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Magnetic field strength and shape measurements of the Fermilab main injector quadrupoles

Description: All of the new quadrupoles for the Fermilab Main Injector ring have been built and measured. The magnets are 2.95 m and 2.54 m in length with a 41.7 mm bore. In operation, the magnets run from 1.61 T/m at 8. 9 GeV/c to 15.7 T/m at 120 GeV/c and 19.6 T/m at 150 GeV/c. These points correspond to injection, Main Injector fixed target physics and antiproton production, and extraction for transfer to the Tevatron. Good field uniformity is required to ensure a stable beam over the whole acceleration cycle. A significant octupole is included to assist in resonant extraction. The performance of these quadrupoles, in both integrated strength and field uniformity, is presented. All magnets produced meet the accelerator requirements.
Date: May 1, 1997
Creator: Harding, D.J.; Brown, B.C. & DiMarco, H.H.
Partner: UNT Libraries Government Documents Department

Magnetic reconnection in space plasmas

Description: This is the final report of a three-year, Laboratory-Directed Research and Development (LDRD) project at the Los Alamos National Laboratory (LANL). Magnetic reconnection produces fundamental changes in the magnetic field topology of plasmas and leads ultimately to substantial plasma heating and acceleration. The transfer of stored magnetic field energy to the plasma occurs primarily at thin conversion layers that extend outward from the reconnection site. We performed a comparative study of the structure and nature of these conversion layers as observed during reconnection at Earth`s magnetopause and in the geomagnetic tail. Our research utilized plasma and magnetic field data from the Earth-orbiting ISEE satellites during crossings of the conversion layers at the magnetopause and in the geomagnetic tail, as well as data obtained during a long-duration balloon flight in Antarctica and simultaneously from satellites in geosynchronous orbit. We have found that the reconnection layer at the magnetopause usually does not contain a slow mode shock, contrary to earlier theoretical expectations. Through a coordinated analysis of data obtained from balloon altitudes and at geosynchronous orbit, we obtained evidence that reconnection can occur simultaneously in both hemispheres at the magnetopause above the polar caps. The final year of our study was oriented primarily towards the question of determining the magnetic topology of disturbances in the solar wind associated with coronal mass ejections (CMEs) and understanding how that topology is affected by magnetic reconnection occurring near the Sun.
Date: April 1, 1996
Creator: Gosling, J.; Feldman, W. & Walthour, D.
Partner: UNT Libraries Government Documents Department

D-zero rototrack: first stage of D-zero 2 Tesla solenoid field mapping device

Description: A simple and portable field mapping device was developed at Fermilab and successfully used to test the D0 2 Tesla solenoid at Toshiba Works in Japan. A description of the mechanical structure, electric driving and control system, and software of the field mapping device is given. Four Hall probe elements of Group3 Digital Gaussmeters are mounted on the radial extension arm of a carriage, which is mounted on a central rotating beam. The system gives two dimensional motions (axial and rotational) to the Hall probes. To make the system compact and portable, we used a laptop computer with PCMCIA cards. For the control system we used commercially available software LabVIEW and Motion Toolbox, and for the data analysis we used Microsoft Excel.
Date: September 1, 1997
Creator: Yamada, R.; Korienek, J.; Krider, J.; Lindenmeyer, C.; Miksa, D. & Miksa, R.
Partner: UNT Libraries Government Documents Department

Alternative poloidal field configurations for ITER

Description: The US Home Team has investigated the physics and engineering issues for two alternate poloidal field coil configurations for ITER. The first is called the Segmented CS configuration, where all of the solenoid modules are pancake-wound. The second option, termed the Hybrid CS configuration, utilizes a layer-wound central module and pancake-wound end modules. Performance comparisons are presented for the baseline design and the two alternate PF configurations, characterizing the 21 MA reference scenario. Alternate operating modes such as reverse-shear operation and a 17 MA driven mode were evaluated, but are not reported here.
Date: September 2, 1997
Creator: Bulmer, R.H. & Neilson, G.H.
Partner: UNT Libraries Government Documents Department

