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Magnetization and critical currents of NbTi wires with fine filaments

Description: In high energy accelerators such as the SSC, the magnetization of the superconductor is an important component in determining the harmonic fields at injection (approx.0.3T). In an effort to reduce these residual fields, interest has focused on NbTi conductors with fine filaments which are expected to have a reduced magnetization as dictated by the critical state model. With this in view, the magnetization and critical currents were measured at 4.3K for a set of NbTi wires with filament diameters, d, ranging from 1.0 to 5.0 microns. The data show that, although the magnetization scales linearly with d, it does not do so with the product J/sub c/d for d less than 3 ..mu..m. However, at these d values, the critical transport current density, J/sub c/ of NbTi was observed to decrease rapidly as a function of d. The origin of this J/sub c/ degradation and its effect on the scaling of magnetization within the framework of the critical state model is explored. We also examine the question of the observed asymmetry of the hysteretic magnetization.
Date: January 1, 1985
Creator: Ghosh, A.K. & Sampson, W.B.
Partner: UNT Libraries Government Documents Department

Influence of Proton Irradiation on Angular Dependence of Second Generation (2G)HTS

Description: In the Facility for Rare Isotope Beams (FRIB) the quadrupoles in the fragment separator are exposed to very high radiation and heat loads. High Temperature Superconductors (HTS) are a good candidate for these magnets because they can be used at {approx}30-50 K and tolerate higher heat generation than Nb-Ti magnets. Radiation damage studies of HTS wires are crucial to ensure that they will survive in a high radiation environment. HTS wires from two vendors were studied. Samples of 2G HTS wires from SuperPower and American Superconductor (ASC) were irradiated with a 42 {mu}A, 142 MeV proton beam from the Brookhaven Linac Isotope Producer (BLIP). The angular dependence of the critical current was measured in magnetic fields at 77K.
Date: May 1, 2011
Creator: Shiroyanagi, Y.; Greene, G.; Gupta, R. & Sampson, W.
Partner: UNT Libraries Government Documents Department

Critical current studies on fine filamentary NbTi accelerator wires

Description: The magnets for the Superconductig Super Collider, a high energy proton colliding beam accelerator, require a superconductor with very high current density (>2400 A/mm/sup 2/ at 5 T) and very small filaments (approx. 2..mu..m in diameter). Previous work has shown that by controlling the formation of Cu/sub 4/Ti compound particles on the filament surfaces it is possible to make fine filamentary NbTi wire with high critical current density. The performance of multi-filamentary wire is characterized by the current density and the quantity ''n'' which describes the superconducting-normal transition. Micrographs of wires having high J/sub c/ and high n show smooth, uniform filaments. Recently wires of very high critical current and high n have been produced in experimental quantities by commercial manufactures.
Date: January 1, 1985
Creator: Garber, M.; Suenaga, M.; Sampson, W.B. & Sabatini, R.L.
Partner: UNT Libraries Government Documents Department

Magnetization, critical current, and injection field harmonics in superconducting accelerator magnets

Description: The very large energy ratio of machines such as the SSC dictates rather low injection field (for 6T, 20 TeV it is approximately 0.3T). Since the harmonic content at such low fields is largely determined by magnetization currents in the superconductor, the random errors depend on the uniformity of the superconducting wire. In principle the magnitude of the residual fields can be reduced indefinitely by using finer filaments, but in practice there is a lower limit of a few microns. We have compared the injection field harmonics for a number of accelerator dipoles with magnetization measurements made on samples of the conductor used to wind the coils. In addition both the magnetization and harmonics have been compared with short sample critical current measurements made at 5T. The results indicated that an accurate estimate of the variation in injection field harmonics can only be obtained from direct measurements of the magnetization of the cable. It appears feasible to use such measurements to ''shuffle'' magnets for a large accelerator by predicting the low field properties of a magnet before actually winding the coils. 10 refs., 4 figs., 2 tabs.
Date: January 1, 1985
Creator: Ghosh, A.K.; Sampson, W.B. & Wanderer, P.
Partner: UNT Libraries Government Documents Department

