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Electrode activation in cesium-free negative ion sources
Vadim Dudnikov1, Rolland P Johnson
1Muons, Inc., Batavia, Illinois 60510, USA. dvg43@yahoo.com
The Review of Scientific Instruments
|March 3, 2010
Summary
Negative ion emission is significantly enhanced in cesium-free discharges through electrode activation. This process involves heating and impurity accumulation, reducing work function and boosting ion output, similar to cesiation.
Area of Science:
- Plasma Physics
- Surface Science
- Ion Source Technology
Background:
- Cesium-free discharges are crucial for specific ion source applications.
- Enhancing negative ion emission is a key challenge in plasma and ion source research.
- Existing methods like cesiation have limitations, necessitating alternative approaches.
Purpose of the Study:
- To investigate electrode activation methods for enhancing negative ion emission in cesium-free discharges.
- To elucidate the underlying physical mechanisms responsible for the observed emission enhancement.
- To establish the importance of monitoring work function and impurity concentration during activation.
Main Methods:
- Utilizing discharge plasma to strongly heat a negatively biased emission electrode.
- Analyzing the accumulation of low-ionization-potential impurities on the electrode surface.
- Observing the correlation between impurity accumulation, work function changes, and negative ion emission.
Main Results:
- Significant increase in negative ion emission observed following electrode activation.
- Electrode activation leads to accumulation of impurities, lowering the surface work function.
- The observed enhancement mechanism is analogous to "Cesiation" but in a cesium-free environment.
- Negative biasing of the emission surface is critical for impurity accumulation and trapping.
Conclusions:
- Electrode activation is an effective strategy for enhancing negative ion emission in cesium-free discharges.
- The mechanism involves impurity accumulation and work function reduction, mimicking cesiation.
- Direct detection of work function and impurity concentration is vital for controlling the activation process.
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