During the last two years, nine 4‐cm aperture, 17‐m‐long dipole magnet prototypes were produced by Brookhaven National Laboratory (BNL) under contact with the Superconducting Super Collider (SSC) Laboratory These prototypes are the last phase of a half‐decade‐long R&D program, carried out in collaboration with Fermi National Accelerator Laboratory and Lawrence Berkeley Laboratory, and aimed at demonstrating the feasibility of the SSC main‐ring dipole magnets They also lay the groundwork for the 5‐cm‐aperture dipole magnet program now underway After reviewing the design features of the BNL 4‐cm‐aperture, 17‐m‐long dipole magnets, we describe in detail the various steps of their fabrication For each step, we discuss the paramaters that need to be mastered, and we compare the values that were achieved for the nine most recent prototypes The data appear coherent and reproducible, demonstrating that the assembly process is under control We then analyze the mechanical behavior of these magnets during cooldown and excitation, and we attempt to relate this behavior to the magnet features The data reveal that the mechanical behavior is sensitive to the collar‐yoke interference and that the magnets exhibit somewhat erratic changes in coil end‐loading during cooldown

About the mechanics of SSC dipole magnet prototypes

The test facility used for R&D testing of full scale development dipole magnets for the SSC is described. The Fermilab Magnet Test Facility, originally built for production testing of Tevatron magnets, has been substantially modified to allow testing also of SSC magnets. Two of the original six test stands have been rebuilt to accommodate testing of SSC magnets at pressures between 1.3 Atm and 4 Atm and at temperatures between 1.8 K and 4.8 K and the power system has been modified to allow operation to at least 8 kA. Recent magnets have been heavily instrumented with voltage taps to allow detailed study of quench location and propagation and with strain gage based stress, force and motion transducers. A data acquisition system has been built with a capacity to read from each SSC test stand up to 220 electrical quench signals, 32 dynamic pressure, temperature and mechanical transducer signals during quench and up to 200 high precision, low time resolution, pressure, temperature and mechanical transducer signals. The quench detection and protection systems is also described.

Fermilab r&d test facility for ssc magnets

A double bath superfluid helium dewar has been constructed and operated at Fermilab’s Magnet Test Facility. The 1.8 K portion of the dewar is sized to contain a superconducting magnet up to 0.5 meters in diameter and 4 meters long in a vertical orientation in 0.12 MPa pressurized superfluid. The dewar can also provide a subcooled Helium I environment for tests; the entire temperature range from 4.4 K to 1.8 K at 0.12 MPa is available. This paper describes the system design, lambda plate, heat exchanger, and performance.

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A 1400 Liter 1.8 K Test Facility

Full-length SSC R&D dipole magnets instrumented with four voltage taps on each turn of the inner quarter coils have been tested. These voltage taps enable (1) accurate location of the point at which the quenches start and (2) detailed studies of quench development in the coil. Attention here is focused on localizing the quench source. After recalling the basic mechanism of a quench (why it occurs and how it propagates), the method of quench origin analysis is described: the quench propagation velocity on the turn where the quench occurs is calculated, and the quench location is then verified by reiterating the analysis on the adjacent turns. Last, the velocity value, which appears to be higher than previously measured, is discussed.

Quench Start Localization in Full-Length SSC R&D Dipoles

In this paper we present results of quench testing of full length SSC dipole magnets at Fermilab. The data are from the first six of a series of thirteen 15 m long, 50 mm aperture SSC dipole magnets which are being built and tested at Fermilab. These magnets were designed jointly by Fermilab, Brookhaven Laboratory, Lawrence Berkeley Laboratory and the SSC Laboratory. Among the major goals for this series of magnets are to transfer magnet production technology to the lead vendor for the Collider Dipole Magnet, the General Dynamics Corporation, and to demonstrate industrial production by the vendor. The first magnet in the series, DCA311, was built by Fermilab technicians to establish assembly procedures. The second magnet, DCA312, was the “technology transfer magnet and was built jointly by Fermilab and General Dynamics technicians. The next seven, DCA313-319 are being built by General Dynamics personnel using Fermilab facilities and procedures. However, Fermilab personnel still operate the major tooling, provide the welders, perform assembly of items that would not be part of production magnets (e.g. voltage taps), and oversee the QA program. Five of these 7 GD-built magnets will be used in the Accelerator Systems String Test (ASST) to be carried out in Dallas later this year. The last four magnets, DCA320-323, are being built by Fermilab alone.”

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Quench performance of fermilab/general dynamics built full length ssc collider dipole magnets

The Fermilab Magnet Test Facility performs testing of full scale SSC magnets on test stands capable of simulating the cryogenic environment of the SSC main ring One of these test stands, Stand 5, also has the ability to operate the magnet under test at temperatures from 18 K to 45 K with either supercritical helium or subcooled liquid, providing at least 25 W of refrigeration At least 50 g/s flow is available from 23 K to 45 K, whereas superfluid operation occurs with zero flow Among the special components designed to permit this variety of operating modes are heat exchangers for both forced flow of normal fluid and stagnant superfluid and special check valves which provide a thermal barrier at each large-diameter penetration to the superfluid space Other unique features include 10000 A current leads mounted in a separate, removable can for easy lead replacement if necessary, and the room-temperature vacuum pumping system with a 25 g/s capacity at 12 Torr Cooldown time from 45 K to 20 K is 15 hours Instrumentation to monitor and control the cryogenic conditions is provided

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P. O. Mazur

Papers

A cryogenic test stand for full length SSC magnets with superfluid capability