Two-coordinate mini drift chamber operating in a self-quenching streamer mode

International Nuclear Information System (INIS)

Chernenko, S.P.; Smykov, L.P.; Zanevskij, Yu.V.

1993-01-01

Two-coordinate mini drift chambers operating in a self-quenching streamer mode have been developed. The tests have demonstrated these chambers to possess an extended counting plateau, a high operating stability and a high uniformity of efficiency over detecting area. The space resolution along anode wires is not worse than 250μm; the expected space resolution for the second coordinate is about 100 μm

Influence of gas mixture and primary ionization on the performance of limit streamer mode tubes

International Nuclear Information System (INIS)

An Jigang; Anderson, K.J.; Merritt, F.S.; Oreglia, M.; Pilcher, J.E.; Possoz, A.; Schappert, W.; Chicago Univ., IL

1988-01-01

We report a study of the dependence of limited streamer mode operation on gas composition. Results are given for the plateau onset voltage, plateau length, charge versus voltage, charge spectra and pulse width for various fractions of (Ar, CO 2 , pentane) and (Ar, isobutane). In addition, a series of argon-free strong quenching gas mixtures has been studied which have very attractive characteristics. Chamber lifetime tests for these are also reported. As part of a study of the nature of the limited streamer mode mechanism, the response to X-rays and minimum ionizing particles are compared and differences noted. The character of the primary ionization is found to have a clear effect on the chamber response even in the streamer region. (orig.)

High-voltage test and training of plastic streamer tubes for the DELPHI hadron calorimeter

International Nuclear Information System (INIS)

Alekseev, G.D.; Cellar, S.; Khomenko, B.A.; Korytov, A.V.; Kulinich, P.A.; Micelmacher, G.V.; Sedykh, Yu.V.; Toledo, R.

1987-01-01

The results of high-voltage test and training of plastic streamer tubes of the DELPHI hadron calorimeter are presented. The testing technique is considered in detail. The equipment for high-voltage training consists of a mini-computer, CAMAC-electronics, a controllable high-voltage supply and a digital ampermeter. The experimental results shows that high-voltage training of streamer tubes improves their characteristics. The value of dark current decreased up to 1 μA. The operational voltage range increased by a value more than 300 V

Streamer Evaporation

Science.gov (United States)

Suess, Steven T.; Wang, A. H.; Wu, Shi T.; Nerney, S.

1998-01-01

Evaporation is the consequence of slow plasma heating near the tops of streamers where the plasma is only weakly contained by the magnetic field. The form it takes is the slow opening of field lines at the top of the streamer and transient formation of new solar wind. It was discovered in polytropic model calculations, where due to the absence of other energy loss mechanisms in magnetostatic streamers, its ultimate endpoint is the complete evaporation of the streamer. This takes, for plausible heating rates, weeks to months in these models. Of course streamers do not behave this way, for more than one reason. One is that there are losses due to thermal conduction to the base of the streamer and radiation from the transition region. Another is that streamer heating must have a characteristic time constant and depend on the ambient physical conditions. We use our global Magnetohydrodynamics (MHD) model with thermal conduction to examine a few examples of the effect of changing the heating scale height and of making ad hoc choices for how the heating depends on ambient conditions. At the same time, we apply and extend the analytic model of streamers, which showed that streamers will be unable to contain plasma for temperatures near the cusp greater than about 2xl0(exp 6) K. Slow solar wind is observed to come from streamers through transient releases. A scenario for this that is consistent with the above physical process is that heating increases the near-cusp temperature until field lines there are forced open. The subsequent evacuation of the flux tubes by the newly forming slow wind decreases the temperature and heating until the flux tubes are able to reclose. Then, over a longer time scale, heating begins to again refill the flux tubes with plasma and increase the temperature until the cycle repeats itself. The calculations we report here are first steps towards quantitative evaluation of this scenario.

CCD camera system for use with a streamer chamber

International Nuclear Information System (INIS)

Angius, S.A.; Au, R.; Crawley, G.C.; Djalali, C.; Fox, R.; Maier, M.; Ogilvie, C.A.; Molen, A. van der; Westfall, G.D.; Tickle, R.S.

1988-01-01

A system based on three charge-coupled-device (CCD) cameras is described here. It has been used to acquire images from a streamer chamber and consists of three identical subsystems, one for each camera. Each subsystem contains an optical lens, CCD camera head, camera controller, an interface between the CCD and a microprocessor, and a link to a minicomputer for data recording and on-line analysis. Image analysis techniques have been developed to enhance the quality of the particle tracks. Some steps have been made to automatically identify tracks and reconstruct the event. (orig.)

Studies of the stability and sistematics of operation of the DELPHI plastic streamer tubes

International Nuclear Information System (INIS)

Alekseev, G.D.; Bilenky, M.S.; Bonyushkin, Yu.Ye.; Korrytov, A.V.

1989-01-01

The influeNce of gas pressure and temperature, slight changes in a gas mixture, self-sustaining discharge, aging, different deviations in the detector geometry on the operation of the DELPHI plastic streamer tubes is studied. The contribution of these factors to the DELPHI hadron calorimeter energy resolution is estimated. The major influence is found to be due to atmospheric pressure fluctuations (∼ ±1% streamer charge change per ±1 Torr). The question of the choice of a gas mixture is studied as well. Maximal streamer charge is shown to be independent of component concentrations in the Ar:CO 2 :i-C 4 H 10 ) or C 5 H 12 ) gas mixtures. 23 refs.; 21 figs.; 1 tab

Display of a proton-proton interaction as seen in the streamer chamber of NA5

CERN Multimedia

CERN PhotoLab

1979-01-01

This experiment was performed by the Bari-Cracow-Liverpool-Munich (MPI)-Nijmegen Collaboration using the unseparated H2 beam in the EHN1 hall. The setup consisted of a three-gap streamer chamber (2x1.4x0.72 m3) inside a superconducting vertex magnet, large magnetostrictive spark chambers, proportional chambers and beam defining counters. A large acceptance electron and hadron calorimeter completed the setup. Particles from beam interactions on a target, 36.5 cm long, 2 cm in diameter (for liquid hydrogen) located inside the chamber at its entrance were photographed. Multiplicities, rapidity distributions, and correlations were studied for interactions with a large value for the sum of the transverse momenta.

A Barrel IFR Instrumented With Limited Streamer Tubes for BABAR Experiment

International Nuclear Information System (INIS)

Andreotti, M.; Ferrara U.; INFN, Ferrara

2006-01-01

The new barrel Instrumented Flux Return (IFR) of BABAR detector will be reported here. Limited Streamer Tubes (LSTs) have been chosen to replace the existing RPCs as active elements of the barrel IFR. The layout of the new detector will be discussed: in particular, a cell bigger than the standard one has been used to improve efficiency and reliability. The extruded profile is coated with a resistive layer of graphite having a typical surface resistivity between 0.2 and 0.4 MOhm/square. The tubes are assembled in modules and installed in 12 active layers of each sextant of the IFR detector. R and D studies to choose the final design and Quality Control procedure adopted during the tube production will be briefly discussed. Finally the performances of installed LSTs into 2/3 of IFR after 8 months of operations will be reported

Self-quenching streamers

International Nuclear Information System (INIS)

Atac, M.; Tollestrup, A.V.; Potter, D.

1982-01-01

Self quenching streamers in drift tubes have been observed both optically and electronically. The streamers of 150-200 μm width extend out from the anode wire to 1.5 to 3 mm at atmospheric pressures. Electronic measurements at a two atomsphere pressure show pulses into a 50 Ω load with a rise time of 5 ns, a decay time of 40 ns, and an amplitude of 30 mV. Details of the experiments are discussed. There was no detectable residue on an anode wire after exposing it to 2x10 9 streamers for a 1 mm section. (orig.)

Analysis and interpretation of the performance degradation of glass Resistive Plate Chambers operated in streamer mode

CERN Document Server

Calcaterra, A; Patteri, P; Piccolo, M; Della Mea, G; Restello, S; Ferri, F; Musella, P; Redaelli, N; Tabarelli de Fatis, T; Tinti, G; Mannocchi, G; Trinchero, G

2007-01-01

The long-term stability of Resistive Plate Chambers (RPCs) with glass electrodes was studied for one year with a dedicated test station hosting about 10 m2 of detectors. RPCs were operated in streamer mode with a ternary gas mixture containing argon (27%), isobutane (9%) and tetrafluoroethane (64%). Environmental conditions were kept under control and, in particular, the water pollution in the gas, deemed responsible for the degradation of glass RPC performance, was monitored never to exceed 30 ppm in the exhaust line. Evidence for a substantial aging of the detectors was observed, resulting in a loss of efficiency correlated to an increased rate of spurious streamers. This can be ascribed to the chemical attack of the glass surface by hydrofluoric acid formed in the streamer process, as confirmed by detailed morphological and chemical analyses of the electrode surface. Our results strengthen the indication that the instability of glass RPCs in the long term is related to the use of fluorocarbons as quenching...

Reversal film development for streamer chamber track photographs

International Nuclear Information System (INIS)

Bahr, J.

1982-01-01

It is the aim of this work to create a method of photographic development specially adapted to streamer image recording, i.e., with high sensitivity, only two signal levels, low dependence of the track signal on image intensity having a great jitter and noise suppression. The method has to be suitable for machine development of high speed films. A reversal photographic development was used to realize these demands, whereby strong fogging in the first step negative development and a solving process for silver bromide after blackening are specially introduced process stages. This results in a step-function shaped characteristic curve with small transition region having only two signal levels, i. e., independence of streamer image density, good resolution, fine grain, suppression of flares and low noise in the signal of the clear streamer images

Triangular tube proportional wire chamber system

Energy Technology Data Exchange (ETDEWEB)

Badtke, D H; Bakken, J A; Barnett, B A; Blumenfeld, B J; Chien, C Y; Madansky, L; Matthews, J A.J.; Pevsner, A; Spangler, W J [Johns Hopkins Univ., Baltimore, MD (USA); Lee, K L [California Univ., Berkeley (USA). Lawrence Berkeley Lab.

1981-10-15

We report on the characteristics of the proportional tube chamber system which has been constructed for muon identification in the PEP-4 experiment at SLAC. The mechanical and electrical properties of the extruded aluminum triangular tubes allow these detectors to be used as crude drift chambers.

The thin-wall tube drift chamber operating in vacuum (prototype)

Science.gov (United States)

Alexeev, G. D.; Glonti, L. N.; Kekelidze, V. D.; Malyshev, V. L.; Piskun, A. A.; Potrbenikov, Yu. K.; Rodionov, V. K.; Samsonov, V. A.; Tokmenin, V. V.; Shkarovskiy, S. N.

2013-08-01

The goal of this work was to design drift tubes and a chamber operating in vacuum, and to develop technologies for tubes independent assembly and mounting in the chamber. These design and technology were tested on the prototype. The main features of the chamber are the following: the drift tubes are made of flexible mylar film (wall thickness 36 μm, diameter 9.80 mm, length 2160 mm) using ultrasonic welding along the generatrix; the welding device and methods were developed at JINR. Drift tubes with end plugs, anode wires and spacers were completely assembled outside the chamber. "Self-centering" spacers and bushes were used for precise setting of the anode wires and tubes. The assembled tubes were sealed with O-rings in their seats in the chamber which simplified the chamber assembling. Moreover the tube assembly and the chamber manufacture can be performed independently and in parallel; this sufficiently reduces the total time of chamber manufacture and assembling, its cost and allows tubes to be tested outside the chamber. The technology of independent tube assembling is suitable for a chamber of any shape but a round chamber is preferable for operation in vacuum. Single channel amplifier-discriminator boards which are more stable against cross talks were used for testing the tubes. Independently assembled tubes were mounted into the chamber prototype and its performance characteristic measured under the vacuum conditions. The results showed that both the structure and the tubes themselves normally operate. They are suitable for making a full-scale drift chamber for vacuum.

The thin-wall tube drift chamber operating in vacuum (prototype)

International Nuclear Information System (INIS)

Alexeev, G.D.; Glonti, L.N.; Kekelidze, V.D.; Malyshev, V.L.; Piskun, A.A.; Potrbenikov, Yu.K.; Rodionov, V.K.; Samsonov, V.A.; Tokmenin, V.V.; Shkarovskiy, S.N.

2013-01-01

The goal of this work was to design drift tubes and a chamber operating in vacuum, and to develop technologies for tubes independent assembly and mounting in the chamber. These design and technology were tested on the prototype. The main features of the chamber are the following: the drift tubes are made of flexible mylar film (wall thickness 36 μm, diameter 9.80 mm, length 2160 mm) using ultrasonic welding along the generatrix; the welding device and methods were developed at JINR. Drift tubes with end plugs, anode wires and spacers were completely assembled outside the chamber. “Self-centering” spacers and bushes were used for precise setting of the anode wires and tubes. The assembled tubes were sealed with O-rings in their seats in the chamber which simplified the chamber assembling. Moreover the tube assembly and the chamber manufacture can be performed independently and in parallel; this sufficiently reduces the total time of chamber manufacture and assembling, its cost and allows tubes to be tested outside the chamber. The technology of independent tube assembling is suitable for a chamber of any shape but a round chamber is preferable for operation in vacuum. Single channel amplifier-discriminator boards which are more stable against cross talks were used for testing the tubes. Independently assembled tubes were mounted into the chamber prototype and its performance characteristic measured under the vacuum conditions. The results showed that both the structure and the tubes themselves normally operate. They are suitable for making a full-scale drift chamber for vacuum

The thin-wall tube drift chamber operating in vacuum (prototype)

Energy Technology Data Exchange (ETDEWEB)

Alexeev, G.D. [Joint Institute for Nuclear Research, Dubna (Russian Federation); Glonti, L.N., E-mail: glonti@sunse.jinr.ru [Joint Institute for Nuclear Research, Dubna (Russian Federation); Kekelidze, V.D.; Malyshev, V.L.; Piskun, A.A.; Potrbenikov, Yu.K.; Rodionov, V.K.; Samsonov, V.A.; Tokmenin, V.V.; Shkarovskiy, S.N. [Joint Institute for Nuclear Research, Dubna (Russian Federation)

2013-08-01

The goal of this work was to design drift tubes and a chamber operating in vacuum, and to develop technologies for tubes independent assembly and mounting in the chamber. These design and technology were tested on the prototype. The main features of the chamber are the following: the drift tubes are made of flexible mylar film (wall thickness 36 μm, diameter 9.80 mm, length 2160 mm) using ultrasonic welding along the generatrix; the welding device and methods were developed at JINR. Drift tubes with end plugs, anode wires and spacers were completely assembled outside the chamber. “Self-centering” spacers and bushes were used for precise setting of the anode wires and tubes. The assembled tubes were sealed with O-rings in their seats in the chamber which simplified the chamber assembling. Moreover the tube assembly and the chamber manufacture can be performed independently and in parallel; this sufficiently reduces the total time of chamber manufacture and assembling, its cost and allows tubes to be tested outside the chamber. The technology of independent tube assembling is suitable for a chamber of any shape but a round chamber is preferable for operation in vacuum. Single channel amplifier-discriminator boards which are more stable against cross talks were used for testing the tubes. Independently assembled tubes were mounted into the chamber prototype and its performance characteristic measured under the vacuum conditions. The results showed that both the structure and the tubes themselves normally operate. They are suitable for making a full-scale drift chamber for vacuum.

SIMUL - a program for the simulation of interactions in the streamer chamber RISK

International Nuclear Information System (INIS)

Friebel, W.; Gajewski, J.; Halm, I.

1976-08-01

A program for the simulation of interactions in the streamer chamber RISK is described. This program allows first investigations and tests for planning and preparing experiments. In the program the trajectories of all particles taking part in the interaction are computed. Selected points are projected onto film planes serving as measurement points for the use in the geometrical reconstruction. The program is used for testing a geometry program. But it also seems to be very helpful in investigating counter and trigger constellations and in the calculation of counting rates and trigger effectivities. (author)

Multiwire proportional chambers in the triggering system of the streamer chamber for high-Pt charged particle production detection in 40 GeV/c hadron-nucleus interactions

International Nuclear Information System (INIS)

Czyrkowski, H.; Dabrowski, R.; Derlicki, A.

1985-01-01

We describe a triggering system based on the multiwire proportional chambers (MWPCs) for the high-P t charged particles selection in Π - A interactions at 40 GeV/c (RISC experiment). The coincidence matrices processing only combinations of hits in MWPCs allow one to reach sufficient purity of experimental material. The large area MWPCs work close to the streamer chamber high voltage electrode without any problems. Details of the fabrication procedure and peformances are also given. 12 refs. (author)

Properties of self-quenching streamer (SQS) tubes

International Nuclear Information System (INIS)

Koori, N.; Nohtomi, A.; Hashimoto, M.; Yoshioka, K.; Kumabe, I.

1989-01-01

The self-quenching streamer (SQS) mode of gas counters have been widely used for measuring high energy particles. The authors have very recently found that all the rare gas (He, Ne, Ar and Xe) mixtures with quenching gas of CH 4 , C 2 H 6 , C 3 H 8 , iso-C 4 H 10 or CO 2 can be used as gas mixtures for the SQS mode except Ne- and He-mixtures with CH 4 or CO 2 . Further studies on the properties of this mode are needed for its application to monitoring devices. Properties of a self-quenching tube are discussed here from this point of view. Gas multiplication properties, pulse shape of current signals, and dead zone are measured under several gas pressures equal to or less than one atomospheric pressure. Either the SQS or GM mode can be obtained by changing the gas pressure with a cylindrical gas counter. The operation mode of the counter may be correctly determined from the dead zone measurement. The measurements show that the SQS and GM modes are exclusive, even though SQS's can be simultaneously formed with a GM discharge. The counting rate capability of the SQS mode is higher than that of the GM mode by about one order of magnitude. Thus, SQS tubes are suitable for use in high flux radiation fields. (N.K.)

On the data compression at filmless readout of the streamer chamber information

International Nuclear Information System (INIS)

Bajla, I.; Ososkov, G.A.; Prikhod'ko, V.I.

1980-01-01

It is supposed that the system of filmless detecting and processing the visual information from ''RISK'' streamer chamber will comprise the effective on-line data compression algorithm. The role of the basic methodological principles of chamber image film processing in Righ Energy Physics for building up such system is analysed. On the basis of this analysis the main requirements are formulated that have to be fulfilled by the compression algorithm. The most important requirement consists in securing the possibility of the input data reprocessing, if problems in the off-line recognition occur. Using a vector system representation of primary data, the on-line data compression philosophy is proposed that embodies the following three principles: universality, parallelism and input data reconstructibility. Excluding of the recognition procedure from the on-line compression algorithm causes the compression factor reduction. The hierarchic structure of the compression algorithm consisting of (1) sorting, (2) filtering, (3) compression for an additional increasing of the compression ratio is proposed

Cylindrical multiwire two-coordinate chamber with foam-polyurethane supporting element

International Nuclear Information System (INIS)

Vakhtin, V.G.; Travkin, V.I.

1988-01-01

Construction and technology of producing the two-coordinate cylindrical chamber with foam-polyurethane supporting element are described. Use of foam-polyurethane permits to reduce the substance quantity at particle path up to 0.2 g/cm 2 . The supporting element represents a foam-polyurethane tube the outside diameter being 126 mm, the thickness - 6.5 mm and the length 600 mm. Special attention was paid to study of elastic properties of foam-polyurethane tubes and to the effect of the chamber working fluid vapors on the tube sizes. It is stated that after a sustained load (3750 N for 6 days) the tube shrinks by 1.25 %. The foam-polyurethane supporting element arranged in 50% argon + 33% methane + 17% methylane mixture didn't change its sizes in the limit of 0.05% for three weeks. The chamber operates under self-qquenching streamer conditions

Tracking chamber made of 15-mm mylar drift tubes

Science.gov (United States)

Kozhin, A.; Borisov, A.; Bozhko, N.; Fakhrutdinov, R.; Plotnikov, I.

2017-05-01

We are presenting a drift chamber composed from three layers of mylar drift tubes with outer diameter 15 mm. The pipe is made of strip of mylar film 125 micrometers thick covered with aluminium from the both sides. A strip of mylar is wrapped around the mandrel. Pipe is created by ultrasonic welding. A single drift tube is self-supported structure withstanding 350 g wire tension without supports and internal overpressure. About 400 such tubes were assembled. Design, quality control procedures of the drift tubes are described. Seven chambers were glued from these tubes of 560 mm length. Each chamber consists of 3 layers, 16 tubes per layer. Several chambers were tested with cosmic rays. Results of the tests, counting rate plateau and coordinate resolution are presented.

Tracking chamber made of 15-mm mylar drift tubes

International Nuclear Information System (INIS)

Kozhin, A.; Borisov, A.; Bozhko, N.; Fakhrutdinov, R.; Plotnikov, I.

2017-01-01

We are presenting a drift chamber composed from three layers of mylar drift tubes with outer diameter 15 mm. The pipe is made of strip of mylar film 125 micrometers thick covered with aluminium from the both sides. A strip of mylar is wrapped around the mandrel. Pipe is created by ultrasonic welding. A single drift tube is self-supported structure withstanding 350 g wire tension without supports and internal overpressure. About 400 such tubes were assembled. Design, quality control procedures of the drift tubes are described. Seven chambers were glued from these tubes of 560 mm length. Each chamber consists of 3 layers, 16 tubes per layer. Several chambers were tested with cosmic rays. Results of the tests, counting rate plateau and coordinate resolution are presented.

The beam tube chamber of the CELLO Detector

International Nuclear Information System (INIS)

Sack, B.

1984-06-01

The beam tube chamber of the CELLO detector is since September 1982 in operation and works without problem. The main aim of this thesis was to determine using muons from the cosmic radiation the improvement in the momentum and vertex resolution by the beam tube chamber. Before this comparison could be performed the accurate position of the beam tube chamber had to be determined. After the performed position determination the spatial resolution amounts to 181 μm. The expected improvement factors could be reached completely both by cosmic radiation and by Bhabha events not studied in this thesis. The transverse momentum resolution amounts to the 1.18% x psub(T)(GeV/c). The vertex resolution is improved to 300 μm. Additionally by the beam tube chamber the time of an events can be measured with an occuracy of 5.7 ns. Finally is remains to be remarked that the beam tube chamber satisfies completely the requirements and represents a simple, but efficient supplement to the CELLO detector. [de

Tritons for the study of the charge-exchange reactions with the LHE streamer chamber: status and some possibilities

International Nuclear Information System (INIS)

Avramenko, S.A.; Belikov, Yu.A.; Golokhvastov, A.I.; Kirillov, A.D.; Khorozov, S.A.; Komolov, L.N.; Lukstin'sh, Yu.; Rukoyatkin, P.A.

1997-01-01

The 6 and 9 GeV/c secondary tritons, produced in the 4 He+A→ 3 H+X reaction, were used to study the charge-exchange reactions using a streamer chamber in magnetic field. The triton formation schemes, the beam parameters achieved as well as a way to reduce the beam momentum spread are given in the paper

Drift chambers on the basis of Mylar tube blocks

Science.gov (United States)

Budagov, Yu.; Chirikov-Zorin, I.; Golovanov, L.; Khazins, D.; Kuritsin, A.; Pukhov, O.; Zhukov, V.

1993-06-01

Prototypes of drift chambers constructed of Mylar tube blocks were tested. The purpose of developing tube blocks technology was to create long chambers (up to 3-4 m). Counting and drift characteristics of the chambers for different values of the gas pressure and different diameters of sense wires are presented. The lifetime of the chambers is determined. A photoeffect in the visible spectrum on the surface of the thin film aluminium cathode, which covers the Mylar tubes was observed.

Drift chambers on the basis of Mylar tube blocks

International Nuclear Information System (INIS)

Budagov, Yu.; Chirikov-Zorin, I.; Golovanov, L.; Khazins, D.; Kuritsin, A.; Pukhov, U.; Zhukov, V.

1993-01-01

Prototypes of drift chambers constructed of Mylar tube blocks were tested. The purpose of developing tube blocks technology was to create chambers (up to 3-4 m). Counting and drift chracteristics of the chambers for different values of the gas pressure and different diameters of sense wires are presented. The lifetime of the chambers is determined. A photoeffect in the visible spectrum on the surface of the thin film aluminium cathode, which covers the Mylar tubes was observed. (orig.)

Design and performance of a straw tube drift chamber

International Nuclear Information System (INIS)

Oh, S.H.; Wesson, D.K.; Cooke, J.; Goshaw, A.T.; Robertson, W.J.; Walker, W.D.

1991-01-01

The design and performance of the straw drift chambers used in E735 is reported. The chambers are constructed from 2.5 cm radius aluminized mylar straw tubes with wall thickness less than 0.2 mm. Also, presented are the results of tests with 2 mm radius straw tubes. The small tube has a direct detector application at the Superconducting Super Collider. (orig.)

Design and performance of a straw tube drift chamber

Science.gov (United States)

Oh, S. H.; Wesson, D. K.; Cooke, J.; Goshaw, A. T.; Robertson, W. J.; Walker, W. D.

1991-06-01

The design and performance of the straw drift chambers used in E735 is reported. The chambers are constructed from 2.5 cm radius aluminized mylar straw tubes with wall thickness less than 0.2 mm. Also, presented are the results of tests with 2 mm radius straw tubes. The small tube has a direct detector application at the Superconducting Super Collider.

Drift chambers on the basis of mylar tubing blocks

International Nuclear Information System (INIS)

Budagov, Yu.A.; Golovanov, L.B.; Kuritsin, A.A.; Pukhov, O.E.; Khazins, D.M.; Chirikov-Zorin, I.E.; Joint Inst. for Nuclear Research, Dubna; Zhukov, V.Yu.

1992-01-01

We tested the models of the drift chambers, which are constructed of mylar tubing blocks. The purpose of the tubing block forming technology is to create long chambers (up to 3-4 meters). There are count and drift characteristics of the chambers for different gas pressures and different diameters of sense wires. The service time of the chambers is defined. We registered a photoeffect in the visible spectrum area, which is displayed on the surface of the mylar film cathode, covered by aluminium. 8 refs.; 5 figs

The limited streamer tubes system for the SLD warm iron calorimeter

International Nuclear Information System (INIS)

Benvenuti, A.C.; Camanzi, B.; Piemontese, L.; Zucchelli, P.; Calcaterra, A.; De Sangro, R.; De Simone, P.; De Simone, S.; Gallinaro, M.; Peruzzi, I.; Piccolo, M.; Bacchetta, N.; Bisello, D.; Castro, A.; Galvagni, S.; Loreti, M.; Pescara, L.; Wyss, J.; Battiston, R.; Biasini, M.; Bilei, G.M.; Checcucci, B; Mancinelli, G.; Mantovani, G.; Pauluzzi, M.; Santocchia, A.; Servoli, L.; Carpinelli, M.; Castaldi, R.; Cazzola, U.; Dell'Orso, R.; Pieroni, E.; Vannini, C.; Verdini, P.G.; Byers, B.L.; Escalera, J.; Kharakh, D.; Messner, R.L.; Zdarko, R.W.; Johnson, J.R.

1992-01-01

The SLD detector at the Stanford Linear Accelerator Center is a general purpose device for studying e + ε - interaction at the Z 0 . The SLD calorimeter system consists of two parts: a lead Liquid Argon Calorimeter (LAC) with both electromagnetic (22 radiation lengths) and hadronic sections (2.8 absorption lengths) housed inside the coil, and the Warm Ion limited streamer tubes Calorimeter (WIC) outside the coil which uses as radiator the iron of the flux return for the magnetic field. The WIC completes the measurement of the hadronic shower energy (∼85% on average is contained in the LAC) and it provides identification and tracking for muons over 99% of the solid angle. In this note we report on the construction, test and commissioning of such a large system

Design and operation of large straw-tube drift chamber planes

Energy Technology Data Exchange (ETDEWEB)

Bromberg, C; Brown, D; Huston, J; Maul, A; Miller, R; Nyugen, A; Sorrell, L; Yosef, C [Physics and Astronomy Dept., Michigan State Univ., East Lansing, MI (United States); Mani, S [Physics Dept., Univ. of California, Davis, CA (United States); Choudhary, B C; Kapoor, V; Shivpuri, R [Dept. of Physics and Astrophysics, Delhi Univ. (India); Baker, W; DeSoi, W; Johnstone, C; Kourbanis, I; Lukens, P; Skow, D; Wu, G H [Fermilab, Batavia, IL (United States); Alverson, G; Chang, P; Dlugosz, W; Faissler, W; Garelick, D; Glaubman, M; Lirakis, C; Pothier, E; Yasuda, T [Dept. of Physics, Northeastern Univ., Boston, MA (United States); Gutierrez, P [Dept. of Physics and Astronomy, Univ. of Oklahoma, Norman, OK (United States); Hartman, K; Oh, B Y; Toothacker, W; Whitmore, J [Dept. of Physics, Pennsylvania State Univ., University Park, PA (United States); Blusk, S R; Chung, W H; Engels, E Jr; Shepard, P F; Weerasundara, D D.S. [Dept. of Physics and

1991-10-01

We describe the design, construction and operation of a straw-tube drift chamber consisting of four X and four Y planes of 16 mm diameter straw-tubes, each 280 cm long. Straws were glued together for rigidity and were mounted into a frame which served as a gas manifold and maintained wire-to-wire precision. A novel conductive gasket was used to seal the tubes and provide electrical contact to the aluminized surface of the straws. The chamber has been successfully used in a high rate experiment (E706 at Fermilab) and has achieved its design resolution of better than 250 {mu}m per tube averaged over the whole chamber. (orig.).

Study of Interaction of Low-Energy Antiprotons with H$^{2}$,He$^{3}$,He$^{4}$,Ne-Nuclei Using a Streamer Chamber in Magnetic Field

CERN Multimedia

2002-01-01

The aim of this experiment is the systematic study of the interaction between low-energy antiprotons and the H|2,~He|3,~He|4,~Ne-nuclei using a self shunted streamer chamber in a magnetic field exposed to the antiproton beam of the LEAR facility. The properties of the self shunted streamer chamber, which allows the use of the filling gas (hydrogen, helium, neon at a pressure of l~atm) as a target, permit to carry out experiments also in the very low-energy region. \\\\ \\\\ The experimental apparatus is suitable for a large programme of measurements. We plan to measure the @*H|2 cross section and the spectator momentum distributions at @* momenta lower than 250~MeV/c, where data are lacking. It is interesting to study for the first time the @*He|3 and @*He|4 interactions measuring the cross sections and the emitted particle distributions. Among other things the knowledge of the branching ratio of the @*He|4 annihilation channels clarifies some open cosmological questions. The study of the process of nuclear absor...

Performance of the MACRO limited streamer tubes for estimates of muon energy

CERN Document Server

Giorgini, M

2002-01-01

The MACRO limited streamer tubes can be operated in drift mode by using the TDCs included in the QTP system. In this way a considerable improvement in the space resolution is obtained, allowing the analysis of muon tracks in terms of multiple scattering effects and the energy estimates of muons crossing the detector. We present the results of two dedicated tests, performed with the CERN PS-T9 and SPS-X7 beams, to provide a full check of the electronics and to exploit the feasibility of the analysis. Using a neural network, we are able to estimate the muon energies up to E/sub mu / approximately = 40 GeV. The test beam data provide then an absolute energy calibration, which allows to apply the method to the MACRO data. (5 refs).

Effect of flame-tube head structure on combustion chamber performance

Science.gov (United States)

Gu, Minqqi

1986-01-01

The experimental combustion performance of a premixed, pilot-type flame tube with various head structures is discussed. The test study covers an extensive area: efficiency of the combustion chamber, quality of the outlet temperature field, limit of the fuel-lean blowout, ignition performance at ground starting, and carbon deposition. As a result of these tests, a nozzle was found which fits the premixed pilot flame tube well. The use of this nozzle optimized the performance of the combustion chamber. The tested models had premixed pilot chambers with two types of air-film-cooling structures, six types of venturi-tube structures, and secondary fuel nozzles with two small spray-cone angles.

Track reconstruction method in a small volume self-shunted streamer chamber - analysis of the errors for low energy electrons

International Nuclear Information System (INIS)

Parizet, M.J.; Augerat, J.; Avan, M.; Ballet, M.; Vialle, M.

1977-01-01

A programme has been worked out to reconstruct electron tracks of low energy (from 100 keV to 2 MeV) curved by a magnetic field in a small streamer chamber (size 10x11x51 cm 3 ). Before a study of the problems involved in the experimental set-up, the geometrical programme is described and the different errors are evaluated. Finally the accuracies on kinetic energies and angles which can be obtained for low energy elctron tracks are given. (Auth.)

Track chambers based on precision drift tubes housed inside 30 mm mylar pipe

International Nuclear Information System (INIS)

Borisov, A; Bozhko, N; Fakhrutdinov, R; Kozhin, A; Leontiev, B; Levin, A

2014-01-01

We describe drift chambers consisting of 3 layers of 30 mm (OD) drift tubes made of double sided aluminized mylar film with thickness 0.125 mm. A single drift tube is self-supported structure withstanding 350 g tension of 50 microns sense wire located in the tube center with 10 microns precision with respect to end-plug outer surface. Such tubes allow to create drift chambers with small amount of material, construction of such chambers doesn't require hard frames. Twenty six chambers with working area from 0.8 × 1.0 to 2.5 × 2.0 m 2 including 4440 tubes have been manufactured for experiments at 70-GeV proton accelerator at IHEP(Protvino)

Track chambers based on precision drift tubes housed inside 30 mm mylar pipe

Science.gov (United States)

Borisov, A.; Bozhko, N.; Fakhrutdinov, R.; Kozhin, A.; Leontiev, B.; Levin, A.

2014-06-01

We describe drift chambers consisting of 3 layers of 30 mm (OD) drift tubes made of double sided aluminized mylar film with thickness 0.125 mm. A single drift tube is self-supported structure withstanding 350 g tension of 50 microns sense wire located in the tube center with 10 microns precision with respect to end-plug outer surface. Such tubes allow to create drift chambers with small amount of material, construction of such chambers doesn't require hard frames. Twenty six chambers with working area from 0.8 × 1.0 to 2.5 × 2.0 m2 including 4440 tubes have been manufactured for experiments at 70-GeV proton accelerator at IHEP(Protvino).

Development and performance of resistive seamless straw-tube gas chambers

International Nuclear Information System (INIS)

Takubo, Y.; Aoki, M.; Ishihara, A.; Ishii, J.; Kuno, Y.; Maeda, F.; Nakahara, K.; Nosaka, N.; Sakamoto, H.; Sato, A.; Terai, K.; Igarashi, Y.; Yokoi, T.

2005-01-01

A new straw-tube gas chamber which is made of seamless straw-tubes, instead of ordinary wound-type straw-tubes is developed. Seamless straw-tubes have various advantages over ordinary wound-type ones, in particular, in terms of mechanical strength and lesser wall thickness. Our seamless straw-tubes are fabricated to be resistive so that the hit positions along the straw axis can be read by cathode planes placed outside the straw-tube chambers, where the cathode strips run transverse to the straw axis. A beam test was carried out at KEK to study their performance. As a result of the beam test, the position resolution of the cathode strips of 220μm is achieved, and an anode position resolution of 112μm is also obtained

Wire- and cathode pulses in a counter of square cross section with a thin wire as central conductor operating in limited streamer mode

Science.gov (United States)

Carli, Ch.; Erd, Ch.; Leder, G.; Pernicka, M.; Regler, M.; Schnizer, B.

1989-11-01

Streamer tubes are becoming increasingly important in high-energy physics experiments. They are used as drift tubes for the localisation of charged-particle tracks, and also as sampling devices in sandwich calorimeters with cathode readout only. The streamer pulses carry charges which are several orders of magnitude larger than pulses from proportional chambers; this provides a good signal-to-noise ratio and makes them appropriate for a wide field of applications in highly compact detectors. The signals induced on the cathodes are also important for measuring — in addition to the anode wire - a second coordinate, and for resolving ambiguities in track recognition. When connecting the signals from two opposite cathodes to the two inputs of a differential amplifier, a left/right bit could be added after suitable buffering via the same signal line as used for time digitalisation. Another essential feature is the association of time information from the anode wire and the cathode. For the streamer tube used in this experiment the pulses induced on the cathode on either side of the particle, and on the anode, are measured by a fast analog-to-digital converter. A simple two-dimensional model ρ( r, θ) at t = 0, without any time-dependent effects other than a constant electron drift velocity of 50 μm/ns, is used to compare the charge distribution in a streamer with the measurements of the pulse lengths at the two opposite cathode strips. First the field generated by a static voltage is calculated. Then the effect of a "space charge" is evaluated. The Green's function of the square domain is a prerequisite for determining the field and the surface charge distribution on the electrodes. It is obtained from that of a concentric circular counter by a conformal mapping. Representations of Green's functions are calculated by series expansions.

Shock tubes: compressions in the low pressure chamber

International Nuclear Information System (INIS)

Schins, H.; Giuliani, S.

1986-01-01

The gas shock tube used in these experiments consists of a low pressure chamber and a high pressure chamber, divided by a metal-diaphragm-to-rupture. In contrast to the shock mode of operation, where incident and reflected shocks in the low pressure chamber are studied which occur within 3.5 ms, in this work the compression mode of operation was studied, whose maxima occur (in the low pressure chamber) about 9 ms after rupture. Theoretical analysis was done with the finite element computer code EURDYN-1M, where the computation was carried out to 30 ms

Construction and Test of New Precision Drift-Tube Chambers for the ATLAS Muon Spectrometer

CERN Document Server

INSPIRE-00218480

2017-02-11

ATLAS muon detector upgrades aim for increased acceptance for muon triggering and precision tracking and for improved rate capability of the muon chambers in the high-background regions of the detector with increasing LHC luminosity. The small-diameter Muon Drift Tube (sMDT) chambers have been developed for these purposes. With half of the drift-tube diameter of the MDT chambers and otherwise unchanged operating parameters, sMDT chambers share the advantages of the MDTs, but have an order of magnitude higher rate capability and can be installed in detector regions where MDT chambers do not fit in. The chamber assembly methods have been optimized for mass production, minimizing construction time and personnel. Sense wire positioning accuracies of 5 ?micons have been achieved in serial production for large-size chambers comprising several hundred drift tubes. The construction of new sMDT chambers for installation in the 2016/17 winter shutdown of the LHC and the design of sMDT chambers in combination with new R...

Researching the Performance of Dual-Chamber Fire-Tube Boiler Furnace

Directory of Open Access Journals (Sweden)

Khaustov Sergei

2015-01-01

Full Text Available Autonomous heating systems equipped with fire-tube or shell boilers show high effectiveness, consistent performance and great technical parameters. But there is a significant limitation of its thermal productivity due to the complexity of durable large diameter fire-tube bottoms implementation. Optimization of combustion aerodynamics can be the way to expand the fire-tube boilers performance limit. In this case lots of problems connected with reducing emissions of toxic substances, providing of burning stability, local heat stresses and aerodynamic resistances should be solved. To resolve the indicated problems, a modified model of dual-chamber fire-tube boiler furnace is proposed. The performance of suggested flame-tube was simulated using the proven computer-aided engineering software ANSYS Multiphysics. Results display proposed flame tube completely filled with moving medium without stagnant zones. Turbulent vortical combustion is observed even with the straight-through fuel supply. Active flue gas recirculation in suggested dual-chamber furnace reduces emissions of pollutants. Diminution of wall heat fluxes allows boiler operation at lower water treatment costs.

Construction and test of high precision drift-tube (sMDT) chambers for the ATLAS muon spectrometer

CERN Document Server

Nowak, Sebastian; Kroha, Hubert; Schwegler, Philipp; Sforza, Federico

2014-01-01

For the upgrade of the ATLAS muon spectrometer in March 2014 new muon tracking chambers (sMDT) with drift-tubes of 15 mm diameter, half of the value of the standard ATLAS Monitored Drift-Tubes (MDT) chambers, and 10~$\\mu$m positioning accuracy of the sense wires have been constructed. The new chambers are designed to be fully compatible with the present ATLAS services but, with respect to the previously installed ATLAS MDT chambers, they are assembled in a more compact geometry and they deploy two additional tube layers that provide redundant rack information. The chambers are composed of 8 layers of in total 624 aluminium drift-tubes. The assembly of a chamber is completed within a week. A semi-automatized production line is used for the assembly of the drift-tubes prior to the chamber assembly. The production procedures and the quality control tests of the single components and of the complete chambers will be discussed. The wire position in the completed chambers have been measured by using a coordinate me...

Application of CA and NN for event recognition in experiments DISTO and STREAMER

International Nuclear Information System (INIS)

Bussa, M.P.; Ivanov, V.V.; Kisel, I.V.; Pontecorvo, G.B.

1997-01-01

An algorithm for charged particle recognition and event identification applying a cellular automaton (CA) model and a multi-layer neural network (NN) has been developed for the DISTO experiment under way at Saturne (Saclay, France). A further development of the model will be applied for particle recognition in the Dubna Streamer Chamber Spectrometer (DSCS) for studying pion-nucleus absorption (experiments DISTO and STREAMER). (orig.)

Construction and test of new precision drift-tube chambers for the ATLAS muon spectrometer

Energy Technology Data Exchange (ETDEWEB)

Kroha, H., E-mail: kroha@mpp.mpg.de; Kortner, O.; Schmidt-Sommerfeld, K.; Takasugi, E.

2017-02-11

ATLAS muon detector upgrades aim for increased acceptance for muon triggering and precision tracking and for improved rate capability of the muon chambers in the high-background regions of the detector with increasing LHC luminosity. The small-diameter Muon Drift Tube (sMDT) chambers have been developed for these purposes. With half of the drift-tube diameter of the MDT chambers and otherwise unchanged operating parameters, sMDT chambers share the advantages of the MDTs, but have an order of magnitude higher rate capability and can be installed in detector regions where MDT chambers do not fit in. The chamber assembly methods have been optimized for mass production, minimizing construction time and personnel. Sense wire positioning accuracies of 5 μm have been achieved in serial production for large-size chambers comprising several hundred drift tubes. The construction of new sMDT chambers for installation in the 2016/17 winter shutdown of the LHC and the design of sMDT chambers in combination with new RPC trigger chambers for replacement of the inner layer of the barrel muon spectrometer are in progress.

Construction and test of new precision drift-tube chambers for the ATLAS muon spectrometer

Science.gov (United States)

Kroha, H.; Kortner, O.; Schmidt-Sommerfeld, K.; Takasugi, E.

2017-02-01

ATLAS muon detector upgrades aim for increased acceptance for muon triggering and precision tracking and for improved rate capability of the muon chambers in the high-background regions of the detector with increasing LHC luminosity. The small-diameter Muon Drift Tube (sMDT) chambers have been developed for these purposes. With half of the drift-tube diameter of the MDT chambers and otherwise unchanged operating parameters, sMDT chambers share the advantages of the MDTs, but have an order of magnitude higher rate capability and can be installed in detector regions where MDT chambers do not fit in. The chamber assembly methods have been optimized for mass production, minimizing construction time and personnel. Sense wire positioning accuracies of 5 μm have been achieved in serial production for large-size chambers comprising several hundred drift tubes. The construction of new sMDT chambers for installation in the 2016/17 winter shutdown of the LHC and the design of sMDT chambers in combination with new RPC trigger chambers for replacement of the inner layer of the barrel muon spectrometer are in progress.

A drift chamber constructed of aluminized mylar tubes

Science.gov (United States)

Baringer, P.; Jung, C.; Ogren, H. O.; Rust, D. R.

1987-03-01

A thin reliable drift chamber has been constructed to be used near the interaction point of the PEP storage ring in the HRS detector. It is composed of individual drift tubes with aluminized mylar walls.

A drift chamber constructed of aluminized mylar tubes

International Nuclear Information System (INIS)

Baringer, P.; Jung, C.; Ogren, H.O.; Rust, D.R.

1987-01-01

A thin reliable drift chamber has been constructed to be used near the interaction point of the PEP storage ring in the HRS detector. It is composed of individual drift tubes with aluminized mylar walls. (orig.)

Electronics for the CMS muon drift tube chambers the read-out minicrate

CERN Document Server

Fernandez Bedoya, Cristina; Oller, Juan Carlos; Willmott, Carlos

2005-01-01

On the Compact Muon Solenoid (CMS) experimentat the Large Hadron Collider (LHC) at the CERN laboratory, the drift tube chambers are responsible for muon detection and precise momentum measurement. In this paper the first level of the read out electronics for these drift tube chambers is described. These drift tube chambers will be located inside the muon barrel detector in the so-called minicrates (MCs), attached to the chambers. The read out boards (ROBs) are the main component of this first level data acquisition system, and they are responsible for the time digitalization related to Level 1 Accept (L1A) trigger of the incoming signals from the front-end electronics, followed by a consequent data merging to the next stages of the data acquisition system. ROBs' architecture and functionality have been exhaustively tested, as well as their capability of operation beyond the expected environmental conditions inside the CMS detector. Due to the satisfactory results obtained, final production of ROBs and their a...

Method of detection of transition radiation by wire chambers operating in self-quenching streamer mode

International Nuclear Information System (INIS)

Akopdzhanov, G.A.; Bityukov, S.I.; Dzhelyadin, R.I.; Zaitsev, A.M.; Lapin, V.V.; Saraikin, A.I.

1984-01-01

A method for detecting X-ray transition radiation against the background of the signal from relativistic charged particles is suggested that is based on the use of peculiarities of the development of self-queenching streamer mode. The self-qunching streamer discharge in the Xe + isobutane mixture is experimentally registered. The effect of separation of signals from the relativistic particle and from soft X-ray, is obtained

Assembly of Drift Tubes (DT) Chambers at CIEMAT (Madrid)

CERN Multimedia

Jesus Puerta-Pelayo

2003-01-01

The construction of muon drift tube chambers (DT) has been carried out in four different european institutes: Aachen (Germany), CIEMAT-Madrid (Spain), Legnaro and Turin (Italy), all of them following similar procedures and quality tests. Each chamber is composed by three or two independent units called superlayers, with four layers of staggered drift cells each. The assembly of a superlayer is a succesive glueing of aluminium plates and I-beams with electrodes previously attached, forming a rectangular and gas-tight volume. These pictures illustrate the various processes of material preparation, construction, equipment and assembly of full chambers at CIEMAT (Madrid).

Charge division in a small proportional chamber constructed with aluminized mylar tubes

International Nuclear Information System (INIS)

Biino, C.; Mussa, R.; Palestini, S.; Pastrone, N.; Pesando, L.

1988-01-01

A tracking detector composed of aluminized mylar drift tubes is under development for the Fermilab experiment 760. A prototype chamber has been constructed. Results on the longitudinal coordinate determined by charge division are given. Spatial resolution values below 2 mm (rms) were found, corresponding to <1% of the chamber length. Results on chamber ageing are also discussed. (orig.)

Charge division in a small proportional chamber constructed with aluminized mylar tubes

Science.gov (United States)

Biino, C.; Mussa, R.; Palestini, S.; Pastrone, N.; Pesando, L.

1988-09-01

A tracking detector composed of aluminized mylar drift tubes is under development for the Fermilab experiment 760. A prototype chamber has been constructed. Results on the longitudinal coordinate determined by charge division are given. Spatial resolution values below 2 mm (rms) were found, corresponding to <1% of the chamber length. Results on chamber ageing are also discussed.

Test beam analysis of the first CMS drift tube muon chamber

CERN Document Server

Albajar, C; Arce, P; Autermann, C; Bellato, M; Benettoni, M; Benvenuti, Alberto C; Bontenackels, M; Caballero, J; Cavallo, F R; Cerrada, M; Cirio, R; Colino, N; Conti, E; de la Cruz, B; Dal Corso, F; Dallavalle, G M; Fernández, C; Fernández de Troconiz, J; Fouz-Iglesias, M C; García-Abia, P; García-Raboso, A; Gasparini, F; Gasparini, U; Giacomelli, P; Gonella, F; Gulmini, M; Hebbeker, T; Hermann, S; Höpfner, K; Jiménez, I; Josa-Mutuberria, I; Lacaprara, S; Marcellini, S; Mariotti, C; Maron, G; Maselli, S; Meneguzzo, Anna Teresa; Monaco, V; Montanari, A; Montanari, C; Montecassiano, F; Navarria, Francesco Luigi; Odorici, F; Passaseo, M; Pegoraro, M; Peroni, C; Perrotta, A; Puerta, J; Reithler, H; Romero, A; Romero, L; Ronchese, P; Rossi, A; Rovelli, T; Sacchi, R; Sowa, M; Staiano, A; Toniolo, N; Torassa, E; Vaniev, V; Vanini, S; Ventura, Sandro; Villanueva, C; Willmott, C; Zotto, P L; Zumerle, G

2004-01-01

In October 2001 the first produced CMS Barrel Drift Tube (DT) Muon Chamber was tested at the CERN Gamma Irradiation Facility (GIF) using a muon beam. A Resistive Plate Chamber (RPC) was attached to the top of the DT chamber, and, for the first time, both detectors were operated coupled together. The performance of the DT chamber was studied for several operating conditions, and for gamma rates similar to the ones expected at LHC. In this paper we present the data analysis; the results are considered fully satisfactory.

Test beam analysis of the first CMS drift tube muon chamber

International Nuclear Information System (INIS)

Albajar, C.; Amapane, N.; Arce, P.; Autermann, C.; Bellato, M.; Benettoni, M.; Benvenuti, A.; Bontenackels, M.; Caballero, J.; Cavallo, F.R.; Cerrada, M.; Cirio, R.; Colino, N.; Conti, E.; Cruz, B. de la; Corso, F. dal; Dallavalle, G.M.; Fernandez, C.; Troconiz, J.F. de; Fouz, M.C.; Garcia-Abia, P.; Garcia-Raboso, A.; Gasparini, F.; Gasparini, U.; Giacomelli, P.; Gonella, F.; Gulmini, M.; Hebbeker, T.; Hermann, S.; Hoepfner, K.; Jimenez, I.; Josa, I.; Lacaprara, S.; Marcellini, S.; Mariotti, C.; Maron, G.; Maselli, S.; Meneguzzo, A.T.; Monaco, V.; Montanari, A.; Montanari, C.; Montecassiano, F.; Navarria, F.L.; Odorici, F.; Passaseo, M.; Pegoraro, M.; Peroni, C.; Perrotta, A.; Puerta, J.; Reithler, H.; Romero, A.; Romero, L.; Ronchese, P.; Rossi, A.; Rovelli, T.; Sacchi, R.; Sowa, M.; Staiano, A.; Toniolo, N.; Torassa, E.; Vaniev, V.; Vanini, S.; Ventura, S.; Villanueva, C.; Willmott, C.; Zotto, P.; Zumerle, G.

2004-01-01

In October 2001 the first produced CMS Barrel Drift Tube (DT) Muon Chamber was tested at the CERN Gamma Irradiation Facility (GIF) using a muon beam. A Resistive Plate Chamber (RPC) was attached to the top of the DT chamber, and, for the first time, both detectors were operated coupled together. The performance of the DT chamber was studied for several operating conditions, and for gamma rates similar to the ones expected at LHC. In this paper we present the data analysis; the results are considered fully satisfactory

Test beam analysis of the first CMS drift tube muon chamber

Energy Technology Data Exchange (ETDEWEB)

Albajar, C.; Amapane, N.; Arce, P.; Autermann, C.; Bellato, M.; Benettoni, M.; Benvenuti, A.; Bontenackels, M.; Caballero, J.; Cavallo, F.R.; Cerrada, M.; Cirio, R.; Colino, N.; Conti, E.; Cruz, B. de la; Corso, F. dal; Dallavalle, G.M.; Fernandez, C.; Troconiz, J.F. de E-mail: jorge.troconiz@uam.es; Fouz, M.C.; Garcia-Abia, P.; Garcia-Raboso, A.; Gasparini, F.; Gasparini, U.; Giacomelli, P.; Gonella, F.; Gulmini, M.; Hebbeker, T.; Hermann, S.; Hoepfner, K.; Jimenez, I.; Josa, I.; Lacaprara, S.; Marcellini, S.; Mariotti, C.; Maron, G.; Maselli, S.; Meneguzzo, A.T.; Monaco, V.; Montanari, A.; Montanari, C.; Montecassiano, F.; Navarria, F.L.; Odorici, F.; Passaseo, M.; Pegoraro, M.; Peroni, C.; Perrotta, A.; Puerta, J.; Reithler, H.; Romero, A.; Romero, L.; Ronchese, P.; Rossi, A.; Rovelli, T.; Sacchi, R.; Sowa, M.; Staiano, A.; Toniolo, N.; Torassa, E.; Vaniev, V.; Vanini, S.; Ventura, S.; Villanueva, C.; Willmott, C.; Zotto, P.; Zumerle, G

2004-06-11

In October 2001 the first produced CMS Barrel Drift Tube (DT) Muon Chamber was tested at the CERN Gamma Irradiation Facility (GIF) using a muon beam. A Resistive Plate Chamber (RPC) was attached to the top of the DT chamber, and, for the first time, both detectors were operated coupled together. The performance of the DT chamber was studied for several operating conditions, and for gamma rates similar to the ones expected at LHC. In this paper we present the data analysis; the results are considered fully satisfactory.

