S.; Pizzuto, A.

1984-01-01

The FTU vacuum vessel must withstand large electromagnetic loads due to the interactions between the eddy currents in the vessel and high magnetic fields of the machine, the atmospheric pressure and the severe thermal loads due to plasma losses and RF power not coupled to the plasma. In order to minimise the stresses on the vacuum chamber, an optimization of the wall thickness has been performed and, in order to assess the feasibility of the vessel, an extensive three dimensional finite element stress analysis has been developed. The main results obtained are illustrated. (author)

Big Bang or vacuum fluctuation

International Nuclear Information System (INIS)

Zel'dovich, Ya.B.

1980-01-01

Some general properties of vacuum fluctuations in quantum field theory are described. The connection between the ''energy dominance'' of the energy density of vacuum fluctuations in curved space-time and the presence of singularity is discussed. It is pointed out that a de-Sitter space-time (with the energy density of the vacuum fluctuations in the Einstein equations) that matches the expanding Friedman solution may describe the history of the Universe before the Big Bang. (P.L.)

Concept for a MEMS-type vacuum sensor based on electrical conductivity measurements

Directory of Open Access Journals (Sweden)

F. J. Giebel

2017-11-01

Full Text Available The concept of the micro-structured vacuum sensor presented in this article is the measurement of the electrical conductivity of thinned gases in order to develop a small, economical and quite a simple type of vacuum sensor. There are already some approaches for small vacuum sensors. Most of them are based on conservative measurement principles similar to those used in macroscopic vacuum gauges. Ionization gauges use additional sources of energy, like hot cathodes, ultraviolet radiation or high voltage for example, for ionizing gas molecules and thereby increasing the number of charge carriers for measuring low pressures. In contrast, the concept discussed here cannot be found in macroscopic sensor systems because it depends on the microscopic dimension of a gas volume defined by two electrodes. Here we present the concept and the production of a micro-structured vacuum sensor chip, followed by the electrical characterization. Reference measurements with electrodes at a distance of about 1 mm showed currents in the size of picoampere and a conductivity depending on ambient pressure. In comparison with these preliminary measurements, fundamental differences regarding pressure dependence of the conductivity are monitored in the electrical characterization of the micro-structured sensor chip. Finally the future perspectives of this sensor concept are discussed.

Vacuum vessel for thermonuclear device

International Nuclear Information System (INIS)

Kikuchi, Mitsuru; Nagashima, Keisuke; Suzuki, Masaru; Onozuka, Masaki.

1997-01-01

A vacuum vessel main body and structural members at the inside and the outside of the vacuum vessel main body are constituted by structural materials activated by irradiation of neutrons from plasmas such as stainless steels. Shielding members comprising tungsten or molybdenum are disposed on the surface of the vacuum vessel main body and the structural members of the inside and the outside of the main body. The shielding members have a function also as first walls or a seat member for the first walls. Armor tiles may be disposed to the shielding members. The shielding members and the armor tiles are secured to a securing seat member disposed, for example, to an inner plate of the vacuum vessel main body by bolts. Since the shielding members are disposed, it is not necessary to constitute the vacuum vessel main body and the structural members at the inside and the outside thereof by using a low activation material which is less activated, such as a titanium alloy. (I.N.)

Vacuum vessel for thermonuclear device

Energy Technology Data Exchange (ETDEWEB)

Kikuchi, Mitsuru; Nagashima, Keisuke [Japan Atomic Energy Research Inst., Tokyo (Japan); Suzuki, Masaru; Onozuka, Masaki

1997-07-11

A vacuum vessel main body and structural members at the inside and the outside of the vacuum vessel main body are constituted by structural materials activated by irradiation of neutrons from plasmas such as stainless steels. Shielding members comprising tungsten or molybdenum are disposed on the surface of the vacuum vessel main body and the structural members of the inside and the outside of the main body. The shielding members have a function also as first walls or a seat member for the first walls. Armor tiles may be disposed to the shielding members. The shielding members and the armor tiles are secured to a securing seat member disposed, for example, to an inner plate of the vacuum vessel main body by bolts. Since the shielding members are disposed, it is not necessary to constitute the vacuum vessel main body and the structural members at the inside and the outside thereof by using a low activation material which is less activated, such as a titanium alloy. (I.N.)

Structure of the QCD vacuum and hadrons

International Nuclear Information System (INIS)

Shuryak, E.

1996-01-01

Recent studies have provided strong arguments in favor of the idea that most hadrons (including the nucleon) are actually bound not because of confining forces, but mainly due to the instanton-induced forces. Quite different effective interactions in various mesonic and baryonic channels can be explained in this way. Moreover, many hadronic parameters and even the point-to-point correlation functions are quantitatively reproduced by the simplest possible ensemble of instantons, the so-called ''Random Instanton Liquid Model'' (RILM). Recent lattice works have confirmed it, essentially deriving the ''instanton vacuum'' from lattice configuration by their ''cooling''. At non-zero temperatures the (quark-induced) interaction between instantons becomes much stronger, and at the critical temperature T=T c the chiral symmetry becomes restored, due to ''pairing'' of the instantons and the anti-instantons into a kind of ''I I molecules''. (orig.)

