Showing papers on "Shields published in 1981"

Advanced radiative cooler with angled shields

Abstract: Recent demands for spaceborne sensor temperatures below 90 K are exceeding the capabilities of present passive radiative cooler designs. To improve cooling performance, a novel technique was developed to radiatively and conductively isolate the radiating plate from the spacecraft using low-emittance, highly specular angled radiation shields. An experimental test of the new shield concept verified its effectiveness and enabled calibration of a detailed thermal model. Based on the concept test results, performance predictions show that the Advanced Radiator can achieve lower temperatures, deliver more cooling power and be smaller and lighter than the best state-of-the-art coolers.

Grading means for high voltage metal enclosed gas insulated surge arresters

Abstract: Capacitance grading is provided within gas insulated lightning arresters containing stacked zinc oxide varistors by means of a grading ring electrically connected to the line terminal or, for arresters of the higher voltage ratings, by means of a plurality of telescoping external electrostatic shields. The shields are arranged so that the degree of overlap between sequential shields decreases from the line end to the ground end of the varistor stacks. The capacitance grading is provided by the degree of overlap between the sequential shields and the ratio of the radii of the overlapping shields.

Cleaning device for electrophotographic copier

Abstract: PURPOSE:To discharge the ozone around a photoreceptor efficiently by connecting the shields of Corotrons near a cleaner body and the housing of the cleaner, recovering the ozone into the cleaner by the air flow, etc. of fur brush rolls, and decomposing the same with an ozone filter. CONSTITUTION:A Corotron 9 for charging and a precleaning Corotron 10 are installed before and behind a cleaner body 2. The Corotrons 9, 10 consist of shields 9a, 10a of a channel shape in section of which the opening parts direct to a photoreceptor 1 side and corona wires 9b, 10b contained in these shields 9a, 10a. The respective shields are so installed that fine gaps 9c, 10c are formed between the opening edges of the shields and the surface of the photoreceptor 1. On the other hand, the air flow contg. the ozone sucked into dust collecting housing 2a by fur brush rolls 3 is decomposed and filtered when it passes through an ozone filter 12 and only the air is released into the atmosphere.

A Theoretical Analysis for Finite-Length Electromagnetic Shields of Superconducting Turbine Generators

Abstract: A lumped parameter circuit representations of finite length solid electromagnetic shields of superconducting turbine generators is developed. A three-dimensional magnetic field analysis is used to calculate the parameters of this representation. The shield lengths are freely chosen which increases the inherent accuracy and usefulness of the representation relative to previous approaches.. The analysis provides the basis for three-dimensional shield design

Shielding arrangement for a vacuum furnace

Abstract: The present invention is directed to graphite shields (or shields of other materials which may react chemically or be oxidized in a vacuum furnace but which when condensed do not readily conduct electricity) or graphite shield liners used to protect electrical insulating devices from having electrical shorting path means develop thereon.

Mosaic printing head with cross-talk prevention means

Abstract: A mosaic printing head with cross talk prevention means comprises a plurality of electromagnetic structure formed by magnetic circuits (39), each coupled to a coil (41) and closed by a movable armature (43), which at rest leave an air gap in the magnetic circuit. The magnetic circuits are radially distributed on a supporting member, very closely together at least with a certain portion. The flux leakage which occurs in these portions, due to the proximity of such portions, is avoided by using conductive non magnetic shields (42) partially surrounding such portions. The shields dinamically limit flux leakage transients, i.e. during the attraction of the armature, dueto the eddy currents induced by flux leakage. The shields are designed in order to be coupled with flux leakages and not with the main flux in the magnetic circuit.

Graphitic Heat Shields for Solar Probe Missions

Abstract: The feasibility of using a graphitic heat-shield system on a solar probe going to within 4 solar radii of the center of the sun is investigated. An analysis of graphite vaporization, with commonly used vaporization coefficients, indicates that the maximum mass-loss rate from a conical shield as large as 4 m in diameter can be kept low enough to avoid interference with measurements of the solar environment. In addition to the mass-loss problem, the problem of protecting the payload from the high-temperature (up to 2300 K) primary shield must be solved. An analysis of radiation exchange between concentric disks provides a technique for designing the intermediate shielding. The technique is applied to the design of a system for the Starprobe spacecraft, and it is found that a system with 10 shields and a payload surface temperature of 600 K will have a payload diameter of 2.45 m. Since this is 61% of the 4-m diameter of the primary shield, it is concluded that a graphitic heat-shield system is feasible for the Starprobe mission.

Rapid determination of linearity in a dose calibrator

Abstract: A method of testing dose calibrator linearity comprising the steps of serially interposing a plurality of shields between the sample and detector, each shield having a given thickness to absorb a desired fraction of the radiation; measuring the activity of the sample as attenuated by the shields; calculating the actual activity of the sample at each level of attenuation; and comparing the measured activities with the calculated activities. For carrying out the method several embodiments of shields are described.

