SQUIDs Then and Now: From SLUGs to Axions

Transcription

1 SQUIDs Then and Now: From SLUGs to Axions SQUIDs Then SQUIDs Now Cold Dark Matter: The Hunt for the Axion Josephson 50 th Anniversary Applied Superconductivity Conference Portland, OR 9 October 2012

2 SQUIDs Then

3 1 October 1964 Royal Society Mond Laboratory Cambridge University Thesis advisor: Brian Pippard Thesis research required measuring voltages of to10 13 volts Eric Gill 1933

4 A Superconducting Galvanometer A. B. Pippard and G. T. Pullan 1951 Tangent magnetometer Magnet and mirror suspended from a long quartz fiber at the centre of a Helmholtz pair Current in the coil caused a deflection of a reflected light beam Voltage resolution 1 pv in 12 s ( 3 pvhz -1/2 )

5 Brian Josephson Explains Tunneling Courtesy Brian Josephson November 1964

6 Φ = n Φ 0 Φ 0 h/2e 1961 to J Deaver and Fairbank Doll and Näbauer I Insulating barrier Superconductor 1 Superconductor 2 V ~ 20 Å Josephson I Φ Anderson and Rowell I 0 Φ 0 Φ Jaklevic, Lambe, Silver and Mercereau

7 The Very Next Day November 1964 Brian Pippard: John, How would you like a voltmeter with a resolution of V in 1 second? Courtesy Kelvin Fagan

8 Brian s Idea R I V in L L V out M = L τ = L/R M Digital voltmeter: I Φ0 = Φ 0 /M = Φ 0 /L Voltage resolution: V in = I Φ0 R = Φ 0 /τ = V for τ = 1 s

9 At Tea Paul Wraight pointed out that Nb has a surface oxide layer and PbSn solder is a superconductor (February 1965)

10 At Tea Paul Wraight pointed out that Nb has a surface oxide layer and PbSn solder is a superconductor (February 1965) Niobium Before dinner I I Copper V SnPb solder 5 mm

11 The Very Next Day I Niobium Brian Pippard: It looks as though a slug crawled through the window last night and expired on your desk! I Copper V SnPb solder 5 mm

12 The SLUG (Superconducting Low-Inductance Undulatory Galvanometer) Nb wire and solder I Niobium I B I Copper Voltage V SnPb solder 5 mm Current I B in niobium wire I B February 1965

13 The SLUG as a Voltmeter Niobium V 1 µω δv δφ Φ Φ o Copper V Analog voltmeter 5 mm Solder Voltage noise at 4.2 K 10 fvhz -1/2 (10-14 VHz -1/2 )

14 Observation of Charge Imbalance (1) (4) V d (nv) SLUG V d (3) (2) I(mA) Current injected through the Al-AlOx-Sn junction creates a charge imbalance between the electron-like and hole-like quasiparticle branches in the superconducting Sn film. This imbalance establishes a potential difference across the Sn-SnOx-Cu junction. Detailed investigation of nonequilibrium superconductivity. V V(mV) JC 1972

15 Adjustable Niobium SQUID Nb wire and foil 0.03 Nb wire Nb foil mylar Beasley and Webb 1967

16 and Now

17 Thin-Film, Square Washer DC SQUID Ketchen and Jaycox (1981) SQUID with input coil Josephson junctions Wafer scale process Photolithographic patterning 500 µm 20 µm Nb-AlOx-Nb Josephson junctions (John Rowell) At 4.2 K Flux noise: 1 2 µφ 0 /Hz 1/2 ~ Φ 0 /1,000,000 in 1 second

18 Superconducting Flux Transformer: Magnetometer B Closed superconducting circuit Magnetic field noise ~ THz -1/2 J SQUID Room temperature electronics

19 Magnetic Fields tesla Conventional MRI 10-4 Earth s field Car at 50 m Human brain response femtotesla Urban noise Human heart Fetal heart SQUID magnetometer

20 Quantum Design "Evercool"

21 UC Berkeley Flux Qubits Qubit 2 SQUID Qubit 1 35 µm UC Berkeley

22 High-T c SQUIDs Prospecting for Mineral Deposits Courtesy Cathy Foley, CSIRO

23 Gravity Probe-B Tests of General Relativity Geodetic effect curved space-time due to the presence of the Earth Lense-Thirring effect dragging of the local space-time frame due to rotation Courtesy Stanford University and NASA Gyroscopes: Spinning, niobium-coated sapphire sphere develops magnetic dipole moment, read out by a SQUID

