Multi-Cathode Source of Negative Ions by Cesium Sputtering (MC-SNICS)

40 MC-SNICS mounted on sliding supports

40 MC-SNICS on sliding support with control rods

40 MC-SNICS in safety cage with control rods

134 MC-SNICS mounted in isolation deck

134 position cathode wheel mounted on source

40 position cathode wheel

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Product Features

• The MC-SNICS is capable of creating all negative ions across the periodic table except noble gases.
• Sources typically function on the order of 1,000 cathodes before requiring maintenance, except for cathode wheel change.
• Cathode wheel change time is within one hour from beam on target to beam on target.
• Indexing system is capable of reproducing cathode position to within 0.05 mm of original position.
• Allows repeat measurements within a batch of cathodes in any sequence.

Contact us to learn more and start an order

The NEC MC-SNICS (Multi-Cathode Source of Negative Ions by Cesium Sputtering) is most commonly used in Accelerator Mass Spectrometry (AMS) systems to generate negative ions. Contact us to learn more.

Applications

NEC manufactures negative ion sources for a variety of applications. We originally developed the Multi-Cathode Source of Negative Ions by Cesium Sputtering (MC-SNICS) as a reliable sputter source. This source specifically targeted applications that required rapid cathode change and precise, repeatable positioning without cathode exposure to air. This source is most commonly used in AMS systems for the production of beams such as C, Be, I, Ca, Cl, and the actinides. Like the SNICS, it can create ion beams from all elements that form a stable negative ion.

How It Works

The MC-SNICS principle of operation is very similar to the single cathode SNICS source, with the exception of using a spherical ionizer instead of a conically shaped ionizer. Here’s how it works.

• Cesium vapor flows from the cesium oven into an enclosed area between the cooled cathode and the heated spherical ionizing surface.
• Most of the cesium is ionized by the hot surface, while some of the cesium condenses on the front of the cathode.
• The ionized cesium sputters particles from the cathode through a condensed cesium layer on the cathode face.
• Negative ions are propelled near the cathode surface and then accelerated back toward the ionizer.

MC-SNICS Design

The MC-SNICS uses the basic elements from the SNICS II ion source. A cathode indexing system adds to the source to allow the change of cathodes without breaking vacuum. The indexing system features:

• Ferrofluidic rotating seal
• Pneumatically driven indexing mechanism with bidirectional indexing
• Bidirectional indexing
• Various cathode wheel sizes and materials

Options

There are two models of the MC-SNICS:

40 MC-SNICS

• Includes an indexing system that is compatible with cathodes that can hold approximately 1 mg of sample (typical sample size for AMS).
• The standard cathode wheel can hold up to 40 cathodes at a time.
• A 20-sample cathode wheel is also available. This wheel is compatible with cathodes that can hold larger samples that can be useful for implantation or other long runs.

134 MC-SNICS

• Similar to the 40 MC-SNICS, except the standard 1 mg sample cathode wheel can hold up to 134 samples at a time.
• The larger sample cathode wheel can hold up to 67 cathodes at a time.

Though the MC-SNICS source is primarily designed for the use of solid samples, NEC offers a gas option that allows the input of carbon dioxide behind a hollow titanium cathode assembly. This is available for both the 40 MC-SNICS and 134 MC-SNICS models.

Configurations

A typical MC-SNICS system includes:

• The source
• Extractor/einzel lens
• A cooling system
• Power supplies

NEC can provide just the source, a complete injector system, or anything in-between. Contact NEC for more information on MC-SNICS injector systems.

Accessories

NEC also offers manual and electric cathode presses to pack powdered elemental samples into cathodes suitable to generate negative ion beams. Contact NEC for more information.

MC-SNICS Performance

The beam emittance is on the order of 5 πmm mR (MeV)1/2 for optimum transmission through a tandem electrostatic accelerator with proper optics.

Examples of Negative Ion Beams Produced by the MC-SNICS

Negative Ion	Current after analysis
Carbon	>100μA
Aluminum	>200nA
Beryllium	>1.5μA
Iodine	~1μA
Chlorine	30μA
Calcium	80nA

This list is based on data from the NEC factory and contributing laboratories. All ion beam currents listed are measured after 30° or 45° mass analysis.

This is not a complete list of beams that can be produced by the MC-SNICS source. For beam current information for other elements, please contact NEC.

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