Presentation on theme: "Ion Source Modelling and Field Index Improvements by Scott Lawrie."— Presentation transcript:
Ion Source Modelling and Field Index Improvements by Scott Lawrie
Current goals Decrease emittance of beam Study the influence of the sector magnet Confirm field index, n = 1 Widen magnet poles Find optimum pole separation and angle Plot good field region Make improved poles and test them …Then move on to the extractor!
Pole piece close-up Angle of Pole-face Pole Width Spacer Thickness Shim Width Shim Height Maximum pole width = 74mm (ISIS standard = 50mm). Allows 1.5mm clearance from bottom of cold box. Centre of pole face; used to measure separation of poles
Comparison of magnetic fields 8.88 ° faces, 24.00mm separation 7.00° faces, 19.16mm separation
Calculating the field index Sum up the z-components along curve Multiply by angle difference integral
Field index of ISIS dipoles Pole pieces separated by 25mm, with face angles of 8.88°
How the field index varies with pole separation Optimum pole separation = 28.6 mm
How the shape of the field index varies Pole face angle Separation of poles modified to give an n = 1 field at R = 80 for each angle. 7 degree poles couldn’t be squeezed close enough together without hitting the extract.