Emittance measurements and operation optimization for ECR ion sources

Electron Cyclotron Resonance (ECR) ion sources supply a broad range of ions for post acceleration in cyclotrons. Here, an effort to improve the beam transfer from RIKEN's 18 GHz superconducting ECR ion source (SC ECRIS) to the Low Energy Beam Transfer (LEBT) line and an optimization of the performance of the ion source is presented. Simulation studies have shown that less than 20% of the beam is currently transferred. The first goal is to measure the transverse beam emittance in real time. The emittance monitor designed and fabricated for this purpose utilizes a pepper pot plate followed by a transparent scintillator and a CMOS camera for image capture. The second goal is to investigate on dependencies between beam emittance and various operating parameters. To this extent, modifications of the ion source took place, as well as a measurement of the magnetic field inside the ion source. In this contribution the design details of the instrument and a description of the algorithm are presented as well as a typical emittance measurement

Test of the Conserved Vector Current Hypothesis by beta-ray Angular Distribution Measurement in the Mass-8 System

The beta-ray angular correlations for the spin alignments of 8Li and 8B have been observed in order to test the conserved vector current (CVC) hypothesis. The alignment correlation terms were combined with the known beta-alpha-angular correlation terms to determine all the matrix elements contributing to the correlation terms. The weak magnetism term, 7.5\pm0.2, deduced from the beta-ray correlation terms was consistent with the CVC prediction 7.3\pm0.2, deduced from the analog-gamma-decay measurement based on the CVC hypothesis. However, there was no consistent CVC prediction for the second-forbidden term associated with the weak vector current. The experimental value for the second-forbidden term was 1.0 \pm 0.3, while the CVC prediction was 0.1 \pm 0.4 or 2.1 \pm 0.5.Comment: 31 pages, 12 figures, Accepted for publication in Phys. Rev.