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Cryogenic techniques for large superconducting magnets in space

Description: A large superconducting magnet is proposed for use in a particle astrophysics experiment, ASTROMAG, which is to be mounted on the United States Space Station. This experiment will have a two-coil superconducting magnet with coils which are 1.3 to 1.7 meters in diameter. The two-coil magnet will have zero net magnetic dipole moment. The field 15 meters from the magnet will approach earth's field in low earth orbit. The issue of high Tc superconductor will be discussed in the paper. The reasons for using conventional niobium-titanium superconductor cooled with superfluid helium will be presented. Since the purpose of the magnet is to do particle astrophysics, the superconducting coils must be located close to the charged particle detectors. The trade off between the particle physics possible and the cryogenic insulation around the coils is discussed. As a result, the ASTROMAG magnet coils will be operated outside of the superfluid helium storage tank. The fountain effect pumping system which will be used to cool the coil is described in the report. Two methods for extending the operating life of the superfluid helium dewar are discussed. These include: operation with a third shield cooled to 90 K with a sterling cycle cryocooler, and a hybrid cryogenic system where there are three hydrogen-cooled shields and cryostat support heat intercept points. Both of these methods will extend the ASTROMAG cryogenic operating life from 2 years to almost 4 years. 14 refs., 8 figs., 4 tabs.
Date: December 1, 1988
Creator: Green, M.A.
Partner: UNT Libraries Government Documents Department

A large superconducting detector magnet without an iron return path

Description: This paper describes a detector magnet which returns flux between the coils rather than through an iron return path. This actively shielded, uniform field 2 T magnet can be fabricated in separate parts which can be manufactured on the SSC site. This magnet can be built so that central field is uniform enough to permit a TPC detector to be used without iron poles. The field outside of the coil can be made to fall of as R/sup /minus/N/ power where N approaches 9. A major advantage of the magnet described in the paper is that there is no pole piece to block the particle jets emanating from the collision region in the forward and backward directions. Inexpensive materials such as earth and concrete can be used to provide the mass needed to analyze particles such as mu mesons. As a result, problems such as experimental hall subsidence can be reduced. Perhaps the cost of such an experiment can also be reduced. This type of magnet would require experimenters to rethink their experimental concepts. 8 refs., 5 figs., 2 tabs.
Date: February 1, 1989
Creator: Green, M.A.
Partner: UNT Libraries Government Documents Department

Use of high current density superconducting coils in fusion devices

Description: Superconducting magnets will play an important role in fusion research in years to come. The magnets which are currently proposed for fusion research use the concept of cryostability to insure stable operation of the superconducting coils. This paper proposes the use of adiabatically stable high current density superconducting coils in some types of fusion devices. The advantages of this approach are much lower system cold mass, enhanced cryogenic safety, increased access to the plasma and lower cost. (MOW)
Date: November 1, 1979
Creator: Green, M.A.
Partner: UNT Libraries Government Documents Department

Large superconducting detector magnets with ultra thin coils for use in high energy accelerators and storage rings

Description: The development of a new class of large superconducting solenoid magnets is described. High energy physics on colliding beam machines sometimes require the use of thin coil solenoid magnets. The development of these magnets has proceeded with the substitution of light materials for heavy materials and by increasing the current density in the coils. The Lawrence Berkeley Laboratory has developed a radical approach to the problem by having the coil operate at very high current densities. This approach and its implications are described in detail.
Date: August 1, 1977
Creator: Green, M.A.
Partner: UNT Libraries Government Documents Department

Field generated within the SSC magnets due to persistant currents in the superconductor

