Cavity fields principal resonance

The experimental arrangement of the Yale experiment is shown in Fig. 3. A Na positron source of about 15 mCi is placed inside a microwave cavity resonant in the TMno mode at 2.323 GHz and filled with N2 gas to a pressure between 0.25 and 3 atm. Eight Nal(Tl) detectors count in coincidence 0.5 MeV annihilation y rays emitted at 180°. The magnetic field of about 8 kG is varied across the resonance line as indicated in Fig. 4. The signal is the increase in Ps(2y) rate, and the linewidth is determined principally by the lifetime of the M=0 triplet state. 

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