COLD KILO-ELECTRON BALL AS PROBE FOR CHARGE-PROPORTIONAL CYCLOTRON FREQUENCY-SHIFT IN PENNING TRAP CAVITY

We report the realization of a cold (4 K), dense spherical droplet of one-component plasma made up of about 1000 electrons. This kilo-e drop let experiences a 1000-fold enlarged shift, delta(ball) of the center -of-mass cyclotron frequency due to interaction with TE(1mn) (n odd) m odes near 164 GHz in our approximate to 1 cm diam Penning trap cavity. For the first time we were able to search for this shift and obtain d elta(ball) approximate to -5 kHZ for 1000 electrons, by comparing dat a for balls of approximate to 100 and approximate to 1000 electrons. A drastic decrease of \delta(ball)\, as in 4 h a 1500e drop flattened, spread in radius from 140 to 390 mu m, and partly decoupled from the cavity modes responsible for the shift, yielded supporting evidence. T he kilo-e ball's small initial radius and slow spreading may make it u seful in other applications.