Cusp and Y-type magnetic structures and volocity fields at the endpoint of the reconnection layer

Description: We study the two-dimensional global scale magnetic field structure for a system of two merging cylindrical plasmas in a steady state. In the limit of very large magnetic Reynolds numbers the reconnection process is slow, and the plasma almost everywhere finds itself in magnetostatic equilibrium. We show that under certain conditions the classical Syrovatskii-type Y-point configuration, with surface current concentrated only in the reconnection layer, is not possible. Instead, a cusp configuration is formed, with finite surface current in the separatrix. The equilibrium condition, together with constraints on the volume per flux, enables us to determine the shape of the separatrix and the magnetic field in the vicinity of the cusp point. Our solution is characterized by a singular power law dependence of current density on the flux coordinate ({psi}) near the separatrix: j({Psi}) {approx} |{Psi}|{sup -1/2}. This solution gives us the boundary conditions that are needed to find the flow in the reconnection and the separatrix regions.
Date: June 12, 1997
Creator: Uzdensky, D.A. & Kulsrud, R.M.
Partner: UNT Libraries Government Documents Department

Recent Advances in the Design of Quasi-axisymmetric Stellarator Plasma Configurations

Description: Strategies for the improvement of quasi-axisymmetric stellarator configurations are explored. Calculations of equilibrium flux surfaces for candidate configurations are also presented. One optimization strategy is found to generate configurations with improved neoclassical confinement, simpler coils with lower current density, and improved flux surface quality relative to previous designs. The flux surface calculations find significant differences in the extent of islands and stochastic regions between candidate configurations. (These calculations do not incorporate the predicted beneficial effects of perturbed bootstrap currents.) A method is demonstrated for removing low-order islands from candidate configurations by relatively small modifications of the configuration. One configuration is identified as having particularly desirable properties for a proposed experiment.
Date: January 30, 2001
Creator: Reiman, A.; Ku, L.; Monticello, D.; Hirschman, S.; Hudson, S. & Kessel, C.
Partner: UNT Libraries Government Documents Department

Hybrid permanent magnet quadrupoles for the Recycler Ring at Fermilab

Description: Hybrid Permanent Magnet Quadrupoles are used in several applications for the Fermilab Recycler Ring and associated beam transfer lines. Most of these magnets use a 0.6096 m long iron shell and provide integrated gradients up to 1.4 T-m/m with an iron pole tip radius of 41.6 mm. A 58.4 mm pole radius design is also required. Bricks of 25. 4 mm thick strontium ferrite supply the flux to the back of the pole to produce the desired gradients (0.6 to 2.75 T/m). For temperature compensation, Ni-Fe alloy strips are interspersed between ferrite bricks to subtract flux in a temperature dependent fashion. Adjustments of the permeance of each pole using iron between the pole and the flux return shell permits the matching of pole potentials. Magnetic potentials of the poles are adjusted to the desired value to achieve the prescribed strength and field uniformity based on rotating coil harmonic measurements. Procurement, fabrication, pole potential adjustment, and measured fields will be reported.
Date: October 1, 1997
Creator: Brown, B.C.; Pruss, S.M.; Foster, G.W.; Glass, H.D.; Harding, D.J.; Jackson, G.R. et al.
Partner: UNT Libraries Government Documents Department

