Crossed Field Velocity Selectors

Applications of Crossed Field Velocity Selectors

Crossed field velocity selectors provide mass and charge analysis. They can be used in high potential terminals and for analysis of exterior ion source beams.

Mass Analysis

For a fixed energy, the velocities of the different mass components are different, and only the selected mass passes undeflected.

Charge Analysis

With a beam of several charge states accelerated through a fixed potential, the velocity selector may be used to select a certain charge state.

Velocity Selector Design & Options

The electrical field is applied between two parallel plates.
The plates are supported by insulating pillars that are mounted on opposite sides of the support tube and secured to the vacuum housing end flange.
Voltage to the plates is applied through two high voltage shielded feedthroughs.
Two ceramic permanent magnets provide a uniform magnetic field at the center.
The magnets are clamped to the support tube, which is made of heavy wall rectangular steel plates.
The magnet faces are protected from sputtering by thin stainless-steel sheets.
The velocity selector is provided with field terminal plates at both ends.
The selection aperture is mounted on the support frame.

NEC offers four velocity selector options. Below are brief descriptions.

Model VS5-502	Mass-analyzes beam in the high potential terminal of an accelerator prior to acceleration Magnetic field of 1200 Gauss (fixed)
Model VS5-504	Mass-analyzes light ions for tandem accelerators Magnetic field of 1500 Gauss (fixed)
Model VS5-506	Compact version of the VS5-504 Magnetic field of 2300 Gauss (fixed)
Model VS5-508	Compact version of the VS5-502 Magnetic field of 3300 Gauss (fixed)