An ECRIS Driven in a Single Mode Microwave Cavity with Variable Pressure

Rhode S, Ruether M., Heinen A. , Ortjohann H.W. , Vitt Ch. , and Andrae H.J.
Inst. fuer Kernphysik, Univ. Muenster, Germany

It is shown that the plasma chambers of our ECRIS I and III can be operated as single mode resonance cavities. The resonance frequency has been measured without plasma. It is reproduced with plasma via the observation of the extracted ion current of Ar6+ as function 16 Watt of MW frequency at a pressure of about 2.10-4 Pa. The presence of the plasma shifts the resonance frequency of the cavity to somewhat lower values, but the single mode resonance character of the cavity is conserved. The width of the resonance suggests that the presence of the plasma lowers the Q-value of the cavity at the pressure cited only by a factor of about two. An increase of the pressure increases the width of the resonance and thus lowers the Q-value systematically. This behavior will be correlated to the cut-off density of the plasma. On the contrary, the lowest pressure in the cavity yields the greatest electric field amplitude due to the greatest possible Q-values and may so explain the great efficiency of ECRIS at the lowest pressures.

Presenting Author : Andrae H.J.
Presentation : poster
Wednesday Poster Session at 14:45