Design consideration on the synchrotron ultrahigh vacuum system

International Nuclear Information System (INIS)

Tsujikawa, H.; Chida, K.; Mizobuchi, A.; Miyahara, A.

1982-01-01

Ultrahigh vacuum production for the high-energy heavy-ion accelerator poses special problems concerning beam-gas molecule and beam-wall interactions. In this paper, summary of the TARN ultrahigh vacuum system and design criteria of the synchrotron ultrahigh vacuum system are presented. On-beam pressure of 4 x 10 -11 Torr is achieved in the TARN ultrahigh vacuum system, of which experiences through the construction and the operation are described and discussed. With emphasis on the application of newly developed technique in the fabrication of vacuum chamber and ultrahigh vacuum pump for the synchrotron ultrahigh vacuum system. (author)

Polarized X-Ray Emission from Magnetized Neutron Stars: Signature of Strong-Field Vacuum Polarization

Science.gov (United States)

Lai, Dong; Ho, Wynn C.

2003-08-01

In the atmospheric plasma of a strongly magnetized neutron star, vacuum polarization can induce a Mikheyev-Smirnov-Wolfenstein type resonance across which an x-ray photon may (depending on its energy) convert from one mode into the other, with significant changes in opacities and polarizations. We show that this vacuum resonance effect gives rise to a unique energy-dependent polarization signature in the surface emission from neutron stars. The detection of polarized x rays from neutron stars can provide a direct probe of strong-field quantum electrodynamics and constrain the neutron star magnetic field and geometry.

Polarized x-ray emission from magnetized neutron stars: signature of strong-field vacuum polarization.

Science.gov (United States)

Lai, Dong; Ho, Wynn C G

2003-08-15

In the atmospheric plasma of a strongly magnetized neutron star, vacuum polarization can induce a Mikheyev-Smirnov-Wolfenstein type resonance across which an x-ray photon may (depending on its energy) convert from one mode into the other, with significant changes in opacities and polarizations. We show that this vacuum resonance effect gives rise to a unique energy-dependent polarization signature in the surface emission from neutron stars. The detection of polarized x rays from neutron stars can provide a direct probe of strong-field quantum electrodynamics and constrain the neutron star magnetic field and geometry.

High vacuum general purpose scattering chamber for nuclear reaction study

International Nuclear Information System (INIS)

Suresh Kumar; Ojha, S.C.

2003-01-01

To study the nuclear reactions induced by beam from medium energy accelerators, one of the most common facility required is a scattering chamber. In the scattering chamber, projectile collides with the target nucleus and the scattered reaction products are detected with various type of nuclear detector at different angles with respect to the beam. The experiments are performed under high vacuum to minimize the background reaction and the energy losses of the charged particles. To make the chamber general purpose various requirement of the experiments are incorporated into it. Changing of targets, changing angle of various detectors while in vacuum are the most desired features. The other features like ascertaining the beam spot size and position on the target, minimizing the background counts by proper beam dump, accurate positioning of the detector as per plan etc. are some of the important requirements

Vacuum status-display and sector-conditioning programs

International Nuclear Information System (INIS)

Skelly, J.; Yen, S.

1989-01-01

Two programs have been developed for observation and control of the AGS vacuum system, which include these notable features: they incorporate a graphical user interface, and they are driven by a relational database which describes the vacuum system. The vacuum system comprises some 440 devices organized into 28 vacuum sectors. The Status Display Program invites menu selection of a sector, interrogates the relational database for relevant vacuum devices, acquires live readbacks, and posts a graphical display of their status. The Sector Conditioning Program likewise invites sector selection, produces the same status display, and also implements process control logic on the sector devices to pump the sector down from atmospheric pressure to high vacuum over a period extending for several hours. As additional devices are installed in the vacuum system, the devices are likewise added to the relational database; these programs then automatically include the new devices. 2 refs., 1 fig

Dynamical effects of QCD vacuum structure

International Nuclear Information System (INIS)

Ferreira, Erasmo

1994-01-01

The role of the QCD vacuum structure in the determination of the properties of states and processes occurring in the confinement regime of QCD is reviewed. The finite range of the vacuum correlations is discussed, and an analytical form is suggested for the correlation functions. The role of the vacuum quantum numbers in the phenomenology of high-energy scattering is reviewed. The vacuum correlation model of non-perturbative QCD is mentioned as a bridge between the fundamental theory and the description of the experiments. (author). 13 refs., 1 fig

Vacuum technology in the chemical industry

CERN Document Server

Jorisch, Wolfgang

2015-01-01

Based on the very successful German edition and a seminar held by the German Engineers` Association (VDI) on a regular basis for years now, this English edition has been thoroughly updated and revised to reflect the latest developments. It supplies in particular the special aspects of vacuum technology, applied vacuum pump types and vacuum engineering in the chemical, pharmaceutical and process industry application-segments. The text includes chapters dedicated to latest European regulations for operating in hazardous zones with vacuum systems, methods for process pressure control and regulati

Running vacuum cosmological models: linear scalar perturbations

Energy Technology Data Exchange (ETDEWEB)

