CHAPTER 7: SAMPLE HOLDERS

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FIG. 7.1: Example of a sample holder for measuring critical current in short, straight samples

FIG. 7.2: Two-lead arrangement and four-lead arrangement for measuring transport properties

FIG. 7.3: Tubular sample mount for measuring coiled conductors in the small bore of a high-field solenoidal magnet

FIG. 7.4: Dual sample holder for variable-angle measurements

FIG. 7.5: Thermal contraction of the radius Δ<em>R/R</em> on cooling from 293 K to 76 K for G-10 fiberglass-epoxy "rolled" tubes

FIG. 7.6: Composite sample holder engineered to match the thermal contraction of the sample

FIG. 7.7: Technique for reducing inductive noise voltage arising from magnetic-field variations or sample motion

FIG. 7.8: Noninductive winding scheme, where one of the voltage leads is wound counter to the test sample to minimize the loop area and induced electromagnetic noise

FIG. 7.9: Relevant lengths for voltage-tap placement and current-contact lengths

FIG. 7.10: Influence of current-transfer voltage on the voltage V vs. current I characteristic of a superconductor

FIG. 7.11: Current-transfer length x min for typical Nb-Ti and Nb3Sn multifilamentary superconductors

FIG. 7.12: Anomalous V-;Icharacteristic of a short Nb-;Ti sample

FIG. 7.13: Model of equipotential lines for the superconductor test setup and data shown in Fig. 7.12

FIG. 7.14: Good and bad supports for high-current testing of short samples

FIG. 7.15: Test mandrel for Nb-Ti superconductor

FIG. 7.16: Combination reaction-and-measurement mandrel for Nb3Sn

FIG. 7.17: Schematic illustration of spring-loaded pogo pins that press the test chip against a copper base support

FIG. 7.18: Test chip located in a wire-bond chip carrier or package

FIG. 7.19: Illustrations of wire-bond procedure

FIG. 7.20: Detailed illustration of a pogo pin for making electrical pressure contacts to small contact pads

FIG. 7.21: Fuzz buttons for making electrical pressure contacts to small contact pads or device leads

FIG. 7.22: Beryllium-copper contact microsprings

FIG. 7.23a: Third-harmonic technique for measuring transport properties of thin films - Experimental data plot

FIG. 7.23b: Third-harmonic technique for measuring transport properties of thin films - Calculated dependence of K

FIG. 7.25: Cross-sectional view of practical high-Tc superconducting composites

References: Listing of all References for Chapter 7 Figures