Emittance measurement of highly charged ion beams extracted from ECR ion source using electric sweep scanner

We have designed and built an emittance scanner which was installed at the beam line LECR3 of the heavy Ion Accelerator Facility in Lanzhou. The scanner measures the emittance of beams from the ECR ion source by the electric-sweep method, named as Electric-Sweep Scanner(ESS). From analyzing the measured results we found it is contrary to the behavior expected from normal theory of ECR plasma. Typical results are as follows: when the extracted voltage is 15.97kV, total current is 190muA, the horizontal and vertical emittance of O4+ are 137pimm.mrad and 120pimm.mrad respectively.