Perico, E.L.D. [Instituto de Física, Universidade de São Paulo, Rua do Matão 1371, CEP 05508-090, São Paulo, SP (Brazil); Tamayo, D.A., E-mail: elduartep@usp.br, E-mail: tamayo@if.usp.br [Departamento de Astronomia, Universidade de São Paulo, Rua do Matão 1226, CEP 05508-900, São Paulo, SP (Brazil)

2017-08-01

In cosmology, phenomenologically motivated expressions for running vacuum are commonly parameterized as linear functions typically denoted by Λ( H {sup 2}) or Λ( R ). Such models assume an equation of state for the vacuum given by P-bar {sub Λ} = - ρ-bar {sub Λ}, relating its background pressure P-bar {sub Λ} with its mean energy density ρ-bar {sub Λ} ≡ Λ/8π G . This equation of state suggests that the vacuum dynamics is due to an interaction with the matter content of the universe. Most of the approaches studying the observational impact of these models only consider the interaction between the vacuum and the transient dominant matter component of the universe. We extend such models by assuming that the running vacuum is the sum of independent contributions, namely ρ-bar {sub Λ} = Σ {sub i} ρ-bar {sub Λ} {sub i} . Each Λ i vacuum component is associated and interacting with one of the i matter components in both the background and perturbation levels. We derive the evolution equations for the linear scalar vacuum and matter perturbations in those two scenarios, and identify the running vacuum imprints on the cosmic microwave background anisotropies as well as on the matter power spectrum. In the Λ( H {sup 2}) scenario the vacuum is coupled with every matter component, whereas the Λ( R ) description only leads to a coupling between vacuum and non-relativistic matter, producing different effects on the matter power spectrum.

46 CFR 154.804 - Vacuum protection.

Science.gov (United States)

2010-10-01

... 46 Shipping 5 2010-10-01 2010-10-01 false Vacuum protection. 154.804 Section 154.804 Shipping... Systems § 154.804 Vacuum protection. (a) Except as allowed under paragraph (b) of this section, each cargo tank must have a vacuum protection system meeting paragraph (a)(1) of this section and either paragraph...

Mass corrections to Green functions in instanton vacuum model

International Nuclear Information System (INIS)

Esaibegyan, S.V.; Tamaryan, S.N.

1987-01-01

The first nonvanishing mass corrections to the effective Green functions are calculated in the model of instanton-based vacuum consisting of a superposition of instanton-antiinstanton fluctuations. The meson current correlators are calculated with account of these corrections; the mass spectrum of pseudoscalar octet as well as the value of the kaon axial constant are found. 7 refs

Vacuum Mechatronics And Insvection For Self-Contained Manufacturing

Science.gov (United States)

Belinski, Steve E.; Shirazi, Majid; Seidel, Thomas E.; Hackwood, Susan

1990-02-01

The vacuum environment is increasingly being used in manufacturing operations, especially in the semiconductor industry. Shrinking linewidths and feature sizes dictate that cleanliness standards become continually more strict. Studies at the Center for Robotic Systems in Microelectronics (CRSM) indicate that a controlled vacuum enclosure can provide a superior clean environment. In addition, since many microelectronic fabrication steps are already carried out under vacuum, self-contained multichamber processing systems are being developed at a rapid pace. CRSM support of these systems includes the development of a research system, the Self-contained Automated Robotic Factory (SCARF), a vacuum-compatible robot, and investigations of particulate characterization in vacuum and inspection for multichamber systems. Successful development of complex and expensive multichamber systems is, to a great extent, dependent upon the discipline called vacuum mechatronics, which includes the design and development of vacuum-compatible computer-controlled mechanisms for manipulating, sensing and testing in a vacuum environment. Here the constituents of the vacuum mechatronics discipline are defined and reviewed in the context of the importance to self-contained in-vacuum manufacturing.

Vacuum system for HIMAC synchrotrons

International Nuclear Information System (INIS)

Kanazawa, M.; Sudou, M.; Sato, K.

1994-01-01

HIMAC synchrotrons are now under construction, which require vacuum chambers of large aperture and high vacuum of about 10 -9 torr. Wide thin wall vacuum chamber of 0.3 mm thickness reinforced with ribs has been developed as the chamber at dipole magnet. We have just now started to evacuate the lower ring. The obtained average value was about 5x10 -8 torr with turbo-molecular and sputter ion pumps, and 1.1x10 -9 torr after baking. (author)

ITER diagnostic system: Vacuum interface

Energy Technology Data Exchange (ETDEWEB)

Patel, K.M., E-mail: Kaushal.Patel@iter.org [ITER Organization, Route de Vinon sur Verdon, 13115 St Paul-Lez-Durance (France); Udintsev, V.S.; Hughes, S.; Walker, C.I.; Andrew, P.; Barnsley, R.; Bertalot, L. [ITER Organization, Route de Vinon sur Verdon, 13115 St Paul-Lez-Durance (France); Drevon, J.M. [Bertin Technologies, BP 22, 13762 Aix-en Provence cedex 3 (France); Encheva, A. [ITER Organization, Route de Vinon sur Verdon, 13115 St Paul-Lez-Durance (France); Kashchuk, Y. [Institution “PROJECT CENTER ITER”, 1, Akademika Kurchatova pl., Moscow (Russian Federation); Maquet, Ph. [Bertin Technologies, BP 22, 13762 Aix-en Provence cedex 3 (France); Pearce, R.; Taylor, N.; Vayakis, G.; Walsh, M.J. [ITER Organization, Route de Vinon sur Verdon, 13115 St Paul-Lez-Durance (France)

