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Cryogenic studies of rf accelerating structures, vintage 1978

Description: Cryogenically cooled rf cavity studies were undertaken at Los Alamos in 1978 to test the effectiveness of reduced temperature on the Q-enhancement of 450-MHz drift-tube linac structures. A complete facility was set up to do high power tests, not only at liquid nitrogen (LN/sub 2/) temperature but with liquid hydrogen (LH/sub 2/) as well. The cavity, Dewar, klystron test stand, and a remote outdoor enclosure were constructed. Hydrogen safety approval for the tests was obtained. Unfortunately, the hydrogen tests were never done. However, the cavity was tested at high power in LN/sub 2/ and a Q-enhancement of 2.02 was recorded, compared to 2.7 expected theoretically. This work is now continuing with improved measuring techniques using some of the same apparatus. It is the purpose of this paper to report on the early work and to reference its continuation today.
Date: January 1, 1986
Creator: Liska, D.; Uher, J. & Potter, J.
Partner: UNT Libraries Government Documents Department

SSC (Superconducting Super Collider) dipole coil production tooling

Description: Superconducting Super Collider dipole coils must be produced to high precision to ensure uniform prestress and even conductor distribution within the collared coil assembly. Tooling is being prepared at Fermilab for the production of high precision 1M and 16.6M SSC dipole coils suitable for mass production. The design and construction methods builds on the Tevatron tooling and production experience. Details of the design and construction methods and measured coil uniformity of 1M coils will be presented. 4 refs., 10 figs.
Date: March 1, 1989
Creator: Carson, J.A.; Barczak, E.J.; Bossert, R.C.; Brandt, J.S. & Smith, G.A.
Partner: UNT Libraries Government Documents Department

Design considerations and prototype performance of the Fermilab Main Injector dipole

Description: The Main Injector project at Fermilab requires a dipole with good field quality from 0.1 T to 1.73 T with ramps to full field at up to 2.4 T/s over an aperture of 10 {times} 5 cm. Operation of this magnet for the variety of purposes proposed for the Main Injector results in a design with low inductance, large copper cross section, and field uniformity sufficient for high intensity injection and efficient slow resonant extraction. The resulting design is presented, along with measurement results of a prototype magnet emphasizing the field uniformity. 6 refs., 4 figs., 2 tabs.
Date: May 1, 1991
Creator: Harding, D.J.; Bleadon, M.E.; Brown, B.C.; Desavouret, E.; Garvey, J.D.; Glass, H.D. et al.
Partner: UNT Libraries Government Documents Department

Magnets for high energy colliders

Description: The problem of producing, preserving and stably colliding low emittance bunches for long periods of time is a formidable problem involving questions of jitter, dynamic alignment and reproducibility associated with magnetic and mechanically hysteresis. Permanent magnets provide ideal solutions for lower capital and operating costs. Because they are light in weight, compact and require no power or cooling they are easy to use, stable and uniquely reliable. With their low permeability this implies a minimal impact on the surrounding environment and vice versa. For example, they are ideal for final focus systems embedded in particle detectors with strong solenoidal fields while their strength and compactness minimizes the solid angle they subtend around the interaction point (IP) as well as their target thickness along the beam line. We discuss calculations there /rvec B/ is a nonlinear, anisotropic function of /rvec H/. The results explain discrepancies observed measurement and calculation of permanent magnet systems and indicate good multipoles are possible with far higher strengths than previously obtained. We extend previous calculations on the obtainable gradients for different types of quadrupoles down to 1 mm bore radii where 2000 T/m appears possible with conventional designs and available materials. We discuss why much higher gradients are possible by the same means. Additional specifications for PM manufacturers are recommended. 14 refs., 5 figs.
Date: March 1, 1989
Creator: Spencer, J. & Stucki, H.
Partner: UNT Libraries Government Documents Department

