Source of Negative Ions by Cesium Sputtering (SNICS)


Product Features
  • The SNICS II is capable of creating over 60 different types of Negative Ion Beams.
  • Lifetime is 3-6 months between source maintance, except for cathode change
  • Cathode change time is within 10 minutes from beam on target to beam on target

Applications
The SNICS II is the most versatile negative ion source presently available. This sputter cathode source produces ion beams for all elements that form a stable negative ion. Its unique design and metal/ceramic construction with no organic seals in the main housing of the source has produced a reliable system with superior performance for all negative ions across the periodic table.

Design
diagram of SNICS internal components
Cesium vapor flows from the cesium oven into an enclosed area between the cooled cathode and the heated ionizing surface.  Some of the cesium condenses on the front of the cathode and some of the cesium is ionized by the hot surface.  The ionized cesium accelerates toward the cathode and is focused on the front face of the cathode.  The ionized cesium sputters particles from the cathode through a condensed cesium layer on the cathode face.  In this way, negative ions are accelerated from the cathode surface.

The source is designed to allow the change of a cathode with minimal downtime.  In Pelletron systems, it is common to change a cathode within 10 minutes from beam on target to beam on target.

Performance
Customers report emittances of the resulting negative ion beam from a SNICS II source from 3-5 πmm mR (MeV)1/2 for 80% of the beam, depending upon the beam mass.

Some Negative Ion Beams Produced by SNICS II

 Negative Ion Current after Analysis (μA) Negative Ion Current after Analysis (μA)
 H 130 Br 60
 D  150  Zr  9.4
 Li  4  Mo  5
BeO  10  Ag  13
B2  73  I  220
C  260  Ta  9.5
CN  12  W  2.5
O  300  Au  150
Na  4  Cl  100
Al2  50  Fe  20
Si  430  Cu  160

This list is based on data from AT&T Bell Laboratories, the NEC test bench, and other contributing laboratories. All ion beam currents listed are measured after 30° or 45° mass analysis.

For a more complete list please reference the Related Documents section below

Options
Though the source is primarily designed for the use of solid samples, NEC offers a gas cathode assembly, which allows the insertion of gas through the center of a cathode.

NEC also offers a similar source that can handle multiple cathodes – 40 or 134 cathodes.  For more information on this source, please see our MC-SNICS source page.


Related Documents
SNICS v1.pdf