2013-10-15

Diagnostics play an essential role for the successful operation of the ITER tokamak. They provide the means to observe control and to measure plasma during the operation of ITER tokamak. The components of the diagnostic system in the ITER tokamak will be installed in the vacuum vessel, in the cryostat, in the upper, equatorial and divertor ports, in the divertor cassettes and racks, as well as in various buildings. Diagnostic components that are placed in a high radiation environment are expected to operate for the life of ITER. There are approx. 45 diagnostic systems located on ITER. Some diagnostics incorporate direct or independently pumped extensions to maintain their necessary vacuum conditions. They require a base pressure less than 10{sup −7} Pa, irrespective of plasma operation, and a leak rate of less than 10{sup −10} Pa m{sup 3} s{sup −1}. In all the cases it is essential to maintain the ITER closed fuel cycle. These directly coupled diagnostic systems are an integral part of the ITER vacuum containment and are therefore subject to the same design requirements for tritium and active gas confinement, for all normal and accidental conditions. All the diagnostics, whether or not pumped, incorporate penetration of the vacuum boundary (i.e. window assembly, vacuum feedthrough etc.) and demountable joints. Monitored guard volumes are provided for all elements of the vacuum boundary that are judged to be vulnerable by virtue of their construction, material, load specification etc. Standard arrangements are made for their construction and for the monitoring, evacuating and leak testing of these volumes. Diagnostic systems are incorporated at more than 20 ports on ITER. This paper will describe typical and particular arrangements of pumped diagnostic and monitored guard volume. The status of the diagnostic vacuum systems, which are at the start of their detailed design, will be outlined and the specific features of the vacuum systems in ports and extensions

ITER diagnostic system: Vacuum interface

International Nuclear Information System (INIS)

Patel, K.M.; Udintsev, V.S.; Hughes, S.; Walker, C.I.; Andrew, P.; Barnsley, R.; Bertalot, L.; Drevon, J.M.; Encheva, A.; Kashchuk, Y.; Maquet, Ph.; Pearce, R.; Taylor, N.; Vayakis, G.; Walsh, M.J.

2013-01-01

Diagnostics play an essential role for the successful operation of the ITER tokamak. They provide the means to observe control and to measure plasma during the operation of ITER tokamak. The components of the diagnostic system in the ITER tokamak will be installed in the vacuum vessel, in the cryostat, in the upper, equatorial and divertor ports, in the divertor cassettes and racks, as well as in various buildings. Diagnostic components that are placed in a high radiation environment are expected to operate for the life of ITER. There are approx. 45 diagnostic systems located on ITER. Some diagnostics incorporate direct or independently pumped extensions to maintain their necessary vacuum conditions. They require a base pressure less than 10 −7 Pa, irrespective of plasma operation, and a leak rate of less than 10 −10 Pa m 3 s −1 . In all the cases it is essential to maintain the ITER closed fuel cycle. These directly coupled diagnostic systems are an integral part of the ITER vacuum containment and are therefore subject to the same design requirements for tritium and active gas confinement, for all normal and accidental conditions. All the diagnostics, whether or not pumped, incorporate penetration of the vacuum boundary (i.e. window assembly, vacuum feedthrough etc.) and demountable joints. Monitored guard volumes are provided for all elements of the vacuum boundary that are judged to be vulnerable by virtue of their construction, material, load specification etc. Standard arrangements are made for their construction and for the monitoring, evacuating and leak testing of these volumes. Diagnostic systems are incorporated at more than 20 ports on ITER. This paper will describe typical and particular arrangements of pumped diagnostic and monitored guard volume. The status of the diagnostic vacuum systems, which are at the start of their detailed design, will be outlined and the specific features of the vacuum systems in ports and extensions will be described

Analysis of conditions for magnetron discharge initiation at vacuum camera testing

International Nuclear Information System (INIS)

Tzeneva, Raina; Dineff, Peter; Darjanova, Denitza

2002-01-01

Models of electric field distribution for two typical cases of vacuum camera internal pressure control are investigated. New relations between the maximum magnetron discharge current value I max and the maximum electric field strength radial component value E τ max are established. (Author)

Problems for superstring models with vacuum expectation values for conjugate sneutrinos

International Nuclear Information System (INIS)

Campbell, B.; Ellis, J.; Gaillard, M.K.; Nanopoulos, D.V.; Olive, K.A.

