Tender: Dry Dilution Refrigerator for Cryogenic RF and Quantum Hardware Characterisation — <=10 mK, 20+ Coaxial Lines, Large Mixing Chamber

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The National Physical Laboratory (NPL) is seeking a supplier for a dry (cryogen-free) pulse-tube cooled dilution refrigerator system to characterise quantum hardware and RF/quantum circuits with a vacuum sample volume. The system must include thermometry, associated wiring and readout electronics with provision to add temperature sensors in future, and be designed to complement existing measurement systems for higher throughput with faster cooldowns typically every two weeks. It must be suitable for RF measurements of complex quantum circuits, equipped with 20 or more coaxial lines with future expandability, including high-attenuation input lines for sensitive quantum devices and low-loss output lines for low-noise amplifiers and isolators; some coaxial lines must operate up to 40 GHz with provision to add higher-frequency cabling later. The system must provide a sufficient number of configurable DC lines to bias at least tens of RF multi-way switches, at least four low-noise amplifiers, and dedicated high-resistance and low-resistance DC looms with future expandability. Required performance and space include a base temperature <= 10 mK with access to the PT2 and other intermediate stages, a mixing chamber plate horizontal area of at least 0.19 m2, and vertical experimental sample space below the mixing chamber of at least 400 mm for custom apparatus; a magnet is not required.