Toroidal Volume Ion Source (TORVIS)


Product Features
  • NEC’s highest current source for H and He
  • Stable, easy to operate source that works well over a wide range of conditions

Applications
The NEC Toroidal Volume Ion Source (TORVIS) is our highest current source for negative ions of hydrogen, deuterium, and helium.  It is designed for efficient injection into tandem electrostatic accelerators.

Design
The TORVIS is a high current H/He ion source with a toroidal discharge chamber.  Negative protons are directly extracted from the source.  For negative helium production, a rubidium vapor charge exchange cell is used.

The TORVIS is a compact vacuum chamber that is completely surrounded by small permanent magnets arranged to create a surface of magnet cusps.  These cusps serve to mirror the ions and electrons away from the walls of the chamber.

A central magnet is placed on the back plate of the ion source directly opposite the beam exit aperture.  This produces a conical region containing slow electrons.  The fast electrons are filtered out of this volume, reducing destruction of the negative ion.

Options
A TORVIS injector system can be set up in three (3) different ways:

Performance

Injector Current*
H only version 400μA H (200μA D)
He only version 20μA He
H and He version 100μA H, 20μA He (50μA D)

*measured after mass analysis. Test beam currents are conservative with emittance for efficient transmission through tandem electrostatic accelerator


Related Documents
TORVIS v1.pdf
Paper presented at 2005 IBA conference