Lab Course: Ion Sources

Larry LammResearch Professor

Technical Director of the NSLWinter 2008

Accelerators in the lab

• Van de Graaff accelerators– KN (3.7 MV) and JN (1.5 MV) are “single-

ended”, meaning the ion source is inside the terminal, producing positively charged beams.

– FN (10.6 MV) is a “tandem” accelerator, with the terminal electrode in the center of the accelerator, requiring negatively charged beams external to the accelerator.

AcceleratorsFN (10.6 MV)

KN (3.7 MV) JN (1.5 MV)

Helium Ion Source (HIS)

• Produces negatively charged 3He and 4He beams for injection into the FN Tandem Van de Graaff accelerator.

• The heart of the HIS helium ion source is the duoplasmatron, manufactured by Peabody Scientific. The details of ion beam production within the duoplasmatron are a bit complicated, but the basic idea can be simply described.

Helium Ion Source (HIS)

Helium Ion Source• Filament

Legs (Ni) used to supply high current (60A) to Filament (W)

Filament Legs (Ni)

Filament (W)

Helium Ion Source• The

filament is surrounded by low pressure helium gas (3He or 4He)

Low Pressure Gas (He)

Helium Ion Source• The

filament glows white hot, emitting electrons which ionize the helium gas.

Filament (W)

Helium Ion Source• Solenoidal

magnet field helps focus electrons to enhance the plasma production.

Solenoid Magnet

Helium Ion Source• Positively

charged helium ions are “pulled”out of the source through a small aperture.

Beam Aperture