Jan Mulder

Optimization of a charge-state analyzer for electron cyclotron resonance ion source beams

A detailed experimental and simulation study of the extraction of a 24 keV He-ion beam from an ECR ion source and the subsequent beam transport through an analyzing magnet is presented. We find that such a slow ion beam is very sensitive to space-charge forces, but also that the neutralization of the beams space charge by secondary electrons is virtually complete for beam currents up to at least 0.5 mA. The beam emittance directly behind the extraction system is 65 pi mm mrad and is determined by the fact that the ion beam is extracted in the strong magnetic fringe field of the ion source. The relatively large emittance of the beam and its non-paraxiality lead, in combination with a relatively small magnet gap, to significant beam losses and a five-fold increase of the effective beam emittance during its transport through the analyzing magnet. The calculated beam profile and phase-space distributions in the image plane of the analyzing magnet agree well with measurements. The kinematic and magnet aberrations have been studied using the calculated second-order transfer map of the analyzing magnet, with which we can reproduce the phase-space distributions of the ion beam behind the analyzing magnet. Using the transfer map and trajectory calculations we have worked out an aberration compensation scheme based on the addition of compensating hexapole components to the main dipole field by modifying the shape of the poles. The simulations predict that by compensating the kinematic and geometric aberrations in this way and enlarging the pole gap the overall beam transport efficiency can be increased from 16 to 45%.A detailed experimental and simulation study of the extraction of a 24 keV He(+) beam from an ECR ion source and the subsequent beam transport through an analyzing magnet is presented. We find that such a slow ion beam is very sensitive to space-charge forces, but also that the neutralization of the beams space charge by secondary electrons is virtually complete for beam currents up to at least 0.5 mA. The beam emittance directly behind the extraction system is 65 π mm mrad and is determined by the fact that the ion beam is extracted in the strong magnetic fringe field of the ion source. The relatively large emittance of the beam and its non-paraxiality lead, in combination with a relatively small magnet gap, to significant beam losses and a five-fold increase of the effective beam emittance during its transport through the analyzing magnet. The calculated beam profile and phase-space distributions in the image plane of the analyzing magnet agree well with measurements. The kinematic and magnet aberrations have been studied using the calculated second-order transfer map of the analyzing magnet, with which we can reproduce the phase-space distributions of the ion beam behind the analyzing magnet. Using the transfer map and trajectory calculations we have worked out an aberration compensation scheme based on the addition of compensating hexapole components to the main dipole field by modifying the shape of the poles. The simulations predict that by compensating the kinematic and geometric aberrations in this way and enlarging the pole gap the overall beam transport efficiency can be increased from 16% to 45%.

Ion source development at KVI

Ion source development at KVI is focused on increasing the beam intensity from the electron cyclotron resonance ion source injector and optimizing the beam transport and injection into the superconducting AGOR cyclotron. We describe several modifications that have resulted in a significant performance increase of the ion source. We also present the first results of ion transport simulations that have been performed to better understand beam losses in the extraction region and in the low-energy beam transport system. Finally, a new emittance meter based on a combination of the pepperpot and scanning techniques will be described, which will be used to benchmark the simulation studies of ion extraction and transport in detail.

Design and Calculations for the New ECRIS at KVI

In this paper a brief description is given of the on‐going upgrade of the CAPRICE‐type ECRIS injector of the K=600 AGOR cyclotron at KVI. This upgrade is motivated by the new TRIμP program, which requires a significant increase of available beam intensity by up to two orders in magnitude. The upgrade follows the AECR design of the university of Jyvaskyla, which was originally pioneered at LBNL (USA). We will discuss the mechanical design and magnetic field calculations of the solenoidal and the permanent magnetic hexapole fields.