R. C. Niemann

Design and Analysis of the SSC Dipole Magnet Suspension System

The design of the suspension system for Superconducting Super Collider (SSC) dipole magnets has been driven by rigorous thermal and structural requirements. The current system, designed to meet those requirements, represents a significant departure from previous superconducting magnet suspension system designs. This paper will present a summary of the design and analysis of the vertical and lateral suspension as well as the axial anchor system employed in SSC dipole magnets.

SSC Magnet Cryostat Suspension System Design

The design of the cryostat for the Superconducting Super Collider (SSC) dipole magnets has largely been driven by the design of the cold mass suspension and anchor systems. Rigorous structural requirements in combination with low allowable heat loads have resulted in a suspension system that represents a significant departure from current superconducting magnet design practice both in performance concept and materials selection. This paper presents a summary of the suspension and anchor system designs being employed in the SSC.

Thermal Performance Measurements of a 100 Percent Polyester MLI System for the Superconducting Super Collider; Part I: Instrumentation and Experimental Preparation (300K - 80K)

Thermal performance measurements of a 100 percent polyester multilayer insulation (MLI) system for the Superconducting Super Collider (SSC) were conducted in a Heat Leak Test Facility (HLTF) under three experimental test arrangements. Each experiment measured the thermal performance of a 32- layer MLI blanket instrumented with twenty foil sensors to measure interstitial layer temperatures. Heat leak values and sensor temperatures were monitored during transient and steady state conditions under both design and degraded insulating vacuums. Heat leak values were measured using a heatmeter. MLI interstitial layer temperatures were measured using Cryogenic Linear Temperature Sensors (CLTS). Platinum resistors monitored system temperatures. High vacuum was measured using ion gauges; degraded vacuum employed thermocouple gauges. A four-wire system monitored instrumentation sensors and calibration heaters. An on-line computerized data acquisition system recorded and processed data. This paper reports on the instrumentation and experimental preparation used in carrying out these measurements. In complement with this paper is an associate paper bearing the same title head, but with the title extension PART II: LABORATORY RESULTS (300K-80K).1

Heat Leak Measurement Facility

Heat leak measurements of superconducting magnet suspension systems, and multilayer insulation (MLI) systems are important for the optimum design of magnet cryostats. For this purpose, a cryogenic test facility was developed having a versatile functional end in which test components of differing geometrical configurations can be installed and evaluated. This paper details the test facility design and operating parameters. Experimental results of heat leak measurements to 4.5 K obtained on a post type support system having heat intercepts at 10 K and 80 K are presented. Included are measurements obtained while operating the 10 K intercept at temperatures above 10 K, i.e., in the 10-40 K range. Also reported is a description of the test facility conversion for a heat load study of several MLI systems with variations of MLI installation technique. The results of the first MLI system tested are presented.

Design, Construction and Performance of a Post Type Cryogenic Support

A support member for superconducting magnets and other cryogenic devices has been designed, fabricated and structurally and thermally evaluated. The member is a cylindrical post constructed with fiber reinforced plastic (FRP) tubing and having metallic heat intercepts and end connections. All FRP to metal connections are made by mechanical shrink fitting and do not employ adhesives or fasteners. The post can operate in tension, compression and flexure or in combinations of these loads. The details of the design and construction are enumerated. Structural performance has been measured in tension and compression at 80 and 300 K and in flexure at 300 K. Creep effects on the shrink fit joint reliability are being evaluated. Thermal performance has been measured for a post with ends at 4.5 and 300 K and with heat intercepts at 10 and 80 K. The measured performance has been compared with the analytical predictions. Full scale, working, prototype posts have been successfully utilized in several model cryostats for the Superconducting Super Collider dipole magnet development program.

Design, construction and test of a full scale SSC dipole magnet cryostat thermal model

As a part of the SSC main ring superconducting magnet development program, a full length dipole magnet thermal model has been constructed and its thermal performance measured. Presented are the details of the cryostat design and the thermal model construction experience and its evaluation. The methods for and the preliminary results of the thermal performance measurements are presented and compared with the predicted performance.

Superconducting Super Collider second generation dipole magnet cryostat design

The second-generation cryostat design for the Superconducting Super Collider has been developed utilizing the experiences gained during the construction, installation and operation of several full-length first-generation dipole magnet models. The nature of the cryostat improvements is described. Considered are the connections between the magnet cold mass and its supports, cryogenic supports, cold mass axial anchor, thermal shields, insulation, vacuum vessel, and interconnections. The details of the improvements are enumerated and the results of available component and system evaluations are presented. >

Cryogenic Support Thermal Performance Measurements

The stringent refrigeration requirements of the Superconducting Super Collider (SSC) and the premium nature of radial space in the SSC cryostat have led to the development of a reentrant tube cryogenic support. Thermal shrink fitting techniques are used to assemble the support. The thermal performance of two cryogenic support models is presented. The geometry of each model, its instrumentation, and experimental test arrangement in a Heat Leak Test Facility are described. Heat leak and temperature profile measurements made with a primary heat intercept temperature controlled between 10 K and 40 K are presented. Heat leak values to 4.5 K were measured by means of a heatmeter. Heat leak values to the primary and secondary heat intercepts were derived using the measured temperature profiles and component material properties. Presented are thermal performance measurements of copper cable connections used to heat sink the primary and secondary heat intercepts to their respective thermal radiation shields. Temperature measurements also were made on identical model supports installed in a full length (17.5 meters long) SSC dipole magnet cryostat thermal model. The thermal performance of the cryogenic supports for the two measurements is compared.

Model magnet studies

A design, construction, and testing program for model magnets is underway at Fermilab to evaluate alternatives in the development of small aperture magnets. The most thoroughly developed of these programs utilizes a set of model magnets based on the Tevatron quadrupoles and dipoles as a standard. These 7.6cm aperture model magnets, approximately 64cm long, have construction or material changes which are to improve quality and/or cost effectiveness. There are also superconductor parameter changes, as well as construction and materiai parameters, which impact or give insight into the choices of material specifications and construction parameters for the 5cm aperture model magnet series which are prototype candidates for the Superconducting Super Collider (SSC) ring magnets. The test program consists of performance test quenching of the windings at various temperatures until the cable critical current is reached. The quality of the magnetic field (Fourier coefficients) B(n) and quenching current is measured versus ramp rate, dB/dt, intensity, B, magnet temperature, and conductor parameters. The magnetization of the windings is measured as a function of these same parameters. There are also other special measurements made, i.e., deflection of coils. Two 5cm diameter aperture SSC candidate dipoles without iron are being prototyped: (a) a two layer, 6kA/turn version and (b) a single layer 10kA/turn model. In addition, there is a collaborative effort between KEK and FNAL in the development of a 10T (dipole, a longer range model) magnet program.

Improved Design for a SSC Coil Assembly Suspension Connection

Close control of the alignment of magnets for the proposed Superconducting Super Collider (SSC) high energy physics research facility is essential for the success of this small bore accelerator. The connection of the magnet coil assembly to the cryostat suspension system presents many challenges to the cryostat designer. The resulting design must withstand shipping and seismic loads, allow axial contraction of the coil assembly, position the coil assembly center line within a 0.25 mm radius, provide rotational adjustment of the coil, resist axial quench loads, provide a bearing assembly which is tolerant to high vacuum, high radiation and cryogenic conditions, and fit within the stringent geometric constraints of the cryostat assembly. A coil assembly suspension connection which meets these criteria is described. Measurements of the effective friction coefficient, static load deflection, and component stresses are compared to the predicted performance. Experiences with a full length model of the coil assembly connection are presented.