Source of Negative Ions by Cesium Sputtering (SNICS)

The NEC SNICS II (Source of Negative Ions by Cesium Sputtering) generates ion beams by accelerating cesium ions onto a sample target (cathode), which sputters out negative particles from the sample. Contact us to learn more.
 
The unique design of NEC’s SNICS II – including a metal/ceramic construction with no organic seals in the main housing of the source – has produced a reliable system with superior performance. The SNICS II sputter cathode source is the most versatile negative ion source presently available, producing ion beams for all elements that form a stable negative ion.

 

Application

NEC manufactures negative ion sources for a variety of applications. SNICS II is designed as a heavy-ion source and is used in diverse applications, including ion implantation and damage studies. There are now over 100 SNICS II ion sources in use on Pelletron® accelerators and other tandem accelerators throughout the world.

 

How It Works

• Cesium vapor flows from the cesium oven into an enclosed area between the cooled cathode and the heated 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.

 

SNICS Design

The SNICS II has multiple design considerations that allow it to maximize beam production.

• All-metal sealed main housing

The SNICS II has an all-metal sealed main housing. The only o-rings are in the back of the cooled area on the cathode holder. This arrangement allows the body of the source to remain warm relative to the cathode.

• Enclosed volume

The volume around the ionizer and cathode is fully enclosed, which keeps the cesium vapor in the volume.

• Adjustable cathode position

Provisions are available to adjust the cathode insertion position while the source is running, optimizing beam current. Adjusting the cathode position can also allow longer runs on a single cathode by optimizing the amount of material used per run.

 

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 multi-cathode SNICS (MC-SNICS) that can handle either 40 or 134 samples at a time.

 

 
 

Configurations

A typical 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 SNICS injector systems.
 

SNICS Performance

The maintenance period of the SNICS II is dependent on beam type and beam current produced. However, customers reported 3-6 months between source maintenance, except for cathode change. This translates into well over 1000 hours of beam production time.
 
The lifetime of a cathode is highly dependent on the sputter rates. However, the source is designed to allow the change of a cathode without turning the source off. In Pelletron® systems, it is common to change a cathode within 10 minutes from beam on target to beam on target.
 
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.
 
 

Examples of 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

Related Documents

SNICS