High-Frequency Power Supplies

Figure 6 Temperature/time profiles and Curie-point temperatures for pure Ni, Fe, and Co wires (diameter 0.5 mm) when using a 1.5 kW, 1.1 MHz high frequency power supply for pyroly-sis/mass spectrometry studies. Reproduced by permission of Elsevier Science from Meuzelaar HLC, Haverkamp J and Hile-man FD (1982), Pyrolysis Mass Spectrometry of Recent and Fossil Biomaterials Compendium and Atlas. Amsterdam Elsevier Science.

EIOs), backward wave oscillators (BWOs) or magnetrons are available. Their spectral characteristics may be favourable however, they typically require highly stabilized high-voltage power supplies. Still higher frequencies may be obtained using far-infrared gas lasers pumped for example by a CO- laser [49]. 

Pulse-mode pyrolyzers include resistively-heated electrical filaments or ribbons and radio frequency induction-heated wires [841,842,846,848,849]. The filament or ribbon-type pyrolyzers are simple to construct. Figure 8.45, and typically consist of an inert wire or ribbon (Pt or Pt-Rh alloy) connected to a high-current power supply. Samples soluble in a volatile solvent are applied to the fileutent as a thin film. Insoluble materials are placed in a crucible or quartz tube, heated by a basket-lilce shaped or helical wound filiunent. The coated filament is contained within a low dead volume chamber through which the carrier gas flows, sweeping the pyrolysis products onto the column. The surface temperatui of the filament is raised rapidly from ambient temperature to He equilibrium pyrolysis temperature. This... 

Modern ESUs contain building blocks that are also found in other medical devices, such as microprocessors, power supplies, enclosures, cables, indicators, displays, and alarms. The main building blocks unique to ESUs are control input switches, the high-frequency power amplifier, and the safety monitor. 

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