Hybrid permanent magnet gradient dipoles for the recycler ring at Fermilab

Description: Hybrid permanent magnets provide the magnetic fields for an anti- proton storage ring which is under construction at Fermilab. Using a combined function lattice, gradient magnets provide the bending, focusing and sextupole correction for the regular cells. Shorter magnets without sextupole are used in dispersion suppressor cells. These magnets use a 4.7 m ( 3 m) long iron shell for flux return, bricks of 25.4 mm thick strontium ferrite supply the flux and transversely tapered iron poles separated by aluminum spacers set the shape of the magnetic field. Central fields of 0.14 T with gradients of {approx}6%/inch ({approx}13%/inch) are required. Field errors are expected to be less than 10{sup -4} of the bend field over an aperture of {+-}40 mm (horizontal) {times} {+-}20 mm (vertical). Design, procurement, fabrication, pole potential adjustment, field shape trimming and measured fields will be reported.
Date: November 1, 1997
Creator: Brown, B.C.; Dimarco, J.; Foster, G.W.; Glass, H.D.; Haggard, J.E.; Harding, D.J. et al.
Partner: UNT Libraries Government Documents Department

Design and alaysis of the PEP-II B-Factory HER QF5 quadrupole magnet

Description: The High Energy Ring (HER) in Stanford Linear Accelerator Center`s PEP-II B-Factory employs two high field quality quadrupole magnets, labeled QF5, located in the Interaction Region (IR) symmetrically about the Interaction Point (IP), for final horizontal beam focusing. An asymmetric, septum, Collins quadrupole design is required for QF5 as a result of space constraints within the IR. Water cooled square hollow copper conductor is used in a two coil per pole configuration to develop the 61.7 kG/m and 82.2 kG/m gradients required for the HER 9 GeV and 12 GeV energy levels respectively. A 1.45 m long laminated iron core constructed in two halves with a 160 mm diameter aperture and pole tip shims shape the quadruple field. The QF5 field quality requirements include a multipole content of b{sub n}/b{sub 2} {le}1 {times} 10{sup -4} for n = 3-15 at a radius of 78.1 mm. The QF5 quadrupole mechanical and magnetic design and analysis are presented.
Date: October 11, 1997
Creator: Kendall, C.M.; Harvey, A.; Swan, J.; Yamamoto, R.; Yokota, T.; Tanabe, J. et al.
Partner: UNT Libraries Government Documents Department

Magnetic topologies of coronal mass ejection events: Effects of 3-dimensional reconnection

Description: New magnetic loops formed in the corona following coronal mass ejection, CME, liftoffs provide strong evidence that magnetic reconnection commonly occurs within the magnetic ``legs`` of the departing CMEs. Such reconnection is inherently 3-dimensional and naturally produces CMEs having magnetic flux rope topologies. Sustained reconnection behind CMEs can produce a mixture of open and disconnected field lines threading the CMES. In contrast to the results of 2-dimensional reconnection. the disconnected field lines are attached to the outer heliosphere at both ends. A variety of solar and solar wind observations are consistent with the concept of sustained 3-dimensional reconnection within the magnetic legs of CMEs close to the Sun.
Date: September 1, 1995
Creator: Gosling, J.T.
Partner: UNT Libraries Government Documents Department

Magnetic field components in a sinusoidally varying helical wiggler

Description: One may be interested in a pure multipole magnetic field (i.e., proportional to sin(n{theta}) or cos(n{theta}) whose strength varies purely as a Fourier sinusoidal series of the longitudinal coordinate z (say proportional to cos{sub L}/{sup (2m-1){pi}z}), where L denotes the half-period of the wiggler and m=1,2,3{hor_ellipsis}). Associated with such a z variation, there necessarily will be presented a z component of magnetic field which in the source-free region, in fact, will give rise to both normal and skew transverse fields associated with the functions A{sub n}(z) and {Angstrom}{sub n}(z) as expressed in Reference{sup bc}. In this note the field components and expression for the scalar potential both inside and outside a thin pure winding surface are included with additional contributions from a possible high permeable shield. It is also shown that for a pure dipole case of n=1 and pure axial variation of m=1 the transverse field can be derived from a simple two dimensional field.
Date: July 27, 1994
Creator: Caspi, S.
Partner: UNT Libraries Government Documents Department

