Superconducting Super Collider Research Articles

QCD corrections to Higgs-boson production at proton-proton colliders.

Gluon fusion is the main production mechanism for Higgs bosons with masses up to several hundred GeV in pp collisions at the CERN large Hadron Collider and Superconducting Super Collider. We present the QCD corrections to the fusion cross section for arbitrary Higgs boson and top quark mass values: gg → H(g), gq → Hq, and qq → Hg. The QCD corrections are positive and they increase the cross section σ (pp→H) by about a factor of 1.5 to 1.7. The analysis applies to the production of Higgs particles in the standard model and also to the production of the CP-even Higgs particles in extensions of the Higgs sectors are required, for example, by supersymmetric theories

SSC-VQP-status of the manufacture at AISA of SSC outer wire and cable

Single stacking billets were processed to manufacture Superconducting Super Collider (SSC) outer wire and cable as part of the SSC vendor qualification program. The authors report the production results and the main performance parameters of the wire manufactured. Phase IA and Phase IB results are discussed. Phase IA of this program related to manufacturing 15 different versions of SSC outer wire to investigate the effects of design and process parameters, e.g., NbTi source, billet design, Nb thickness, etc., on the wire critical current density and piece length as well as on the production yield. With regard to phase IB, 23 multifilament billets were processed to produce SSC outer cable with the Alsthom Intermagnetics SA (AISA) baseline design and process. >

Results of AC loss measurements on heat treated SSC cables

Dipole magnets designed for the Superconducting Super Collider (SSC) have shown anomalous ramp rate dependence, and it is thought that interstrand coupling may contribute to this effect. The authors describe measurements made on cable samples which were prepared and measured under circumstances which approximate those which an actual magnet conductor will experience. The object of this experiment was to investigate the sensitivity of eddy current loss to applied pressure, and to observe the loss in a sample prepared under conditions which actual SSC conductors experience during magnet fabrication. Subjecting the cable to pressure during heat treatment and during measurement significantly increased the eddy current loss, but it is not altogether clear that the increase results primarily from interstrand coupling. >

Physics goals of the superconducting supercollider (SSC)

Abstract In the 1980s a strong consensus emerged that the physical goals of the Superconducting SuperCollider (SSC) were clear enough to justify making it the highest priority scientifically of the US particle physics community. That these goals could be achieved followed from the research of a number of people, and in turn was founded on the success of the Standard Model of particle physics. This article reviews these goals, including the impact of recent new data, ideas and calculations. At every stage, results from the Snowmass workshops (each 3 weeks long, with several hundred participants, in 1982, 1984, 1986, 1988 and 1990) have greatly clarified our understanding. Because of the validity of the Standard Model, we know that some fundamental new results will be obtained at the SSC even though we do not know what form those results will take.

Yoke magnetic analysis for the SSC collider quadrupole magnet (CQM)

The authors investigate some options that can improve the design and performance of the Superconducting Super Collider (SSC) collider quadrupole magnet (CQM). They concentrate on the effect of the CQM magnetic material (yoke) on the design. Among these options are reduction of the amount of iron used; transfer function improvement to match that of the collider dipole magnets (CDM); yoke hysteresis effects; and shaping yoke or inserted magnetic material in the CQM collar to correct for some multipoles. PE2D software and FORTRAN codes were used to conduct the analysis. >

Critical current properties of fine filament superconducting wires for the SSC

Nb-Ti superconducting wires with high performance were developed and manufactured at the Furukawa Electric Co., Ltd. under the Superconducting Super Collider (SSC) vendor qualification program. The authors report the result of the experiment intended to enhance the superconductivity performance. This experiment was intended specifically to examine the effects of the heat treatment schedule on the critical current density (J/sub c/), effects of production conditions, other than heat treatment conditions, as represented by extrusion of monofilament and multifilament billets, and the difference in NbTi sources and difference in the thickness of the Nb barrier used as a diffusion preventive material while using mass-produced superconducting wire. The correlation between J/sub c/ and the resultant wire drawing performance is summarized. >

The evolution of tooling, techniques, and quality control for accelerator dipole magnet cables

