Um sistema nacional de aquisição e processamento de dados acoplado "on line" ao espectrômetro de massa de fonte sólida TH-5 (Varian Mat)

Abstract

A VARIAN MAT solid source mass spectrometer, varían model MAT TH-5, used for geochronological applications has been coupled on line to a 16-bit HP-9825B computer. An appropriate digital voltimeter and interface, both supplied by Hewlett-Packard, complete the system. The developed prototype allows, through peak switching of 8 channels controlled by a Hall effect probe, isotopic analyses of all the elements which can be carried out by the thermal ionization method. This system has been used since 1983 with success, and the strontium measurements performed on 2 carbonate standards NBS-987 and SrN (E&A) agree, within experimental error, with results obtained in modem instruments. A similar system, with the same performance capabilities as the one described above, using an Apple computer and peripherals available in Brazil, has also been developed. The developed interface is provided with outputs to control external devices and accessories like solenoid valves, vacuum systems, scales, etc, common is mass spectrometry. The software, available in HPL and Applesoft languages, is provided with dinamic interference correction, Dodson's interpolation technique, rejection of the spurious ratios and computes all the common statistical parameters.