1986-01-01

Superstring models compactified on Calabi-Yau manifolds contain two new neutral scalars in each 27 generation of chiral supermultiplets. We consider implications of a vacuum expectation value for one of the neutral scalars, the conjugates neutrino ν tilde L c : L c vertical stroke0>=y. Apart from a coupling which generates a Dirac neutrino mass and which must be small [ -9 )], its only superpotential interaction is with D L d L , so there wold be D-d mixing if y≠0. The fact that m d is not much less than m e or m u then tells us that y ν , arises if y≠0, and the D-d mixing would then induce the decay K→π+a ν at an unacceptable rate. Regardless of the gauge group rank, we show that the combined constraints on D-d mixing, and on the flavour-changing neutral currents it would induce, are sufficient to rule out D L d L c ν L c superpotential coupling large enough to produce L c vertical stroke0>≠0. These problems are avoided in models with a rank-5 gauge group and L c vertical stroke0>< or approx.40 KeV. (orig.)

Vacuum arcing behavior between transverse magnetic field contacts subjected to variable axial magnetic field

Science.gov (United States)

Ma, Hui; Wang, Jianhua; Liu, Zhiyuan; Geng, Yingsan; Wang, Zhenxing; Yan, Jing

2016-06-01

The objective of this work is to reveal the effects of an axial magnetic field (AMF) on the vacuum arc characteristics between transverse magnetic field (TMF) contacts. These vacuum arc characteristics include the vacuum arcing behavior and the arc voltage waveform. In the experiments, an external AMF was applied to a pair of TMF contacts. The external AMF flux density BAMF can be adjusted from 0 to 110 mT. The arc current in the tests varied over a range from 0 to 20 kA rms at 45 Hz. The contact material was CuCr25 (25% Cr). A high-speed charge-coupled device video camera was used to record the vacuum arc evolution. The experimental results show that the application of the AMF effectively reduces the TMF arc voltage noise component and reduces the formation of liquid metal drops between the contacts. The diffuse arc duration increases linearly with increasing AMF flux density, but it also decreases linearly with increasing arc current under application of the external AMF. The results also indicate that the diffuse arc duration before the current zero is usually more than 1 ms under the condition that the value of the AMF per kiloampere is more than 2.0 mT/kA. Finally, under application of the AMF, the arc column of the TMF contacts may constrict and remain in the center region without transverse rotation. Therefore, the combined TMF-AMF contacts should be designed such that they guarantee that the AMF is not so strong as to oppose transverse rotation of the arc column.

Rotary bayonets for cryogenic and vacuum service

International Nuclear Information System (INIS)

Rucinski, R.A.; Dixon, K.D.; Krasa, R.; Krempetz, K.J.; Mulholland, G.T.; Trotter, G.R.; Urbin, J.B.

1993-07-01

Rotary bayonets were designed, tested, and installed for liquid nitrogen, liquid argon, and vacuum service. This paper will present the design, testing, and service record for two sizes of vacuum jacketed cryogenic rotary bayonets and two sizes of vacuum service rotary bayonets. Materials used in construction provide electrical isolation across the bayonet joint. The joint permits 360 degrees of rotation between the male and female pipe sections while maintaining integrity of service. Assemblies using three such joints were built to allow end connection points to be translated through at least 1 meter of horizontal travel while kept in service. Vacuum jacketed sizes built in-house at Fermi National Accelerator Laboratory are 1-1/2 in. inner pipe size, 3 in. vacuum jacket, and 4 in. inner pipe size, 6 in. vacuum jacket The single wall vacuum service bayonets are in 4 in. and 6 in. pipe sizes. The bayonets have successfully been in active service for over one year

Rotary bayonets for cryogenic and vacuum service

International Nuclear Information System (INIS)

Rucinski, R.A.; Dixon, K.D.; Krasa, R.; Krempetz, K.J.; Mulholland, G.T.; Trotter, G.R.; Urbin, J.B.

1994-01-01

Rotary bayonets were designed, tested, and installed for liquid nitrogen, liquid argon, and vacuum service. This paper will present the design, testing, and service record for two sizes of vacuum jacketed cryogenic rotary bayonets and two sizes of vacuum service rotary bayonets. Materials used in construction provide electrical isolation across the bayonet joint. The joint permits 360 degrees of rotation between the male and female pipe sections while maintaining integrity of service. Assemblies using three such joints were built to allow end connection points to be translated through at least 1 meter of horizontal travel while kept in service. Vacuum jacketed sizes built in-house at Fermi National Accelerator Laboratory are 1 1/2 inches inner pipe size, 3 inches vacuum jacket, and 4 inches inner pipe size, 6 inches vacuum jacket. The single wall vacuum service bayonets are in 4 inch and 6 inch pipe sizes. The bayonets have successfully been in active service for over one year

Photocurrent, Rectification, and Magnetic Field Symmetry of Induced Current Through Quantum Dots

DEFF Research Database (Denmark)

DiCarlo, L.; M. Marcus, C.; Harris jr, J.

2003-01-01

We report mesoscopic dc current generation in an open chaotic quantum dot with ac excitation applied to one of the shape-defining gates. For excitation frequencies large compared to the inverse dwell time of electrons in the dot (i.e., GHz), we find mesoscopic fluctuations of induced current...... that are fully asymmetric in the applied perpendicular magnetic field, as predicted by recent theory. Conductance, measured simultaneously, is found to be symmetric in field. In the adiabatic (i.e., MHz) regime, in contrast, the induced current is always symmetric in field, suggesting its origin is mesoscopic...

