Provided are a slow wave circuit and a traveling wave tube suitable for an increase in fineness with regard to processing beam holes, and suitable for higher frequencies. A slow wave circuit (10) includes a meandering waveguide (1) and a beam hole (2) that pierces the meandering waveguide (1), and the cross-section of the beam hole (2) in the direction orthogonal to the long direction is in the shape of a polygon having a larger number of sides than a quadrilateral.

Provided are a slow wave circuit and a traveling wave tube suitable for an increase in fineness with regard to processing beam holes, and suitable for higher frequencies. A slow wave circuit (10) includes a meandering waveguide (1) and a beam hole (2) that pierces the meandering waveguide (1), and the cross-section of the beam hole (2) in the direction orthogonal to the long direction is in the shape of a polygon having a larger number of sides than a quadrilateral.

An electron emitter device is provided comprising a cathode comprising a conductive transition metal perovskite oxide comprising mobile conducting electrons exhibiting a conductivity of at least 10.sup.6 .sup.1-cm.sup.1 at room temperature, the transition metal perovskite oxide having a surface from which the mobile electrons are induced to emit upon receiving sufficient energy from an energy source; and an anode electrically coupled to the cathode and positioned to define an interelectrode conductive region between the anode and the cathode, onto which anode the emitted electrons are collected. The transition metal perovskite oxide may have formula Sr.sub.1-xBa.sub.xVO.sub.3. Related methods and devices based on the electron emitter device are also provided.

An electron emitter device is provided comprising a cathode comprising a conductive transition metal perovskite oxide comprising mobile conducting electrons exhibiting a conductivity of at least 10.sup.6 .sup.1-cm.sup.1 at room temperature, the transition metal perovskite oxide having a surface from which the mobile electrons are induced to emit upon receiving sufficient energy from an energy source; and an anode electrically coupled to the cathode and positioned to define an interelectrode conductive region between the anode and the cathode, onto which anode the emitted electrons are collected. The transition metal perovskite oxide may have formula Sr.sub.1-xBa.sub.xVO.sub.3. Related methods and devices based on the electron emitter device are also provided.

Provided are a traveling wave tube and a high-frequency circuit system such that the product life span of the traveling wave tube operating in multiple modes can be extended while variations in gain and amplification efficiency that accompany switching of the operation modes can be suppressed. The traveling wave tube comprises: an electron gun equipped with a cathode that releases electrons, and a heater that provides the cathode with heat energy for releasing the electrons; a helix causing an RF signal to interact with an electron beam formed from the electrons released by the electron gun; a collector for catching the electron beam emitted by the helix; an anode whereby the electrons released from the electron gun are guided into the helix; and a magnetic field application device for generating a magnetic field in order to change the diameter of the electron beam, said magnetic field application device being supplied with electric power for generating the magnetic field from the outside.

A travelling-wave tube comprising a helix joined by posts to a vacuum chamber, each post made of electrically insulating material being covered by an electrically conductive material, of electrical conductivity comprised between 1000 and 100000 S.Math.m1, over a portion of the post extending from the end of the post joined to the helix to the end of the post joined to the vacuum chamber and corresponding to a height comprised between 10% and 50% of the post.

An electron emitter device is provided comprising a cathode comprising a conductive transition metal perovskite oxide comprising mobile conducting electrons exhibiting a conductivity of at least 10.sup.6 .sup.1-cm.sup.1 at room temperature, the transition metal perovskite oxide having a surface from which the mobile electrons are induced to emit upon receiving sufficient energy from an energy source; and an anode electrically coupled to the cathode and positioned to define an interelectrode conductive region between the anode and the cathode, onto which anode the emitted electrons are collected. The transition metal perovskite oxide may have formula Sr.sub.1-xBa.sub.xVO.sub.3. Related methods and devices based on the electron emitter device are also provided.

An electron emitter device is provided comprising a cathode comprising a conductive transition metal perovskite oxide comprising mobile conducting electrons exhibiting a conductivity of at least 10.sup.6 .sup.1-cm.sup.1 at room temperature, the transition metal perovskite oxide having a surface from which the mobile electrons are induced to emit upon receiving sufficient energy from an energy source; and an anode electrically coupled to the cathode and positioned to define an interelectrode conductive region between the anode and the cathode, onto which anode the emitted electrons are collected. The transition metal perovskite oxide may have formula Sr.sub.1-xBa.sub.xVO.sub.3. Related methods and devices based on the electron emitter device are also provided.

Provided are a traveling wave tube and a high-frequency circuit system such that the product life span of the traveling wave tube operating in multiple modes can be extended while variations in gain and amplification efficiency that accompany switching of the operation modes can be suppressed. The traveling wave tube comprises: an electron gun equipped with a cathode that releases electrons, and a heater that provides the cathode with heat energy for releasing the electrons; a helix causing an RF signal to interact with an electron beam formed from the electrons released by the electron gun; a collector for catching the electron beam emitted by the helix; an anode whereby the electrons released from the electron gun are guided into the helix; and a magnetic field application device for generating a magnetic field in order to change the diameter of the electron beam, said magnetic field application device being supplied with electric power for generating the magnetic field from the outside.