Dynamo and anomalous transport in the reversed field pinch

Description: The reversed field pinch is an effective tool to study the macroscopic consequences of magnetic fluctuations, such as the dynamo effect and anomalous transport. Several explanations exist for the dynamo (the self-generation of plasma current)--the MHD dynamo, the kinetic dynamo, and the diamagnetic dynamo. There is some experimental evidence for each, particularly from measurements of ion velocity and electron pressure fluctuations. Magnetic fluctuations are known to produce energy and particle flux in the RFP core. Current profile control is able to decrease fluctuation-induced transport by a factor of five. Improved confinement regimes are also obtained at deep reversal and, possibly, with flow shear.
Date: August 1, 1998
Creator: Prager, S. C.
Partner: UNT Libraries Government Documents Department

Measurement of core velocity fluctuations and the dynamo in a reversed-field pinch

Description: Plasma flow velocity fluctuations have been directly measured in the high temperature magnetically confined plasma in the Madison Symmetric Torus (MST) Reversed-Field Pinch (RFP). These measurements show that the flow velocity fluctuations are correlated with magnetic field fluctuations. This initial measurement is subject to limitations of spatial localization and other uncertainties, but is evidence for sustainment of the RFP magnetic field configuration by the magnetohydrodynamic (MHD) dynamo. Both the flow velocity and magnetic field fluctuations are the result of global resistive MHD modes of helicity m = 1, n = 5--10 in the core of MST. Chord-averaged flow velocity fluctuations are measured in the core of MST by recording the Doppler shift of impurity line emission with a specialized high resolution and throughput grating spectrometer. Magnetic field fluctuations are recorded with a large array of small edge pickup coils, which allows spectral decomposition into discrete modes and subsequent correlation with the velocity fluctuation data.
Date: December 31, 1998
Creator: Den Hartog, D. J.; Craig, D.; Fiksel, G.; Fontana, P. W.; Prager, S. C.; Sarff, J. S. et al.
Partner: UNT Libraries Government Documents Department

Results on Fermilab main injector dipole measurements

Description: Measurements of the Productions run of Fermilab Main Injector Dipole magnets is underway. Redundant strength measurements provide a set of data which one can fit to mechanical and magnetic properties of the assembly. Plots of the field contribution from the steel supplement the usual plots of transfer function (B/I) vs. I in providing insight into the measured results.
Date: June 1, 1995
Creator: Brown, B.C.; Baiod, R.; DiMarco, J.; Glass, H.D.; Harding, D.J.; Martin, P.S. et al.
Partner: UNT Libraries Government Documents Department

Field shape of the accumulator LDA dipoles

Description: Large Aperture Dipoles (LDA) are used in the Fermilab Antiproton Accumulator to provide one half of the bending required for that storage ring. The production measurement data for those magnets are analyzed and the integrated field shape on the median plane at the design operating current (1,180 A) is reported. When linear (quadrupole) and parabolic (sextupole) terms are subtracted, the remaining field errors are only {approximately}10{sup {minus}4} over a {+-}4 inch aperture. Polynomial fits to that data can be interpreted in terms of normal harmonics of the magnetic field. However the polynomial fits are not unique. When the polynomial coefficients are expressed as harmonics with a reference radius of 1 inch, the nonlinear portions of this field (harmonics higher than quadrupole) are typically 10{sup {minus}5} to 10{sup {minus}6}. Both individual magnet results and statistical profiles are reported along with studies of the fitting limitations.
Date: May 1, 1996
Creator: Brown, B.C.
Partner: UNT Libraries Government Documents Department

Low alpha experiments at the ALS

Description: The authors present a modified, low alpha lattice for the Advanced Light Source where the quadrupole field strengths have been detuned to allow the momentum compaction factor to be varied smoothly from positive to negative values. With this low alpha lattice the authors decrease the momentum compaction factor by a factor of 5 to 0.0003 over normal operation resulting in a measured bunch length reduction of 2. They also measure the size the second order momentum compaction factor as well as store beam in a negative momentum compaction lattice. Streak camera measurements at positive and negative momentum compaction operation show longitudinal beam profile distributions that are in agreement with simulations by Fang et al.
Date: August 1, 1995
Creator: Robin, D.; Alvis, R.; Jackson, A.; Holtzapple, R. & Podobedov, B.
Partner: UNT Libraries Government Documents Department