Effect of Cu/sub 4/Ti compound formation on the characteristics of NbTi accelerator magnet wire

Description: High critical current density, J/sub c/ > 2500 A/mm/sup 2/, and small filament diameter, d approx. 3 ..mu..m, are required in multifilamentary NbTi wire used for superconducting accelerator magnets. Wires obtained from various commercial sources had J/sub c/'s in the range 1000 to 2800 A/mm/sup 2/ amd d's in the range 1 to 23 ..mu..m. The filaments were examined by means of scanning electron microscopy in order to determine the reason for the variation in J/sub c/. It was found that the filaments in high J/sub c/ wires had clean smooth surfaces and uniform cross section along their lengths. Filaments in low J/sub c/ wires show formation of Cu/sub 4/Ti compound particles on their surfaces and large variations in cross section. The lower critical current measured in these wires is believed to be largely due to this effect. The superconducting-normal state transition is relatively wide in these wires.
Date: January 1, 1985
Creator: Garber, M.; Suenaga, M.; Sampson, W.B. & Sabatini, R.L.
Partner: UNT Libraries Government Documents Department

Correlation of superconductor strand, cable, and dipole critical currents in CBA magnets

Description: A calibration between vendor critical current data for 0.0268'' diameter superconductor strand supplied to Fermilab, and the BNL 10/sup -12/..cap omega..cm critical current specification is presented. Vendor critical current data for over 400 Fermilab type billets are shown, both as supplied by the vendor and converted to BNL units. Predictions of cable critical current are made using the sum of the critical currents of the 23 strands, where all strands from the same half billet are assigned the same critical current. The measured critical current shows excellent correlation to the predicted value and is approximately 14 +- 2 percent below it. Colliding Beam Accelerator (CBA) full length dipoles reach the conductor critical current limit, essentially without training. Magnet performance is predictable from the measured critical current of a short sample of cable to within 2%.
Date: January 1, 1982
Creator: Tannenbaum, M.J.; Garber, M. & Sampson, W.B.
Partner: UNT Libraries Government Documents Department

ISABELLE insertion quadrupoles

Description: Beam focussing and control at the beam intersection regions of ISABELLE is accomplished by a number of superconducting insertion quadrupoles. These magnets differ from the standard ISABELLE quadrupoles in various ways. In particular, the requirements of limited space near the intersections and aperture for beam extraction impose constraints on their configuration. To achieve optimum beam focussing and provide tuning flexibility calls for stronger quadrupole trim windings than those in the standard quadrupoles. The magnetic and mechanical design of the insertion quadrupoles and their associated correction and steering windings to accomplish the above tasks is presented.
Date: January 1, 1979
Creator: Kaugerts, J.; Polk, I.; Sampson, W. & Dahl, P.F.
Partner: UNT Libraries Government Documents Department

ISABELLE full scale dipoles

Description: Data are presented on the various cosine theta type magnet models constructed at BNL in the development of ring magnets for ISABELLE, a pair of intersecting 200 GeV proton accelerating storage rings. The rings are to be filled with 30 GeV protons from the AGS and then accelerated to 200 GeV. The acceleration period is a 120 sec ramp from approximately 0.5 T to 4 T. The effect of mechanical precompression on training was studied by varying the interference fit between the coil (ISA IV) and its iron shield. The results were used to optimize the mechanical design of the full-size magnet models. (auth)
Date: January 1, 1975
Creator: McInturff, A. D.; Dahl, P. F.; Kassner, D.; Lasky, C.; Robins, K. & Sampson, W. B.
Partner: UNT Libraries Government Documents Department