Test of two 1. 8 M SSC model magnets iwth iterated design

Description: We report results from two 1.8 m-long dipoles built as part of the Superconducting Super Collider (SSC) RandD program. These magnets contain design changes made on both the 1.8 m and the full-length 17 m dipoles to improve quench performance, magnetic field uniformity, and manufacturability. The magnets reach 8 T with little training. 10 refs., 5 figs., 1 tab.
Date: January 1, 1989
Creator: Wanderer, P.; Cottingham, J.G.; Dahl, P.; Ganetis, G.; Garber, M.; Ghosh, A. et al.
Partner: UNT Libraries Government Documents Department

An alternate method for designing dipole magnet ends

Description: Small bore superconducting dipole magnets, such as those for the SSC, often have problems in the ends. These problems can often be alleviated by spreading out the end windings so that the conductor sees less deformation. This paper presents a new procedure for designing dipole magnet ends which can be applied to magnets with either cylindrical or conical bulged ends to have integrated field multipoles which meet the constraints imposed by the SSC lattice. The method described here permits one to couple existing multiparameter optimization routines (i.e., MINUIT with suitable independent parameter constraints) with a computer code DIPEND, which describes the multiples, so that one can meet any reasonable objective (i.e., minimizing integrated sextupole and decapole). This paper will describe how the computer method was used to analyze the bulged conical ends for an SSC dipole. 6 refs, 6 figs, 2 tabs.
Date: August 1, 1988
Creator: Pope, W.L.; Green, M.A.; Peters, C.; Caspi, S. & Taylor, C.E.
Partner: UNT Libraries Government Documents Department

The location of the quench origin in a superconducting accelerator magnet

Description: A method of calculating the initial rate of rise of the resistive voltage in a quenching superconducting magnet is described. Comparison of such calculations with data from spontaneously occurring quenches gives the location of the quench origin since the normal state resistance of the conductor is determined by its position in the windings due to the magnetoresistance of the copper matrix. The characteristics of the voltage buildup is used to separate quenches occurring in low field regions, such as the magnet ends, from those starting in the two-dimensional straight section of the coil. The magnitude of V dot is a measure of performance and can be used to determine if the magnet is reaching the maximum current permitted by the conductor parameters.
Date: January 1, 1987
Creator: Ghosh, A.K.; Robins, K.E. & Sampson, W.B.
Partner: UNT Libraries Government Documents Department

Mechanical and electromagnetic design of the SSC QSE101 quadrupole ends

Description: The SSC collider magnets feature grouped ends in which cables of a particular coil remain stacked together as they are gent around the end. methods have been developed to form the ends in such a way that mechanical stresses are lowered and field quality is optimized. This paper discusses techniques of end turn design and presents calculations of harmonics and peak fields for the SSC quadrupole QSE101. 5 refs., 9 figs.
Date: June 1, 1991
Creator: Orrell, D.; Nobrega, F.; Lilly, J.; Snitchler, G.; Jayakumar, J.; Venkatraman, V. (Superconducting Super Collider Lab., Dallas, TX (United States)) et al.
Partner: UNT Libraries Government Documents Department

Status of the SUNY superconducting RFQ

Description: A RFQ resonator is presently being developed at SUNY. This resonator is a prototype for a chain of six short ({approximately}0.5m long), superconducting (Pb plated Cu), 50 MHz resonators designed to accelerate beam from {beta} = 0.01 to 0.05. The chain accepts a prebunched beam to save on superconducting length. The resonators are of four-rods type with vane-like electrodes. The prototype resonator is designed to accelerate ions of q/A = 1/6 from {beta} = 0.030 to 0.036, operating at a peak surface electric field of 16 MV/m. The electrodes have a rather high modulation parameter of 4 and a wide aperture of 1.57 cm radius. These values are chosen to maximize the accelerating field (E{sub a}) for a given peak surface electric field (E{sub s}). At the design value of E{sub s} = 16 MV/m, the resonator is estimated to have E{sub a} = 2.0 MV/m, stored energy of 4 J, peak surface magnetic field of 360 Gauss, and inter-vane voltage of 0.42 MV. Results of RF tests on this prototype resonator will be presented. 7 refs., 3 figs.
Date: January 1, 1991
Creator: Jain, A.; Ben-Zvi, I.; Paul, P.; Wang, H. (Brookhaven National Lab., Upton, NY (United States)) & Lombardi, A. (Istituto Nazionale di Fisica Nucleare, Legnaro (Italy). Lab. Nazionale di Legnaro)
Partner: UNT Libraries Government Documents Department

