Many users of Cathodoluminescence petrography often wish to sample regions of interest for various geochemical analyses (for example, stable isotopes or trace elements). Relion has developed a versatile micro-sampling apparatus, building on the work of Fouke, B.W. and J. Rakovan, 2001.
Microsampling may be done with either Microdrilling or Micromilling techniques.
In Microdrilling, the sample is stationary and the drill cutter is moved around the sample on the desired areas. The live video image of the sample under the microscope showing the drill point is overlaid in software over a CL image (or other) to help identify features of interest.
With Micromilling, the milling cutter is rigidly held in a fixed vertical position and the sample is moved on a computer-controlled X,Y stage to move the desired areas against the milling cutter. The areas may be preselected or the operator may use a type of joy-stick to control the sample position.
In both cases, a vacuum-operated micropipette is used to collect the powdered material generated by the drilling or milling on a filter.
We are currently exploring micro-core drilling and "spallation" (production of chips as opposed to powder) techniques.
Each system is built to order, customized to the user's requirements, but each system typically incorporates the following major components :
A stereo microscope with appropriate illumination systems and a digital video camera, connected to a computer with appropriate imaging software
A heavy steel base plate, to which the microscope is securely mounted
A micromotor handpiece (the drill) mounted to a 3-axis micropositioner attached to the end of an adjustable arm secured to the base plate with a switchable magnet. The micromotor will have a separate power supply unit, equipped with a foot switch for activation.
A collection system consisting of a micropipette tip, filter assembly, and vacuum tubing, also attached to the end of adjustable arm (with or without a 3-axis micropositioner) secured to the base plate with a switchable magnet. The vacuum tubing is connected to a small laboratory vacuum pump.
Often the microscope will be fitted with a manual XY stage, equipped with several options (mounting plates) for securing your samples to the stage, to facilitate positioning the sample area of interest under the microscope and the drill.
The microdrill can be converted to a micromill by attaching the micromotor handpiece on a rigid vertical mounting accessory. Automating the XY stage makes this a two-axis CNC mill...
