Magnetrons

Figure Bl.7.18. (a) Schematic diagram of the trapping cell in an ion cyclotron resonance mass spectrometer excitation plates (E) detector plates (D) trapping plates (T). (b) The magnetron motion due to tire crossing of the magnetic and electric trapping fields is superimposed on the circular cyclotron motion aj taken up by the ions in the magnetic field. Excitation of the cyclotron frequency results in an image current being detected by the detector electrodes which can be Fourier transfonned into a secular frequency related to the m/z ratio of the trapped ion(s).

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]. 

Figure Bl.17.8. Iron oxide particles coated with 4 nm of Pt in an m-planar magnetron sputter coater (Hennann and Mtiller 1991). Micrographs were taken in a Hitachi S-900 in-lens field emission SEM at 30,000 primary magnification and an acceleration voltage of 30 kV. Image width is 2163 nm.

The most dramatic evolution of a microwave power source is that of the cooker magnetron for microwave ovens (48). These magnetrons are air-cooled, weigh 1.2 kg, generate weU over 700 W at 2.45 GHz into a matched load, and exhibit a tube efficiency on the order of 70%. AppHcation is enhanced by the avaHabiHty of comparatively inexpensive microwave power and microwave oven hardware (53). The cost of these tubes has consistently dropped (11) since their introduction in the eady 1970s. As of this writing (ca 1995), cost is < 15/tube for large quantities. For small quantities the price is < 100/tube. 

Some power tubes can be operated without the need for a protective ferrite isolator. One example is the cooker magnetron (700 W) used in modern microwave ovens (57). At higher power levels, such as 25 kW, it is more common to employ a protective ferrite device, particularly in the form of a circulator (58), as shown in Figure 3. This results in a power loss equivalent to a few percentage points in system efficiency. The ferrite circulator prevents reflected power from returning to the power tube and instead directs it into an auxiHary dummy load. The pulling of tube frequency is thus minimised. 

The price of cooker magnetrons at ca 700 W was in the range of several hundred dollars in the 1960s (11). As of the mid-1990s, this price is < 15. Total sales of microwave ovens worldwide exceed 20 x 10 /yr. The majority of homes in Japan and the United States have microwave ovens (94). European homes should foUow before the year 2000 (95). 

Food. The most successful appHcation of microwave power is that of food processing (qv), cooking, and reheating. The consumer industry surpasses all other microwave power appHcations. Essentially all microwave ovens operate at 2450 MH2 except for a few U.S. combination range models that operate at 915 MH2. The success of this appHance resulted from the development of low cost magnetrons producing over 700 W for oven powers of 500-800 W (Table 3). 

The Magnetron, Astex/Gerhng Laboratories, Inc., Modesto, Calif., July 1994. 

Fig. 3. Schematics of magnetic confinement geometries (a) planar and (b) cylindrical geometries for magnetron sputtering sources (24) (c) open-ended...

The various ultrahigh versions of the gauge, the magnetron and the inverted magnetron, for example, are accurate to within an order of magnitude. 

Fig. 10. Unbalanced magnetron vaporization source usiag an electromagnetic field.

The simplest arrangement for a linear accelerator is shown in Fig. 5. Here a single source, either a self-oscillating magnetron or klystron amplifier with appropriate drive stages, feeds power into a single length of accelerator wave-... 

The cost of the vehicle to move the accelerator, and temporary shielding, if needed, have not been included in Table 14. The vehicle houses the control console, video system, and robotic controls. A trailer would carry the main robotic system, the electronic accelerator, magnetron, and the supplies. The cost for such a vehicle and trailer is estimated at 100,000. 

The frequency of microwave radiation lies between that of IR radiation and high frequency radio waves and the boundaries between these regions are not fixed [221]. The microwaves are generated in a transmitter (magnetron) which possesses a stalk which penetrates Uke a radio antenna into a hollow energy guide (Fig. 48). This leads the electromagnetic waves into the reaction chamber (power about... 

Kato, T., Ito, T., Ishikawa, H., and Maeda, M., Magnetron-Plasma C VD System and its Applications to Aluminum Film Deposit on, Proc. Int. Conf. on Solid State Devices and Materials, Business Center for Academic Societies, Tokyo, Japan (Aug. 1986)... 

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