Tests of full scale SSC (Superconducting Super Collider) R and D dipole magnets

Description: Four full-scale SSC R and D dipole magnets, incorporating successive mechanical design improvements, have been quench tested. Three of these magnets are heavily instrumented with sensors to measure the mechanical behavior of the magnets and verify the performance of the mechanical improvements and with multiple voltage taps to locate the origin of quenches. The last two magnets of this series reach the SSC design operating field of 6.6 T in two or fewer quenches. Load cells and motion sensors show that in these two magnets the azimuthal clamping stress is higher at zero current and drops more slowly with excitation than in previous long magnets and that the axial motion of the coil upon excitation has been greatly reduced. Quenches are found to originate preferentially in several locations, suggesting other design improvements. 13 refs., 5 figs.
Date: August 22, 1988
Creator: Strait, J.; Brown, B.C.; Hanft, R.; Kuchnir, M.; Lamm, M.; Lundy, R. et al.
Partner: UNT Libraries Government Documents Department

Test results from recent 1. 8-m SSC (Superconducting Super Collider) model dipoles

Description: We report results from four 1.8 m-long dipoles built as part of the Superconducting Super Collider (SSC) RandD program. Except for length, these models have the features of the SSC design, which is based on a two-layer cosine theta coil with 4 cm aperture. As compared to the 17 m design length SSC dipoles, these 1.8 m magnets are a faster and more economical way of testing design changes in field shape, conductor support in the coil straight-section and ends, etc. The four magnets reported here all reach fields in excess of 7.5T with little training and have excellent field shape. 10 refs., 2 figs., 3 tabs.
Date: January 1, 1988
Creator: Wanderer, P.; Cottingham, J.G.; Dahl, P.; Garber, M.; Ghosh, A.; Goodzeit, C. et al.
Partner: UNT Libraries Government Documents Department

Mechanical support of superconducting coils

Description: Cold iron magnets use the iron yoke and skin for mechanical support of the collared coil assembly. A variety of designs, including horizontally and vertically split yokes, collarless'' magnets and conductor block geometries, have been considered for use with collared coils. This note qualitatively compares the support mechanisms by estimating the amount of coil overcompression'' necessary for the magnet to achieve the same mechanical condition in the cold, powdered state. These designs inspect magnet limitations by suggesting means to reduce the peak coil compressive load, allowing higher central magnetic fields to be reached.
Date: July 1, 1990
Creator: Bossert, R.C. & Kerby, J.S.
Partner: UNT Libraries Government Documents Department

Magnetic field decay in model SSC dipoles

Description: We have observed that some of our model SSC dipoles have long time constant decays of the magnetic field harmonics with amplitudes large enough to result in significant beam loss, if they are not corrected. The magnets were run at constant current at the SSC injection field level of 0.3 tesla for one to three hours and changes in the magnetic field were observed. One explanation for the observed field decay is time dependent superconductor magnetization. Another explanation involves flux creep or flux flow. Data are presented on how the decay changes with previous flux history. Similar magnets with different Nb-Ti filament spacings and matrix materials have different long time field decay. A theoretical model using proximity coupling and flux creep for the observed field decay is discussed. 10 refs., 5 figs., 2 tabs.
Date: August 1, 1988
Creator: Gilbert, W.S.; Althaus, R.F.; Barale, P.J.; Benjegerdes, R.W.; Green, M.A.; Green, M.I. et al.
Partner: UNT Libraries Government Documents Department

