1. New Generation Nuclear Microprobe Systems: A new look at old problems By David N. Jamieson Microanalytical Research Centre School of Physics University of Melbourne Parkville, 3010 AUSTRALIA 7 th International Conference on Nuclear Microprobe Technology and Applications, Cité Mondiale, Bordeaux, France, September 11 2000

2. © David N. Jamieson 1999 Electron Emission from Surfaces CVD B-doped diamond films are electrically conductive Diamond has a negative electron affinity Potential applications as a cold cathode electron emitter Measure  : number of electrons emitted from surface per ion impact Measure  =15 to 30 (metals:  = 1.5) H H H electrons Incident ion + – I–I– H H H electrons Incident ion + – I+I+ 50  m Yield max min RBS I–I–

3. © David N. Jamieson 1999 Filiform Corrosion in Aluminium 200  m Yield max min Anticorrosion layer removed Filiform growth C - RBS Al - RBS He Cl - PIXE O - RBS Al - RBS Cl growth head Filiforms grow under breaches in the anticorrosion coating on Al 3 MeV H PIXE data confirms role of Cl in catalysing growth of the filiform

4. © David N. Jamieson 1999 Menke’s Syndrome revisited Menke’s Syndrome is a Cu deficency genetic disorder. The gene responsible for the disorder has now been mapped. Pathways for Cu metabolism within cells can now be controlled and studied with unprecedented precsion. But can the nuclear microprobe cope? Need to resolve Cu distributions within single cells to a spatial resolution of sub-micron. Images here are by indirect immunofluorescence from anti- body labelled Menkes protein. Cells are less than 10 micons in width

5. © David N. Jamieson 1999 Outline The quest for superior spatial resolution in the Nuclear Microprobe: Why has the probe resolution stalled at 1 micron for 2 decades? Some new insights provide possible pathways to future progress Introduction to elementary ion optics –Chromatic aberration - not a problem? –Spherical aberration - not too much of a problem? –Stray magnetic fields - definitely a problem –Demagnification - the way forward –Ion source brightness - small advances to be welcomed A review of the next generation systems Conclusion (Topics not addressed: –High efficiency detectors, fast DAQ’s to handle high intensity beams, –specimen damage,channeling convergence angle)

6. © David N. Jamieson 1999 1  m wall Chip feature size and NMP resolution Size (micron) Year Moore’s Law <1 pA 8086 80386 P5 P6 P7 >100 pA

7. © David N. Jamieson 1999 1  m wall Spatial Resolution Required: Applications published at the Last Conference 1998 “Pile up”

8. © David N. Jamieson 1999 Image Plane Introductory Ion Optics x i = (x/x)x o + (x/  )  o + (x/  )  o  o + (x/  )  o 3 + (x/   2 )  o  o 2 y i = (y/y)y o + (y/  )  o + (y/  )  o  o + (y/  )  o 3 + (y/  2  )  o 2  o 2 …plus higher order terms Object Plane Aperture Plane (x o,  o, y o,  o,  o ) (x i, y i ) Lens System Magnification (x/x)x o (y/y)y o Focusing (x/  )  o (y/  )  o Chromatic (x/  )  o  o (y/  )  o  o Spherical (x/  )  o 3 + (x/   2 )  o  o 2 (y/  )  o 3 + (y/  2  )  o 2  o 2

9. © David N. Jamieson 1999 Steps to evaluate lens system design: 1. Calculate magnification and coefficients from ion optics computer codes 2. Measure: –Beam Brightness –Chromatic momentum spread from the accelerator (use nuclear resonance) 3. Set object size so that demagnified image is equal to desired probe resolution 4. Set aperture size so that beam current is equal to desired beam current 5. Calculate aberration contribution from maximum divergence and energy spread 6. Add contributions to probe size in quadrature (or similar) 7. Spot size is now greater than desired spot size so go back to 3 and choose a smaller object size Repeat 4-7 until done. d m = 2(x/x)x o | max d c = 2(x/  )  o | max  o | max d s = 2|(x/  )  o 3 | max + |(x/   2 )  o  o 2 | max How to calculate probe resolution? d i 2 = d m 2 +d c 2 +d s 2 Wrong!!

10. © David N. Jamieson 1999 Chromatic Aberration, A closer look Singapore system achieves sub-micron probes with 15 o switcher magnet that has low energy dispersion Yet chromatic aberrations of this system should be large Skilled tuning of system is part of the answer, but not all! Maximum d c depends on getting maximum  and  in the same beam particle d c = 2(x/  )  o | max  o | max High excitation systems