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Abstract The impact of the double frequency heating (DFH) physics on the performance of Electron Cyclotron Resonance Ion Sources (ECRIS) has been investigated by studying the correlation between the two RF-frequencies, injected into the plasma of an ECRIS operated in DFH mode by measuring extracted currents of highly charged Argon ions from the Frankfurt 14 GHz-ECRIS as a function of the relative sharing of the total injected power. In order to study the influence of the plasma physics, the effectivity of DFH as a function of the plasma–electron–densityand -energy, a second series of measurements has been carried out, where the ECRIS was run in an enhanced configuration with plasma parameters, where plasma–electron–density and -energy were close to values typical for a more performant (e.g. 18 GHz) source. The measurements demonstrate the positive impact of the DFH physics particularly for the creation of very high charge states also and in particular for high performing sources in modern accelerator installations. [ABSTRACT FROM AUTHOR]

A study dedicated to enhance the performance of the volume effect in double-frequency heating (DFH) has been carried at the Frankfurt 14-GHz ECRIS of the Institut für Kernphysik, Goethe University Frankfurt, Germany. For this purpose, the electron density and temperature of the plasma have been enhanced by applying the established MD method developed by the authors. In addition to the standard RF frequency (14.3 GHz) injected from a klystron transmitter, a second RF frequency has been injected into the plasma chamber of the ECRIS via the second waveguide from a TWT transmitter, allowing variation of the injected frequency in the range between 13 and 15 GHz. A frequency gap of 800 MHz with almost overlapping resonance zones has been used in contrast to the minimum gap width of 1.5 GHz usually used in DFH. Applying the MD method permitted the increase in the intensity of the extracted Ar14+ ion beam by a factor of 5 by adding a 150-W RF power from the TWT to the basic injection of 700 W from the klystron, a value that clearly exceeds enhancements that have been measured in earlier experiments with the DFH having two well separated resonance zones. [ABSTRACT FROM PUBLISHER]

Charge diffusion in an electron cyclotron resonance ion source (ECRIS) discharge is usually characterized by nonambipolar behavior. While the ions are transported to the radial walls, electrons are lost axially from the magnetic trap. Global neutrality is maintained via compensating currents in the conducting walls of the vacuum chamber. It is assumed that this behavior reduces the ion breeding times compared to a truly ambipolar plasma. We have carried out a series of dedicated experiments in which the ambipolarity of the ECRIS plasma was influenced by inserting special metal-dielectric structures (MD layers) into the plasma chamber of the Frankfurt 14 GHz ECRIS. The measurements demonstrate the positive influence on the source performance when the ECR plasma is changed toward more ambipolar behavior. [ABSTRACT FROM AUTHOR]