Description: This report presents the results of a number of computer studies of the magnetic fields generated by persistent circulating currents in the superconductor of superconducting dipoles. These magnetic fields are referred to as residual fields throughout this report. Since the field generated by persistent currents have a hysteric behavior, they are analagous to the residual filed found in iron bound conventional solenoids. The residual field calculations presented in this report were done using the LBL SCMAG4 computer code. This code has not been well tested against measured data, but a comparison with measured CBA data given in this report suggests that good agreement is possible. The residual fields generated by persistent superconducting currents are rich in higher multipoles. This is of concern to the accelerator designer for SSC. This report shows the effect of various superconductor parameters and coil parameters on the magnitude and structure of the residual fields. The effect of the magnet charging history on residual fields is aldo discussed. 14 references.
Date: January 1, 1984
Creator: Green, M.A.
Partner: UNT Libraries Government Documents Department

Modeling the behavior of oriented permanent magnet material using current double theory

Description: This paper presents a method for modeling two dimensional dipoles, quadrupoles and other higher multipoles built using oriented permanent magnet materials such as samarium cobalt (one of the rare earth cobalt REC materials). The technique presented here uses complex current doublet to model the magnetized material. This technique can be used in conjunction with an infinitely permeable circular iron shield which lies outside the REC material. Examples of two types of dipoles and quadrupoles are presented in this report. 15 refs., 4 figs., 1 tab.
Date: November 1, 1987
Creator: Green, M.A.
Partner: UNT Libraries Government Documents Department

Passive superconductor: A viable method of controlling magnetization multipoles in the SSC dipole

Description: At injection, the magnetization of the superconductor produces the dominant field error in the SSC dipole magnets. The field generated by magnetization currents in the superconductor is rich in higher symmetric multipoles (normal sextupole, normal decapole, and so on). Pieces of passive superconductor properly located within the bore of the dipole magnet can cancel the higher multipoles generated by the SSC dipole coils. The multipoles generated by the passive superconductor (predominantly sextupole and decapole) are controlled by the angular and radial location of the superconductor, the volume of superconductor, and the size of the superconducting filaments within the passive conductor. This paper will present the tolerances on each of these factors. The paper will show that multipole correction using passive superconductor is in general immune to the effects of temperature and magnetization decay due to flux creep, provided that dipole superconductor and the passive correction superconductor are properly specified. When combined with a lumped correction system, the passive superconductor can be a viable alternative to continuous correction coils within the SSC dipoles. 20 refs., 8 figs., 2 tabs.
Date: February 1, 1989
Creator: Green, M.A.
Partner: UNT Libraries Government Documents Department

Generation of the J/sub c/, H/sub c/, T/sub c/ surface for commercial superconductor using reduced-state parameters

Description: This report presents a method for calculating the J/sub C/, H/sub C/, T/sub C/ surface for Type II Superconductors. The method requires that one knows T/sub C/ at zero current and field, H/sub c2/ at zero current and temperature, and J/sub c/ at at least one temperature and field. The theory presented in this report agrees with the measured data quite well over virtually the entire J/sub c/, H/sub c/, T/sub c/ surface given the value of J/sub c/ versus H at one or two temperatures. This report presents calculated and measured values of J/sub c/ versus T and B for niobium titanium, niobium zirconium, niobium tin, niobium titanium tin, niobium tantalum tin, vanadium zirconium hafnium, and vanadium gallium. Good agreement of theory with measured data was obtained for commercial niobium titanium and niobium tin. 76 refs., 26 figs., 6 tabs.
Date: April 1, 1988
Creator: Green, M.A.
Partner: UNT Libraries Government Documents Department

Control of the fields due to superconductor magnetization in the SSC (Superconducting Super Collider) magnets

Description: Field uniformity of better than one part in 10,000 is required for the dipole magnets for the Superconducting Super Collider (SSC). The high field dipole and quaddrupole magnets proposed for the SSC generate higher multipole components of field due to magnetization (persistent currents) in the superconductor. When the superconductor filament diameter is of the order of 20..mu..m, the sextupole term alone is about 17 parts in 10,000 at an injection induction of 0.3 tesla in the SSC dipole magnets at a radius of 1 cm. This paper shows calculations of the magnetization phenomena which agree very well with magnetic measurement. Several passive methods for removing the sextupole component and higher components of the field generated by magnetization of the superconductor in the SSC dipole magnets are presented in the paper.
Date: September 1, 1986
Creator: Green, M.A.
Partner: UNT Libraries Government Documents Department

