P.O. Mazur

About the mechanics of SSC dipole magnet prototypes

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 cool...

Fermilab r & d Test Facility for SSC Magnets

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.

Performance of full-length SSC model dipoles: Results from 1988 tests

Over the past year, magnets that meet the SSC field and quench training criteria have been developed as a result of the detailed understanding of magnet performance made possible by tests on a series of model magnets. The SSC dipole magnet design is a cos θ style coil with a 4-cm aperture and a magnetic length of 16.6 m. The design operating field is 6.6 T at a current of 6.5 kVA. Design, fabrication, and testing of full-length model magnets has been a cooperative effort among the SSC Central Design group and three major national laboratories: BNL, FNAL, and LBL.

Quench Characteristics of Full-Length SSC R&D Dipole Magnets

Several 17-meter-long SSC R&D dipole magnets, instrumented with numerous voltage taps on the inner quarter coils, have been tested. These magnets, protected with quench heaters, differed in mechanical details as well as in the cables used for the winding. The voltage taps enabled us to measure longitudinal and azimuthal quench propagation velocities. Summary plots of these velocities are presented showing that, even though the Fourier conduction model doesn’t apply, the mechanism of the quench is reproducible from magnet to magnet. Correlations are established between the velocities and the fraction of short sample. After showing that for currents higher than 5000 A the magnet is self-protected, we investigate the relation between the number of MIITs and the quench characteristics.

Status of 4-cm Aperture, 17-m-Long SSC Dipole Magnet R&D Program at BNL Part I: Magnet Assembly

Over the last year-and-a-half, several 4-cm-aperture, 17-m-long dipole magnet prototypes were built by Brookhaven National Laboratory (BNL) under contract 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 prepare the way of the 5-cm-aperture dipole magnet program to be started soon. In this paper, we analyze the mechanical behavior of the BNL prototypes during cool-down and excitation, and we attempt to relate this behavior to the magnet features. The data reveal that the mechanical behavior is sensitive to the vertical collar-yoke interference, and that the magnets exhibited somewhat erratic changes in coil end-loading during cool-down. 9 refs., 6 figs.

Quench protection of SC quadrupole magnets

The high gradient quadrupole (HGQ) being developed for the LHC interaction regions by the collaboration of FNAC/LBNL/BNL, relies on the use of quench protection heaters. As part of the HGQ R&D program at Fermilab, Tevatron low-/spl beta/ quadrupoles installed with quench protection heaters were tested in normal and superfluid helium. This paper focuses on heater operation time delay and quench propagation velocity measurements since these are important input parameters for designing the quench protection system of the HGQ.

Investigation of Heater-Induced Quenches in a Full-Length SSC R&D Dipole

A 17-m-long SSC R&D dipole magnet instrumented with quench heaters and numerous voltage taps has been tested. These voltage taps enable (1) accurate localization of the quench start, (2) detailed studies of quench development, and (3) determination of coil temperature rise during a quench. The hot-spot temperature is determined by measuring the resistance of the conductor in the vicinity of the heater and is plotted versus number of MIITs. Measured temperatures are found to be in good agreement with predictions based on the assumption that the conductor is heated adiabatically. Finally, a limit to be imposed on the number of MIITs to operate the magnet safely is determined.

Test of Fermilab built, post-ASST, 50-mm-aperture, full length SSC dipole magnets

During 1992 at Fermilab, a series of nine 50-mm-aperture, 15-m-long, SSC superconducting dipole magnets, designed jointly by Fermilab, Brookhaven National Laboratory, and the SSC Laboratory, have been built and successfully cold tested. Seven of these dipole magnets, designated for the Accelerator System String Test (ASST) carried out at SSCL in Dallas, were assembled at Fermilab by General Dynamics personnel, and have achieved the nominal operating current level without significant training.1,2 In addition, a series of four R&D magnets (DCA320 323) were manufactured at Fermilab to test an alternative insulation schemes. In this paper we present the quench performance of these four R&D magnets, which were cold tested at the Fermilab Magnet Test Facility at nominal temperatures of 4.35 K, 3.85 K, and 3.50 K. An extended characterization test was performed on one of these magnets (DCA322). During this test the magnet was successfully cooled down to superfluid He temperature (1.8 K) and reached a field B ≥ 9.5 T.

Reducing The Energy Requirements of Quench Protection Heaters for SSC Dipoles — Test Results

Design considerations and first test results of quench protection heaters for Superconducting Super Collider (SSC) collider dipole magnets have been presented in earlier papers. 1,2

Experimental Evaluation of Design Features of a Cryostat for an Ironless cosine theta SSC Magnet

A conceptual design for an iron-less cosθ SSC magnet cryostat has identified several areas for experimental study. Included are bowing of thermal radiation shields due to cooldown and warmup; thermal performance of the suspension systems; cryostat thermal performance; structural responses to decentering forces between the coil and the steel vacuum vessel; and response of thermal shields to forces due to quench induced eddy currents. Studies were carried out with 6m long thermal bowing and magnetic effects models, a suspension heat leak measurement dewar and a 12m long thermal model. The models incorporate important features of the conceptual cryostat design. The details of the test arrangements, procedures and results are presented.