In general, magnetrons for electronic microwave ovens generate microwaves at 2450 MHz band. In this case, a high frequency component having an integer time of the frequency of a fundamental wave component is generated with the fundamental wave component. When the high frequency component is radiated from an output unit of a magnetron, it is propagated to a heating space in the magnetron with the fundamental wave component. Because high frequency components have shorter wavelengths and are difficult to be shielded, they are sometimes leaked to the outside and occur radio interference or the like; the limit value of leakage is set by law. Therefore, conventional magnetrons are designed so that a choke groove is formed in an output unit to suppress arbitrary high frequency components by the choke groove (see for example Patent Document 1).
As such magnetrons, as an output unit 205 of a magnetron 201 shown in FIG. 8, there is a magnetron provided with a second harmonic choke groove 84, a fourth harmonic choke groove 86 and a fifth harmonic choke groove 88. In the magnetron 201, three quarter-wave type chokes corresponding to three higher harmonic waves including an exhaust pipe 21 are arranged, and suppressing a second harmonic wave (4.9 GHz) by the second harmonic choke groove 84, a fourth harmonic wave (9.8 GHz) by the fourth harmonic choke groove 86, and a fifth harmonic wave (12.25 GHz) by the fifth harmonic choke groove 88 formed by a metal sealing body 207 and a fifth harmonic choke 90. The fifth harmonic choke 90 is prepared separately from the metal sealing body 207, and is joined to the metal sealing body by a brazing material (that is, brazed).
On the other hand, as an output unit 305 of a magnetron 301 shown in FIG. 9, there is a magnetron in that the fifth harmonic choke 90 and a metal sealing body 307 of the output unit 305 are integrated to reduce the number of parts.