There is a much simpler way of doing the same thing. Even the Japanese don't understand Leif Holmlid's or @Wyttenbach's physics for producing Rydberg matter in a simple six inch cube.
I am not sure it requires different ways. Maybe the involved Japanese researchers are not aware UDD/UDD may be formed in these multi-layer metal layers (optionally catalyzed by CaO). Francesco Celani is aware but not convinced from my observations.