Quench protection and design of large high-current-density superconducting magnets

Description: Although most large superconducting magnets have been designed using the concept of cryostability, there is increased need for large magnets which operate at current densities above the cryostable limit (greater than 10/sup 8/ Am/sup -2/). Large high current density superconducting magnets are chosen for the following reasons: reduced mass, reduced coil thickness or size, and reduced cost. The design of large high current density, adiabatically stable, superconducting magnets requires a very different set of design rules than either large cryostable superconducting magnets or small self-protected high current density magnets. The problems associated with large high current density superconducting magnets fall into three categories; (a) quench protection, (b) stress and training, and (c) cryogenic design. The three categories must be considered simultaneously. The paper discusses quench protection and its implication for magnets of large stored energies (this includes strings of smaller magnets). Training and its relationship to quench protection and magnetic strain are discussed. Examples of magnets, built at the Lawrence Berkeley Laboratory and elsewhere using the design guidelines given in this report, are presented.
Date: March 1, 1981
Creator: Green, M.A.
Partner: UNT Libraries Government Documents Department

A design for a combined function superconducting dipole for a muon collider FFAG accelerator

Description: The acceleration stages for a muon collider require that the muons be accelerated within a given ring in fewer than twenty turns. One type of accelerator that appears to be attractive for a synchrotron that accelerates the muon a factor of four in energy in a few turns is the Fixed Field Alternating Gradient (FFAG) type of accelerator. As the energy of the muon beam increases, the muons move toward a higher field region of a DC combined function dipole. The following dipole and quadrupole magnet characteristics are required for a muon FFAG machine to be successful: (1) The dipole will be a fixed field dipole with an impressed quadrupole and sextupole field. There may or may not be separate quadrupoles that mayor may not have added sextupole windings. (2) The horizontal aperture of the required good field region is wider than the vertical aperture of the required good field region. (3) The magnet is relatively short, so that the conventional SSC type of superconducting dipole or quadrupole ends can not be used. The field at the end of the magnet must fall off abruptly within the distance of less than one vertical aperture. For a magnet that is 400 mm long, the end region can be no more than 80 mm long. (4) The structure of the integrated field within the end region must be the same as the structure of the two-dimensional filed at the center of the magnet. A very preliminary design concept for a FFAG combined function dipole is presented in this paper.
Date: September 10, 1999
Creator: Green, M.A.
Partner: UNT Libraries Government Documents Department

Combining magnetic shielding and cryopumping for a neutral beam source

Description: This paper describes a feasible geometry for the shield/cryopump for a TFTR/Doublet type of neutral beam source, summarizes some of the design parameters, and compares the performance, fabrication, and operating cost of such a system with a more conventional system.
Date: October 1, 1979
Creator: Tanabe, J. & Green, M.A.
Partner: UNT Libraries Government Documents Department

2 meg-ampere prototype levitated coil for multipole fusion

Description: The coils major diameter is 1.0 meter and it occupies a cross-section which is about 0.2 meter minor in diameter. The prototype coil will carry four times the current of the largest such magnet built to date. As a result, the peak induction in the coil is about 8 T and the stored magnetic energy will be around 3 MJ. The paper describes the proposed Nb/sub 3/SN superconductor, the quench protection system which is based on the LBL shorted secondary concept, the isochroic refrigeration storage system which stores about 5 kJ of refrigeration between 4.5/sup 0/K and 7/sup 0/K, and the persistent switch.
Date: November 1, 1979
Creator: Green, M.A. & Glueck, R.
Partner: UNT Libraries Government Documents Department

