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The CSIRO-GEMOC Nuclear Microprobe

System Overview

Lens System

Quadrupole Design

Quintuplet Configuration

Beam Shaping Controls

Scanning, Beam Deflection

Detectors

Data Acquisition and Analysis

Target Chamber





Return to NMP microanalysis

Quintuplet Lens Configuration

The novel lens configuration uses a separated quadrupole quintuplet, with a coupling of +A+A-A-A+B. The drift spaces between the first 3 quadrupoles (S12 = 0.45 m, S23 = 0.6 m) have been used to reduce spherical aberration, especially the cross-terms, increase demagnification, reduce lens excitation, and approach equal demagnification in the X and Y planes. This configuration has a demagnification of 70-90 in X and Y (depending on dift lengths) despite a short overall system length of 4.7 m, low total spherical aberration for this demagnification, and has all its significant aberration contributions concentrated into x|thetan terms.

Spaced Quintuplet configuration

The theoretical performance of this new configuration [1-3], suggests that sub-micron beam spot-sizes at 100 pA beam current can be achieved, at the low brightness of the CSIRO tandem accelerator (~1 pA.µm-2.mrad-2.MeV-1). A spot-size of 1.3 µm has been obtained at a beam current suitable for trace element work (0.5 nA). As the acceptance of the system is increased, and the beam current grows to ~20 nA, the modelling suggests a slow rate of spot-size growth with a spot size of ~3 µm possible at these high currents. This is observed in practice with the spot-size growing to 1.8 µm at 10 nA, despite the low brightness, ideal for mineralogical work.

These new quadrupole quintuplet lens systems are being manufactured by, and are available through, MARCO, Melbourne.

[1] C.G. Ryan and D.N. Jamieson, "A high performance quadrupole quintuplet lens system for the CSIRO-GEMOC Nuclear Microprobe", Nucl. Instr. Meth. B158 (1999) 18-23.

[2] C.G. Ryan, D.N. Jamieson, W.L. Griffin, G. Cripps and R. Szymanski, "The New CSIRO-GEMOC Nuclear Microprobe: First Results, Performance and Recent Applications", Nucl. Instr. Meth. B181 (2001) 12-19.

[3] C.G. Ryan, D.N. Jamieson, W.L. Griffin, S.H. Sie, G. Cripps and G.F. Suter, "The new CSIRO-GEMOC Nuclear Microprobe: A new highly integrated design for geoscience applications", proc. 10th Australian Conf. on Nuclear Techniques of Analysis, Canberra, ISSN 1329-8437 (1997) NTA/VSA8.

For further information contact: Dr. Chris Ryan via email: (Chris.Ryan@csiro.au)
Phone +61-3-9905 9087
Fax orders +61-7-3327 4455
CSIRO Exploration and Mining
Bayview Road, Clayton VIC 3168
Australia
CSIRO Australia

CSIRO Exploration and Mining

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