Effect of Biased Electrode to High Energetic Electrons in Plasma of RIKEN18 GHz ECRIS

Kidera M., Higurashi Y.*, Nakagawa T., Biri S.**, Shirkov G.***, Miyazawa Y., Hemmi M., Chiba T., Kase M., Kageyama T., Goto A., Yano Y.,
The Institute of Physical and Chemical Research (RIKEN), Japan
*College of Science, Rikkyo University, Japan
**ATOMKI, Hungary
***Dubna, Russia

To obtain higher beam intensities in ECR ion sources many laboratories have made efforts by using various methods. One of these methods is to install a biased or floating electrode into the plasma chamber of the ion source. In spite of the great success of this method, the mechanism is still not completely clear. Very recently, we found that the beam intensities of highly charged ions are strongly dependent on the position of electrode, bias voltage, and size of electrode. When the electrode is placed near the RF injection side, we do not need the bias voltage to increase the beam intensity and the beam intensity decreases with increasing the bias voltage. Near the resonance zone, the beam intensity increases with increasing the bias voltage.

To understand these phenomena, we measured the bremsstrahlung X-ray and beam intensity of highly charged Xe ions from RIKEN 18 GHz electron cyclotron resonance ion source as a function of negative bias voltage and position of electrode systematically. We observed that yield of high energetic X-ray, slope of energy spectra and beam intensity of charged ions are strongly dependant on the negative bias voltage of electrode. From these results, we found that the electrode works to change the plasma potential when the electrode is placed near the RF injection side. Near the resonance zone, the electrode works to increase the electron density.

In this contribution we present the results of X-ray measurement in detail and discuss the effect of electrode from out experimental results.

Presenting Author : Kidera M.
Presentation : Oral
Tuesday 12:00