Plasma diagnostic reflectometry

Description: Theoretical and experimental studies of plasma diagnostic reflectometry have been undertaken as a collaborative research project between the Lawrence Livermore National Laboratory (LLNL) and the University of California Department of Applied Science Plasma Diagnostics Group under the auspices of the Laboratory Directed Research and Development Program at LLNL. Theoretical analyses have explored the basic principles of reflectometry to understand its limitations, to address specific gaps in the understanding of reflectometry measurements in laboratory experiments, and to explore extensions of reflectometry such as ultra-short-pulse reflectometry. The theory has supported basic laboratory reflectometry experiments where reflectometry measurements can be corroborated by independent diagnostic measurements.
Date: February 26, 1996
Creator: Cohen, B.I.; Afeyan, B.B.; Garrison, J.C.; Kaiser, T.B.; Luhmann, N.C. Jr.; Domier, C.W. et al.
Partner: UNT Libraries Government Documents Department

Effects of orbit squeezing on ion transport processes close to magnetic axis

Description: It is shown that ion thermal conductivity close to the magnetic axis in tokamaks is reduced by a factor of {vert_bar}S{vert_bar}{sup 5/3} if (M{sub i}/M{sub e}){sup 2/3}(T{sub e}/T{sub i}){sup 4/3}/{vert_bar}S{vert_bar}{sup 5/3} {much_gt} 1. Here, S is the orbit squeezing factor, M{sub i}(M{sub e}) is the ion (electron) mass, and T{sub i}(Te{sub e}) is the ion (electron) temperature. The reduction reflects both the increase of the fraction of trapped particles by a factor of {vert_bar}S{vert_bar}{sup 1/3}, and the decrease of the orbit size in units of the poloidal flux {psi} by a factor of {vert_bar}S{vert_bar}{sup 2/3}.
Date: January 1997
Creator: Shaing, K. C.; Hazeltine, R. D. & Zarnstorff, M. C.
Partner: UNT Libraries Government Documents Department

Study of driven magnetic reconnection in a laboratory plasma

Description: The Magnetic Reconnection Experiment (MRX) has been constructed to investigate the fundamental physics of magnetic reconnection in a well controlled laboratory setting. This device creates an environment satisfying the criteria for a magnetohydrodynamic (MHD) plasma (S {much_gt} 1, {rho}{sub i} {much_lt} L). The boundary conditions can be controlled externally, and experiments with fully three-dimensional reconnection are now possible. In the initial experiments, the effects of the third vector component of reconnecting fields have been studied. Two distinctively different shapes of neutral sheet current layers, depending on the third component, are identified during driven magnetic reconnection. Without the third component (anti-parallel or null-helicity reconnection), a thin double-Y shaped diffusion region is identified. A neutral sheet current profile is measured accurately to be as narrow as order ion gyro-radius. In the presence of an appreciable third component (co-helicity reconnection), an O-shaped diffusion region appears and grows into a spheromak configuration.
Date: December 31, 1998
Creator: Yamada, Masaaki; Ji, H.; Hsu, S.; Carter, T.; Kulsrud, R.; Bretz, N. et al.
Partner: UNT Libraries Government Documents Department

Measuring the magnetic connectivity of the geosynchronous region of the magnetosphere