Performance of the CMS Drift Tube Chambers with Cosmic Rays

CERN Document Server

Chatrchyan, S; Sirunyan, A M; Adam, W; Arnold, B; Bergauer, H; Bergauer, T; Dragicevic, M; Eichberger, M; Erö, J; Friedl, M; Frühwirth, R; Ghete, V M; Hammer, J; Hänsel, S; Hoch, M; Hörmann, N; Hrubec, J; Jeitler, M; Kasieczka, G; Kastner, K; Krammer, M; Liko, D; Magrans de Abril, I; Mikulec, I; Mittermayr, F; Neuherz, B; Oberegger, M; Padrta, M; Pernicka, M; Rohringer, H; Schmid, S; Schöfbeck, R; Schreiner, T; Stark, R; Steininger, H; Strauss, J; Taurok, A; Teischinger, F; Themel, T; Uhl, D; Wagner, P; Waltenberger, W; Walzel, G; Widl, E; Wulz, C E; Chekhovsky, V; Dvornikov, O; Emeliantchik, I; Litomin, A; Makarenko, V; Marfin, I; Mossolov, V; Shumeiko, N; Solin, A; Stefanovitch, R; Suarez Gonzalez, J; Tikhonov, A; Fedorov, A; Karneyeu, A; Korzhik, M; Panov, V; Zuyeuski, R; Kuchinsky, P; Beaumont, W; Benucci, L; Cardaci, M; De Wolf, E A; Delmeire, E; Druzhkin, D; Hashemi, M; Janssen, X; Maes, T; Mucibello, L; Ochesanu, S; Rougny, R; Selvaggi, M; Van Haevermaet, H; Van Mechelen, P; Van Remortel, N; Adler, V; Beauceron, S; Blyweert, S; D'Hondt, J; De Weirdt, S; Devroede, O; Heyninck, J; Kalogeropoulos, A; Maes, J; Maes, M; Mozer, M U; Tavernier, S; Van Doninck, W; Van Mulders, P; Villella, I; Bouhali, O; Chabert, E C; Charaf, O; Clerbaux, B; De Lentdecker, G; Dero, V; Elgammal, S; Gay, A P R; Hammad, G H; Marage, P E; Rugovac, S; Vander Velde, C; Vanlaer, P; Wickens, J; Grunewald, M; Klein, B; Marinov, A; Ryckbosch, D; Thyssen, F; Tytgat, M; Vanelderen, L; Verwilligen, P; Basegmez, S; Bruno, G; Caudron, J; Delaere, C; Demin, P; Favart, D; Giammanco, A; Grégoire, G; Lemaitre, V; Militaru, O; Ovyn, S; Piotrzkowski, K; Quertenmont, L; Schul, N; Beliy, N; Daubie, E; Alves, G A; Pol, M E; Souza, M H G; Carvalho, W; De Jesus Damiao, D; De Oliveira Martins, C; Fonseca De Souza, S; Mundim, L; Oguri, V; Santoro, A; Silva Do Amaral, S M; Sznajder, A; Fernandez Perez Tomei, T R; Ferreira Dias, M A; Gregores, E M; Novaes, S F; Abadjiev, K; Anguelov, T; Damgov, J; Darmenov, N; Dimitrov, L; Genchev, V; Iaydjiev, P; Piperov, S; Stoykova, S; Sultanov, G; Trayanov, R; Vankov, I; Dimitrov, A; Dyulendarova, M; Kozhuharov, V; Litov, L; Marinova, E; Mateev, M; Pavlov, B; Petkov, P; Toteva, Z; Chen, G M; Chen, H S; Guan, W; Jiang, C H; Liang, D; Liu, B; Meng, X; Tao, J; Wang, J; Wang, Z; Xue, Z; Zhang, Z; Ban, Y; Cai, J; Ge, Y; Guo, S; Hu, Z; Mao, Y; Qian, S J; Teng, H; Zhu, B; Avila, C; Baquero Ruiz, M; Carrillo Montoya, C A; Gomez, A; Gomez Moreno, B; Ocampo Rios, A A; Osorio Oliveros, A F; Reyes Romero, D; Sanabria, J C; Godinovic, N; Lelas, K; Plestina, R; Polic, D; Puljak, I; Antunovic, Z; Dzelalija, M; Brigljevic, V; Duric, S; Kadija, K; Morovic, S; Fereos, R; Galanti, M; Mousa, J; Papadakis, A; Ptochos, F; Razis, P A; Tsiakkouri, D; Zinonos, Z; Hektor, A; Kadastik, M; Kannike, K; Müntel, M; Raidal, M; Rebane, L; Anttila, E; Czellar, S; Härkönen, J; Heikkinen, A; Karimäki, V; Kinnunen, R; Klem, J; Kortelainen, M J; Lampén, T; Lassila-Perini, K; Lehti, S; Lindén, T; Luukka, P; Mäenpää, T; 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Nardulli, A; Nessi-Tedaldi, F; Pape, L; Pauss, F; Punz, T; Rizzi, A; Ronga, F J; Sala, L; Sanchez, A K; Sawley, M C; Sordini, V; Stieger, B; Tauscher, L; Thea, A; Theofilatos, K; Treille, D; Trüb, P; Weber, M; Wehrli, L; Weng, J; Zelepoukine, S; Amsler, C; Chiochia, V; De Visscher, S; Regenfus, C; Robmann, P; Rommerskirchen, T; Schmidt, A; Tsirigkas, D; Wilke, L; Chang, Y H; Chen, E A; Chen, W T; Go, A; Kuo, C M; Li, S W; Lin, W; Bartalini, P; Chang, P; Chao, Y; Chen, K F; Hou, W S; Hsiung, Y; Lei, Y J; Lin, S W; Lu, R S; Schümann, J; Shiu, J G; Tzeng, Y M; Ueno, K; Velikzhanin, Y; Wang, C C; Wang, M; Adiguzel, A; Ayhan, A; Azman Gokce, A; Bakirci, M N; Cerci, S; Dumanoglu, I; Eskut, E; Girgis, S; Gurpinar, E; Hos, I; Karaman, T; Kayis Topaksu, A; Kurt, P; Önengüt, G; Önengüt Gökbulut, G; Ozdemir, K; Ozturk, S; Polatöz, A; Sogut, K; Tali, B; Topakli, H; Uzun, D; Vergili, L N; Vergili, M; Akin, I V; Aliev, T; Bilmis, S; Deniz, M; Gamsizkan, H; Guler, A M; Öcalan, K; Serin, M; Sever, R; 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Elias, J E; Elvira, V D; Evans, D; Feng, L; Fischler, M; Fisk, I; Foulkes, S; Freeman, J; Gartung, P; Gottschalk, E; Grassi, T; Green, D; Guo, Y; Gutsche, O; Hahn, A; Hanlon, J; Harris, R M; Holzman, B; Howell, J; Hufnagel, D; James, E; Jensen, H; Johnson, M; Jones, C D; Joshi, U; Juska, E; Kaiser, J; Klima, B; Kossiakov, S; Kousouris, K; Kwan, S; Lei, C M; Limon, P; Lopez Perez, J A; Los, S; Lueking, L; Lukhanin, G; Lusin, S; Lykken, J; Maeshima, K; Marraffino, J M; Mason, D; McBride, P; Miao, T; Mishra, K; Moccia, S; Mommsen, R; Mrenna, S; Muhammad, A S; Newman-Holmes, C; Noeding, C; O'Dell, V; Prokofyev, O; Rivera, R; Rivetta, C H; Ronzhin, A; Rossman, P; Ryu, S; Sekhri, V; Sexton-Kennedy, E; Sfiligoi, I; Sharma, S; Shaw, T M; Shpakov, D; Skup, E; Smith, R P; Soha, A; Spalding, W J; Spiegel, L; Suzuki, I; Tan, P; Tanenbaum, W; Tkaczyk, S; Trentadue, R; Uplegger, L; Vaandering, E W; Vidal, R; Whitmore, J; Wicklund, E; Wu, W; Yarba, J; Yumiceva, F; Yun, J C; Acosta, D; Avery, P; Barashko, V; Bourilkov, D; Chen, M; Di Giovanni, G P; Dobur, D; Drozdetskiy, A; Field, R D; Fu, Y; Furic, I K; Gartner, J; Holmes, D; Kim, B; Klimenko, S; Konigsberg, J; Korytov, A; Kotov, K; Kropivnitskaya, A; Kypreos, T; Madorsky, A; Matchev, K; Mitselmakher, G; Pakhotin, Y; Piedra Gomez, J; Prescott, C; Rapsevicius, V; Remington, R; Schmitt, M; Scurlock, B; Wang, D; Yelton, J; Ceron, C; Gaultney, V; Kramer, L; Lebolo, L M; Linn, S; Markowitz, P; Martinez, G; Rodriguez, J L; Adams, T; Askew, A; Baer, H; Bertoldi, M; Chen, J; Dharmaratna, W G D; Gleyzer, S V; Haas, J; Hagopian, S; Hagopian, V; Jenkins, M; Johnson, K F; Prettner, E; Prosper, H; Sekmen, S; Baarmand, M M; Guragain, S; Hohlmann, M; Kalakhety, H; Mermerkaya, H; Ralich, R; Vodopiyanov, I; Abelev, B; Adams, M R; Anghel, I M; Apanasevich, L; Bazterra, V E; Betts, R R; Callner, J; Castro, M A; Cavanaugh, R; Dragoiu, C; Garcia-Solis, E J; Gerber, C E; Hofman, D J; Khalatian, S; Mironov, C; Shabalina, E; Smoron, A; Varelas, N; Akgun, U; Albayrak, E A; 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Gomez Ceballos, G; Hahn, K A; Harris, P; Jaditz, S; Kim, Y; Klute, M; Lee, Y J; Li, W; Loizides, C; Ma, T; Miller, M; Nahn, S; Paus, C; Roland, C; Roland, G; Rudolph, M; Stephans, G; Sumorok, K; Sung, K; Vaurynovich, S; Wenger, E A; Wyslouch, B; Xie, S; Yilmaz, Y; Yoon, A S; Bailleux, D; Cooper, S I; Cushman, P; Dahmes, B; De Benedetti, A; Dolgopolov, A; Dudero, P R; Egeland, R; Franzoni, G; Haupt, J; Inyakin, A; Klapoetke, K; Kubota, Y; Mans, J; Mirman, N; Petyt, D; Rekovic, V; Rusack, R; Schroeder, M; Singovsky, A; Zhang, J; Cremaldi, L M; Godang, R; Kroeger, R; Perera, L; Rahmat, R; Sanders, D A; Sonnek, P; Summers, D; Bloom, K; Bockelman, B; Bose, S; Butt, J; Claes, D R; Dominguez, A; Eads, M; Keller, J; Kelly, T; Kravchenko, I; Lazo-Flores, J; Lundstedt, C; Malbouisson, H; Malik, S; Snow, G R; Baur, U; Iashvili, I; Kharchilava, A; Kumar, A; Smith, K; Strang, M; Alverson, G; Barberis, E; Boeriu, O; Eulisse, G; Govi, G; McCauley, T; Musienko, Y; Muzaffar, S; Osborne, I; Paul, T; Reucroft, S; 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Yoo, H D; Zheng, Y; Jindal, P; Parashar, N; Cuplov, V; Ecklund, K M; Geurts, F J M; Liu, J H; Maronde, D; Matveev, M; Padley, B P; Redjimi, R; Roberts, J; Sabbatini, L; Tumanov, A; Betchart, B; Bodek, A; Budd, H; Chung, Y S; de Barbaro, P; Demina, R; Flacher, H; Gotra, Y; Harel, A; Korjenevski, S; Miner, D C; Orbaker, D; Petrillo, G; Vishnevskiy, D; Zielinski, M; Bhatti, A; Demortier, L; Goulianos, K; Hatakeyama, K; Lungu, G; Mesropian, C; Yan, M; Atramentov, O; Bartz, E; Gershtein, Y; Halkiadakis, E; Hits, D; Lath, A; Rose, K; Schnetzer, S; Somalwar, S; Stone, R; Thomas, S; Watts, T L; Cerizza, G; Hollingsworth, M; Spanier, S; Yang, Z C; York, A; Asaadi, J; Aurisano, A; Eusebi, R; Golyash, A; Gurrola, A; Kamon, T; Nguyen, C N; Pivarski, J; Safonov, A; Sengupta, S; Toback, D; Weinberger, M; Akchurin, N; Berntzon, L; Gumus, K; Jeong, C; Kim, H; Lee, S W; Popescu, S; Roh, Y; Sill, A; Volobouev, I; Washington, E; Wigmans, R; Yazgan, E; Engh, D; Florez, C; Johns, W; Pathak, S; Sheldon, P; Andelin, D; Arenton, M W; Balazs, M; Boutle, S; Buehler, M; Conetti, S; Cox, B; Hirosky, R; Ledovskoy, A; Neu, C; Phillips II, D; Ronquest, M; Yohay, R; Gollapinni, S; Gunthoti, K; Harr, R; Karchin, P E; Mattson, M; Sakharov, A; Anderson, M; Bachtis, M; Bellinger, J N; Carlsmith, D; Crotty, I; Dasu, S; Dutta, S; Efron, J; Feyzi, F; Flood, K; Gray, L; Grogg, K S; Grothe, M; Hall-Wilton, R; Jaworski, M; Klabbers, P; Klukas, J; Lanaro, A; Lazaridis, C; Leonard, J; Loveless, R; Magrans de Abril, M; Mohapatra, A; Ott, G; Polese, G; Reeder, D; Savin, A; Smith, W H; Sourkov, A; Swanson, J; Weinberg, M; Wenman, D; Wensveen, M; White, A

2010-01-01

Studies of the performance of the CMS drift tube barrel muon system are described, with results based on data collected during the CMS Cosmic Run at Four Tesla. For most of these data, the solenoidal magnet was operated with a central field of 3.8 T. The analysis of data from 246 out of a total of 250 chambers indicates a very good muon reconstruction capability, with a coordinate resolution for a single hit of about 260 microns, and a nearly 100% efficiency for the drift tube cells. The resolution of the track direction measured in the bending plane is about 1.8 mrad, and the efficiency to reconstruct a segment in a single chamber is higher than 99%. The CMS simulation of cosmic rays reproduces well the performance of the barrel muon detector.

Study of Streamers in Gradient Density Air: Table Top Modeling of Red Sprites

Science.gov (United States)

Opaits, D. F.; Shneider, M. N.; Howard, P. J.; Miles, R. B.; Milikh, G. M.

2009-12-01

Sprites and blue jets develop in the upper atmosphere where ambient density changes drastically over their lengths. Theoretical analysis of Red Sprites [1] and Blue Jets [2,3] are based on the streamer tip parameters’ functional dependence on a local gas density N(h). At the moment there is a lack of experimental data for streamer propagation in a non-uniform ambient gas density. Small scale experiments in controllable conditions are important for validation of analytical models as well as numerical simulations, which can be used for the investigation of real scale plasma phenomena that develop above thunderclouds. Controllable, non-uniform gas density can be achieved in laboratory conditions in super sonic nozzles, fast centrifuges or gas filled tubes with a non-uniform temperature distribution along the axis. The latter approach was used in the present work. A quartz tube, approximately one foot in length, was filled with air at different pressures. A density gradient was created by heating up the top of the tube while keeping the bottom at room temperature. The discharge was initiated by applying a high voltage pulse to a pin electrode at the top of the tube while a flat electrode was grounded at the bottom. Similar to Red Sprites, the streamer propagates downwards into a region of higher density and stops before reaching the lower electrode while the top electrode remains under high potential. This work will present results of streamer propagation at different pressures and voltages. Measurements of current-voltage characteristics as well as integral images will be presented. 1. Y. P.Raizer, G. M. Milikh, M. N. Shneider, and S. V. Novakovski (1998), J. Phys. D: Appl. Phys. 31, 3255-3264. 2. Y. P.Raizer, G. M. Milikh, and M. N. Shneider (2006), Geophys. Res. Lett., 33, L23801 3. Y .P.Raizer, G. M. Milikh, and M. N. Shneider (2007), J. Atmos. & Solat-Terr. Phys, 69, 925-938

Effect of inhomogeneities on streamer propagation: II. Streamer dynamics in high pressure humid air with bubbles

International Nuclear Information System (INIS)

Babaeva, Natalia Yu; Kushner, Mark J

2009-01-01

The branching of electric discharge streamers in atmospheric pressure air, dense gases and liquids is a common occurrence whose origins are likely found with many causes, both deterministic and stochastic. One mechanism for streamer branching may be inhomogeneities in the path of a streamer which either divert the streamer (typically a region of lower ionization) or produce a new branch (a region of higher ionization). The propagation and branching of streamers in liquids is likely aided by low density inhomogeneities, bubbles; however, modeling of streamers in liquids is made difficult by the lack of transport coefficients. As a first step towards understanding the propagation and branching of streamers in liquids, we investigated the consequences of random inhomogeneities in the form of low pressure bubbles on the propagation of streamers in high pressure humid air. By virtue of their lower density, bubbles have larger E/N (electric field/gas number density) than the ambient gas with larger rates of ionization. The intersection of a streamer with a bubble will focus the plasma into the bubble by virtue of that higher rate of ionization but the details of the interaction depend on the relative sizes of the bubble and streamer. When a streamer intersects a field of bubbles, the large E/N in the bubble avalanches seed electrons produced by photoionization from the streamer. Each bubble then launches both a negative and positive going streamer that may link with those from adjacent bubbles or the original streamer. The total process then appears as streamer branching.

Development of small-diameter lead-glass-tube matrices for gamma-ray conversion in positron emission tomography

International Nuclear Information System (INIS)

Schwartz, G.M.

1985-05-01

A gamma-ray converter for a multiwire proportional chamber (MWPC) positron emission tomograph is described. The converter is made of small-diameter (0.48 mm inner diameter, 0.06 mm wall thickness) lead-oxide-glass tubes fused to form a honeycomb matrix. The surfaces of the tubes are reduced in a hydrogen atmosphere to provide the drift electric field for detection of the conversion electrons. The detection efficiency for a 10 mm thick converter is 6.65%, with a time resolution of 160 ns (FWHM). A scheme which will improve the spatial resolution of the tomograph by use of the self quenching streamer mode of chamber operation is described. Details of construction of the converters and the MWPC are presented, as well as the design performance of a high spatial resolution positron emission tomograph (HISPET). 40 refs., 22 figs

Large-Scale Production of Monitored Drift Tube Chambers for the ATLAS Muon Spectrometer

CERN Document Server

Bauer, F.; Kortner, O; Kroha, H; Manz, A; Mohrdieck, S; Richter, R; Zhuravlov, V

2016-01-01

Precision drift tube chambers with a sense wire positioning accuracy of better than 20 microns are under construction for the ATLAS muon spectrometer. 70% of the 88 large chambers for the outermost layer of the central part of the spectrometer have been assembled. Measurements during chamber construction of the positions of the sense wires and of the sensors for the optical alignment monitoring system demonstrate that the requirements for the mechanical precision of the chambers are fulfilled.

Investigation of $pp\\bar$ Events at 540 GeV c.m. Energy with a Streamer Chamber Detection System

CERN Multimedia

2002-01-01

The SPS Collider offers an opportunity to study hadronically-produced events in an entirely new energy domain. The UA5 Collaboration is investigating many features of the physics of 540 GeV proton-antiproton collisions, including 1) charged particle production; pseudorapidity and multiplicity distributions 2) photon production; pseudorapidity distributions 3) charged-charged and charged-neutral particle correlations 4) neutral and charged strange particle production and their p^t-distributions 5)~~a special study of high multiplicity events; search for Centauro events,~etc. .in;.sk; The basic detector consists of two large (6m) streamer chambers, triggered by hodoscopes at either end and at 90|0, and viewed by cameras via image intensifiers. Charged tracks can be observed down to 3/4|0, and hence over most of the pseudorapidity range (!@h!$<$5.0) in which they are produced; photons are observed over the same pseudorapidity range. Neutral and charged particle decays are identified over !@h!$<$3. New comp...

Construction of monitored drift tube chambers for ATLAS end-cap muon spectrometer at IHEP (Protvino)

CERN Document Server

Bensinger, J; Borisov, A; Fakhrutdinov, R M; Goryatchev, S; Goryachev, V N; Gushchin, V; Hashemi, K S; Kojine, A; Kononov, A I; Larionov, A; Paramoshkina, E; Pilaev, A; Skvorodnev, N; Tchougouev, A; Wellenstein, H

2002-01-01

Trapezoidal-shaped Monitored Drift Tube (MDT) chambers will be used in end-caps of ATLAS muon spectrometer. Design and construction technology of such chambers in IHEP (Protvino) is presented. X-ray tomography results confirm desirable 20 mum precision of wire location in the chamber.

[Characterizing the passive opening of the eustachian tube in a hypo-/hyperbaric pressure chamber].

Science.gov (United States)

Meyer, M F; Mikolajczak, S; Luers, J C; Lotfipour, S; Beutner, D; Jumah, M D

2013-09-01

Beside arbitrary and not arbitrary active pressure equalization systems there is a passive equalization system via the Eustachian tube (ET) at pressure difference between the epipharyngeal space and the middle ear. Aim of this study was to characterize this passive equalization system in a hypobaric/hyperbaric pressure chamber by continuously measuring the tympanic impedance. In contrast to other studies, which are measured only in a hypobaric pressure chamber it is possible to include participants with Eustachian tube dysfunction (ETD). Following a fixed pressure profile 39 participants were exposed to phases of pressure rising and decompression. By continuously measuring the tympanic impedance in the pressure chamber it was possible to measure data of the Eustachian Tube opening Pressure (ETOP), Eustachian Tube closing pressure (ETCP) and Eustachian Tube opening duration (ETOD). In addition it was possible to characterize the gradient of pressure during decompression, while the ET was open. Beside the measurement of the arithmetic average of the ETOP (30.2 ± 15.1 mbar), ETCP (9.1 ± 7.7 mbar) and ETOD (0.65 ± 0.38 s) it was obvious that there are recurrent samples of pressure progression during the phase of tube opening. Generally it is possible to differentiate between the type of complete opening and partial opening. The fundamental characterization of the action of the passive tube opening, including the measurement of the ETOP, ETCP and ETOD, is a first step in understanding the physiological and pathophysiological function of the ET. © Georg Thieme Verlag KG Stuttgart · New York.

Streamer knotwilg branching: sudden transition in morphology of positive streamers in high-purity nitrogen

International Nuclear Information System (INIS)

Heijmans, L C J; Clevis, T T J; Nijdam, S; Van Veldhuizen, E M; Ebert, U

2015-01-01

We describe a peculiar branching phenomenon in positive repetitive streamer discharges in high purity nitrogen. We name it knotwilg branching after the Dutch word for a pollard willow tree. In a knotwilg branching a thick streamer suddenly splits into many thin streamers. Under some conditions this happens for all streamers in a discharge at about the same distance from the high-voltage electrode tip. At this distance, the thick streamers suddenly bend sharply and appear to propagate over a virtual surface surrounding the high-voltage electrode, rather than following the background electric field lines. From these bent thick streamers many, much thinner, streamers emerge that roughly follow the background electric field lines, creating the characteristic knotwilg branching. We have only found this particular morphology in high purity nitrogen at pressures in the range 50 to 200 mbar and for pulse repetition rates above 1 Hz; the experiments were performed for an electrode distance of 16 cm and for fast voltage pulses of 20 or 30 kV. These observations clearly disagree with common knowledge on streamer propagation. We have analyzed the data of several tens of thousands of discharges to clarify the phenomena. We also present some thoughts on how the ionization of the previous discharges could concentrate into some pre-ionization region near the needle electrode and create the knotwilg morphology, but we present no final explanation. (paper)

Use of gas mixture electroluminescence for optical data readout from wire chambers

International Nuclear Information System (INIS)

Polyakov, V.A.; Rykalin, V.I.; Tskhadadze, Eh.G.

1988-01-01

The radiation spectra, the values of electroluminescence yield and coefficients of gas amplification of Ar and Ne mixture with inorganic and organic additions in a wire chamber operating under proportional and self-quenching streamer conditions are measured. Maximum light yield: 2x10 7 photons for Ar+acetone+white spirit gas mixture in a proportional regime and 1.1x10 7 photons for Ar+CO 2 + ethyl alcohol+ white spirit in self-quenching streamer regime is obtained. Three methods of optical data readout from the wire chambers are tested. The best results are obtained when spectrum shifting bands and fibers are placed behind the chamber cathode planes

Land Streamer Surveying Using Multiple Sources

KAUST Repository

Mahmoud, Sherif

2014-12-11

Various examples are provided for land streamer seismic surveying using multiple sources. In one example, among others, a method includes disposing a land streamer in-line with first and second shot sources. The first shot source is at a first source location adjacent to a proximal end of the land streamer and the second shot source is at a second source location separated by a fixed length corresponding to a length of the land streamer. Shot gathers can be obtained when the shot sources are fired. In another example, a system includes a land streamer including a plurality of receivers, a first shot source located adjacent to the proximal end of the land streamer, and a second shot source located in-line with the land streamer and the first shot source. The second shot source is separated from the first shot source by a fixed overall length corresponding to the land streamer.

The multiscale nature of streamers

International Nuclear Information System (INIS)

Ebert, U; Montijn, C; Briels, T M P; Hundsdorfer, W; Meulenbroek, B; Rocco, A; Veldhuizen, E M van

2006-01-01

Streamers are a generic mode of electric breakdown of large gas volumes. They play a role in the initial stages of sparks and lightning, in technical corona reactors and in high altitude sprite discharges above thunderclouds. Streamers are characterized by a self-generated field enhancement at the head of the growing discharge channel. We briefly review recent streamer experiments and sprite observations. Then we sketch our recent work on computations of growing and branching streamers, we discuss concepts and solutions of analytical model reductions and we review different branching concepts and outline a hierarchy of model reductions

The multiscale nature of streamers

Energy Technology Data Exchange (ETDEWEB)

Ebert, U [Centrum voor Wiskunde en Informatica (CWI), PO Box 94079, 1090GB Amsterdam (Netherlands); Faculty of Physics, Eindhoven University of Technology, PO Box 513, 5600MB Eindhoven (Netherlands); Montijn, C [Centrum voor Wiskunde en Informatica (CWI), PO Box 94079, 1090GB Amsterdam (Netherlands); Briels, T M P [Faculty of Physics, Eindhoven University of Technology, PO Box 513, 5600MB Eindhoven (Netherlands); Hundsdorfer, W [Centrum voor Wiskunde en Informatica (CWI), PO Box 94079, 1090GB Amsterdam (Netherlands); Meulenbroek, B [Centrum voor Wiskunde en Informatica (CWI), PO Box 94079, 1090GB Amsterdam (Netherlands); Rocco, A [Centrum voor Wiskunde en Informatica (CWI), PO Box 94079, 1090GB Amsterdam (Netherlands); University of Oxford, Department of Statistics, 1 South Parks Road, Oxford OX1 3TG (United Kingdom); Veldhuizen, E M van [Faculty of Physics, Eindhoven University of Technology, PO Box 513, 5600MB Eindhoven (Netherlands)

2006-05-15

Streamers are a generic mode of electric breakdown of large gas volumes. They play a role in the initial stages of sparks and lightning, in technical corona reactors and in high altitude sprite discharges above thunderclouds. Streamers are characterized by a self-generated field enhancement at the head of the growing discharge channel. We briefly review recent streamer experiments and sprite observations. Then we sketch our recent work on computations of growing and branching streamers, we discuss concepts and solutions of analytical model reductions and we review different branching concepts and outline a hierarchy of model reductions.

Construction and Test of Muon Drift Tube Chambers for High Counting Rates

CERN Document Server

Schwegler, Philipp; Dubbert, Jörg

2010-01-01

Since the start of operation of the Large Hadron Collider (LHC) at CERN on 20 November 2009, the instantaneous luminosity is steadily increasing. The muon spectrometer of the ATLAS detector at the LHC is instrumented with trigger and precision tracking chambers in a toroidal magnetic field. Monitored Drift-Tube (MDT) chambers are employed as precision tracking chambers, complemented by Cathode Strip Chambers (CSC) in the very forward region where the background counting rate due to neutrons and γ's produced in shielding material and detector components is too high for the MDT chambers. After several upgrades of the CERN accelerator system over the coming decade, the instantaneous luminosity is expected to be raised to about five times the LHC design luminosity. This necessitates replacement of the muon chambers in the regions with the highest background radiation rates in the so-called Small Wheels, which constitute the innermost layers of the muon spectrometer end-caps, by new detectors with higher rate cap...

Rectangular drift tube characteristics

International Nuclear Information System (INIS)

Denisov, D.S.; Musienko, Yu.V.

1985-01-01

Results on the study of the characteristics of a 50 x 100 mm aluminium drift tube are presented. The tube was filled with argon-methane and argon-isobutane mixtures. With 16 per cent methane concentration the largest deviation from a linear relation between the drift time and the drift path over 50 mm is less than 2 mm. The tube filled with argon-isobutane mixture is capable of operating in a limited streamer mode

Performance of the ATLAS Muon Drift-Tube Chambers at High Background Rates and in Magnetic Fields

CERN Document Server

INSPIRE-00213689; Horvat, S.; Legger, F.; Kortner, O.; Kroha, H.; Richter, R.; Valderanis, Ch.; Rauscher, F.; Staude, A.

2016-01-01

The ATLAS muon spectrometer uses drift-tube chambers for precision tracking. The performance of these chambers in the presence of magnetic field and high radiation fluxes is studied in this article using test-beam data recorded in the Gamma Irradiation Facility at CERN. The measurements are compared to detailed predictions provided by the Garfield drift-chamber simulation programme.

Land Streamer Surveying Using Multiple Sources

KAUST Repository

Mahmoud, Sherif; Schuster, Gerard T.

2014-01-01

are fired. In another example, a system includes a land streamer including a plurality of receivers, a first shot source located adjacent to the proximal end of the land streamer, and a second shot source located in-line with the land streamer and the first

Diameter-speed relation of sprite streamers

International Nuclear Information System (INIS)

Kanmae, T; Stenbaek-Nielsen, H C; McHarg, M G; Haaland, R K

2012-01-01

Propagation and splitting of sprite streamers has been observed at high temporal and spatial resolution using two intensified high-speed CMOS cameras recording at 10 000 and 16 000 frames per second. Concurrent video recordings from a remote site provided data for triangulation allowing us to determine accurate altitude scales for the sprites. Diameters and speeds of the sprite streamers were measured from the high-speed images, and the diameters were scaled to the reduced diameters based on the triangulated locations. The sprite streamers with larger reduced diameter move faster than those with smaller diameter; the relation between the reduced diameter and speed is roughly linear. The reduced diameters at ≈65-70 km altitude are larger than streamer diameters measured at ground pressure in laboratory discharges indicating a deviation from the similarity law possibly due to the effects of the photoionization and an expansion of the streamer head along its propagation over a long distance. The reduced diameter and speed of the sprite streamers agree well with the diameter-velocity relation proposed by Naidis (2009 Phys. Rev. E 79 057401), and the peak electric field of the sprite streamers is estimated to be approximately 3-5 times the breakdown threshold field. (paper)

Evolution of streamer groups in nonthermal plasma

Energy Technology Data Exchange (ETDEWEB)

Okubo, M., E-mail: mokubo@me.osakafu-u.ac.jp [Department of Mechanical Engineering, Osaka Prefecture University, 1-1 Gakuen-cho, Naka-ku, Sakai 599-8531 (Japan)

2015-12-15

Nonthermal plasmas (NTPs) induced by atmospheric nanosecond pulsed corona discharge have been studied for controlling pollution from combustors, such as boilers, incinerators, and diesel engines. In high-speed short-width high-voltage pulsed corona discharge-induced plasmas, primary streamer evolution is followed by secondary streamer evolution. Though this phenomenon is known experimentally, the details of the structures of the streamers and their evolution mechanisms have not been fully clarified. In this letter, we perform quasi two-dimensional numerical analysis of nonequilibrium NTP induced by a nanosecond positive pulsed corona discharge. The continuum fluid equations for two-temperature nonequilibrium NTP are used as governing equations. In this study, 197 gas phase reactions for 25 chemical species and 21 surface reactions on the inner glass wall surface are considered in an air plasma under atmospheric pressure. The simulated behavior of the streamer groups agrees with experimental observations. Soon after the voltage increases on the reactor, primary streamers are formed, which may transit the complete gap, disappearing near the peak voltage. Next, second streamers appear, disappearing at the end of the applied voltage pulse. The streamer wavelength and the distance between the streamers in the axial direction are determined. Moreover, ozone generation is shown to be more significant in the secondary streamer. This simulation will allow better predictions for nanosecond positive pulsed plasma systems.

Evolution of streamer groups in nonthermal plasma

Science.gov (United States)

Okubo, M.

2015-12-01

Nonthermal plasmas (NTPs) induced by atmospheric nanosecond pulsed corona discharge have been studied for controlling pollution from combustors, such as boilers, incinerators, and diesel engines. In high-speed short-width high-voltage pulsed corona discharge-induced plasmas, primary streamer evolution is followed by secondary streamer evolution. Though this phenomenon is known experimentally, the details of the structures of the streamers and their evolution mechanisms have not been fully clarified. In this letter, we perform quasi two-dimensional numerical analysis of nonequilibrium NTP induced by a nanosecond positive pulsed corona discharge. The continuum fluid equations for two-temperature nonequilibrium NTP are used as governing equations. In this study, 197 gas phase reactions for 25 chemical species and 21 surface reactions on the inner glass wall surface are considered in an air plasma under atmospheric pressure. The simulated behavior of the streamer groups agrees with experimental observations. Soon after the voltage increases on the reactor, primary streamers are formed, which may transit the complete gap, disappearing near the peak voltage. Next, second streamers appear, disappearing at the end of the applied voltage pulse. The streamer wavelength and the distance between the streamers in the axial direction are determined. Moreover, ozone generation is shown to be more significant in the secondary streamer. This simulation will allow better predictions for nanosecond positive pulsed plasma systems.

Study of the performance of ATLAS muon drift-tube chambers in magntic fields and at high irradiation rates

Energy Technology Data Exchange (ETDEWEB)

Valderanis, Chrysostomos

2012-07-26

The performance of ATLAS muon drift-tube (MDT) chambers has been studied in detail using high-energy muon beams. The measurements of the drift tube properties in magnetic fields showed that inelastic collisions of the drifting electrons with the CO{sub 2} molecules in the Ar:CO{sub 2} (93:7) gas mixture of the MDT chambers have to be taken into account in the simulation of the drift properties. Such inelastic collisions are now correctly treated by the Garfield simulation programme from version 9 providing an accurate description of the behaviour of the ATLAS muon drift tubes, in particular in the magnetic field. Measurements at the Gamma Irradiation Facility at CERN were performed to study the performance of the MDT chambers in the presence of high {gamma} ray background fluences. The chambers have a spatial resolution better than 40 {mu}m at the nominal background rates expected at the Large Hadron Collider design luminosity of 10{sup 34} cm{sup -2}s{sup -1} and a resolution better than 50 {mu}m for up to five times higher background rates. Efficient muon detection up to background counting rates of 500 kHz per tube corresponding to 35% occupancy was demonstrated.

Magnetic field influence on the selfquenching streamer discharge

International Nuclear Information System (INIS)

Alekseev, G.D.; Korytov, A.V.

1987-01-01

The influence of the magnetic field on the selfquenching streamer discharge characteristics is investigated. In the field about 10 kGs streamer charge is decreased several per cent (change of charge is due to amplitude decreasing of signal). In the transition region from limited-proportional to streamer mode magnetic field results in increasing of probability of avalanche developing into a streamer

Pulsed positive corona streamer propagation and branching

International Nuclear Information System (INIS)

Veldhuizen, E.M. van; Rutgers, W.R.

2002-01-01

The propagation and branching of pulsed positive corona streamers in a short gap is observed with high resolution in space and time. The appearance of the pre-breakdown phenomena can be controlled by the electrode configuration, the gas composition and the impedance of the pulsed power circuit. In a point-wire gap the positive corona shows much more branching than in the parallel plane gap with a protrusion. In air, the branching is more pronounced than in argon. The pulsed power circuit appears to operate in two modes, either as an inductive circuit creating a lower number of thick streamers or as a resistive circuit giving a higher number of thin streamers. A possible cause for branching is electrostatic repulsion of two parts of the streamer head. The electric field at the streamer head is limited, the maximum values found are ∼170 kV cm -1 in air and ∼100 kV cm -1 in argon. At these maximum field strengths, the electrons have 5-10 eV energy, so the ionization is dominated by two-step processes. Differences between argon and ambient air in the field strength at which streamers propagate are ascribed to the difference in de-excitation processes in noble and molecular gases. The fact that the pulsed power circuit can control the streamer structure is important for applications, but this effect must also be taken into account in fundamental studies of streamer propagation and branching. (author)

Pulsed positive corona streamer propagation and branching

Energy Technology Data Exchange (ETDEWEB)

Veldhuizen, E.M. van [Department of Physics, Technische Universiteit Eindhoven, Eindhoven (Netherlands)]. E-mail: e.m.v.veldhuizen@tue.nl; Rutgers, W.R. [Department of Physics, Technische Universiteit Eindhoven, Eindhoven (Netherlands)

2002-09-07

The propagation and branching of pulsed positive corona streamers in a short gap is observed with high resolution in space and time. The appearance of the pre-breakdown phenomena can be controlled by the electrode configuration, the gas composition and the impedance of the pulsed power circuit. In a point-wire gap the positive corona shows much more branching than in the parallel plane gap with a protrusion. In air, the branching is more pronounced than in argon. The pulsed power circuit appears to operate in two modes, either as an inductive circuit creating a lower number of thick streamers or as a resistive circuit giving a higher number of thin streamers. A possible cause for branching is electrostatic repulsion of two parts of the streamer head. The electric field at the streamer head is limited, the maximum values found are {approx}170 kV cm{sup -1} in air and {approx}100 kV cm{sup -1} in argon. At these maximum field strengths, the electrons have 5-10 eV energy, so the ionization is dominated by two-step processes. Differences between argon and ambient air in the field strength at which streamers propagate are ascribed to the difference in de-excitation processes in noble and molecular gases. The fact that the pulsed power circuit can control the streamer structure is important for applications, but this effect must also be taken into account in fundamental studies of streamer propagation and branching. (author)

Streamer head structure: role of ionization and photoionization

International Nuclear Information System (INIS)

Nudnova, M M; Starikovskii, A Yu

2008-01-01

Results from experiments and numerical modelling of streamer propagation are presented. The 2D hydrodynamic numerical description of the pulsed discharge based on the local ionization and photoionization models adequately describes the streamer shape and dynamics over a wide range of pressures and voltages. This work presents a method for imaging the instantaneous emission distribution in the streamer head. A method for restoring the electrodynamic radius of the streamer head was developed on the basis of the streamer head images that were obtained with subnanosecond exposure time. The electrodynamic radius has been determined as the distance between the maxima of the electric field at the position where the streamer head transforms into the streamer channel. The dependence of the electrodynamic radius on voltage and pressure has been determined. We show that a 2D numerical model using hydrodynamic approximation predicts the streamer characteristics with an accuracy of about 15% in the 0.5-1 atmosphere pressure range and up to 40% in the 0.2-0.3 atmosphere pressure range for a voltage of U from 20 kV up to 40 kV in the 30 and 40 mm discharge gap.

Analysis and Evaluation of a Vapor-Chamber Fin-Tube Radiator for High-Power Rankine Cycles

National Research Council Canada - National Science Library

Haller, Henry

1965-01-01

An analytical investigation of a flat, direct- condensing fin-tube radiator employing segmented vapor-chamber fins as a means of improving heat rejection was performed A for illustrative high-power...

Optimization and Calibration of the Drift-Tube Chambers for the ATLAS Muon Spectrometer

CERN Document Server

AUTHOR|(CDS)2067746

2000-01-01

The final phase of preparations for the ATLAS experiment at the future Large Hadron Collider (LHC) has begun. In the last decade the collaboration has carried out various test-beam experiments to study and optimize prototypes of all subdetectors under more and more realistic conditions. To enhance the detector-physical understanding, these hardware activities were complemented by detailed simulations. In parallel the development of reconstruction software has made important progress. The present work focusses on some advanced aspects of optimizing the Monitored Drift Tube Chambers (MDT) for operation as precision chambers in the Muon Spectrometer. It will be shown how this system has been tuned for maximum performance in order to meet the ambitious goals defined by the objectives of LHC particle physics. After defining the basic detector parameters, the tubes' capability of running in ATLAS's high-rate gamma radiation background was verified. Both tasks necessitated several years of gathering experience in mu...

Bacterial streamers in curved microchannels

Science.gov (United States)

Rusconi, Roberto; Lecuyer, Sigolene; Guglielmini, Laura; Stone, Howard

2009-11-01

Biofilms, generally identified as microbial communities embedded in a self-produced matrix of extracellular polymeric substances, are involved in a wide variety of health-related problems ranging from implant-associated infections to disease transmissions and dental plaque. The usual picture of these bacterial films is that they grow and develop on surfaces. However, suspended biofilm structures, or streamers, have been found in natural environments (e.g., rivers, acid mines, hydrothermal hot springs) and are always suggested to stem from a turbulent flow. We report the formation of bacterial streamers in curved microfluidic channels. By using confocal laser microscopy we are able to directly image and characterize the spatial and temporal evolution of these filamentous structures. Such streamers, which always connect the inner corners of opposite sides of the channel, are always located in the middle plane. Numerical simulations of the flow provide evidences for an underlying hydrodynamic mechanism behind the formation of the streamers.

Pressure Drop Versus Flow Rate Analysis of the Limited Streamer Tube Gas System of the BaBar Muon Detector Upgrade

International Nuclear Information System (INIS)

Yi, M.

2004-01-01

It has been proposed that Limited Streamer Tubes (LST) be used in the current upgrade of the muon detector in the BaBar detector. An LST consists of a thin silver plated wire centered in a graphite-coated cell. One standard LST tube consists of eight such cells, and two or three such tubes form an LST module. Under operation, the cells are filled with a gas mixture of CO 2 , argon and isobutane. During normal operation of the detector, the gas will be flushed out of the system at a constant low rate of one volume change per day. During times such as installation, however, it is often desired to flush and change the LST gas volumes very rapidly, leading to higher than normal pressure which may damage the modules. This project studied this pressure as a function of flow rate and the number of modules that are put in series in search of the maximal safe flow rate at which to flush the modules. Measurements of pressure drop versus flow rate were taken using a flow meter and a pressure transducer on configurations of one to five modules put in series. Minimal Poly-Flo tubing was used for all connections between test equipment and modules. They contributed less than 25% to all measurements. A ratio of 0.00022 ± 0.00001 mmHg per Standard Cubic Centimeter per Minute (SCCM) per module was found, which was a slight overestimate since it included the contributions from the tubing connections. However, for the purpose of finding a flow rate at which the modules can be safely flushed, this overestimate acts as a safety cushion. For a standard module with a volume of 16 liters and a known safe overpressure of 2 inches of water, the ratio translates into a flow rate of 17000 ± 1000SCCM and a time requirement of 56 ± 5 seconds to flush an entire module

Stochastic and deterministic causes of streamer branching in liquid dielectrics

International Nuclear Information System (INIS)

Jadidian, Jouya; Zahn, Markus; Lavesson, Nils; Widlund, Ola; Borg, Karl

2013-01-01

Streamer branching in liquid dielectrics is driven by stochastic and deterministic factors. The presence of stochastic causes of streamer branching such as inhomogeneities inherited from noisy initial states, impurities, or charge carrier density fluctuations is inevitable in any dielectric. A fully three-dimensional streamer model presented in this paper indicates that deterministic origins of branching are intrinsic attributes of streamers, which in some cases make the branching inevitable depending on shape and velocity of the volume charge at the streamer frontier. Specifically, any given inhomogeneous perturbation can result in streamer branching if the volume charge layer at the original streamer head is relatively thin and slow enough. Furthermore, discrete nature of electrons at the leading edge of an ionization front always guarantees the existence of a non-zero inhomogeneous perturbation ahead of the streamer head propagating even in perfectly homogeneous dielectric. Based on the modeling results for streamers propagating in a liquid dielectric, a gauge on the streamer head geometry is introduced that determines whether the branching occurs under particular inhomogeneous circumstances. Estimated number, diameter, and velocity of the born branches agree qualitatively with experimental images of the streamer branching

Radio Frequency Electromagnetic Radiation From Streamer Collisions.

Science.gov (United States)

Luque, Alejandro

2017-10-16

We present a full electromagnetic model of streamer propagation where the Maxwell equations are solved self-consistently together with electron transport and reactions including photoionization. We apply this model to the collision of counter-propagating streamers in gaps tens of centimeters wide and with large potential differences of hundreds of kilovolts. Our results show that streamer collisions emit electromagnetic pulses that, at atmospheric pressure, dominate the radio frequency spectrum of an extended corona in the range from about 100 MHz to a few gigahertz. We also investigate the fast penetration, after a collision, of electromagnetic fields into the streamer heads and show that these fields are capable of accelerating electrons up to about 100 keV. By substantiating the link between X-rays and high-frequency radio emissions and by describing a mechanism for the early acceleration of runaway electrons, our results support the hypothesis that streamer collisions are essential precursors of high-energy processes in electric discharges.

Streamer properties and associated x-rays in perturbed air

Science.gov (United States)

Köhn, C.; Chanrion, O.; Babich, L. P.; Neubert, T.

2018-01-01

Streamers are ionization waves in electric discharges. One of the key ingredients of streamer propagation is an ambient gas that serves as a source of free electrons. Here, we explore the dependence of streamer dynamics on different spatial distributions of ambient air molecules. We vary the spatial profile of air parallel and perpendicular to the ambient electric field. We consider local sinusoidal perturbations of 5%-100%, as induced from discharge shock waves. We use a cylindrically symmetric particle-in-cell code to simulate the evolution of bidirectional streamers and compare the electron density, electric field, streamer velocity and electron energy of streamers in uniform air and in perturbed air. In all considered cases, the motion is driven along in decreasing air density and damped along increasing air density. Perturbations of at most 5%-10% change the velocity differences by up to approximately 40%. Perturbations perpendicular to the electric field additionally squeeze or branch streamers. Air variations can thus partly explain the difference of velocities and morphologies of streamer discharges. In cases with large perturbations, electrons gain energies of up to 30 keV compared to 100 eV in uniformly distributed air. For such perturbations parallel to the ambient electric field, we see the spontaneous initiation of a negative streamer; for perpendicular perturbations, x-rays with energies of up to 20 keV are emitted within 0.17 ns.

Quality control results of the drift tubes for the ATLAS MDT-BIS chambers

International Nuclear Information System (INIS)

Alexopoulos, T.; Avramidou, R.; Dris, M.; Filippas, T.A.; Gazis, E.N.; Katsoufis, E.; Maltezos, S.; Savva, P.; Tsipolitis, G.; Tzamariudaki, E.

2006-01-01

ATLAS (A Toroidal LHC ApparatuS) is a general purpose experiment, which will start its operation at the Large Hadron Collider (LHC) at CERN in 2007. The ATLAS detector is designed to study the products of proton-proton collisions at c.m.s. energies of up to 14 TeV. Three Greek Universities have taken the responsibility to construct 112 BIS-MDT (Barrel Inner Small) chambers using 29 000 drift tubes of 170 cm length and 3 cm diameter that have been quality tested before assembly. This work describes the Quality Assurance and Quality Control (QA Q C) procedures for the drift tubes, followed at the High Energy Physics Laboratory of the National Technical University of Athens, while emphasis is given on the obtained results for the above mentioned number of tubes

Extremely far from equilibrium: the multiscale dynamics of streamers

Science.gov (United States)

Ebert, Ute

2012-10-01

Streamers can emerge when high voltages are applied to gases. At their tips, the electric field is strongly enhanced, and electron energies locally reach distributions very far from equilibrium, with long tails at high energies. These exotic electron energies create radiation and chemical excitations at very low energy input, as the gas stays cold while the ionization front passes. Applications are multiple: highly efficient O* radical production in air for disinfection, combustion gas cleaning, plasma assisted combustion, plasma bullets in medicine etc. In that sense, streamers can be considered as very efficient converters of pulsed electric into chemical energy, in particular, if the electric circuits are optimized for the application. Streamers are also ubiquitous in nature, e.g., in the streamer corona of lightning leaders, in sprite discharges high above the clouds; and streamers also seem to contribute to generating gamma-ray flashes and even to electron-positron beams in active thunderstorms. Unravelling the intrinsic mechanisms of streamers is challenging: they can move with up to one tenth of the speed of light, and they have an intricate nonlinear structure with a hierarchy of scales. I will review how theory and experiment deal with these structures, and I will discuss the basic differences between positive and negative streamers, electron acceleration at streamer tips and the consecutive radiation and chemical reactions, the propagation mechanism of positive streamers in different gases, streamer velocities and diameters varying over at least two orders of magnitude, streamer branching and interaction, and their three-dimensional tree structure. Both theory and experiment work with a patchwork of methods, and geophysics can provide movies that cannot be taken in the lab. I will sketch the state and outline open questions.

Optical Emissions of Sprite Streamers in Weak Electric Fields

Science.gov (United States)

Liu, N.; Pasko, V. P.

2004-12-01

Sprites commonly consist of large numbers of needle-shaped filaments of ionization [e.g., Gerken and Inan, JASTP, 65, 567, 2003] and typically initiate at altitudes 70-75 km in a form of upward and downward propagating streamers [Stanley et al., GRL, 26, 3201, 1999; Stenbaek-Nielsen et al., GRL, 27, 3829, 2000; McHarg et al., JGR, 107, 1364, 2002; Moudry et al., JASTP, 65, 509, 2003]. The strong electric fields E exceeding the conventional breakdown threshold field Ek are needed for initiation of sprite streamers from single electron avalanches and recent modeling studies indicate that streamers propagating in fields E>Ek experience strong acceleration and expansion in good agreement with the above cited observations [Liu and Pasko, JGR, 109, A04301, 2004]. The initiated streamers are capable of propagating in fields substantially lower than Ek [Allen and Ghaffar, J. Phys. D: Appl. Phys., 28, 331, 1995] and it is expected that a significant part of sprite optical output comes from regions with EEk). Additionally, the values of electric fields inside of the streamer channel are always well below Ek and since the excitation coefficients for optical emissions are very sensitive to the driving electric field magnitude most of the optical luminosity of streamers in this case arises from streamer tips, indicating that observed streamer filaments in many cases may be produced by time averaging of optical luminosity coming from localized regions around streamer tips as streamers move through an instrument's field of view. We will discuss pressure dependent differences of optical emissions at different sprite altitudes, and important similarities between observed sprite streamers and recent time resolved (van Veldhuizen et al., IEEE Trans. Plasma Sci., 30, 162, 2002; Yi and Williams, J. Phys. D. Appl. Phys., 35, 205, 2002].

A high-precision X-ray tomograph for quality control of the ATLAS Muon Monitored Drift Tube Chambers

CERN Document Server

Schuh, S; Banhidi, Z; Fabjan, Christian Wolfgang; Lampl, W; Marchesotti, M; Rangod, Stephane; Sbrissa, E; Smirnov, Y; Voss, Rüdiger; Woudstra, M; Zhuravlov, V

2004-01-01

A dedicated X-ray tomograph has been developed at CERN to control the required wire placement accuracy of better than 20mum of the 1200 Monitored Drift Tube Chambers which make up most of the precision chamber part of the ATLAS Muon Spectrometer. The tomograph allows the chamber wire positions to be measured with a 2mum statistical and 2mum systematic uncertainty over the full chamber cross-section of 2.2 multiplied by 0.6m**2. Consistent chamber production quality over the 4-year construction phase is ensured with a similar to 15% sampling rate. Measurements of about 70 of the 650 MDT chambers so far produced have been essential in assessing the validity and consistency of the various construction procedures.

Modeling of a new electron-streamer acceleration mechanism

Science.gov (United States)

Ihaddadene, K. M. A.; Dwyer, J. R.; Liu, N.; Celestin, S. J.

2017-12-01

Lightning stepped leaders and laboratory spark discharges in air are known to produce X-rays [e.g., Dwyer et al., Geophys. Res. lett., 32, L20809, 2005; Kochkin et al., J. Phys. D: Appl. Phys., 45, 425202, 2012]. However, the processes behind the production of these X-rays are still not very well understood. During discharges, encounters between streamers of different polarities are very common. For example, during the formation of a new leader step, the negative streamer zone around the tip of a negative leader and the positive streamers initiated from the posiive part of a bidirectional space leader strongly interact. In laboratory experiments, when streamers are approaching a sharp electrode, streamers with the opposite polarity are initiated from the electrode and collide with the former streamers. Recently, the encounter between negative and positive streamers has been proposed as a plausible mechanism for the production of X-rays by spark discharges [Cooray et la., JASTP, 71, 1890, 2009; Kochkin et al., J. Phys. D: Appl. Phys., 45, 425202, 2012], but modeling results have shown later that the increase of the electric field involved in this process, which is above the conventional breakdown threshold field, is accompanied by a strong increase of the electron density. The resulting increase in the conductivity, in turn, causes this electric field to collapse over a few tens of picoseconds, preventing the electrons reaching high energies and producing significant X-ray emissions [e.g., Ihaddadene and Celestin, Geophys. Res. Lett., 45, 5644, 2015]. In this work, we will present simulation results of a new electron acceleration mechanism for producing runaway electron energies above hundred keV. The mechanism couples multiple single streamers and streamer head-on collisions, similar to a laboratory discharge, and is suitable for explaining the high-energy X-rays produced by discharges in air and by lightning stepped leaders.

Two-dimensional simulation of positive and negative streamers in air

International Nuclear Information System (INIS)

Babaeva, N.Yu.; Naidis, G.V.

1998-01-01

The paper deals with 2D numerical simulation of positive and negative streamers in air at atmospheric pressure. The dynamics of an axially symmetric streamer based on a charged sphere is described by a coupled system of equations for the electric field and the density of charged particles. The results of simulation show that the production rate of radicals in short sphere-plane gaps depends only weakly on the discharge conditions, that the streamer velocity in uniform field depends linearly on the streamer length, and the field corresponding to the negative streamer propagation with a constant velocity is 2-3 times greater than that obtained with a positive streamer. (J.U.)

Structure of positive streamers inside gaseous bubbles immersed in liquids

International Nuclear Information System (INIS)

Babaeva, Natalia Yu; Kushner, Mark J

2009-01-01

Electric discharges and streamers in liquids typically proceed through vapour phase channels produced by the streamer or in gaseous bubbles. The bubbles can originate by enthalpy changes produced by the discharge or can be artificially injected into the liquid. Experiments on streamers in bubbles immersed in liquids have shown that the discharge propagates either along the surface of the bubble or through the volume of the bubble as in conventional streamer propagation in air. In this paper we report on results of a computational investigation of streamer propagation through bubbles immersed in liquids. We found that the dielectric constant of the liquid in large part determines the path the streamer takes. Streamers in bubbles immersed in a liquid with a high permittivity preferentially propagate along the surface of the bubble. Liquids with low permittivity can result in the streamer propagating along the axis of the bubble. The permittivity at which this transition occurs is a function of the applied voltage, size of the bubble and the conductivity of the liquid. (fast track communication)

Study of Anterior Chamber Aqueous Tube Shunt by Fourier-Domain Optical Coherence Tomography

Directory of Open Access Journals (Sweden)

Chunhui Jiang

2012-01-01

Full Text Available Purpose. This cross-sectional, observational study used Fourier-domain optical coherence tomography (OCT to examine the position, patency, and the interior entrance site of anterior chamber (AC aqueous tube shunts. Methods. The OCT, slitlamp biomicroscopy, and gonioscopy findings of 23 eyes of 18 patients with AC shunts were collected and compared. Results. OCT images demonstrated the shunt position and patency in all 23 eyes, and the details of the AC entrance in 16 eyes. The position of the tube varied, with the majority (14/23 on the surface of the iris. The exact position of the AC entrance relative to Schwalbe’s line (SL could be determined in 9 eyes (posterior to SL in 7 eyes, anterior in 2 eyes. At the AC entrance, growth of fibrous scar tissue was present between the tube and the corneal endothelium in all 16 eyes in which the entrance could be clearly visualized. It’s a new finding that could not be visualized by slitlamp examination or lower resolution OCT. Conclusion. Compared to slitlamp examination, Fourier-domain OCT of AC tube shunts provided more detailed anatomic information regarding the insertion level relative to SL, scar tissue between the tube and the corneal endothelium, and patency of the tube opening.

Saffman-Taylor streamers: Mutual finger interaction in spark formation

NARCIS (Netherlands)

Luque, A.; Brau, F.; Ebert, U.

2008-01-01

Bunches of streamers form the early stages of sparks and lightning but theory presently concentrates on single streamers or on coarse approximations of whole breakdown trees. Here a periodic array of interacting streamer discharges in a strong homogeneous electric field is studied in density or

Particle-in-cell modeling of streamer branching in CO2 gas

KAUST Repository

Levko, Dmitry

2017-07-07

The mechanism of streamer branching remains one of the unsolved problems of low-temperature plasma physics. The understanding of this phenomenon requires very high-fidelity models that include, for instance, the kinetic description of electrons. In this paper, we use a two-dimensional particle-in-cell Monte Carlo collisional model to study the branching of anode-directed streamers propagating through short cathode-anode gap filled with atmospheric-pressure CO2 gas. We observe three key phenomena leading to the streamer branching at the considered conditions: flattening of the streamer head, the decrease of the streamer head thickness, and the generation at the streamer head of electrons having the energy larger than 50 eV. For the conditions of our studies, the non-homogeneous distribution of such energetic electrons at the streamer head is probably the primary mechanism responsible for the streamer branching.

Fluid and hybrid models for streamers

Science.gov (United States)

Bonaventura, Zdeněk

2016-09-01

Streamers are contracted ionizing waves with self-generated field enhancement that propagate into a low-ionized medium exposed to high electric field leaving filamentary trails of plasma behind. The widely used model to study streamer dynamics is based on drift-diffusion equations for electrons and ions, assuming local field approximation, coupled with Poisson's equation. For problems where presence of energetic electrons become important a fluid approach needs to be extended by a particle model, accompanied also with Monte Carlo Collision technique, that takes care of motion of these electrons. A combined fluid-particle approach is used to study an influence of surface emission processes on a fast-pulsed dielectric barrier discharge in air at atmospheric pressure. It is found that fluid-only model predicts substantially faster reignition dynamics compared to coupled fluid-particle model. Furthermore, a hybrid model can be created in which the population of electrons is divided in the energy space into two distinct groups: (1) low energy `bulk' electrons that are treated with fluid model, and (2) high energy `beam' electrons, followed as particles. The hybrid model is then capable not only to deal with streamer discharges in laboratory conditions, but also allows us to study electron acceleration in streamer zone of lighting leaders. There, the production of fast electrons from streamers is investigated, since these (runaway) electrons act as seeds for the relativistic runaway electron avalanche (RREA) mechanism, important for high-energy atmospheric physics phenomena. Results suggest that high energy electrons effect the streamer propagation, namely the velocity, the peak electric field, and thus also the production rate of runaway electrons. This work has been supported by the Czech Science Foundation research project 15-04023S.

Streamers in water and other dielectric liquids

International Nuclear Information System (INIS)

Kolb, J F; Joshi, R P; Xiao, S; Schoenbach, K H

2008-01-01

Experimental results on the inception and propagation of streamers in water generated under the application of high electric fields are reviewed. Characteristic parameters, such as breakdown voltage, polarity of the applied voltage, propagation velocities and other phenomenological features, are compared with similar phenomena in other dielectric liquids and in gases. Consequently, parameters that are expected to influence the development of streamers in water are discussed with respect to the analogous well-established models and theories for the related mechanisms in gases. Most of the data support the notion that an initial low-density nucleation site or gas-filled bubble assists the initiation of a streamer. Details of this theory are laid out explaining the observed differences in the breakdown originating from the anode versus the cathode locations. The mechanisms can also be applied to streamer propagation, although some observations cannot be satisfactorily explained.

Characteristics of rectangular drift tube for muon identifier

International Nuclear Information System (INIS)

Denisov, D.S.; Musienko, Yu.V.

1987-01-01

The results of a study of an aluminum drift tube with a cross section of 50 x 100 mm are presented. Argon-methane and argon-isobutane mixtures were used as fillers. For a 16% methane concentration, the nonlinearity of the time-coordinate dependence does not exceed 2 mm. The tube can operate in the self-quenched streamer mode when filled with a mixture of argon with isobutane

Modeling of plasma chemistry in a corona streamer pulse series in air

International Nuclear Information System (INIS)

Nowakowska, H.; Stanco, J.; Dors, M.; Mizeraczyk, J.

