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Your power specification (100 W pri/200 mW sec) makes no sense. I wonder how you got there? Making a 50/60 Hz transformer with kV secondary voltage is possible of course, but toroidal design is least favourable for high voltage, I believe. I would rather expect a standard M or EI core shape. Consider proper winding insulation to handle the voltage.

We don't know the application, if it's constrained to a low frequency transformer and AC output?