The author summarize the results of the Superconducting Super Collider (SSC) R&D program from 1984 to 1990. The SSC R&D program has led to a significant improvement in critical current, piece lengths, and overall manufacturing capability for multifilamentary NbTi superconductors. The requirements for current density, filament size, dimensional control, long lengths, and low current degradation are much more stringent for the present accelerators compared with the earlier Tevatron and HERA accelerators. Also, to achieve higher field strengths with efficient use of the superconductor, the new designs require wider cables with more strands. These requirements have stimulated an active research effort which has led to significant improvements in critical current density and conductor manufacturing. In addition, they have stimulated the development of new cabling techniques, improved tooling, and better measurement techniques. The need to produce over 20 million meters of cable has led to the development of high speed cabling machines and online quality assurance measurements. These new developments are discussed, and areas still requiring improvement are identified. >

Quadrupole magnets for the SSC

The authors have designed, constructed, and tested four short (1-m) models and six full-size (5-m) models of the Superconducting Super Collider (SSC) main-ring 5-m focusing quadrupole magnet (211 T/m). The results of this program are summarized. The magnet construction, test procedures, and test results are discussed. Except for modest training above the SSC operating point, the magnets performed very well and proved to be self-protecting. Some design flaws, e.g., inadequate end-clamping and pole shimming, were identified and corrected sufficiently so that the later magnets exceeded specifications.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Results of SSC vendor qualification program at Outokumpu superconductors

Outokumpu Superconductors is engaged as one of the suppliers in the developing of Superconducting Super Collider (SSC) dipole outer cable in the vendor qualification program. In the program, the authors used a billet size of 278 mm in the outer diameter. In phase IB, 15 billets were extruded and drawn down to the final diameter. The phase IA goal was to optimize some production process parameters. In this phase, 18 billets were processed. The wires for the phases IA and IB have been finished, and a summary of the results of phase IB is presented, focusing on the uniformity of quality. Some results of the different optimizing programs of phase IA are presented. >

Magnetic performance of the SSC dipole magnets

The authors report on the status of the magnetic design of the Superconducting Super Collider (SSC) dipole magnets. A two- and three-dimensional design optimization was performed that included the effects of permeable collar, yoke, cryostat, beam tube, crescent yoke end pieces, cool-down, and Lorentz loads. A field quality plan was developed that represents the approach to tuning the design for satisfying the systematic and RMS multipole specifications. The VSA tool is being used to simulate the effects of random parts, tool and process variations on the expected multipole distributions, both between many magnets, and within a single magnet. >

A 50 mm bore superconducting dipole with a unique iron yoke structure

A 50-mm-bore superconducting dipole with a thin stainless steel collar and a close-in elliptical iron yoke was designed to obtain a high transfer function and low saturation effects on the multipoles. A 1-m model was built and tested. The training behavior of the first 1-m model is presented at 4.3 K and 1.8 K. At 1.8 K it reached the record field of 10.06 T. The two layer cos theta winding uses 30 and 36 strand cables identical to the cables of the 50-mm-bore Superconducting Super Collider (SSC) dipole, and it has an operating field of 6.6 T at 4.35 K with a current of 5800 A. To evaluate behavior at high fields, the mechanical structure for the model was designed for 10 T. The thin collar itself provides only a minimum prestress of 10 MPa, and the full prestress of 70 MPa is given by the iron yoke. An aluminum spacer is used to control the gap size in the vertically split iron yoke. The tapered gap in the yoke is determined by the size of the Al spacer so that during cooldown there is no loss of coil prestress and the gap remains closed when the magnet is energized. >

A method to quench and recharge avalanche photo diodes for use in high rate situations

We present a new method of using avalanche photo diodes (APDs) for low level light detection in Geiger mode in high rate situations such as those encountered at the Superconducting Super Collider (SSC). The new technique is readily adaptable to implementation in CMOS VLSI.

Tunnel Boring Begins at Superconducting Super Collider

The first of the Superconducting Super Collider's 60‐foot‐wide tunnel‐access shafts opens down into a cavernous magnet‐transfer area 236 feet below the sod of Ellis County, Texas. Some eight thousand 50‐foot‐long superconducting bending magnets will eventually be lowered down such access shafts, arrayed around the 54‐ mile‐circumference underground SSC ring. Just after this picture was taken at the end of December, the first of the SSC's 250‐ton “inchworm” tunnel borers was lowered down the shaft in segments to begin the actual boring of the 14‐foot‐high SSC tunnel.