2002-01-01

The aim of this study is to analyse the chemistry in air treated by a series of corona discharge streamers. Attention is focused on the conversion of ozone and nitrogen oxides. In the model it is assumed that the streamer head of relatively small geometrical dimensions propagates from the anode to the cathode, leaving the streamer channel behind. Any elemental gas volume in the streamer path is subjected first to the conditions of the streamer head, and next to those of the streamer channel. The kinetics of plasma-chemical processes occurring in the gas is modeled numerically for a single streamer and a series of streamers. The temporal evolution of 25 chemical compounds initially present or produced in air is calculated. (author)

Optimisation of the Read-out Electronics of Muon Drift-Tube Chambers for Very High Background Rates at HL-LHC and Future Colliders

CERN Document Server

Nowak, Sebastian; Gadow, Philipp; Ecker, Katharina; Fink, David; Fras, Markus; Kortner, Oliver; Kroha, Hubert; Müller, Felix; Richter, Robert; Schmid, Clemens; Schmidt-Sommerfeld, Korbinian; Zhao, Yazhou

2016-01-01

In the ATLAS Muon Spectrometer, Monitored Drift Tube (MDT) chambers and sMDT chambers with half of the tube diameter of the MDTs are used for precision muon track reconstruction. The sMDT chambers are designed for operation at high counting rates due to neutron and gamma background irradiation expected for the HL-LHC and future hadron colliders. The existing MDT read-out electronics uses bipolar signal shaping which causes an undershoot of opposite polarity and same charge after a signal pulse. At high counting rates and short electronics dead time used for the sMDTs, signal pulses pile up on the undershoot of preceding background pulses leading to a reduction of the signal amplitude and a jitter in the drift time measurement and, therefore, to a degradation of drift tube efficiency and spatial resolution. In order to further increase the rate capability of sMDT tubes, baseline restoration can be used in the read-out electronics to suppress the pile-up effects. A discrete bipolar shaping circuit with baseline...

Construction and Test of New Precision Drift-Tube Chambers for Upgrades of the ATLAS Muon Spectrometer in 2016/17

CERN Document Server

INSPIRE-00218480; Kortner, O.; Müller, F.; Nowak, S.; Schmidt-Sommerfeld, K.

2016-01-01

Small-diameter Muon Drift Tube (sMDT) chambers have been developed for the ATLAS muon detector upgrade. They possess an improved rate capability and a more compact design with respect to the existing chambers, which allows to equip detector regions uninstrument at present. The chamber assembly methods have been optimized for mass production, while the sense wire positioning accuracy is improved to below ten microns. The chambers will be ready for installation in the winter shutdown 2016/17 of the Large Hadron Collider. The design and construction of the new sMDT chambers for ATLAS will be discussed as well as measurements of their precision and performance.

Experimental investigations on the physics of streamers

NARCIS (Netherlands)

Nijdam, S.

2011-01-01

Streamers are rapidly extending ionized fingers that can appear in gasses, liquids and solids. They are generated by high electric fields but can penetrate into areas where the background electric field is below the ionization threshold. Streamers occur in nature as a precursor to sparks and

Resolution and Efficiency of the ATLAS Muon Drift-Tube Chambers at High Background Rates

CERN Document Server

Deile, M.; Horvat, S.; Kortner, O.; Kroha, H.; Manz, A.; Mohrdieck-Mock, S.; Rauscher, F.; Richter, Robert; Staude, A.; Stiller, W.

2016-01-01

The resolution and efficiency of a precision drift-tube chamber for the ATLAS muon spectrometer with final read-out electronics was tested at the Gamma Irradiation Facility at CERN in a 100 GeV muon beam and at photon irradiation rates of up to 990 Hz/square cm which corresponds to twice the highest background rate expected in ATLAS. A silicon strip detector telescope was used as external reference in the beam. The pulse-height measurement of the read-out electronics was used to perform time-slewing corrections which lead to an improvement of the average drift-tube resolution from 104 microns to 82 microns without irradiation and from 128 microns to 108 microns at the maximum expected rate. The measured drift-tube efficiency agrees with the expectation from the dead time of the read-out electronics up to the maximum expected rate.

Propagation of a plasma streamer in catalyst pores

Science.gov (United States)

Zhang, Quan-Zhi; Bogaerts, Annemie

2018-03-01

Although plasma catalysis is gaining increasing interest for various environmental applications, the underlying mechanisms are still far from understood. For instance, it is not yet clear whether and how plasma streamers can propagate in catalyst pores, and what is the minimum pore size to make this happen. As this is crucial information to ensure good plasma-catalyst interaction, we study here the mechanism of plasma streamer propagation in a catalyst pore, by means of a two-dimensional particle-in-cell/Monte Carlo collision model, for various pore diameters in the nm-range to μm-range. The so-called Debye length is an important criterion for plasma penetration into catalyst pores, i.e. a plasma streamer can penetrate into pores when their diameter is larger than the Debye length. The Debye length is typically in the order of a few 100 nm up to 1 μm at the conditions under study, depending on electron density and temperature in the plasma streamer. For pores in the range of ∼50 nm, plasma can thus only penetrate to some extent and at very short times, i.e. at the beginning of a micro-discharge, before the actual plasma streamer reaches the catalyst surface and a sheath is formed in front of the surface. We can make plasma streamers penetrate into smaller pores (down to ca. 500 nm at the conditions under study) by increasing the applied voltage, which yields a higher plasma density, and thus reduces the Debye length. Our simulations also reveal that the plasma streamers induce surface charging of the catalyst pore sidewalls, causing discharge enhancement inside the pore, depending on pore diameter and depth.

ADS and CDS streamer generation as function of pulsed parameters

NARCIS (Netherlands)

Winands, G.J.J.; Liu, Z.; Heesch, van E.J.M.; Pemen, A.J.M.; Yan, K.

2008-01-01

Streamer plasmas can be used to remove pollutants from gases. As a result of the complex mechanisms involved during streamer initiation and propagation, the related knowledge is incomplete. During the last few years, extensive research was performed to determine typical streamer properties (such as

Test of freonless operation of resistive plate chambers with glass electrodes--1 mm gas gap vs 2 mm gas gap

CERN Document Server

Sakaue, H; Takahashi, T; Teramoto, Y

2002-01-01

Non-freon gas mixtures (Ar/iso-C sub 4 H sub 1 sub 0) were tested as the chamber gas for 1 and 2 mm gas gap Resistive Plate Chambers (RPCs) with float glass as the resistive electrodes, operated in the streamer mode. With the narrower (1 mm) gas gap, streamer charge is reduced (approx 1/3), which reduces the dead time (and dead area), associated with each streamer, improving the detection efficiency. The best performance was obtained for two cases: Ar/iso-C sub 4 H sub 1 sub 0 =50/50 and 60/40. For the 50/50 mixture, a detection efficiency of better than 98% was obtained for the 1 mm gap RPC, while the efficiency was 95% for the 2 mm gap RPC, each operated as a double-gap RPC. The measured time resolution (rms) was 1.45+-0.05 (2.52+-0.09) ns for the 1 (2) mm gap RPC for the 50/50 mixture.

Cross-talk in straw tube chambers

Energy Technology Data Exchange (ETDEWEB)

Marzec, J. E-mail: janusz.marzec@ire.pw.edu.pl

2003-05-11

An analytical model of the signal transmission between neighboring straw tubes with resistive cathodes (cross-talk) is presented. The dependence of the cross-talk level on the cathode resistance, tube length, particle detection point, the distance of the tube from the shielding planes, and termination of the tube ends is analyzed.

Cross-talk in straw tube chambers

International Nuclear Information System (INIS)

Marzec, J.

2003-01-01

An analytical model of the signal transmission between neighboring straw tubes with resistive cathodes (cross-talk) is presented. The dependence of the cross-talk level on the cathode resistance, tube length, particle detection point, the distance of the tube from the shielding planes, and termination of the tube ends is analyzed

Reconnection and merging of positive streamers in air

Energy Technology Data Exchange (ETDEWEB)

Nijdam, S; Geurts, C G C; Van Veldhuizen, E M; Ebert, U, E-mail: s.nijdam@tue.n [Department of Applied Physics, Eindhoven University of Technology, PO Box 513, 5600 MB Eindhoven (Netherlands)

2009-02-21

Pictures show that streamer or sprite discharge channels emerging from the same electrode sometimes seem to reconnect or merge though their heads carry electric charge of the same polarity; one might therefore suspect that reconnections are an artefact of the two-dimensional projection in the pictures. Here we use stereo photography to investigate the full three-dimensional structure of such events. We analyse reconnection, possibly an electrostatic effect in which a late thin streamer reconnects to an earlier thick streamer channel, and merging, a suggested photoionization effect in which two simultaneously propagating streamer heads merge into one new streamer. We use four different anode geometries (one tip, two tips, two asymmetric protrusions in a plate and a wire), placed 40 mm above a flat cathode plate in ambient air. A positive high voltage pulse is applied to the anode, creating a positive corona discharge. This discharge is studied with a fast ICCD camera, in many cases combined with optics to enable stereoscopic imaging. We find that reconnections as defined above occur frequently. Merging on the other hand was only observed at a pressure of 25 mbar and a tip separation of 2 mm, i.e. for a reduced tip distance of p{center_dot}d = 50 {mu}m bar. In this case the full width at half maximum of the streamer channel is more than 10 times as large as the tip separation. At higher pressures or with a wire anode, merging was not observed.

Reconnection and merging of positive streamers in air

International Nuclear Information System (INIS)

Nijdam, S; Geurts, C G C; Van Veldhuizen, E M; Ebert, U

2009-01-01

Pictures show that streamer or sprite discharge channels emerging from the same electrode sometimes seem to reconnect or merge though their heads carry electric charge of the same polarity; one might therefore suspect that reconnections are an artefact of the two-dimensional projection in the pictures. Here we use stereo photography to investigate the full three-dimensional structure of such events. We analyse reconnection, possibly an electrostatic effect in which a late thin streamer reconnects to an earlier thick streamer channel, and merging, a suggested photoionization effect in which two simultaneously propagating streamer heads merge into one new streamer. We use four different anode geometries (one tip, two tips, two asymmetric protrusions in a plate and a wire), placed 40 mm above a flat cathode plate in ambient air. A positive high voltage pulse is applied to the anode, creating a positive corona discharge. This discharge is studied with a fast ICCD camera, in many cases combined with optics to enable stereoscopic imaging. We find that reconnections as defined above occur frequently. Merging on the other hand was only observed at a pressure of 25 mbar and a tip separation of 2 mm, i.e. for a reduced tip distance of p·d = 50 μm bar. In this case the full width at half maximum of the streamer channel is more than 10 times as large as the tip separation. At higher pressures or with a wire anode, merging was not observed.

Modelling of the space-to-drift-time relationship of the ATLAS monitored drift-tube chambers in the presence of magnetic fields

International Nuclear Information System (INIS)

Dubbert, J.; Horvat, S.; Khartchenko, D.; Kortner, O.; Kotov, S.; Kroha, H.; Manz, A.; Nikolaev, K.; Rauscher, F.; Richter, R.; Staude, A.; Valderanis, Ch.

2007-01-01

The ATLAS muon spectrometer uses tracking chambers consisting of up to 5m long drift tubes filled with Ar:CO 2 (93:7) at 3bar. The chambers are run in a average toroidal magnetic field of 0.4T created by 8 air core coils. They provide a track-point accuracy of 40μm if the space-to-drift-time relationship r(t) is known with 20μm accuracy. The magnetic field B influences the electron drift inside the tubes: the maximum drift time t max =700ns increases by ∼70ns/T 2 B 2 . B varies by up to +/-0.4T along the tubes of the chambers mounted near the magnet coils which translates into a variation of t max of up to 45ns. The dependence of r(t) on B must be taken into account. Test-beam measurements show that the electron drift in case of B 0 can be modelled with the required accuracy by a Langevin equation with a friction term which is slightly non-linear in the drift velocity

Mechanisms important to later stages of streamer system development

Science.gov (United States)

Lehtinen, N. G.; Carlson, B.; Kochkin, P.; Østgaard, N.

2017-12-01

Typical streamer modeling focuses on the propagation of the streamer head and thus neglects processes such as electron detachment, electron energy relaxation, and thermalization of the electron energy distribution. These mechanisms, however, may become important at later stages of streamer system development, in particular following streamer collisions. We present a model of a later-stage streamer system development which includes these processes. A linear analysis suggests that these processes under some conditions can lead to new effects, such as excitation of waves similar to striations in the positive column of a glow discharge. Such instabilities do not occur if these mechanisms are neglected under the same conditions, although previous modeling suggested existence of wave-like phenomena during the streamer propagation [Luque et al, 2016, doi:10.1002/2015JA022234]. In the sea-level pressure air, the obtained striation-like waves may manifest as very high frequency range (>10 MHz) oscillations in plasma parameters and may have been detected in the electrode current and electromagnetic radiation measurements during laboratory spark experiments. We discuss whether the longitudinal electric field in such waves can efficiently transfer energy to charged particles, because such a process may play a role in production of x-rays.

Circuit dependence of the diameter of pulsed positive streamers in air

Energy Technology Data Exchange (ETDEWEB)

Briels, T M P [Department of Applied Physics, Technische Universiteit Eindhoven, PO Box 513, 5600MB Eindhoven (Netherlands); Kos, J [Department of Applied Physics, Technische Universiteit Eindhoven, PO Box 513, 5600MB Eindhoven (Netherlands); Veldhuizen, E M van [Department of Applied Physics, Technische Universiteit Eindhoven, PO Box 513, 5600MB Eindhoven (Netherlands); Ebert, U [Department of Applied Physics, Technische Universiteit Eindhoven, PO Box 513, 5600MB Eindhoven (Netherlands)

2006-12-21

The diameter and branching structure of positive streamers in ambient air are investigated with a fast iCCD camera. We use different pulsed power circuits and find that they generate different spatial streamer structures. The electrodes have a point-plane geometry and a distance of 40 or 80 mm, and the peak voltages over the discharge gap are up to 60 kV. Depending on circuit and peak voltage, we observe streamers with diameters varying gradually between 0.2 and 2.5 mm. The streamer velocity increases with the diameter, ranging from 0.07 to 1.5 mm ns{sup -1}, while the current density within the streamers stays almost constant. The thicker streamers extend much further before they branch than the thinner ones. The pulsed power supplies are a switched capacitor supply with an internal resistance of 1 k{omega} and a transmission line transformer supply with an impedance of 200 {omega}; additional resistors change the impedance as well as the voltage rise time in the case of the capacitor supply. We observe that short rise times and low impedance create thick streamers close to the pointed electrode, while a longer rise time as well as a higher impedance create thinner streamers at the same peak voltage over the discharge.

Circuit dependence of the diameter of pulsed positive streamers in air

International Nuclear Information System (INIS)

Briels, T M P; Kos, J; Veldhuizen, E M van; Ebert, U

2006-01-01

The diameter and branching structure of positive streamers in ambient air are investigated with a fast iCCD camera. We use different pulsed power circuits and find that they generate different spatial streamer structures. The electrodes have a point-plane geometry and a distance of 40 or 80 mm, and the peak voltages over the discharge gap are up to 60 kV. Depending on circuit and peak voltage, we observe streamers with diameters varying gradually between 0.2 and 2.5 mm. The streamer velocity increases with the diameter, ranging from 0.07 to 1.5 mm ns -1 , while the current density within the streamers stays almost constant. The thicker streamers extend much further before they branch than the thinner ones. The pulsed power supplies are a switched capacitor supply with an internal resistance of 1 kΩ and a transmission line transformer supply with an impedance of 200 Ω; additional resistors change the impedance as well as the voltage rise time in the case of the capacitor supply. We observe that short rise times and low impedance create thick streamers close to the pointed electrode, while a longer rise time as well as a higher impedance create thinner streamers at the same peak voltage over the discharge

Pencil-shaped radiation detection ionization chamber

International Nuclear Information System (INIS)

Suzuki, A.

1979-01-01

A radiation detection ionization chamber is described. It consists of an elongated cylindrical pencil-shaped tubing forming an outer wall of the chamber and a center electrode disposed along the major axis of the tubing. The length of the chamber is substantially greater than the diameter. A cable connecting portion at one end of the chamber is provided for connecting the chamber to a triaxial cable. An end support portion is connected at the other end of the chamber for supporting and tensioning the center electrode. 17 claims

Positive and negative streamers in ambient air: measuring diameter, velocity and dissipated energy

International Nuclear Information System (INIS)

Briels, T M P; Kos, J; Van Veldhuizen, E M; Ebert, U; Winands, G J J

2008-01-01

Positive and negative streamers are studied in ambient air at 1 bar; they emerge from a needle electrode placed 40 mm above a planar electrode. The amplitudes of the applied voltage pulses range from 5 to 96 kV; most pulses have rise times of 30 ns or shorter. Diameters, velocities and energies of the streamers are measured. Two regimes are identified; a low voltage regime where only positive streamers appear and a high voltage regime where both positive and negative streamers exist. Below 5 kV, no streamers emerge. In the range from 5 to 40 kV, positive streamers form, while the negative discharges only form a glowing cloud at the electrode tip, but no streamers. For 5-20 kV, diameters and velocities of the positive streamers have the minimal values of d = 0.2 mm and v ∼ 10 5 m s -1 . For 20-40 kV, their diameters increase by a factor of 6 while the voltage increases only by a factor of 2. Above the transition value of 40 kV, streamers of both polarities form; they strongly resemble each other, though the positive ones propagate further; their diameters continue to increase with applied voltage. For 96 kV, positive streamers attain diameters of 3 mm and velocities of 4 x 10 6 m s -1 ; negative streamers are about 20% slower and thinner. An empirical fit formula for the relation between velocity v and diameter d is v = 0.5d 2 mm -1 ns -1 for both polarities. Streamers of both polarities dissipate energies of the order of several millijoules per streamer while crossing the gap.

The LST analog read-out system of the ZEUS muon detector

International Nuclear Information System (INIS)

De Giorgi, M.; Abbiendi, G.; Bertolin, A.; Borsato, E.; Brugnera, R.; Carlin, R.; Dal Corso, F.; Dosselli, U.; Gasparini, F.; Limentani, S.; Morandin, M.; Pitacco, G.; Posocco, M.; Stanco, L.; Stroili, R.; Voci, C.; Zuin, F.

1996-01-01

A muon position detector based on limited streamer tubes has been built for the ZEUS experiment at the HERA e-p collider at Desy. The tubes are arranged in chambers equipped with electronics circuitry providing an analog read-out of induced signals on strips set orthogonal to the tube wires. The electronic module for charge amplification and conversion will be described including some results obtained from the complete system. (orig.)

SYMPATHETIC FILAMENT ERUPTIONS FROM A BIPOLAR HELMET STREAMER IN THE SUN

International Nuclear Information System (INIS)

Yang Jiayan; Jiang Yunchun; Zheng Ruisheng; Bi Yi; Hong Junchao; Yang Bo

2012-01-01

On 2005 August 5, two solar filaments erupted successively from different confined arcades underlying a common overarching multiple-arcade bipolar helmet streamer. We present detailed observations of these two events and identify them as sympathetic filament eruptions. The first (F1) is a small active-region filament located near the outskirts of the streamer arcade. It underwent a nonradial eruption, initially moving in the interior of the streamer arcade and resulting in an over-and-out coronal mass ejection. The second filament (F2), a larger quiescent one far away from F1, was clearly disturbed during the F1 eruption. It then underwent a very slow eruption and finally disappeared completely and permanently. Because two belt-shaped diffuse dimmings formed along the footprints of the streamer arcade in the first eruption and persisted throughout the complete disappearance of F2, the eruption series are interpreted as sympathetic: the simple expansion of the common streamer arcade forced by the F1 eruption weakened magnetic flux overlying F2 and thus led to its slow eruption, with the dimming formation indicating their physical connection. Our observations suggest that multiple-arcade bipolar helmet-streamer configurations are appropriate to producing sympathetic eruptions. Combined with the recent observations of unipolar-streamer sympathetic events, it appears that a multiple-arcade unipolar or bipolar helmet streamer can serve as a common magnetic configuration for sympathetic eruptions.

Dependence of streamer density on electric field strength on positive electrode

Science.gov (United States)

Koki, Nakamura; Takahumi, Okuyama; Wang, Douyan; Takao, N.; Hidenori, Akiyama; Kumamoto University Collaboration

2015-09-01

Pulsed streamer discharge plasma, a type of non-thermal plasma, is known as generation method of reactive radicals and ozone and treatment of exhausted gas. From our previous research, the distance between electrodes has been considered a very important parameter for applications using pulsed streamer discharge. However, how the distance between electrodes affects the pulsed discharge hasn't been clarified. In this research, the propagation process of pulsed streamer discharge in a wire-plate electrode was observed using an ICCD camera for 4 electrodes having different distance between electrodes. The distance between electrodes was changeable at 45 mm, 40 mm, 35 mm, and 30 mm. The results show that, when the distance between electrodes was shortened, applied voltage with a pulse duration of 100 ns decreased from 80 to 60.3 kV. Conversely, discharge current increased from 149 to 190 A. Streamer head velocity became faster. On the other hand, Streamer head density at onset time of streamer head propagation didn't change. This is considered due to the electric field strength of streamer head at that time, in result, it was about 14 kV/mm under each distance between electrodes.

KELVIN-HELMHOLTZ INSTABILITY OF A CORONAL STREAMER

Energy Technology Data Exchange (ETDEWEB)

Feng, L.; Gan, W. Q. [Key Laboratory of Dark Matter and Space Astronomy, Purple Mountain Observatory, Chinese Academy of Sciences, 210008 Nanjing (China); Inhester, B., E-mail: lfeng@pmo.ac.cn [Max-Planck-Institut fuer Sonnensystemforschung, Max-Planck-Str.2, D-37191 Katlenburg-Lindau (Germany)

2013-09-10

Shear-flow-driven instability can play an important role in energy transfer processes in coronal plasma. We present for the first time the observation of a kink-like oscillation of a streamer that is probably caused by the streaming kink-mode Kelvin-Helmholtz instability (KHI). The wave-like behavior of the streamer was observed by the Large Angle and Spectrometric Coronagraph Experiment C2 and C3 on board the SOlar and Heliospheric Observatory. The observed wave had a period of about 70-80 minutes, and its wavelength increased from 2 R{sub Sun} to 3 R{sub Sun} in about 1.5 hr. The phase speeds of its crests and troughs decreased from 406 {+-} 20 to 356 {+-} 31 km s{sup -1} during the event. Within the same heliocentric range, the wave amplitude also appeared to increase with time. We attribute the phenomena to the MHD KHI, which occurs at a neutral sheet in a fluid wake. The free energy driving the instability is supplied by the sheared flow and sheared magnetic field across the streamer plane. The plasma properties of the local environment of the streamer were estimated from the phase speed and instability threshold criteria.

Positive and negative streamers in ambient air: measuring diameter, velocity and dissipated energy

Energy Technology Data Exchange (ETDEWEB)

Briels, T M P; Kos, J; Van Veldhuizen, E M; Ebert, U [Department of Applied Physics, Technische Universiteit Eindhoven, PO Box 513, 5600 MB Eindhoven (Netherlands); Winands, G J J [Department of Electrical Engineering, Technische Universiteit Eindhoven, PO Box 513, 5600 MB Eindhoven (Netherlands)], E-mail: e.m.v.veldhuizen@tue.nl, E-mail: ebert@cwi.nl

2008-12-07

Positive and negative streamers are studied in ambient air at 1 bar; they emerge from a needle electrode placed 40 mm above a planar electrode. The amplitudes of the applied voltage pulses range from 5 to 96 kV; most pulses have rise times of 30 ns or shorter. Diameters, velocities and energies of the streamers are measured. Two regimes are identified; a low voltage regime where only positive streamers appear and a high voltage regime where both positive and negative streamers exist. Below 5 kV, no streamers emerge. In the range from 5 to 40 kV, positive streamers form, while the negative discharges only form a glowing cloud at the electrode tip, but no streamers. For 5-20 kV, diameters and velocities of the positive streamers have the minimal values of d = 0.2 mm and v {approx} 10{sup 5} m s{sup -1}. For 20-40 kV, their diameters increase by a factor of 6 while the voltage increases only by a factor of 2. Above the transition value of 40 kV, streamers of both polarities form; they strongly resemble each other, though the positive ones propagate further; their diameters continue to increase with applied voltage. For 96 kV, positive streamers attain diameters of 3 mm and velocities of 4 x 10{sup 6} m s{sup -1}; negative streamers are about 20% slower and thinner. An empirical fit formula for the relation between velocity v and diameter d is v = 0.5d{sup 2} mm{sup -1} ns{sup -1} for both polarities. Streamers of both polarities dissipate energies of the order of several millijoules per streamer while crossing the gap.

Study on the streamer inception characteristics under positive lightning impulse voltage

Directory of Open Access Journals (Sweden)

Zezhong Wang

2017-11-01

Full Text Available The streamer is the main process in an air gap discharge, and the inception characteristics of streamers have been widely applied in engineering. Streamer inception characteristics under DC voltage have been studied by many researchers, but the inception characteristics under impulse voltage, and particularly under lightning impulse voltage with a high voltage rise rate have rarely been studied. A measurement system based on integrated optoelectronic technology has been proposed in this paper, and the streamer inception characteristics in a 1-m-long rod-plane air gap that was energized by a positive lightning impulse voltage have been researched. We have also measured the streamer inception electric field using electrodes with different radii of curvature and different voltage rise rates. As a result, a modified empirical criterion for the streamer inception electric field that considers the voltage rise rate has been proposed, and the wide applicability of this criterion has been proved. Based on the streamer inception time-lag obtained, we determined that the field distribution obeys a Rayleigh distribution, which explains the change law of the streamer inception time-lag. The characteristic parameter of the Rayleigh distribution lies in the range from 0.6 to 2.5 when the radius of curvature of the electrode head is in the range from 0.5 cm to 2.5 cm and the voltage rise rate ranges from 80 kV/μs to 240kV/μs under positive lightning impulse voltage.

Study on the streamer inception characteristics under positive lightning impulse voltage

Science.gov (United States)

Wang, Zezhong; Geng, Yinan

2017-11-01

The streamer is the main process in an air gap discharge, and the inception characteristics of streamers have been widely applied in engineering. Streamer inception characteristics under DC voltage have been studied by many researchers, but the inception characteristics under impulse voltage, and particularly under lightning impulse voltage with a high voltage rise rate have rarely been studied. A measurement system based on integrated optoelectronic technology has been proposed in this paper, and the streamer inception characteristics in a 1-m-long rod-plane air gap that was energized by a positive lightning impulse voltage have been researched. We have also measured the streamer inception electric field using electrodes with different radii of curvature and different voltage rise rates. As a result, a modified empirical criterion for the streamer inception electric field that considers the voltage rise rate has been proposed, and the wide applicability of this criterion has been proved. Based on the streamer inception time-lag obtained, we determined that the field distribution obeys a Rayleigh distribution, which explains the change law of the streamer inception time-lag. The characteristic parameter of the Rayleigh distribution lies in the range from 0.6 to 2.5 when the radius of curvature of the electrode head is in the range from 0.5 cm to 2.5 cm and the voltage rise rate ranges from 80 kV/μs to 240kV/μs under positive lightning impulse voltage.

Modeling the plasma chemistry of stratospheric Blue Jet streamers

Science.gov (United States)

Winkler, Holger; Notholt, Justus

2014-05-01

Stratospheric Blue Jets (SBJs) are upward propagating discharges in the altitude range 15-40 km above thunderstorms. The currently most accepted theory associates SBJs to the development of the streamer zone of a leader. The streamers emitted from the leader can travel for a few tens of kilometers predominantly in the vertical direction (Raizer et al., 2007). The strong electric fields at the streamer tips cause ionisation, dissociation, and excitation, and give rise to chemical perturbations. While in recent years the effects of electric discharges occurring in the mesosphere (sprites) have been investigated in a number of model studies, there are only a few studies on the impact of SBJs. However, chemical perturbations due to SBJs are of interest as they might influence the stratospheric ozone layer. We present results of detailed plasma chemistry simulations of SBJ streamers for both day-time and night-time conditions. Any effects of the subsequent leader are not considered. The model accounts for more than 500 reactions and calculates the evolution of the 88 species under the influence of the breakdown electric fields at the streamer tip. As the SBJ dynamics is outside the scope of this study, the streamer parameters are prescribed. For this purpose, electric field parameters based on Raizer et al. (2007) are used. The model is applied to the typical SBJ altitude range 15-40 km. The simulations indicate that SBJ streamers cause significant chemical perturbations. In particular, the liberation of atomic oxygen during the discharge leads to a formation of ozone. At the same time, reactive nitrogen and hydrogen radicals are produced which will cause catalytic ozone destruction. Reference: Raizer et al. (2007), J. Atmos. Solar-Terr. Phys., 69 (8), 925-938.

Probing photo-ionization: experiments on positive streamers in pure gases and mixtures

International Nuclear Information System (INIS)

Nijdam, S; Van de Wetering, F M J H; Blanc, R; Van Veldhuizen, E M; Ebert, U

2010-01-01

Positive streamers are thought to propagate by photo-ionization; the parameters of photo-ionization depend on the nitrogen : oxygen ratio. Therefore we study streamers in nitrogen with 20%, 0.2% and 0.01% oxygen and in pure nitrogen as well as in pure oxygen and argon. Our new experimental set-up guarantees contamination of the pure gases to be well below 1 ppm. Streamers in oxygen are difficult to measure as they emit considerably less light in the sensitivity range of our fast ICCD camera than the other gases. Streamers in pure nitrogen and in all nitrogen-oxygen mixtures look generally similar, but become somewhat thinner and branch more with decreasing oxygen content. In pure nitrogen the streamers can branch so much that they resemble feathers. This feature is even more pronounced in pure argon, with approximately 10 2 hair tips cm -3 in the feathers at 200 mbar; this density can be interpreted as the free electron density creating avalanches towards the streamer stem. It is remarkable that the streamer velocity is essentially the same for similar voltage and pressure in all nitrogen-oxygen mixtures as well as in pure nitrogen, while the oxygen concentration and therefore the photo-ionization lengths vary by more than five orders of magnitude. Streamers in argon have essentially the same velocity as well. The physical similarity of streamers at different pressures is confirmed in all gases; the minimal diameters are smaller than in earlier measurements.

Probing photo-ionization: experiments on positive streamers in pure gases and mixtures

Energy Technology Data Exchange (ETDEWEB)

Nijdam, S; Van de Wetering, F M J H; Blanc, R; Van Veldhuizen, E M; Ebert, U, E-mail: s.nijdam@tue.n [Eindhoven University of Technology, Department Applied Physics, PO Box 513, 5600 MB Eindhoven (Netherlands)

2010-04-14

Positive streamers are thought to propagate by photo-ionization; the parameters of photo-ionization depend on the nitrogen : oxygen ratio. Therefore we study streamers in nitrogen with 20%, 0.2% and 0.01% oxygen and in pure nitrogen as well as in pure oxygen and argon. Our new experimental set-up guarantees contamination of the pure gases to be well below 1 ppm. Streamers in oxygen are difficult to measure as they emit considerably less light in the sensitivity range of our fast ICCD camera than the other gases. Streamers in pure nitrogen and in all nitrogen-oxygen mixtures look generally similar, but become somewhat thinner and branch more with decreasing oxygen content. In pure nitrogen the streamers can branch so much that they resemble feathers. This feature is even more pronounced in pure argon, with approximately 10{sup 2} hair tips cm{sup -3} in the feathers at 200 mbar; this density can be interpreted as the free electron density creating avalanches towards the streamer stem. It is remarkable that the streamer velocity is essentially the same for similar voltage and pressure in all nitrogen-oxygen mixtures as well as in pure nitrogen, while the oxygen concentration and therefore the photo-ionization lengths vary by more than five orders of magnitude. Streamers in argon have essentially the same velocity as well. The physical similarity of streamers at different pressures is confirmed in all gases; the minimal diameters are smaller than in earlier measurements.

Streamer properties and associated x-rays in perturbed air

DEFF Research Database (Denmark)

Köhn, C; Chanrion, O; Babich, L P

2018-01-01

Streamers are ionization waves in electric discharges. One of the key ingredients of streamerpropagation is an ambient gas that serves as a source of free electrons. Here, we explore thedependence of streamer dynamics on different spatial distributions of ambient air molecules. We varythe spatial...... profile of air parallel and perpendicular to the ambient electric field. We consider localsinusoidal perturbations of 5%–100%, as induced from discharge shock waves. We use acylindrically symmetric particle-in-cell code to simulate the evolution of bidirectional streamers andcompare the electron density...

Runaway electrons from a ‘beam-bulk’ model of streamer: application to TGFs

DEFF Research Database (Denmark)

Chanrion, Olivier Arnaud; Bonaventura, Z.; Cinar, Deniz

2014-01-01

-energy electrons and ions. For a negative streamer discharge, we show how electrons are accelerated in the large electric field in the tip of the streamer and travel ahead of the streamer where they ionize the gas. In comparison to the results obtained with a classical fluid model for a negative streamer, the beam...

Influence of Auroral Streamers on Rapid Evolution of Ionospheric SAPS Flows

Science.gov (United States)

Gallardo-Lacourt, Bea; Nishimura, Y.; Lyons, L. R.; Mishin, E. V.; Ruohoniemi, J. M.; Donovan, E. F.; Angelopoulos, V.; Nishitani, N.

2017-12-01

Subauroral polarization streams (SAPS) often show large, rapid enhancements above their slowly varying component. We present simultaneous observations from ground-based all-sky imagers and flows from the Super Dual Auroral Radar Network radars to investigate the relationship between auroral phenomena and flow enhancement. We first identified auroral streamers approaching the equatorward boundary of the auroral oval to examine how often the subauroral flow increased. We also performed the reverse query starting with subauroral flow enhancements and then evaluated the auroral conditions. In the forward study, 98% of the streamers approaching the equatorward boundary were associated with SAPS flow enhancements reaching 700 m/s and typically hundreds of m/s above background speeds. The reverse study reveals that flow enhancements associated with streamers (60%) and enhanced larger-scale convection (37%) contribute to SAPS flow enhancements. The strong correlation of auroral streamers with rapid evolution (approximately minutes) of SAPS flows suggests that transient fast earthward plasma sheet flows can often lead to westward SAPS flow enhancements in the subauroral region and that such enhancements are far more common than only during substorms because of the much more frequent occurrences of streamers under various geomagnetic conditions. We also found a strong correlation between flow duration and streamer duration and a weak correlation between SAPS flow velocity and streamer intensity. This result suggests that intense flow bursts in the plasma sheet (which correlate with intense streamers) are associated with intense SAPS ionospheric flows perhaps by enhancing the ring current pressure and localized pressure gradients when they are able to penetrate close enough to Earth.

First joint test beam of CMS Drift Tubes (DT) and Resistive Plate Chambers (RPC)

CERN Multimedia

Paolo Giacomelli

2001-01-01

The first full size muon drift tube chamber ever built for the CMS barrel with the final cell design (constructed at CIEMAT, Madrid) was succesfully tested with a muon beam in September 2001 at the Gamma Irradiation Facility (GIF) at CERN. For the first time also both muon detectors for the CMS barrel (DT + RPC) were coupled together. The results of this test were fully succesful and confirmed the excellent performance of both detectors together in a radiation environment.

Streamer discharges can move perpendicularly to the electric field

NARCIS (Netherlands)

Nijdam, S.; Takahashi, E.; Teunissen, J.; Ebert, U.

2014-01-01

Streamer discharges are a primary mode of electric breakdown in thunderstorms and high voltage technology; they are generally believed to grow along electric field lines. However, we here give experimental and numerical evidence that streamers can propagate nearly perpendicularly to the background

An adaptive grid refinement strategy for the simulation of negative streamers

International Nuclear Information System (INIS)

Montijn, C.; Hundsdorfer, W.; Ebert, U.

2006-01-01

The evolution of negative streamers during electric breakdown of a non-attaching gas can be described by a two-fluid model for electrons and positive ions. It consists of continuity equations for the charged particles including drift, diffusion and reaction in the local electric field, coupled to the Poisson equation for the electric potential. The model generates field enhancement and steep propagating ionization fronts at the tip of growing ionized filaments. An adaptive grid refinement method for the simulation of these structures is presented. It uses finite volume spatial discretizations and explicit time stepping, which allows the decoupling of the grids for the continuity equations from those for the Poisson equation. Standard refinement methods in which the refinement criterion is based on local error monitors fail due to the pulled character of the streamer front that propagates into a linearly unstable state. We present a refinement method which deals with all these features. Tests on one-dimensional streamer fronts as well as on three-dimensional streamers with cylindrical symmetry (hence effectively 2D for numerical purposes) are carried out successfully. Results on fine grids are presented, they show that such an adaptive grid method is needed to capture the streamer characteristics well. This refinement strategy enables us to adequately compute negative streamers in pure gases in the parameter regime where a physical instability appears: branching streamers

Surface streamer propagations on an alumina bead: experimental observation and numerical modeling

Science.gov (United States)

Kang, Woo Seok; Kim, Hyun-Ha; Teramoto, Yoshiyuki; Ogata, Atsushi; Lee, Jin Young; Kim, Dae-Woong; Hur, Min; Song, Young-Hoon

2018-01-01

A surface streamer in a simplified packed-bed reactor has been studied both experimentally (through time-resolved ICCD imaging) and theoretically (through two-dimensional numerical modeling). The propagation of streamers on an alumina spherical bead without catalytic coating shows three distinct phases—the generation and propagation of a primary streamer (PS) with a moderate velocity and electric field, fast PS acceleration with an enhanced electric field, and slow secondary streamer (SS) propagation. The velocity of the streamer is less than that of propagation in a gaseous media. The electric field and velocity at the streamer front are maximized when a PS propagates during the interval from the midpoint of the bead to the bottom electrode. The SS exhibits a much lower velocity and electric field compared with the PS. The PS velocity is affected by an external applied voltage, especially when it approaches the ground electrode. However, that of the SS remains constant regardless of the voltage change. The simulation shows that the PS exhibits a high electric field mainly created by the space charge induced by electrons, whereas the SS relies on ion movement with electron decay in a charge-filled thin streamer body.

Factors determining the choice of the beam tube material and the vacuum chamber design for a superconducting high energy storage accelerator

International Nuclear Information System (INIS)

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

1979-01-01

The factors which determine the choice of the material and the basic design for the vacuum chamber of the ISABELLE Colliding Storage Accelerator are reviewed. When the physical, thermal, electrical, and mechanical properties of the bulk material, as well as the various surface characteristics, are considered, it appears that a stainless tube covered with a copper sleeve is the best choice for the chambers in the magnet lattice of the rings. Aluminum is probably the most desirable material for those chambers in the experimental straight sections

2d axisymmetric "beam-bulk" modelling of the generation of runaway electrons by streamers.

Science.gov (United States)

Chanrion, Olivier; Bonaventura, Zdenek; Bourdon, Anne; Neubert, Torsten

2017-04-01

We present results from a 2d axisymmetric numerical model of streamers based on a "beam-bulk" approach which describes cold electrons with a fluid model and high energy electrons with a particle model. The interest is motivated by the generation of runaway electrons by streamers which may participate in the recently observed TGFs and which challenge the modelling. Runaway electrons are known to be generated from streamers when the electric field in its negative tip is of sufficient magnitude. After overtaking the streamer tip, runaways can affect the streamer propagation ahead and may produce high energy photons through the bremsstrahlung process. In conventional model of streamers, the evolution of the streamer discharge is mostly governed by cold electrons. By including runaway electrons, we model their production, their impact on the discharge propagation and can address their role in TGFs. Results of streamer propagation in leader electric field show that the runaway electrons accelerate the streamers, reduce the electric field in its tip and enlarge its radius by pre-ionizing the gas ahead. We observed that if we increase the electric field, the discharge is getting more diffuse, with a pattern driven by the increase in runaway induced ionisation.

Stereo-photography of streamers in air

International Nuclear Information System (INIS)

Nijdam, S.; Moerman, J. S.; Briels, T. M. P.; Veldhuizen, E. M. van; Ebert, U.

2008-01-01

Standard photographs of streamer discharges show a two-dimensional projection. Here, we present stereophotographic images that resolve their three-dimensional structure. We describe the stereoscopic setup and evaluation, and we present results for positive streamer discharges in air at 0.2-1 bar in a point-plane geometry with a gap distance of 14 cm and a voltage pulse of 47 kV. In this case, an approximately Gaussian distribution of branching angles of 43 deg. ±12 deg. is found; these angles do not significantly depend on the distance from the needle or on the gas pressure

Auroral streamers: characteristics of associated precipitation,convection and field-aligned currents

Directory of Open Access Journals (Sweden)

V. A. Sergeev

2004-01-01

Full Text Available During the long-duration steady convection activity on 11 December 1998, the development of a few dozen auroral streamers was monitored by Polar UVI instrument in the dark northern nightside ionosphere. On many occasions the DMSP spacecraft crossed the streamer-conjugate regions over the sunlit southern auroral oval, permitting the investigation of the characteristics of ion and electron precipitation, ionospheric convection and field-aligned currents associated with the streamers. We confirm the conjugacy of streamer-associated precipitation, as well as their association with ionospheric plasma streams having a substantial equatorward convection component. The observations display two basic types of streamer-associated precipitation. In its polewardmost half, the streamer-associated (field-aligned accelerated electron precipitation coincides with the strong (≥2–7μA/m² upward field-aligned currents on the westward flank of the convection stream, sometimes accompanied by enhanced proton precipitation in the adjacent region. In the equatorward portion of the streamer, the enhanced precipitation includes both electrons and protons, often without indication of field-aligned acceleration. Most of these characteristics are consistent with the model describing the generation of the streamer by the narrow plasma bubbles (bursty bulk flows which are contained on dipolarized field lines in the plasma sheet, although the mapping is strongly distorted which makes it difficult to quantitatively interprete the ionospheric image. The convective streams in the ionosphere, when well-resolved, had the maximal convection speeds ∼0.5–1km/s, total field-aligned currents of a few tenths of MA, thicknesses of a few hundreds km and a potential drop of a few kV across the stream. However, this might represent only a small part of the associated flux transport in the equatorial plasma sheet.

Key words. Ionosphere (electric fiels and

A novel pulsed corona discharge reactor based on surface streamers for diesel exhaust remediation

Energy Technology Data Exchange (ETDEWEB)

Malik, M.A.; Schoenbach, K.H. [Old Dominion Univ., Norfolk, VA (United States). Frank Reidy Research Center for Bioelectrics

2010-07-01

Modelling of surface streamers along insulating surfaces to determine the dielectric strength of insulators in high voltage systems has shown that surface streamers consist of a positive streamer head followed by quasi-neutral plasma in the channel behind and surrounded by a layer of positive charges. This paper described a novel pulsed corona discharge reactor which utilized such surface streamers along insulating surfaces. The electrodes were comprised of a stainless steel wire anode of 150 mm in diameter stretched along the surface of a glass sheet and two parallel aluminum strips as cathodes. An eight-stage Marx bank, was used to produce the surface streamers in nitrogen-oxygen mixtures at atmospheric pressure. The paper described the experimental study with particular reference to the schematics of a surface streamer plasma reactor and the dimensions of discharge spaces of three reactors. The purpose of the study was to find the optimum conditions for energy yield and effective destruction of nitrogen oxides from diesel engine exhaust. It was concluded that surface streamers generate a more diffuse plasma. Energy costs for production of ozone or nitrogen dioxide that require reactions with bulk gas molecules were nearly the same in surface streamer discharges as in volume streamer discharges. 12 refs., 1 tab., 7 figs.

Analyses of electron runaway in front of the negative streamer channel

Science.gov (United States)

Babich, L. P.; Bochkov, E. I.; Kutsyk, I. M.; Neubert, T.; Chanrion, O.

2017-08-01

X-ray and γ-ray emissions, observed in correlation with negative leaders of lightning and long sparks of high-voltage laboratory experiments, are conventionally connected with the bremsstrahlung of high-energy runaway electrons (REs). Here we extend a focusing mechanism, analyzed in our previous paper, which allows the electric field to reach magnitudes, required for a generation of significant RE fluxes and associated bremsstrahlung, when the ionization wave propagates in a narrow, ionized channel created by a previous streamer. Under such conditions we compute the production rate of REs per unit streamer length as a function of the streamer velocity and predict that, once a streamer is formed with the electric field capable of producing REs ahead of the streamer front, the ionization induced by the REs is capable of creating an ionized channel that allows for self-sustained propagation of the RE-emitting ionization wave independent of the initial electron concentration. Thus, the streamer coronas of the leaders are probable sources of REs producing the observed high-energy radiation. To prove these predictions, new simulations are planned, which would show explicitly that the preionization in front of the channel via REs will lead to the ionization wave propagation self-consistent with RE generation.

A track chamber with controlled heat centres as a vertex detector for very high energy physics experiments

International Nuclear Information System (INIS)

Shcherbakov, Yu.A.

1989-01-01

A high-pressure vertex detector for high energy experiments is proposed on the basis of development of a new track detector of charged particles, which is a chamber with controlled centres. A possible design of this chamber is discussed. Laser illumination of a streamer chamber allows enough light for reading the information by means of a CCD device. Some characteristics of the set-up are considered in the paper. A possibility of using a new method for suppression of diffusion is discussed. 30 refs.; 7 figs.; 3 tabs

Evaluation of pulsed streamer corona experiments to determine the O* radical yield

International Nuclear Information System (INIS)

Van Heesch, E J M; Winands, G J J; Pemen, A J M

2008-01-01

The production of O* radicals in air by a pulsed streamer plasma is studied by integration of a large set of precise experimental data and the chemical kinetics of ozone production. The measured data comprise ozone production, plasma energy, streamer volume, streamer length, streamer velocity, humidity and gas-flow rate. Instead of entering input parameters into a kinetic model to calculate the end products the opposite strategy is followed. Since the amount of end-products (ozone) is known from the measurements the model had to be applied in the reverse direction to determine the input parameters, i.e. the O* radical concentration.

Evaluation of pulsed streamer corona experiments to determine the O* radical yield

Science.gov (United States)

van Heesch, E. J. M.; Winands, G. J. J.; Pemen, A. J. M.

2008-12-01

The production of O* radicals in air by a pulsed streamer plasma is studied by integration of a large set of precise experimental data and the chemical kinetics of ozone production. The measured data comprise ozone production, plasma energy, streamer volume, streamer length, streamer velocity, humidity and gas-flow rate. Instead of entering input parameters into a kinetic model to calculate the end products the opposite strategy is followed. Since the amount of end-products (ozone) is known from the measurements the model had to be applied in the reverse direction to determine the input parameters, i.e. the O* radical concentration.

On increasing the efficiency of a streamer semiconductor laser

International Nuclear Information System (INIS)

Rusakov, K I; Parashchuk, V V

2007-01-01

The influence of intense electric and optical fields produced by a streamer discharge in wide-gap semiconductors on their spectroscopic properties is studied. The effect is manifested in the reversible change of the luminescence parameters of the active medium. Methods are proposed for increasing the service life and efficiency of a streamer laser in limiting regimes, which are based on the use of semiconductor protective layers of a certain crystallographic orientation and a crystal microrelief with the size of elements of the order of the wavelength of light. Streamer emission was observed and studied in new promising Eu:CaGa 2 S 4 and Eu:Ca 4 Ga 2 S 7 materials. (lasers)

Computational Studies of Positive and Negative Streamers in Bubbles Suspended in Distilled Water

KAUST Repository

Sharma, Ashish

2017-01-05

We perform computational studies of nanosecond streamers generated in helium bubbles immersed in distilled water under high pressure conditions. The model takes into account the presence of water vapor in the gas bubble for an accurate description of the chemical kinetics of the discharge. We apply positive and negative trigger voltages much higher than the breakdown voltage and study the dynamic characteristics of the resulting discharge. We observe that, for high positive trigger voltages, the streamer moves along the surface of the gas bubble during the initial stages of the discharge. We also find a considerable difference in the evolution of the streamer discharge for positive and negative trigger voltages with more uniform volumetric distribution of species in the streamer channel for negative trigger voltages due to formation of multiple streamers. We also observe that the presence of water vapor does not influence the breakdown voltage of the discharge but greatly affects the composition of dominant species in the trail of the streamer channel.

Numerical Analysis of Flow Distribution in a Sodium Chamber of a Finned-tube Sodium-to-Air Heat Exchanger

Energy Technology Data Exchange (ETDEWEB)

Jo, Youngchul; Son, Seokkwon; Kim, Hyungmo; Eoh, Jaehyuk; Jeong, Jiyoung [Korea Atomic Energy Research Institute, Daejeon (Korea, Republic of)

2015-10-15

DHR systems consist of two diverse heat removal loops such as passive and active DHR systems, and the heat load imposed on the primary sodium pool is safely rejected into the environment through different kinds of sodium-to-air heat exchangers, e.g. M-shape and helical-coil type air-coolers. The former is called as an FHX(Forced-draft sodium-to-air Heat Exchanger) and the latter is simply called as an AHX(natural-draft sodium-to-Air Heat Exchanger). In a general sodium-to-air heat exchanger design, convection resistance in a shell-side air flow path becomes dominant factor affecting the mechanism of conjugate heat transfer from the sodium flow inside the tube to the air path across the sodium tube wall. Hence verification of the flow and heat transfer characteristics is one of the most important tasks to demonstrate decay heat removal performance. To confirm a kind of ultimate heat sink heat exchanger, a medium-scale Sodium thermal-hydraulic Experiment Loop for Finned-tube sodium-to-Air Heat exchanger (here after called the SELFA) has been designed and is recently being constructed at KAERI site. The introduction of the flow baffle inside the upper sodium chamber of the model FHX unit in the SELFA facility is briefly proposed and discussed as well. The present study aims at introducing a flow baffle design inside the upper sodium chamber to make more equalized flowrates flowing into each heat transfer tube of the model FHX unit. In the cases without the flow baffle geometry, it was observed lager discrepancies in flowrates at the heat transfer tubes. However it was also found that those kinds of discrepancies could be definitely decreased at around 1/10 by employing a flow baffle.

Characterizing the active opening of the eustachian tube in a hypobaric/hyperbaric pressure chamber.

Science.gov (United States)

Mikolajczak, Stefanie; Meyer, Moritz Friedo; Hahn, Moritz; Korthäuer, Christine; Jumah, Masen Dirk; Hüttenbrink, Karl-Bernd; Grosheva, Maria; Luers, Jan Christoffer; Beutner, Dirk

2015-01-01

Active and passive opening of the Eustachian tube (ET) enables direct aeration of the middle ear and a pressure balance between middle ear and the ambient pressure. The aim of this study was to characterize standard values for the opening pressure (ETOP), the opening frequency (ETOF), and the opening duration (ETOD) for active tubal openings (Valsalva maneuver, swallowing) in healthy participants. In a hypobaric/hyperbaric pressure chamber, 30 healthy participants (19 women, 11 men; mean age, 25.57 ± 3.33 years) were exposed to a standardized profile of compression and decompression. The pressure values were recorded via continuous impedance measurement during the Valsalva maneuver and swallowing. Based on the data, standard curves were identified and the ETOP, ETOD, and ETOF were determined. Recurring patterns of the pressure curve during active tube opening for the Valsalva maneuver and for active swallowing were characterized. The mean value for the Valsalva maneuver for ETOP was 41.21 ± 17.38 mbar; for the ETOD, it was 2.65 ± 1.87 seconds. In the active pressure compensation by swallowing, the mean value for the ETOP was 29.91 ± 13.07 mbar; and for the ETOD, it was 0.82 ± 0.53 seconds. Standard values for the opening pressure of the tube and the tube opening duration for active tubal openings (Valsalva maneuver, swallowing) were described, and typical curve gradients for healthy subjects could be shown. This is another step toward analyzing the function of the tube in compression and decompression.

Photoionization in negative streamers : fast computations and two propagation modes

NARCIS (Netherlands)

Luque, A.; Ebert, U.M.; Montijn, C.; Hundsdorfer, W.

2007-01-01

Streamer discharges play a central role in electric breakdown of matter in pulsed electric fields, both in nature and in technology. Reliable and fast computations of the minimal model for negative streamers in simple gases such as nitrogen have recently been developed. However, photoionization was

A study of gas mixtures for the ATLAS MDT

International Nuclear Information System (INIS)

Zhao, T.; He, L.

1996-01-01

Results of a gas study for the ATLAS Monitored Drift Tubes (MDT) are reported. The electron drift velocity, Lorentz angle and tube radius to drift time relations are calculated for selected gas mixtures by using the CERN drift chamber simulation code GARFIELD/MAGBOLTZ. The drift tube efficiency, gas gain, avalanche size and self-quenching streamer (SQS) mode fraction as functions of anode voltage are measured by using radioactive sources. Discussions of the results, including effects of nitrogen and water vapor, are presented

Positive streamers in air and nitrogen of varying density: experiments on similarity laws

International Nuclear Information System (INIS)

Briels, T M P; Van Veldhuizen, E M; Ebert, U

2008-01-01

Positive streamers in ambient air at pressures from 0.013 to 1 bar are investigated experimentally. The voltage applied to the anode needle ranges from 5 to 45 kV, the discharge gap from 1 to 16 cm. Using a 'slow' voltage rise time of 100-180 ns, the streamers are intentionally kept thin. For each pressure p, we find a minimal diameter d min . To test whether streamers at different pressures are similar, the minimal streamer diameter d min is multiplied by its pressure p; we find this product to be well approximated by p · d min = 0.20 ± 0.02 mm bar over two decades of air pressure at room temperature. The value also fits diameters of sprite discharges above thunderclouds at an altitude of 80 km when extrapolated to room temperature (as air density rather than pressure determines the physical behaviour). The minimal velocity of streamers in our measurements is approximately 0.1 mm ns -1 = 10 5 m s -1 . The same minimal velocity has been reported for tendrils in sprites. We also investigate the size of the initial ionization cloud at the electrode tip from which the streamers emerge, and the streamer length between branching events. The same quantities are also measured in nitrogen with a purity of approximately 99.9%. We characterize the essential differences with streamers in air and find a minimal diameter of p · d min = 0.12 ± 0.02 mm bar in our nitrogen.

Parallel sparse direct solvers for Poisson's equation in streamer discharges

NARCIS (Netherlands)

M. Nool (Margreet); M. Genseberger (Menno); U. M. Ebert (Ute)

2017-01-01

textabstractThe aim of this paper is to examine whether a hybrid approach of parallel computing, a combination of the message passing model (MPI) with the threads model (OpenMP) can deliver good performance in streamer discharge simulations. Since one of the bottlenecks of almost all streamer

Influences of the pulsed power supply on corona streamer appearance

NARCIS (Netherlands)

Veldhuizen, van E.M.; Briels, T.M.P.; Grabowski, L.R.; Pemen, A.J.M.; Ebert, U.M.

2005-01-01

Pulsed positive corona streamers in air are studied by images obtained with an intensified CCD camera. Using a switched capacitor power supply, thin streamers are observed that branch. A power supply consisting of a 4-stage transmission line transformer gives pulses of much higher current to the

Multisource waveform inversion of marine streamer data using normalized wavefield

KAUST Repository

Choi, Yun Seok

2013-09-01

Multisource full-waveform inversion based on the L1- and L2-norm objective functions cannot be applied to marine streamer data because it does not take into account the unmatched acquisition geometries between the observed and modeled data. To apply multisource full-waveform inversion to marine streamer data, we construct the L1- and L2-norm objective functions using the normalized wavefield. The new residual seismograms obtained from the L1- and L2-norms using the normalized wavefield mitigate the problem of unmatched acquisition geometries, which enables multisource full-waveform inversion to work with marine streamer data. In the new approaches using the normalized wavefield, we used the back-propagation algorithm based on the adjoint-state technique to efficiently calculate the gradients of the objective functions. Numerical examples showed that multisource full-waveform inversion using the normalized wavefield yields much better convergence for marine streamer data than conventional approaches. © 2013 Society of Exploration Geophysicists.

Two-Dimensional Electron Density Measurement of Positive Streamer Discharge in Atmospheric-Pressure Air

Science.gov (United States)

Inada, Yuki; Ono, Ryo; Kumada, Akiko; Hidaka, Kunihiko; Maeyama, Mitsuaki

2016-09-01

The electron density of streamer discharges propagating in atmospheric-pressure air is crucially important for systematic understanding of the production mechanisms of reactive species utilized in wide ranging applications such as medical treatment, plasma-assisted ignition and combustion, ozone production and environmental pollutant processing. However, electron density measurement during the propagation of the atmospheric-pressure streamers is extremely difficult by using the conventional localized type measurement systems due to the streamer initiation jitters and the irreproducibility in the discharge paths. In order to overcome the difficulties, single-shot two-dimensional electron density measurement was conducted by using a Shack-Hartmann type laser wavefront sensor. The Shack-Hartmann sensor with a temporal resolution of 2 ns was applied to pulsed positive streamer discharges generated in an air gap between pin-to-plate electrodes. The electron density a few ns after the streamer initiation was 7*1021m-3 and uniformly distributed along the streamer channel. The electron density and its distribution profile were compared with a previous study simulating similar streamers, demonstrating good agreement. This work was supported in part by JKA and its promotion funds from KEIRIN RACE. The authors like to thank Mr. Kazuaki Ogura and Mr. Kaiho Aono of The University of Tokyo for their support during this work.

