1. © David N. Jamieson 1999 Modify RF Ion Source Beam from ion source emerges with low energy Gas leakage from ion source canal fills low energy end of accelerator Gas scattering degrades ion source brightness Solution: Add recirculating turbopump gas T.p. old new From the work of Roland Szymanski

2. © David N. Jamieson 1999 Modify Accelerator Column Remove corona needles and replace with resistors (Have now increased brightness by a factor of 10) So need to design a system optimised for a flux peaked beam… High demagnification!

3. © David N. Jamieson 1999 Selected new quadrupole systems 1970 Russian quadruplet D x =D y =30 1998 Leipzig separated quadruplet D x =80 D y =80 1998 CSIRO/MARC high excitation quintuplet D x =67 D y =71 1980 Oxford high excitation triplet D x =25 D y =90 2000 Oxford separated triplet D x =240 D y =50 2001 New system D x =D y =200 ?

4. © David N. Jamieson 1999 1 2 5 4 3 Strong demagnification in a long system CSIRO quintuplet system Leipzig two stage system Strong demagnification in a short system, 80 mm WD Very intense beam spot into 1  m

5. © David N. Jamieson 1999 3  m at 20 nA Resolution Versus Beam Current: CSIRO/MARC quintuplet system 1.3  m at 0.5 nA Accelerator brightness = 1.2 pA.  m -2.mrad -2.MeV -1 12.7  m 1.2  m x 0.9  m at 0.1 nA CSIRO-GEMOC Nuclear Microprobe 2.0  m at 10 nA 3100 pA/  m 2 ! 1.8  m at 8 nA 12.7  m From the work of Chris Ryan

6. © David N. Jamieson 1999 Future Developments Conclusion: To break through the 1 micron wall Install heavier magnetic shielding! But be sure to clean off DC fields (10 nT). Don’t worry about chromatic and spherical aberration, they are not a severe as first though because of flux peaking (<0.1  m) Make brighter ion sources by small tweaks, even a factor of 10 is helpful (x1/3) Install an optimised system for a strongly flux peaked accelerator, this will have a large demagnification (of necessity a high excitation system) (M -1 > 200) Need more radical lens design to reduce working distance and increase fields (40 mm) Apply the new system to some interesting problems! (< 0.1  m resolution) MP2 Bochum Leipzig Oxford triplet CSIRO 5 New Ox

7. © David N. Jamieson 1999 Spherical Aberration: A closer look The TFF model also revealed the need for careful attention to the field overlap between adjacent lenses Must have a linear field gradient as a function of beam direction to minimise aberrations Need to shape pole ends to achieve this z Pole tip ? N SN S z N N S S