Design, Construction and Test of Cryogen-Free HTS Coil Structure

Description: This paper will describe design, construction and test results of a cryo-mechanical structure to study coils made with the second generation High Temperature Superconductor (HTS) for the Facility for Rare Isotope Beams (FRIB). A magnet comprised of HTS coils mounted in a vacuum vessel and conduction-cooled with Gifford-McMahon cycle cryocoolers is used to develop and refine design and construction techniques. The study of these techniques and their effect on operations provides a better understanding of the use of cryogen free magnets in future accelerator projects. A cryogen-free, superconducting HTS magnet possesses certain operational advantages over cryogenically cooled, low temperature superconducting magnets.
Date: March 28, 2011
Creator: Hocker, H.; Anerella, M.; Gupta, R.; Plate, S.; Sampson, W.; Schmalzle, J. et al.
Partner: UNT Libraries Government Documents Department

The effect of magnetic impurities and barriers on the magnetization and critical current of fine filament NbTi composites

Description: It has been shown that the highest critical currents in fine filament NbTi conductors are obtained when the filaments are closely spaced. However, the filaments in a composite with a high purity copper matrix tend to be coupled via the ''proximity effect'' as the filament spacing is reduced leading to large magnetization at low fields. To reduce the ''proximity'' coupling, trial billets of NbTi have been fabricated with Cu-30% Ni matrix, Cu-0.5% Mn matrix and one with a Ni barrier around the filaments. Wires drawn from these billets have shown that this interfilament coupling can be suppressed for very small filament separations. A full sized commercial billet with Cu-0.5% Mn matrix demonstrates that high J/sub c/ conductors with filament size approx.1 to 5 ..mu..m can be fabricated which show no interfilament coupling at low fields.
Date: January 1, 1987
Creator: Ghosh, A.K.; Sampson, W.B.; Gregory, E.; Kreilick, S. & Wong, J.
Partner: UNT Libraries Government Documents Department

Development of high efficiency (14%) solar cell array module. First quarterly report, November 29, 1978-March 15, 1979

Description: The development of the high efficiency, P/N silicon solar cells has begun. The best efficiency achieved to date on the 3'' diameter cell was 15.6% at AM1 and 28/sup 0/C, slightly below that of 16.5% required for the fabrication of 14% efficiency module. Work is continuing on the cell development, with efforts concentrating on junction formation and back surface field application. The design of the module was completed utilizing 120 3'' diameter cells, Sunadex glass as the superstrate, polyvinyl butyral as the encapsulant, extruded aluminum channel for framing, and Teflon insulated flexible leads as the electrical terminals. The design of the production tooling has been submitted for design review. The tooling consists of: (1) back contact soldering machine, (2) vacuum pickup, (3) anti-reflective coating tooling, and (4) test fixture.
Date: January 1, 1979
Creator: Iles, P.A.; Khemthong, S.; Olah, S.; Sampson, W.J. & Ling, K.S.
Partner: UNT Libraries Government Documents Department

Development of high efficiency (14%) solar cell array module. Third quarterly report, July 15, 1979-November 15, 1979

Description: Most effort was concentrated on development of procedures to provide large area (3'' diameter) high efficiency (approx. 15.5% AM1, 28/sup 0/C) P/N solar cells. These efficiencies had been obtained for 2 x 2 cm area cells, but tests showed that the problem was not reduced silicon quality near the edges of the larger slices. The problems were in optimizing the back-surface field (BSF) process, and its possible interaction with the shallow P+ layer formation. Towards the end of this reporting period a promising process sequence had been identified and is being tested. The module design has been finalized. One hundred and twenty (120) cells will be connected eight (8) in parallel and fifteen (15) in series. The designs and tooling phases have been completed and are awaiting completion of the cells.
Date: January 1, 1980
Creator: Iles, P.A.; Khemthong, S.; Olah, S.; Sampson, W.J. & Ling, K.S.
Partner: UNT Libraries Government Documents Department

Development of high efficiency (14%) solar cell array module. Second quarterly report, March 15-July 15, 1979

