J. D. Gonczy

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.

Measuring Heat Leak with a Heatmeter

The heatmeter or more precisely the heat flow meter is a device based on thermal conductivity measuring tecniques. It consists of a thermal conducting body between two thermometers, with provisions for thermal connections and calibration. The paper describes the design, construction details, calibration and performance of one such heatmeter for use with heat reservoirs at either 4.2 K or 78 K. Near 4.2 K it has a sensitivity of 10 µW and requires less than a minute to reach steady state. Near 78 K its sensitivity is 10 mW and requires 25 minutes to reach steady state.

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.

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.

The Cryostat for the SSC 6 T Magnet Option

A design has been developed for an SSC 6T option dipole magnet cryostat. The design criteria that defines the basic parameters and performance requirements are discussed. Details of the single phase assembly, suspension, insulation, thermal shields, vacuum vessels and interconnections are presented. Results of the experimental program in support of the design effort are discussed.

A Blanket Design, Apparatus, and Fabrication Techniques for the Mass Production of Multilayer Insulation Blankets for the Superconducting Super Collider*

The multilayer insulation (MLI) system for the Superconducting Super Collider (SSC) consists of full cryostat length assemblies of aluminized polyester film fabricated in the form of blankets and installed as blankets to the 4.5K cold mass and the 20K and 80K thermal radiation shields. Approximately 40,000 MLI blankets will be required in the 10,000 cryogenic devices comprising the SSC accelerator. Each blanket is nearly 17 meters long and 1.8 meters wide. This paper reports the blanket design, an apparatus, and the fabrication method used to mass produce pre-fabricated MLI blankets. Incorporated in the blanket design are techniques which automate quality control during installation of the MLI blankets in the SSC cryostat. The apparatus and blanket fabrication method insure consistency in the mass produced blankets by providing positive control of the dimensional parameters which contribute to the thermal performance of the MLI blanket. By virtue of the fabrication process, the MLI blankets have inherent features of dimensional stability, three-dimensional uniformity, controlled layer density, layer-to-layer registration, interlayer cleanliness, and inter layer material to accommodate thermal contraction differences.

SSC Dipole Magnet Cryostat Thermal Model Measurement Results

Thermal performance of the conceptual design SSC dipole magnet cryostat has been experimentally evaluated. A full scale thermal model was constructed and open cycle thermal performance measurements were made. Details of the measurement program, measurement results and a comparison of predicted and measured performance are presented. The measurement methods and improvements of them for possible follow-on evaluations are discussed.

Multilayer Insulation (Mli) in the Superconducting Super Collider: A Practical Engineering Approach to Physical Parameters Governing Mli Thermal Performance

Multilayer insulation (MLI) is employed in cryogenic devices to control the heat load of those devices. The physics defining the thermal performance of an MLI system is extremely complex due to the thermal dynamics of numerous interdependent parameters which in themselves contribute differently depending on whether boundary conditions are transient or steady-state. The Multilayer Insulation system for the Superconducting Super Collider (SSC) consists of full cryostat length assemblies of aluminized polyester film, fabricated in the form of blankets, and installed as blankets to the 4.5K cold mass, and the 20K and 80K thermal radiation shields. Approximately 40,000 blankets will be required in the 10,000 cryogenic devices comprising the SSC accelerator. Each blanket will be nearly 56 feet long by 6 feet wide and will consist of as many as 32 reflective and 31 spacer layers of material. Discussed are MLI material choices, and the physical parameters which contribute to the operational performance of MLI systems. Disclosed is a method for fabricating MLI blankets by employing a large diameter winding mandrel having a circumference sufficient for the required blanket length. The blanket fabrication method assures consistency in mass produced MLI blankets by providing positive control of the dimensional parameters which contribute to the MLI blanket thermal performance. The fabrication method can be used to mass produce prefabricated MLI blankets that by virtue of the product have inherent features of dimensional stability, three-dimensional uniformity, controlled layer density, layer-to-layer registration, interlayer cleanliness, and interlayer material to accommodate thermal contraction differences.