Some options for the muon collider capture and decay solenoids

Description: This report discusses some of the problems associated with using solenoid magnets to capture the secondary particles that are created when an intense beam of 8 to 10 GeV protons interacts with the target at the center of the capture region. Hybrid capture solenoids with inductions of 28 T and a 22T are described. The first 14 to 15 T of the solenoid induction will be generated by a superconducting magnet. The remainder of the field will be generated by a Bitter type of water cooled solenoid. The capture solenoids include a transition section from the high field solenoid to a 7 T decay channel where pions and kaons that come off of the target decay into muons. A short 7 T solenoidal decay channel between the capture solenoid system and the phase rotation system is described. A concept for separation of negative and positive pions and kaons is briefly discussed.
Date: November 1, 1995
Creator: Green, M.A.
Partner: UNT Libraries Government Documents Department

The effect of muon decay on the design of dipoles and quadrupoles for a muon collider

Description: The decay of muons to neutrinos and electrons can cause heating in the superconducting dipoles and quadrupoles in the muon collider acceleration rings and the colliding beam ring. The problem is particularly acute in the colliding beam ring where heating in the magnets can be high as 2.4 kW per meter in the bending magnets of muon collider ring with 2 TeV mu minus beams with 2.22{times}10{sup 12} particles per bunch at a repetition rate of 30 Hz. The energy deposited within the helium temperature region must be reduced at least three orders of magnitude in order for the refrigeration system to begin to keep up with the heat load. Beam heating from muon decay will require changes in dipole design from traditional cosine theta (or intersecting ellipse) design used in the SSC magnets. Some dipole and quadrupole design options are presented in this report for both the accelerator rings and the colliding beam rings.
Date: November 1, 1995
Creator: Green, M.A.
Partner: UNT Libraries Government Documents Department

Some conceptual designs for a LASSY spectrometer magnet

Description: The LASSY spectrometer is a gas filled spectrometer (hydrogen or helium at a pressure of about 1 torr). The design bending power for the primary bending magnet for the spectrometer will have an induction bend radius product of 2.5 tesla-meters. In order to increase the acceptance of the spectrometer, the bending magnet system must be located close to the target where the desired nuclei are created. The spectrometer magnet system must consist of both bending and focusing elements so that the wide acceptance of particles can be brought to a focus at the analysis point that is down stream from the last magnet element. In order improve the spectrometer resolution and to catch the shortest lived nuclei, the length of the magnet system must be as short as possible. The length for the LASSY spectrometer magnet system from the target to the analysis point has been set at 2.5 meters or less. To improve the resolution of the spectrometer, the bending angle for bending magnet system must be increased to close to 180 degrees. In order to achieve a large bending angle and a short magnet system length, the bending induction must be above 3 tesla and the focusing elements must be combined with the bending elements. As a result, a LASSY spectrometer will have bending magnet with a bending angle from 140 to 170 degrees. This magnet win be combined with one or more focusing magnets (a straight dipole in some places and a combined function dipole in other places). The result is a single superconducting bending magnet with one or more quadrupoles incorporated within the large angle bending magnet.
Date: September 1, 1995
Creator: Green, M.A.
Partner: UNT Libraries Government Documents Department

Radiation and gas conduction heat transport across a helium dewar multilayer insulation system

Description: This report describes a method for calculating mixed heat transfer through the multilayer insulation used to insulate a 4 K liquid helium cryostat. The method described here permits one to estimate the insulation potential for a multilayer insulation system from first principles. The heat transfer regimes included are: radiation, conduction by free molecule gas conduction, and conduction through continuum gas conduction. Heat transfer in the transition region between the two gas conduction regimes is also included.
Date: October 10, 1994
Creator: Green, M.A.
Partner: UNT Libraries Government Documents Department

A superconducting linear motor drive for a positive displacement bellows pump for use in the g-2 cryogenics system

Description: Forced two-phase cooling of indirectly cooled magnets requires circulation of liquid helium through the magnet cooling channel. A bellows helium pump is one possible way of providing helium flow to a magnet cooling system. Since the bellows type of helium pump is immersed in liquid helium, a superconducting linear motor drive appears to be an attractive option. This report describes a linear motor drive that employs oriented permanent magnet materials such as samarium-cobalt as the stator magnet system and a superconducting loud speaker voice coil type of drive as the armature of the linear motor. This report examines drive motor requirements for a helium pump.
Date: October 1994
Creator: Green, M. A.
Partner: UNT Libraries Government Documents Department

