This document discusses the Josephson Effect through the theory of Cooper pair tunneling in superconductors. It describes the experimental setup used to study the effect, including a cryostat, temperature probe, and bipolar current source. The document analyzes data collected from two niobium junction arrays, finding that the critical currents matched predictions from BCS theory for the superconducting energy gap of niobium.

1. The DC Josephson Effect
By Jackson Cummings

2. Background
• Josephson Effect
• BCS Theory
• Cooper Pairs
• Brian Josephson
• Cooper Pair Tunneling

3. Theory
2 1( ) sin( )cI t I   

4. Apparatus
Cryostat Setup
Temperature Probe

5. Bipolar Current Source
BNC Router Box

6. Schematic

7. Junction 1 Data
= 12.06 ± 2.12 μA = .25 ± .03 V

8. Junction 2 Data
= 16.15 ± 2.03μA = .25 ± .03 V

9. Analysis
Using the equation for band gap energy of niobium from
BCS theory:
= .0019 eV
Our data:
= .005 ± .0006 eV
= 16.15 ± 2.13μA
= 12.06 ± 2.02 μA
Critical Currents for
Junctions arrays 1 and 2

10. Questions?