Paper 1.12: "Large Storage Box Hydrogen Maser," E. E. Uzgiris and N. F. Ramsey, IEEE J. Quantum Electron. QE-4, 563–568 (1968).

Since the principal disadvantage of the hydrogen maser is the small frequency shift introduced by collisions with the walls of the storage bottle, I realized that this shift could be reduced by a factor of ten by making the storage vessel ten times larger in diameter. Superficially, this appears to be impossible since the 21 cm wavelength of the radiation would be smaller than the 150 cm diameter of such a bottle and the phases inside the container would be mixed if the radiation were present throughout the chamber. However, in Paper 1.7, I had shown that a sharp resonance could be obtained even if the oscillatory field region were confined to a small part of the container provided the atoms could randomly move between the two regions. My graduate student E. E. Uzgiris and I then successfully built such a maser. This was the first experimental demonstration of the randomly successive coherent oscillatory field method described in Paper 1.7. We gave a more detailed description of the apparatus and the results in Phys. Rev. A1, 429–446 (1970).