Life cycle environmental impacts of vacuum cleaners and the effects of European regulation

Energy Technology Data Exchange (ETDEWEB)

Gallego-Schmid, Alejandro, E-mail: alejandro.gallegoschmid@manchester.ac.uk; Mendoza, Joan Manuel F.; Jeswani, Harish Kumar; Azapagic, Adisa

2016-07-15

Energy efficiency of vacuum cleaners has been declining over the past decades while at the same time their number in Europe has been increasing. The European Commission has recently adopted an eco-design regulation to improve the environmental performance of vacuum cleaners. In addition to the existing directive on waste electrical and electronic equipment (WEEE), the regulation could potentially have significant effects on the environmental performance of vacuum cleaners. However, the scale of the effects is currently unknown, beyond scant information on greenhouse gas emissions. Thus, this paper considers for the first time life cycle environmental impacts of vacuum cleaners and the effects of the implementation of these regulations at the European level. The effects of electricity decarbonisation, product lifetime and end-of-life disposal options are also considered. The results suggest that the implementation of the eco-design regulation alone will reduce significantly the impacts from vacuum cleaners (37%–44%) by 2020 compared with current situation. If business as usual continued and the regulation was not implemented, the impacts would be 82%–109% higher by 2020 compared to the impacts with the implementation of the regulation. Improvements associated with the implementation of the WEEE directive will be much smaller (< 1% in 2020). However, if the WEEE directive did not exist, then the impacts would be 2%–21% higher by 2020 relative to the impacts with the implementation of the directive. Further improvements in most impacts (6%–20%) could be achieved by decarbonising the electricity mix. Therefore, energy efficiency measures must be accompanied by appropriate actions to reduce the environmental impacts of electricity generation; otherwise, the benefits of improved energy efficiency could be limited. Moreover, because of expected lower life expectancy of vacuum cleaners and limited availability of some raw materials, the eco-design regulation should

Life cycle environmental impacts of vacuum cleaners and the effects of European regulation

International Nuclear Information System (INIS)

Gallego-Schmid, Alejandro; Mendoza, Joan Manuel F.; Jeswani, Harish Kumar; Azapagic, Adisa

2016-01-01

Energy efficiency of vacuum cleaners has been declining over the past decades while at the same time their number in Europe has been increasing. The European Commission has recently adopted an eco-design regulation to improve the environmental performance of vacuum cleaners. In addition to the existing directive on waste electrical and electronic equipment (WEEE), the regulation could potentially have significant effects on the environmental performance of vacuum cleaners. However, the scale of the effects is currently unknown, beyond scant information on greenhouse gas emissions. Thus, this paper considers for the first time life cycle environmental impacts of vacuum cleaners and the effects of the implementation of these regulations at the European level. The effects of electricity decarbonisation, product lifetime and end-of-life disposal options are also considered. The results suggest that the implementation of the eco-design regulation alone will reduce significantly the impacts from vacuum cleaners (37%–44%) by 2020 compared with current situation. If business as usual continued and the regulation was not implemented, the impacts would be 82%–109% higher by 2020 compared to the impacts with the implementation of the regulation. Improvements associated with the implementation of the WEEE directive will be much smaller (< 1% in 2020). However, if the WEEE directive did not exist, then the impacts would be 2%–21% higher by 2020 relative to the impacts with the implementation of the directive. Further improvements in most impacts (6%–20%) could be achieved by decarbonising the electricity mix. Therefore, energy efficiency measures must be accompanied by appropriate actions to reduce the environmental impacts of electricity generation; otherwise, the benefits of improved energy efficiency could be limited. Moreover, because of expected lower life expectancy of vacuum cleaners and limited availability of some raw materials, the eco-design regulation should

Physical electronics handbook of vacuum physics

CERN Document Server

Beck, A H

2013-01-01

Handbook of Vacuum Physics, Volume 2, Physical Electronics, discusses the fundamentals of electric discharges in gases. Electrical discharges in gases is used generically to denote the passage of electricity through a gas and implicitly embraces the wide variety of physical phenomena which accompany such a discharge of electricity. The discharge currents may be as small as 10-16A in certain ionization growth studies, or be as large as megamperes in thermonuclear and plasma physics studies. Key topics discussed include collision phenomena in gases; surface phenomena and transport of charged par

A low-cost non-intercepting beam current and phase monitor for heavy ions

International Nuclear Information System (INIS)

Bogaty, J.M.; Clifft, B.E.

1995-01-01

A low cost ion beam measurement system has been developed for use at ATLAS. The system provides nondestructive phase and intensity measurement of passing ion beam bunches by sensing their electric fields. Bunches traverse a short tubular electrode thereby inducing displacement currents. These currents are brought outside the vacuum jacket where a lumped inductance resonates electrode capacitance at one of the bunching harmonic frequencies. This configuration yields a basic sensitivity of a few hundred millivolts signal per microampere of beam current. Beam induced radiofrequency signals are summed against an offset frequency generated by the master oscillator. The resulting difference frequency conveys beam intensity and bunch phase information which is sent to separate processing channels. One channel utilizes a phase locked loop to stabilize phase readings during microsecond beam drop outs. The other channel uses a linear full-wave active rectifier circuit which converts sine wave signal amplitude to a DC voltage representing beam current. Plans are in progress to install this new diagnostic at several locations in ATLAS which should help shorten the tuning cycle of new ion species

REQUIREMENTS AND GUIDELINES FOR NSLS EXPERIMENTAL BEAM LINE VACUUM SYSTEMS-REVISION B.

