Practical Comparison of Two-Frequency Heating Phenomena in Different ECR Ion Sources
In order to improve highly-charged ion production from the 18GHz NIRS-HEC ECRIS, our group has studied the mixture of two microwaves of which the frequencies were close together each. Our conclusion was that when an additional microwave is added to the primary microwave, the plasma stability is improved. The output current of the highly charged ion beam was proportional to the total power of both microwaves. The dependence on the additional frequency showed the fine structure. Since this
... . Since this structure depended on the magnetic field, vacuum pressure, and so on, the precise frequency adjustment for maximum output was required under each condition. Our interest is whether the above-mentioned phenomenon can be demonstrated using a different ion source where the two frequencies are even far from each other. We installed a 17.75-18.25 GHz microwave system in addition to the 14.3 GHz klystron amplifier of the ATOMKI ECRIS. Argon output currents at various values of the microwave power and frequency were studied. The dependence on the total power shows the similar tendency as at NIRS. The dependence on the additional frequency also shows the fine structure. Detailed data will be presented.