june 1, 2014 multipole for uniformity control of ribbon ion beam nick white

April 10, 2023

Multipole for uniformity control of ribbon ion beam

Nick White

April 10, 2023

Uniformity Control Concept

Steel

Coils

Ion Beamtravel

US Patent 7,078,713

April 10, 2023

Operation of Multipole

• The following pictures show the effect of adjusting a single pair of coils

• Note how the beam that passes between these coils is compressed in one direction and expanded in the other

• The current density in the rest of the beam is unaffected– But there is a slight correctable change in

beam overall width

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Operation (cont)• The following sequence shows the effect of this

adjustment on the beam current profile along the longer beam dimension

• The beam is shown with its density profile overlaid.

• Note that the profile scale changes. It is linked to the highest density present– The current density at the sides of the beam is

not changing

• The process is entirely linear (unlike the VIISta-80)

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Beam is initially non-uniform

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Beam is tuned for best uniformity