Correction of magnetization sextupole in one-meter long dipole magnets using passing superconductor

Description: The generation of higher multipoles due to the magnetization of the superconductor in the dipoles of the SSC is a problem during injection of the beam into the machine. The use of passive superconductor was proposed some years ago to correct the magnetization sextupole in the dipole magnet. This paper presents the LBL test results in which the magnetization sextupole was greatly reduced in two one-meter long dipole magnets by the use of passive superconductor mounted on the magnet bore tube. The magnetization sextupole was reduced a factor of five on one magnet and a factor of eight on the other magnet using this technique. Magnetization decapole was also reduced by the passive superconductor. The passive superconductor method of correction also reduced the temperature dependence of the magnetization multipoles. In addition, the drift in the magnetization sextupole due to flux creep was also reduced. Passive superconductor correction appears to be a promising method of correcting out the effects of superconductor magnetization in SSC dipoles and quadrupoles. 10 refs., 6 figs.
Date: March 1, 1990
Creator: Green, M.A.; Althaus, R.F.; Barale, P.J.; Benjegerdes, R.W.; Gilbert, W.S.; Green, M.I. et al.
Partner: UNT Libraries Government Documents Department

Superconducting synchrotron power supply and quench protection scheme. [Fermilab 6 km circumference]

Description: The power supply and quench protection scheme for the proposed Fermilab 6 km circumference superconducting synchrotron is described. Specifically, the following points are discussed: (1) the 46 MW thyristor power supply; (2) the 3 x 10/sup 8/ J emergency energy dump; (3) the distributed microprocessing system for the detection of quenches; (4) the thyristor network for shunting current around quenched magnets; and (5) the heaters internal to the magnets which cause rapid propagation of quenches. Test results on prototype systems are given.
Date: January 1, 1978
Creator: Stiening, R.; Flora, R.; Lauckner, R. & Tool, G.
Partner: UNT Libraries Government Documents Department

Electrical characteristics of a short RFQ resonator

Description: Electrical characteristics of a short RFQ resonator of the four rod'' type have been studied by carrying out measurements on models and numerical simulations using the MAFIA codes. An empirical formula is obtained for the capacitance of vane-like electrodes in a four-rod RFQ resonator. It is shown that the electrode supports could account for a significant part of the total capacitance. This additional capacitance may change the circuit symmetry and give rise to a dipole component. This effect can be compensated by appropriate modifications of the support structure. The beam offset due to a dipole component is estimated. 6 refs., 4 figs., 1 tab.
Date: January 1, 1990
Creator: Ben-Zvi, I.; Jain, A.; Wang, H. (State Univ. of New York, Stony Brook, NY (USA). Dept. of Physics) & Lombardi, A. (Istituto Nazionale di Fisica Nucleare, Legnaro (Italy). Lab. Nazionale di Legnaro)
Partner: UNT Libraries Government Documents Department

A high gradient quadrupole magnet for the SSC (Superconducting Super Collider)

Description: A quadrupole magnet for the SSC has been designed with a gradient of 234 T/m at 6500 A. Coil ID is 40 mm. The two-layer windings have 9 inner turns and 13 outer turns per pole with a wedge-shaped spacer in each layer. The 30-strand cable is identical to that used in the outer layer of the SSC dipole magnet. Interlocking aluminum alloy collars are compressed around the coils using a four-way press and are locked with four keys. The collared coil is supported and centered in a cold split iron yoke. A one-meter model was constructed and tested. Design details including quench behavior are presented.
Date: March 1, 1987
Creator: Taylor, C.; Caspi, S.; Helm, M.; Mirk, K.; Peters, C. & Wandesforde, A.
Partner: UNT Libraries Government Documents Department

