CHAPTER 4: WIRING AND CONNECTIONS Click on any of the links below to download high resolution pdfs of any figure FIG. 4.1: Thermal resistivity of common wire materials FIG. 4.2: Cross-sectional view of a heat-sink scheme for larger probes (<= 2 cm diameter) FIG. 4.3: Amount of liquid helium remaining after pumping the bath down to various temperatures FIG. 4.4: Illustration of noninductive winding scheme for further minimizing induced voltages in instrumentation leads when making measurements in high magnetic fields FIG. 4.5: Beryllium-oxide heat-sink chips for thermally anchoring instrumentation leads FIG. 4.6: Technique for attaching fine electrical leads to small samples, especially when using weak silver paint to contact the sample FIG. 4.7: Technique for attaching a bare copper wire to a copper block, which minimizes thermoelectric voltages FIG. 4.8: Several schemes for making low-thermoelectric-voltage connections between the test apparatus leads and the leads from a sensitive voltmeter FIG. 4.9: Connector box Ð nonvacuum tight FIG.4.10: Conventional multipin D-connector adapted for a vacuum tight seal FIG. 4.11: Connector chamber Ð vacuum tight FIG. 4.12: Vacuum-tight aluminum connector box with removable plates for mounting commercial vacuum-tight multiple-pin connectors FIG. 4.13: Removable vacuum lead-through for continuous leads to minimize thermoelectric voltages FIG. 4.14: Dewar arrangements for high-current testing FIG. 4.15: Superconducting rf transmission lines FIG. 4.16a: Optimum wire diameter for a single copper wire conducting current I from a region of the cryostat at temperature T upper to a temperature Tlower FIG. 4-16b: Minimum heat input for a single copper wire conducting current I from a region of the cryostat at temperature Tupper to a temperature Tlower FIG. 4.17: Illustration of a 150 A vapor-cooled high-current lead FIG. 4.18: Helium-gas trap for venting a dewar without allowing air to condense and freeze in the dewar or vapor-cooled leads FIG. 4.19: Critical-current density as a function of magnetic field at various temperatures for a Bi2Sr2Ca2Cu3O10 current lead FIG. 4.20: Flexible high-current lead References: Listing of all References for Chapter 4 Figures
