Showing papers on "Shields published in 1985"

Design of Cassegrain Light Shields

Abstract: A Fortran program has been written for the optimum design of light shields for Cassegrain optical systems with finite field. The techniques employed are described, and results are shown.

Smokeless flare gas burner

Abstract: A flare gas burner is described in which a deflector shell approximating a half Venturi is disposed about the upper end of a waste gas delivery pipe equipped with standard pilot-flame igniters and flame stabilizers. A manifold on the lower end of the deflector delivers motive fluid (air, steam) under high pressure into the passageway between the deflector and pipe. The fluid is directed by the inwardly inclined upper lip of the shell into the path of emissions from the waste gas pipe. Heat shields and noise shields are incorporated into the assembly. Additional whirling and turbulence is imparted to the stream of motive fluid by appropriate shaping of spacer plates securing the deflector to the waste gas pipe. The structure is less complex than previously known devices, has improved ease of maintenance, and gives excellent performance in smokeless flaring of waste gas.

Multilayer Nb 3 Sn superconducting shields

Abstract: Multilayer Nb 3 Sn shields have been designed, fabricated, and tested for use in low field, e.g. superconducting electronics, applications. Magnetic field profiles, shielding factors, and thermal effects are reported for these shields. The quality of the shields depends strongly on the reaction temperature used to form the Nb 3 Sn layers with lower reaction temperatures forming better quality shields. Nearly ideal behavior was observed with a reaction temperature of 750°C.

Conduction cooled ion laser

Abstract: The subject invention relates to a conduction cooled ion laser capable of producing higher output power. The device includes an insulated tube and a plurality of heat conducting members mounted in thermal contact with the wall of the tube. Primary and secondary ring gas barriers or shields project axially from the heat conducting members with the primary shield being located radially inward with respect to the secondary shield. The shields are mounted such that they axially overlap to define a reentrant configuration. The reentrant configuration allows for the operation of the laser at a higher power with the same voltage safety margin above the instability voltage.

Measurements of the Electrostatic and Electromagnetic Fields of Faraday-Shielded Half-Turn Loop-Type ICRF Antennae

Abstract: Detailed measurements of both the electrostatic and electromagnetic fields are performed for various types of Faraday shields mounted on PLT ion cyclotron range of frequencies (ICRF) antennae. The data show that the shields have little effect on the electromagnetic fields when the antenna is driven such that it is generating a constant total flux for the various cases. A new type of shield (Type II) is investigated that has no effect on the antenna inductance and performs equally as well as the conventional shields (Type I) in shielding out the electrostatic fields. Measurements indicate, for the shields investigated, that each layer of shield strips degrades the Q by approximately a factor of two.

Electromagnetic shielding properties of amorphous alloy shields for cathode ray tubes

Abstract: Because of the excellent soft magnetic properties of the amorphous alloy Fe40Ni38Mo4B18 (2826MB), we have made funnel‐shaped shields for cathode ray tubes by combining the amorphous ribbons and ferromagnetic powders via resin transfer molding composite technology. The electromagnetic shielding properties of shields were improved by increasing the thickness of ribbons and the weight percentage of ferromagnetic powders. For a shield with six‐layer ribbons, the maximum magnetic shielding effectiveness obtained near the applied magnetic field 2 Oe (dc and ac 60 Hz) was about 25–27 dB, and the magnetic shielding factors were improved to 27–30 dB by adding the ferromagnetic powders. After the field annealing of shields, the magnetic shielding effectiveness increased and the maximum values of 35–40 dB were shifted near the applied magnetic field 0.2 Oe. The electric field shielding effectiveness over the broadband spectrum 10 kHz–18 GHz was in the range 50–80 dB.

Material and Electromagnetic Properties of Faraday Shields for Ion Cyclotron Heating Antennas

Abstract: The Faraday shields for ion cyclotron antennas must transmit magnetic waves and absorb little RF power. To investigate these properties, we have constructed 27 Faraday shields in many configurations, including chevrons, tubes, straps, concentric rings, various layered shields, conventionally leafed straps, and replicas of the Faraday shields for ASDEX, the Joint European Torus (JET), TEXTOR, and Alcator-C. We have measured the magnetic flux and observed loading at various operating resistances by using dielectric sheets or magnetic-coupled loads. Each Faraday shield effects a net change in the characteristic inductance of the antenna, resulting in a reduction of wave coupling. However, the load experienced by the antenna is not always reduced because the Faraday shield itself acts as a load. We differentiate between these effects experimentally. The net result of the study is that the Faraday shields now in use cost up to a factor of 50% of coupling. This, of course, reduces the power handling capability by 50% as well. However, configurations exist that are easily cooled and result in a reduction of less than 5% in loading.

5cm, no iron ssc dipole 12m model cryostat thermal performance*

Abstract: A 12 m long model of a 5 cm costheta dipole cryostat has been constructed and its thermal performance measured. The model utilized heat intercepted fiberglass reinforced plastic posts to support the 12 m long, 4.5 K cold mass and the 10 and 80 K thermal shields. A superinsulation blanket system utilizing aluminized polyester with fiberglass mat spacing material was developed and installed on the 10 and 80 K thermal shields. The heat gain to 4.5, 10 and 80 K was measured. We have compared the results with the analytical predicted performance and it shows good agreement. The performance of the multilayer insulation system has been measured under several different system conditions and the results are reported. 6 refs., 5 figs.

Fabrication and performance of cylindrical iron shields for mri systems.

