ECR Magnets

Electromagnet ECR: Most ECR sources utilize electromagnet solenoid coils. This approach allows fine-tuning of the source by adjusting the relative excitation currents in the electromagnet coils. However each Watt of power going into an electromagnet has to be removed by a separate cooling system–essentially doubling the electric power requirements for an ion source. Since ECR sources are typically mounted on a high voltage (HV) platform, the physical dimensions of that platform can become quite large and conventional electromagnets require a significant amount of power to be transmitted across the high voltage isolation system. Generally this power transmission is accomplished by either a motor-generator set with an insulating shaft connecting these components or a high-voltage isolation transformer where the secondary of the transformer is isolated from the primary (both approaches are expensive). Examples of electromagnet ECR sources are the 110 mA proton source developed at the Los Alamos National Laboratory (LANL) and ion implantation sources by Hitachi and and Varian.

Permanent magnet ECR: The current trend in industrial sources is towards permanent magnet ECR systems. This approach eliminates most of the electrical power and cooling requirements of the high voltage isolation platform. The disadvantage of this approach is that it is difficult to adjust the magnetic field profile once the source has been assembled. Hitachi is one of many companies currently developing permanent magnet ECR sources for ion implantation. Scientific Solutions developed a concept for a permanent magnet replacement for the LANL 110 mA proton source.

Superconducting magnet ECR: The current trend of high charge-state ECR souces towards ever higher operating frequencies requires the use of superconducting magnet coils because the needed current and power densities exceed the levels achievable with conventional copper coils. In addition, a number of lower-frequency ECR sources employ superconducting coils because the added complexity of the cryogenic system required for a superconducting magnet is cost-effective compared with mounting a set of water-cooled magnets on a high voltage platform. Note however that the excitation currents in superconducting magnet coils cannot be easily adjusted to fine-tune the performance of the ion source.

ECR Magnets

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