A study of Ks0, Λ and anti Λ production in 60 and 200 GeV per nucleon OAu and pAu collisions with a streamer chamber detector at the CERN SPS

International Nuclear Information System (INIS)

Bamberger, A.; Runge, K.; Bialkowska, H.; Bock, R.; Brockmann, R.; Guerra, C.; Humanic, T.; Sandoval, A.; Chase, S.I.; Harris, J.W.; Odyniec, G.; Pugh, H.G.; Rai, G.; Rauch, W.; Schroeder, L.S.; Tincknell, M.; Teitelbaum, L.; Tonse, S.; De Marzo, C.; De Palma, M.; Favuzzi, C.; Nappi, E.; Posa, F.; Ranieri, A.; Spinelli, P.; Derado, I.; Eckardt, V.; Fessler, H.; Freund, P.; Gebauer, H.J.; Pretzl, K.P.; Schmitz, N.; Schouten, T.; Seyboth, P.; Seyerlein, J.; Vesztergombi, G.; Ferenc, D.; Vranic, D.; Gazdzicki, M.; Heck, W.; Lahanas, M.; Margetis, S.; Pfennig, J.; Renfordt, R.; Roehrich, D.; Stock, R.; Stroebele, H.; Thomas, A.; Wenig, S.; Karabarbounis, A.; Petridis, A.; Panagiotou, A.D.; Skrzypczak, E.

1989-01-01

The production of neutral strange particles K s 0 , Λ and anti Λ has been studied in 60 and 200 GeV per nucleon OAu and pAu collisions with the streamer chamber vertex spectrometer of the NA35 experiment at the CERN-SPS accelerator. Ratios of neutral strange particle production to negatively charged particle production in selected regions of phase space were measured to be the same in OAu and pAu reactions. The rates of strange particle production in central OAu collisions are about a factor of 16 higher than in pAu collisions when compared in the same regions of phase space. If an enhancement of strange particle production in OAu collisions relative to pAu collisions is considered to be a signature for quark-gluon plasma formation, no evidence supporting it is observed. The experimental results are compared to the Lund FRITIOF model. (orig.)

Fractal multiplication of electron avalanches and streamers: new mechanism of electrical breakdown?

International Nuclear Information System (INIS)

Ficker, T

2007-01-01

Long-lasting problems concerning peculiar statistical behaviour of high populated electron avalanches have been analysed. These avalanches are precursors of streamer breakdown in gases. The present streamer theory fails in explaining severe systematic deviations from the Furry statistics that is believed to be a governing statistical law. Such a deviated behaviour of high populated avalanches seems to be a consequence of a special pre-breakdown mechanism that is rather different from that known so far in discharge physics. This analysis tends towards formulating a modified theoretical concept supplementing the streamer theory by a new statistical view of pre-streamer states. The correctness of the concept is corroborated by a series of experiments

Positive streamers in air and nitrogen of varying density: experiments on similarity laws

Energy Technology Data Exchange (ETDEWEB)

Briels, T M P; Van Veldhuizen, E M; Ebert, U [Department of Applied Physics, Technische Universiteit Eindhoven, P O Box 513, 5600 MB Eindhoven (Netherlands)], E-mail: ebert@cwi.nl, E-mail: e.m.v.veldhuizen@tue.nl

2008-12-07

Positive streamers in ambient air at pressures from 0.013 to 1 bar are investigated experimentally. The voltage applied to the anode needle ranges from 5 to 45 kV, the discharge gap from 1 to 16 cm. Using a 'slow' voltage rise time of 100-180 ns, the streamers are intentionally kept thin. For each pressure p, we find a minimal diameter d{sub min}. To test whether streamers at different pressures are similar, the minimal streamer diameter d{sub min} is multiplied by its pressure p; we find this product to be well approximated by p {center_dot} d{sub min} = 0.20 {+-} 0.02 mm bar over two decades of air pressure at room temperature. The value also fits diameters of sprite discharges above thunderclouds at an altitude of 80 km when extrapolated to room temperature (as air density rather than pressure determines the physical behaviour). The minimal velocity of streamers in our measurements is approximately 0.1 mm ns{sup -1} = 10{sup 5} m s{sup -1}. The same minimal velocity has been reported for tendrils in sprites. We also investigate the size of the initial ionization cloud at the electrode tip from which the streamers emerge, and the streamer length between branching events. The same quantities are also measured in nitrogen with a purity of approximately 99.9%. We characterize the essential differences with streamers in air and find a minimal diameter of p {center_dot} d{sub min} = 0.12 {+-} 0.02 mm bar in our nitrogen.

Vertex chamber for the KEDR detector

International Nuclear Information System (INIS)

Aulchenko, V.M.; Chilingarov, A.G.; Kolachev, G.M.; Lazarenko, O.B.; Nagaslaev, V.P.; Romanov, L.V.

1989-01-01

The project and design of the vertex chamber for the KEDR detector is described. The chamber consists of 6 cylindrical layers of tubes with 10 mm diameter and 800 mm length. The tubes are made of 20 μm thick aluminized mylar. The prototype tests show that it is possible to achieve a resolution of 20-30 μm using the cool gas mixtures. (orig.)

Streamers and their applications

Science.gov (United States)

Pemen, A. J. M.

2011-10-01

In this invited lecture we give an overview of our 15 years of experience on streamer plasma research. Efforts are directed to integrating the competence areas of plasma physics, pulsed power technology and chemical processing. The current status is the development of a large scale pulsed corona system for gas treatment. Applications on biogas conditioning, VOC removal, odor abatement and control of traffic emissions have been demonstrated. Detailed research on electrical and chemical processes resulted in a boost of efficiencies. Energy transfer efficiency to the plasma was raised to above 90%. Simultaneous improvement of the plasma chemistry resulted in a highly efficient radical generation: O-radical production up to 50% of the theoretical maximum has been achieved. A major challenge in pulsed power driven streamers is to unravel, understand and ultimately control the complex interactions between the transient plasma, electrical circuits, and process. Even more a challenge is to yield electron energies that fit activation energies of the process. We will discuss our ideas on adjusting pulsed power waveforms and plasma reactor settings to obtain more controlled catalytic processing: the ``Chemical Transistor'' concept.

An Atlantic streamer in stratospheric ozone observations and SD-WACCM simulation data

Science.gov (United States)

Hocke, Klemens; Schranz, Franziska; Maillard Barras, Eliane; Moreira, Lorena; Kämpfer, Niklaus

2017-03-01

Observation and simulation of individual ozone streamers are important for the description and understanding of non-linear transport processes in the middle atmosphere. A sudden increase in mid-stratospheric ozone occurred above central Europe on 4 December 2015. The GROund-based Millimeter-wave Ozone Spectrometer (GROMOS) and the Stratospheric Ozone MOnitoring RAdiometer (SOMORA) in Switzerland measured an ozone enhancement of about 30 % at 34 km altitude (8.3 hPa) from 1 to 4 December. A similar ozone increase is simulated by the Specified Dynamics Whole Atmosphere Community Climate (SD-WACCM) model. Further, the global ozone fields at 34 km altitude (8.3 hPa) from SD-WACCM and the satellite experiment Aura/MLS show a remarkable agreement for the location and timing of an ozone streamer (large-scale tongue-like structure) extending from the subtropics in northern America over the Atlantic to central Europe. This agreement indicates that SD-WACCM can inform us about the wind inside the Atlantic ozone streamer. SD-WACCM shows an eastward wind of about 100 m s-1 inside the Atlantic streamer in the mid-stratosphere. SD-WACCM shows that the Atlantic streamer flows along the edge of the polar vortex. The Atlantic streamer turns southward at an erosion region of the polar vortex located above the Caspian Sea. The spatial distribution of stratospheric water vapour indicates a filament outgoing from this erosion region. The Atlantic streamer, the polar vortex erosion region and the water vapour filament belong to the process of planetary wave breaking in the so-called surf zone of the northern midlatitude winter stratosphere.

A new gaseous detector for tracking: The blade chamber

International Nuclear Information System (INIS)

Ambrosi, G.; Battiston, R.; Levi, G.; Barillari, T.; Susinno, G.; Bergsma, F.; Contin, A.; Labbe, J.C.; Laurenti, G.; Mattern, D.; Simonet, G.; Williams, M.C.S.; Zichichi, A.; Boscherini, D.; Bruni, G.; De Pasquale, S.; Giusti, P.; Maccarrone, G.; Nania, R.; O'Shea, V.; Castro, H.; Galvez, J.; Rivera, F.; Schioppa, M.; Sharma, A.

1990-01-01

As part of the LAA project at CERN a prototype of a streamer-chamber in which a blade, instead of a wire, is used as the amplification electrode has been built. A big advantage is that the blade can be bent to follow a curve so that a chamber can be built with cells ideally matched to the geometry of the experiment. Moreover, a blade is very rugged, it can withstand severe mechanical shocks and it is also resistant to damage by sparks. The drift time has been measured and a spatial resolution of 250μm has been achieved. Left-right ambiguity can be solved by measuring the charge asymmetry on the walls. The coordinate along the blade is read by external pickup strips. (orig.)

The dynamics of streamer formation and its growth mechanism

International Nuclear Information System (INIS)

Zalikhanov, B.Zh.

2004-01-01

We report the results of experimental studies of physical processes responsible for the transformation of the electron avalanche to the streamer and its growth towards the cathode. The new experimental data on the mechanism of formation and the structure of the streamer allow a more concrete understanding of the pattern of evolution of long spark discharges, including the lightning, and the interrelation of basic processes in such discharges. (author)

Preparation of water-soluble carbon nanotubes using a pulsed streamer discharge in water

International Nuclear Information System (INIS)

Imasaka, Kiminobu; Suehiro, Junya; Kanatake, Yusuke; Kato, Yuki; Hara, Masanori

2006-01-01

A novel technique for the preparation of water-soluble carbon nanotubes was demonstrated using a pulsed streamer discharge generated in water. The technique involved chemical reactions between radicals generated by the pulsed streamer discharge and carbon nanotubes. The pulsed streamer-treated carbon nanotubes were homogeneously dispersed and well solubilized in water for a month or longer. The mechanism of solubilization of carbon nanotubes by the pulsed streamer discharge is discussed based on FTIR spectroscopy and optical emission spectra measurements. FTIR spectroscopy revealed that -OH groups, which are known to impart a hydrophilic nature to carbon material, were introduced on the carbon nanotube surface. Optical emission spectra from the pulsed streamer plasma showed that highly oxidative O * and H * radicals were generated in water. These results suggest that the functionalization of the carbon nanotube surface by -OH group can be attributed to the O * and H * radicals. An advantage of the proposed method is that there is no need for any chemical agents or additives for solubilization. Chemical agents for solubilization are generated from the water itself by the electrochemical reactions induced by the pulsed streamer discharge

Streamer model for high voltage water switches

International Nuclear Information System (INIS)

Sazama, F.J.; Kenyon, V.L. III

1979-01-01

An electrical switch model for high voltage water switches has been developed which predicts streamer-switching effects that correlate well with water-switch data from Casino over the past four years and with switch data from recent Aurora/AMP experiments. Preclosure rounding and postclosure resistive damping of pulseforming line voltage waveforms are explained in terms of spatially-extensive, capacitive-coupling of the conducting streamers as they propagate across the gap and in terms of time-dependent streamer resistance and inductance. The arc resistance of the Casino water switch and of a gas switch under test on Casino was determined by computer fit to be 0.5 +- 0.1 ohms and 0.3 +- 0.06 ohms respectively, during the time of peak current in the power pulse. Energy lost in the water switch during the first pulse is 18% of that stored in the pulseforming line while similar energy lost in the gas switch is 11%. The model is described, computer transient analyses are compared with observed water and gas switch data and the results - switch resistance, inductance and energy loss during the primary power pulse - are presented

Upgrades of the ATLAS Muon Spectrometer with sMDT Chambers

CERN Document Server

Ferretti, Claudio; The ATLAS collaboration

2015-01-01

With half the drift-tube diameter of the Monitored Drift Tube (MDT) chambers of the ATLAS muon spectrometer and otherwise unchanged operating parameters, small-diameter Muon Drift Tube (sMDT) chambers provide an order of magnitude higher rate capability and can be installed in detector regions where MDT chambers do not fit. The chamber assembly time has been reduced by a factor of seven to one working day and the sense wire positioning accuracy improved by a factor of two to better than ten microns. Two sMDT chambers have been installed in ATLAS in 2014 to improve the momentum resolution in the barrel part of the spectrometer. The construction of additional twelve chambers covering the feet regions of the ATLAS detector has started. It will be followed by the replacement of the MDT chambers at the ends of the barrel inner layer by sMDTs improving the Performance at the high expected background rates and providing space for additional RPC trigger chambers.

Upgrades of the ATLAS Muon Spectrometer with sMDT Chambers

CERN Document Server

Ferretti, C

2016-01-01

With half the drift-tube diameter of the Monitored Drift Tube (MDT) chambers of the ATLAS muon spectrometer and otherwise unchanged operating parameters, small-diameter Muon Drift Tube (sMDT) chambers provide an order of magnitude higher rate capability and can be installed in detector regions where MDT chambers do not fit. The chamber assembly time has been reduced by a factor of seven to one working day and the sense wire positioning accuracy improved by a factor of two to better than ten microns. Two sMDT chambers have been installed in ATLAS in 2014 to improve the momentum resolution in the barrel part of the spectrometer. The construction of an additional twelve chambers covering the feet regions of the ATLAS detector has started. It will be followed by the replacement of the MDT chambers at the ends of the barrel inner layer by sMDTs improving the Performance at the high expected background rates and providing space for additional RPC trigger chambers.

Upgrades Of The ATLAS Muon Spectrometer With sMDT Chambers

CERN Document Server

Ferretti, Claudio; The ATLAS collaboration

2015-01-01

The Monitored Drift Tube (MDT) chambers of the ATLAS muon spectrometer demonstrated that they provide very precise and robust tracking over large areas. Goals of ATLAS muon detector upgrades are to increase the acceptance for precision muon momentum measurement and triggering and to improve the rate capability of the muon chambers in the high-background regions when the LHC luminosity increases. Small-diameter Muon Drift Tube (sMDT) chambers have been developed for these purposes. With half the drift-tube diameter of the MDT chambers and otherwise unchanged operating parameters, sMDT chambers share the advantages with the MDTs, but have more than ten times higher rate capability and can be installed in detector regions where MDT chambers do not fit in. The chamber assembly methods have been optimized for mass production, reducing cost and construction time considerably and improving the sense wire positioning accuracy to better than ten microns. Two sMDT chambers have been installed in 2014 to improve the mom...

Design and Development of a control system for the Drift Tube Chamber High Voltage Power Supply

CERN Document Server

Leon Vega, Luis Gerardo

2017-01-01

This paper contains information related to the design and development of a control and data acquisition manager implemented in WinCC, a Siemens SCADA system. The goal was to manage a CAEN HV (High Voltage) system for powering a Drift Tube (DT) chamber of the CMS experiment. Basically, this manager consists of two sections: a friendly user interface and powerful scripts to manage the back-end. It is in charge of adjusting the power supply settings to the correct values needed for the DT Chamber operations (ON, OFF, Standby), depending of the requirements of the operator, managing automatically all the transition process. Also, the manager is in charge of configuring the archiving process for acquiring data and providing the history of the system. It also implements the monitoring of the status of each connected channel, alerting in case it is needed.

On-chamber readout system for the ATLAS MDT Muon Spectrometer

CERN Document Server

Chapman, J; Ball, R; Brandenburg, G; Hazen, E; Oliver, J; Posch, C

2004-01-01

The ATLAS MDT Muon Spectrometer is a system of approximately 380,000 pressurized cylindrical drift tubes of 3 cm diameter and up to 6 meters in length. These Monitored Drift Tubes (MDTs) are precision- glued to form super-layers, which in turn are assembled into precision chambers of up to 432 tubes each. Each chamber is equipped with a set of mezzanine cards containing analog and digital readout circuitry sufficient to read out 24 MDTs per card. Up to 18 of these cards are connected to an on-chamber DAQ element referred to as a Chamber Service Module, or CSM. The CSM multiplexes data from the mezzanine cards and outputs this data on an optical fiber which is received by the off-chamber DAQ system. Thus, the chamber forms a highly self-contained unit with DC power in and a single optical fiber out. The Monitored Drift Tubes, due to their length, require a terminating resistor at their far end to prevent reflections. The readout system has been designed so that thermal noise from this resistor remains the domi...

SLD Design Report

International Nuclear Information System (INIS)

1984-05-01

This Design Report describes the plans for the construction of the second detector for the SLAC Linear Collider to study e + e - collisions at energies of up to 100 GeV in the center-of-mass. Particle tracking and momentum measurement are provided by a vertex detector, a high-precision central drift chamber, and pairs of endcap drift chambers, all in a 1 Tesla magnetic field produced by a superconducting solenoid. Particle identification is provided by CRIDs (Cerenkov Ring Imaging Detectors). Calorimetry is done in two parts; a liquid argon calorimeter (LAC) with uranium and iron radiators is located inside the coil, and the laminated iron of the flux return is instrumented with limited-streamer-mode tubes to complete the hadron calorimetry. The streamer tubes of this warm-iron calorimeter, called the WIC, are instrumented with strip readout to provide muon tracking in addition to calorimetry. The same technology is used on the end structures of the detector and the central region, thus providing uniform response in both regions

Plasma chemistry in wire chambers

International Nuclear Information System (INIS)

Wise, J.

1990-05-01

The phenomenology of wire chamber aging is discussed and fundamentals of proportional counters are presented. Free-radical polymerization and plasma polymerization are discussed. The chemistry of wire aging is reviewed. Similarities between wire chamber plasma (>1 atm dc-discharge) and low-pressure rf-discharge plasmas, which have been more widely studied, are suggested. Construction and use of a system to allow study of the plasma reactions occurring in wire chambers is reported. A proportional tube irradiated by an 55 Fe source is used as a model wire chamber. Condensable species in the proportional tube effluent are concentrated in a cryotrap and analyzed by gas chromatography/mass spectrometry. Several different wire chamber gases (methane, argon/methane, ethane, argon/ethane, propane, argon/isobutane) are tested and their reaction products qualitatively identified. For all gases tested except those containing methane, use of hygroscopic filters to remove trace water and oxygen contaminants from the gas resulted in an increase in the average molecular weight of the products, consistent with results from low-pressure rf-discharge plasmas. It is suggested that because water and oxygen inhibit polymer growth in the gas phase that they may also reduce polymer deposition in proportional tubes and therefore retard wire aging processes. Mechanistic implications of the plasma reactions of hydrocarbons with oxygen are suggested. Unresolved issues in this work and proposals for further study are discussed

A study of the self-quenched streamer mode using a nitrogen laser

International Nuclear Information System (INIS)

An Jigang; Anderson, K.J.; Merritt, F.S.; Oreglia, M.; Pilcher, J.E.; Possoz, A.; Schappert, W.; Chicago Univ., IL

1988-01-01

The characteristics and mechanism of the self-quenched streamer mode have been explored using laser induced ionization. Both the size of the streamer signal and the transformation from proportional to streamer mode depend on high voltage and the primary ionization density. Two nearby tracks influence each other mainly by space charge effects. The zone of influence depends on relative drift time of the tracks but is less than 3 mm along the anode. The influence is less with argon-free strong quenching gas mixtures. (orig.)

Two-dimensional potential and charge distributions of positive surface streamer

International Nuclear Information System (INIS)

Tanaka, Daiki; Matsuoka, Shigeyasu; Kumada, Akiko; Hidaka, Kunihiko

2009-01-01

Information on the potential and the field profile along a surface discharge is required for quantitatively discussing and clarifying the propagation mechanism. The sensing technique with a Pockels crystal has been developed for directly measuring the potential and electric field distribution on a dielectric material. In this paper, the Pockels sensing system consists of a pulse laser and a CCD camera for measuring the instantaneous two-dimensional potential distribution on a 25.4 mm square area with a 50 μm sampling pitch. The temporal resolution is 3.2 ns which is determined by the pulse width of the laser emission. The transient change in the potential distribution of a positive surface streamer propagating in atmospheric air is measured with this system. The electric field and the charge distributions are also calculated from the measured potential profile. The propagating direction component of the electric field near the tip of the propagating streamer reaches 3 kV mm -1 . When the streamer stops, the potential distribution along a streamer forms an almost linear profile with the distance from the electrode, and its gradient is about 0.5 kV mm -1 .

Reliability of Eustachian tube function measurements in a hypobaric and hyperbaric pressure chamber.

Science.gov (United States)

Meyer, M F; Jansen, S; Mordkovich, O; Hüttenbrink, K-B; Beutner, D

2017-12-01

Measurement of the Eustachian tube (ET) function is a challenge. The demand for a precise and meaningful diagnostic tool increases-especially because more and more operative therapies are being offered without objective evidence. The measurement of the ET function by continuous impedance recording in a pressure chamber is an established method, although the reliability of the measurements is still unclear. Twenty-five participants (50 ears) were exposed to phases of compression and decompression in a hypo- and hyperbaric pressure chamber. The ET function reflecting parameters-ET opening pressure (ETOP), ET opening duration (ETOD) and ET opening frequency (ETOF)-were determined under exactly the same preconditions three times in a row. The intraclass correlation coefficient (ICC) and Bland and Altman plot were used to assess test-retest reliability. ICCs revealed a high correlation for ETOP and ETOF in phases of decompression (passive equalisation) as well as ETOD and ETOP in phases of compression (active induced equalisation). Very high correlation could be shown for ETOD in decompression and ETOF in compression phases. The Bland and Altman graphs could show that measurements provide results within a 95 % confidence interval in compression and decompression phases. We conclude that measurements in a pressure chamber are a very valuable tool in terms of estimating the ET opening and closing function. Measurements show some variance comparing participants, but provide reliable results within a 95 % confidence interval in retest. This study is the basis for enabling efficacy measurements of ET treatment modalities. © 2017 John Wiley & Sons Ltd.

Study of an avalanche-mode resistive plate chamber

International Nuclear Information System (INIS)

Ying, J.; Ban, Y.; Liu, H.T.; Zhu, Z.M.; Zhu, Z.Y.; Chen, T.; Ma, J.G.; Ye, Y.L.

2000-01-01

Resistive plate chambers (RPCs) are widely used to detect high-energy charged particles, especially muons, due to the high gain, moderate time and spatial resolution, simple design and low cost of these detectors. While the simple streamer mode is adequate for cosmic-ray and low-rate accelerator experiments, the avalanche mode is required for high-rate experiments such as CMS at LHC. In this paper construction of a medium-sized double-gap RPC made of Chinese materials is reported. The experimental set-up of cosmic-ray and muon beam tests are introduced. The avalanche mode was clearly observed. Good efficiency and time resolution were obtained from the beam test at CERN under normal irradiation conditions. At very high radiation background the chamber efficiency decreases, indicating the necessity to change the resistivity value of the Chinese bakelites. (author)

Development of puncture resistance tire tube; Nirinsha no taipankusei kojo cube no kaihatsu

Energy Technology Data Exchange (ETDEWEB)

Yamagiwa, T; Nakayama, K; Kiyota, S; Tanaka, A [Honda R and D Co. Ltd., Tokyo (Japan); Makisaka, N

1997-10-01

A new tire tube with a puncture resistance function was developed. The tube is a two-chamber structure having an air chamber and a liquid chamber, and the liquid chamber at the crown-side half of the tube is filled with an anti-puncture sealant during a manufacturing process. In a market test, it was confirmed that the number of puncture cases were reduced by 90 % in comparison with conventional tire tubes by using the newly developed tube. This paper describes the structure of the tube and the characteristics of the tube rubber, and the manufacturing process and durability of the tube. 3 refs., 17 figs.

Probing background ionization: positive streamers with varying pulse repetition rate and with a radioactive admixture

International Nuclear Information System (INIS)

Nijdam, S; Van Veldhuizen, E M; Ebert, U; Wormeester, G

2011-01-01

Positive streamers need a source of free electrons ahead of them to propagate. A streamer can supply these electrons by itself through photo-ionization, or the electrons can be present due to external background ionization. Here we investigate the effects of background ionization on streamer propagation and morphology by changing the gas composition and the repetition rate of the voltage pulses, and by adding a small amount of radioactive 85 Kr. We find that the general morphology of a positive streamer discharge in high-purity nitrogen depends on background ionization: at lower background ionization levels the streamers branch more and have a more feather-like appearance. This is observed both when varying the repetition rate and when adding 85 Kr, though side branches are longer with the radioactive admixture. But velocities and minimal diameters of streamers are virtually independent of the background ionization level. In air, the inception cloud breaks up into streamers at a smaller radius when the repetition rate and therefore the background ionization level is higher. When measuring the effects of the pulse repetition rate and of the radioactive admixture on the discharge morphology, we found that our estimates of background ionization levels are consistent with these observations; this gives confidence in the estimates. Streamer channels generally do not follow the paths of previous discharge channels for repetition rates of up to 10 Hz. We estimate the effect of recombination and diffusion of ions and free electrons from the previous discharge and conclude that the old trail has largely disappeared at the moment of the next voltage pulse; therefore the next streamers indeed cannot follow the old trail.

Use of a high density lead glass tubing projection chamber in positron emission tomography and in high energy physics

International Nuclear Information System (INIS)

Conti, M.; Guerra, A.D.; Habel, R.; Mulera, T.; Perez-Mendez, V.; Schwartz, G.

1985-10-01

We describe the principle of operation of a high density Projection Chamber, in which the converter/radiator and drift field shaping structures are combined in the form of high density (5 to 6 g/cm 3 ) lead glass tubing. The main applications of this type of detector to Medical Physics (Positron Emission Tomography) and High Energy Physics (Electromagnetic Calorimetry) are discussed

MHD Simulations of the Eruption of Coronal Flux Ropes under Coronal Streamers

Energy Technology Data Exchange (ETDEWEB)

Fan, Yuhong, E-mail: yfan@ucar.edu [High Altitude Observatory, National Center for Atmospheric Research, 3080 Center Green Drive, Boulder, CO 80301 (United States)

2017-07-20

Using three-dimensional magnetohydrodynamic (MHD) simulations, we investigate the eruption of coronal flux ropes underlying coronal streamers and the development of a prominence eruption. We initialize a quasi-steady solution of a coronal helmet streamer, into which we impose at the lower boundary the slow emergence of a part of a twisted magnetic torus. As a result, a quasi-equilibrium flux rope is built up under the streamer. With varying streamer sizes and different lengths and total twists of the flux rope that emerges, we found different scenarios for the evolution from quasi-equilibrium to eruption. In the cases with a broad streamer, the flux rope remains well confined until there is sufficient twist such that it first develops the kink instability and evolves through a sequence of kinked, confined states with increasing height until it eventually develops a “hernia-like” ejective eruption. For significantly twisted flux ropes, prominence condensations form in the dips of the twisted field lines due to runaway radiative cooling. Once formed, the prominence-carrying field becomes significantly non-force-free due to the weight of the prominence, despite having low plasma β . As the flux rope erupts, the prominence erupts, showing substantial draining along the legs of the erupting flux rope. The prominence may not show a kinked morphology even though the flux rope becomes kinked. On the other hand, in the case with a narrow streamer, the flux rope with less than one wind of twist can erupt via the onset of the torus instability.

Resolution and Efficiency of Monitored Drift-Tube Chambers with Final Read-out Electronics at High Background Rates

CERN Document Server

Dubbert, J; Kortner, O; Kroha, H; Manz, A; Mohrdieck-Möck, S; Rauscher, F; Richter, R; Staude, A; Stiller, W

2003-01-01

The performance of a monitored drift-tube chamber for ATLAS with the final read-out electronics was tested at the Gamma Irradiation facility at CERN under varyin photon irradiation rates of up to 990~Hz\\,cm$^{-2}$ which corresponds to 10 times the highest background rate expected in ATLAS. The signal pulse-height measurement of the final read-out electronics was used to perform time-slewing corrections. The corrections improve the average single-tube resolution from 106~$\\mu$m to 89~$\\mu$m at the nominal discriminator threshold of 44~mV without irradiation, and from 114~$\\mu$m to 89~$\\mu$m at the maximum nominal irradiation rate in ATLAS of 100~Hz\\,cm$^{-2}$. The reduction of the threshold from 44~mV to 34~mV and the time-slewing corrections lead to an average single-tube resolution of 82~$\\mu$m without photon background and of 89~$\\mu$m at 100~Hz\\,cm$^{-2}$. The measured muon detection efficiency agrees with the expectation for the final read-out electronics.

Multi-source waveform inversion of marine streamer data using the normalized wavefield

KAUST Repository

Choi, Yun Seok

2012-01-01

Even though the encoded multi-source approach dramatically reduces the computational cost of waveform inversion, it is generally not applicable to marine streamer data. This is because the simultaneous-sources modeled data cannot be muted to comply with the configuration of the marine streamer data, which causes differences in the number of stacked-traces, or energy levels, between the modeled and observed data. Since the conventional L2 norm does not account for the difference in energy levels, multi-source inversion based on the conventional L2 norm does not work for marine streamer data. In this study, we propose the L2, approximated L2, and L1 norm using the normalized wavefields for the multi-source waveform inversion of marine streamer data. Since the normalized wavefields mitigate the different energy levels between the observed and modeled wavefields, the multi-source waveform inversion using the normalized wavefields can be applied to marine streamer data. We obtain the gradient of the objective functions using the back-propagation algorithm. To conclude, the gradient of the L2 norm using the normalized wavefields is exactly the same as that of the global correlation norm. In the numerical examples, the new objective functions using the normalized wavefields generate successful results whereas conventional L2 norm does not.

Physicist makes muon chamber sing

CERN Multimedia

2007-01-01

This Monitored Drift Tube detector, consisting of argon-CO2-filled aluminium tubes with a wire down the centre of each, will track muons in ATLAS; Tiecke used a single tube from one of these detectors to create the pipes in his organ. Particle physicists can make good musicians; but did you know particle detectors can make good music? That's what NIKHEF physicist Henk Tiecke learned when he used pipes cut from the ATLAS Monitored Drift Tube detector (MDT) to build his own working Dutch-style barrel organ in the autumn of 2005. 'I like to work with my hands,' said Tiecke, who worked as a senior physicist at NIKHEF, Amsterdam, on ZEUS until his retirement last summer. Tiecke had already constructed his barrel organ when he visited some colleagues in the ATLAS muon chambers production area at Nikhef in 2005. He noticed that the aluminium tubes they were using to build the chambers were about three centimetres in diameter-just the right size for a pipe in a barrel organ. 'The sound is not as nice as from wooden...

Flow Analysis of a Rising Crude Oil Micro-Droplet Affected by Attached Microbial Streamers

Science.gov (United States)

Amaro, Matthew; White, Andrew; Jalali, Maryam; Sheng, Jian

2017-11-01

Microfluidic experiments show bacteria flowing past a pinned crude oil droplet produce microbial aggregates and streamers on the oil-water interface. High speed DIC microscopy at 1000 fps for 1 sec with a sampling interval of 10 min captures the evolving flow and bacterial motility as well as adhesion, aggregation and streamer events. With bacteria as tracers, velocity measurements are acquired with in-house PIV-assisted PTV software. Flow fields with spatial resolution 2.5 μm are measured around an O(100) μm drop in a 700 ×700 μm window. Full budgets of the 2D Navier-Stokes equation are faithfully resolved to determine pressure gradients by performing the balance over a control volume enclosing the droplet. Pressure gradients are integrated over the border of the control region to obtain pressure profiles at the leading and trailing edges. A momentum balance can be used to determine the drag induced by the drop and any attached streamers. Cases with and without streamers and their differing flow features are presented. Additionally streamers produce nonzero curl in the pressure gradient field providing a tool for identifying the position of otherwise invisible streamers. Ongoing experiments and future applications of the tools presented here will be discussed. Funded by GoMRI, NSF, ARO.

Local electron mean energy profile of positive primary streamer discharge with pin-plate electrodes in oxygen—nitrogen mixtures

International Nuclear Information System (INIS)

Sima Wen-Xia; Peng Qing-Jun; Yang Qing; Yuan Tao; Shi Jian

2013-01-01

Local electron mean energy (LEME) has a direct effect on the rates of collisional ionization of molecules and atoms by electrons. Electron-impact ionization plays an important role and is the main process for the production of charged particles in a primary streamer discharge. Detailed research on the LEME profile in a primary streamer discharge is extremely important for a comprehensive understanding of the local physical mechanism of a streamer. In this study, the LEME profile of the primary streamer discharge in oxygen-nitrogen mixtures with a pin-plate gap of 0.5 cm under an impulse voltage is investigated using a fluid model. The fluid model includes the electron mean energy density equation, as well as continuity equations for electrons and ions and Poisson's electric field equation. The study finds that, except in the initial stage of the primary streamer, the LEME in the primary streamer tip tends to increase as the oxygen-nitrogen mole ratio increases and the pressure decreases. When the primary streamer bridges the gap, the LEME in the primary streamer channel is smaller than the first ionization energies of oxygen and nitrogen. The LEME in the primary streamer channel then decreases as the oxygen-nitrogen mole ratio increases and the pressure increases. The LEME in the primary streamer tip is primarily dependent on the reduced electric field with mole ratios of oxygen-nitrogen given in the oxygen-nitrogen mixtures. (physics of gases, plasmas, and electric discharges)

Probing photo-ionization: simulations of positive streamers in varying N2:O2 mixtures

OpenAIRE

Wormeester, G; Pancheshnyi, S; Luque, A A; Nijdam, S Sander; Ebert, UM Ute

2010-01-01

htmlabstractPhoto-ionization is the accepted mechanism for the propagation of positive streamers in air though the parameters are not very well known; the efficiency of this mechanism largely depends on the presence of both nitrogen and oxygen. But experiments show that streamer propagation is amazingly robust against changes of the gas composition; even for pure nitrogen with impurity levels below 1 ppm streamers propagate essentially with the same velocity as in air, but their minimal diame...

Numerical modeling of positive streamer in air in nonuniform fields: Efficiency of radicals production

International Nuclear Information System (INIS)

Kulikovsky, A.A.

2001-01-01

The efficiency of streamer corona depends on a number of factors such as geometry of electrodes, voltage pulse parameters, gas pressure etc. In a past 5 years a two-dimensional models of streamer in nonuniform fields in air have been developed. These models allow to simulate streamer dynamics and generation of species and to investigate the influence of external parameters on species production. In this work the influence of Laplacian field on efficiency of radicals generation is investigated

Temperature and EUV Intensity in a Coronal Prominence Cavity and Streamer

Science.gov (United States)

Kucera, T. A.; Gibson, S.E.; Schmit, D. J.; Landi, E.; Tripathi, D.

2012-01-01

We analyze the temperature and EUV line emission of a coronal cavity and surrounding streamer in terms of a morphological forward model. We use a series of iron line ratios observed with the Hinode Extreme-ultraviolet Imaging Spectrograph (EIS) on 2007 Aug. 9 to constrain temperature as a function of altitude in a morphological forward model of the streamer and cavity. We also compare model prediction of the EIS EUV line intensities and polarized brightness (pB) data from the Mauna Loa Solar Observatory (MLSO) MK4. This work builds on earlier analysis using the same model to determine geometry of and density in the same cavity and streamer. The fit to the data with altitude dependent temperature profiles indicates that both the streamer and cavity have temperatures in the range 1.4-1.7 MK. However, the cavity exhibits substantial substructure such that the altitude dependent temperature profile is not sufficient to completely model conditions in the cavity. Coronal prominence cavities are structured by magnetism so clues to this structure are to be found in their plasma properties. These temperature substructures are likely related to structures in the cavity magnetic field. Furthermore, we find that the model overestimates the line intensities by a factor of 4-10, while overestimating pB data by no more than a factor of 1.4. One possible explanation for this is that there may be a significant amount of material at temperatures outside of the range log T(K) approximately equals 5.8 - 6.7 in both the cavity and the streamer.

Chamber Core Structures for Fairing Acoustic Mitigation

National Research Council Canada - National Science Library

Lane, Steven A; Henderson, Kyle; Williams, Andrew; Ardelean, Emil

2007-01-01

.... A composite chamber core fairing consists of many axial tubes sandwiched between face sheets, tubes that can be used as acoustic dampers to reduce low-frequency interior noise with virtually no added mass...

Temperature and pressure effects on the properties of positive streamers in air

NARCIS (Netherlands)

Huiskamp, T.; Heesch, van E.J.M.; Beckers, F.J.C.M.; Hoeben, W.F.L.M.; Pemen, A.J.M.

2012-01-01

In this paper we present experimental results on how the properties of positive, pulsed streamers in air depend on E/n (E is the applied electric field and n is the gas density). Streamers are generated in a wire-cylinder reactor at constant voltage (so constant E). The density is changed either by

A Slow Streamer Blowout at the Sun and Ulysses

Science.gov (United States)

Seuss, S. T.; Bemporad, A.; Poletto, G.

2004-01-01

On 10 June 2000 a streamer on the southeast limb slowly disappeared from LASCO/C2 over approximately 10 hours. A small CME was reported in C2. A substantial interplanetary CME (ICME) was later detected at Ulysses, which was at quadrature with the Sun and SOHO at the time. This detection illustrates the properties of an ICME for a known solar source and demonstrates that the identification can be done even beyond 3 AU. Slow streamer blowouts such as this have long been known but are little studied. We report on the SOHO observation of a coronal mass ejection (CME) on the solar limb and the subsequent in situ detection at Ulysses, which was near quadrature at the time, above the location of the CME. SOHO-Ulysses quadrature was 13 June, when Ulysses was 3.36 AU from the Sun and 58.2 degrees south of the equator off the east limb. The slow streamer blowout was on 10 June, when the SOHO-Sun-Ulysses angle was 87 degrees.

Initiation of Positive Streamers near Uncharged Ice Hydrometeors in the Thundercloud Field

Science.gov (United States)

Babich, L. P.; Bochkov, E. I.

2018-05-01

Since the threshold electric field required for breakdown of air is much higher than the maximum field strength measured in thunderstorm clouds, the problem of lightning initiation still remains unsolved. According to the popular hypothesis, lightning can be initiated by a streamer discharge in the field enhanced near a hydrometeor. To verify the adequacy of this hypothesis, the development of a positive streamer propagating along the thunderstorm electric field in the vicinity of an ice needle at an air pressure corresponding to an altitude of 5 km (which is typical of the lightning initiation conditions) was simulated numerically. The hydrometeor dimensions are determined at which streamers can be initiated at different strengths of the thunderstorm electric field.

Study of the effect of water vapor on a resistive plate chamber with glass electrodes

CERN Document Server

Sakai, H H; Teramoto, Y; Nakano, E E; Takahashi, T T

2002-01-01

We studied the effects of water vapor on the efficiencies of resistive plate chambers with glass electrodes, operated in the streamer mode. With moisture in the chamber gas that has freon as a component (water vapor approx 1000 ppm), a decrease in the efficiency (approx 20%) has been observed after operating for a period of several weeks to a few months. From our study, the cause of the efficiency decrease was identified as a change on the cathode surface. In addition, a recovery method was found: flushing for 1 day with argon bubbled through water containing >=3% ammonia, followed by a few weeks of training with dry gas.

Observations of electric discharge streamer propagation and capillary oscillations on the surface of air bubbles in water

Energy Technology Data Exchange (ETDEWEB)

Sommers, B S; Foster, J E [Department of Nuclear Engineering and Radiological Science, University of Michigan, Ann Arbor, MI, 48109 (United States); Babaeva, N Yu; Kushner, Mark J [Department of Electrical Engineering and Computer Science, University of Michigan, Ann Arbor, MI, 48109 (United States)

2011-03-02

The propagation of electric discharge streamers inside bubbles in liquids is of interest for the remediation of toxins in water and plasma-based surgical instruments. The manner of streamer propagation has an important influence on the production of reactive species that are critical to these applications. Streamer propagation along the surface of electrode-attached bubbles of air in water, previously predicted by numerical simulations, has been experimentally imaged using a fast frame-rate camera. The successive pulsing of the streamer discharge inside the bubbles produced oscillations along the air-water interface. Subsequent streamers were observed to closely follow surface distortions induced by such oscillations. The oscillations likely arise from the non-uniform perturbation of the bubble driven by the electric field of the streamer and were found to be consistent with Kelvin's equation for capillary oscillations. For a narrow range of applied voltage pulse frequencies, the oscillation amplitude increased over several pulse periods indicating, potentially, resonant behaviour. We also observed coupling between bubbles wherein oscillations in a second bubble without an internal discharge were induced by the presence of a streamer in a fixed bubble. (fast track communication)

The effect of reduced air density on streamer-to-leader transition and on properties of long positive leader

International Nuclear Information System (INIS)

Bazelyan, E M; Raizer, Yu P; Aleksandrov, N L

2007-01-01

New results of observations of the leader process in a pressure chamber are presented for reduced air pressures. The analysis of these data and observations of the leader discharge in peak regions shows that the length of the leader tip and some other characteristics vary by several times as pressure decreases from 1 to 0.3 atm, whereas, under the conditions considered, the leader velocity remains almost independent of air density, the leader current being the same. These data are used to extract relationships between discharge parameters. It is shown that, at reduced air densities, electric field in a 'young' section of the leader channel exceeds electric field in the streamer zone. Therefore, transition of the leader process to the final-jump phase is not inevitably followed by a breakdown of the gap for reduced pressures, as opposed to the discharge in atmospheric pressure air. The model suggested previously by the authors for the streamer-to- leader transition at atmospheric pressure is amended to take into account hydrodynamic expansion of the channel and used to simulate the process at a relative air density of 0.3. The calculated results are used to interpret the observations of the leader process at reduced air pressures

Construction and test of sMDT chambers for the ATLAS muon spectrometer

Energy Technology Data Exchange (ETDEWEB)

Takasugi, Eric; Schmidt-Sommerfeld, Korbinian; Kortner, Oliver; Kroha, Hubert [Max-Planck-Institut fuer Physik, Muenchen (Germany)

2016-07-01

In the ATLAS muon spectrometer, Monitored Drift Tube chambers (MDTs) are used for precise tracking measurements. In order to increase the geometric acceptance and rate capability, new chambers have been designed and are under construction to be installed in ATLAS during the winter shutdown of 2016/17 of the LHC. The new chambers have a drift tube diameter of 15 mm (compared to 30 mm of the other MDTs) and are therefore called sMDT chambers. This presentation reports on the progress of chamber construction and on the results of quality assurance tests.

Electron acceleration during streamer collisions in air

DEFF Research Database (Denmark)

Köhn, Christoph; Chanrion, Olivier; Neubert, Torsten

2017-01-01

charge fields, with a Monte Carlo scheme accounting for collisions and ionization. We present the electron density, the electric field, and the velocity distribution as functions of space and time. Assuming a background electric field 1.5 times the breakdown field, we find that the electron density......High-voltage laboratory experiments show that discharges in air, generated over a gap of one meter with maximal voltage of 1 MV, may produce X-rays with photon energies up to 1 MeV. It has been suggested that the photons are bremsstrahlung from electrons accelerated by the impulsive, enhanced field...... during collisions of negative and a positive streamers. To explore this process, we have conducted the first self-consistent particle simulations of streamer encounters. Our simulation model is a 2-D, cylindrically symmetric, particle-in-cell code tracing the electron dynamics and solving the space...

Radio-Frequency Emissions from Streamer Collisions: Implications for High-Energy Processes.

Science.gov (United States)

Luque, A.

2017-12-01

The production of energetic particles in a discharge corona is possibly linked to the collision of streamers of opposite polarities [Cooray et al. (2009), Kochkin et al. (2012), Østgaard et al. (2016)]. There is also experimental evidence linking it to radio-frequency emissions in the UHF frequency range (300 MHz-3 GHz) [Montanyà et al. (2015), Petersen and Beasley (2014)]. Here we investigate these two links by modeling the radio-frequency emissions emanating from an encounter between two counter-propagating streamers. Our numerical model combines self-consistently a conservative, high-order Finite-Volume scheme for electron transport with a Finite-Difference Time-Domain (FDTD) method for electromagnetic propagation. We also include the most relevant reactions for streamer propagation: impact ionization, dissociative attachment and photo-ionization. Our implementation benefits from massive parallelization by running on a General-Purpose Graphical Processing Unit (GPGPU). With this code we found that streamer encounters emit electromagnetic waves predominantly in the UHF range, supporting the hypothesis that streamer collisions are essential precursors of high-energy processes in electric discharges. References Cooray, V., et al., J. Atm. Sol.-Terr. Phys., 71, 1890, doi:10.1016/j.jastp.2009.07.010 (2009). Kochkin, P. O., et al., J. Phys. D, 45, 425202, doi: 10.1088/0022-3727/45/42/425202 (2012). Montanyà, J., et al., J. Atm. Sol.-Terr. Phys., 136, 94, doi:10.1016/j.jastp.2015.06.009, (2015). Østgaard, N., et al., J. Geophys. Res. (Atmos.), 121, 2939, doi:10.1002/2015JD024394 (2016). Petersen, D., and W. Beasley, Atmospheric Research, 135, 314, doi:10.1016/j.atmosres.2013.02.006 (2014).

A PIC-MCC code for simulation of streamer propagation in air

DEFF Research Database (Denmark)

Chanrion, Olivier Arnaud; Neubert, Torsten

2008-01-01

A particle code has been developed to study the distribution and acceleration of electrons in electric discharges in air. The code can follow the evolution of a discharge from the initial stage of a single free electron in a background electric field to the formation of an electron avalanche...... and its transition into a streamer. The code is in 2D axi-symmetric coordinates, allowing quasi 3D simulations during the initial stages of streamer formation. This is important for realistic simulations of problems where space charge fields are essential such as in streamer formation. The charged...... particles are followed in a Cartesian mesh and the electric field is updated with Poisson's equation from the charged particle densities. Collisional processes between electrons and air molecules are simulated with a Monte Carlo technique, according to cross section probabilities. The code also includes...

Spectral analysis of the light emitted from streamers in chlorinated alkane and alkene liquids

International Nuclear Information System (INIS)

Ingebrigtsen, S; Bonifaci, N; Denat, A; Lesaint, O

2008-01-01

We have studied the time-averaged optical emission from fast positive and negative non-breakdown streamers under pulsed divergent field conditions in five chlorocarbon liquids, namely, dichloromethane, 1,2-dichloroethane, tetrachloromethane, trichloroethene and tetrachloroethene. We have accumulated light emitted from the first 10-15 μm trail of a few thousand streamers. We have also briefly studied single breakdown arcs in tetrachloromethane. Atomic lines of hydrogen, chlorine and carbon as well as excited states of C 2 radicals (Swan bands) have been observed, with sufficient resolution for evaluating line and band-shapes. The characteristic broadening, shift and asymmetry of atomic lines varied significantly between the liquids. Differences between the two streamer polarities were comparatively small. Densities of electrons and neutrals in the illuminated phase have been deduced from broadening of atomic lines, atomic excitation temperatures from absolute line intensities and rotational and vibrational temperatures from the Swan bands. The gas densities of the propagating streamers were generally very high (∼10% of critical) and with a high degree of ionization (∼1 per mille ). Dichloromethane and 1,2-dichloroethane produced re-illuminating streamers with densities close to atmospheric conditions, in agreement with a rapid pressure relaxation. Rotational temperatures were high and in the range 2 x 10 3 -6 x 10 3 K for the different liquids. Results can be interpreted to suggest a partial local thermodynamic equilibrium in the streamer plasmas.

Drift velocity and pressure monitoring of the CMS muon drift chambers

CERN Document Server

Sonnenschein, Lars

2011-01-01

The drift velocity in drift tubes of the CMS muon chambers is a key parameter for the muon track reconstruction and trigger. It needs to be monitored precisely in order to detect any deviation from its nominal value. A change in absolute pressure, a variation of the gas admixture or a contamination of the chamber gas by air affect the drift velocity. Furthermore, the temperature and magnetic field influence its value. First data, taken with a dedicated Velocity Drift Chamber (VDC) built by RWTH Aachen IIIA are presented. Another important parameter to be monitored is the pressure inside the muon drift tube chambers. The differential pressure must not exceed a certain value and the absolute pressure has to be kept slightly above ambient pressure to prevent air from entering into the muon drift tube chambers in case of a leak. Latest drift velocity monitoring results are discussed.

System and method having multi-tube fuel nozzle with differential flow

Science.gov (United States)

Hughes, Michael John; Johnson, Thomas Edward; Berry, Jonathan Dwight; York, William David

2017-01-03

A system includes a multi-tube fuel nozzle with a fuel nozzle body and a plurality of tubes. The fuel nozzle body includes a nozzle wall surrounding a chamber. The plurality of tubes extend through the chamber, wherein each tube of the plurality of tubes includes an air intake portion, a fuel intake portion, and an air-fuel mixture outlet portion. The multi-tube fuel nozzle also includes a differential configuration of the air intake portions among the plurality of tubes.

Effect of electric field configuration on streamer and partial discharge phenomena in a hydrocarbon insulating liquid under AC stress

International Nuclear Information System (INIS)

Liu, Z; Liu, Q; Wang, Z D

2016-01-01

This paper concerns pre-breakdown phenomena, including streamer characteristics from a fundamental perspective and partial discharge (PD) measurements from an industrial perspective, in a hydrocarbon insulating liquid. The aim was to investigate the possible changes of the liquid’s streamer and PD characteristics and their correlations when the uniformity of the AC electric field varies. In the experiments, a plane-to-plane electrode system incorporating a needle protrusion was used in addition to a needle-to-plane electrode system. When the applied electric field became more uniform, fewer radial branches occurred and streamer propagation towards the ground electrode was enhanced. The transition from streamer propagation dominated breakdown in divergent fields to streamer initiation dominated breakdown in uniform fields was evidenced. Relationships between streamer and PD characteristics were established, which were found to be electric field dependent. PD of the same apparent charge would indicate longer streamers if the electric field is more uniform. (paper)

Numerical simulation for production of O and N radicals in an atmospheric-pressure streamer discharge

International Nuclear Information System (INIS)

Komuro, Atsushi; Ono, Ryo; Oda, Tetsuji

2012-01-01

A streamer discharge model is developed to analyse the characteristics of a pulsed positive streamer discharge in point-to-plane electrodes filled with oxygen-nitrogen mixed gas at room temperature and atmospheric pressure. In this paper we study the mechanisms of O and N radical production in an atmospheric-pressure streamer discharge. To confirm the validity of the simulation model, the discharge emission of light and the discharge current are compared with experimental data at several voltages in gas mixtures with 2-20% oxygen concentrations. The calculated streak picture and the axial distribution of streamer luminous intensity are in good agreement with our previous experimental results. After demonstrating the reliability of the model, we performed a numerical study on radical production by the streamer discharge. The experimentally obtained axial distributions of oxygen radical production in O 2 (20%)/N 2 and nitrogen radical production in O 2 (2%)/N 2 are successfully reproduced in our simulation. For the production of nitrogen radicals, two-step dissociation through the vibrationally excited states is predominant. (paper)

Results from the MAC Vertex chamber

International Nuclear Information System (INIS)

Nelson, H.N.

1987-05-01

The design, construction, and performance characteristics of a high precision gaseous drift chamber made of thin walled proportional tubes are described. The device achieved an average spatial resolution of 45 μm in use for physics analysis with the MAC detector. The B-lifetime result obtained with this chamber is discussed

Streamer Motives and User-Generated Content on Social Live-Streaming Services

OpenAIRE

Friedlander, Mathilde B.

2017-01-01

Three most popular information services, Periscope, Ustream, and YouNow, vicarious for all Social Live-Streaming Services (SLSSs), are investigated to analyze their streamers' motivations and the user-generated content. Additionally, we collected demographic data (gender and age). More than 7,500 streams by users from the U.S., Germany, and Japan were observed. Main streamer motivations on SLSSs are boredom, socializing, the need to reach a specific group, the need to communicate, and fun. Im...

Drift velocity and pressure monitoring of the CMS muon drift chambers

CERN Document Server

Sonnenschein, Lars

2010-01-01

The drift velocity in drift tubes of the CMS muon chambers is a key parameter for the muon track reconstruction and trigger. It needs to be monitored precisely in order to detect any deviation from its nominal value. A change in absolute pressure, a variation of the gas admixture or a contamination of the chamber gas by air affect the drift velocity. Furthermore, the temperature and magnetic field influence its value. First data, taken with a dedicated Velocity Drift Chamber (VDC) built by RWTH Aachen IIIA are presented. Another important parameter to be monitored is the pressure inside the muon drift tube chambers because the drift velocity depends on it. Furthermore the differential pressure must not exceed a certain value and the absolute pressure has to be kept slightly above ambient pressure to prevent air from entering into the muon drift tube chambers in case of a leak. Latest pressure monitoring results are discussed.

Experimental Investigation of Pulsed Nanosecond Streamer Discharges for CO2 Reforming

Science.gov (United States)

Pachuilo, Michael; Levko, Dima; Raja, Laxminarayan; Varghese, Philip

2016-09-01

Rapid global industrialization has led to an increase in atmospheric greenhouse gases, specifically carbon dioxide levels. Plasmas present a great potential for efficient reforming of greenhouse gases. There are several plasma discharges which have been reported for reforming process: dielectric barrier discharges (DBD), microwave discharges, and glide-arcs. Microwave discharges have CO2 conversion energy efficiency of up to 40% at atmospheric conditions, while glide-arcs have 43% and DBD 2-10%. In our study, we analyze a single nanosecond pulsed cathode directed streamer discharge in CO2 at atmospheric pressure and temperature. We have conducted time resolved imaging with spectral bandpass filters of a streamer discharge with an applied negative polarity pulse. The image sequences have been correlated to the applied voltage and current pulses. From the spectral filters we can determine where spatially and temporally excited species are formed. In this talk we report on spectroscopic studies of the discharge and estimate plasma properties such as temperature and density of excited species and electrons. Furthermore, we report on the effects of pulse polarity as well as anodic streamer discharges on the CO2 conversion efficiency. Finally, we will focus on the effects of vibrational excitation on carbon dioxide reforming efficiency for streamer discharges. Our experimental results will be compared with an accompanying plasma computational model studies.

Electron densities and energies of a guided argon streamer in argon and air environments

International Nuclear Information System (INIS)

Hübner, S; Hofmann, S; Van Veldhuizen, E M; Bruggeman, P J

2013-01-01

In this study we report the temporally and spatially resolved electron densities and mean energies of a guided argon streamer in ambient argon and air obtained by Thomson laser scattering. The plasma is driven by a positive monopolar 3.5 kV pulse, with a pulse width of 500 ns and a frequency of 5 kHz which is synchronized with the high repetition rate laser system. This configuration enables us to use the spatial and temporal stability of the guided streamer to accumulate a multitude of laser/plasma shots by a triple grating spectrometer equipped with an ICCD camera and to determine the electron parameters. We found a strong initial n e -overshoot with a maximum of 7 × 10 19  m −3 and a mean electron energy of 4.5 eV. This maximum is followed by a fast decay toward the streamer channel. Moreover, a 2D distribution of the electron density is obtained which exhibits a peculiar mushroom-like shape of the streamer head with a diameter significantly larger than that of the emission profile. A correlation of the width of the streamer head with the expected pre-ionization channel is found. (paper)

Pseudo-spectral 3D simulations of streamers

NARCIS (Netherlands)

A. Luque (Alejandro); U. M. Ebert (Ute); C. Montijn (Carolynne-Sireeh); W. Hundsdorfer (Willem); J. Schmidt; M. Simek; S. Pekarek; V. Prukner

2007-01-01

textabstractA three-dimensional code for the simulation of streamers is introduced. The code is based on a fluid model for oxygen-nitrogen mixtures that includes drift, diffusion and attachement of electrons and creation of new charge carriers through impact ionization and photo-ionization. The

Multipoint Ignition of a Gas Mixture by a Microwave Subcritical Discharge with an Extended Streamer Structure

Science.gov (United States)

Aleksandrov, K. V.; Busleev, N. I.; Grachev, L. P.; Esakov, I. I.; Ravaev, A. A.

2018-02-01

The results of experimental studies on using an electrical discharge with an extended streamer structure in a quasioptical microwave beam in the multipoint ignition of a propane-air mixture have been reported. The pulsed microwave discharge was initiated at the interior surface of a quartz tube that was filled with the mentioned flammable mixture and introduced into a microwave beam with a subbreakdown initial field. Gas breakdown was initiated by an electromagnetic vibrator. The dependence of the type of discharge on the microwave field strength was examined, the lower concentration threshold of ignition of the propane-air mixture by the studied discharge was determined, and the dynamics of combustion of the flammable mixture with local and multipoint ignition were compared.

Storage chamber for container of radiation-contaminated material

International Nuclear Information System (INIS)

Takakura, Masahide.

1996-01-01

The present invention concerns a storage chamber for containing radiation-contaminated materials in containing tubes and having cooling fluids circulated at the outer side of the containing tubes. The storage chamber comprises a gas supply means connected to the inside of the container tube for supplying a highly heat-conductive gas and a gas exhaustion means for discharging the gas present in the container tube. When containing vessels for radiation-contaminated materials are contained in the container tube, the gases present inside of the container tube is exhausted by means of the gas exhaustion means, and highly heat conductive gases are filled from the gas supply means to the space between the container tube and the containing vessels for the radiation-contaminated materials. When the temperature of the highly heat conductive gas is elevated due to the heat generation of the radiation-contaminated materials, the container tube is heated, and then cooled by the cooling fluid at the outer side of the container tube. In this case, the heat of the radiation-contaminated material-containing vessels is removed by the heat conduction by the highly heat conductive gas to reduce temperature gradient between the containing vessels and the containing tube. This can enhance the cooling effect. (T.M.)