Description: This is the final report of a three-year, Laboratory-Directed Research and Development (LDRD) project at the Los Alamos National Laboratory (LANL). The purpose of this project was to determine the magnetic connectivity of the geosynchronous region of the magnetosphere to the auroral zone in the polar ionosphere in order to test and refine current magnetospheric magnetic field models. The authors used plasma data from LANL instruments on three geosynchronous satellites and from USAF instruments on three low-altitude, polar-orbiting, DMSP satellites. Magnetic connectivity is tested by comparing plasma energy spectra at DMSP and geosynchronous satellites when they are in near conjunction. The times of closest conjugacy are used to evaluate the field models. They developed the tools for each step of the process and applied them to the study of a one-week test set of conjunctions. They automated the analysis tools and applied them to four months of two-satellite observations. This produced a database of about 130 definitive magnetic conjunctions. They compared this database with the predictions of the widely-used Tsyganenko magnetic field model and showed that in most cases one of the various parameterizations of the model could reproduce the observed field line connection. Further, they explored various measurables (e.g., magnetospheric activity indices or the geosynchronous field orientation) that might point to the appropriate parameterization of the model for these conjunctions, and ultimately, for arbitrary times.
Date: March 1, 1996
Creator: Thomsen, M.; Hones, E.; McComas, D.; Reeves, G. & Weiss, L.
Partner: UNT Libraries Government Documents Department

Effects of particle exhaust on neutral compression ratios in DIII-D

Description: In this paper, neutral particles in DIII-D are studied via their compression in the plenum and via particle exhaust. The compression of gas in the plena is examined in terms of the magnetic field configuration and wall conditions. DIII-D compression ratios are observed in the range from 1 to {ge} 1,000. Particle control ultimately depends on the exhaust of neutrals via plenum or wall pumping. Wall pumping or outgassing is calculated by means of a detailed particle balance throughout individual discharges, and its effect on particle control is discussed. It is demonstrated that particle control through wall conditioning leads to lower normalized densities. A two-region model shows that the gas compression ratio (C{sub div} = divertor plenum neutral pressure/torus neutral pressure) can be interpreted in relation to gas flows in the torus and divertor including the pumping speed of the plenum cryopumps, plasma pumping, and the pumping or outgassing of the walls.
Date: August 1, 1998
Creator: Colchin, R. J.; Maingi, R.; Wade, M. R.; Allen, S. L. & Greenfield, C. M.
Partner: UNT Libraries Government Documents Department

A study of the plasma properties under an LID configuration in the CHS

Description: An experimental study of the local island divertor (LID) was done in the Compact Helical System (CHS). The separatrix of an m/n = 1/1 magnetic island, formed at the edge region by additional magnetic field was utilized as a divertor configuration. The main purpose of this configuration is to control the neutral particle recycling. The reduced line averaged density and radiation power loss, and improved energy confinement were obtained under an LID configuration.
Date: December 1, 1997
Creator: Masuzaki, Suguru; Komori, Akio & Morisaki, Tomohiro
Partner: UNT Libraries Government Documents Department

Edge plasma control using an LID configuration on CHS

Description: A Local Island Divertor (LID) has been proposed to enhance energy confinement through neutral particle control. For the case of the Large Helical Device (LHD), the separatrix of an m/n = 1/1 magnetic island, formed at the edge region, will be utilized as a divertor configuration. The divertor head is inserted in the island, and the island separatrix provides connection between the edge plasma region surrounding the core plasma and the back plate of the divertor head through the field lines. The particle flux and associated heat flux from the core plasma strike the back plate of the divertor head, and thus particle recycling is localized in this region. A pumping duct covers the divertor head to form a closed divertor system for efficient particle exhaust. The advantages of the LID are ease of hydrogen pumping because of the localized particle recycling and avoidance of the high heat load that would be localized on the leading edge of the divertor head. With efficient pumping, the neutral pressure in the edge plasma region will be reduced, and hence the edge plasma temperature will be higher, hopefully leading to a better core confinement region. A LID configuration experiment was done on the Compact Helical System (CHS) to confirm the effect of the LID. The typical effects of the LID configuration on the core plasma are reduction of the line averaged density to a half, and small or no reduction of the stored energy. In this contribution, the experimental results which were obtained in edge plasma control experiments with the LID configuration in the CHS are presented.
Date: July 1, 1997
Creator: Masuzaki, S.; Komori, A. & Morisaki, T.
Partner: UNT Libraries Government Documents Department