Mike,

 

I took a look at Tom’s Coil Set (aka 72 Coil Set) which has some attractions such as just 2 types of coils and is designable/achievable. I went thru a similar study as before, choosing subsets of these coils to measure their effectiveness and current demands. The results are in the attached spreadsheet.

 

The results shown are only the best cases found using stellarator symmetric groups (ie each group contains 6 coils) . The 2,3,4 and 5 group subsets (containing 12, 18, 24 & 30 total coils respectively) all provide good reduction in islands from what would be 22% total islands at the 95% level for 1.5 mm tolerance (0.060”) if uncorrected. They differ in the max current they require to achieve this ranging from 80 KAT if only 12 coils are used down to less than 15 KAT if all of them are used.

 

I also looked at expanding toroidally the best 24 coil subset which straddles the two  symmetry planes. If we triple the size of these coils, effectively providing full toroidal coverage as with the 72 coil set, we maintain the same level of correction but significantly reduce Max Currents required  down to less than 13 KAT for 1.5 mm tolerance.

 

There may be some assembly issues with coils straddling the symmetry planes, particularly at the C-C interface, but I think its worth due consideration.

 

Art

 

 

 

 

 

 

 

 

 

Art – View this email in HTML mode.  The attached IGS file is curves on the centerline of two of the trim coils.  Does this provide the information that you need or is there a better form to give you?  I haven’t heard from Mike Z indicating that this arrangement is of interest to him.  

 

Tom

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Tom Brown, PPPL

Phone: 609-243-2156

E-mail: tbrown@pppl.gov