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Microwave Reactor Design and Configurations
Published in Veera Gnaneswar Gude, Microwave-Mediated Biofuel Production, 2017
The magnetron consists of a cylindrical cathode surrounded by a coaxial anode (shown in Figure 1). Between these, an electric field is created by an applied direct current (dc) potential. A longitudinal magnetic field is applied by an external magnet. Thus the electric and magnetic field are perpendicular to one another. Electrons, traveling from the anode to the cathode through this field, interact to cause a net energy transfer from the applied dc voltage to the microwave field. The cavity magnetron is the most efficient of the microwave tubes. Efficiencies of 90% have been achieved and 70-80% are common. The microwave frequency is determined by the size of the magnetron: the bigger the size; the lower will be thefrequency. The microwave power is determined by the voltage of the direct current applied to magnetron. However cooling presents a practical limit for each magnetron. At 2450 MHz and 900 MHz, 20 kW and 100 kW, respectively, magnetrons are available, and 1000 kW magnetrons are available for even lower frequencies (Stein 1994, Metaxas and Meredith 1983). As magnetrons are very common, especially at 2450 MHz, they are relatively inexpensive. The frequency generated by a magnetron varies significantly compared to, e.g., a klystron. However this is of little significance for heating applications.
The next-generation consumer microwave oven: a review
Published in Journal of Microwave Power and Electromagnetic Energy, 2022
The technology that will most likely replace the cavity magnetron as a microwave source in consumer ovens is called Solid-State Radio Frequency (RF), and it uses solid-state transistors to generate microwaves. Current Solid-State RF devices heat food faster and more evenly during manufacturer demonstrations (Barry 2017; Sclocchi 2018). They are also predicted to offer an improved consumer experience (Drucker 2020). Finally, consumer systems could be more reliable and longer-lasting than current magnetron systems (RF Energy Alliance 2014; Sclocchi 2018). In addition to consumer ovens, this technology could also be used to replace automotive spark plugs, improve medical ablation devices, and develop new horticultural heating systems (RF Energy Alliance 2014; Hambling 2016; DeMartino 2017b). Table 1 summarizes the differences between magnetron and Solid-State RF consumer ovens.