The influence of bremsstrahlung on electric discharge streamers in N₂, O₂ gas mixtures

DEFF Research Database (Denmark)

Köhn, Christoph; Chanrion, Olivier; Neubert, Torsten

2017-01-01

Streamers are ionization filaments of electric gas discharges. Negative polarity streamers propagate primarily through electron impact ionization, whereas positive streamers in air develop through ionization of oxygen by UV photons emitted by excited nitrogen; however, experiments show that posit...

Kinetics of a plasma streamer ionization front

Science.gov (United States)

Taccogna, Francesco; Pellegrini, Fabrizio

2018-02-01

A streamer is a non-linear and non-local gas breakdown mode. Its large-scale coherent structures, such as the ionization front, are the final results of a hierarchical cascade starting from the single particle dynamics. Therefore, this phenomenon covers, by definition, different space and time scales. In this study, we have reproduced the ionization front formation and development by means of a particle-based numerical methodology. The physical system investigated concerns of a high-voltage ns-pulsed surface dielectric barrier discharge. Different reduced electric field regimes ranging from 50 to 500 Td have been considered for two gases: pure atomic Ar and molecular N2. Results have shown the detailed structure of the negative streamer: the leading edge, the head, the interior and the tail. Its dynamical evolution and the front propagation velocity have been calculated for the different cases. Finally, the deviation of the electron energy distribution function from equilibrium behavior has been pointed out as a result of a fast and very localized phenomenon.

Heated Tube Facility

Data.gov (United States)

Federal Laboratory Consortium — The Heated Tube Facility at NASA GRC investigates cooling issues by simulating conditions characteristic of rocket engine thrust chambers and high speed airbreathing...

Radially and temporally resolved electric field of positive streamers in air and modelling of the induced plasma chemistry

Science.gov (United States)

Hoder, T.; Šimek, M.; Bonaventura, Z.; Prukner, V.; Gordillo-Vázquez, F. J.

2016-08-01

The initial stages of transient luminous events (TLEs) occurring in the upper atmosphere of the Earth are, in a certain pressure range, controlled by the streamer mechanism. This paper presents the results of the first laboratory experiments to study the TLE streamer phenomena under conditions close to those of the upper atmosphere. Spectrally and highly spatiotemporally resolved emissions originating from radiative states {{\\text{N}}2}≤ft({{\\text{C}}3}{{\\Pi}u}\\right) (second positive system) and \\text{N}2+≤ft({{\\text{B}}2}Σu+\\right) (first negative system) have been recorded from the positive streamer discharge. Periodic ionizing events were generated in a barrier discharge arrangement at a pressure of 4 torr of synthetic air, i.e. simulating the pressure conditions at altitudes of ≃37 km. Employing Abel inversion on the radially scanned streamer emission and a 2D fitting procedure, access was obtained to the local spectral signatures within the over 106  m s-1 fast propagating streamers. The reduced electric field strength distribution within the streamer head was determined from the ratio of the \\text{N}2+/{{\\text{N}}2} band intensities with peak values up to 500 Td and overall duration of about 10 ns. The 2D profiles of the streamer head electric fields were used as an experimentally obtained input for kinetic simulations of the streamer-induced air plasma chemistry. The radial and temporal computed distribution of the ground vibrational levels of the radiative states involved in the radiative transitions analyzed (337.1 nm and 391.5 nm), atomic oxygen, nitrogen, nitric oxide and ozone concentrations are vizualized and discussed in comparison with available models of the streamer phase of Blue Jet discharges in the stratosphere.

Time characteristics of a self quenching streamer in the coexistence region

International Nuclear Information System (INIS)

Han Jiaxiang; Li Cheng; Xu Zizong; Chen Honfang

1994-01-01

Experimental studies on the time correlation between electrical signals in the primary avalanche and optical signals which are emitted in the avalanches of the limited proportional mode and the self quenching streamer (SQS) mode have demonstrated that there exists a weak optical emission which is almost simultaneous with the limited proportional avalanche, that a streamer pulse in the SQS mode has a few nanoseconds delay relative to the primary avalanche, and that the spread of the delay (FWHM) is also a few nanoseconds. ((orig.))

Development of Fast High-Resolution Muon Drift-Tube Detectors for High Counting Rates

CERN Document Server

INSPIRE-00287945; Dubbert, J.; Horvat, S.; Kortner, O.; Kroha, H.; Legger, F.; Richter, R.; Adomeit, S.; Biebel, O.; Engl, A.; Hertenberger, R.; Rauscher, F.; Zibell, A.

2011-01-01

Pressurized drift-tube chambers are e?cient detectors for high-precision tracking over large areas. The Monitored Drift-Tube (MDT) chambers of the muon spectrometer of the ATLAS detector at the Large Hadron Collider (LHC) reach a spatial resolution of 35 micons and almost 100% tracking e?ciency with 6 layers of 30 mm diameter drift tubes operated with Ar:CO2 (93:7) gas mixture at 3 bar and a gas gain of 20000. The ATLAS MDT chambers are designed to cope with background counting rates due to neutrons and gamma-rays of up to about 300 kHz per tube which will be exceeded for LHC luminosities larger than the design value of 10-34 per square cm and second. Decreasing the drift-tube diameter to 15 mm while keeping the other parameters, including the gas gain, unchanged reduces the maximum drift time from about 700 ns to 200 ns and the drift-tube occupancy by a factor of 7. New drift-tube chambers for the endcap regions of the ATLAS muon spectrometer have been designed. A prototype chamber consisting of 12 times 8 l...

Effect of Fe{sub 3}O{sub 4} nanoparticles on positive streamer propagation in transformer oil

Energy Technology Data Exchange (ETDEWEB)

Lv, Yuzhen, E-mail: yzlv@ncepu.edu.cn [Beijing Key Laboratory of High Voltage and EMC, School of Electric and Electronic Engineering, North China Electric Power University, Beijing, 102206 (China); School of Energy, Power and Mechanical Engineering, North China Electric Power University, Beijing, 102206 (China); Wang, Qi; Ge, Yang [Beijing Key Laboratory of High Voltage and EMC, School of Electric and Electronic Engineering, North China Electric Power University, Beijing, 102206 (China); Zhou, You [Hunan Province Key Laboratory of Smart Grids Operation and Control, Changsha University of Science and Technology, Changsha, 410076 (China); Li, Chengrong, E-mail: lcr@ncepu.edu.cn; Qi, Bo [Beijing Key Laboratory of High Voltage and EMC, School of Electric and Electronic Engineering, North China Electric Power University, Beijing, 102206 (China); State Key Laboratory of Alternate Electrical Power System with Renewable Energy Sources, North China Electric Power University, Beijing, 102206 (China)

2016-03-15

Fe{sub 3}O{sub 4} nanoparticles with an average diameter of 10 nm were prepared and used to modify streamer characteristic of transformer oil. It was found that positive streamer propagation velocity in transformer oil-based Fe{sub 3}O{sub 4} nanofluid is greatly reduced by 51% in comparison with that in pure oil. The evolution of streamer shape is also dramatically affected by the presence of nanoparticles, changing from a tree-like shape with sharp branches in pure oil to a bush-like structure with thicker and denser branches in nanofluid. The TSC results reveal that the modification of Fe{sub 3}O{sub 4} nanoparticle can greatly increase the density of shallow trap and change space charge distribution in nanofluid by converting fast electrons into slow electrons via trapping and de-trapping process in shallow traps. These negative space charges induced by nanoparticles greatly alleviate the electric field distortion in front of the positive streamer tip and significantly hinder the propagation of positive streamer.

Experimental Study on Branch and Diffuse Type of Streamers in Leader Restrike of Long Air Gap Discharge

International Nuclear Information System (INIS)

Chen She; Zeng Rong; Zhuang Chijie; Zhou Xuan; Ding Yujian

2016-01-01

One of the main problems in the Ultra High Voltage (UHV) transmission project is to choose the external insulation distance, which requires a deep understanding of the long air gap discharge mechanism. The leader-streamer propagation is one of most important stages in long air gap discharge. In the conductor-tower lattice configuration, we have measured the voltage, the current on the high voltage side and the electric field in the gap. While the streamer in the leader-streamer system presented a conical or hyperboloid diffuse shape, the clear branch structure streamer in front of the leader was firstly observed by a high speed camera in the experiment. Besides, it is found that the leader velocity, width and injected charge for the branch type streamer are greater than those of a diffuse type. We propose that the phenomenon results from the high humidity, which was 15.5-16.5 g/m 3 in our experiment. (paper)

Cathode readout with stripped resistive drift tubes

International Nuclear Information System (INIS)

Bychkov, V.N.; Kekelidze, G.D.; Novikov, E.A.; Peshekhonov, V.D.; Shafranov, M.D.; Zhiltsov, V.E.

1995-01-01

A straw tube drift chamber prototype has been constructed and tested. The straw tube material is mylar film covered with a carbon layer with a resistivity of 0.5, 30 and 70 kΩ/□. Both the anode wire and the cathode strip signals were detected to study the behaviour of the chamber in the presence of X-ray ionization. The construction and the results of the study are presented. (orig.)

Cathode readout with stripped resistive drift tubes

Science.gov (United States)

Bychkov, V. N.; Kekelidze, G. D.; Novikov, E. A.; Peshekhonov, V. D.; Shafranov, M. D.; Zhiltsov, V. E.

1995-12-01

A straw tube drift chamber prototype has been constructed and tested. The straw tube material is mylar film covered with a carbon layer with a resistivity of 0.5, 30 and 70 kΩ/□. Both the anode wire and the cathode strip signals were detected to study the behaviour of the chamber in the presence of X-ray ionization. The construction and the results of the study are presented.

A nautical study of towed marine seismic streamer cable configurations

Energy Technology Data Exchange (ETDEWEB)

Pedersen, Egil

1996-12-31

This study concerns marine seismic surveying and especially the towed in-sea hardware which is dominated by recording cables (streamers) that are extremely long compared to their diameter, neutrally buoyant and depth controlled. The present work aims to examine the operations from a nautical viewpoint, and the final objective is to propose improvements to the overall efficiency of marine seismic operations. Full-scale data were gathered from seismic vessels in order to identify which physical parameters affect the dynamic motion of the towing vessel and its in-sea hardware. Experimental test programmes have been carried out, and data bases with the hydrodynamic characteristics of the test equipment have been established at speeds comparable to those used in seismic operations. A basic analysis tool to provide dynamic simulations of a seismic streamer cable has been developed by tailoring the computer program system Riflex, and the validation and accuracy of this modified Riflex system are evaluated by performing uncertainty analyses of measurements and computations. Unexpected, low-frequency depth motions in towed seismic streamer cables occasionally take place when seismic data are being acquired. The phenomenon is analysed and discussed. 99 refs., 116 figs., 5 tabs.

A nautical study of towed marine seismic streamer cable configurations

Energy Technology Data Exchange (ETDEWEB)

Pedersen, Egil

1997-12-31

This study concerns marine seismic surveying and especially the towed in-sea hardware which is dominated by recording cables (streamers) that are extremely long compared to their diameter, neutrally buoyant and depth controlled. The present work aims to examine the operations from a nautical viewpoint, and the final objective is to propose improvements to the overall efficiency of marine seismic operations. Full-scale data were gathered from seismic vessels in order to identify which physical parameters affect the dynamic motion of the towing vessel and its in-sea hardware. Experimental test programmes have been carried out, and data bases with the hydrodynamic characteristics of the test equipment have been established at speeds comparable to those used in seismic operations. A basic analysis tool to provide dynamic simulations of a seismic streamer cable has been developed by tailoring the computer program system Riflex, and the validation and accuracy of this modified Riflex system are evaluated by performing uncertainty analyses of measurements and computations. Unexpected, low-frequency depth motions in towed seismic streamer cables occasionally take place when seismic data are being acquired. The phenomenon is analysed and discussed. 99 refs., 116 figs., 5 tabs.

Controlling branching in streamer discharge by laser background ionization

International Nuclear Information System (INIS)

Takahashi, E; Kato, S; Furutani, H; Sasaki, A; Kishimoto, Y

2011-01-01

Irradiation with a KrF laser controlled the positive streamer branching in atmospheric argon gas. This laser irradiation changed the amount of background ionization before the streamer discharge. Measuring the ionization current allowed us to evaluate the initial electron density formed by the KrF laser. We observed characteristic feather-like branching structure and found that it was only suppressed in the irradiated region. The threshold of ionization density which can influence the branching was evaluated to be 5 x 10 5 cm -3 . The relationship between the size of avalanche head and mean distance between initial electrons explained this suppression behaviour. These experimental results support that the feather-like structure originates from the branching model of Loeb-Meek, a probabilistic merging of individual avalanches.

Construction and test of a full-scale prototype of an ATLAS muon spectrometer tracking chamber

International Nuclear Information System (INIS)

Biscossa, A.; Cambiaghi, M.; Conta, C.; Ferrari, R.; Fraternali, M.; Freddi, A.; Iuvino, G.; Lanza, A.; Livan, M.; Negri, A.; Polesello, G.; Rimoldi, A.; Vercellati, F.; Vercesi, V.; Bagnaia, P.; Bini, C.; Capradossi, G.; Ciapetti, G.; Creti, P.; De Zorzi, G.; Iannone, M.; Lacava, F.; Mattei, A.; Nisati, L.; Oberson, P.; Pontecorvo, L.; Rosati, S.; Veneziano, S.; Zullo, A.; Daly, C.H.; Davisson, R.; Guldenmann, H.; Lubatti, H.J.; Zhao, T.

1999-01-01

We have built a full scale prototype of the precision tracking chambers (Monitored Drift Tubes, MDT) for the muon spectrometer of the Atlas Experiment at the LHC collider. This article describes in detail the procedures used in constructing the drift tubes and in assembling the chamber. It presents data showing that the required mechanical precision has been achieved as well as test beam results displaying the over all chamber performance. The article presents data demonstrating the derivation of the space-time relation of the drift tubes by the autocalibration procedure using real data from the tracks crossing the chamber. Autocalibration is the procedure which must be used during run time

Inspection tool for butt-welded tubing

Science.gov (United States)

Horman, D. P.

1977-01-01

Inspection tool for tubing consists of metal casing housing elastic collar. Collar is clamped around weld site under test. Leakage through weld is contained within chamber and is bled to detector via tubing attached to fitting. Tool, originally designed to detect fluid leakage in tubing, can be used to detect gas leaks.

Improvement of fire-tube boilers calculation methods by the numerical modeling of combustion processes and heat transfer in the combustion chamber

Science.gov (United States)

Komarov, I. I.; Rostova, D. M.; Vegera, A. N.

2017-11-01

This paper presents the results of study on determination of degree and nature of influence of operating conditions of burner units and flare geometric parameters on the heat transfer in a combustion chamber of the fire-tube boilers. Change in values of the outlet gas temperature, the radiant and convective specific heat flow rate with appropriate modification of an expansion angle and a flare length was determined using Ansys CFX software package. Difference between values of total heat flow and bulk temperature of gases at the flue tube outlet calculated using the known methods for thermal calculation and defined during the mathematical simulation was determined. Shortcomings of used calculation methods based on the results of a study conducted were identified and areas for their improvement were outlined.

Experiments on how photo- and background ionization affect positive streamers: oxygen concentration, repetition and radioactivity

NARCIS (Netherlands)

Nijdam, S.; Veldhuizen, van E.M.; Ebert, U.

2011-01-01

Positive streamers in air and other oxygen-nitrogen mixtures are generally believed to propagate against the electron drift direction due to photo-ionization. Photo-ionization is the non-local ionization of O2-molecules by UV radiation from excited N2-molecules. This facilitates the streamer

The engineering development of an actively controlled precise muon chamber for the SDC detector

International Nuclear Information System (INIS)

Ayer, F.; Berk, E.; Gorman, J.; Govignon, J.; Sullivan, D.

1992-01-01

As the detector configuration for the Solenoidal Detector Collaboration (SDC) evolved, a number of concepts for MUON chambers were proposed and investigated. The Boston Group (Brandeis, Harvard and Tufts Universities, with Draper Laboratory) has developed a concept incorporating elliptical section drift tubes with field shaping and intermediate wire supports. This approach combines good single and multi-track resolution with a small channel count and modularity at the tube level. Other concepts have been developed which arise from differing interpretations of the fundamental physics and economic requirements. These include: Octagonal Drift Tubes, Unsupported Wires, No Field Shaping, U. Wisconsin; Round Tubes, Unsupported Wires, w or w/o Field Shaping, U. Washington; JFT Chambers (Multi-Wire, Intermediate Support, Field Shaping), KEK, Japan. This paper outlines the mechanical implementation of the Boston MUON chamber concept and discusses the rationale for several key design decisions imposed by the stringent mechanical tolerances. A prototype MUON chamber designed to verify design feasibility, performance, and cost is also described. A special section is devoted to the design and development of an optical alignment system within the chamber, which provides error signals driving the intermediate supports to true position. The Boston subgroup MUON chamber design is called the wine rack concept by virtue of its numerous (non-structural) drift tubes laid into a supporting chamber, which provides structural and handling capability. A number of individual θ,φ, and Stereo chambers is normally grouped into a supermodule, which in turn is assembled into a multi-layer supertower. Supertowers are the basic elements of the SDC MUON System, each comprising three supermodule layers in the barrel region and five in the forward regions

A drift chamber with a new type of straws for operation in vacuum

Science.gov (United States)

Azorskiy, N.; Glonti, L.; Gusakov, Yu.; Elsha, V.; Enik, T.; Kakurin, S.; Kekelidze, V.; Kislov, E.; Kolesnikov, A.; Madigozhin, D.; Movchan, S.; Polenkevich, I.; Potrebenikov, Yu.; Samsonov, V.; Shkarovskiy, S.; Sotnikov, S.; Zinchenko, A.; Danielsson, H.; Bendotti, J.; Degrange, J.; Dixon, N.; Lichard, P.; Morant, J.; Palladino, V.; Gomez, F. Perez; Ruggiero, G.; Vergain, M.

2016-07-01

A 2150×2150 mm2 registration area drift chamber capable of working in vacuum is presented. Thin-wall tubes (straws) of a new type are used in the chamber. A large share of these 9.80 mm diameter drift tubes are made in Dubna from metalized 36 μm Mylar film welded along the generatrix using an ultrasonic welding machine created at JINR. The main features of the chamber and some characteristics of the drift tubes are described. Four such chambers with the X, Y, U, V coordinates each, containing 7168 straws in total, are designed and produced at JINR and CERN. They are installed in the vacuum volume of the NA62 setup in order to study the ultra-rare decay K+ →π+ vv bar and to search for and study rare meson decays. In autumn 2014 the chambers were used for the first time for the data taking in the experimental run of the NA62 at CERN's SPS.

Dual-chamber inflatable oil boom

International Nuclear Information System (INIS)

Blair, R.M.; Tedeschi, E.T.

1993-01-01

An elongated floating material containment boom section is described having a normally vertical ballasted skirt depending from flotation means, and convertible from a flattened collapsed condition to a deployable condition wherein buoyancy chamber means extending along the upper edge of said skirt are inflated to expanded buoyant configuration, including: a gas-impervious sleeve extending along the upper edge of said normally vertical skirt forming a first outer collapsible and inflatable flotation chamber, a first inflation valve connecting the interior of said sleeve with the ambient atmosphere, through which gas under pressure may be introduced into said sleeve to inflate said first buoyant outer flotation chamber, elongated gas-impervious tube means positioned inside said outer flotation chamber and forming second collapsible and inflatable internal flotation bladder chamber means, second inflation valve means connecting the interior of said bladder means through said outer flotation chamber to the ambient atmosphere through which gas under pressure may be introduced into said bladder means to inflate it forming said second flotation chamber means inside said outer flotation chamber

High-resolution seismic reflection surveying with a land streamer

Science.gov (United States)

Cengiz Tapırdamaz, Mustafa; Cankurtaranlar, Ali; Ergintav, Semih; Kurt, Levent

2013-04-01

In this study, newly designed seismic reflection data acquisition array (land streamer) is utilized to image the shallow subsurface. Our acquisition system consist of 24 geophones screwed on iron plates with 2 m spacing, moving on the surface of the earth which are connected with fire hose. Completely original, 4.5 Kg weight iron plates provides satisfactory coupling. This land-streamer system enables rapid and cost effective acquisition of seismic reflection data due to its operational facilities. First test studies were performed using various seismic sources such as a mini-vibro truck, buffalo-gun and hammer. The final fieldwork was performed on a landslide area which was studied before. Data acquisition was carried out on the line that was previously measured by the seismic survey using 5 m geophone and shot spacing. This line was chosen in order to re-image known reflection patterns obtained from the previous field study. Taking penetration depth into consideration, a six-cartridge buffalo-gun was selected as a seismic source to achieve high vertical resolution. Each shot-point drilled 50 cm for gunshots to obtain high resolution source signature. In order to avoid surface waves, the offset distance between the source and the first channel was chosen to be 50 m and the shot spacing was 2 m. These acquisition parameters provided 12 folds at each CDP points. Spatial sampling interval was 1 m at the surface. The processing steps included standard stages such as gain recovery, editing, frequency filtering, CDP sorting, NMO correction, static correction and stacking. Furthermore, surface consistent residual static corrections were applied recursively to improve image quality. 2D F-K filter application was performed to suppress air and surface waves at relatively deep part of the seismic section. Results show that, this newly designed, high-resolution land seismic data acquisition equipment (land-streamer) can be successfully used to image subsurface. Likewise

Nongeometrically converted shear waves in marine streamer data

NARCIS (Netherlands)

Drijkoningen, G.G.; El Allouche, N.; Thorbecke, J.W.; Bada, G.

2012-01-01

Under certain circumstances, marine streamer data contain nongeometrical shear body wave arrivals that can be used for imaging. These shear waves are generated via an evanescent compressional wave in the water and convert to propagating shear waves at the water bottom. They are called

Positive streamer initiation from raindrops in thundercloud fields

DEFF Research Database (Denmark)

Babich, L. P.; Bochkov, E. I.; Kutsyk, I. M.

2016-01-01

required for the streamer formation is larger than the measured thunderstorm fields. Therefore, the results of simulations suggest that second mechanisms must operate to amplify the local field. Such mechanisms could be electric field space variations via collective effects of many hydrometeors or runaway...

Radial dependence of surface streamer-channel luminosity: experimental evidence of Gaussian radiative profiles in Ar and N2

International Nuclear Information System (INIS)

Šimek, M; Ambrico, P F

2012-01-01

Radial distributions of electronically excited species produced during surface streamer propagation were obtained by applying the Abel inverse transform to projected luminosities of single streamers. The streamers were generated in an argon and nitrogen surface coplanar dielectric barrier discharge at atmospheric pressure and their magnified microscopic images were registered with high time resolution. Selected regions of the projected luminosities were processed by the Abel inverse transform procedure based on the Hankel–Fourier method assuming cylindrical symmetry of the streamer channel. Projected as well as Abel-inverted profiles were fitted by Gaussian functions. It is shown that the projected profiles, in addition to the Abel-inverted ones, can be well approximated by the sum of two coaxial Gaussians with two different half-widths and weights. The sharper Gaussian component with higher weight characterizes the radial dependence of the primary cathode-directed streamer-channel luminosity. The second (broader) Gaussian component probably originates either from the pre-breakdown Townsend phase or from the second wave propagating towards the anode. (paper)

Performance and simulation of a double-gap resistive plate chamber in the avalanche mode

CERN Document Server

Ahn Sung Hwan; Hong Byung Sik; Hong Seong Jong; Ito, M; Kang, T I; Kim, B I; Kim, J H; Kim, Y J; Kim, Y U; Koo, D G; Lee Hyup Woo; Lee, K B; Lee Kyong Sei; Lee Seok Jae; Lim, J K; Moon, D H; Nam, S K; Park, S; Park, W J; Rhee June Tak; Ryu, M S; Sim Kwang Souk

2004-01-01

We present a detailed analysis of the time and the charge signals of a prototype double-gap resistive plate chamber for the endcap region of the Compact Muon Solenoid (CMS) detector at the Large Hadron Collider (LHC). The chamber was built with relatively low-resistivity bakelite. The time and the charge results demonstrate that the high- voltage plateau, which satisfies various CMS requirements for the efficiency, the noise cluster rate, the fraction of the large signal, and the streamer probability, can be extended at least up to 400 V with the present design. In addition, a simple avalanche multiplication model is studied in detail. The model can reproduce the experimental charge spectra reasonably well. The charge information enables us to estimate the effective Townsend coefficient in avalanche-mode operation.

Search for short-lived particles produced on nuclei with a heavy liquid mini bubble chamber

CERN Multimedia

2002-01-01

The aim of this experiment is to search for short-lived particles produced in hadronic interactions on nuclei with our high resolution heavy liquid mini bubble chamber BIBC, aiming to establish the cross-section for associated production in hadron-nucleus collisions, its $A$-dependence and an approximate value of the lifetime. The chamber will be operated at a bubble density of 290 bubbles/cm and with an apparent bubble size of 30 $\\mu$m in real space. In test runs at CERN we measured detection efficiencies which, together with simulations of $D\\bar{D}$ production and decay, lead to a sensitivity of 0.25 events/($\\mu$b/N) per day if the lifetime is of the order of $5\\times10^{-13}$s. A null result after 10 days running time would set an upper limit on the production cross section to $3 \\mu$b. \\\\ \\\\ In order to measure the momenta of charged decay products of short-lived particles, the bubble chamber will be placed 1.80 m upstream of the streamer chamber of the NA5 experiment (MPI). The geometrical acceptance ...

Detection of muon bundles at large zenith angles

International Nuclear Information System (INIS)

Aynutdinov, V.M.; Castellina, A.; Chernov, D.V.; Ezubchenko, A.A.; Fulgione, W.; Kindin, V.V.; Kokoulin, R.P.; Kompaniets, K.G.; Konovalov, A.A.; Mannocchi, G.; Petrukhin, A.A.; Rodin, Yu. N.; Saavedra, O.; Shutenko, V.V.; Trinchero, G.; Vernetto, S.; Vonsovsky, N.N.; Yanson, E.E.; Yashin, I.I.

1999-01-01

The large area coordinate detector (DECOR) represents a multilayer system of plastic streamer tube chamber modules surrounding the Cherenkov water calorimeter NEVOD. Experimental data collected during the test expositions of first DECOR supermodules (8 vertical planes with 8.4 m 2 working area) have been analysed, angular and spatial reconstruction accuracies have been estimated. The procedure of the selection of events corresponding to detection of parallel tracks (muon bundles originated in the atmosphere) is discussed

Data-processing problems in filmless readout systems applied to physical experiments

International Nuclear Information System (INIS)

Bogdanova, N.B.; Prikhod'ko, V.I.; Ososkov, G.A.; Gadzhokov, V.

1984-01-01

The applications of filmless readout systems in modern physical experiments are considered. The basic characteristics of systems built on TV tubes and on charge-coupled devices (CCD) are reported. Filmless-data processing problems are formulated: recognition of images of tracks and fiducial marks; data compression; computation of the calibration transforms and of the system accuracy parameter. Results from mathematical algorithms and computer codes are reported for the case of streamer-chamber systems

Effect of the linseed oil surface treatment on the performance of resistive plate chambers

International Nuclear Information System (INIS)

Abbrescia, M.; Colaleo, A.; Iaselli, G.; Maggi, M.; Marangelli, B.; Natali, S.; Nuzzo, S.; Ranieri, A.; Romano, F.; Arena, V.; Bonomi, G.; Braj, A.; Gianini, G.; Liguori, G.; Ratti, S.P.; Riccardi, C.; Viola, L.; Vitulo, P.

1997-01-01

Results on the behaviour of several bakelite resistive plate chambers (RPCs) without the linseed oil treatment of the internal electrodes will be presented. Efficiency, collected charge and cluster size distributions will be compared to the ones of a standard oiled RPC. Currents and single rate are the quantities most affected by the surface treatment of the electrodes beyond the optical/mechanical properties. A factor 4 less in currents and at least a factor 10 less in single rate is achieved using standard oiled RPCs operated in streamer mode. (orig.)

Electrons in the solar corona. Pt. 3. Coronal streamers analysis from balloon-borne coronagraph

Energy Technology Data Exchange (ETDEWEB)

Dollfus, A; Mouradian, Z [Observatoire de Paris, Section de Meudon, 92 (France)

1981-03-01

During a balloon flight in France on September 13, 1971, at altitude 32 000 m, the solar corona was cinematographed from 2 to 5 Rsub(sun) during 5 hr, with an externally occulted coronagraph. Motions in coronal features, when they occur, exhibit deformations of structures with velocities not exceeding a few 10 km s/sup -1/; several streamers were often involved simultaneously; these variations are compatible with magnetic changes or sudden reorganizations of lines of forces. Intensity and polarization measurements give the electron density with height in the quiet corona above the equator. Electron density gradient for one of the streamers gives a temperature of 1.6 x 10/sup 6/ K and comparisons with the on-board Apollo 16 coronal observation of 31 July, 1971 are compatible with the extension of this temperature up to 25 Rsub(sun). Three-dimensional structures and localizations of the streamers are deduced from combined photometry, polarimetry and ground-based K coronametry. Three of the four coronal streamers analysed have their axis bent with height towards the direction of the solar rotation, as if the upper corona has a rotation slightly faster than the chromosphere.

Sag compensation system for assembly of MDT-chambers for the ATLAS experiment

International Nuclear Information System (INIS)

Barashkov, A.V.; Glonti, G.L.; Gongadze, A.L.; Evtukhovich, P.G.; Il'yushenko, E.N.; Kotov, S.A.; Kruchonok, V.G.; Tskhadadze, Eh.G.; Chepurnov, V.F.; Shelkov, G.A.

2005-01-01

The description of a system of the devices created for compensation of the gravitational deflection of the drift chamber during its assembly is presented. By means of this system during stage-by-stage gluing of layers of tube drift detectors to the chamber the transversal deflection considerably decreases and by that high accuracy of mutual position of separate tubes is provided. The devices were applied at assembly of 74 MDT-chambers of the ATLAS experiment. Design values of deformation of the chambers as well as the results of measurement of transversal deflections obtained during the assembly with the use of the system of sag compensation are given. Testing of chambers on the X-ray tomograph at CERN has shown that the accuracy of the positions of separate signal wires inside the assembled chambers is within the limits of the required 20 μm

Evaluation of the effectiveness of light streamer tori-lines and characteristics of bait attacks by seabirds in the western North Pacific.

Directory of Open Access Journals (Sweden)

Noriyosi Sato

Full Text Available To improve the effectiveness of tori-lines it is necessary to evaluate the ability of tori-lines to mitigate seabird bycatch and determine what kind of seabird species gather during line settings, attack the bait and are incidentally caught. We conducted two experiments in the western North Pacific and examined the effectiveness for seabird mitigation of light streamer tori-lines which have no long streamers but many light (short streamers and are mainly used in the North Pacific area. Firstly, the effectiveness of two different types of tori-line (light streamer (1 m and long streamer (up to 7 m tori-line and of two different colors (yellow and red of light streamers for seabird bycatch avoidance was evaluated using 567 sets based on data from 20 offshore surface commercial longliners. No significant difference in the bycatch number between the different tori-line types and streamer colors was found. Secondly, we investigated the characteristics of the seabird bycatch in the North Pacific and the effectiveness of three different types of streamers (light, hybrid and modified light types by detailed observations of seabird attacks using a chartered longline vessel. Although the appearance rate of albatrosses and shearwaters were 40.9% and 27.7%, Laysan albatross was the main seabird species that followed the vessel but shearwaters seldom followed the vessel and did not aggregate during line setting. In all attacks on bait observed during line settings, 81% and 7% were by albatrosses and shearwaters, respectively. In the number of primary attacks by Laysan albatrosses which attacked most aggressively of all seabirds, there were no significant differences among the tori-line types. No individuals of shearwater were caught. The results of both experiments indicated that light streamer tori-lines were as effective as tori-lines with long streamers for mitigating seabird bycatch in the North Pacific.

Recent developments in wire chamber tracking at SSC

International Nuclear Information System (INIS)

Ogren, H.

1990-01-01

All of the major SSC proposed detectors use wire chambers in their tracking systems. The feasibility of wire chambers in an SSC detector has now been established by a number of groups planning detectors at SSC. The major advances during the past year in understanding straw tube drift chambers are presented and several innovations in gaseous wire chambers are discussed. The R and D section will concentrate on progress in drift cell design, electronics and signal processing, and engineering aspects of the tracking designs

ATLAS Muon Drift Tube Electronics

CERN Document Server

Arai, Y; Beretta, M; Boterenbrood, H; Brandenburg, G W; Ceradini, F; Chapman, J W; Dai, T; Ferretti, C; Fries, T; Gregory, J; Guimarães da Costa, J; Harder, S; Hazen, E; Huth, J; Jansweijer, P P M; Kirsch, L E; König, A C; Lanza, A; Mikenberg, G; Oliver, J; Posch, C; Richter, R; Riegler, W; Spiriti, E; Taylor, F E; Vermeulen, J; Wadsworth, B; Wijnen, T A M

2008-01-01

This paper describes the electronics used for the ATLAS monitored drift tube (MDT) chambers. These chambers are the main component of the precision tracking system in the ATLAS muon spectrometer. The MDT detector system consists of 1,150 chambers containing a total of 354,000 drift tubes. It is capable of measuring the sagitta of muon tracks to an accuracy of 60 microns, which corresponds to a momentum accuracy of about 10% at pT = 1 TeV. The design and performance of the MDT readout electronics as well as the electronics for controlling, monitoring and powering the detector will be discussed. These electronics have been extensively tested under simulated running conditions and have undergone radiation testing certifying them for more than 10 years of LHC operation. They are now installed on the ATLAS detector and are operating during cosmic ray commissioning runs.

TEMPERATURE AND EXTREME-ULTRAVIOLET INTENSITY IN A CORONAL PROMINENCE CAVITY AND STREAMER

Energy Technology Data Exchange (ETDEWEB)

Kucera, T. A. [NASA/GSFC, Code 671, Greenbelt, MD 20771 (United States); Gibson, S. E.; Schmit, D. J. [HAO/NCAR, P.O. Box 3000, Boulder, CO 80307-3000 (United States); Landi, E. [Department of Atmospheric, Oceanic and Space Science, Space Research Building, University of Michigan, 2455 Hayward St., Ann Arbor, MI 48109-2143 (United States); Tripathi, D. [Inter-University Centre for Astronomy and Astrophysics, Post Bag-4, Ganeshkhind, Pune University Campus, Pune 411 007 (India)

2012-09-20

We analyze the temperature and EUV line emission of a coronal cavity and surrounding streamer in terms of a morphological forward model. We use a series of iron line ratios observed with the Hinode Extreme-ultraviolet Imaging Spectrograph (EIS) on 2007 August 9 to constrain temperature as a function of altitude in a morphological forward model of the streamer and cavity. We also compare model predictions to the EIS EUV line intensities and polarized brightness (pB) data from the Mauna Loa Solar Observatory (MLSO) Mark 4 K-coronameter. This work builds on earlier analysis using the same model to determine geometry of and density in the same cavity and streamer. The fit to the data with altitude-dependent temperature profiles indicates that both the streamer and cavity have temperatures in the range 1.4-1.7 MK. However, the cavity exhibits substantial substructure such that the altitude-dependent temperature profile is not sufficient to completely model conditions in the cavity. Coronal prominence cavities are structured by magnetism so clues to this structure are to be found in their plasma properties. These temperature substructures are likely related to structures in the cavity magnetic field. Furthermore, we find that the model overestimates the EUV line intensities by a factor of 4-10, without overestimating pB. We discuss this difference in terms of filling factors and uncertainties in density diagnostics and elemental abundances.

Stepwise expansion of a surface dielectric barrier discharge as a result of alternation in formation of streamers and leaders

International Nuclear Information System (INIS)

Akishev, Yu; Aponin, G; Balakirev, A; Grushin, M; Petryakov, A; Karal'nik, V; Trushkin, N

2013-01-01

Spatial–temporal development of the plasma sheet structure in a surface dielectric barrier discharge (SDBD) powered with a single long pulse of negative polarity is traced. Ambient air and Ar at atmospheric pressure are used as plasma-forming gases. It is found that current regimes and spatial structures occurring at the development of a long-pulsed discharge differ cardinally as compared with those of a short-pulsed SDBD. In the case of long-pulsed SDBDs, the expansion of the barrier area covered by the plasma sheet and seeded with a surface negative charge occurs in a stepwise manner due to cyclic alternation (one after another) in generation of surface streamers and formation of hot surface leaders from the streamers due to streamer–leader transitions. Leaders, in their turn, initiate new streamers, which serve again as precursors for next-step leader formation, and so on. However, the crucial role in surface charge deposition is played not by streamers and leaders but by a diffusive plasma sheet (DPS), which slowly extends from the sides of streamers and leaders. The expansion of the DPS occurs due to the ionization wave propagating from the sides of the streamers and leaders. The difference in spatial structures of a single long-pulsed and a steady-state sin SDBD is studied. In high-frequency sin SDBDs at negative half-cycle there are only leaders and DPS, but there are no streamers. The reason is that there is no necessity for the formation of leaders due to streamer–leader transitions—leaders are formed at the previous cycle and do not decay strongly till the beginning of the next cycle, and they recover themselves without streamers. (paper)

Laboratory experiments cannot be utilized to justify the action of early streamer emission terminals

International Nuclear Information System (INIS)

Becerra, Marley; Cooray, Vernon

2008-01-01

The early emission of streamers in laboratory long air gaps under switching impulses has been observed to reduce the time of initiation of leader positive discharges. This fact has been arbitrarily extrapolated by the manufacturers of early streamer emission devices to the case of upward connecting leaders initiated under natural lightning conditions, in support of those non-conventional terminals that claim to perform better than Franklin lightning rods. In order to discuss the physical basis and validity of these claims, a self-consistent model based on the physics of leader discharges is used to simulate the performance of lightning rods in the laboratory and under natural lightning conditions. It is theoretically shown that the initiation of early streamers can indeed lead to the early initiation of self-propagating positive leaders in laboratory long air gaps under switching voltages. However, this is not the case for positive connecting leaders initiated from the same lightning rod under the influence of the electric field produced by a downward moving stepped leader. The time evolution of the development of positive leaders under natural conditions is different from the case in the laboratory, where the leader inception condition is closely dependent upon the initiation of the first streamer burst. Our study shows that the claimed similarity between the performance of lightning rods under switching electric fields applied in the laboratory and under the electric field produced by a descending stepped leader is not justified. Thus, the use of existing laboratory results to validate the performance of the early streamer lightning rods under natural conditions is not justified

Application of multi-source waveform inversion to marine streamer data using the global correlation norm

KAUST Repository

Choi, Yun Seok

2012-05-02

Conventional multi-source waveform inversion using an objective function based on the least-square misfit cannot be applied to marine streamer acquisition data because of inconsistent acquisition geometries between observed and modelled data. To apply the multi-source waveform inversion to marine streamer data, we use the global correlation between observed and modelled data as an alternative objective function. The new residual seismogram derived from the global correlation norm attenuates modelled data not supported by the configuration of observed data and thus, can be applied to multi-source waveform inversion of marine streamer data. We also show that the global correlation norm is theoretically the same as the least-square norm of the normalized wavefield. To efficiently calculate the gradient, our method employs a back-propagation algorithm similar to reverse-time migration based on the adjoint-state of the wave equation. In numerical examples, the multi-source waveform inversion using the global correlation norm results in better inversion results for marine streamer acquisition data than the conventional approach. © 2012 European Association of Geoscientists & Engineers.

Cathode Readout with Stripped Resistive Drift Tubes

International Nuclear Information System (INIS)

Bychkov, V.N.; Kekelidze, G.D.; Novikov, E.A.; Peshekhonov, V.D.; Shafranov, M.D.; Zhil'tsov, V.E.

1994-01-01

A straw tube drift chamber prototype has been constructed and tested. The straw tube material is mylar film covered with carbon layer of resistivity 0.5, 30 and 70 k Ohm/sq. The gas mixture used was Ar/CH 4 . Both the anode wire and cathode signals were detected in order to study the behaviour of the chamber in the presence of X-ray ionization. The construction and the results of the study are presented. 7 refs., 11 figs., 1 tab

Commissioning activities of CMS Drift Tubes (DT) chambers at SX5

CERN Multimedia

Domenico Dattola

2005-01-01

After DT and RPC packages have been installed, and before their cabling, single chamber commissioning takes place. It consists of a series of performance test on the on-chamber minicrates, containing readout and trigger electronics, as well as high voltage tests and cosmic data taking. The pictures show the preparation activities for the chamber commissioning in the construction hall in Cessy (neighbouring France), called SX5.

Numerical simulation of evolution of electron-hole avalanches and streamers in silicon in a uniform electric field

International Nuclear Information System (INIS)

Kyuregyan, A. S.

2010-01-01

Numerical simulation of origination and evolution of streamers in Si is performed for the first time. It is assumed that an external electric field E 0 is constant and uniform, the avalanche and streamer are axially symmetric, and background electrons and holes are absent. The calculations have been performed in the context of the diffusion-drift approximation with impact and tunneling ionization, Auger recombination, and electron-hole scattering taken into account. The most realistic values of the ionization and recombination rates, diffusion coefficients, and drift mobilities of electrons and holes have been used. It is shown that the features of evolution of avalanches and streamers are generally consistent with the result obtained previously for a hypothetic semiconductor with equal kinetic coefficients for electrons and holes. Asymmetry of these coefficients (mostly, the impact-ionization coefficients) manifests itself only at the initial stage of evolution. However, with time, two exponentially self-similar streamers are formed, differing only in the sign of charge of fronts and directions of their propagation. Empirical dependences of the main parameters of streamers on E 0 in the range of 0.34-0.75 MV/cm have been derived for this most important stage of evolution.

Filaments in curved streamlines: rapid formation of Staphylococcus aureus biofilm streamers

International Nuclear Information System (INIS)

Kevin Kim, Minyoung; Drescher, Knut; Shun Pak, On; Stone, Howard A; Bassler, Bonnie L

2014-01-01

Biofilms are surface-associated conglomerates of bacteria that are highly resistant to antibiotics. These bacterial communities can cause chronic infections in humans by colonizing, for example, medical implants, heart valves, or lungs. Staphylococcus aureus, a notorious human pathogen, causes some of the most common biofilm-related infections. Despite the clinical importance of S. aureus biofilms, it remains mostly unknown how physical effects, in particular flow, and surface structure influence biofilm dynamics. Here we use model microfluidic systems to investigate how environmental factors, such as surface geometry, surface chemistry, and fluid flow affect biofilm development of S. aureus. We discovered that S. aureus rapidly forms flow-induced, filamentous biofilm streamers, and furthermore if surfaces are coated with human blood plasma, streamers appear within minutes and clog the channels more rapidly than if the channels are uncoated. To understand how biofilm streamer filaments reorient in flows with curved streamlines to bridge the distances between corners, we developed a mathematical model based on resistive force theory of slender filaments. Understanding physical aspects of biofilm formation of S. aureus may lead to new approaches for interrupting biofilm formation of this pathogen. (paper)

Twin-tubes: 3D tracking based on the ATLAS muon drift tubes

International Nuclear Information System (INIS)

Woudstra, M.; Bobbink, G.J.; Eldik, N. van; Graaf, H. van der; Kluit, P.; Koutsman, A.; Limper, M.; Linde, F.; Massaro, G.; Snuverink, J.; Vreeswijk, M.; Groenstege, H.; Koopstra, J.; Mos, S.; Rewiersma, P.; Timmermans, C.; Dijkema, J.

2006-01-01

The Monitored Drift Tubes (MDTs) of the ATLAS Muon Spectrometer have been paired to form so-called twin-tubes to measure the coordinate which runs along the wire direction. This modification endows the MDTs with full 3D track reconstruction using specially designed electronic boards. The performance of the twin-tubes has been measured for an equipped MDT chamber at the ATLAS Muon Cosmic Ray Test Stand at NIKHEF. The efficiency of a twin-tube has been determined to be 99.8%, and the measured resolution 17 cm per hit. By equipping one multilayer consisting of three layers and combining the measurements a resolution of 10 cm has been obtained

Development of linseed oil-free bakelite resistive plate chambers

International Nuclear Information System (INIS)

Biswas, S.; Bhattacharya, S.; Bose, S.; Chattopadhyay, S.; Saha, S.; Viyogi, Y.P.

2009-01-01

In this paper we would like to present a few characteristics of the Resistive Plate Chambers (RPCs) made of a particular grade of bakelite paper laminates (P-120, NEMA LI-1989 Grade XXX), produced and commercially available in India. This particular grade is used for high voltage insulation in humid conditions. The chambers are tested with cosmic rays in the streamer mode using argon, tetrafluroethane and isobutane in 34:59:7 mixing ratio. In the first set of detectors made with such grade, a thin coating of silicone fluid on the inner surfaces of the bakelite was found to be necessary for operation of the detector. Those silicone coated RPCs were found to give satisfactory performance with stable efficiency of >90% continuously for a long period as reported earlier. Results of the crosstalk measurement of these silicone coated RPC will be presented in this paper. Very recently RPCs made with the same grade of bakelite but having better surface finish are found to give equivalent performance even without any coating inside. Preliminary results of this type of RPCs are also being presented.

Lifetime tests for MAC vertex chamber

International Nuclear Information System (INIS)

Nelson, H.

1986-01-01

A vertex chamber for MAC was proposed in fall 1983 to increase precision in the measurement of the B hadron and tau lepton lifetimes. The chamber had to be placed within the existing central drift chamber, making access for repairs difficult and costly. Therefore for detector elements thin-walled aluminized mylar drift tubes (straws) were used because of their simplicity and robustness. The diameter of the drift tubes was 6.9 mm. The radial extent of the proposed chamber was from 3 cm to 10 cm, the inner wall of the central drift. It was clear that radiation levels, from synchrotron x-rays and overfocussed electrons, were potentially high. Since the drift distance is short in the straws, it was desirable to operate them at the highest possible gas gain, to achieve the best spatial resolution. There was a likelihood of drawing large currents in the chamber and thus causing radiation damage. Therefore a study of radiation hardness under the conditions of their proposed design was undertaken. In tests, argon-hydrocarbon mixtures consistently became unusable at ∼0.05 C/cm collected charge, due to anode buildup. Argon-CO 2 mixtures, while underquenched, were operational to 0.25 C/cm, at which point loss of cathode material became intolerable. Argon-xenon-CO 2 proved to be quenched as well as argon-hydrocarbons, but was limited by cathode damage. The MAC vertex chamber has operated at a distance of 4.6 cm from the e + e - interaction point at PEP for two years and has shown no aging effects

Duplex-tube sodium-indication steam generator

International Nuclear Information System (INIS)

Matal, O.; Martoch, J.

1984-01-01

The steam generator with duplex tubes and sodium indication is connected to the main sodium input and output via the inlet and outlet chambers and has indication spaces connected to the interspaces of the duplex tubes. The first indication space is linked with the auxiliary inlet pipe to the inlet chamber and the second indication space is connected with the auxiliary pipe to the outlet chamber. Mounted to the auxiliary inlet pipe is at least one closure, i.e., a valve or electromagnetic stop. Mounted on the auxiliary outlet pipe is an indication sensor, e.g., a sodium flow sensor. At least one indication space is provided with an alarm sensor, e.g., a thermocouple, a pressure gauge and one sensor to monitor the hydrogen content of sodium. (J.P.)

Laboratory coupling tests for optimum land streamer design over sand dunes surface

KAUST Repository

Almalki, Hashim

2012-02-26

The cost of data acquisition in land is becoming a major issue as we strive to cover larger areas with seismic surveys at high resolution. Over sand dunes the problem is compounded by the week coupling obtain using geophones, which often forces us to bury the phone. A major challenge is designing such a land streamer system that combines durability, mobility and the required coupling. We share a couple of such designs and discuss the merits behind such designs and test their capability. The testing includes, the level of coupling, mobility and drag over sand surfaces. For specific designs loose sand can accumulate inside the steamer reducing its mobility. On the other hand, poor coupling will attenuate the high frequencies and cause an effective delay in the signal. The weight of the streamer is also an important factor in both mobility and coupling as it adds to the coupling it reduces the mobility of the streamer. We study the impact of weight and base plate surface area on the seismic signal quality, as well as the friction factor of different designs.

Development of a test system for the analysis of the read-out electronic cabling for the CMS drift tube chambers

International Nuclear Information System (INIS)

Fernandez Bedoya, C.; Montero, M.; Willmott, C.

2004-01-01

A test system has been developed for the analysis of the read-out electronics cabling for the CMS drift tube chambers. The read-out electronics will be placed inside some aluminium boxes, so-called Minicrates, which are going to be produced soon at CIEMAT. Due to the difficulty of detecting and repairing errors in the cables once they have been installed and recalling also to the large number of Minicrates that are going to be produced, it was decided to design and develop a test system for testing the cabling before its installation. (Author)

Some characteristics of the digitization pulses from high pressure neon-helium flash tubes

International Nuclear Information System (INIS)

Chan, D.S.K.; Leung, S.K.; Ng, L.K.

1979-01-01

Characteristics of the digitization output pulses from high pressure neon-helium flash tubes were studied under various operation conditions using square ultra-high voltage pulses. Properties reported by previous workers were compared. Two discharge mechanisms, the Townsend avalanche discharge and the streamer discharge, were observed to occur in sequence in some events. The output waveforms for both discharge mechanisms were studied in detail. The charge induced on a detecting probe was also estimated from the measured data. (Auth.)

Apparatus for inspecting and repairing a pressurized-water reactor's steam generator heat exchanger tubes

International Nuclear Information System (INIS)

Mueller, O.; Roettger, H.; Kasti, H.; Hagen, H.G.

1976-01-01

Described is an apparatus provided for use with a pressurized-water reactor' steam generator having a manifold chamber enclosing the bottom side of a horizontal tube sheet having holes therethrough in which are mounted the tubes of a heat exchanger tube bundle. The manifold chamber has a manhole giving access to the tube's bottom side to permit internal inspection or repair of the tubes by registration of an end of a flexible guide conduit with the tube sheet holes and through which a flexible carrier can be guided for insertion via these holes in the tube sheet and through the tubes extending from the tube sheet's other side

ATLAS Muon Drift Tube Electronics

Energy Technology Data Exchange (ETDEWEB)

Arai, Y [KEK, High Energy Accelerator Research Organisation, Tsukuba (Japan); Ball, B; Chapman, J W; Dai, T; Ferretti, C; Gregory, J [University of Michigan, Department of Physics, Ann Arbor, MI (United States); Beretta, M [INFN Laboratori Nazionali di Frascati, Frascati (Italy); Boterenbrood, H; Jansweijer, P P M [Nikhef National Institute for Subatomic Physics, Amsterdam (Netherlands); Brandenburg, G W; Fries, T; Costa, J Guimaraes da; Harder, S; Huth, J [Harvard University, Laboratory for Particle Physics and Cosmology, Cambridge, MA (United States); Ceradini, F [INFN Roma Tre and Universita Roma Tre, Dipartimento di Fisica, Roma (Italy); Hazen, E [Boston University, Physics Department, Boston, MA (United States); Kirsch, L E [Brandeis University, Department of Physics, Waltham, MA (United States); Koenig, A C [Radboud University Nijmegen/Nikhef, Dept. of Exp. High Energy Physics, Nijmegen (Netherlands); Lanza, A [INFN Pavia, Pavia (Italy); Mikenberg, G [Weizmann Institute of Science, Department of Particle Physics, Rehovot (Israel)], E-mail: brandenburg@physics.harvard.edu (and others)

2008-09-15

This paper describes the electronics used for the ATLAS monitored drift tube (MDT) chambers. These chambers are the main component of the precision tracking system in the ATLAS muon spectrometer. The MDT detector system consists of 1,150 chambers containing a total of 354,000 drift tubes. It is capable of measuring the sagitta of muon tracks to an accuracy of 60 {mu}m, which corresponds to a momentum accuracy of about 10% at p{sub T}= 1 TeV. The design and performance of the MDT readout electronics as well as the electronics for controlling, monitoring and powering the detector will be discussed. These electronics have been extensively tested under simulated running conditions and have undergone radiation testing certifying them for more than 10 years of LHC operation. They are now installed on the ATLAS detector and are operating during cosmic ray commissioning runs.

3D streamers simulation in a pin to plane configuration using massively parallel computing

Science.gov (United States)

Plewa, J.-M.; Eichwald, O.; Ducasse, O.; Dessante, P.; Jacobs, C.; Renon, N.; Yousfi, M.

2018-03-01

This paper concerns the 3D simulation of corona discharge using high performance computing (HPC) managed with the message passing interface (MPI) library. In the field of finite volume methods applied on non-adaptive mesh grids and in the case of a specific 3D dynamic benchmark test devoted to streamer studies, the great efficiency of the iterative R&B SOR and BiCGSTAB methods versus the direct MUMPS method was clearly demonstrated in solving the Poisson equation using HPC resources. The optimization of the parallelization and the resulting scalability was undertaken as a function of the HPC architecture for a number of mesh cells ranging from 8 to 512 million and a number of cores ranging from 20 to 1600. The R&B SOR method remains at least about four times faster than the BiCGSTAB method and requires significantly less memory for all tested situations. The R&B SOR method was then implemented in a 3D MPI parallelized code that solves the classical first order model of an atmospheric pressure corona discharge in air. The 3D code capabilities were tested by following the development of one, two and four coplanar streamers generated by initial plasma spots for 6 ns. The preliminary results obtained allowed us to follow in detail the formation of the tree structure of a corona discharge and the effects of the mutual interactions between the streamers in terms of streamer velocity, trajectory and diameter. The computing time for 64 million of mesh cells distributed over 1000 cores using the MPI procedures is about 30 min ns-1, regardless of the number of streamers.

Towards a fluid model for the streamer-to-leader transition in lightning channels.

Science.gov (United States)

Malagón, Alejandro; Luque, Alejandro

2017-04-01

Electric discharges are a very common phenomenon on Earth's atmosphere. However some of their features are still poorly understood. A sufficiently long electric discharge, such as a lightning channel, propagates along two phases. The first phase is known as "streamer phase" and consists in thin filaments of ionized air that advance due to a high electric field at their tip. The dominant process of ionization is impact ionization, involving electrons and the two major components in the air mass, which are nitrogen and oxygen. In the second phase called "leader phase", the electric current of the streamers has increased the air temperature highly enough so the thermal energy of the molecules present in the air is comparable to the ionization potential of nitrogen and oxygen. The underlying mechanism whereby the streamer-to-leader transition occurs is not precisely known. High-speed observations show that in negative discharges, comprising 90% of cloud-to-ground lightning, this transition is not smooth but mediated by the formation of a "space leader", that is, an isolated hot segment within the streamer region. This space leader is connected to the main leader in a sudden jump and therefore one speaks of a "stepped leader". However, the origin of the space leader is so far unknown. Here we present recent steps in the modeling of the streamer-to-leader transition, which requires coupling fluid mechanics, electromagnetism and air plasma chemistry. We discuss our work towards a model that solves Euler's equations (3 dimensions reduced to 2 by virtue of symmetry) coupled to electron drift using high-resolution finite volume methods for hyperbolic systems [1] implemented in the software package CLAWPACK. The drift of electrons is determined by a self-consistent electric field, which we obtain by solving Poisson's equation by means of off-the-shelf solvers. Our model also includes a selection of chemical reactions that have a relevant effect on the electron density in air

Detection of muon bundles at large zenith angles

Energy Technology Data Exchange (ETDEWEB)

Aynutdinov, V.M.; Castellina, A.; Chernov, D.V.; Ezubchenko, A.A.; Fulgione, W.; Kindin, V.V.; Kokoulin, R.P.; Kompaniets, K.G.; Konovalov, A.A.; Mannocchi, G.; Petrukhin, A.A.; Rodin, Yu. N.; Saavedra, O.; Shutenko, V.V.; Trinchero, G.; Vernetto, S.; Vonsovsky, N.N.; Yanson, E.E.; Yashin, I.I

1999-03-01

The large area coordinate detector (DECOR) represents a multilayer system of plastic streamer tube chamber modules surrounding the Cherenkov water calorimeter NEVOD. Experimental data collected during the test expositions of first DECOR supermodules (8 vertical planes with 8.4 m{sup 2} working area) have been analysed, angular and spatial reconstruction accuracies have been estimated. The procedure of the selection of events corresponding to detection of parallel tracks (muon bundles originated in the atmosphere) is discussed.

