SQUID System Issues

This chapter contains sections titled: Introduction Cryogenics Introduction Liquid Cryogen Cooling (Cryostats) Cryogenic Refrigerators (Cryocoolers) Introduction Joule–Thomson Coolers Stirling Coolers Gifford–McMahon Coolers Pulse-tube Coolers Comparison of Cryocoolers Trends in Cryocooling Cryostat or Cryocooler? Cryocooler-interference Reduction Interference Mechanisms Time Separation Space Separation Low-noise Coolers Noise Suppression Techniques Material Properties Cabling and Electronics Shielding and Filtering of Noise Sources Introduction to Shielding Effectiveness Absorption Reflection High-frequency Shielding Low-frequency Shielding Filtering in an Unshielded Urban Environment Determination of Low-frequency Shielding, Filtering or Noise Cancellation Requirements Electronics and Cables RF Screening of Electronics Cables and Conductors Cable Junctions, Terminations, Connectors and Grounding Crosstalk Power Consumption and Supply Choice of SQUIDs and Electronics Data Acquisition and Rudimentary Signal Processing Introduction Hardware Considerations Dynamic Range, Accuracy and Linearity Sampling Rate and Signal Conditioning Digital Signal Conditioning and Storage Characterization, Calibration and Testing Introduction Characterizing SQUIDs Introduction Transfer Coefficient Effective Area of a Magnetometer Effective Volume of a Gradiometer SQUID Noise and Bandwidth Measurements Dynamic Range Slew Rate Nonlinearity Characterization in Various Magnetic Field Situations Introduction Field-applied (FA) Characterization Field-removed (FR) Characterization Hysteresis Calibration Setting up Calibration Fields Magnetometer and Gradiometer Calibration Testing and Practical Tips Drifts and Offsets SQUID or Flux Jumps Excess Noise Electronic Noise from Other Systems Adequate Shielding of the Cryostat Consequences of Cryogen Boil-off Mechanical Vibration Increase in Noise of the System Compared to a SQUID Conditions Imposed on SQUID Systems by the Environment and Applications Introduction Signals Acting on SQUID Systems Noise Acting on a SQUID System Environmental Noise in Stationary Applications Additional Noise in Mobile Instrumentation Noise Suppression Introduction Active Shielding Noise Cancellation by Primary Sensors Noise Cancellation Using References Introduction Static Systems Mobile Systems Noise Cancellation Without the References Signal and Noise Implications for the SQUID System Design Introduction Static SQUID Systems Mobile SQUID Systems Summary of Parameters Concluding Remarks and System Trends