Energy Technology Data Exchange (ETDEWEB)

FOERSTER,C.

1999-05-01

Typical beam lines are comprised of an assembly of vacuum valves and shutters referred to as a ''front end'', optical elements to monochromatize, focus and split the photon beam, and an experimental area where a target sample is placed into the photon beam and data from the interaction is detected and recorded. Windows are used to separate sections of beam lines that are not compatible with storage ring ultra high vacuum. Some experimental beam lines share a common vacuum with storage rings. Sections of beam lines are only allowed to vent up to atmospheric pressure using pure nitrogen gas after a vacuum barrier is established to protect ring vacuum. The front end may only be bled up when there is no current in the machine. This is especially true on the VUV storage ring where for most experiments, windows are not used. For the shorter wavelength, more energetic photons of the x-ray ring, beryllium windows are used at various beam line locations so that the monochromator, mirror box or sample chamber may be used in a helium atmosphere or rough vacuum. The window separates ring vacuum from the environment of the downstream beam line components. The stored beam lifetime in the storage rings and the maintenance of desirable reflection properties of optical surfaces depend upon hydrocarbon-free, ultra-high vacuum systems. Storage ring vacuum systems will operate at pressures of {approximately} 1 x 10{sup {minus}10} Torr without beam and {approximately} 1 x 10{sup {minus}9} Torr with beam. Systems are free of hydrocarbons in the sense that no pumps, valves, etc. containing organics are used. Components are all-metal, chemically cleaned and bakeable. To the extent that beam lines share a common vacuum with the storage ring, the same criteria will hold for beam line components. The design philosophy for NSLS beam lines is to use all-metal, hydrocarbon-free front end components and recommend that experimenters use this approach for common vacuum hardware

Design foundation of vacuum system for electron beam machine

International Nuclear Information System (INIS)

Darsono; Suprapto; Djasiman

1999-01-01

Vacuum system is a main part of electron beam Machine because (EBM) the electron can not be produced without this vacuum. Vacuum system consists of vacuum pump, connecting pipe, valve, and vacuum gauge. The design vacuum system of EBM, basis knowledge and technology of vacuum is needed. The paper describes types of vacuum pump, calculation of pipe conductance and pumping time of vacuum system then there are used as consideration of criteria to choose vacuum pump for EBM. From the result of study, it is concluded that for EBM of 500 keV/10 mA which is going to use for wood coating and with consideration of economic and technic factor it is better to use diffusion pump. (author)

Development of a vacuum superinsulation panel

Energy Technology Data Exchange (ETDEWEB)

Timm, H; Seefeldt, D; Nitze, C

1983-05-01

After completion of the investigations the vacuum-insulated panel is available as prototype. The aim of the investigations was to optimize and to finalize the vacuum superinsulation system with regard to a pressure-resistant, temperature-resistant thermal insulation of high efficiency. In this connection, particularly investigations with regard to vacuum-tight sealing, compression and evacuation of powder filling as well as special material investigations were performed. The application-specific utilization of the vacuum-insulated panel and the adjustment to special operational conditions can now be started. Application possibilities are at present seen in coverings or linings with high temperature and/or pressure requirements.

Current-induced changes of migration energy barriers in graphene and carbon nanotubes.

Science.gov (United States)

Obodo, J T; Rungger, I; Sanvito, S; Schwingenschlögl, U

2016-05-21

An electron current can move atoms in a nanoscale device with important consequences for the device operation and breakdown. We perform first principles calculations aimed at evaluating the possibility of changing the energy barriers for atom migration in carbon-based systems. In particular, we consider the migration of adatoms and defects in graphene and carbon nanotubes. Although the current-induced forces are large for both the systems, in graphene the force component along the migration path is small and therefore the barrier height is little affected by the current flow. In contrast, the same barrier is significantly reduced in carbon nanotubes as the current increases. Our work also provides a real-system numerical demonstration that current-induced forces within density functional theory are non-conservative.

Vacuum pulse conditioning and risetime sharpening on a low nu/gamma multi-MEV electron beam accelerator

International Nuclear Information System (INIS)

Stringfield, R.M.; Bartsch, R.R.; Davis, H.A.; Sherwood, E.G.

