Robert Clark wrote:

...
The paper by Yan et.al. discusses using a 6 kW microwave oven for
their CVD process:

Very high growth rate chemical vapor deposition of single-crystal
diamond.
PNAS | October 1, 2002 | vol. 99 | no. 20 | 12523-12525
http://www.pnas.org/cgi/content/full/99/20/12523

Using this they were able to get up to 150 micron/hour growth rates.
If the Yan et.al. process also scales linearly as other microwave CVD
methods, then a 6 megawatt microwave reactor would give a 150
millimeter/hour growth rate. So production of a 30 meter mirror would
require 30,000/150 = 200 hours, less than 9 days.
Another method would be to use several microwave ovens of the same
6kW
size used by Yan et.al. simultaneously, each working on its own seed
diamond. If we used a hundred of these we could get an equivalent
total
size of a 30 meter mirror in 90 days.
...

Correction. If several 6 kw ovens were used to make separate segments
it would take more ovens than this or a much longer time. If 900 ovens
were used, you would you get 900 segments each 1 m wide. At 150
microns/hour this would take 1000 mm/.150 mm/hr = 6667 hours, or 278
days.


Bob Clark