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August 31, 2010

Superconducting Nanomesh Films Achieve Critical Current of 600 billion Amps per square meter, 8 to 60 times better than previous bests and will enable high performance magsails

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Nanoletters -Achieving the Theoretical Depairing Current Limit in Superconducting Nanomesh Films
This critical current level of 600 billion amps per square meter is eight times better than the best thin film and sixty times higher than previous wires. Depairing current is the theoretically maximum critical current that you can achieve on a given superconducting material as per thermodynamics without losing superconductivity).

We show the theoretical depairing current limit can be achieved in a robust fashion in highly ordered superconductor nanomesh films having spatial periodicities smaller than both the superconducting coherence length and the magnetic penetration depth. For a niobium nanomesh film with 34 nm spatial periodicity, the experimental critical current density is enhanced by more than 17 times over the continuous film and is in good agreement with the depairing limit over the entire measured temperature range. The nanomesh superconductors are also less susceptible to thermal fluctuations when compared to nanowire superconductors. Tc values similar to the bulk film are achieved, and the nanomeshes are capable of retaining superconductivity to higher fields relative to the bulk. In addition, periodic oscillations in Tc are observed as a function of field, reflecting the highly ordered nanomesh structure.

Supporting info 5 page pdf


Previous Best Critical Current

Item 2 in the above link of my status review of high temp superconductors has a graph that shows critical current for different materials at different temperatures



Superpower Inc YCBO tape plane material maintains 10 billion Amp/m^2 for a far wider range of temperatures and starts beating Niobium tin at temps over about 1.5 degrees kelvin.

Among the silver-doped films, the 5 wt% silver-doped Bi-2212 film showed highest Jc = 7.5 × 10^6 A cm−2 at 0.5 T and 5 K, which is higher than that for the undoped Bi-2212 film

7.5 x 10^10 m^2 for thin film superconductor

Critical current from a 2007 patent

The YBCO film was patterned using a wet chemical etching method. The critical current density was measured by the standard four-point method at liquid nitrogen temperature (75.5 K at Los Alamos, N. Mex.) using the 1 microvolt/cm voltage criterion. The critical current density was 2.68 MA/cm2 (Los alamos)


Nanostructured YCBO/BZO getting up to 5.2 X10^10 m^2



When we can make a lot of this Nanomesh we can have High performance Magsails

There is the possibility of a ground launched magnetic sail if we can make kilometers of the nanomesh material and not require extra weight for cooling. This critical current will enable high performance magsails for braking interstellar ships or for moving about the solar system without propellant. We jusst need a lot of it with stable performance.

31 page pdf of the 1999 Zubrin study for Nasa on magnetic sails






Getting up to 100 billion to 1 trillion or more amperes per cubic meter is the current density for high performing magnetic sails.

D.G. Andrews and R.M. Zubrin, "Magnetic Sails and Interstellar Travel." Journal of the British Interplanetary Society, 1990. The first paper published, concerned primarily with the cost savings to other propulsion systems from the use of the magsail as an interstellar brake.

R.M. Zubrin and D.G. Andrews, "Magnetic Sails and Interplanetary Travel." Journal of Spacecraft and Rockets, April 1991. The technical description and very thorough analysis of the magsail for interplanetary travel. Excellent.

R.M. Zubrin, "The Magnetic Sail." Analog Science Fiction & Fact, May 1992. A version of the above paper edited for a non-technical audience. Useful for general concepts, inadequate for a full understanding.



Magsail Mass-to-Thrust Ratio
Current capacity (amps/m^2) -- Mass in tons per ton of thrust

1 x 10^10 -- 500
3 x 10^10 -- 160
1 x 10^11 -- 50
3 x 10^11 -- 16
1 x 10^12 -- 5 
There is speculation on advanced magsail performance.
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