Kinetics and dynamics of nanosecond streamer discharge in atmospheric-pressure gas bubble suspended in distilled water under saturated vapor pressure conditions

KAUST Repository

Sharma, Ashish

2016-09-08

We perform computational studies of nanosecond streamer discharges generated in helium bubbles immersed in distilled water under atmospheric pressure conditions. The model takes into account the presence of water vapor in the gas bubble for an accurate description of the discharge kinetics. We find that the dynamic characteristics of the streamer discharge are different at low and high positive trigger voltages with the axial streamer evolution dominant for low voltages and a surface hugging mode favored for high voltages. We also find a substantial difference in initiation, transition and evolution stages of discharge for positive and negative trigger voltages with the volumetric distribution of species in the streamer channel much more uniform for negative trigger voltages on account of the presence of multiple streamers. We observe that the presence of water vapor does not affect the breakdown voltage even for oversaturated conditions but significantly influences the composition of dominant species in the trail of the streamer as well as the flux of the dominant species on the bubble surface. © 2016 IOP Publishing Ltd.

Fast imaging of streamer propagation

International Nuclear Information System (INIS)

Veldhuizen, E.M. van; Baede, A.H.F.M.; Hayashi, D.; Rutgers, W.R.

2001-01-01

Recently measurement methods are becoming available to study the corona discharge in more detail. One of the most promising methods is laser-induced fluorescence to determine radical density. Recent improvements in CCD cameras makes it now possible to improve measurements of the discharge structure to a resolution of 1 ns in time and 10 μm in space. This paper shows the first results of the spontaneous emission of a point-to-plane corona discharge in air using such a camera. It clearly indicates that the 2-D approach for streamer propagation under these conditions is insufficient

Fast imaging of streamer propagation

Energy Technology Data Exchange (ETDEWEB)

Veldhuizen, E.M. van; Baede, A.H.F.M.; Hayashi, D.; Rutgers, W.R. [Eindhoven Univ. of Technology (Netherlands). Dept. of Applied Physics

2001-07-01

Recently measurement methods are becoming available to study the corona discharge in more detail. One of the most promising methods is laser-induced fluorescence to determine radical density. Recent improvements in CCD cameras makes it now possible to improve measurements of the discharge structure to a resolution of 1 ns in time and 10 {mu}m in space. This paper shows the first results of the spontaneous emission of a point-to-plane corona discharge in air using such a camera. It clearly indicates that the 2-D approach for streamer propagation under these conditions is insufficient.

Effects of SF$_{6}$ on the avalanche mode operation of a real-sized double-gap resistive plate chamber for the Compact Muon Solenoid experiment

CERN Document Server

Ahn Sung Hwan; Hong, B; Hong, S J; Ito, M; Kim, B I; Kim, J H; Kim, Y J; Kim, Y U; Koo, D G; Lee, H W; Lee, K B; Lee, K S; Lee, S J; Lim, J K; Moon, D H; Nam, S K; Park, S; Park, W J; Rhee, J T; Ryu, M S; Shim, H H; Sim, K S; Kang, T I

2005-01-01

We present the design and the test, results for a real-sized prototype resistive plate chamber by using cosmic-ray muons for the forward region of the Compact Muon Solenoid (CMS) experiment at the Large Hadron Collider (LHC). In particular, we investigate the effects of adding SF/sub 6/ to the gas mixture for the avalanche mode operation of a resistive plate chamber. A small fraction of SF/sub 6/ is very effective in suppressing streamer signals in a resistive plate chamber. The shapes of the muon detection efficiency and the muon cluster size remain similar, but are shifted to higher operating voltage by SF/sub 6/. The noise cluster rate and size are not influenced by SF/sub 6/.

Simulation of subnanosecond streamers in atmospheric-pressure air: Effects of polarity of applied voltage pulse

Energy Technology Data Exchange (ETDEWEB)

Babaeva, N. Yu.; Naidis, G. V. [Joint Institute for High Temperatures, Russian Academy of Sciences, Moscow 125412 (Russian Federation)

2016-08-15

Results of simulation of subnanosecond streamer propagation in corona gap configuration, obtained in the framework of 2D fluid model, are presented. Effects related with the polarity of a voltage pulse applied to the stressed electrode are discussed. It is argued that these effects (dependence of the discharge current and propagation velocity on the polarity of applied voltage) observed in experiments can be attributed to the difference in initial (preceding the streamer formation) distributions of charged species inside the gap. This difference can be caused by preionization (at negative polarity) of the gas inside the discharge gap by runaway electrons. Calculated streamers have large widths (up to 1 cm) and move with velocities in the range of 10{sup 9}–10{sup 10 }cm s{sup −1}, similar to experimental data.

Preliminary results of Resistive Plate Chambers operated with eco-friendly gas mixtures for application in the CMS experiment

CERN Document Server

Abbrescia, Marcello; Benussi, Luigi; Bianco, Stefano; Cauwenbergh, Simon Marc D; Ferrini, Mauro; Muhammad, Saleh; Passamontic, L; Pierluigi, Daniele; Piccolo, Davide; Primavera, Federica; Russo, Alessandro; Savianoc, G; Tytgat, Michael

2016-01-01

The operations of Resistive Plate Chambers in LHC experiments require F-based gases for optimal performance. Recent regulations demand the use of environmentally unfriendly F-based gases to be limited or banned. In view of the CMS experiment upgrade several tests are ongoing to measure the performance of the detector in terms of efficiency, streamer probability, induced charge and time resolution. Prototype chambers with readout pads and with the standard cms electronic setup are under test. In this talk preliminary results on performance of RPCs operated with a potential eco-friendly gas candidate 1,3,3,3-Tetrafluoropropene, commercially known as HFO-1234ze and with CO2 based gas mixtures are presented and discussed for the possible application in the CMS experiment.

Method of repairing incore structure and water sealing chamber

Energy Technology Data Exchange (ETDEWEB)

Kikuchi, Toshikazu; Sato, Sukenobu (Hitachi Nuclear Engineering Co. Ltd., Ibaraki (Japan)); Wada, Noriaki; Kurosawa, Koichi; Tsujimura, Hiroshi; Enomoto, Kunio.

1993-11-26

An incore-chamber main body comprises a guide tube, an insertion guide, an extensible arm, a device fixing mechanism, a gas supply pipe, a guide driving mechanism and an in-core chamber control device. The in-core chamber main body is installed and secured to an upper flange surface of a shroud. Reactor water is raised to a level below a flange of a reactor pressure vessel while supplying a dry gas from a gas supply pipe to make the inside of the shroud as a gas atmosphere. Subsequently, each of the devices is attached to the top end of the extensible arm, and the guide driving mechanism is operated by the in-core chamber control device to an aimed position for preventive maintenance or repair to conduct positioning and fixing by utilizing the guide tube and the insertion guide. This enables to conduct preventive maintenance or repair in a state where reactor water is present to the outside of the in-core reactor chamber while maintaining the in-core equipment in the gas atmosphere, thereby enabling to reduce operator's exposure dose. (I.N.).

Method of repairing incore structure and water sealing chamber

International Nuclear Information System (INIS)

Kikuchi, Toshikazu; Sato, Sukenobu; Wada, Noriaki; Kurosawa, Koichi; Tsujimura, Hiroshi; Enomoto, Kunio.

1993-01-01

An incore-chamber main body comprises a guide tube, an insertion guide, an extensible arm, a device fixing mechanism, a gas supply pipe, a guide driving mechanism and an in-core chamber control device. The in-core chamber main body is installed and secured to an upper flange surface of a shroud. Reactor water is raised to a level below a flange of a reactor pressure vessel while supplying a dry gas from a gas supply pipe to make the inside of the shroud as a gas atmosphere. Subsequently, each of the devices is attached to the top end of the extensible arm, and the guide driving mechanism is operated by the in-core chamber control device to an aimed position for preventive maintenance or repair to conduct positioning and fixing by utilizing the guide tube and the insertion guide. This enables to conduct preventive maintenance or repair in a state where reactor water is present to the outside of the in-core reactor chamber while maintaining the in-core equipment in the gas atmosphere, thereby enabling to reduce operator's exposure dose. (I.N.)

OBSERVATIONS OF A HYBRID DOUBLE-STREAMER/PSEUDOSTREAMER IN THE SOLAR CORONA

Energy Technology Data Exchange (ETDEWEB)

Rachmeler, L. A.; Seaton, D. B. [Royal Observatory of Belgium, Avenue Circulaire 3, 1180 Brussels (Belgium); Platten, S. J. [School of Mathematics and Statistics, University of St. Andrews, North Haugh, St. Andrews, Fife KY16 9SS (United Kingdom); Bethge, C. [Kiepenheuer-Institut für Sonnenphysik, Schöneckstrasse 6, D-79104 Freiburg (Germany); Yeates, A. R., E-mail: rachmeler@oma.be [Department of Mathematical Sciences, Durham University, Science Laboratories, South Road, Durham DH1 3LE (United Kingdom)

2014-05-20

We report on the first observation of a single hybrid magnetic structure that contains both a pseudostreamer and a double streamer. This structure was originally observed by the SWAP instrument on board the PROBA2 satellite between 2013 May 5 and 10. It consists of a pair of filament channels near the south pole of the Sun. On the western edge of the structure, the magnetic morphology above the filaments is that of a side-by-side double streamer, with open field between the two channels. On the eastern edge, the magnetic morphology is that of a coronal pseudostreamer without the central open field. We investigated this structure with multiple observations and modeling techniques. We describe the topology and dynamic consequences of such a unified structure.

The physics of pulsed streamer discharge in high pressure air and applications to engine techonologies

Science.gov (United States)

Lin, Yung-Hsu

The goal of this dissertation is to study high pressure streamers in air and apply it to diesel engine technologies. Nanosecond scale pulsed high voltage discharges in air/fuel mixtures can generate radicals which in turn have been shown to improve combustion efficiency in gasoline fueled internal combustion engines. We are exploring the possibility to extend such transient plasma generation and expected radical species generation to the range of pressures encountered in compression-ignition (diesel) engines having compression ratios of ˜20:1, thereby improving lean burning efficiency and extending the range of lean combustion. At the beginning of this dissertation, research into streamer discharges is reviewed. Then, we conducted experiments of streamer propagation at high pressures, calculated the streamer velocity based on both optical and electrical measurements, and the similarity law was checked by analyzing the streamer velocity as a function of the reduced electric field, E/P. Our results showed that the similarity law is invalid, and an empirical scaling factor, E/√P, is obtained and verified by dimensional analysis. The equation derived from the dimensional analysis will be beneficial to proper electrode and pulse generator design for transient plasma assisted internal engine experiments. Along with the high pressure study, we applied such technique on diesel engine to improve the fuel efficiency and exhaust treatment. We observed a small effect of transient plasma on peak pressure, which implied that transient plasma has the capability to improve the fuel consumption. In addition, the NO can be reduced effectively by the same technique and the energy cost is 30 eV per NO molecule.

Hexagon and stripe patterns in dielectric barrier streamer discharge

International Nuclear Information System (INIS)

Dong Lifang; He Yafeng; Yin Zengqian; Chai Zhifang

2004-01-01

We present a specially designed dielectric barrier discharge (DBD) system for the study of pattern formation. Hexagon and stripe patterns have been observed in a streamer discharge in a DBD for the first time. The phase diagram of pattern types as a function of applied voltage is given

Resistive Plate Chamber Performance During the CMS Magnet Test Cosmic Challenge

CERN Document Server

Trentadue, R

2008-01-01

The CMS detector at the CERN Large Hadron Collider (LHC) is equipped with a redundant muon system based on Drift Tubes Chambers (barrel region) and Cathode Strip Chamber (endcap region), and Resistive Plate Chamber (RPC). During the summer and fall 2006 a first integrated test of an entire CMS slice was performed at the SX5 experimental surface hall. The RPC chambers were operated with cosmic rays. The results on the RPC performance are reported.

Conceptual design of low activation target chamber and components for the National Ignition Facility

International Nuclear Information System (INIS)

Streckert, H.H.; Schultz, K.R.; Sager, G.T.; Kantner, R.D.

1996-01-01

The baseline design for the target chamber and chamber components for the National Ignition Facility (NIF) consists of aluminum alloy structural material. Low activation composite chamber and components have important advantages including enhanced environmental and safety characteristics and improved accessibility due to reduced neutron-induced radioactivity. A low activation chamber can be fabricated from carbon fiber reinforced epoxy using thick wall laminate technology similar to submarine bow dome fabrication for the U.S. Navy. A risk assessment analysis indicates that a composite chamber has a reasonably high probability of success, but that an aluminum alloy chamber represents a lower risk. Use of low activation composite materials for several chamber components such as the final optics assemblies, the target positioner and inserter, the diagnostics manipulator tubes, and the optics beam tubes would offer an opportunity to make significant reductions in post-shot radiation dose rate with smaller, less immediate impact on the NIF design. 7 refs., 3 figs

Multisource waveform inversion of marine streamer data using normalized wavefield

KAUST Repository

Choi, Yun Seok; Alkhalifah, Tariq Ali

2013-01-01

Multisource full-waveform inversion based on the L1- and L2-norm objective functions cannot be applied to marine streamer data because it does not take into account the unmatched acquisition geometries between the observed and modeled data. To apply

Streamlined Calibration of the ATLAS Muon Spectrometer Precision Chambers

CERN Document Server

Levin, DS; The ATLAS collaboration; Dai, T; Diehl, EB; Ferretti, C; Hindes, JM; Zhou, B

2009-01-01

The ATLAS Muon Spectrometer is comprised of nearly 1200 optically Monitored Drifttube Chambers (MDTs) containing 354,000 aluminum drift tubes. The chambers are configured in barrel and endcap regions. The momentum resolution required for the LHC physics reach (dp/p = 3% and 10% at 100 GeV and 1 TeV) demands rigorous MDT drift tube calibration with frequent updates. These calibrations (RT functions) convert the measured drift times to drift radii and are a critical component to the spectrometer performance. They are sensitive to the MDT gas composition: Ar 93%, CO2 7% at 3 bar, flowing through the detector at arate of 100,000 l hr−1. We report on the generation and application of Universal RT calibrations derived from an inline gas system monitor chamber. Results from ATLAS cosmic ray commissioning data are included. These Universal RTs are intended for muon track reconstuction in LHC startup phase.

Pulsed and streamer discharges in air above breakdown electric field

NARCIS (Netherlands)

A.B. Sun (Anbang); H.J. Teunissen (Jannis); U. M. Ebert (Ute)

2013-01-01

htmlabstractA 3D particle model is developed to investigate the streamer formation in electric fields above the breakdown threshold, in atmospheric air (1bar, 300 Kelvin). Adaptive particle management, adaptive mesh refinement and parallel computing techniques are used in the code. Photoionization

Performance of the ATLAS Precision Muon Chambers under LHC Operating Conditions

CERN Document Server

Deile, M.; Dubbert, J; Horvat, S; Kortner, O; Kroha, H; Manz, A; Mohrdieck, S; Rauscher, F; Richter, Robert; Staude, A

2004-01-01

For the muon spectrometer of the ATLAS detector at the large hadron collider (LHC), large drift chambers consisting of 6 to 8 layers of pressurized drift tubes are used for precision tracking covering an active area of 5000 m2 in the toroidal ?eld of superconducting air core magnets. The chambers have to provide a spatial resolution of 41 microns with Ar:CO2 (93:7) gas mixture at an absolute pressure of 3 bar and gas gain of 2?104. The environment in which the chambers will be operated is characterized by high neutron and background with counting rates of up to 100 per square cm and second. The resolution and efficiency of a chamber from the serial production for ATLAS has been investigated in a 100 GeV muon beam at photon irradiation rates as expected during LHC operation. A silicon strip detector telescope was used as external reference in the beam. The spatial resolution of a chamber is degraded by 4 ?m at the highest background rate. The detection e?ciency of the drift tubes is unchanged under irradiation...

Thin-walled beam tubes for the SIS. Construction and manufacturing

International Nuclear Information System (INIS)

Malwitz, E.

1985-06-01

The vacuum system of the SIS consists essentially of torus-shaped vacuum chamber with an annulus-circumference of 216 m which is composed by several beam-tube and chamber elements. In order to reach the desired final pressure of -11 mbar (5 . 10 -9 Pa) a heating of the whole vacuum system to 300 0 C is required. The beam tubes within magnets have regularly an elliptic tube cross section. Within bending magnets the beam tubes are curved in a plane through the large ellipse axis with a bending radius of 10 m. During the development work for the beam tubes within magnets to construction variants were studied until construction maturity. Generally thin-walled beam tubes with elliptic tube cross section are fabricated similarly to spring bellows as corrugated tubes. In this report however beam tubes with elliptic tube cross section are discussed the tube walls of which are smooth and stabilized against the atmospheric pressure by hard-soldered ribs. The report reproduces mainly the most important know how respectively serves as instruction for new constructions. Such beam tubes are planned for the dipole magnets and the quadrupole group consisting of two long quadrupoles, a short quadrupole, and a sextupole. (orig./HSI) [de

Particle based 3D modeling of positive streamer inception

NARCIS (Netherlands)

H.J. Teunissen (Jannis)

2012-01-01

htmlabstractIn this report we present a particle based 3D model for the study of streamer inception near positive electrodes in air. The particle code is of the PIC-MCC type and an electrode is included using the charge simulation method. An algorithm for the adaptive creation of super-particles is

Electric field determination in streamer discharges in air at atmospheric pressure

International Nuclear Information System (INIS)

Bonaventura, Z; Bourdon, A; Celestin, S; Pasko, V P

2011-01-01

The electric field in streamer discharges in air can be easily determined by the ratio of luminous intensities emitted by N 2 (C 3 Π u ) and N 2 + (B 2 Σ u + ) if the steady-state assumption of the emitting states is fully justified. At ground pressure, the steady-state condition is not fulfilled and it is demonstrated that its direct use to determine the local and instantaneous peak electric field in the streamer head may overestimate this field by a factor of 2. However, when spatial and time-integrated optical emissions (OEs) are considered, the reported results show that it is possible to formulate a correction factor in the framework of the steady-state approximation and to accurately determine the peak electric field in an air discharge at atmospheric pressure. A correction factor is defined as Γ = E s /E e , where E e is the estimated electric field and E s is the true peak electric field in the streamer head. It is shown that this correction stems from (i) the shift between the location of the peak electric field and the maximum excitation rate for N 2 (C 3 Π u ) and N 2 + (B 2 Σ u + ) as proposed by Naidis (2009 Phys. Rev. E 79 057401) and (ii) from the cylindrical geometry of the streamers as stated by Celestin and Pasko (2010 Geophys. Res. Lett. 37 L07804). For instantaneous OEs integrated over the whole radiating plasma volume, a correction factor of Γ ∼ 1.4 has to be used. For time-integrated OEs, the reported results show that the ratio of intensities can be used to derive the electric field in discharges if the time of integration is sufficiently long (i.e. at least longer than the longest characteristic lifetime of excited species) to have the time to collect all the light from the emitting zones of the streamer. For OEs recorded using slits (i.e. a window with a small width but a sufficiently large radial extension to contain the total radial extension of the discharge) the calculated correction factor is Γ ∼ 1.4. As for OEs observed

Quality control of ATLAS muon chambers

CERN Document Server

Fabich, Adrian

ATLAS is a general-purpose experiment for the future Large Hadron Collider (LHC) at CERN. Its Muon Spectrometer will require ∼ 5500m2 of precision tracking chambers to measure the muon tracks along a spectrometer arm of 5m to 15m length, embedded in a magnetic field of ∼ 0.5T. The precision tracking devices in the Muon System will be high pressure drift tubes (MDTs). Approximately 370,000 MDTs will be assembled into ∼ 1200 drift chambers. The performance of the MDT chambers is very much dependent on the mechanical quality of the chambers. The uniformity and stability of the performance can only be assured providing very high quality control during production. Gas tightness, high-voltage behaviour and dark currents are global parameters which are common to gas detectors. For all chambers, they will be tested immediately after the chamber assembly at every production site. Functional tests, for example radioactive source scans and cosmic-ray runs, will be performed in order to establish detailed performan...

Multisource full waveform inversion of marine streamer data with frequency selection

KAUST Repository

Huang, Yunsong; Schuster, Gerard T.

2013-01-01

Multisource migration with frequency selection is now extended to multisource full waveform inversion (FWI) of supergathers for marine streamer data. There are three advantages of this approach compared to conventional FWI for marine streamer data. 1. The multisource FWI method with frequency selection is computationally more efficient than conventional FWI. 2. A supergather requires more than an order of magnitude less storage than the the original data. 3. Frequency selection overcomes the acquisition mismatch between the observed data and the simulated multisource supergathers for marine data. This mismatch problem has prevented the efficient application of FWI to marine geometries in the space-time domain. Preliminary result of applying multisource FWI with frequency selection to a synthetic marine data set suggests it is at least four times more efficient than standard FWI.

Precise muon drift tube detectors for high background rate conditions

Energy Technology Data Exchange (ETDEWEB)

Engl, Albert

2011-08-04

The muon spectrometer of the ATLAS-experiment at the Large Hadron Collider consists of drift tube chambers, which provide the precise measurement of trajectories of traversing muons. In order to determine the momentum of the muons with high precision, the measurement of the position of the muon in a single tube has to be more accurate than {sigma}{<=}100 {mu}m. The large cross section of proton-proton-collisions and the high luminosity of the accelerator cause relevant background of neutrons and {gamma}s in the muon spectrometer. During the next decade a luminosity upgrade to 5.10{sup 34} cm{sup -2}s{sup -1} is planned, which will increase the background counting rates considerably. In this context this work deals with the further development of the existing drift chamber technology to provide the required accuracy of the position measurement under high background conditions. Two approaches of improving the drift tube chambers are described: - In regions of moderate background rates a faster and more linear drift gas can provide precise position measurement without changing the existing hardware. - At very high background rates drift tube chambers consisting of tubes with a diameter of 15 mm are a valuable candidate to substitute the CSC muon chambers. The single tube resolution of the gas mixture Ar:CO{sub 2}:N{sub 2} in the ratio of 96:3:1 Vol %, which is more linear and faster as the currently used drift gas Ar:CO{sub 2} in the ratio of 97:3 Vol %, was determined at the Cosmic Ray Measurement Facility at Garching and at high {gamma}-background counting rates at the Gamma Irradiation Facility at CERN. The alternative gas mixture shows similar resolution without background. At high background counting rates it shows better resolution as the standard gas. To analyse the data the various parts of the setup have to be aligned precisely to each other. The change to an alternative gas mixture allows the use of the existing hardware. The second approach are drift tubes

Preliminary results of Resistive Plate Chambers operated with eco-friendly gas mixtures for application in the CMS experiment

International Nuclear Information System (INIS)

Abbrescia, M.; Muhammad, S.; Saviano, G.; Auwegem, P. Van; Cauwenbergh, S.; Tytgat, M.; Benussi, L.; Bianco, S.; Passamonti, L.; Pierluigi, D.; Piccolo, D.; Primavera, F.; Russo, A.; Ferrini, M.

2016-01-01

The operations of Resistive Plate Chambers in LHC experiments require Fluorine based (F-based) gases for optimal performance. Recent European regulations demand the use of environmentally unfriendly F-based gases to be limited or banned. In view of the CMS experiment upgrade, several tests are ongoing to measure the performance of the detector with these new ecological gas mixtures, in terms of efficiency, streamer probability, induced charge and time resolution. Prototype chambers with readout pads and with the standard CMS electronic setup are under test. In this paper preliminary results on performance of RPCs operated with a potential eco-friendly gas candidate 1,3,3,3-Tetrafluoropropene, commercially known as HFO-1234ze, with CO 2 and CF 3 I based gas mixtures are presented and discussed for the possible application in the CMS experiment.

Preliminary results of Resistive Plate Chambers operated with eco-friendly gas mixtures for application in the CMS experiment

CERN Document Server

Abbrescia, M.

2016-01-01

The operations of Resistive Plate Chambers in LHC experiments require Fluorine based (F-based) gases for optimal performance. Recent European regulations demand the use of environmentally unfriendly F-based gases to be limited or banned. In view of the CMS experiment upgrade, several tests are ongoing to measure the performance of the detector with these new ecological gas mixtures, in terms of efficiency, streamer probability, induced charge and time resolution. Prototype chambers with readout pads and with the standard CMS electronic setup are under test. In this paper preliminary results on performance of RPCs operated with a potential eco-friendly gas candidate 1,3,3,3-Tetrafluoropropene, commercially known as HFO-1234ze, with CO2 and CF3I based gas mixtures are presented and discussed for the possible application in the CMS experiment.

Particle-in-cell modeling of streamer branching in CO2 gas

KAUST Repository

Levko, Dmitry; Pachuilo, Michael; Raja, Laxminarayan L

2017-01-01

The mechanism of streamer branching remains one of the unsolved problems of low-temperature plasma physics. The understanding of this phenomenon requires very high-fidelity models that include, for instance, the kinetic description of electrons

Transfer of a cold atmospheric pressure plasma jet through a long flexible plastic tube

International Nuclear Information System (INIS)

Kostov, Konstantin G; Prysiazhnyi, Vadym; Honda, Roberto Y; Machida, Munemasa

2015-01-01

This work proposes an experimental configuration for the generation of a cold atmospheric pressure plasma jet at the downstream end of a long flexible plastic tube. The device consists of a cylindrical dielectric chamber where an insulated metal rod that serves as high-voltage electrode is inserted. The chamber is connected to a long (up to 4 m) commercial flexible plastic tube, equipped with a thin floating Cu wire. The wire penetrates a few mm inside the discharge chamber, passes freely (with no special support) along the plastic tube and terminates a few millimeters before the tube end. The system is flushed with Ar and the dielectric barrier discharge (DBD) is ignited inside the dielectric chamber by a low frequency ac power supply. The gas flow is guided by the plastic tube while the metal wire, when in contact with the plasma inside the DBD reactor, acquires plasma potential. There is no discharge inside the plastic tube, however an Ar plasma jet can be extracted from the downstream tube end. The jet obtained by this method is cold enough to be put in direct contact with human skin without an electric shock. Therefore, by using this approach an Ar plasma jet can be generated at the tip of a long plastic tube far from the high-voltage discharge region, which provides the safe operation conditions and device flexibility required for medical treatment. (paper)

Fully kinetic particle simulations of high pressure streamer propagation

Science.gov (United States)

Rose, David; Welch, Dale; Thoma, Carsten; Clark, Robert

2012-10-01

Streamer and leader formation in high pressure devices is a dynamic process involving a hierarchy of physical phenomena. These include elastic and inelastic particle collisions in the gas, radiation generation, transport and absorption, and electrode interactions. We have performed 2D and 3D fully EM implicit particle-in-cell simulation model of gas breakdown leading to streamer formation under DC and RF fields. The model uses a Monte Carlo treatment for all particle interactions and includes discrete photon generation, transport, and absorption for ultra-violet and soft x-ray radiation. Central to the realization of this fully kinetic particle treatment is an algorithm [D. R. Welch, et al., J. Comp. Phys. 227, 143 (2007)] that manages the total particle count by species while preserving the local momentum distribution functions and conserving charge. These models are being applied to the analysis of high-pressure gas switches [D. V. Rose, et al., Phys. Plasmas 18, 093501 (2011)] and gas-filled RF accelerator cavities [D. V. Rose, et al. Proc. IPAC12, to appear].

Latest results on the performance of the multigap resistive plate chamber used for the ALICE TOF

CERN Document Server

Akindinov, A; Anselmo, F; Antonioli, P; Basile, M; Cara Romeo, G; Cifarelli, Luisa; Cindolo, F; Cosenza, F; D'Antone, I; De Caro, A; De Pasquale, S; Di Bartolomeo, A; Fusco-Girard, M; Golovine, V; Guerzoni, M; Guida, M; Hatzifotiadou, D; Kaidalov, A B; Kim, D H; Kim, D W; Kisselev, S M; Laurenti, G; Lioublev, E; Lee, K; Lee, S C; Luvisetto, M L; Margotti, A; Martemyanov, A N; Massera, F; Meneghini, S; Michinelli, R; Nania, R; Otiougova, P; Pancaldi, G; Pesci, A; Pilastrini, R; Pinazza, O; Polozov, P A; Rizzi, M; Scapparone, E; Scioli, G; Sellitto, S B; Semeria, F; Serra, S; Smirnitsky, A V; Tchoumakov, M M; Ugolini, E; Usenko, E; Valenti, G; Voloshin, K G; Williams, M C S; Zagreev, B V; Zampolli, C; Zichichi, A; Zucchini, A; Zuffa, M

2004-01-01

For the identification of particles in the momentum range 0.5-2.5 GeV /c, the ALICE experiment uses a Time Of Flight array consisting of Multigap Resistive Plate Chambers (MRPC) in the form of long strips. The design of the detector elements is as follows: double stack MRPCs with glass resistive plates and 5 gas gaps of 250 mum per stack. The latest results on the performance of these MRPCs are presented. Typical values of time resolution sigma are better than 50 ps, with an efficiency of 99.9% and a long, more than 1.5kV, streamer-free plateau.

Monitored Drift Chambers in the ATLAS Detector

CERN Multimedia

Herten, G

Monitored Drift Chambers (MDT) are used in the ATLAS Detector to measure the momentum of high energy muons. They consist of drift tubes, which are filled with an Ar-CO2 gas mixture at 3 bar gas pressure. About 1200 drift chambers are required for ATLAS. They are up to 6 m long. Nevertheless the position of every wire needs to be known with a precision of 20 µm within a chamber. In addition, optical alignment sensors are required to measure the relative position of adjacent chambers with a precision of 30µm. This gigantic task seems impossible at first instance. Indeed it took many years of R&D to invent the right tools and methods before the first chamber could be built according to specifications. Today, at the time when 50% of the chambers have been produced, we are confident that the goal for ATLAS can be reached. The mechanical precision of the chambers could be verified with the x-ray tomograph at CERN. This ingenious device, developed for the MDT system, is able to measure the wire position insid...

The effect of temperature on pulsed positive streamer discharges in air over the range 292 K–1438 K

Science.gov (United States)

Ono, Ryo; Ishikawa, Yuta

2018-05-01

The effect of temperature on pulsed positive streamer discharges in air is measured by comparing atmospheric-pressure, high-temperature discharges with low-pressure, room-temperature discharges at the same air densities n and discharge voltages. Both discharges have the same reduced electric field E/n, so the differences between the two discharges only depend on the temperature, which is varied from 292 K to 1438 K. Temperature affects the discharge pulse energy most significantly; at 1438 K, the energy of an atmospheric-pressure discharge pulse is approximately 30 times larger than that of the corresponding 20.5 kPa, room-temperature discharge. Temperature also affects the shapes of the streamers when K, but no significant effect is observed for K. There is also no significant temperature effect on the spatially integrated intensity of N2(C–B) emission. However, temperature strongly affects the ratio of the integrated emission intensity to the discharge energy. No effect of the temperature is observed on the propagation velocity of the primary streamer or on the length of the secondary streamer.

Indication chamber of liquid metal fired steam generators with double wall for heat transfer

International Nuclear Information System (INIS)

Matal, O.; Martoch, J.

1982-01-01

The double wall of the steam generator consists of inner and outer tubes anchored in a tube plate. Between the tubes are indication spaces which end in recesses formed at least in one of the tube plates and coaxial with the outer tubes. The recesses interconnected with channels form the indication chamber to which is connected at least one sensor of the alarm signal equipment. (B.S.)

Design, construction, prototype tests and performance of a vertex chamber for the MAC detector

International Nuclear Information System (INIS)

Ash, W.W.; Band, H.R.; Bloom, E.D.; Bosman, M.; Camporesi, T.; Chadwick, G.B.; Delfino, M.C.; De Sangro, R.; Ford, W.T.; Gettner, M.W.; Goderre, G.P.; Godfrey, G.L.; Groom, D.E.; Hurst, R.B.; Johnson, J.R.; Lau, K.H.; Lavine, T.L.; Leedy, R.E.; Lippi, I.; Maruyama, T.; Messner, R.L.; Moromisato, J.H.; Moss, L.J.; Muller, F.; Nelson, H.N.; Peruzzi, I.; Piccolo, M.; Prepost, R.; Pyrlik, J.; Qi, N.; Read, A.L. Jr.; Ritson, D.M.; Rosenberg, L.J.; Shambroom, W.D.; Sleeman, J.C.; Smith, J.G.; Venuti, J.P.; Verdini, P.G.; Goeler, E. von; Wald, H.B.; Weinstein, R.; Wiser, D.E.; Zdarko, R.W.; Istituto Nazionale di Fisica Nucleare, Frascati; Houston Univ., TX; Northeastern Univ., Boston, MA; Stanford Univ., CA; Stanford Linear Accelerator Center, CA; Utah Univ., Salt Lake City; Wisconsin Univ., Madison

1987-01-01

The design considerations, construction techniques, prototype tests and performance characteristics of a pressurized drift chamber used in the MAC detector at PEP are described. The chamber consists of 324 aluminized mylar tubes of 6.9 mm diameter with wall thickness of 100 μm. With appropriate shielding it operates successfully at 4.6 cm from the beam line. It was simple to construct and was configured to permit any malfunctioning tubes to be remotely disconnected without affecting operation. The chamber operated without problems for two years in the PEP environmental with a gas mixture of 49.5% argon, 49.5% CO 2 , 1% CH 4 , at 4 atm absolute pressure. The mean spatial resolution averaged over all tubes was 45 μm. The time to distance relation for this gas mixture, along with the geometric positioning of individual wires relative to the central tracking chamber, was obtained with data from Bhabha scattering events. We also describe resolution studies performed with a prototype chamber in a SLAC test beam. A wide range of gases, gas pressures, and electronic parameters were explored. These studies proved that resolutions in the 10-50 μm range were possible. Our experience demonstrates that chambers of this type provide high precision tracking and are particularly suited for operation in regions with difficult physical access and/or high ambient radiation levels. (orig.)

Design, construction, prototype tests and performance of a vertex chamber for the MAC detector

Science.gov (United States)

Ash, W. W.; Band, H. R.; Bloom, E. D.; Bosman, M.; Camporesi, T.; Chadwick, G. B.; Delfino, M. C.; De Sangro, R.; Ford, W. T.; Gettner, M. W.; Goderre, G. P.; Godfrey, G. L.; Groom, D. E.; Hurst, R. B.; Johnson, J. R.; Lau, K. H.; Lavine, T. L.; Leedy, R. E.; Lippi, I.; Maruyama, T.; Messner, R. L.; Moromisato, J. H.; Moss, L. J.; Muller, F.; Nelson, H. N.; Peruzzi, I.; Piccolo, M.; Prepost, R.; Pyrlik, J.; Qi, N.; Read, A. L.; Ritson, D. M.; Rosenberg, L. J.; Shambroom, W. D.; Sleeman, J. C.; Smith, J. G.; Venuti, J. P.; Verdini, P. G.; Von Goeler, E.; Wald, H. B.; Weinstein, R.; Wiser, D. E.; Zdarko, R. W.

1987-11-01

The design considerations, construction techniques, prototype tests and performance characteristics of a pressurized drift chamber used in the MAC detector at PEP are described. The chamber consists of 324 aluminized mylar tubes of 6.9 mm diameter with wall thickness of 100 μm. With appropriate shielding it operates successfully at 4.6 cm from the beam line. It was simple to construct and was configured to permit any malfunctioning tubes to be remotely disconnected without affecting operation. The chamber operated without problems for two years in the PEP environment with a gas mixture of 49.5% argon, 49.5% CO 2, 1% CH 4, at 4 atm absolute pressure. The mean spatial resolution averaged over all tubes was 45 μm. The time to distance relation for this gas mixture, along with the geometric positioning of individual wires relative to the central tracking chamber, was obtained with data from Bhabha scattering events. We also describe resolution studies performed with a prototype chamber in a SLAC test beam. A wide range of gases, gas pressures, and electronic parameters were explored. These studies proved that resolutions in the 10-50 μm range were possible. Our experience demonstrates that chambers of this type provide high precision tracking and are particularly suited for operation in regions with difficult physical access and/or high ambient radiation levels.

Quenching gases for limited-streamer operation

Energy Technology Data Exchange (ETDEWEB)

Rapp, P

1986-04-01

Charge spectra and efficiencies of the limited-streamer mode are presented as a function of quencher fraction and high voltage for several gas mixes. The goal was to find a working gas of low hydrocarbon content in order to relieve safety concerns about the flammability of the large gas volume contained in the hadron calorimeter of the OPAL detector at LEP. No suitable low-hydrocarbon quenching mix is found. The charge spectra from these quenchers develop secondary peaks and long tails as full efficiency is approached, leading to catastrophic breakdown near the onset of full efficiency.

Quenching gases for limited-streamer operation

Energy Technology Data Exchange (ETDEWEB)

Rapp, P

1986-04-01

Charge spectra and efficiencies of the limited-streamer mode are presented as a function of quencher fraction and high voltage for several gas mixes. The goal was to find a working gas of low hydrocarbon content in order to relieve safety concerns about the flammability of the large gas volume contained in the hadron calorimeter of the OPAL detector at LEP. No suitable low-hydrocarbon quenching mix is found. The charge spectra from these quenchers develop secondary peaks and long tails as full efficiency is approached, leading to catastrophic breakdown near the onset of full efficiency. (orig.).

New ideas and developments in calorimetry

International Nuclear Information System (INIS)

Gordon, H.A.

1981-01-01

The challenges for calorimeter performance in the next decade are reviewed. Some new ideas for calorimeters are described: (1) the test of a parallel plate calorimeter; (2) the use of vacuum photodiodes for calorimeters operating in a magnetic field; (3) the attempt to build high pressure gas sealed tubes as ion chambers in hadron calorimeters; (4) the progress in the attempt to mold plastic loaded with heavy metal for the inert material in gas calorimeters; and (5) the use of the limited streamer mode in calorimeters

An Extreme-ultraviolet Wave Generating Upward Secondary Waves in a Streamer-like Solar Structure

Science.gov (United States)

Zheng, Ruisheng; Chen, Yao; Feng, Shiwei; Wang, Bing; Song, Hongqiang

2018-05-01

Extreme-ultraviolet (EUV) waves, spectacular horizontally propagating disturbances in the low solar corona, always trigger horizontal secondary waves (SWs) when they encounter the ambient coronal structure. We present the first example of upward SWs in a streamer-like structure after the passing of an EUV wave. This event occurred on 2017 June 1. The EUV wave happened during a typical solar eruption including a filament eruption, a coronal mass ejection (CME), and a C6.6 flare. The EUV wave was associated with quasi-periodic fast propagating (QFP) wave trains and a type II radio burst that represented the existence of a coronal shock. The EUV wave had a fast initial velocity of ∼1000 km s‑1, comparable to high speeds of the shock and the QFP wave trains. Intriguingly, upward SWs rose slowly (∼80 km s‑1) in the streamer-like structure after the sweeping of the EUV wave. The upward SWs seemed to originate from limb brightenings that were caused by the EUV wave. All of the results show that the EUV wave is a fast-mode magnetohydrodynamic (MHD) shock wave, likely triggered by the flare impulses. We suggest that part of the EUV wave was probably trapped in the closed magnetic fields of the streamer-like structure, and upward SWs possibly resulted from the release of slow-mode trapped waves. It is believed that the interplay of the strong compression of the coronal shock and the configuration of the streamer-like structure is crucial for the formation of upward SWs.

Heat exchanger tube tool

International Nuclear Information System (INIS)

Gugel, G.

1976-01-01

Certain types of heat-exchangers have tubes opening through a tube sheet to a manifold having an access opening offset from alignment with the tube ends. A tool for inserting a device, such as for inspection or repair, is provided for use in such instances. The tool is formed by a flexible guide tube insertable through the access opening and having an inner end provided with a connector for connection with the opening of the tube in which the device is to be inserted, and an outer end which remains outside of the chamber, the guide tube having adequate length for this arrangement. A flexible transport hose for internally transporting the device slides inside of the guide tube. This hose is long enough to slide through the guide tube, into the heat-exchanger tube, and through the latter to the extent required for the use of the device. The guide tube must be bent to reach the end of the heat-exchanger tube and the latter may be constructed with a bend, the hose carrying anit-friction elements at interspaced locations along its length to make it possible for the hose to negotiate such bends while sliding to the location where the use of the device is required

The differences between storms driven by helmet streamer CIRs and storms driven by pseudostreamer CIRs

OpenAIRE

Borovsky, Joseph E.; Denton, Michael

2013-01-01

A corotating interaction region (CIR) is formed when fast coronal hole origin solar wind overtakes slow solar wind and forms a region of compressed plasma and magnetic field. The slow wind upstream of the coronal hole fast wind can be either of helmet streamer origin or pseudostreamer origin. For a collection of 125 CIR-driven geomagnetic storms, the slow wind ahead of each CIR is examined; for those storm not containing ejecta, each CIR is categorized as a helmet streamer CIR (74 of the 125 ...

Small-sized pump for the target chamber of the E-SUVI accelerator

International Nuclear Information System (INIS)

Borts, B.V.; Kravchenko, S.F.; Pisarev, G.V.; Rubashko, V.G.; Khorenko, V.K.

1980-01-01

The target chamber of the accelerator ESUVI is located at the high voltage end of the accelerating tube under the electrostatic generator conductor. The pumping out from the target chamber region has been performed through the accelerating tube its rate constituting 1.5 l/s which resulted in oxidation and contamination of the surface of irradiated targets in the course of the irradiation of chemically active materials. For obtaining high vacuum in a target chamber a small-size gettering-ionic pump of the ORBITRON type has been developed which operates in the autonomous mode. The pump pumping out rate in the pressure range 10 -5 -10 -7 mm Hg constitutes for air and nitrogen 20-25 l/s, ffor oxygen 30-40 l/s, for hydrogen 100-120 l/s. The pump weight without supply units is 2 kg. The pumps permits performing pressure indicator in the target chamber. Using the developed pump makes possible to decrease the target chamber pressure to 1x10 -6 mm Hg for active gases to 10 -8 -10 -9 mm Hg

Drift velocity monitoring of the CMS muon drift chambers

CERN Document Server

Sonnenschein, Lars

2010-01-01

The drift velocity in drift tubes of the CMS muon chambers is a key parameter for the muon track reconstruction and trigger. It needs to be monitored precisely in order to detect any deviation from its nominal value. A change in absolute pressure, a variation of the gas admixture or a contamination of the chamber gas by air affect the drift velocity. Furthermore the temperature and magnetic field influence its value. First data, taken with a dedicated Velocity Drift Chamber (VDC) built by RWTH Aachen IIIA are presented.

Ionizing potential waves and high-voltage breakdown streamers.

Science.gov (United States)

Albright, N. W.; Tidman, D. A.

1972-01-01

The structure of ionizing potential waves driven by a strong electric field in a dense gas is discussed. Negative breakdown waves are found to propagate with a velocity proportional to the electric field normal to the wavefront. This causes a curved ionizing potential wavefront to focus down into a filamentary structure, and may provide the reason why breakdown in dense gases propagates in the form of a narrow leader streamer instead of a broad wavefront.

Irradiation chamber for photoactivation patient treatment system

International Nuclear Information System (INIS)

Lee, K.H.; Troutner, V.H.; Goss, J.; King, M.J.

1988-01-01

A flat plate irradiation chamber is described for use in a patient treatment system for altering cells, including treating the cells with a photoactivatable agent and passing the cells and the agent through a field of photoactivating radiation whereby the agent is caused to be activated and to affect the cells. The agent and the cells are contained in the irradiation chamber during irradiation. The flat plate irradiation chamber comprises: a rigid top sheet matably joined with a rigid bottom sheet, forming therebetween a rigid serpentine pathway for conducting the cells through the field of radiation; and pump block means for holding tubing means in fluid communication with the serpentine pathway and adapted for engaging a peristaltic pump whereby rotation of the pump causes the cells to flow through the serpentine pathway, and wherein the chamber is removable from the system and disposable

Lifetime tests for MAC vertex chamber

International Nuclear Information System (INIS)

Nelson, H.N.

1986-07-01

A vertex chamber for MAC was proposed to increase precision in the measurement of the B hadron and tau lepton lifetimes. Thin-walled aluminized mylar drift tubes were used for detector elements. A study of radiation hardness was conducted under the conditions of the proposed design using different gases and different operating conditions

Branching of positive discharge streamers in air at varying pressures

NARCIS (Netherlands)

Briels, T.M.P.; Veldhuizen, van E.M.; Ebert, U.M.

2005-01-01

The formation of positive streamers in a 17-mm gap in air is studied at pressures varying in the range from 1010 to 100 mbar. An intensified charge coupled device camera is used to image the discharge. At high pressures, the discharge shows many branches, while at low pressure, fewer branches arise.

A study of the response of ionization chambers to mammography beams

International Nuclear Information System (INIS)

Kessler, G.; Burns, D.T.; Buermann, L.; Prez, L.A. de

2007-03-01

Some simulated mammography radiation beams have been established at the BIPM using a low-energy x-ray tube with a tungsten anode and molybdenum as a filter. The response of two ionization chambers of different types to these beams is compared with that obtained in mammography beams at the PTB and the NMi which were produced with x-ray tubes with molybdenum anodes and molybdenum filters. The relative differences between the chamber responses to these two different types of beams were less than 7 x 10 -3 which implies the uncertainty for the transfer of a calibration from one type of beam to the other. (authors)

Streamlined calibrations of the ATLAS precision muon chambers for initial LHC running

Energy Technology Data Exchange (ETDEWEB)

Amram, N. [Raymond and Beverly Sackler School of Physics and Astronomy, Tel-Aviv University, 69978 Tel Aviv (Israel); Ball, R. [Department of Physics, The University of Michigan, Ann Arbor, MI 48109-1120 (United States); Benhammou, Y.; Ben Moshe, M. [Raymond and Beverly Sackler School of Physics and Astronomy, Tel-Aviv University, 69978 Tel Aviv (Israel); Dai, T.; Diehl, E.B. [Department of Physics, The University of Michigan, Ann Arbor, MI 48109-1120 (United States); Dubbert, J. [Max-Planck-Institut fuer Physik, Werner-Heisenberg-Institut, Muenchen (Germany); Etzion, E., E-mail: erez@cern.ch [Raymond and Beverly Sackler School of Physics and Astronomy, Tel-Aviv University, 69978 Tel Aviv (Israel); Ferretti, C.; Gregory, J. [Department of Physics, The University of Michigan, Ann Arbor, MI 48109-1120 (United States); Haider, S. [CERN, CH-1211 Geneva 23 (Switzerland); Hindes, J.; Levin, D.S.; Manilow, E.; Thun, R.; Wilson, A.; Weaverdyck, C.; Wu, Y.; Yang, H.; Zhou, B. [Department of Physics, The University of Michigan, Ann Arbor, MI 48109-1120 (United States); and others

2012-04-11

The ATLAS Muon Spectrometer is designed to measure the momentum of muons with a resolution of dp/p=3% at 100 GeV and 10% at 1 TeV. For this task, the spectrometer employs 355,000 Monitored Drift Tubes (MDTs) arrayed in 1200 chambers. Calibration (RT) functions convert drift time measurements into tube-centered impact parameters for track segment reconstruction. RT functions depend on MDT environmental parameters and so must be appropriately calibrated for local chamber conditions. We report on the creation and application of a gas monitor system based calibration program for muon track reconstruction in the LHC startup phase.

Impedance analysis of the PEP-II vacuum chamber

International Nuclear Information System (INIS)

Ng, C.K.; Weiland, T.

1995-05-01

The PEP-II high energy ring (HER) vacuum chamber consists of a copper tube with periodically spaced pumping slots. The impedance of the vacuum chamber due to the slots is analyzed. Both narrow-band and broadband impedances are considered as well as longitudinal and transverse components thereof. It is found that although the broad-band impedance is tolerable, the narrow-band impedance may exceed the instability limit given by the natural damping with no feedback system on. Traveling wave modes in the chamber are the major source of this high value narrow-band impedance. We also study the dependences of the impedance on the slot length and the geometrical cross section

Behaviour of OH radicals in an atmospheric-pressure streamer discharge studied by two-dimensional numerical simulation

International Nuclear Information System (INIS)

Komuro, Atsushi; Ono, Ryo; Oda, Tetsuji

2013-01-01

The production process of OH radicals in an atmospheric-pressure streamer discharge is studied. A streamer discharge model is developed to analyse the characteristics of a pulsed positive streamer discharge in point-to-plane electrodes filled with humid air at atmospheric pressure. The results indicate that the behaviour of OH radicals in and after the discharge pulse is characterized by three reaction processes: ‘OH-production’, ‘OH-cycle’ and ‘OH-recombination’. The first process of OH-production includes dissociation reactions of H 2 O with O( 1 D) and N 2 (a' 1 Σ u - ), which are the main production processes of OH in the discharge. Immediately after the OH-production process, the OH radicals are destroyed by a reaction with O( 3 P) to form O 2 and H. Then the subsequent reactions produce OH again through the reaction of H + HO 2 , which is the OH-cycle process. Finally, the OH radicals are consumed by the OH-recombination process. (paper)

Calibration of PKA meters against ion chambers of two geometries

International Nuclear Information System (INIS)

Almeida Junior, Jose N.; Terini, Ricardo A.; Pereira, Marco A.G.; Herdade, Silvio B.

2011-01-01

Kerma-area product (KAP or PKA) is a quantity that is independent of the distance to the X-ray tube focal spot and that can be used in radiological exams to assess the effective dose in patients. Clinical KAP meters are generally fixed in tube output and they are usually calibrated on-site by measuring the air kerma with an ion chamber and by evaluating the irradiated area by means of a radiographic image. Recently, a device was marketed (PDC, Patient Dose Calibrator, Radcal Co.), which was designed for calibrating clinical KAP meters with traceability to a standard laboratory. This paper presents a metrological evaluation of two methods that can be used in standard laboratories for the calibration of this device, namely, against a reference 30 cc ionization chamber or a reference parallel plates monitor chamber. Lower energy dependence was also obtained when the PDC calibration was made with the monitor chamber. Results are also shown of applying the PDC in hospital environment to the cross calibration of a clinical KAP meter from a radiology equipment. Results confirm lower energy dependence of the PDC relatively to the tested clinical meter. (author)

Single-electron pulse-height spectra in thin-gap parallel-plate chambers

CERN Document Server

Fonte, Paulo J R; Peskov, Vladimir; Policarpo, Armando

1999-01-01

Single-electron pulse-height spectra were measured in 0.6 and 1.2 mm parallel-plate chambers developed for the TOF system of the ALICE /LHC-HI experiment. Mixtures of Ar with ethane, isobutane, and SF/sub 6/ were studied. The observed spectrum shows a clear peak for all gases, suggesting efficient single-electron detection in thin parallel-plate structures. The pulse-height spectrum can be described by the weighted sum of an exponential and a Polya distribution, the Polya contribution becoming more important at higher gains. Additionally, it was found that the maximum gain, above 10/sup 6/, is limited by the appearance of streamers and depends weakly on the gas composition. The suitability of each mixture for single-electron detection is also quantitatively assessed. (8 refs).

Multi-source waveform inversion of marine streamer data using the normalized wavefield

KAUST Repository

Choi, Yun Seok; Alkhalifah, Tariq Ali

2012-01-01

Even though the encoded multi-source approach dramatically reduces the computational cost of waveform inversion, it is generally not applicable to marine streamer data. This is because the simultaneous-sources modeled data cannot be muted to comply

High precision straw tube chamber with cathode readout

International Nuclear Information System (INIS)

Bychkov, V.N.; Golutvin, I.A.; Ershov, Yu.V.

1992-01-01

The high precision straw chamber with cathode readout was constructed and investigated. The 10 mm straws were made of aluminized mylar strip with transparent longitudinal window. The X coordinate information has been taken from the cathode strips as induced charges and investigated via centroid method. The spatial resolution σ=120 μm has been obtained with signal/noise ratio about 60. The possible ways for improving the signal/noise ratio have been described. 7 refs.; 8 figs

A Series of Jets that Drove Streamer-Puff CMEs from Giant Active Region of 2014

Science.gov (United States)

Panesar, Navdeep K.; Sterling, Alphonse C.; Moore, Ronald L.

2016-01-01

We investigate characteristics of solar coronal jets that originated from active region NOAA 12192 and produced coronal mass ejections (CMEs). This active region produced many non­-jet major flare eruptions (X and M class) that made no CME. A multitude of jets occurred from the southeast edge of the active region, and in contrast to the major-­flare eruptions in the core, six of these jets resulted in CMEs. Our jet observations are from SDO/AIA EUV channels and from Hinode/XRT, and CME observations are from the SOHO/LASCO C2 coronograph. Each jet-­driven CME was relatively slow-­moving (approx. 200 - 300 km/s) compared to most CMEs; had angular width (20deg - 50deg) comparable to that of the streamer base; and was of the "streamer­-puff" variety, whereby a pre-existing streamer was transiently inflated but not removed (blown out) by the passage of the CME. Much of the chromospheric-­temperature plasma of the jets producing the CMEs escaped from the Sun, whereas relatively more of the chromospheric plasma in the non-CME-producing jets fell back to the solar surface. We also found that the CME-producing jets tended to be faster in speed and longer in duration than the non-CME-­producing jets. We expect that the jets result from eruptions of mini-filaments. We further propose that the CMEs are driven by magnetic twist injected into streamer-­base coronal loops when erupting twisted mini-filament field reconnects with the ambient field at the foot of those loops.

Internal current generation in respiration chambers

Science.gov (United States)

Saborowski, R.; Buchholz, F.

1998-06-01

A technical device generating a constant and directed current within a sealed respiration chamber is described. It does not involve any external pumps or tubing. This system is easy to handle, and improved the maintenance of rheotactic pelagic species like the Northern krill ( Meganyctiphanes norvegica, Crustacea) or small fishes ( Gasterosteus aculeatus) under experimental conditions.

Method and apparatus for testing closed-end tubes in heat exchangers of nuclear reactors and the like

International Nuclear Information System (INIS)

Seyd, G.; Bergbauer, A.; Paulsen, U.

1975-01-01

A description is given of a test stopper which is insertable into a tube closed at one end for testing the tightness of the tube with a fluid under pressure, the tube being in a heat exchanger of a nuclear reactor or the like. The test stopper includes a tubular outer jacket that is expandable outwardly to tightly seat the stopper in the tube. The stopper also has front and back end-face members joined to the ends of the outer jacket to define a closed space within the jacket. With the stopper inserted into the tube, the front end-face member and the closed end portion of the tube define a closed inner region of the tube. An inner tubular member, disposed within the outer jacket, partitions the closed space within the jacket into an annular outer chamber and a cylindrical inner chamber. A pressure-fluid supply selectively supplies fluid to the chambers. The outer jacket expands in response to fluid admitted to the annular chamber and the front end-face member has a through bore to admit fluid under pressure to the inner region of the tube. A method of testing of such a tube with a fluid under pressure includes inserting the test stopper into the tube and then expanding the outer jacket of the stopper to seat the stopper firmly in the tube. A fluid under pressure is directed through the stopper and into the closed region defined by the front end-face member of the stopper and the closed end portion of the tube. The pressure of the fluid introduced into this closed region is monitored for detecting a leak in the closed-end tube

Drained Lava Tubes and Lobes From Eocretaceous Paraná-Etendeka Province, Brazil

Science.gov (United States)

Waichel, B. L.; Lima, E. F. D.; Mouro, L. D.; Briske, D. R.; Tratz, E. B.

2017-12-01

The identification of lava tubes in continental flood basalt provinces (CFBP) is difficult and reports of preserved drained tubes and lobes are rare. The large extension of CFBP must be related to an efficient transport of lava and tubes are the most efficient mechanism to transport lava in insulated pathways, like observed in modern volcanic fields. Looking for caves in the central portion of Paraná-Etendeka Province, we discovered drained lava tubes (4) and lobes (6) in a volcanic sequence constituted by pahoehoe flows. Lava tubes are: Casa de Pedra, Perau Branco, Dal Pae and Pinhão. The Casa de Pedra tube system is composed of two principal chambers with similar dimensions, reaching up to 10 m long and 4.0 m high connected by a narrow passage. The general form of the chamber is hemispherical, with re-entrances of ellipsoidal shape probably formed by small lava lobes and collapse structures in the roof. The second chamber is connected with three secondary lava tubes. Columns in the cave are formed when the flowing lava separates in two lava channels that join again further down the system, forming and anastomosing tube network. Lateral lava benches and lava drainings at the walls are observed in secondary tubes. The general lava flow is to SW. The Perau Branco system is composed of five tubes with ellipsoidal openings. The main features are the long tubes that emerge from the small flattened chambers. One tube is more than 20 m long, with alternating circular and flattened ellipsoidal sections. The general lava flow is to NE. Pinhão tube is spherical with 3 meters diameter and 15 m long, with lava flow orientation to NW. This tube has a bottleneck shape with linings (up to 3 cm thick), which are observed in the roof and walls. Dal Pae Tube is 10 m long with an ellipsoidal opening, bottleneck shape and orientation to NE. The lava flow directions measured in the tubes is to SW (Casa de Pedra, Pinhão) and NE (Perau Branco, Dal Pae) and this pattern is related to

Latest results on the performance of the multigap resistive plate chamber used for the ALICE TOF

International Nuclear Information System (INIS)

Akindinov, A.N.; Alici, A.; Anselmo, F.

