2D extension of gem (the generalized ecr ion source modeling code)
To model electron cyclotron resonance (ECR) ion sources, GEM [1] is being extended to two dimensions (2D) by adding a radial dimension. The electron distribution function (EDF) is calculated on each magnetic flux surface using a bounce-averaged Fokker-Planck code with a 2D ECR heating (ECRH) model. The ion fluid model is also being extended to 2D by adding collisional radial transport terms. All species in ECRIS are balanced by assuming quasi-neutrality in each cell and the plasma potential is calculated by maintaining the ambipolarity globally. The graphical user interface (GUI) and parallel computing ability of GEM make it an easy- to-use tool for ECRIS research. Numerical results and comparisons with experimental data are presented here.
FPPAC94: A two-dimensional multispecies nonlinear Fokker-Planck package for UNIX systems☆
Abstract FPPAC94 solves the complete nonlinear multispecies Fokker-Planck collison operator for a plasma in two-dimensional velocity space. The operator is expressed in terms of spherical coordinates (speed and pitch angle) under the assumption of azimuthal symmetry. Provision is made for additional physics contributions (e.g. rf heating, electric field acceleration). The charged species, referred to as general species, are assumed to be in the presence of an arbitrary number of fixed Maxwellian species. The electrons may be treated either as one of these Maxwellian species or as a general species. Coulomb interactions among all charged species are considered This program is a new version of FPPAC. FPPAC was last published in Computer Physics Communications in 1988. This new version is identical in scope to the previous version. However, it is written in standard Fortran 77 and is able to execute on a variety of Unix systems. The code has been tested on the Cray-C90, HP-755 and Sun Sparc-1. The answers agree on all platforms where the code has been tested. The test problems are the same as those provided in 1988. This version also corrects a bug in the 1988 version.
REXEBIS operation and developments
At REX-ISOLDE at CERN a unique combination of a Penning trap and an electron beam ion source for the bunching and charge breeding of radioactive ions prior to their acceleration has been put into operation. The task of REXEBIS is to increase the charge state of injected singly charged radioactive ions to a mass to charge ratio A/q<4.5. This enables an efficient acceleration in the following LINAC. Even without optimizing every part a total efficiency of up to 4% for Na ions including the efficiency of the trap and the accelerator could be achieved and the system has been operated reliable and stable for several weeks of beam time. For the EBIS alone the efficiency for the charge breeding in a single state has been determined to be around 10% for elements between Li and Sm and average ion currents of a few pA.