The Original SQUID. Arnold H. Silver. Josephson Symposium Applied Superconductivity Conference Portland, OR October 9, 2012

Transcription

1 The Original SQUID Arnold H. Silver Josephson Symposium Applied Superconductivity Conference Portland, OR October 9, 2012

2 Two Part Presentation Phase One: Jaklevic, Lambe, Mercereau, Silver Microwave observations by John Lambe Thin film interferometers First two-josephson tunnel junction macroscopic quantum interference Quantum wave phase shifts Other tunnel junction macroscopic quantum interference experiments Phase Two: Silver and Zimmerman Point contacts Bulk Nb SQUIDs dc, rf, and R SQUIDs Flux-quantum based SQUID model Linearized SQUID magnetometer Measured SQUID flux-quantum states 1

3 Ford Scientific Lab Lambe, Zimmerman, Silver, Jaklevic, Mercereau 2

4 We Used 1960 s Technology Analog electronics Vacuum-tubes Oscilloscopes X-Y recorders Glass, double-jacket LHe dewars Manuscripts Typewritten Literally cut and paste Hand-plotting on graph paper Trace on vellum for publication 3 x 4 glass slides 3

5 Phase One: Jaklevic, Lambe, Mercereau, Silver Microwave observations by John Lambe First 2-Josephson tunnel junction macroscopic quantum interference Vector potential measurement Quantum wave phase shifts Other tunnel junction macroscopic quantum interference experiments 4

6 Periodic Microwave Signals (1963) Submitted to Physics Letters in June microgauss periodicity 5

7 First 2-Josephson-Junction Macroscopic Quantum Interferometer Microscope slide substrates Stainless steel shim masks Formvar insulating aperture A Sn thin films Tin thin-film macroscopic quantum interferometer with two Josephson tunnel junctions (1) and (2) 6

8 Measuring Josephson Tunnel Junction IC Oscilloscope trace Hysteretic I-V characteristic Requires current cycling 7 Automated measurement Sinusoidal current source Synchronous detector voltage linear in critical current

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10 Small solenoid inserted here 9

11 We Did Other Tunnel Junction Experiments Measured Josephson junction kinetic inductance, L J, vs I/I C at 30 MHz using an RCA rf voltmeter. Measured debroglie wavelength of supercurrent in a film thinner than the London-penetration-length which generates phase shifts along the film detected by Josephson junctions. 10

12 Phase Two: Silver and Zimmerman Point contact junctions Bulk Nb SQUIDs dc, rf, and R SQUIDs Flux-quantum based SQUID model Linearized SQUID magnetometer Measured SQUID flux-quantum states 11

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14 Junction Comparisons Josephson tunnel junction Hysteretic Millivolt signals Required current cycling Point-contact weak-link Single valued Microvolt signals V (µ µv) 13

15 Point Contact SQUIDs in Bulk Niobium SQUIDs were machined from bulk Nb Pointed Nb screws Screws were adjustable in LHe with long wrench, nut, and locking washer 14

16 Single Junction RF SQUID 15

17 RF SQUID Response RF Current Periodic in RF amplitude and magnetic field Similar to early microwave observations RF Voltage Φ 0 Φ 0 16

18 RF SQUID Oscilloscope Video 17

19 RF SQUID Diagnostics 18

20 SQUID Quantized Flux States and Transitions β = 2πLI C Φ 0 Single valued for β 1 Multiple-valued for β >1 β 1 For there is an inflection point where φ = φ ex = Φ 0 /2 and I = 0. 19

21 RF SQUID Flux Quantum States Measured With Linearized RF SQUID Magnetometer 20

22 SQUID Quantized States and Transitions Theory Measurement β >1 β <1 21

23 Resistive R-SQUID VCO Micro-ohm resistance X-band, 10 GHz, cavity Josephson ac effect V = Φ 0 f 22

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25 How We Did It! Good Luck Inquisitiveness Serendipity Persistence Free from programmatic constraints 24

26 First Magnetocardiogram MIT Magnet Lab Zimmerman, Cohen, Edelsack 25

27 SQUID Evolution Summary Ford Motor Company Scientific Laboratory