2004-01-01

For the identification of particles in the momentum range 0.5-2.5GeV/c, the ALICE experiment uses a Time Of Flight array consisting of Multigap Resistive Plate Chambers (MRPC) in the form of long strips. The design of the detector elements is as follows : double stack MRPCs with glass resistive plates and 5 gas gaps of 250μm per stack. The latest results on the performance of these MRPCs are presented. Typical values of time resolution σ are better than 50ps, with an efficiency of 99.9% and a long, more than 1.5kV, streamer-free plateau

Pseudo-spectral 3D simulations of streamers with adaptively refined grids

NARCIS (Netherlands)

Luque, A.; Ebert, U.; Montijn, C.; Hundsdorfer, W.; Schmidt, J.; Simek, M.; Pekarek, S.; Prukner, V.

2007-01-01

A three-dimensional code for the simulation of streamers is introduced. The code is based on a fluid model for oxygen-nitrogen mixtures that includes drift, diffusion and attachement of electrons and creation of new charge carriers through impact ionization and photo-ionization. The electric field

Comparison of Positive Streamers in Liquid Dielectrics with and without Nanoparticles Simulated with Finite-Element Software

Directory of Open Access Journals (Sweden)

Juan Velasco

2018-02-01

Full Text Available In this paper, a comparison of positive streamer diffusion propagation is carried out in three configurations of oil transformers: mineral transformer oil, mineral oil with solid dielectric barriers, and a nanofluid. The results have been solved using a finite-element method with a two-dimensional (2D axi-symmetric space dimension selected. Additionally, previous results from other research has been reviewed to compare the results obtained. As expected, it is confirmed that the nanoparticles improve the dielectric properties of the mineral oil. In addition, it is observed that the dielectric solid blocks the propagation of the streamer when it is submerged with a horizontal orientation, thus perpendicular to the applied electric field. The computer used, with four cores (each 3.4 GHz and 16 GB of RAM, was not sufficient for performing the simulations of the models with great precision. However, with these first models, the tendency of the dielectric behavior of the oil was obtained for the three cases in which the streamer was acting through the transformer oil. The simulation of these models, in the future, in a supercomputer with a high performance in terms of RAM memory may allow us to predict, as an example, the best concentration of nanoparticles to retard the streamer inception. Finally, other dielectric issues will be predicted using these models, such as to analyze the advantages and drawbacks of the presence of dielectrics inside the oil transformer.

Loeb's and streamer-based mechanism for negative corona current pulses

International Nuclear Information System (INIS)

Vagnerova, L.; Skalny, J.D.; Cermak, M.

1998-01-01

The negative point-to-plane corona discharge in electronegative gaseous mixtures is studied experimentally and the basic mechanisms controlling the corona phenomena are discussed. The typical shapes of the current pulse waveforms observed in experiments with the nitrogen-freon mixtures are explained in terms of the theory by Loeb and of the positive-streamer-based model. (J.U.)

DC-driven plasma gun: self-oscillatory operation mode of atmospheric-pressure helium plasma jet comprised of repetitive streamer breakdowns

Science.gov (United States)

Wang, Xingxing; Shashurin, Alexey

2017-02-01

This paper presents and studies helium atmospheric pressure plasma jet comprised of a series of repetitive streamer breakdowns, which is driven by pure DC high voltage (self-oscillatory behavior). The repetition frequency of the breakdowns is governed by the geometry of discharge electrodes/surroundings and gas flow rate. Each next streamer is initiated when the electric field on the anode tip recovers after the previous breakdown and reaches the breakdown threshold value of about 2.5 kV cm-1. One type of the helium plasma gun designed using this operational principle is demonstrated. The gun operates on about 3 kV DC high voltage and is comprised of the series of the repetitive streamer breakdowns at a frequency of about 13 kHz.

Towards User-Friendly Spelling with an Auditory Brain-Computer Interface: The CharStreamer Paradigm

Science.gov (United States)

Höhne, Johannes; Tangermann, Michael

2014-01-01

Realizing the decoding of brain signals into control commands, brain-computer interfaces (BCI) aim to establish an alternative communication pathway for locked-in patients. In contrast to most visual BCI approaches which use event-related potentials (ERP) of the electroencephalogram, auditory BCI systems are challenged with ERP responses, which are less class-discriminant between attended and unattended stimuli. Furthermore, these auditory approaches have more complex interfaces which imposes a substantial workload on their users. Aiming for a maximally user-friendly spelling interface, this study introduces a novel auditory paradigm: “CharStreamer”. The speller can be used with an instruction as simple as “please attend to what you want to spell”. The stimuli of CharStreamer comprise 30 spoken sounds of letters and actions. As each of them is represented by the sound of itself and not by an artificial substitute, it can be selected in a one-step procedure. The mental mapping effort (sound stimuli to actions) is thus minimized. Usability is further accounted for by an alphabetical stimulus presentation: contrary to random presentation orders, the user can foresee the presentation time of the target letter sound. Healthy, normal hearing users (n = 10) of the CharStreamer paradigm displayed ERP responses that systematically differed between target and non-target sounds. Class-discriminant features, however, varied individually from the typical N1-P2 complex and P3 ERP components found in control conditions with random sequences. To fully exploit the sequential presentation structure of CharStreamer, novel data analysis approaches and classification methods were introduced. The results of online spelling tests showed that a competitive spelling speed can be achieved with CharStreamer. With respect to user rating, it clearly outperforms a control setup with random presentation sequences. PMID:24886978

Precise muon drift tube detectors for high background rate conditions

CERN Document Server

Engl, Albert; Dünnweber, Wolfgang

The muon spectrometer of the ATLAS-experiment at the Large H adron Collider consists of drift tube chambers, which provide the precise m easurement of trajec- tories of traversing muons. In order to determine the moment um of the muons with high precision, the measurement of the position of the m uon in a single tube has to be more accurate than σ ≤ 100 m. The large cross section of proton-proton-collisions and th e high luminosity of the accelerator cause relevant background of neutrons and γ s in the muon spectrome- ter. During the next decade a luminosity upgrade [1] to 5 10 34 cm − 2 s − 1 is planned, which will increase the background counting rates consider ably. In this context this work deals with the further development of the existing drift chamber tech- nology to provide the required accuracy of the position meas urement under high background conditions. Two approaches of improving the dri ft tube chambers are described: • In regions of moderate background rates a faster and more lin ear ...

Composite film fabricated on biomedical material with corona streamer plasma processing to mitigate bacterial adhesion

Science.gov (United States)

Alhamarneh, Ibrahim; Pedrow, Patrick; Eskhan, Asma; Abu-Lail, Nehal

2011-10-01

Composite films might control bacterial adhesion and concomitant biofouling that afflicts biomedical materials. Different size molecules of polyethylene glycol (PEG) with nominal molecular weights 600, 2000, and 20000 g/mol were used to synthesize composite films with plasma processing and dip-coating procedures on surgical-grade 316L stainless steel. Before dip-coating, the substrate was pre-coated with plasma-polymerized di(ethylene glycol) vinyl ether (pp-EO2V) in an atmospheric pressure corona streamer plasma reactor. The PEG dip-coating step followed immediately in the same chamber due to the finite lifetime of radicals associated with freshly deposited pp-EO2V. Morphology of the composite film was investigated with an ESEM. FTIR confirmed incorporation of pp-EO2V and PEG species into the composite film. More investigations on the composite film were conducted by XPS measurements. Adhesion of the composite film was evaluated with a standard peel-off test. Stability of the composite film in buffer solution was evaluated by AFM. AFM was also used to measure the film roughness and thickness. Polar and non-polar contact angle measurements were included.

Comparison among different CT ionization chambers

International Nuclear Information System (INIS)

Castro, Maysa C. de; Xavier, Marcos; Caldas, Linda V.E.

2015-01-01

The dosimetry in computed tomography (CT) is carried out by the use of a pencil type ionization-chamber, because it has a uniform response at all angles relative to the incident beam of radiation, which is essential for CT equipment since the X-ray tube executes a circular movement around the table during irradiation. The commercial ionization chamber used to perform quality control procedures of this kind of equipment has a length of the sensitive volume of 10 cm. In the Calibration Laboratory of Instruments (LCI) of the IPEN there were already developed some prototypes with small differences in construction, when compared to commercially available ionization chambers. They have been used in previous studies and showed results within internationally acceptable limits. The ionization chambers tested in this study present the sensitive volume lengths of 1 cm, 3 cm and 10 cm. The objective of this study was to present results on the stability test of the three homemade ionization chambers and a commercial chamber, as well to obtain the calibration coefficients for each of them in CT standard X radiation beams. The obtained results for both characterization tests are within the recommended limits, except for the homemade ionization chambers with sensitive volume lengths of 3 cm and 1 cm in the case of the stability test. (author)

One-dimensional flame instability and control of burning in fire-chamber

Directory of Open Access Journals (Sweden)

Victor E. Volkov

2015-03-01

Full Text Available The flame stability with regard to one-dimensional exponential perturbations both for the combustion in the fire-chamber and the flame propagating in closed tubes or chambers is investigated. It is proved that both stability and instability are possible for the combustion process. At the same time the one-dimensional flame instability is guaranteed near the front wall of the fire-chamber where the fuel supply is realized. Therefore the control of combustion in the fire-chamber leads to support of the flame at the maximum possible distance from the front wall of the fire-chamber to prevent the vibratory combustion or to diminish intensity of pulsations if these pulsations are inevitable.

NA35: sulphur-gold collision

CERN Multimedia

1991-01-01

In this image the real particles produced by the collision of a 6400 GeV sulphur ion with a gold target can be seen as they pass through a streamer chamber. Streamer chambers consist of a gas chamber through which a strong pulsed electric field is passed, creating sparks as a charged particle passes through it. The NA35 experiment, which was in operation in the 1980s, was part of CERN's ongoing heavy ion project.

Streamlined Calibrations of the ATLAS Precision Muon Chambers for Initial LHC Running

CERN Document Server

Amram, N; Benhammou, Y; Moshe, M Ben; Dai, T; Diehl, E B; Dubbert, J; Etzion, E; Ferretti, C; Gregory, J; Haider, S; Hindes, J; Levin, D S; Thun, R; Wilson, A; Weaverdyck, C; Wu, Y; Yang, H; Zhou, B; Zimmermann, S

2012-01-01

The ATLAS Muon Spectrometer is designed to measure the momentum of muons with a resolution of dp/p = 3% and 10% at 100 GeV and 1 TeV momentum respectively. For this task, the spectrometer employs 355,000 Monitored Drift Tubes (MDTs) arrayed in 1200 Chambers. Calibration (RT) functions convert drift time measurements into tube-centered impact parameters for track segment reconstruction. RT functions depend on MDT environmental parameters and so must be appropriately calibrated for local chamber conditions. We report on the creation and application of a gas monitor system based calibration program for muon track reconstruction in the LHC startup phase.

Streamer-induced emission and spectrometric determination of basic plasma parameters

Czech Academy of Sciences Publication Activity Database

Šimek, Milan

2004-01-01

Roč. 54, suppl.C (2004), C778-C783 ISSN 0011-4626. [Symposium on Plasma Physics and Technology /21./. Praha, 14.06.2004-17.06.2004] R&D Projects: GA AV ČR IAA1043403 Institutional research plan: CEZ:AV0Z2043910 Keywords : optical diagnostics * discharge * streamer Subject RIV: BL - Plasma and Gas Discharge Physics Impact factor: 0.292, year: 2004

New results from the UA5/2-experiment

International Nuclear Information System (INIS)

Geich-Gimbel, C.

1985-01-01

This paper covers recent and unpublished results from the investigation of pp-bar-interactions at √s = 200 and 900 GeV with a streamer chamber detector (UA5/2-experiment) at the CERN SPS Collider. The author concentrates on cross section measurements and searches for unusual phenomena. The data these preliminary results are based upon were taken during a very successful run of the pulsed pp-bar-Collider at CERN in spring 1985. The UA5/2 detector took 115,000 streamer chamber pictures and 500,000 electronic events (i.e. only containing information from the trigger hodoscopes and the hadron calorimeter), mainly at the flat bottom at 100 GeV beam energy and the four seconds flat top at 450 GeV of the cycle. For part of the run, an additional photon converter plate was introduced between the beam pipe and the upper streamer chamber to increase the photon detection efficiency at large production angles. The UA5/2-detector consists of two large streamer chambers (6 x 1.25 x 0.5 m/sup 3/ visible volume), placed above and below the 2 mm thick beryllium beam pipe. The azimuthal coverage of the chambers is 95% for a pseudorapidity absolute value of n ≤, 3

Vitreous occlusion of tube implant in a phakic patient with traumatic glaucoma

Directory of Open Access Journals (Sweden)

Suneeta Dubey

2014-01-01

Full Text Available Tube implants or glaucoma drainage devices have become an important method of intraocular pressure reduction when treating complex cases of traumatic glaucoma. However, it is not uncommon to have complications associated with tube implants. The optimal treatment of patients who have undergone glaucoma implant surgery complicated by vitreous incarceration is uncertain. If vitreous is present or is able to prolapse into anterior chamber, as in aphakic or pseudophakic patient without an intact posterior capsule, a concurrent anterior vitrectomy is usually performed. In such cases, pars plana vitrectomy has been found to be more effective in several studies. However, there are no set guidelines for management of such a case in a phakic eye and the management can be more challenging especially when there is no obvious deficiency in posterior capsule, zonular dialysis, or loose vitreous gel in the anterior chamber prior to or during tube implantation. We describe a case of 14-year-old phakic patient with traumatic glaucoma without vitreous gel in anterior chamber whose tube implant became occluded by vitreous resulting in increased intra ocular pressure. This is the first documented report of vitreous incarceration in a phakic patient and its successful management.

Simulating streamer discharges in 3D with the parallel adaptive Afivo framework

NARCIS (Netherlands)

H.J. Teunissen (Jannis); U. M. Ebert (Ute)

2017-01-01

htmlabstractWe present an open-source plasma fluid code for 2D, cylindrical and 3D simulations of streamer discharges, based on the Afivo framework that features adaptive mesh refinement, geometric multigrid methods for Poisson's equation, and OpenMP parallelism. We describe the numerical

Numerical simulation of positive streamer development in thundercloud field enhanced near raindrops

DEFF Research Database (Denmark)

Babich, L. P.; Bochkov, E. I.; Kutsyk, I. M.

2016-01-01

As the threshold field strength for the breakdown in air significantly exceeds the maximum measured thundercloud strength 3 kV/cm/atm, the problem of lightning initiation remains unclear. According to the popular idea, lightning can be initiated from streamer discharges developed in the enhanced...

The drift velocity monitoring system of the CMS barrel muon chambers

CERN Document Server

Altenhoefer, Georg Friedrich; Heidemann, Carsten Andreas; Reithler, Hans; Sonnenschein, Lars; Teyssier, Daniel Francois

2017-01-01

The drift velocity is a key parameter of drift chambers. Its value depends on several parameters: electric field, pressure, temperature, gas mixture, and contamination, for example, by ambient air. A dedicated Velocity Drift Chamber (VDC) with 1-L volume has been built at the III. Phys. Institute A, RWTH Aachen, in order to monitor the drift velocity of all CMS barrel muon Drift Tube chambers. A system of six VDCs was installed at CMS and has been running since January 2011. We present the VDC monitoring system, its principle of operation, and measurements performed.

The drift velocity monitoring system of the CMS barrel muon chambers

Science.gov (United States)

Altenhöfer, Georg; Hebbeker, Thomas; Heidemann, Carsten; Reithler, Hans; Sonnenschein, Lars; Teyssier, Daniel

2018-04-01

The drift velocity is a key parameter of drift chambers. Its value depends on several parameters: electric field, pressure, temperature, gas mixture, and contamination, for example, by ambient air. A dedicated Velocity Drift Chamber (VDC) with 1-L volume has been built at the III. Phys. Institute A, RWTH Aachen, in order to monitor the drift velocity of all CMS barrel muon Drift Tube chambers. A system of six VDCs was installed at CMS and has been running since January 2011. We present the VDC monitoring system, its principle of operation, and measurements performed.

Computational Studies of Positive and Negative Streamers in Bubbles Suspended in Distilled Water

KAUST Repository

Sharma, Ashish; Levko, Dmitry; Raja, Laxminarayan L.

2017-01-01

We perform computational studies of nanosecond streamers generated in helium bubbles immersed in distilled water under high pressure conditions. The model takes into account the presence of water vapor in the gas bubble for an accurate description

Streamer Motives and User-Generated Content on Social Live-Streaming Services

Directory of Open Access Journals (Sweden)

Friedlander, Mathilde B.

2017-03-01

Full Text Available Three most popular information services, Periscope, Ustream, and YouNow, vicarious for all Social Live-Streaming Services (SLSSs, are investigated to analyze their streamers' motivations and the user-generated content. Additionally, we collected demographic data (gender and age. More than 7,500 streams by users from the U.S., Germany, and Japan were observed. Main streamer motivations on SLSSs are boredom, socializing, the need to reach a specific group, the need to communicate, and fun. Important content categories on all three SLSSs are chatting, sharing information, 24/7, and 'slice of life.' We were able to identify differences between users from the U.S., Germany, and Japan as well as between the users of Periscope, Ustream, and YouNow. The main motive to stream in the U.S. is to reach a specific group, while in Japan it is socializing, and in Germany boredom. The top content category for both, YouNow as well as Periscope, is to chat; on Ustream it is 24/7 (i.e., webcams.

Numerical simulations and conformal analysis of growing and branching negative discharge streamers

NARCIS (Netherlands)

Montijn, C.; Meulenbroek, B.; Ebert, U.; Hundsdorfer, W.

2005-01-01

The dynamics of an anode-directed streamer can be described by advection-diffusion equations for the charged particles, including a local field-dependent impact ionization term, and coupled to the Poisson equation for the electric field. We present the results of new simulations that use a local

Formation of ball streamers at a subnanosecond breakdown of gases at a high pressure in a nonuniform electric field

Science.gov (United States)

Beloplotov, D. V.; Tarasenko, V. F.; Sorokin, D. A.; Lomaev, M. I.

2017-11-01

The formation of a diffuse discharge plasma at a subnanosecond breakdown of a "cone-plane" gap filled with air, nitrogen, methane, hydrogen, argon, neon, and helium at various pressures has been studied. Nanosecond negative and positive voltage pulses have been applied to the conical electrode. The experimental data on the dynamics of plasma glow at the stage of formation and propagation of a streamer have been obtained with intensified charge-coupled device and streak cameras. It has been found that the formation of ball streamers is observed in all gases and at both polarities. A supershort avalanche electron beam has been detected behind the flat foil electrode in a wide range of pressures in the case of a negatively charged conical electrode. A mechanism of the formation of streamers at breakdown of various gases at high overvoltages has been discussed.

Optical diagnostics of streamer discharges in atmospheric gases

Czech Academy of Sciences Publication Activity Database

Šimek, Milan

2014-01-01

Roč. 47, č. 46 (2014), s. 463001-463001 ISSN 0022-3727 R&D Projects: GA ČR(CZ) GAP205/12/1709 Grant - others:Rada Programu interní podpory projektů mezinárodní spolupráce AV ČR(CZ) M100431201 Program:M Institutional support: RVO:61389021 Keywords : streamer * optical diagnostics * laser-induced fluorescence * LIF * TALIF * red-sprite Subject RIV: BL - Plasma and Gas Discharge Physics Impact factor: 2.721, year: 2014 http://iopscience.iop.org/0022-3727/47/46/463001/pdf/0022-3727_47_46_463001.pdf

A comparison of charged coupled devices and film sensitivities

International Nuclear Information System (INIS)

Wallick, W.O.; Kenyon, R.G.; Lubatti, H.J.

1977-01-01

The response of a charged coupled device (Fairchild CCD-202) to a Ne light source is studied and compared to the Kodak SO-143 film commonly used for streamer chamber applications. It is found that the CCD-202 cooled to - 10 0 C is considerebly more sensitive than the film. The advantages of using a CCD camera system for streamer chamber and other applications is discussed. (Auth.)

High-rate performance of muon drift tube detectors

International Nuclear Information System (INIS)

Schwegler, Philipp

2014-01-01

The Large Hadron Collider (LHC) at the European Centre for Particle Physics, CERN, collides protons with an unprecedentedly high centre-of-mass energy and luminosity. The collision products are recorded and analysed by four big experiments, one of which is the ATLAS detector. In parallel with the first LHC run from 2009 to 2012, which culminated in the discovery of the last missing particle of the Standard Model of particle physics, the Higgs boson, planning of upgrades of the LHC for higher instantaneous luminosities (HL-LHC) is already progressing. The high instantaneous luminosity of the LHC puts high demands on the detectors with respect to radiation hardness and rate capability which are further increased with the luminosity upgrade. In this thesis, the limitations of the Muon Drift Tube (MDT) chambers of the ATLAS Muon Spectrometer at the high background counting rates at the LHC and performance of new small diameter muon drift tube (sMDT) detectors at the even higher background rates at HL-LHC are studied. The resolution and efficiency of sMDT chambers at high γ-ray and proton irradiation rates well beyond the ones expected at HL-LHC have been measured and the irradiation effects understood using detailed simulations. The sMDT chambers offer an about an order of magnitude better rate capability and are an ideal replacement for the MDT chambers because of compatibility of services and read-out. The limitations of the sMDT chambers are now in the read-out electronics, taken from the MDT chambers, to which improvements for even higher rate capability are proposed.

Space shuttle orbit maneuvering engine reusable thrust chamber program

Science.gov (United States)

Senneff, J. M.

1975-01-01

Reusable thrust chamber and injector concepts were evaluated for the space shuttle orbit maneuvering engine (OME). Parametric engine calculations were carried out by computer program for N2O4/amine, LOX/amine and LOX/hydrocarbon propellant combinations for engines incorporating regenerative cooled and insulated columbium thrust chambers. The calculation methods are described including the fuel vortex film cooling method of combustion gas temperature control, and performance prediction. A method of acceptance of a regeneratively cooled heat rejection reduction using a silicone oil additive was also demonstrated by heated tube heat transfer testing. Regeneratively cooled thrust chamber operation was also demonstrated where the injector was characterized for the OME application with a channel wall regenerative thrust chamber. Bomb stability testing of the demonstration chambers/injectors demonstrated recovery for the nominal design of acoustic cavities. Cavity geometry changes were also evaluated to assess their damping margin. Performance and combustion stability was demonstrated of the originally developed 10 inch diameter combustion pattern operating in an 8 inch diameter thrust chamber.

Neutron accelerator tube having improved ionization section

International Nuclear Information System (INIS)

Givens, W.W.

1982-01-01

A neutron accelerator tube is described having a target section, an ionization section, and a replenisher section for supplying accelerator gas to the ionization section. The ionization section is located between the target and the replenisher section and includes an ionization chamber adapted to receive accelerator gas from the replenisher section. The ionization section further includes spaced cathodes having opposed active surfaces exposed to the interior of the ionization chamber. An anode is located intermediate the cathodes whereby in response to an applied positive voltage, electrons created by field emission are transmitted between the opposed active surfaces of the cathodes and produce the emission of secondary electrons. The active surface of at least one of the cathodes is formulated of a material having a secondary electron emission factor of at least one cathode member located in the tube adjacent to th replenisher section may have a protuberant portion extending axially into the ionization chamber. The other cathode spaced from the first cathode member in the direction of the target has an aperture therein along the axis of the protuberant portion. An annular magnet extends around the exterior of the ionization chamber and envelops the anode member. Means are provided to establish a high permeability magnetic flux path extending outwardly from the opposed poles from the magnet to the active surfaces of the cathode members

Neutron accelerator tube having improved ionization section

International Nuclear Information System (INIS)

Givens, W.W.

1981-01-01

A neutron accelerator tube having a target section, an ionization section, and a replenisher section for supplying accelerator gas to the ionization section. The ionization section is located between the target and the replenisher section and includes an ionization chamber adapted to receive accelerator gas from the replenisher section. The ionization section further includes spaced cathodes having opposed active surfaces exposed to the interior of the ionization chamber. An anode is located intermediate the cathodes whereby in response to an applied positive voltage, electrons created by field emmission are transmitted between the opposed active surfaces of the cathodes and produce the emission of secondary electrons. The active surface of at least one of the cathodes is formulated of a material having a secondary electron emission factor of at least 2. One cathode member located in the tube adjacent to the replenisher section may have a protuberant portion extending axially into the ioization chamber. The other cathode spaced from the first cathode member in the direction of the target has an aperture therein along the axis of the protuberant portion. An annular magnet extends around the exterior of the ionization chamber and envelops the anode member. Means are provided to establish a high permeability magnetic flux path extending outwardly from the opposed poles from the magnet to the active surfaces of the cathode members

The large size straw drift chambers of the COMPASS experiment

CERN Document Server

Bychkov, V N; Dünnweber, W; Faessler, Martin A; Fischer, H; Franz, J; Geyer, R; Gousakov, Yu V; Grünemaier, A; Heinsius, F H; Ilgner, C; Ivanchenko, I M; Kekelidze, G D; Königsmann, K C; Livinski, V V; Lysan, V M; Marzec, J; Matveev, D A; Mishin, S V; Mialkovski, V V; Novikov, E A; Peshekhonov, V D; Platzer, K; San, M; Schmid, T; Shokin, V I; Sissakian, A N; Viriasov, K S; Wiedner, U; Zaremba, K; Zhukov, I A; Zlobin, Y L; Zvyagin, A

2005-01-01

Straw drift chambers are used for the Large Area Tracking (LAT) of the Common Muon and Proton Apparatus for Structure and Spectroscopy (COMPASS) at CERN. An active area of 130 m2 in total is covered by 12 440 straw tubes, which are arranged in 15 double layers. The design has been optimized with respect to spatial resolution, rate capability, low material budget and compactness of the detectors. Mechanical and electrical design considerations of the chambers are discussed as well as new production techniques. The mechanical precision of the chambers has been determined using a CCD X-ray scanning apparatus. Results about the performance during data taking in COMPASS are described.

Construction and manufacture of large size straw-chambers of the COMPASS spectrometer tracking system

International Nuclear Information System (INIS)

Bychkov, V.N.; Gorbacheva, N.M.; Gusakov, Yu.V.

2002-01-01

We report the construction and preliminary testing of 3.6 and 3.2 m long straw tube drift chambers consisting of 672 and 864 channels, respectively. The design considerations, the development of several new techniques are described. The 15 two-layer straw drift chambers have been built for the experiment COMPASS at CERN

The development of an auto-sealing system using an electrically shrinkable tube under a low-pressure condition

Energy Technology Data Exchange (ETDEWEB)

Okano, Yoshihiro; Kitagawa, Takao [NKK Corp, Tsu, Mie (Japan); Shoji, Norio [NKK Corp., Yokohama (Japan); Namioka, Toshiyuki [Nippon Kokan Koji Corp., Yokohama (Japan). Research and Development Dept.; Komura, Minoru [Nitto Denko Corp., Fukaya, Saitama (Japan)

1997-04-01

This article describes the development of a system to create high quality, automatic sealing of field joints of polyethylene coated pipelines. The system uses a combination of an electrically heated shrinkable tube and a low-pressure chamber. The self-heating shrinkable tube includes electric heater wires that heat when connected to electricity. A method was developed to eliminate air trapped between the tube and the steel pipe by shrinking the tube under a low-pressure condition. The low-pressure condition was automatic and easily attained by using a vacuum chamber. It was verified that the system produced high quality sealing of the field joints.

A high precision straw tube chamber with cathode readout

International Nuclear Information System (INIS)

Bychkov, V.N.; Golutvin, I.A.; Ershov, Yu.V.; Zubarev, E.V.; Ivanov, A.B.; Lysiakov, V.N.; Makhankov, A.V.; Movchan, S.A.; Peshekhonov, V.D.; Preda, T.

1993-01-01

The high precision straw chamber with cathode readout was constructed and investigated. The 10 mm diameter straws were made of aluminized Mylar with transparent longitudinal window. The X-coordinate information has been taken from cathode strips as induced charges and investigated with the centroid method. The spatial resolution σ x =103 μm was obtained at a signal-to-noise ratio of about 70. The possible ways to improve the signal-to-noise ratio are discussed. (orig.)

Detectors for the MINOS long-baseline neutrino oscillation experiment

International Nuclear Information System (INIS)

Ayres, D.S.

1996-01-01

The MINOS long-baseline experiment will use an intense neutrino beam, generated by Fermilab''s Main Injector accelerator, and 730 km flight path to search for neutrino oscillations. The 10,000 ton MINOS far detector will utilize toroidally magnetized steel plates interleaved with track chambers to reconstruct event topologies and to measure the energies of the muons, hadrons and electromagnetic showers produced by neutrino interactions. The MINOS collaboration is currently developing three alternative technologies for the track chambers: ''Iarocci'' tubes (operated in either limited streamer or saturated proportional mode), RPC''s (with either glass or ABS plates), and scintillator (either liquid or plastic) with wavelength shifting fiber readout. The technology choice will be made in mid 1997 based on the projected performance and cost of the 32,000 m 2 active detector system

Numerical and experimental study on a pulsed-dc plasma jet

Science.gov (United States)

Liu, X. Y.; Pei, X. K.; Lu, X. P.; Liu, D. W.

2014-06-01

A numerical and experimental study of plasma jet propagation in a low-temperature, atmospheric-pressure, helium jet in ambient air is presented. A self-consistent, multi-species, two-dimensional axially symmetric plasma model with detailed finite-rate chemistry of helium-air mixture composition is used to provide insights into the propagation of the plasma jet. The obtained simulation results suggest that the sheath forms near the dielectric tube inner surface and shields the plasma channel from the tube surface. The strong electric field at the edge of the dielectric field enhances the ionization in the air mixing layer; therefore, the streamer head becomes ring-shaped when the streamer runs out of the tube. The avalanche-to-streamer transition is the main mechanism of streamer advancement. Penning ionization dominates the ionization reactions and increases the electrical conductivity of the plasma channel. The simulation results are supported by experimental observations under similar discharge conditions.

Feasibility study of aluminum beam tube for the collider: An option for no-coating and no-liner

International Nuclear Information System (INIS)

Chou, W.

1994-07-01

This report proposes to use a single-layer beam tube made of high strength, high resistivity aluminum alloy (such as 7039-T61 or A7N01) to replace the double-layer copper coated stainless steel tube in the SSC Collider. The main reasons are: (1) a potential saving of about $23 million which is basically the baseline cost of the copper coating and (2) the use of an extruded aluminum tube consisting of a beam chamber and a pumping chamber may solve the vacuum problem without any liner

Protein interactions at the heart of cardiac chamber formation

NARCIS (Netherlands)

Boogerd, Cornelis J. J.; Moorman, Antoon F. M.; Barnett, Phil

2009-01-01

The vertebrate heart is a muscular pump that contracts in a rhythmic fashion to propel the blood through the body. During evolution, the morphologically complex four-chambered heart of birds and mammals has evolved from a single-layered tube with peristaltic contractility. The heart of Drosophila,

Cardiomyocytes derived from embryonic stem cells resemble cardiomyocytes of the embryonic heart tube

NARCIS (Netherlands)

Fijnvandraat, Arnoud C.; van Ginneken, Antoni C. G.; de Boer, Piet A. J.; Ruijter, Jan M.; Christoffels, Vincent M.; Moorman, Antoon F. M.; Lekanne Deprez, Ronald H.

2003-01-01

OBJECTIVE: After formation of the linear heart tube a chamber-specific program of gene expression becomes active that underlies the formation of the chamber myocardium. To assess whether this program is recapitulated in in vitro differentiated embryonic stem cells, we performed qualitative and

Low noise amplifier for ZnS(Ag) scintillation chamber

International Nuclear Information System (INIS)

Do Hoang Cuong

1998-01-01

A new pulse amplifier that can be used with standard photomultiplier tubes coupled with Zn(Ag) scintillation chamber is presented. The amplifier based on an IC operational amplifier LF 356N consists of a low-noise charge sensitive preamplifier and pulse shaping circuits for optimization of signal to noise ratio. Temperature instability is ≤ 0.05%/ o C. Dynamic range for linear output signals is equal +7 V. The presented amplifier is used in a measuring head for 0.17 L Lucas chambers developed in Department of Nuclear Instruments and Methods of the INCT in laboratory investigations aimed to develop methods and instruments for measurement of radon concentration in the air. The amplifier can also be employed for measurement of ionizing radiation by means of other scintillators coupled to PM tube. The amplifier is followed by a pulse discriminator with adjustable discrimination level. The amplifier output signal and discriminator output pulses are fed to external devices. (author)

Double streamer phenomena in atmospheric pressure low frequency corona plasma

International Nuclear Information System (INIS)

Kim, Dan Bee; Jung, H.; Gweon, B.; Choe, Wonho

2010-01-01

Time-resolved images of an atmospheric pressure corona discharge, generated at 50 kHz in a single pin electrode source, show unique positive and negative corona discharge features: a streamer for the positive period and a glow for the negative period. However, unlike in previous reports of dc pulse and low frequency corona discharges, multistreamers were observed at the initial time stage of the positive corona. A possible physical mechanism for the multistreamers is suggested.

Mechanical support for straw tubes

International Nuclear Information System (INIS)

Joestlein, H.

1990-01-01

A design is proposed for mounting a large number of straw tubes to form an SSC central tracking chamber. The assembly is precise and of very low mass. The fabrication is modular and can be carried out with a minimum of tooling and instrumentation. Testing of modules is possible prior to the final assembly. 4 figs

A projection graphic display for the computer aided analysis of bubble chamber images

International Nuclear Information System (INIS)

Solomos, E.

1979-01-01

A projection graphic display for aiding the analysis of bubble chamber photographs has been developed by the Instrumentation Group of EF Division at CERN. The display image is generated on a very high brightness cathode ray tube and projected on to the table of the scanning-measuring machines as a superposition to the image of the bubble chamber. The display can send messages to the operator and aid the measurement by indicating directly on the chamber image the tracks which are measured correctly or not. (orig.)

Development of the discharge (spark) chamber in Japan in the 1950s

International Nuclear Information System (INIS)

Fukui, Shuji

1989-01-01

The paper, written by its Japanese inventor Shuji Fukui, describes the development of the discharge or spark chamber in Japan in the 1950s. Flash-tubes were used in air-shower cosmic-ray experiments and this led to his design of a neon hodoscope detector. By including the property of neon bulbs glowing the discharge chamber was born, after he observed localized discharges along the trajectories of cosmic-ray particles. (UK)

Streamer free operation of a 2 mm gap resistive plate chamber with $C_{2}F_{5}H$

CERN Document Server

Cerron-Zeballos, E; Hatzifotiadou, D; Lamas-Valverde, J; Williams, M C S; Zichichi, A

1999-01-01

It is necessary to operate the resistive plate chamber (RPC) in avalanche mode to obtain high efficiency at elevated particle fluxes. We examine this mode of operation with a 2 mm gap RPC using gas mixtures containing C/sub 2/F/sub 4/H/sub 2/ and C/sub 2/F/sub 5/H. In order to explain the data we propose that the avalanche growth is strongly limited by space charge effects. (10 refs).

Criteria of choice in the planning of a solar radiation lamp arrangement, in climatic chambers for plant physiology studies

International Nuclear Information System (INIS)

Materassi, A.; Fasano, G.; Vincenzi, M. De

2006-01-01

This technical note is an integration of the previous study: Climatic chambers for plant physiology: a new project concept. This note gives details regarding the planning of the lamp arrangement and demonstrates how mixing, in appropriate quantities, the radiative range of various types of lamps can give apparently contrasting results: to maximize radiation in maximum absorption range of chlorophylls and carotenoids; to minimize heat emission in the climatic chamber. With nine daylight fluorescent tubes, four sunlight metallic halide spotlights and nine red-blue fluorescent tubes, for a total of 562 W mE-2 (electric), mounted on the ceiling of a 2 m high chamber with a 4 square m surface area, on the chamber floor about 130 W mE-2 total solar radiation equivalent was obtained. This means a power emitted, in the bands of chlorophylls and carotenoids absorption, from a total solar radiation (black body of 5,500 K) of about 130 W mE-2. This radiation is sufficient to grow a large number of plant species. In the lamp arrangement there are seven other light fixtures, for fluorescent tubes, defined as auxiliary because tubes can be inserted which either integrate active radiation on the photoreceptors or produce particular spectral ranges. In the above cited work, fluorescent tubes producing in the ultraviolet B range were mounted in these auxiliary fixtures. Less thermal energy emitted in the climatic chamber means that it is possible to use a less powerful conditioning system and, thus, have lower costs of set-up and management. The efficiency of the lighting system is demonstrated by the fact that during 15 days of experimentation on 18-month-old, potted poplar plants (Populus alba), symptoms of insufficient light were not detected [it

Application of multi-source waveform inversion to marine streamer data using the global correlation norm

KAUST Repository

Choi, Yun Seok; Alkhalifah, Tariq Ali

2012-01-01

Conventional multi-source waveform inversion using an objective function based on the least-square misfit cannot be applied to marine streamer acquisition data because of inconsistent acquisition geometries between observed and modelled data

PADI ASIC for straw tube read-out

Energy Technology Data Exchange (ETDEWEB)

Pietraszko, Jerzy; Traeger, Michael; Fruehauf, Jochen; Schmidt, Christian [GSI, Darmstadt (Germany); Ciobanu, Mircea [ISS, Bucharest (Romania); Collaboration: CBM-Collaboration

2016-07-01

A prototype of the CBM MUCH straw tube detector consisting of six individual straws of 6mm inner diameter and 220 mm length filled with Ar/CO{sub 2} gas mixture has been tested at the COSY accelerator in Juelich. The straw tubes were connected to the FEET-PADI6-HDa PCB equipped with PADI-6 fast amplifier/discriminator ASIC. As a reference counter in this measurement the scCVD diamond detector has been used delivering excellent timing, time resolution below 100 ps (sigma), and very precise position information, below 50 μm. The demonstrated position resolution of about 160 μm of the straw tube read out with PADI-6 ASIC confirms the capability of the PADI chip and puts this development as a very attractive readout option for straw tubes and wire chambers.

Short description of BMS/BMF MDT chamber production for the muon spectrometer of the ATLAS experiment

International Nuclear Information System (INIS)

Barashkov, A.V.; Glonti, G.L.; Gongadze, A.L.; Gongadze, I.B.; Gostkin, M.I.; Gus'kov, A.V.; Dedovich, D.V.; Demichev, M.A.; Evtukhovich, P.G.; Elagin, A.L.; Zhemchugov, A.S.; Il'yushenko, E.N.; Kotov, S.A.; Kotova, T.I.; Korolevich, Ya.V.; Kruchonok, V.G.; Krumshtejn, Z.V.; Kuznetsov, N.K.; Lomidze, D.D.; Nikolaev, K.V.; Potrap, I.N.; Rudenko, T.O.; Kharchenko, D.V.; Tskhadadze, Eh.G.; Chepurnov, V.F.; Shelkov, G.A.; Shiyakova, M.M.; Shcherbakov, A.A.; Podkladkin, S.Yu.

2005-01-01

The method of assembly of the MDT chambers for the muon spectrometer of the ATLAS experiment is described. During 2000-2004 ∼ 25000 drift tubes were produced at the DLNP, JINR. The tubes were assembled into 84 muon chambers of BMS/BMF type, one of the six main types for the barrel part of the ATLAS muon spectrometer. Particle momenta must be measured in the ATLAS spectrometer with very high precision (2% at 100 GeV/c and 10% at 1000 GeV/c), which required to produce the coordinate detectors with very high (∼80 μm) precision. We describe the method of assembly of large-scale 5-10 m 2 muon chambers with the signal wire mean deviation from the nominal position less than 20 μm

Negative surface streamers propagating on TiO2 and γ-Al2O3-supported Ag catalysts: ICCD imaging and modeling study

Science.gov (United States)

Kim, Hyun-Ha; Teramoto, Yoshiyuki; Ogata, Atsushi; Kang, Woo Seok; Hur, Min; Song, Young-Hoon

2018-06-01

Surface streamers propagating on the surface of titanium dioxide (TiO2) and alumina (γ-Al2O3) were studied in negative polarity using intensified charge coupled device (ICCD) imaging and numerical simulation. Detailed time-resolved ICCD images of cathode-directed streamers (CDSs) emanating from a ground electrode are first presented in this report. Instead of primary streamers in positive polarity, only a glow-like discharge appeared in the early stage at the cathode under negative polarity. After this discharge disappeared, a counter-propagating CDS initiated from the ground electrode (anode). Numerical simulation indicated that strong electric fields at the pellet-anode and the formation of positive ion rich local spots were the main reason for the CDS formation near the ground electrode. The maximum velocity was 750 km s‑1 for Ag-supported γ-Al2O3 and 550 km s‑1 for Ag-supported TiO2, respectively. In contrast to the CDS in the gas-phase with a positive polarity, the CDS in a catalyst packed-bed under negative polarity showed more branching and a larger number of streamers in the presence of oxygen than in pure N2.

The RISC-spectrometer experiment

International Nuclear Information System (INIS)

Pinter, Gy.

1981-01-01

The RISC (Relativistic Ionising Streamer Chamber) spectrometer (situated at Protvino, joining the accelerator) is discussed, and the experiment carried out in international cooperation is presented. The beam monitor, the trigger system and the control and data recording system as well as the streamer spark chamber are detailed (the latter is the largest of our time). Examples of the main experiments as well as the work carried out in Budapest are discussed briefly. (Sz.J.)

THE POSSIBLE ROLE OF CORONAL STREAMERS AS MAGNETICALLY CLOSED STRUCTURES IN SHOCK-INDUCED ENERGETIC ELECTRONS AND METRIC TYPE II RADIO BURSTS

Energy Technology Data Exchange (ETDEWEB)

Kong, Xiangliang; Chen, Yao; Feng, Shiwei; Wang, Bing; Du, Guohui [Shandong Provincial Key Laboratory of Optical Astronomy and Solar-Terrestrial Environment, and Institute of Space Sciences, Shandong University, Weihai, Shandong 264209 (China); Guo, Fan [Theoretical Division, Los Alamos National Laboratory, Los Alamos, NM 87545 (United States); Li, Gang, E-mail: yaochen@sdu.edu.cn [Department of Space Science and CSPAR, University of Alabama in Huntsville, Huntsville, AL 35899 (United States)

2015-01-10

Two solar type II radio bursts, separated by ∼24 hr in time, are examined together. Both events are associated with coronal mass ejections (CMEs) erupting from the same active region (NOAA 11176) beneath a well-observed helmet streamer. We find that the type II emissions in both events ended once the CME/shock fronts passed the white-light streamer tip, which is presumably the magnetic cusp of the streamer. This leads us to conjecture that the closed magnetic arcades of the streamer may play a role in electron acceleration and type II excitation at coronal shocks. To examine such a conjecture, we conduct a test-particle simulation for electron dynamics within a large-scale partially closed streamer magnetic configuration swept by a coronal shock. We find that the closed field lines play the role of an electron trap via which the electrons are sent back to the shock front multiple times and therefore accelerated to high energies by the shock. Electrons with an initial energy of 300 eV can be accelerated to tens of keV concentrating at the loop apex close to the shock front with a counter-streaming distribution at most locations. These electrons are energetic enough to excite Langmuir waves and radio bursts. Considering the fact that most solar eruptions originate from closed field regions, we suggest that the scenario may be important for the generation of more metric type IIs. This study also provides an explanation of the general ending frequencies of metric type IIs at or above 20-30 MHz and the disconnection issue between metric and interplanetary type IIs.

Computational investigation of the temperature separation in vortex chamber

International Nuclear Information System (INIS)

Anish, S.; Setoguchi, T.; Kim, H. D.

2014-01-01

The vortex chamber is a mechanical device, without any moving parts that separates compressed gas into a high temperature region and a low temperature region. Functionally vortex chamber is similar to a Ranque-Hilsch vortex tube (RVHT), but it is a simpler and compact structure. The objective of the present study is to investigate computationally the physical reasoning behind the energy separation mechanism inside a vortex chamber. A computational analysis has been performed using three-dimensional compressible Navier Stokes equations. A fully implicit finite volume scheme was used to solve the governing equations. A commercial software ANSYS CFX is used for this purpose. The computational predictions were validated with existing experimental data. The results obtained show that the vortex chamber contains a large free vortex zone and a comparatively smaller forced vortex region. The physical mechanism that causes the heating towards periphery of the vortex chamber is identified as the work done by the viscous force. The cooling at the center may be due to expansion of the flow. The extent of temperature separation greatly depends on the outer diameter of the vortex chamber. A small amount of compression is observed towards the periphery of the vortex chamber when the outer diameter is reduced.

Experimental Study of the Effect of Water Mist Location On Blast Overpressure Attenuation in A Shock Tube

Science.gov (United States)

Mataradze, Edgar; Chikhradze, Nikoloz; Bochorishvili, Nika; Akhvlediani, Irakli; Tatishvili, Dimitri

2017-12-01

Explosion protection technologies are based on the formation of a shock wave mitigation barrier between the protection site and the explosion site. Contemporary protective systems use water mist as an extinguishing barrier. To achieve high effectiveness of the protective system, proper selection of water mist characteristics is important. The main factors defining shock wave attenuation in water mist include droplet size distribution, water concentration in the mist, droplet velocity and geometric properties of mist. This paper examines the process of attenuation of shock waves in mist with droplets ranging from 25 to 400 microns under different conditions of water mist location. Experiments were conducted at the Mining Institute with the use of a shock tube to study the processes of explosion suppression by a water mist barrier. The shock tube consists of a blast chamber, a tube, a system for the dosed supply of water, sensors, data recording equipment, and a process control module. Shock wave overpressure reduction coefficient was studied in the shock tube under two different locations of water mist: a) when water mist is created in direct contact with blast chamber and b) the blast chamber and the mist are separated by air space. It is established that in conditions when the air space distance between the blast chamber and the mist is 1 meter, overpressure reduction coefficient is 1.5-1.6 times higher than in conditions when water mist is created in direct contact with blast chamber.

Dark Matter Time Projection Chamber : Recent R&D Results

Science.gov (United States)

Battat, J. B. R.; Ahlen, S.; Chernicoff, M.; Deaconu, C.; Dujmic, D.; Dushkin, A.; Fisher, P.; Henderson, S.; Inglis, A.; Kaboth, A.; Kirsch, L.; Lopez, J. P.; Monroe, J.; Ouyang, H.; Sciolla, G.; Tomita, H.; Wellenstein, H.

2012-02-01

The Dark Matter Time Projection Chamber collaboration recently reported a dark matter limit obtained with a 10 liter time projection chamber filled with CF4 gas. The 10 liter detector was capable of 2D tracking (perpendicular to the drift direction) and 2D fiducialization, and only used information from two CCD cameras when identifying tracks and rejecting backgrounds. Since that time, the collaboration has explored the potential benefits of photomultiplier tube and electronic charge readout to achieve 3D tracking, and particle identification for background rejection. The latest results of this effort is described here.

Secondary magnetic field harmonics dependence on vacuum beam chamber geometry

Directory of Open Access Journals (Sweden)

S. Y. Shim

2013-08-01

Full Text Available The harmonic magnetic field properties due to eddy currents have been studied with respect to the geometry of the vacuum beam chamber. We derived a generalized formula enabling the precise prediction of any field harmonics generated by eddy currents in beam tubes with different cross-sectional geometries. Applying our model to study the properties of field harmonics in beam tubes with linear dipole magnetic field ramping clearly proved that the circular cross section tube generates only a dipole field from eddy currents. The elliptic tube showed noticeable magnitudes of sextupole and dipole fields. We demonstrate theoretically that it is feasible to suppress the generation of the sextupole field component by appropriately varying the tube wall thickness as a function of angle around the tube circumference. This result indicates that it is possible to design an elliptical-shaped beam tube that generates a dipole field component with zero magnitude of sextupole. In a rectangular-shaped beam tube, one of the selected harmonic fields can be prevented if an appropriate wall thickness ratio between the horizontal and vertical tube walls is properly chosen. Our generalized formalism can be used for optimization of arbitrarily complex-shaped beam tubes, with respect to suppression of detrimental field harmonics.

Completion of installation of DT and RPC chambers before Cosmic Challenge

CERN Multimedia

Mimmo Dattola

2006-01-01

All the drift tube ("DT") and resistive plate chambers ("RPC") packages foreseen to be installed in the central barrel ring ("YB0") before the magnet test have been installed (some are missing in the photograph but have since been installed). These silver-coloured rectangular boxes in the gaps between the steel of the rings (red in the image) detect muons. Chambers for Sectors 4 and 5 (sector 1 is at the 9 o'clock position and the counting is clockwise) as well as a couple of chambers in the support "feet" (sectors 9 and 11) will be installed after the magnet test. Chambers for sectors 1 and 7 will be installed in the underground cavern ("UXC") - the latter will be in the places used for the lifting and lowering of the ring.

Monitored Drift Tube (MDT) chambers for precise measurement of muon trajectories in the ATLAS muon spectrometer.

CERN Multimedia

Maximilien Brice

2002-01-01

The basic detection component of the chamber is the cylindrical, aluminium, gas-filled MDT with its central tungsten rhenium wire. Each chamber is an assembly of two parallel multilayers of MDTs separated by a spacer frame. The chambers are pictured here in building 887 on the Prévessin site where they are being tested.

Mapping the base of sand dunes using a new design of land-streamer for static correction applications

KAUST Repository

Almalki, H.

2012-05-16

The complex near-surface structure is a major problem in land seismic data. This is more critical when data acquisition takes place over sand dune surfaces, where the base of the sand acts as a trap for energy and, depending on its shape, can considerably distort conventionally acquired seismic data. Estimating the base of the sand dune surface can help model the sand dune and reduce its harmful influence on conventional seismic data. Among the current methods to do so are drilling upholes and using conventional seismic data to apply static correction. Both methods have costs and limitations. For upholes, the cost factor and their inability to provide a continuous model is well realized. Meanwhile, conventional seismic data lack the resolution necessary to obtain accurate modeling of the sand basement. We developed a method to estimate the sand base from land-streamer seismic acquisition that is developed and geared to sand surfaces. Seismic data acquisition took place over a sand surface in the Al-Thumamah area, where an uphole is located, using the developed land-streamer and conventional spiked geophone systems. Land-streamer acquisition not only provides a more efficient data acquisition system than the conventional spiked geophone approach, but also in our case, the land-streamer provided better quality data with a broader frequency bandwidth. Such data enabled us to do accurate near-surface velocity estimation that resulted in velocities that are very close to those measured using uphole methods. This fact is demonstrated on multiple lines acquired near upholes, and agreement between the seismic velocities and the upholes is high. The stacked depth seismic section shows three layers. The interface between the first and second layers is located at 7 m depth, while the interface between second and third layers is located at 68 m depth, which agrees with the uphole result. 2012 The Author(s).

Study tube housing leakage of 111 conventional diagnostic X-ray machines using ion chamber survey meter

International Nuclear Information System (INIS)

Lalrinmawia, Jonathan; Tiwari, Ramesh Chandra; Pau, Kham Suan

2018-01-01

This study aims at measuring the leakage radiation from X-ray tube and compare to national and international safety standard. The leakage radiation is formed at the anode inside the X-ray tube and transmitted through the tube housing. The tube housing is proposed to protect both patients and workers from leakage radiation. To the best of the authors' knowledge, no tube housing leakage measurements have been done so far in the present study area

Laser Welding Test Results with Gas Atmospheres in Welding Chamber

Energy Technology Data Exchange (ETDEWEB)

Joung, Chang-Young; Hong, Jin-Tae; Ahn, Sung-Ho; Heo, Sung-Ho; Jang, Seo-Yun; Yang, Tae-Ho [Korea Atomic Energy Research Institute, Daejeon (Korea, Republic of)

2015-10-15

The weld beads of specimens welded under identical conditions in the helium and argon gas were cleaner, more regular, and steadier than those in a vacuum. The penetration depth of the FZ in the vacuum was much deeper than those in the helium and argon gas. To measure the irradiation properties of nuclear fuel in a test reactor, a nuclear fuel test rod instrumented with various sensors must be fabricated with assembly processes. A laser welding system to assemble the nuclear fuel test rod was designed and fabricated to develop various welding technologies of the fuel test rods to joint between a cladding tube and end-caps. It is an air-cooling optical fiber type and its emission modes are a continuous (CW) mode of which the laser generates continuous emission, and pulse (QCW) mode in which the laser internally generates sequences of pulses. We considered the system welding a sample in a chamber that can weld a specimen in a vacuum and inert gas atmosphere, and the chamber was installed on the working plate of the laser welding system. In the chamber, the laser welding process should be conducted to have no defects on the sealing area between a cladding tube and an end-cap.

Assembly and method for testing the integrity of stuffing tubes

Energy Technology Data Exchange (ETDEWEB)

Morrison, E.F.

1996-12-31

A stuffing tube integrity checking assembly includes first and second annular seals, with each seal adapted to be positioned about a stuffing tube penetration component. An annular inflation bladder is provided, the bladder having a slot extending longitudinally there along and including a separator for sealing the slot. A first valve is in fluid communication with the bladder for introducing pressurized fluid to the space defined by the bladder when mounted about the tube. First and second releasible clamps are provided. Each clamp assembly is positioned about the bladder for securing the bladder to one of the seals for thereby establishing a fluid-tight chamber about the tube.

Fabrication of Free Air Well Type Ionization Chamber and Calculational Assessment and Measurement of Its Operational Characteristics

Directory of Open Access Journals (Sweden)

Koroush Arbabi

2007-12-01

Full Text Available Introduction: Well type ionization chamber is a measuring device which is used to determine the activity of brachytherapy sources. The chamber has a cylindrical volume in which a cylindrical tube is mounted in the middle of the chamber. For the measurements, the brachytherapy sources are transferred to the middle of the tube. Materials and Methods: For designing the well type chamber, the measurement principals of well type chambers were considered and MCNP-4C code as a calculation tool was used. The designed chamber was simulated and the response of the chamber was evaluated. In this investigation, the chamber operational parameters such as operating voltage, leakage current, reproducibility, reference measuring point, recombination and polarization factors as well as response stability for 137Cs, 57Co and 241Am sources were studied. Results: The chamber leakage currents at the operating voltage in comparison to the chamber response for the measurement of the above mentioned sources were negligible. The responses of the fabricated chamber for these sources are reproducible and its reference measurement position for these sources was obtained at 6 cm from the bottom of the chamber. The recombination factor for the well type chamber was negligible and the polarization factor is close to 1. Therefore, these two factors were not considered in the measurements. The reproducibility of the measurements in different intervals shows the stability of the chamber response for each source. Also the results of the chamber current measurement in term of source strength were compared to the response of the simulated chamber for different source positions and energy ranges of the used sources. Discussion and Conclusion: The results show that the measurement of the reference positions for each source in the simulated and fabricated chamber is quite in a good agreement. Regarding the reliable operational properties of the fabricated chamber, this chamber can be

Study of final states in deep inelastic muon scattering

CERN Multimedia

2002-01-01

The aim of this experiment is to study the different possible final states in deep inelastic muon scattering from hydrogen in connection with the detection of the scattered muon in a forward spectrometer (Experiment NA2).\\\\ \\\\ A vertex detector will be used which extends the hadron detection capabilities into the backward hemisphere of the centre-of-mass system. Particle momenta can be measured down to 200 MeV/c in a vertex magnet, which contains a streamer chamber (SC Particle identification will be done in a series of wide angle Čerenkov counters (C$_{0}$, C$_{1}$) and at low momenta in time-of-flight counter hodoscopes (F1-F4). An 8-plane module of MWPC chambers (PV) will be used in conjunction with the streamer chamber and the drift chambers WV1 and WV2 and WV3. \\\\ \\\\ The vertex magnet is a C magnet with circular pole tips of 2 m diameter and 1 m gap width. The central magnetic field will be 1.5 T. The streamer chamber (2m x 1.2m x 0.72m) will contain a 1 m liquid H$_{2}$ target.\\\\ \\\\ As a natural extens...

Mechanisms Affecting Performance of the BaBar Resistive Plate Chambers and Searches for Remediation

International Nuclear Information System (INIS)

Lu, Changguo

2003-01-01

The BaBar experiment at PEPII relies on the Instrumentation of the Flux Return (IFR) for both muon identification and KL detection. The active detector is composed of Resistive Plate Chambers (RPC's) operated in streamer mode. Since the start of operation the RPC's have suffered persistent efficiency deterioration and dark current increase problems. The ''autopsy'' of bad BaBar RPC's revealed that in many cases uncured Linseed oil droplets had formed on the inner surface of the Bakelite plates, leading to current paths from oil ''stalagmites'' bridging the 2 mm gap. In this paper a possible model of this ''stalagmite'' formation and its effect on the dark current and efficiency of RPC chambers is presented. Laboratory test results strongly support this model. Based upon this model we are searching for solutions to eliminate the unfavorable effect of the oil stalagmites. The lab tests show that the stalagmite resistivity increases dramatically if exposed to the air, an observation that points to a possible way to remedy the damage and increase the efficiency. We have seen that flowing an oxygen gas mixture into the chamber helps to polymerize the uncured linseed oil. Consequently the resistivity of the bridged oil stalagmites increases, as does that of the oil coating on the frame edges and spacers, significantly reducing the RPC dark currents and low-efficiency regions. We have tested this idea on two chambers removed from BaBar because of their low efficiency and high dark current. These test results are reported in the paper, and two other remediation methods also mentioned. We continue to study this problem, and try to find new treatments with permanent improvement

STUDENT AWARD FINALIST: Oxygen Pathways in Streamer Discharge for Transient Plasma Ignition

Science.gov (United States)

Pendleton, S. J.; Bowman, S.; Singleton, D.; Watrous, J.; Carter, C.; Lempert, W.; Gundersen, M. A.

