Magnetic pulsed extraction of highly charged ions from a plateau ECRIS

The afterglow is known to produce pulses of highly charged ions suited for injection to accelerator facilities. We tested a new technique of magnetic pulsed extraction (PUMAEX) in our plateau-ECR ion source PECRIS III. This source has a large resonance volume due to a homogeneous magnetic field in its center. Compared to the afterglow of PECRIS III we reached higher ion currents. The length of the PUMAEX pulses depends on the electric current pulse in the PUMAEX coil, we used pulse lengths of 0.25-1 ms. The PUMAEX coil is a small coil which is placed around the extraction hole in the plasma electrode. The absolute value of the static magnetic field near the extraction hole can be reduced below the value in the center of the source by a current pulse in the PUMAEX coil. Thus the magnetic confinement of the ECR plasma is opened specifically in the direction of the extraction hole. The plasma therefore escapes from the source more directed to the extraction hole than in the afterglow. Since the coil is very near to the location where the magnetic field is changed, it was possible to use a small coil, which could be placed in the plasma electrode of PECRIS III without major modifications. Currently we are building a new multifrequency plateau ECRIS. Using eight frequencies between 17 and 18 GHz we intend to improve the electron heating in the large resonance volume. The highest frequency will be set to the resonance frequency of cold electrons at the center of the source. The lower frequencies will match the resonance frequencies of more energetic electrons as those electrons have a greater relativistic mass. In the near future we will test the PUMAEX technique with this new source. (C) 2002 American Institute of Physics.