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Superconducting Gravity Gradiometry

Superconducting Gravity Gradiometry. State of the Art. Superconducting Gravity Gradiometry. Present status Key technologies Conclusions. Present status: low-Tc. Maryland design (Paik et.al. 1996/2002) Noise level: 20 mE /  Hz (4 mE /  Hz) CMRR (lin.): 10 4. Oxford Instruments (2001)

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Superconducting Gravity Gradiometry

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  1. SuperconductingGravity Gradiometry State of the Art Univeristy of Twente

  2. SuperconductingGravity Gradiometry • Present status • Key technologies • Conclusions Univeristy of Twente

  3. Present status: low-Tc Univeristy of Twente

  4. Maryland design (Paik et.al. 1996/2002) • Noise level: 20 mE /Hz (4 mE /Hz) • CMRR (lin.): 104 Univeristy of Twente

  5. Oxford Instruments (2001) • CMRR: 8104 (>106) • Noise level: 180 mE/Hz (?) (1 mE/Hz) Univeristy of Twente

  6. UWA (van Kann et.al. 2002) • Noise level: 0.5 E/Hz • CMRR (ang.): >104 (106) • CMRR (lin.): 109 (31010) Univeristy of Twente

  7. Gravitec (Veryaskin 2000) • Noise level: 3 E/Hz • CMRR: ? Univeristy of Twente

  8. Univ. Kharkov (verozub 1996) • Magnetic levitation of proof mass • Low intrinsic noise level… • Lateral stability… • Potential for miniaturization… F = 0 for I1 = 0. Univeristy of Twente

  9. High-Tc • High-Tc conceptual design study on basis of Maryland device1 • Predicted sensitivity • 4 mE/Hz @ 1 Hz and 77 K • 2.5 mE/Hz @ 0.1 Hz and 28 K 1 C.S. Jacobsen et. al., Conceptual Design of a Gravity Gradient sensor based on high Tc superconducting technology, ESA contract 9031/90/NL/PB CCN2 final report May 1995 Univeristy of Twente

  10. Key technologies: materials • Low-Tc • Nb @ 4 K • High-Tc • YBCO @ 77 K • Bi, Tl, Hg families • MgB2 • Tc of 39 K, operating temp. 35 K • Test masses • High quality Nb or Si Univeristy of Twente

  11. Key technologies: SQUIDS • Low-Tc • Nb: improved sensitivity • Well developed technology • High-Tc • YBCO: limited progress since 1995 • Lifetime: no significant improvement • Coupling coils: still difficult (T) • MgB2 • Research in full swing • At present no sophisticated junction technology • More work needed Univeristy of Twente

  12. Key technologies: levitation coils • Nb • Fulfils requirements • BSCCO • Joining still a problem • Tapes 0.2x5 mm2 (big) • Geometry: react after wind, limited strain • Other materials not suitable • MgB2 • First results wit powder in tube, but improvement in properties needed • Joints not yet realised Univeristy of Twente

  13. Key technologies: electronics • SQUID electronics for both low-Tc and high-Tc has improved in sensitivity and speed • Modulation techniques are available for improved signal to noise ratios at low frequencies Univeristy of Twente

  14. Key technologies: cooling1 • Cooler mass • 4K  100 kg • 35K  10 kg • 77K  1 kg Recent overview for cryocoolers in space: ISEC, 6-9 september 2005, Noordwijkerhout Univeristy of Twente

  15. Key technologies: cooling • Efficiency: Pin @ 0.3W • 2kW @ 4K • 20W @ 40K • 7W @ 77K Univeristy of Twente

  16. Key technologies: cooling • Mass vs. volume Univeristy of Twente

  17. Conclusions • Low-Tc: possible, size reduction possible, cooler has large mass and requires a lot of power • MgB2: research is underway, has to prove itself, cooling hast intermediate mass and power requirements • High-Tc: looks possible when several practical issues have been solved (maybe hybrid structure with MEMS), cooler has acceptable mass and power requirement Univeristy of Twente

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