24 South Pole Telescope: Searching for galaxy clusters Antarctica 9,500 feet 960 transition edge sensors with multiplexed SQUID readout 12,000 SQUIDs The Bullet Cluster UC Berkeley + Many other groups

25 300-Channel SQUID Systems for Magnetoencephalography (MEG)

26 Magnetic Resonance Imaging at 132 µt UC Berkeley

27 Cold Dark Matter: The Hunt for the Axion S.J. Asztalos G. Carosi C. Hagmann D. Kinion, K. van Bibber M. Hotz L.J. Rosenberg G. Rybka, J. Hoskins J. Hwang P. Sikivie D. B. Tanner R. Bradley JC

28 Our Bizarre Universe 400 Intensity (MJy sr -1 ) K Neutrinos 0.6% Baryons (ordinary matter) 4.6% Dark Energy (DE) 73% Cold Dark Matter (CDM) 22% Frequency (GHz) A candidate particle for CDM is the axion, proposed in 1978 to explain the absence of a measurable electric dipole moment on the neutron Roberto Peccei and Helen Quinn 2013 J.J. Sakurai Prize An alternative candidate particle is the WIMP Weakly Interacting Massive Particle Blas Cabrera and Bernard Sadoulet 2013 W.K.H. Panofsky Prize

29 Resonant Conversion of Axions into Photons Pierre Sikivie (1983) Primakoff Conversion HEMT* Amplifier Magnet Predicted axion mass: m a 1 µev 1 mev ( GHz) Need to scan frequency Expected Signal Cavity Power ν ν ~ 10 6 *High Electron Mobility Transistor Frequency

30 Axion Dark Matter experiment (ADMX) Originally: Lawrence Livermore National Laboratory Now: University of Washington, Seattle Cooled to 1.5K 7 tesla magnet

31 Amplifier Noise Temperature R T i -A V SV (f) = A 4k B + [ T T ( R) ]R i N Quantum limit: T Q = hf/k B

32 LLNL Axion Detector Original system noise temperature: T S = T + T N 3.2 K Cavity temperature: T 1.5 K Amplifier noise temperature: T N 1.7 K Time to scan the frequency range from f 1 = 0.24 to f 2 = 0.48 GHz: τ(f 1, f 2 ) 4 x (T S /1 K) 2 (1/f 1 1/f 2 ) sec 270 years

33 Microstrip SQUID Amplifier: Principle Conventional SQUID Amplifier Microstrip SQUID Amplifier (MSA) Source connected to both ends of coil Gain (db) Frequency (MHz) Source connected to one end of the coil and SQUID washer; the other end of the coil is left open

34 MSA Gain Measurements Gain for four coil length Gain (db) mm νres ν (MHz) mm Coil Length (mm) 7 mm mm Frequency (MHz) M. Mück, J. Gail, C. Heiden, M-O André, JC

35 MSA Noise Temperature vs. Bath Temperature Gain = 20 db T Q Quantum limit T Q = 30 mk T bath = 50 mk Noise temperature: T N opt = 48 ± 5 mk Darin Kinion, JC

36 MSA:Impact on Axion Detector Original LLNL axion detector: T S 3.2 K Microstrip SQUID amplifier: T N 50 mk Next generation: Cool system in a dilution refrigerator to 50 mk For T T N 50 mk: T S T + T N 0.1 K Scan time T s2 : τ(0.24 GHz, 0.48 GHz) 270 years x (0.1/3.2) days ADMX II now funded at the University of Washington by DOE

37 Epilogue SQUIDs are remarkably broadband: 10 4 Hz (geophysics) to 10 9 Hz (axion detectors). At low temperatures, the resolution of SQUID amplifiers is essentially limited by Heisenberg s Uncertainty Principle. SQUIDs are amazingly diverse, with applications in physics, chemistry, biology, medicine, materials science, geophysics, cosmology, quantum information,..

38 Then Brian: Thanks and Congratulations! and Now