An accurate method of calculating multilayer, multimaterial cylindrical magnetic shields

Abstract: The basic concepts of shielding theory have existed since the last century [1,2] There have been many publications on the subject of magnetic shielding, treating the case of shielding apparatus from static fields by means of multiple concentric shields and deriving several principles of fundamental importance Unfortunately, however, theory has been applied to only the most ideal shield configurations, for the case of constant permeability [3-5] This paper covers the analysis of shielding effectiveness of variable Permeability cylindrical shielded enclosures for the DC magnetic field case When the permeability is a function of magnetic induction, the simple boundary solution for spherical or cylindrical shields can no longer be applied since the induction, through the permeability, is caused to vary as much as two orders of magnitude, causing nonuniformity in the field in the cavity and inside the shield Thus, the permeability of the shielding material is considered as a function of the induction, and a significantly improved method of estimating the induction and permeability of the shield is presented The effects of a multiple-shell geometry are treated in the equations of this analysis This method gives fast, accurate results and can be run on a small computer for shielding optimization Results of these magnetic field calculations allowed the selection of optimization criteria and showed how system requirements could be met by choosing a suitable shell structure arrangement Experimental measurements on real materials for various shell structures confirmed the accuracy of this method

Phase 02 report on effectiveness of shelf couplers, head shields and thermal shields

Abstract: The Class DOT 112(114) tank cars retrofitted with shelf couplers, head shields, and thermal shields under HM-144 have now had sufficient service experience to permit an assessment of their effectiveness. Specifically, the fleet of 112(114) cars has had about 2-3/4 fleet-years experience with shelf couplers and 1-3/4 fleet-years experience with head shields and thermal shields. Accident data for the last 2-1/4 years (average fleet-years the cars have been equipped) are compared to accident data for the preceding 14 years. It is found that the frequency of head punctures has been reduced to about one-seventh the previous rate, and the frequency of fire induced ruptures has been reduced to about one-third the previous rate. Shell punctures have decreased, but the limited number of cases precludes quantifying the amount. Considering all cases of punctures and ruptures combined, and normalizing on the basis of car population, the frequency has dropped to about one-fourth the previous rate.

Nucleonic analysis of the ETF neutral-beam-injector-duct and vacuum-pumping-duct shields

Abstract: A nucleonic analysis of the Engineering Test Facility neutral-beam-injector-duct and vacuum-pumping-duct shields has been made using a hybrid Monte Carlo/discrete-ordinates method. This method used Monte Carlo to determine internal and external boundary surface sources for subsequent discrete-ordinates calculations of the neutron and gamma-ray transport through the shields. Confidence was provided in both the hybrid method and the results obtained through a comparison with three-dimensional Monte Carlo results. Also determined in the analysis were the energy and angular distributions of neutrons and gamma rays entering the neutral-beam-injector duct from the toroidal plasma chamber, as well as exiting the duct into the neutral-beam-injector chamber. In addition, the energy and angular distributions of neutrons entering the vacuum-pumping chamber were determined.

Novel design of pressure vessels and thermal shields in coal gasifiers

Abstract: This report describes a proposed solution to two outstanding problems in commercial-sized coal gaSifiers, namely, detecting and locating any deterioration in the refractory thermal barrier and the construction of a safe pressure vessel utilizing advanced carbo~ fiber composite technology. DeSign considerations are given for a typical gasifier some 30 feet in diameter by 150 feet tall with a maximum internal temperature and pressure of 2500°F and'1500 psi respectively. A system of computer controlled cooling circuits is deployed between the refractory barrier and the exterria 1 1 i ghtwe i ght pressure vesse 1. Multiple levels of redundancy are built in to guard against any component failure. 'Through th~ sensing of coolant temperature and the modulation of coolant flow, a map of heat flux distribution over the gasifier wall may be generat~d with a spatial resolution of about 5 feet. It seems possible to maintain the coolant temperature rise by no more than 90°F with only a modest amount of coolant flow.

The Use of a Small Accelerator as a Source of 14-MeV Neutrons for Shielding Studies

Abstract: It is important in calculating complex shields such as those proposed for the fusion reactors to ascertain that the neutron cross-section data sets used in the calculations are as accurate as possible and that the calculational methods used to transport the neutrons are as reliable as practical. To assure that both these criteria are met, a project at the Oak Ridge National Laboratory (ORNL) is being conducted in which a small accelerator is used to provide 14-MeV neutrons via the T(d, n)4He reaction and an NE-213 detector is used to measure the neutron and gamma-ray pulse-height spectra of the radiations transported through and/or created in very thick laminated shields of stainless steel (type 304) and borated polyethylene. To produce the neutron flux required, the targets are made by depositing about 4 mg/cm2 of TiT onto a 1.27-cm circular area of a O.254-cm thick copper disk. The NE-213 detector is operated in standard, state-of-the-art electronic circuits. A surface-barrier alpha counter and a small NE-213 detector are located permanently at a distance of about 150 cm from the target to monitor the reaction rate in the target. The pulse-height data are unfolded to produce energy spectra by using the computer program FERD. These results are then compared almost immediately with spectra obtained using two-dimensional radiation transport methods incorporating 53-neutron, 21-gamma-ray energy-group cross section data derived from the VITAMIN-C data set (ENDF/B). Laminated stainless-steel and borated polyethylene shields having thicknesses up to 412 g/cm2 have been measured.