Purdue University National Biomedical Tracer Facility: Project definition phase. Final report

Description: The proposed National Biomedical Tracer Facility (NBTF) will house a high-current accelerator dedicated to production of short-lived radionuclides for biomedical and scientific research. The NBTF will play a vital role in repairing and maintaining the United States` research infrastructure for generation of essential accelerator-based radioisotopes. If properly designed and managed, the NBTF should also achieve international recognition as a Center-of-Excellence for research on radioisotope production methods and for associated education and training. The current report documents the results of a DOE-funded NBTF Project Definition Phase study carried out to better define the technical feasibility and projected costs of establishing and operating the NBTF. This report provides an overview of recommended Facility Design and Specifications, including Accelerator Design, Building Design, and the associated Construction Cost Estimates and Schedule. It is recommended that the NBTF be established as an integrated, comprehensive facility for meeting the diverse production, research, and educational missions set forth in previous documents. Based on an analysis of the projected production demands that will be placed on the NBTF, it appears that a 70 MeV, 1 mA, negative ion cyclotron will offer a good balance between production capabilities and the costs of accelerator purchase and operation. A preliminary architectural plan is presented for a facility designed specifically to fulfill the functions of the NBTF in a cost-effective manner. This report also presents a detailed analysis of the Required Federal State, and Local Permits that may be needed to establish the NBTF, along with schedules and cost estimates for obtaining these permits. The Handling, Storage, and Disposal of Radioactive Waste will pose some significant challenges in the operation of the NBTF, but at this stage of planning the associated problems do not appear to be prohibitive.
Date: February 15, 1995
Creator: Green, M.A.
Partner: UNT Libraries Government Documents Department

An update on passive correctors for the SSC dipole magnets

Description: The concept of correction of the magnetization sextupole became a topic of discussion as soon as it was realized that superconductor magnetization could have a serious effect on the SSC beam during injection. Several methods of correction were proposed. These included (1) correction with active bore tube windings like those on the HERA machine which correct out magnetization sextupole and the sextupole due to iron saturation, (2) correction with persistent sextupole windings mounted on the bore tube (3) correction using passive superconductor (4) correction using ferromagnetic material, and (5) correction using oriented magnetized materials. This report deals with the use of passive superconductor to correct the magnetization sextupole. Two basic methods are explored in this report: (1) One can correct the magnetization sextupole by changing the diameter of the superconductor filaments in one or more blocks of the SSC dipole. (2) One can correct the magnetization sextupole and decapole by mounting passive superconducting wires on the inside of the SSC dipole coil bore. In addition, an assessment of the contribution of each conductor in the dipole to the magnetization sextupole and decapole is shown. 38 refs, 25 figs., 15 tabs.
Date: May 1, 1991
Creator: Green, M.A.
Partner: UNT Libraries Government Documents Department

Correction of magnetization sextupole and decapole in a 5 centimeter bore SSC dipole using passive superconductor

Description: Higher multipoles due to magnetization of the superconductor in four and five centimeter bore Superconducting Super Collider (SSC) superconducting dipole magnets have been observed. The use of passive superconductor to correct out the magnetization sextupole has been demonstrated on two dipoles built by the Lawrence Berkeley Laboratory (LBL). This reports shows how passive correction can be applied to the five centimeter SSC dipoles to remove sextupole and decapole caused by magnetization of the dipole superconductor. Two passive superconductor corrector options will be presented. The change in magnetization sextupole and decapole due to flux creep decay of the superconductor during injection can be partially compensated for using the passive superconductor. 9 refs; 5 figs.
Date: May 1, 1991
Creator: Green, M.A.
Partner: UNT Libraries Government Documents Department