Description: Work on the development of large area, high efficiency P/N solar cells is described. The best performance achieved to-date on 3'' diameter cells is 15.6% at AM1 and 28/sup 0/C. Factors contributing toward the poor performance have not been identified and isolated. Work is continuing. Minor modifications have been incorporated in the modular design. The 120 cells will be connected 8 in parallel and 15 in series to enhance the reliability of the modules. As a result of the changes, two junction boxes will be required as the P and N terminals will come out from the opposite sides of the module. Designs for back contact soldering machine, vacuum pick-up, AR coating tooling, and test fixture have been completed. Fabrication of tooling has begun.
Date: January 1, 1979
Creator: Iles, P.A.; Khemthong, S.; Olah, S.; Sampson, W.J. & Ling, K.S.
Partner: UNT Libraries Government Documents Department

BNL superconducting storage ring magnet update

Description: The various performance data, design and specifications for the storage ring and experimental series dipole and quadrupole magnets as well as the working line and correction coil systems are reported. The working line system includes the closed orbit dipoles, the quadrupole trim, sextupoles, octapoles, decapoles and duodecapoles. These are the magnets in the standard subunits of the Brookhaven National Laboratory Intersecting Storage Ring Accelerator ''ISABELLE.''
Date: January 1, 1978
Creator: McInturff, A.D.; Bleser, E.; Dahl, P.F.; Kaugerts, J.; Robins, K. & Sampson, W.
Partner: UNT Libraries Government Documents Department

Magnetic field measurements on ISABELLE storage ring magnets

Description: In 1978 the magnetic field shapes of six ISABELLE prototype dipole magnets were measured in detail. All the harmonic terms that are forbidden by symmetry in dipole magnets are found to have values that are zero to within the allowed tolerances. This result indicates that the random errors in conductor placement are within tolerances and that the assembly techniques are satisfactory in this regard. However, the first allowed error term in a dipole magnet, the sextupole term, is much too large, and varies greatly from magnet to magnet resulting in field errors at the edge of the desired good field region that are 10/sup -3/ of the central field value, whereas the tolerable field errors are of the order of 10/sup -4/ of the central field value. This large sextupole term has been traced to assembly errors which yield a coil assembly which instead of being circular in cross section is racetrack shaped, with the vertical axis being 10 to 20 thousandths of an inch greater than the horizontal axis. This problem will be corrected in the future production series.
Date: January 1, 1979
Creator: Bleser, E.; Dahl, P.; Gardner, D.; Kaugerts, J.; McInturff, A.; Robins, K. et al.
Partner: UNT Libraries Government Documents Department

The Effect of Axial Stress on YBCO Coils

Description: The large aspect ratio of typical YBCO conductors makes them ideal for constructing solenoids from pancake style coils. An advantage of this method is that each subunit can be tested before assembly into the finished magnet. The fact that conductors are available in relatively short lengths is another reason for using such a fabrication technique. The principal drawback is the large number of joints required to connect the coils together. When very high field solenoids such as those contemplated for the muon collider are built in this way the magnetic forces between pancakes can be very large. Extensive measurements have been made on the effect of stress on short lengths of conductor, but there is little or no data on the effect of intercoil loading. The experiment described in this paper was designed to test the ability of YBCO coils to withstand these forces. A spiral wound 'pancake' coil made from YBCO coated conductor has been stressed to a pressure of 100MPa in the axial direction at 77K. In this case axial refers to the coil so that the force is applied to the edge of the conductor. The effect on the critical current was small and completely reversible. Repeatedly cycling the pressure had no measureable permanent effect on the coil. The small current change observed exhibited a slight hysteretic behaviour during the loading cycle.
Date: March 28, 2011
Creator: Sampson, W.; Anerella, M.; Cozzolino, J.P.; Gupta, R.C.; Shiroyanagi, Y. & Evangelou, E.
Partner: UNT Libraries Government Documents Department