* according to Marc, there is no contraindications to use 3.4 mm diameter rods, that fit in the GEM support structure holes, for the rings. The rings could be between 7 and 8 mm wide. The spacer will need to be chosen carfully: presumably they should have 6.35 mm outer diameter.
* Steven will check with Sven if there is contraindication
* Steven will also estimate from first principal the alpha rate coming from the copper ring
Igal.