1. Josephson effect (see also hand-out)
In 1962 Josephson predicted Cooper-pairs can tunnel through a weak link at zero voltage difference. Current in junction (called Josephson junction – Jj) is then equal to:
Electrical current flows between two SC materials - even when they are separated by a non-SC or insulator. Electrons "tunnel" through this non-SC region, and SC current flows.

2. Brian D. Josephson
The Discovery of Tunnelling Supercurrents
The Nobel Prize in Physics 1973

3. JJ’s essential in Superconducting Interference Devices
The SQUID may be configured as a magnetometer to detect incredibly small magnetic fields - small enough to measure the magnetic fields in living organisms.
Threshold for SQUID: T
Magnetic field of heart: T
Magnetic field of brain: T
Many uses in everyday life
Making measurements using SQUIDs
(magnetic susceptibility, static nuclear susceptibility, Nuclear Magnetic resonance...)
Biomagnetism
(magnetoencephalography [MEG], magnetocardiogram)
Scanning SQUID microscopy
Geophysical applications of SQUID
(oil prospecting, earthquake prediction, geothermal energy surveying)
Higher Temperature SQUIDs
(nondestructive testing of materials...)

4. Fig.2 Neuromag Ltd.122
sensor array
Fig.1 Neuromag Ltd.122
MEG system
Arrays of gradiometer dc SQUID detectors are
contained within a helmet surrounded by a liquid
helium reservoir for cooling
Fig. MRI scan of a human scull

5. Uses of SC magnets

6. Pirelli Cables & Systems
Transmission Lines
15% of generated electricity is dissipated in transmission lines
Potential 100-fold increase in capacity
BNL Prototype: 1000 MW transported in a diameter of 40 cm
Pirelli Cables & Systems

7. Conductus Clearsite system
Telecommunications
Superconductors are used as efficient filters in cellular telephone towers (now 700 worldwide)
Separate signals of individual phone calls.
Because of electrical resistance, conventional interference filters eat away part of the signal.
Conductus Clearsite system

8. Superconducting magnets
An electrical current in a wire creates a magnetic field around a wire. The strength of the magnetic field increases as the current in a wire increases. Because SCs are able to carry large currents without loss of energy, they are well suited for making strong magnets. When a SC is cooled below its Tc and a magnetic field is increased around it, the magnetic field remains around the SC. If the magnetic field is increased to a critical value Hc the SC will turn normal.
A typical Nb3Sn SC magnet.
It produces 10.8T with a current
of 146A. Bore diameter is 3.8 cm.
Support a very high current density with a very small resistance
A magnet can be operated for days or even months at nearly constant field
Cross-section of multifilament
Nb-Ti of 1mm overall diameter,
consisting from mm
filaments

9. Other Uses of Superconductivity
Fault current limiters
Electric motors
Electric generators
Petaflop computers (thousand trillion floating point operations per second)

10. Applications of Superconductivity
Trade off between:
Cost Saving and Cost Increase
Zero resistance, no energy lost, novel uses…
Need refrigeration, fabrication costs….

11. High-Tc Superconductivity
Paul Chu
164 K
Alex Müller and Georg Bednorz

12. 373 K,BP of water
295 K,room temp
273 K,FP of water
138 K,Highest Tc for HgBaCaCuO
77 K,Liquid Nitrogen
4.2 K,Liquid Helium

13. K.A. Muller J. G. Bednorz
The Discovery of superconductivity in ceramic materials
The Nobel Prize in Physics 1987