2011-10-01

The use of streamers for the ignition of fuels, also known as transient plasma ignition (TPI), has been shown in a variety of engines to improve combustion through decreased ignition delay, increased lean burn capability and increased energy release relative to conventional spark ignition. The mechanisms behind these improvements, however, remain poorly understood. Temperature measurements by optical emission spectroscopy demonstrate that ignition by TPI is a nonthermal process, and thus is almost entirely dependent on the production and presence of electron impact-created active species in the discharge afterglow. Of particular interest are active oxygen species due to their relatively long lifetimes at high pressures and the pivotal role they play in combustion reactions. In order to elucidate the oxygen pathways, here we report the investigation of the temporal evolution of the populations of atomic oxygen and ozone by use of two-photon absorption laser induced fluorescence (TALIF) and UV absorption, respectively. Experimental results are presented and compared to kinetic modeling of the streamers. Future experiments are proposed to better understand the physics behind TPI. Supported by NSF, AFOSR, NumerEx-ONR, AFRL-WPAFB.

Application of dimensional analysis to ozone production by pulsed streamer discharge in oxygen

Energy Technology Data Exchange (ETDEWEB)

Buntat, Z; Harry, J E; Smith, I R [Department of Electronic and Electrical Engineering, Loughborough University, Loughborough, Leicestershire LE11 3TU (United Kingdom)

2003-07-07

This paper describes the use of dimensional analysis in investigating the effects of the electrical and the discharge configuration parameters on ozone production in oxygen, by means of a pulsed streamer discharge. Ozone destruction factors are taken into account in the model, and predicted results are shown to be in good agreement with experimental findings.

Application of dimensional analysis to ozone production by pulsed streamer discharge in oxygen

CERN Document Server

Buntat, Z; Smith, I R

2003-01-01

This paper describes the use of dimensional analysis in investigating the effects of the electrical and the discharge configuration parameters on ozone production in oxygen, by means of a pulsed streamer discharge. Ozone destruction factors are taken into account in the model, and predicted results are shown to be in good agreement with experimental findings.

Application of dimensional analysis to ozone production by pulsed streamer discharge in oxygen

International Nuclear Information System (INIS)

Buntat, Z; Harry, J E; Smith, I R

2003-01-01

This paper describes the use of dimensional analysis in investigating the effects of the electrical and the discharge configuration parameters on ozone production in oxygen, by means of a pulsed streamer discharge. Ozone destruction factors are taken into account in the model, and predicted results are shown to be in good agreement with experimental findings

Application of dimensional analysis to ozone production by pulsed streamer discharge in oxygen

Science.gov (United States)

Buntat, Z.; Harry, J. E.; Smith, I. R.

2003-07-01

This paper describes the use of dimensional analysis in investigating the effects of the electrical and the discharge configuration parameters on ozone production in oxygen, by means of a pulsed streamer discharge. Ozone destruction factors are taken into account in the model, and predicted results are shown to be in good agreement with experimental findings.

Numerical modelling of radiation in 2+ and- systems of nitrogen accounting non-stationary excited states population in a streamer discharge

International Nuclear Information System (INIS)

Djakov, A.F.; Bobrov, J.K.; Jourguelenas, J.V.

2000-01-01

Measurement of spectral bands intensity allows to obtain a valuable information on plasma temperature and electron density - the parameters having critical influence on chemical reactions and efficiency of plasma chemistry applications. At present the interest in streamer discharges is becoming more important because of their applications to flue gas treatment and ozone generation. For a streamer discharge in air the molecular spectral bands of the second positive and first negative systems of nitrogen are the most intensive ones. However, both the registration of radiation and interpretation of the received data are very complicated problems. (Authors)

A study on the equivalent electric circuit simulation model of DBD streamer and glow alternate discharge

International Nuclear Information System (INIS)

Yao, J; Zhang, Z T; Xu, S J; Yu, Q X; Yu, Z; Zhao, J S

2013-01-01

This paper presents a dynamic simulating model of the dielectric barrier discharge (DBD), structured as an equivalent electric circuit of the streamer and glow discharge generated alternately in DBD. The main parameters of DBD have been established by means of analysing the structural characteristics of a single discharge cell. An electrical comprehensive Simulink /MATLAB model was developed in order to reveal the interaction of the adjacent two discharge cell. A series of simulations was carried out in order to estimate the key structural parameters that affect the alternate streamer and glow discharge mode. The comparison results of experimental and simulate indicate that there exists a close similarity of the current waveforms graphic. Therefore, we can grasp a deep understanding mechanism of the dielectric barrier discharge and optimize the plasma reactor.

Pulse shape of the self quenching streamer counter in the coexistence region

International Nuclear Information System (INIS)

Chen Hongfang; Han Jiaxiang; Li Cheng; Xu Zizong

1996-01-01

The pulse shape of the electrical signal out of the counter operating in the self-quenching streamer (SQS) mode is obtained and the time correlation between the primary avalanche and the SQS avalanche is measured and studied. The results yield more information in the coexistence region about the time jitters in the process of the SQS avalanche than that shown in our last paper. (orig.)

Program package for data preparation of RISK events

International Nuclear Information System (INIS)

Denes, E.; Wagner, I.; Nagy, J.

1980-01-01

A FORTRAN program package written for the CDC-6500 computer is presented. The SMHV program is designed to transform data obtained from events of RISK streamer chamber by means of measuring SAMET or PUOS devices to the HEVAS data tormat format needed by the geometrical reconstruction program. Such a transformation provides the standartization of measurement data procession inside the RISK collaboration and capability of the direct input into program of event geometrical reconstruction registered on a film of RISK streamer chamber

Positive streamers in air of varying density : experiments on the scaling of the excitation density

NARCIS (Netherlands)

Dubrovin, D.; Nijdam, S.; Clevis, T.T.J.; Heijmans, L.C.J.; Ebert, U.; Yair, Y.; Price, C.

2015-01-01

Streamers are rapidly extending ionized finger-like structures that dominate the initial breakdown of large gas volumes in the presence of a sufficiently strong electric field. Their macroscopic parameters are described by simple scaling relations, where the densities of electrons and of excited

Inspection and repair of steam generator tubing with a robot

International Nuclear Information System (INIS)

Boehm, H.H.; Foerch, H.

1985-01-01

During inspection and repair of steam generator tubing, radiation exposure to personnel is an unrequested endowment. To combat this intrinsic handicap, a robot has been designed for deployment in all operations inside the steam generator water chamber. This measure drastically reduces entering time and also improves inspection capabilities with regard to the accuracy and reproduction of the desired tube address. The inherent flexibility of the robot allows for performing various inspection and repair techniques: eddy-current testing of tubing; ultrasonic testing of tubing; visual examination of tube ends; profilometry measurements; tube plugging; plug removal; tube extraction; sleeving of tubes; tube end repair; chemical cleaning; and thermal treatment. Plant experience has highlighted the following features of the robot: 1) short installation and demounting periods; 2) installation independent of manhole location; 3) installation possible from outside the steam generator; 4) only one relocation required to address all the tube positions; 5) fast and highly accurate positioning; 6) operational surveillance not required; and 7) drastic reduction of radiation exposure to personnel during repair work

Temporal development and chemical efficiency of positive streamers in a large scale wire-plate reactor as a function of voltage waveform parameters

Science.gov (United States)

Winands, G. J. J.; Liu, Z.; Pemen, A. J. M.; van Heesch, E. J. M.; Yan, K.; van Veldhuizen, E. M.

2006-07-01

In this paper a large-scale pulsed corona system is described in which pulse parameters such as pulse rise-time, peak voltage, pulse width and energy per pulse can be varied. The chemical efficiency of the system is determined by measuring ozone production. The temporal and spatial development of the discharge streamers is recorded using an ICCD camera with a shortest exposure time of 5 ns. The camera can be triggered at any moment starting from the time the voltage pulse arrives on the reactor, with an accuracy of less than 1 ns. Measurements were performed on an industrial size wire-plate reactor. The influence of pulse parameters like pulse voltage, DC bias voltage, rise-time and pulse repetition rate on plasma generation was monitored. It was observed that for higher peak voltages, an increase could be seen in the primary streamer velocity, the growth of the primary streamer diameter, the light intensity and the number of streamers per unit length of corona wire. No significant separate influence of DC bias voltage level was observed as long as the total reactor voltage (pulse + DC bias) remained constant and the DC bias voltage remained below the DC corona onset. For those situations in which the plasma appearance changed (e.g. different streamer velocity, diameter, intensity), a change in ozone production was also observed. The best chemical yields were obtained for low voltage (55 kV), low energetic pulses (0.4 J/pulse): 60 g (kWh)-1. For high voltage (86 kV), high energetic pulses (2.3 J/pulse) the yield decreased to approximately 45 g (kWh)-1, still a high value for ozone production in ambient air (RH 42%). The pulse repetition rate has no influence on plasma generation and on chemical efficiency up to 400 pulses per second.

Temporal development and chemical efficiency of positive streamers in a large scale wire-plate reactor as a function of voltage waveform parameters

Energy Technology Data Exchange (ETDEWEB)

Winands, G J J [EPS Group, Department of Electrical Engineering, Eindhoven University of Technology, 5600 MB, Eindhoven (Netherlands); Liu, Z [EPS Group, Department of Electrical Engineering, Eindhoven University of Technology, 5600 MB, Eindhoven (Netherlands); Pemen, A J M [EPS Group, Department of Electrical Engineering, Eindhoven University of Technology, 5600 MB, Eindhoven (Netherlands); Heesch, E J M van [EPS Group, Department of Electrical Engineering, Eindhoven University of Technology, 5600 MB, Eindhoven (Netherlands); Yan, K [EPS Group, Department of Electrical Engineering, Eindhoven University of Technology, 5600 MB, Eindhoven (Netherlands); Veldhuizen, E M van [EPG Group, Department of Applied Physics, Eindhoven University of Technology, 5600 MB, Eindhoven (Netherlands)

2006-07-21

In this paper a large-scale pulsed corona system is described in which pulse parameters such as pulse rise-time, peak voltage, pulse width and energy per pulse can be varied. The chemical efficiency of the system is determined by measuring ozone production. The temporal and spatial development of the discharge streamers is recorded using an ICCD camera with a shortest exposure time of 5 ns. The camera can be triggered at any moment starting from the time the voltage pulse arrives on the reactor, with an accuracy of less than 1 ns. Measurements were performed on an industrial size wire-plate reactor. The influence of pulse parameters like pulse voltage, DC bias voltage, rise-time and pulse repetition rate on plasma generation was monitored. It was observed that for higher peak voltages, an increase could be seen in the primary streamer velocity, the growth of the primary streamer diameter, the light intensity and the number of streamers per unit length of corona wire. No significant separate influence of DC bias voltage level was observed as long as the total reactor voltage (pulse + DC bias) remained constant and the DC bias voltage remained below the DC corona onset. For those situations in which the plasma appearance changed (e.g. different streamer velocity, diameter, intensity), a change in ozone production was also observed. The best chemical yields were obtained for low voltage (55 kV), low energetic pulses (0.4 J/pulse): 60 g (kWh){sup -1}. For high voltage (86 kV), high energetic pulses (2.3 J/pulse) the yield decreased to approximately 45 g (kWh){sup -1}, still a high value for ozone production in ambient air (RH 42%). The pulse repetition rate has no influence on plasma generation and on chemical efficiency up to 400 pulses per second.

Temporal development and chemical efficiency of positive streamers in a large scale wire-plate reactor as a function of voltage waveform parameters

International Nuclear Information System (INIS)

Winands, G J J; Liu, Z; Pemen, A J M; Heesch, E J M van; Yan, K; Veldhuizen, E M van

2006-01-01

In this paper a large-scale pulsed corona system is described in which pulse parameters such as pulse rise-time, peak voltage, pulse width and energy per pulse can be varied. The chemical efficiency of the system is determined by measuring ozone production. The temporal and spatial development of the discharge streamers is recorded using an ICCD camera with a shortest exposure time of 5 ns. The camera can be triggered at any moment starting from the time the voltage pulse arrives on the reactor, with an accuracy of less than 1 ns. Measurements were performed on an industrial size wire-plate reactor. The influence of pulse parameters like pulse voltage, DC bias voltage, rise-time and pulse repetition rate on plasma generation was monitored. It was observed that for higher peak voltages, an increase could be seen in the primary streamer velocity, the growth of the primary streamer diameter, the light intensity and the number of streamers per unit length of corona wire. No significant separate influence of DC bias voltage level was observed as long as the total reactor voltage (pulse + DC bias) remained constant and the DC bias voltage remained below the DC corona onset. For those situations in which the plasma appearance changed (e.g. different streamer velocity, diameter, intensity), a change in ozone production was also observed. The best chemical yields were obtained for low voltage (55 kV), low energetic pulses (0.4 J/pulse): 60 g (kWh) -1 . For high voltage (86 kV), high energetic pulses (2.3 J/pulse) the yield decreased to approximately 45 g (kWh) -1 , still a high value for ozone production in ambient air (RH 42%). The pulse repetition rate has no influence on plasma generation and on chemical efficiency up to 400 pulses per second

Neutron-sensitive ionization chamber

International Nuclear Information System (INIS)

Mayer, W.

1978-01-01

The neutron-sensitive ionization chamber which is to be applied for BWRs consists of a cylindrical outer electrode, closed at the ends, and a concentrically arranged inner electrode. It is designed as a hollow tube and coated with uranium on the outside. The reaction space lies between the two electrodes. The electrical connection is obtained through a coaxial cable whose nickel helix is properly intorduced into the inner electrode made of titanium or nickel. The sheathing respectively external conductor of the cable has got the same diameter as the outer electrode and is butt-welded to it. Between the cable helix and the sheathing there is filled Al 2 O 3 powder. The reaction space is sealed against the cable by means of a little tube pushed over the internal conductor resp. the helix. It consists of Ni resp. Al 2 O 3 which is coated on the outside at first by a layer of Al 2 O 3 and a layer of Ni resp. by a metal layer on the inside and on the outside. (DG) [de

Pulsed Streamer Discharge Characteristics of Ozone Production in Dry Air

OpenAIRE

Samaranayake, W.J.M.; Miyahara, Y.; Namihira, T.; Katsuki, S.; Sakugawa, T.; Hackam, R.; Akiyama, H.; ナミヒラ, タカオ; カツキ, スナオ; アキヤマ, ヒデノリ; 波平, 隆男; 勝木, 淳; 秋山, 秀典

2000-01-01

Experimental investigation of HV short pulsed streamer discharges in dry air-fed ozonizers under various operating conditions are reported. Ozone concentration, energy input and ozone production yield (efficiency) were measured at various voltages (14 to 37 kV), pulse repetition rates (25 to 400 pulses per second, pps), flow rates (1.5 to 3.0 1/min) and different gap spacings (10 to 20 mm) at a pressure of 1.01×105 Pa in dry air. A spiral copper wire (1 mm in diameter) made to a cylindrical c...

Towards a fully kinetic 3D electromagnetic particle-in-cell model of streamer formation and dynamics in high-pressure electronegative gases

International Nuclear Information System (INIS)

Rose, D. V.; Welch, D. R.; Clark, R. E.; Thoma, C.; Zimmerman, W. R.; Bruner, N.; Rambo, P. K.; Atherton, B. W.

2011-01-01

Streamer and leader formation in high pressure devices is dynamic process involving a broad range of physical phenomena. These include elastic and inelastic particle collisions in the gas, radiation generation, transport and absorption, and electrode interactions. Accurate modeling of these physical processes is essential for a number of applications, including high-current, laser-triggered gas switches. Towards this end, we present a new 3D implicit particle-in-cell simulation model of gas breakdown leading to streamer formation in electronegative gases. The model uses a Monte Carlo treatment for all particle interactions and includes discrete photon generation, transport, and absorption for ultra-violet and soft x-ray radiation. Central to the realization of this fully kinetic particle treatment is an algorithm that manages the total particle count by species while preserving the local momentum distribution functions and conserving charge [D. R. Welch, T. C. Genoni, R. E. Clark, and D. V. Rose, J. Comput. Phys. 227, 143 (2007)]. The simulation model is fully electromagnetic, making it capable of following, for example, the evolution of a gas switch from the point of laser-induced localized breakdown of the gas between electrodes through the successive stages of streamer propagation, initial electrode current connection, and high-current conduction channel evolution, where self-magnetic field effects are likely to be important. We describe the model details and underlying assumptions used and present sample results from 3D simulations of streamer formation and propagation in SF 6 .

Towards a fully kinetic 3D electromagnetic particle-in-cell model of streamer formation and dynamics in high-pressure electronegative gases

Science.gov (United States)

Rose, D. V.; Welch, D. R.; Clark, R. E.; Thoma, C.; Zimmerman, W. R.; Bruner, N.; Rambo, P. K.; Atherton, B. W.

2011-09-01

Streamer and leader formation in high pressure devices is dynamic process involving a broad range of physical phenomena. These include elastic and inelastic particle collisions in the gas, radiation generation, transport and absorption, and electrode interactions. Accurate modeling of these physical processes is essential for a number of applications, including high-current, laser-triggered gas switches. Towards this end, we present a new 3D implicit particle-in-cell simulation model of gas breakdown leading to streamer formation in electronegative gases. The model uses a Monte Carlo treatment for all particle interactions and includes discrete photon generation, transport, and absorption for ultra-violet and soft x-ray radiation. Central to the realization of this fully kinetic particle treatment is an algorithm that manages the total particle count by species while preserving the local momentum distribution functions and conserving charge [D. R. Welch, T. C. Genoni, R. E. Clark, and D. V. Rose, J. Comput. Phys. 227, 143 (2007)]. The simulation model is fully electromagnetic, making it capable of following, for example, the evolution of a gas switch from the point of laser-induced localized breakdown of the gas between electrodes through the successive stages of streamer propagation, initial electrode current connection, and high-current conduction channel evolution, where self-magnetic field effects are likely to be important. We describe the model details and underlying assumptions used and present sample results from 3D simulations of streamer formation and propagation in SF6.

Towards a fully kinetic 3D electromagnetic particle-in-cell model of streamer formation and dynamics in high-pressure electronegative gases

Energy Technology Data Exchange (ETDEWEB)

Rose, D. V.; Welch, D. R.; Clark, R. E.; Thoma, C.; Zimmerman, W. R.; Bruner, N. [Voss Scientific, LLC, Albuquerque, New Mexico 87108 (United States); Rambo, P. K.; Atherton, B. W. [Sandia National Laboratories, Albuquerque, New Mexico 87185 (United States)

2011-09-15

Streamer and leader formation in high pressure devices is dynamic process involving a broad range of physical phenomena. These include elastic and inelastic particle collisions in the gas, radiation generation, transport and absorption, and electrode interactions. Accurate modeling of these physical processes is essential for a number of applications, including high-current, laser-triggered gas switches. Towards this end, we present a new 3D implicit particle-in-cell simulation model of gas breakdown leading to streamer formation in electronegative gases. The model uses a Monte Carlo treatment for all particle interactions and includes discrete photon generation, transport, and absorption for ultra-violet and soft x-ray radiation. Central to the realization of this fully kinetic particle treatment is an algorithm that manages the total particle count by species while preserving the local momentum distribution functions and conserving charge [D. R. Welch, T. C. Genoni, R. E. Clark, and D. V. Rose, J. Comput. Phys. 227, 143 (2007)]. The simulation model is fully electromagnetic, making it capable of following, for example, the evolution of a gas switch from the point of laser-induced localized breakdown of the gas between electrodes through the successive stages of streamer propagation, initial electrode current connection, and high-current conduction channel evolution, where self-magnetic field effects are likely to be important. We describe the model details and underlying assumptions used and present sample results from 3D simulations of streamer formation and propagation in SF{sub 6}.

Observed tail current systems associated with bursty bulk flows and auroral streamers during a period of multiple substorms

Directory of Open Access Journals (Sweden)

C. Forsyth

2008-02-01

Full Text Available We present a multi-instrument study of a substorm bursty bulk flow (BBF and auroral streamer. During a substorm on 25 August 2003, which was one of a series of substorms that occurred between 00:00 and 05:00 UT, the Cluster spacecraft encountered a BBF event travelling Earthwards and duskwards with a velocity of ~500 km s−1 some nine minutes after the onset of the substorm. Coincident with this event the IMAGE spacecraft detected an auroral streamer in the substorm auroral bulge in the Southern Hemisphere near the footpoints of the Cluster spacecraft. Using FluxGate Magnetometer (FGM data from the four Cluster spacecraft, we determine the field-aligned currents in the BBF, using the curlometer technique, to have been ~5 mA km−2. When projected into the ionosphere, these currents give ionospheric field-aligned currents of ~18 A km−2, which is comparable with previously observed ionospheric field-aligned currents associated with BBFs and auroral streamers. The observations of the BBF are consistent with the plasma "bubble" model of Chen and Wolf (1993. Furthermore, we show that the observations of the BBF are consistent with the creation of the BBF by the reconnection of open field lines Earthward of a substorm associated near-Earth neutral line.

Calandria cooling structure in pressure tube reactor

International Nuclear Information System (INIS)

Hyugaji, Takenori; Sasada, Yasuhiro.

1976-01-01

Purpose: To contrive the structure of a heavy water distributing device in a pressure tube reactor thereby to reduce the variation in the cooling function thereof due to the welding deformation and installation error. Constitution: A heating water distributing plate is provided at the lower part of the upper tubular plate of a calandria tank to form a heavy water distributing chamber between both plates and a plurality of calandria tubes. Heavy water which has flowed in the upper part of the heavy water distributing plate from the heavy water inlet nozzle flows down through gaps formed around the calandria tubes, whereby the cooling of the calandria tank and the calandria tubes is carried out. In the above described calandria cooling structure, a heavy water distributing plate support is provided to secure the heavy water distributing plate and torus-shaped heavy water distributing rings are fixed to holes formed in the heavy water distributing plate penetrating through the calandria tubes thereby to form torus-shaped heavy water outlet ports each having a space. (Seki, T.)

Spatially hybrid computations for streamer discharges with generic features of pulled fronts: I. Planar fronts

NARCIS (Netherlands)

C. Li (Chao); U. M. Ebert (Ute); W. Hundsdorfer (Willem)

2010-01-01

textabstractStreamers are the first stage of sparks and lightning; they grow due to a strongly enhanced electric field at their tips: this field is created by a thin curved space charge layer. These multiple scales are already challenging when the electrons are approximated by densities. However,

Gas sampling calorimeter studies in proportional, saturated avalanche, and streamer modes

International Nuclear Information System (INIS)

Atac, M.; Bedeschi, F.; Yoh, J.; Morse, R.; Procario, M.

1982-01-01

Recently, satisfactory new results were obtained at SLAC from gas sampling calorimeters running in the saturated avalanche mode within the energy range of 1.5 to 17.5 GeV. To study the higher energy behavior of this mode, more tests were carried out in the M4 beamline at Fermilab. This paper contains results obtained from the MAC prototype electromagnetic and hadronic calorimeters running in the proportional, saturated avalanche, and the streamer regions for energies between 12 and 150 GeV

Study the Z-Plane Strip Capacitance

International Nuclear Information System (INIS)

Parikh, H.; Swain, S.

2005-01-01

The BaBaR detector at the Stanford Linear Accelerator Center is currently undergoing an upgrade to improve its muon and neutral hadron detection system. The Resistive Plate Chambers (RPCs) that had been used till now have deteriorated in performance over the past few years and are being replaced by Limited Streamer Tube (LSTs). Each layer of the system consists of a set of up to 10 streamer tube modules which provide one coordinate (φ coordinate) and a single ''Z-plane'' which provides the Z coordinate of the hit. The large area Z-planes (up to 12m 2 ) are 1mm thick and contain 96 copper strips that detect the induced charge from avalanches created in the streamer tube wires. All the Z-planes needed for the upgrade have already been constructed, but only a third of the planes were installed last summer. After installing the 24 Z-planes last year, it was learned that 0.7% of the strips were dead when put inside the detector. This was mainly due to the delicate solder joint between the read-out cable and the strip, and since it is difficult to access or replace the Z-planes inside the detector, it is very important to perform various tests to make sure that the Z-planes will be efficient and effective in the long term. We measure the capacitance between the copper strips and the ground plane, and compare it to the theoretical value that we expect. Instead of measuring the capacitance channel by channel, which would be a very tedious job, we developed a more effective method of measuring the capacitance. Since all the Z-planes were built at SLAC, we also built a smaller 46 cm by 30 cm Z-plane with 12 strips just to see how they were constructed and to gain a better understanding about the solder joints

Improvements to parallel plate flow chambers to reduce reagent and cellular requirements

Directory of Open Access Journals (Sweden)

Larson Richard S

2001-09-01

Full Text Available Abstract Background The parallel plate flow chamber has become a mainstay for examination of leukocytes under physiologic flow conditions. Several design modifications have occurred over the years, yet a comparison of these different designs has not been performed. In addition, the reagent requirements of many designs prohibit the study of rare leukocyte populations and require large amounts of reagents. Results In this study, we evaluate modifications to a newer parallel plate flow chamber design in comparison to the original parallel plate flow chamber described by Lawrence et al. We show that modifications in the chamber size, internal tubing diameters, injection valves, and a recirculation design may dramatically reduce the cellular and reagent requirements without altering measurements. Conclusions These modifications are simple and easily implemented so that study of rare leukocyte subsets using scarce or expensive reagents can occur.

Storm-time Convection Dynamics Viewed from Optical Auroras: from Streamer to Patchy Pulsating Aurora

Science.gov (United States)

Yang, B.; Donovan, E.; Liang, J.; Grono, E.

2016-12-01

In a series of statistical and event studies we have demonstrated that the motion of patches in regions of Patchy Pulsating Aurora (PPA) is very close to if not exactly convection. Thus, 2D maps of PPA motion provides us the opportunity to remote sense magnetospheric convection with relatively high space and time resolution, subject to uncertainties associated with mapping between the ionosphere and magnetosphere. In this study, we use THEMIS ASI aurora observations (streamers and patchy pulsating aurora) combined with SuperDARN convection measurements, Swarm ion drift velocity measurements, and RBSP electric field measurements to explore the convection dynamics in storm time. From 0500 UT to 0600 UT on March 19 2015, convection observations across 5 magnetic local time (MLT) inferred from the motion of PPA patches and SuperDARN measurements show that a westward SAPS (Subauroral Polarized Streams) enhancement occurs after an auroral streamer. This suggests that plasma sheet fast flows can affect the inner magnetospheric convection, and possibly trigger very fast flows in the inner magnetosphere.

Radiation aging studies of CO2 hydrocarbon mixtures for the SLD drift chamber

International Nuclear Information System (INIS)

Venuti, J.P.; Chadwick, G.B.

1988-10-01

The SLD drift chamber requires a 'slow' drifting gas and low diffusion to allow wave form digitization. CO 2 provides this but requires an admixture of a quencher to provide more gain. A test chamber with an 8 sense wire cell, such as will appear in the final chamber, was exposed to an x-ray tube while containing a variety of binary admixtures of Co 2 : 8% isobutane, 8% ethane, and 2% isopropanol. It was determined that adding small fractions of water (≤0.66%) or isopropanol (1--2%) to the Co 2 : 8% ethane, or 8% isobutane extended the useful life of the chamber so that integrated charge collections of /approximately/1 C/cm are permissible. Results and discussions are presented. 10 refs., 7 figs., 1 tab

Performance of Drift-Tube Detectors at High Counting Rates for High-Luminosity LHC Upgrades

CERN Document Server

Bittner, Bernhard; Kortner, Oliver; Kroha, Hubert; Manfredini, Alessandro; Nowak, Sebastian; Ott, Sebastian; Richter, Robert; Schwegler, Philipp; Zanzi, Daniele; Biebel, Otmar; Hertenberger, Ralf; Ruschke, Alexander; Zibell, Andre

2016-01-01

The performance of pressurized drift-tube detectors at very high background rates has been studied at the Gamma Irradiation Facility (GIF) at CERN and in an intense 20 MeV proton beam at the Munich Van-der-Graaf tandem accelerator for applications in large-area precision muon tracking at high-luminosity upgrades of the Large Hadron Collider (LHC). The ATLAS muon drifttube (MDT) chambers with 30 mm tube diameter have been designed to cope with and neutron background hit rates of up to 500 Hz/square cm. Background rates of up to 14 kHz/square cm are expected at LHC upgrades. The test results with standard MDT readout electronics show that the reduction of the drift-tube diameter to 15 mm, while leaving the operating parameters unchanged, vastly increases the rate capability well beyond the requirements. The development of new small-diameter muon drift-tube (sMDT) chambers for LHC upgrades is completed. Further improvements of tracking e?ciency and spatial resolution at high counting rates will be achieved with ...

Precision Muon Tracking at Future Hadron Colliders with sMDT Chambers

CERN Document Server

Kortner, Oliver; Müller, Felix; Nowak, Sebastian; Richter, Robert

2016-01-01

Small-diameter muon drift tube (sMDT) chambers are a cost-effective technology for high-precision muon tracking. The rate capability of the sMDT chambers has been extensively tested at the Gamma Irradiation Facility at CERN in view of expected rates at future high-energy hadron colliders. Results show that it fulfills the requirements over most of the acceptance of muon detectors. The optimization of the read-out electronics to further increase the rate capability of the detectors is discussed. Chambers of this type are under construction for upgrades of the muon spectrometer of the ATLAS detector at high LHC luminosities. Design and construction procedures have been optimized for mass production while providing a precision of better than 10 micrometers in the sense wire positions and the mechanical stability required to cover large areas.

Mechanical structure of the TOPAZ barrel drift chamber

International Nuclear Information System (INIS)

Morimoto, T.; Maruyama, K.; Okuno, H.

1987-07-01

A Barrel Drift Chamber (BDC) is constructed for the TOPAZ experiment at TRISTAN, KEK. The BDC has a cylindrical shape with dimensions of 325.2 cm in inner diameter, 347.2 cm in outer diameter and 500 cm long. It consists of 1232 drift tubes made of conductive plastic cathodes, which are staggered in four layers. In this report, a design of the mechanical structure and construction procedures are described in detail. (author)

A Full Front End Chain for Drift Chambers

Energy Technology Data Exchange (ETDEWEB)

Chiarello, G. [Istituto Nazionale di Fisica Nucleare, Lecce (Italy); Università del Salento, Lecce (Italy); Corvaglia, A.; Grancagnolo, F. [Istituto Nazionale di Fisica Nucleare, Lecce (Italy); Panareo, M. [Istituto Nazionale di Fisica Nucleare, Lecce (Italy); Università del Salento, Lecce (Italy); Pepino, A., E-mail: aurora.pepino@le.infn.it [Istituto Nazionale di Fisica Nucleare, Lecce (Italy); Università del Salento, Lecce (Italy); Primiceri, P. [Istituto Nazionale di Fisica Nucleare, Lecce (Italy); Tassielli, G. [Istituto Nazionale di Fisica Nucleare, Lecce (Italy); Fermilab, Batavia, Illinois (United States); Università Marconi, Roma (Italy)

2014-03-01

We developed a high performance full chain for drift chamber signals processing. The Front End electronics is a multistage amplifier board based on high performance commercial devices. In addition a fast readout algorithm for Cluster Counting and Timing purposes has been implemented on a Xilinx-Virtex 4 core FPGA. The algorithm analyzes and stores data coming from a Helium based drift tube and represents the outcome of balancing between efficiency and high speed performance.

Sub-nanosecond delays of light emitted by streamer in atmospheric pressure air: Analysis of N2( C3Πu) and N2+(B2Σ u +) emissions and fundamental streamer structure

Czech Academy of Sciences Publication Activity Database

Hoder, T.; Bonaventura, Z.; Bourdon, A.; Šimek, Milan

2015-01-01

Roč. 117, č. 7 (2015), 073302-073302 ISSN 0021-8979 R&D Projects: GA ČR(CZ) GAP205/12/1709 Institutional support: RVO:61389021 Keywords : streamer * optical diagnostics * nitrogen * emission Subject RIV: BL - Plasma and Gas Discharge Physics Impact factor: 2.101, year: 2015 http://scitation.aip.org/content/aip/journal/jap/117/7/10.1063/1.4913215

Bent paths of a positive streamer and a cathode-directed spark leader in diffuse discharges preionized by runaway electrons

Energy Technology Data Exchange (ETDEWEB)

Zhang, Cheng; Shao, Tao, E-mail: st@mail.iee.ac.cn; Wang, Ruixue; Yan, Ping [Institute of Electrical Engineering, Chinese Academy of Sciences, Beijing 100190 (China); Key Laboratory of Power Electronics and Electric Drive, Chinese Academy of Sciences, Beijing 100190 (China); Tarasenko, Viktor F.; Beloplotov, Dmitry V.; Lomaev, Mikhail I.; Sorokin, Dmitry A. [Institute of High Current Electronics, Russian Academy of Science, Tomsk 634055 (Russian Federation); National Research Tomsk State University, 36 Lenin Ave., Tomsk 634050 (Russian Federation)

2015-03-15

Diffuse discharges preionized by runaway electrons can produce large-area homogeneous discharges at elevated pressures, which is an intriguing phenomenon in the physics of pulsed discharges. In this paper, runaway-electron-preionized diffuse discharge (REP DD) was obtained in a wide pressure range (0.05–0.25 MPa), and under certain conditions a positive streamer and a cathode-directed spark leader could be observed to propagate at some angles to the applied (background) electric field lines. For a 16-mm gap at an air pressure of 0.08–0.1 MPa, the percentage of pulses in which such propagation is observed is about 5%–50% of their total number, and in the other pulses such bent paths could not be observed because there is even no streamer or cathode-directed spark leader in diffuse discharges. In our opinion, such propagation of the positive streamer and the cathode-directed spark leader at some angle to the background electric field lines owes to different increase rates of the electron density in different regions of the discharge volume under REP DD conditions. Therefore, during the formation of a REP DD, the increase of the electron density is inhomogeneous and nonsimultaneous, resulting in an electron density gradient at the ionization wave front.

Bent paths of a positive streamer and a cathode-directed spark leader in diffuse discharges preionized by runaway electrons

International Nuclear Information System (INIS)

Zhang, Cheng; Shao, Tao; Wang, Ruixue; Yan, Ping; Tarasenko, Viktor F.; Beloplotov, Dmitry V.; Lomaev, Mikhail I.; Sorokin, Dmitry A.

2015-01-01

Diffuse discharges preionized by runaway electrons can produce large-area homogeneous discharges at elevated pressures, which is an intriguing phenomenon in the physics of pulsed discharges. In this paper, runaway-electron-preionized diffuse discharge (REP DD) was obtained in a wide pressure range (0.05–0.25 MPa), and under certain conditions a positive streamer and a cathode-directed spark leader could be observed to propagate at some angles to the applied (background) electric field lines. For a 16-mm gap at an air pressure of 0.08–0.1 MPa, the percentage of pulses in which such propagation is observed is about 5%–50% of their total number, and in the other pulses such bent paths could not be observed because there is even no streamer or cathode-directed spark leader in diffuse discharges. In our opinion, such propagation of the positive streamer and the cathode-directed spark leader at some angle to the background electric field lines owes to different increase rates of the electron density in different regions of the discharge volume under REP DD conditions. Therefore, during the formation of a REP DD, the increase of the electron density is inhomogeneous and nonsimultaneous, resulting in an electron density gradient at the ionization wave front

Numerical investigation of unsteady detonation waves in combustion chamber using Shchelkin spirals

Directory of Open Access Journals (Sweden)

Repaka Ramesh

2016-09-01

Full Text Available : Pulse Detonation Engine (PDE is considered to be a propulsive system of future air vehicles. The main objective is to minimizing the Deflagration to Detonation transition run-up distance and time by placing Shchelkin spiral with varying pitch length. Here we have considered blockage-area ratio is 0.5 as optimal value from review of previous studies. In the present study the detonation initiation and propagation is modeled numerically using commercial CFD codes GAMBIT and FLUENT. The unsteady and two-dimensional compressible Reynolds Averaged Navier-Stokes equation is used to simulate the model. Fuel-air mixture of Hydrogen-air is used for better efficiency of PDE. It is very simple straight tube with Shchelkin spirals, one of the methods which is used to initiate detonation is creation of high pressure and temperature chamber region with 0.5cm from closed end of tube where shock will generate and transition into low pressure and temperature region propagates towards end of the tube. Two different zones namely high and low pressure zones are used as interface in modeling and patching has been used to fill the zones with hydrogen and oxygen with different pressure and temperatures hence shock leads to propagate inside the combustion chamber.

Observed tail current systems associated with bursty bulk flows and auroral streamers during a period of multiple substorms

Directory of Open Access Journals (Sweden)

C. Forsyth

2008-02-01

Full Text Available We present a multi-instrument study of a substorm bursty bulk flow (BBF and auroral streamer. During a substorm on 25 August 2003, which was one of a series of substorms that occurred between 00:00 and 05:00 UT, the Cluster spacecraft encountered a BBF event travelling Earthwards and duskwards with a velocity of ~500 km s⁻¹ some nine minutes after the onset of the substorm. Coincident with this event the IMAGE spacecraft detected an auroral streamer in the substorm auroral bulge in the Southern Hemisphere near the footpoints of the Cluster spacecraft. Using FluxGate Magnetometer (FGM data from the four Cluster spacecraft, we determine the field-aligned currents in the BBF, using the curlometer technique, to have been ~5 mA km⁻². When projected into the ionosphere, these currents give ionospheric field-aligned currents of ~18 A km⁻², which is comparable with previously observed ionospheric field-aligned currents associated with BBFs and auroral streamers. The observations of the BBF are consistent with the plasma "bubble" model of Chen and Wolf (1993. Furthermore, we show that the observations of the BBF are consistent with the creation of the BBF by the reconnection of open field lines Earthward of a substorm associated near-Earth neutral line.

A new TXRF vacuum chamber with sample changer for chemical analysis using silicon drift chamber detector

International Nuclear Information System (INIS)

Streli, C.; Wobrauschek, P.; Zoeger, N.; Pepponi, G.

2003-01-01

Full text: Several TXRF spectrometers for chemical analysis as well as for wafer surface analysis are commercially available. But there is no one available for chemical analysis offering the possibility to measure the samples in vacuum conditions. Vacuum of 10 -2 mbar in the sample environment helps to reduce the background due to scattering from air, thus to improve the detection limits as well as to reduce the absorption of low energy fluorescence radiation from low Z elements and extend the elemental range to be measured and removes the Ar lines from the spectrum. The x-ray group of the Atominstitut designed and fabricated a new vacuum chamber for TXRF equipped with a 12 position sample changer from Italstructures, Riva, Italy. The detector used was a 10 mm 2 silicon drift detector (KETEK, Munich, Germany), offering the advantage of electrically cooling, so no LN2 is required. The chamber was designed to be attached to a diffraction tube housing, e.g. with a fine focus Mo-x-ray tube and uses a multilayer monochromator. Spectra are stored by a small AMTEK MCA and control between sample changer and MCA communication is done by a modified AMPTEK software. The performance is expressed in detection limits of 1 pg Rb for Mo Ka excitation with 50 kV, 40 mA excitation conditions, 1000 s lifetime, obtained from a sample containing 600 pg Rb as single element standard. Details on performance, reproducibility and light element excitation and detection are presented. (author)

A southeastern Mediterranean PV streamer and its role in December 2001 case with torrential rains in Israel

Directory of Open Access Journals (Sweden)

S. O. Krichak

2007-01-01

Full Text Available A precipitation event of unprecedented intensity took place over northern part of Israel during 4 December 2001–5 December 2001. The case was associated with formation of a Cyprus Low cyclone over the Asia Minor. In the current study the synoptic developments over the eastern part of the Mediterranean region are simulated with the MM5 nonhydrostatic model and analyzed based on dynamic tropopause patterns calculated from the simulation results. According to the results, a powerful potential vorticity (PV streamer system played a major role in the process over the southeastern Mediterranean region. The PV streamer created conditions for seclusion of moist air masses from the equatorial East Africa and Atlantics during the cyclone development. Condensation of the moisture, associated with the latent heat release processes have contributed to the intense thunderstorm activity and heavy precipitation of the event.

The CPLEAR detector at CERN

CERN Document Server

Adler, R; Alhalel, T; Angelopoulos, Angelos; Apostolakis, Alcibiades J; Aslanides, Elie; Backenstoss, Gerhard; Bal, F; Bard, J P; Barraca, D; Bee, C P; Behnke, O; Benelli, A; Bennet, J; Bertin, V; Blanc, F; Bloch, P; Bonnet, M; Bula, C; Calzas, A; Carlson, P J; Carroll, M; Carvalho, J; Cawley, E; Charalambous, S; Chardalas, M; Chardin, G; Charra, P; Chertok, M B; Cody, A; Da Silva, J; Damianoglou, D; Daniel, R; Danielsson, M; Dechelette, Paul; Dedieu, M; Dedoussis, S; Dejardin, M; Derré, J; Dijksman, A; Dinkespiler, B; Dodgson, M; Dröge, M; Duclos, J; Dudragne, J; Durand, D; Ealet, A; Eckart, B; Eleftheriadis, C; Engster, Claude; Evangelou, I; Faravel, L; Fassnacht, P; Faure, J L; Felder, C; Ferreira-Marques, R; Fetscher, W; Fidecaro, Maria; Filipcic, A; Francis, D; Fry, J; Fuglesang, C; Gabathuler, Erwin; Gally, Y; Gamet, R; Garreta, D; Geiss, D; Geralis, R; Gerber, H J; Go, A; Gumplinger, P; Guyon, D; Guyot, C; Harrison, P; Harrison, P F; Haselden, A; Hayman, P J; Hazen, E S; Henry-Coüannier, F; Heyes, W G; Hollander, R W; Hubert, E; Jacobs, C; Jansson, K; Johner, H U; Jon-And, K; Karkour, N; Kérek, A; Kesseler, G; Kettle, P R; King, D; Klados, T; Kochowski, Claude; Kokkas, P; Kontek, K; Kreuger, R; Lawry, T; Lecouturier, T; Le Gac, R; Leimgruber, F; Linget, D; Liolios, A; Löfstedt, B; Louis, F; Machado, E; Maley, P; Mall, U; Mandic, I; Manthos, N; Marel, Gérard; Marin, C P; Martin, H; Michau, J C; Mikuz, M; Miller, J; Montanet, François; Nakada, Tatsuya; Nanni, F; Onofre, A; Pagels, B; Papadopoulos, I M; Pavlopoulos, P; Pelucchi, F; Petit, P; Philippoussis, K; Pinto da Cunha, J; Policarpo, Armando; Polivka, G; Postma, H; Rheme, C; Rickenbach, R; Roberts, B L; Rozaki, E; Ruf, T; Sacks, L; Sakelliou, L; Sanders, P; Santoni, C; Sarigiannis, K; Schäfer, M; Schaller, L A; Schietinger, T; Schopper, A; Schune, P; Soares, A; Steinacher, M; Tatsis, S; Tauscher, Ludwig; Thibault, C; Touchard, F; Touramanis, C; Triantis, F A; Tröster, D A; Tsamouranis, I; Tschopp, H; Tsilimigras, Panayiotis; Van Beveren, E; van Eijk, C W E; Van Koningsfeld, V; Vanuxem, J P; Varner, G S; Verweij, H; Vlachos, S; Warner, D; Watson, E; Weber, P; Wendler, H; Wigger, O; Witzig, C; Wolter, M; Yéche, C; Zavrtanik, D; Zimmerman, D

1996-01-01

The CPLEAR collaboration has constructed a detector at CERN for an extensive programme of CP-, T- and CPT-symmetry studies using ${\\rm K}^0$ and $\\bar{\\rm K}^0$ produced by the annihilation of $\\bar{\\rm p}$'s in a hydrogen gas target. The ${\\rm K}^0$ and $\\bar{\\rm K}^0$ are identified by their companion products of the annihilation ${\\rm K}^{\\pm} \\pi^{\\mp}$ which are tracked with multiwire proportional chambers, drift chambers and streamer tubes. Particle identification is carried out with a liquid Cherenkov detector for fast separation of pions and kaons and with scintillators which allow the measurement of time of flight and energy loss. Photons are measured with a lead/gas sampling electromagnetic calorimeter. The required antiproton annihilation modes are selected by fast online processors using the tracking chamber and particle identification information. All the detectors are mounted in a 0.44 T uniform field of an axial solenoid of diameter 2 m and length 3.6 m to form a magnetic spectrometer capable o...

Combustor with two stage primary fuel tube with concentric members and flow regulating

Science.gov (United States)

Parker, David Marchant; Whidden, Graydon Lane; Zolyomi, Wendel

1999-01-01

A combustor for a gas turbine having a centrally located fuel nozzle and inner, middle and outer concentric cylindrical liners, the inner liner enclosing a primary combustion zone. The combustor has an air inlet that forms two passages for pre-mixing primary fuel and air to be supplied to the primary combustion zone. Each of the pre-mixing passages has a circumferential array of swirl vanes. A plurality of primary fuel tube assemblies extend through both pre-mixing passages, with each primary fuel tube assembly located between a pair of swirl vanes. Each primary fuel tube assembly is comprised of two tubular members. The first member supplies fuel to the first pre-mixing passage, while the second member, which extends through the first member, supplies fuel to the second pre-mixing passage. An annular fuel manifold is divided into first and second chambers by a circumferentially extending baffle. The proximal end of the first member is attached to the manifold itself while the proximal end of the second member is attached to the baffle. The distal end of the first member is attached directly to the second member at around its mid-point. The inlets of the first and second members are in flow communication with the first and second manifold chambers, respectively. Control valves separately regulate the flow of fuel to the two chambers and, therefore, to the two members of the fuel tube assemblies, thereby allowing the flow of fuel to the first and second pre-mixing passages to be separately controlled.

Front-end electronics for long straw tube systems

International Nuclear Information System (INIS)

Paulos, J.J.; Blake, S.L.

1990-01-01

This paper addresses several critical issues in the readout of long, small diameter plastic straw tubes for central tracking subsystems. Of particular concern are signal attentuation in long straw tubes and signal reflections which arise from improper termination at the ends of the tube. This work is part of a 12 institution collaboration to design and validate a hybrid central tracking chamber (HCTC) utilizing both straw tube and scintillating fiber components. The HCTC design calls for 4 mm diameter plastic straw tubes spanning the entire central tracking region (6-8 m) with readout electronics at both ends. An electrical isolator may be used at the center of each wire to separate each tube into two electrically isolated regions so as to reduce occupancy by a factor of two. With this scheme, no track is farther than 4 m from the associated readout electronics. The HCTC collaboration includes the participation of researchers at the University of Pennsylvania who have contributed a preamplifier and shaper ship which is used in the simulations presented here. A more complete discussion of the HCTC design can be found in the paper by Dr. Alfred Goshaw

Development and characterisation of new high-rate muon drift tube detectors

Energy Technology Data Exchange (ETDEWEB)

Bittner, Bernhard

2012-07-25

With the increase of the LHC luminosity above the design value and the higher background counting rates, detectors in the ATLAS muon spectrometer have to be replaced because the limits of the radiation tolerance will be exceeded. Therefore drift tube chambers with 15 mm tube diameter were developed. The required construction accuracy was verified and the limits of the resolution and efficiency were determined in a muon beam and under gamma irradiation and compared to model expectations.

Trigger drift chamber for the upgraded mark II detector at PEP

Science.gov (United States)

Ford, W. T.; Smith, J. G.; Wagner, S. R.; Weber, P.; White, S. L.; Alvarez, M.; Calviño, F.; Fernandez, E.

1987-04-01

A small cylindrical track detector was built as an array of single-wire drift cells with aluminized mylar cathode tubes. Point measurement resolution of ˜ 90 μm was achieved with a drift gas of 50% argon-50% ethane at atmospheric pressure. The chamber construction, electronics, and calibration are discussed. Performance results from PEP colliding-beam data are presented.

Stress response of Escherichia coli induced by surface streamer discharge in humid air

International Nuclear Information System (INIS)

Doležalová, Eva; Prukner, Václav; Lukeš, Petr; Šimek, Milan

2016-01-01

Inactivation of Escherichia coli by means of surface streamer discharge has been investigated to obtain new insights into the key mechanisms involved, with a particular emphasis placed on the microbial response to plasma-induced stress. The surface streamer discharge was produced in coplanar dielectric barrier discharge electrode geometry, and was driven by an amplitude-modulated ac high voltage in humid synthetic air at atmospheric pressure. The response to plasma-induced stress was evaluated by using conventional cultivation, sublethal injury and resazurin assay and the LIVE/DEAD ® BacLight ™ Bacterial Viability kit. Compared to conventional cultivation, the LIVE/DEAD ® test labels bacteria with damaged membranes, while resazurin assay tracks their metabolic activity. Our results clearly demonstrate that the treated bacteria partly lost their ability to grow properly, i.e. they became injured and culturable, or even viable but nonculturable (VBNC). The ability to develop colonies could have been lost due to damage of the bacterial membrane. Damage of the membranes was mainly caused by the lipid peroxidation, evidencing the key role of oxygen reactive species, in particular ozone. We conclude that the conventional cultivation method overestimates the decontamination efficiency of various plasma sources, and must therefore be complemented by alternative techniques capable of resolving viable but nonculturable bacteria. (paper)

In situ measurement of ceramic vacuum chamber conductive coating quality

International Nuclear Information System (INIS)

Doose, C.; Harkay, K.; Kim, S.; Milton, S.

1997-01-01

A method for measuring the relative surface resistivity and quality of conductive coatings on ceramic vacuum chambers was developed. This method is unique in that it allows one to test the coating even after the ceramic chamber is installed in the accelerator and under vacuum; furthermore, the measurement provides a localized surface reading of the coating conductance. The method uses a magnetic probe is calibrated using the measured DC end-to-end resistance of the tube under test and by comparison to a high quality test surface. The measurement method has also been verified by comparison to high frequency impedance measurements. A detailed description, results, and sensitivity of the technique are given here

He leaks in the CERN LHC beam vacuum chambers operating at cryogenic temperatures

CERN Document Server

Baglin, V

2007-01-01

The 27 km long large hadron collider (LHC), currently under construction at CERN, will collide protons beam at 14 TeV in the centre of mass. In the 8 arcs, the superconducting dipoles and quadrupoles of the FODO cells operate with superfluid He at 1.9 K. In the 8 long straight sections, the cold bores of the superconducting magnets are held at 1.9 or 4.5 K. Thus, in the LHC, 75% of the beam tube vacuum chamber is cooled with He. In many areas of the machine, He leaks could appear in the beam tube. At cryogenic temperature, the gas condenses onto the cold bores or beam screens, and interacts with the circulating beam. He leaks creates a He front propagating along the vacuum chambers, which might cause magnet quench. We discuss the consequences of He leaks, the possible means of detections, the strategies to localise them and the methods to measure their size.

Breakdown processes in wire chambers, prevention and rate capability

International Nuclear Information System (INIS)

Atac, M.

1983-01-01

Breakdowns were optically and electronically observed in drift tubes and drift chambers. They occur at a critical gain for given intensity in a gas mixture when ultraviolet photons are not completely quenched. It was observed that the breakdowns depended critically on average current for a given gas mixture independent of the size of the drift tubes used. Using 4.6% ethyl alcohol vapor mixed into 50/50 argon ethane gas, breakdown are eliminated up to 7 /sub μ/A average current drawn by pulses on a 1 cm section of an anode wire under an intense source. Pulses with an avalanche size of 10 6 electron rates above 10 6 pulses per centimeter per wire may be obtained with the elimination of breakdowns

Breakdown processes in wire chambers, prevention and rate capability

International Nuclear Information System (INIS)

Atac, M.

1982-01-01

Breakdowns were optically and electronically observed in drift tubes and drift chambers. They occur at a critical gain for given intensity in a gas mixture when ultraviolet photons are not completely quenched. It was observed that the breakdowns depended critically on average current for a given gas mixture independent of the size of the drift tubes used. Using 4.6% ethyl alcohol vapor mixed into 50/50 argon ethane gas, breakdowns are eliminated up to 7 μA average current drawn by pulses on a 1 cm section of an anode wire under an intense source. Pulses with an avalanche size of 10 6 electron rates above 10 6 pulses per centimeter per wire may be obtained with the elimination of breakdowns

Tubular heat exchangers, preferably for hot ashes and the like with two inlet chambers for hot ashes at different pressures

Energy Technology Data Exchange (ETDEWEB)

Vasiliev, B P; Borisov, N L; Semenov, M K; Ponomarev, I K; Tyryshkina, B G; Gorbatenko, I V

1985-10-28

The stand and the tubes are encased in a structure where the space between the stand and the structure is divided into a collector chamber and a distribution chamber. Ashes of shale are introduced at different pressures into a special inlet where equalizing takes place and the ashes will flow homogeneously through the heat exchanger.

Thermal hydraulics analysis of LIBRA-SP target chamber

International Nuclear Information System (INIS)

Mogahed, E.A.

1996-01-01

LIBRA-SP is a conceptual design study of an inertially confined 1000 MWe fusion power reactor utilizing self-pinched light ion beams. There are 24 ion beams which are arranged around the reactor cavity. The reaction chamber is an upright cylinder with an inverted conical roof resembling a mushroom, and a pool floor. The vertical sides of the cylinder are occupied by a blanket zone consisting of many perforated rigid HT-9 ferritic steel tubes called PERITs (PEr-forated RIgid Tube). The breeding/cooling material, liquid lead-lithium, flows through the PERITs, providing protection to the reflector/vacuum chamber so as to make it a lifetime component. The neutronics analysis and cavity hydrodynamics calculations are performed to account for the neutron heating and also to determine the effects of vaporization/condensation processes on the surface heat flux. The steady state nuclear heating distribution at the midplane is used for thermal hydraulics calculations. The maximum surface temperature of the HT-9 is chosen to not exceed 625 degree C to avoid drastic deterioration of the metal's mechanical properties. This choice restricts the thermal hydraulics performance of the reaction cavity. The inlet first surface coolant bulk temperature is 370 degree C, and the heat exchanger inlet coolant bulk temperature is 502 degree C. 4 refs., 6 figs., 2 tabs

Report from Workshop on VOCs in diving chambers

International Nuclear Information System (INIS)

Crosbie, A.; Simpson, M.

2000-05-01

This report of the 'Setting the Standards' workshop on the problems of volatile organic compounds (VOCs) in diving in offshore operations, sponsored jointly by the UK Health and Safety Executive Offshore Safety Division and the Stolt Rockwater Joint Venture, gives details of the papers presented covering the chemical contamination of diver's atmosphere, sampling protocols and methods, analytical procedures used for VOCs in hyperbaric chambers, and contamination in buildings. The setting of exposure limits in the UK, the derivation of threshold limiting values (TVLs), the selection of Tenax tubes for atmospheric sampling, organic contaminant monitoring, and NASA's approach to contamination in the space environment are examined, and dealing with contamination problems in a submarine atmosphere, and the simulation of a condensate spillage in a diving bell are discussed. Guidelines for the measurement of VOCs in hyperbaric chambers are given in the appendices

Space charge effect measurements for a multi-channel ionization chamber used for synchrotron radiation

International Nuclear Information System (INIS)

Nasr, Amgad

2012-01-01

In vivo coronary angiography is one of the techniques used to investigate the heart diseases, by using catheter to inject a contrast medium of a given absorption coefficient into the heart vessels. Taking X-ray images produced by X-ray tube or synchrotron radiation for visualizing the blood in the coronary arteries. As the synchrotron radiation generated by the relativistic charged particle at the bending magnets, which emits high intensity photons in comparison with the X-ray tube. The intensity of the synchrotron radiation is varies with time. However for medical imaging it's necessary to measure the incoming intensity with the integrated time. The thesis work includes building a Multi-channel ionization chamber which can be filled with noble gases N 2 , Ar and Xe with controlled inner pressure up to 30 bar. This affects the better absorption efficiency in measuring the high intensity synchrotron beam fluctuation. The detector is a part of the experimental setup used in the k-edge digital subtraction angiography project, which will be used for correcting the angiography images taken by another detector at the same time. The Multi-channel ionization chamber calibration characteristics are measured using 2 kW X-ray tube with molybdenum anode with characteristic energy of 17.44 keV. According to the fast drift velocity of the electrons relative to the positive ions, the electrons will be collected faster at the anode and will induce current signals, while the positive ions is still drifting towards the cathode. However the accumulation of the slow ions inside the detector disturbs the homogeneous applied electric field and leads to what is known a space charge effect. In this work the space charge effect is measured with very high synchrotron photons intensity from EDR beam line at BESSYII. The strong attenuation in the measured amplitude signal occurs when operating the chamber in the recombination region. A plateau is observed at the amplitude signal when