MgB Advances

MSimon · Post by **MSimon** » Mon Sep 26, 2011 7:29 am

http://iopscience.iop.org/0953-2048/24/ ... 105005.pdf

Abstract
MgB2 tapes were fabricated by the in situ powder-in-tube method using C2H4O3-treated B powder as a source material. It is found that the Jc values of MgB2 tapes are significantly improved by treating B powder with C2H4O3. At 4.2K, the Jc of the C2H4O3-treated sample sintered at 800 ◦C reaches 5 × 10^3 A cm−2 at 12 T. The C2H4O3-treated B improves not only the upper critical field through enhancing intraband scattering but also the flux pinning by increasing grain boundaries and C substitution effects. A larger amount of intragranular structural defects and grain boundaries were found in the C2H4O3-treated MgB2 matrix. Benefiting from the good crystallinity, the C2H4O3-treated tape sintered at 800 ◦C shows a bigger active area fraction and a higher Jc than the sample sintered at 700 ◦C. These results suggest that treating B powder with C2H4O3 is an effective way to enhance the critical current density of MgB2 superconductors.

ChengduoWang1, YanweiMa1, Xianping Zhang1,
Dongliang Wang1, Zhaoshun Gao1, Chao Yao1, Satoshi Awaji2 and
KazuoWatanabe2
1 Key Laboratory of Applied Superconductivity, Institute of Electrical Engineering,
Chinese Academy of Sciences, PO Box 2703, Beijing 100080, People’s Republic of China
2 High Field Laboratory for SuperconductingMaterials, Institute for Materials Research,
Tohoku University, Sendai 980-8577, Japan

MSimon · Post by **MSimon** » Mon Sep 26, 2011 7:30 am

Give me a shout if you can't pick the pdf up on line.

mvanwink5 · Post by **mvanwink5** » Tue Sep 27, 2011 12:15 pm

MSimon,
Would you care to translate the MgB2 production process improvements on a polywell design, specifically, the B field, coolant type, and coil size for a 100 MW net P-B machine. I suspect you have a model and have plugged those numbers in already.

Best regards and thanks for the consideration...

Giorgio · Post by **Giorgio** » Tue Sep 27, 2011 3:42 pm

Nice paper Msimon, thanks.

I found the result extremely interesting, especially Figure 3 that clearly shows as the new treatment flattens the influence of the magnetic field.
Quite a result IMHO!

MSimon · Post by **MSimon** » Wed Sep 28, 2011 3:02 am

mvanwink5 wrote:MSimon,
Would you care to translate the MgB2 production process improvements on a polywell design, specifically, the B field, coolant type, and coil size for a 100 MW net P-B machine. I suspect you have a model and have plugged those numbers in already. :cool:
Best regards and thanks for the consideration...

I haven't worked the spread sheets for about a year. But let me give you what I remember. A 10T machine was envisioned by Nebel and company with a diameter on the order of 20 meters. Or maybe it was 10 m I'd have to look it up. Small compared to a tok but still. If the field could be raised to 15 T the size went down to about 1 or 3 m.

And if you know the scaling laws it turns out the smaller you can make the coils at a certain intrinsic field level the more power you can get out (linear inverse scaling vs diameter). The big deal for this new material is not so much field strength but the amps per cm^2 the wire can carry at a given field strength. IIRC 1E3 Amps per cm^2 was very desirable. MgB back then was 1/2 or 1/4 of that number making the machines large in order to get enough amp turns.

If things go the way they usually go in this field the wire will be commercial in about 2 years.

The big problem will be cranking in all the e-guns etc into the vacuum box. So at least as a start the size will be limited by the aux eqpt required not the coils.