Abstract: Using analytic and experimental methods, we have investigated the design, fabrication,and performance of axially symmetric shields which minimize the field perturbation withinthe central bore of an MR magnet. Magnetic resonance shields have been built for 1.9tesla /60 cm bore and 1.5 tesla /100 cm bore superconducting magnets. The 1.9 T system isenclosed by a simple cylindrical shield having a weight of 49,000 pounds. The 1.5 T systemshield is a 100,000 pound tapered thickness cylinder with conic ends. The shields areconstructed from cold rolled steel sections which are welded in place at the magnet site.A low carbon, specially annealed steel with particularly desireable properties of inducedmagnetism has been employed. The 5 gauss line is constrained to a point 4.0 meters to theside of the 1.9 T magnet, 3.0 meters to the side of the 1.5 T magnet and 7.0 meters off theend of both magnets.IntroductionHigh field, large bore magnets used for magnetic resonance imaging and spectroscopy pro-duce magnetic fields which can influence the environment at distances far from the magnet.Within this sphere of influence, which may have a radius greater than 15 meters, ferrousobjects will become intensely magnetized and perturb the normally homogeneous field withinthe magnet. Consequently, many high field MR systems have been installed within large,free -standing buildings of a ferrous -free design which are remote from direct patient carefacilitiesl.Discontinuous asymmetrical iron shields enclosing high field MR magnets have been usedto constrain the magnet sphere of influence2. The return magnetic fields resulting frominduced shield magnetism perturb the uniform field within the magnet and can compromisesystem performance, particularly for spectroscopy applications. Using analytic and experi-mental methods, we have investigated the design, fabrication, and performance of axiallysymmetric shields which minimize the field perturbation within the central bore of the MRmagnet.MethodsWe have designed magnetic resonance shields for two magnetic resonance systems:

Magnetic shield of stationary induction apparatus

Abstract: PURPOSE:To prevent infiltration of magnetic flux into a tank by removing the gap between adjacent magnetic shields forming the end of the magnetic shield in a recessed or a projected shape. CONSTITUTION:In a tank 4 made of a magnetic material housing a stationary induction apparatus, plural unit magnetic shields 15-7-15-10 laminated with magneto-conductive plates are installed. Each unit magnetic shield has plural recessions at one end of the longitudinal direction and plural projections which correspond to the recessions at the other end. By engaging the recession and the projection of the ends of the adjacent unit magnetic shields, the gap between the adjacent unit magnetic shields is removed and infiltration of magnetic flux into the tank 4 can be prevented.

Magnetic shielding device for induction apparatus

Abstract: PURPOSE:To reduce sharply magnetic flux to flow into the tank of an induction apparatus, and to suppress loss to the minimum by a method wherein second magnetic shields adhered closely to first magnetic shields and having the large different fitting direction therefrom are arranged on the upper surfaces of the first magnetic shields equipped to the tank CONSTITUTION:Second magnetic shields 6 are arranged on the upper surfaces of first magnetic shields 4 adhering closely thereto, and changing the fitting direction large (at 90 deg) According to this construction, because magnetic flux is enabled to advance to the original direction of leakage magnetic flux passing the magnetic bodies 4a, 6a of the longitudinal and lateral directions, magnetic flux to pass through a tank 1 having an inferior magnetic loss characteristic is reduced sharply, and loss generated in the tank 1 can be made to the minimum

Magnetoresistance effect element wafer

Abstract: PURPOSE:To measure magnetoresistance effect element characteristics under the state of a wafer before assembly by arranging a magnetoresistance effect element having structure in which a magnetic thin-film sensor is interposed and both sides of the sensor are covered with magnetic thin-film shields and a magnetoresistance effect element having structure in which the magnetic thin-film shield on at least one side is removed CONSTITUTION:Magnetoresistance effect elements having structure in which magnetic thin-film sensors 3 are interposed and both sides of the sensors 3 are covered with magnetic thin-film shields 1, 1' are arranged to one parts, and magnetoresistance effect elements 6, 7 having structure in which the magnetic thin-film shields on at least one sides are disposed to other one parts A film such as a permalloy film is evaporated on a wafer 5, the permalloy film is removed completely in sections corresponding to the elements 6, 7, unnecessary sections are removed through etching according to patterns of the predetermined lower shields 1 in other sections, and the lower shields 1 are formed SiO2 lower insulating layers 2, the magnetoresistance effect sensors 3 and conductors 4 are shaped on the shields 1 SiO2 upper insulating layers 2' and the upper shields 1' are formed on these layers 2, sensors 3 and conductors 4

Improved multitrack magnetic head and method of manufacture

Abstract: This high-resolution multitrack magnetic head comprises, in a known manner, two castings 1a, 1b, in which grooves 5 receiving magnetic circuits 2a, 2b, and slots 6 receiving shields 3 are made The shields are glued into their slot and brace the castings To prevent dimensional variations in the air gap at high temperatures, free spaces 11 are provided in the bottom of the slots 6 allowing free expansion of the shields inside these slots

Comment on magnetic shielding in hydrogen masers

Abstract: In a previous article (Kunski and Vanier 1982, to be referred to as KV) the authors reported the results of measurements of the magnetic shielding characteristics of concentric cylindrical enclosures made of Moly Permalloy, such as are used in hydrogen masers (Kleppner et al 1965, Vanier 1982). The arrangement studied was a system of five shields spaced by 25.4 mm with the outside shield having external dimensions 762 mm length and 305 mm radius. In this comment, the authors report on the characteristics of these shields when used on the maser itself.