1986-01-01

The surface flashover switch interrupts the cathode stalk of the vacuum transmission line near the load. The flashover voltage is controlled by varying the switch length, with a maximum flashover voltage of 3MV. A diode element immediately upstream of the switch allows current to build up in the inductance of the vacuum transmission line while the switch is open. Upon switch closure, the axial current flowing the the load acts as a bias current to magnetically inhibit current flow in the upstream diode. This diode serves the additional purpose, with or without the flashover switch, of diverting a controlled portion of the total machine current form the load by varying the AK spacing. This feature provides the capability to vary the current and voltage at the load outside the simple constraints of the accelerator's load line. An examination of the performance of the switch and the diode is presented

Effects of vacuum rapid thermal annealing on the electrical characteristics of amorphous indium gallium zinc oxide thin films

Science.gov (United States)

Lee, Hyun-Woo; Cho, Won-Ju

2018-01-01

We investigated the effects of vacuum rapid thermal annealing (RTA) on the electrical characteristics of amorphous indium gallium zinc oxide (a-IGZO) thin films. The a-IGZO films deposited by radiofrequency sputtering were subjected to vacuum annealing under various temperature and pressure conditions with the RTA system. The carrier concentration was evaluated by Hall measurement; the electron concentration of the a-IGZO film increased and the resistivity decreased as the RTA temperature increased under vacuum conditions. In a-IGZO thin-film transistors (TFTs) with a bottom-gate top-contact structure, the threshold voltage decreased and the leakage current increased as the vacuum RTA temperature increased. As the annealing pressure decreased, the threshold voltage decreased, and the leakage current increased. X-ray photoelectron spectroscopy indicated changes in the lattice oxygen and oxygen vacancies of the a-IGZO films after vacuum RTA. At higher annealing temperatures, the lattice oxygen decreased and oxygen vacancies increased, which suggests that oxygen was diffused out in a reduced pressure atmosphere. The formation of oxygen vacancies increased the electron concentration, which consequently increased the conductivity of the a-IGZO films and reduced the threshold voltage of the TFTs. The results showed that the oxygen vacancies and electron concentrations of the a-IGZO thin films changed with the vacuum RTA conditions and that high-temperature RTA treatment at low pressure converted the IGZO thin film to a conductor.

Vacuum and ultravacuum physics and technology

CERN Document Server

Bello, Igor

2018-01-01

Vacuum technology has enormous impact on human life in many aspects and fields, such as metallurgy, material development and production, food and electronic industry, microelectronics, device fabrication, physics, materials science, space science, engineering, chemistry, technology of low temperature, pharmaceutical industry, and biology. All decorative coatings used in jewelries and various daily products—including shiny decorative papers, the surface finish of watches, and light fixtures—are made using vacuum technological processes. Vacuum analytical techniques and vacuum technologies are pillars of the technological processes, material synthesis, deposition, and material analyses—all of which are used in the development of novel materials, increasing the value of industrial products, controlling the technological processes, and ensuring the high product quality. Based on physical models and calculated examples, the book provides a deeper look inside the vacuum physics and technology.

Comprehending the structure of a vacuum vessel and in-vessel components of fusion machines. 1. Comprehending the vacuum vessel structure

International Nuclear Information System (INIS)

Onozuka, Masanori; Nakahira, Masataka

2006-01-01

The functions, conditions and structure of vacuum vessel using tokamak fusion machines are explained. The structural standard and code of vacuum vessel, process of vacuum vessel design, and design of ITER vacuum vessel are described. Production and maintenance of ultra high vacuum, confinement of radioactive materials, support of machines in vessel and electromagnetic force, radiation shield, plasma vertical stability, one-turn electric resistance, high temperature baking heat and remove of nuclear heat, reduce of troidal ripple, structural standard, features of safety of nuclear fusion machines, subjects of structural standard of fusion vacuum vessel, design flow of vacuum vessel, establishment of radial build, selections of materials, baking and cooling method, basic structure, structure of special parts, shield structure, and of support structure, and example of design of structure, ITER, are stated. (S.Y.)

PREFACE: International Symposium on `Vacuum Science and Technology' (IVS 2007)

Science.gov (United States)

Mittal, K. C.; Gupta, S. K.

2008-03-01

The Indian Vacuum Society (established in 1970) has organized a symposium every alternate year on various aspects of vacuum science and technology. There has been considerable participation from R & D establishments, universities and Indian industry in this event. In view of the current global scenario and emerging trends in vacuum technology, this year, the executive committee of IVS felt it appropriate to organize an international symposium at Tata Institute of Fundamental Research, Colaba, Mumbai 400 005 from 29-30 November 2007. This symposium provided a forum for exchange of information among vacuum scientists, technologists and industrialists on recent advances made in the areas of large vacuum systems, vacuum production, its measurement and applications in industry, and material processing in vacuum. Vacuum science and technology has made vital contributions in high tech areas like space, high energy particle accelerators, large plasma systems, electronics, thin films, melting and refining of metals, extraction and processing of advanced materials etc. The main areas covered in the symposium were the production and measurement of vacuums, leak detection, large vacuum systems, vacuum metallurgy, vacuum materials and processing inclusive of applications of vacuum in industry. Large vacuum systems for high energy particle accelerators, plasma devices and light sources are of special significance for this symposium. Vacuum evaporation, hard coatings, thin films, joining techniques, sintering, melting and heat treatment, furnaces and thermo dynamics are also covered in this symposium. There were eighteen invited talks from the best experts in the respective fields and more than one hundred contributed papers. This fact itself indicates the interest that has been generated amongst the scientists, technologists and industrialists in this field. In view of the industrial significance of the vacuum technology, an exhibition of vacuum and vacuum processing related

Structural analysis of the ITER vacuum vessel from disruption loading with halo asymmetry

International Nuclear Information System (INIS)