Current dependence of harmonic field coefficients of 5-cm-aperture, 15-m-long SSC dipole magnet prototypes

Eighteen 5-cm-aperture, 15-m-long Superconducting Super Collider (SSC) dipole magnet prototypes have been produced and cold tested. On each prototype, the dependence of harmonic field coefficients on magnetic current was measured as part of a study of the magnetic field quality. For most of the magnets, the observed behavior conforms to what can be expected from the effects of persistent magnetization currents and iron yoke saturation. A few prototypes, however, exhibited anomalies during current ramp at 4 A/s which can be attributed to large cable eddy currents.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

An examination of the properties of SSC Phase II R&amp;D strands

The authors summarize a detailed characterization of the Superconducting Super Collider (SSC) Phase II R&D billets, samples of which were supplied to the University of Wisconsin (UW). An important part of the SSC Phase I and II strand R&D programs was an extensive sampling scheme that covered the entire fabrication process of the strand. Samples were sent to UW, where complete microstructural and physical property analysis could be performed. In addition, sufficient extruded pre-heat-treatment multifilamentary material was provided to OW so that parallel processing to strand could be performed. In Phase I material it was found that the 2 vol% Nb diffusion barrier thickness was insufficient to prevent extrinsic limitation of the critical current density (J/sub c/). This contrasted with the Phase II strand which incorporated 4% barriers and showed intrinsic behavior. The intrinsic nature of the Phase II conductor has made it possible to probe the basic microstructure property relationships of the strand and provide insight into improvements in future processing. >

Magnetic field angle changes during manufacture and testing of SSC collider dipoles

Measurements of the magnetic field angle along the length of collider dipole magnets are discussed. These superconducting magnets were built at Fermilab for the Superconducting Super Collider (SSC) by Fermilab and General Dynamics personnel. These measurements were made at four stages in the assembly and test sequence. The data show that changes can occur both during installation in the cryostat and as a result of cold testing. Most of the changes during installation are correlated with the welding of the tie bar restraints, but the changes observed as a result of the cold testing can be attributed to changes in the magnetization of the iron laminations. >

Locating the magnetic center of the SSC CDM using a temporary quadrupole field

For the Superconducting Super Collider (SSC) to meet its physics requirements, the magnetic center of each collider dipole magnet (CDM) must be accurately aligned. A technique has been developed to determine the magnetic center of the SSC dipole magnet under ambient test conditions. This technique involves flowing current in the upper half of the coils in the direction opposite to the current in the lower half. This is done using a temporary lead connected to the splice joining the two coil halves and two matched power supplies. The resulting field is primarily skew quadrupole and has high field gradients which allow the center to be accurately located. The viability of this method has been verified by analysis using a Taylor series expansion of the resulting magnetic field. The analysis has also verified that off-the-shelf power supplies have low enough mismatch to be used in this technique. The analytical results have been verified through the test of a short dipole magnet at the Brookhaven National Laboratory.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Development of ductile, high current density multifilament niobium-titanium superconducting wire for SSC corrector magnets

A superconducting corrector magnet wire was developed for the Superconducting Super Collider (SSC) which surpassed all performance specifications. Critical current requirements were met while maintaining the high degree of ductility necessary for manufacturing the intricate magnet coils. Data suggest that ductility specifications can be met with current densities exceeding 3000 A/mm/sup 2/ at 5 T. Indications are that electrical performance can be further increased without compromising piece length, ductility, or manufacturability.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Magnetic and mechanical considerations in the design of the SSC collider dipole magnet end region

The end regions of the Superconducting Super Collider (SSC) collider dipole magnets. (CDMs) were designed to meet both magnetic and mechanical requirements. The authors present an optimized end design for CDM magnets that is mechanically producible and possesses desirable magnetic field quality, peak field, and magnetic length properties. A three-dimensional magnetic field distribution was calculated for this end-turn design using the finite element program TOSCA. The effective magnetic length, integrated multipole content, and peak fields are extracted from the results of the finite element model. These results compare favorably with those from a second analysis program, ENDTURN, that is based on an analytic solution to the defining field equations.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

A facility to test short superconducting accelerator magnets at Fermilab

The superconducting magnet R&D facility at Fermilab (Lab 2) has successfully tested superconducting dipole, quadrupole, and correction coil magnets less than 2 m in length for the Superconducting Super Collider (SSC) project and the Tevatron D0/B0 Low- beta Insertion. The authors describe the Lab 2 facility and the several upgrades which were developed to accomplish these successful test programs. Several improvements have been made to the facility that have greatly enhanced its magnet testing capabilities. Among the upgrades have been a new rotating coil and data acquisition system for measuring magnetic fields, a controlled flow liquid helium transfer line using an electronically actuated cryo valve, and stand-alone systems for measuring AC loss and training low current Tevatron correction coil packages. Tests are performed in vertical dewars of boiling liquid helium. >