Offset coil designs for superconducting magnets, a logical development

Description: Dipoles and quadrupoles for any new, large proton ring must be stronger, smaller and have better field shape (systematic error) than those used in the Doubler. The present two-shell designs are rigid in that the coils are too thin but cannot be relatively fatter without destroying the field quality. An examination of the coil shapes for dipoles and quadrupoles which produce perfect fields from a uniform current density shows clearly that our persistent use of a circular form for the inner surface of the coils is a poor approximation. When this is corrected by ''offsets'' there is a striking improvement both in the strength of fields and in the field quality. The same analysis makes clear that the efficient use of superconductor and the overall magnet size is determined by the perfect coil shapes. Any reasonable magnet will not differ significantly from the ideal for these parameters. This will be particularly helpful in setting design goals for very large quadrupoles. The offset two-shell dipole design preserves the mechanical features of the highly successful, resilient doubler magnets while greatly extending the performance.
Date: March 1, 1986
Creator: Collins, T.
Partner: UNT Libraries Government Documents Department

Mechanical design and analysis of the 2D cross-section of the SSC collider dipole magnet

Description: The 50 mm aperture collider dipole magnet uses stainless steel collars to position the conductors at the locations specified by the magnetic design and to prestress the coil to prevent conductor motion under excitation. The collars are supported by the vertically-split yoke and cold mass skin to reduce their deflection under excitation. The collar interior is designed to give the coil its required shape at the operating temperature taking into account all deflections that occur from assembly and cooldown. 13 refs., 2 figs., 1 tab.
Date: May 1, 1991
Creator: Strait, J.; Kerby, J.; Bossert, R.; Carson, J. (Fermi National Accelerator Lab., Batavia, IL (USA)); Spigo, G. & Turner, J.R. (Superconducting Super Collider Lab., Dallas, TX (USA))
Partner: UNT Libraries Government Documents Department

Mechanical design and analysis of the 2D cross-section of the SSC collider dipole magnet

Description: This paper describes the mechanical design of the two dimensional cross-section of the base-line collider dipole magnet for the Superconducting Super Collider. The components described here are the collar laminations, the tapered keys that lock the upper and lower collars, the yoke laminations, the cold mass shell. We describe in detail the shape of the outer surface of the collars which defines the yoke-collar interface, and the shape of the collar interior, which defines the conductor placement. Other features of the collar and yoke will be described in somewhat less detail. 20 refs., 12 figs. , 6 tabs.
Date: May 1, 1991
Creator: Strait, J.; Kerby, J.; Bossert, R. & Carson, J.
Partner: UNT Libraries Government Documents Department

SSC collider dipole magnet end mechanical design

Description: This paper describes the mechanical design of the ends of Superconducting Super Collider dipole magnets to be constructed and tested at Fermilab. Coil end clamps, end yoke configuration, and end plate design are discussed. Loading of the end plate by axial Lorentz forces is discussed. Relevant data from 40 mm and 50 mm aperture model dipole magnets built and tested at Fermilab are presented. In particular, the apparent influence of end clamp design on the quench behavior of model SSC dipoles is described. 8 refs., 3 figs.
Date: May 1, 1991
Creator: Delchamps, S.W.; Bossert, R.C.; Carson, J.; Ewald, K.; Fulton, H.; Kerby, J. et al.
Partner: UNT Libraries Government Documents Department

SSC dipole vacuum vessel support placement analysis

Description: Early (superconducting super collider) SSC dipole model magnets were supported at five points along their length by feet welded to the vacuum vessel. The cold mass was supported at the same five points. The number of supports was determined such that the maximum cold mass deflection between supports was limited to 0.010 inches as specified in the first version of the SSC Design Criteria. The spacing between supports was determined to minimize the sag of the cold mass, given five supports. This paper analyzes the deflection of the cold mass and vacuum vessel as a result of these supports. 4 refs. (LSP)
Date: August 1, 1987
Creator: Nicol, T.H.
Partner: UNT Libraries Government Documents Department