Incremental Heating

Incremental heating of metal encapsulated samples to produce age spectra is totally automated and acheived using a diode laser controlled by either setting the diode current directly or external modulation via output from an optical pyrometer or thermocouple.  Temperature is calibrated from measurements of the melting point of Al foil and the Arrhenius properties of kalsilite glass.  Samples are either single crystals enclosed in 1 mm Nb capsules or grain aggregates up to 2 milligram that are contained within 3 mm Ta foil packets.  Individual samples are either placed in a 21 well or 45 well stainless tray or suspended on thermocouples from one of 7 available ports of a spherical octagon.  The user specifies the well numbers (or thermocouple port) to be analyzed as well as heating schedules and gettering times that are apropriate for each sample.  Typical heating steps are 3-5 minutes in duration with additional time specified for gettering.  The sample gas is analyzed by the Noblesse mass spectrometer.  A typical analysis last 5 minutes with additional time required for post analysis peak centering and baseline measurement.  It takes about 4 hours to perform a 16-step sequence (typical for micas) or about 10 hours for a 40 step sequence (typical for K-feldspar).  Blanks are interspersed as dictated by the user.  Detector intercalibration is performed at least once daily. A fully loaded sample tray requires several days to a week to complete.  Management of the analysis session is routinely handled remotely.