An emitter according to the present disclosure includes: first and second heaters generating heat by energization; an electron source comprising a first material emitting an electron by being heated by the first and second heaters; and an intermediate member interposed between the electron source, and the first and second heaters, the intermediate member comprising a second material lower in thermal conductivity than the first material.

A feedthrough device for protecting a system from an electrical transient may include a housing having a first end and a second end spaced apart from the first end in a longitudinal direction. A conductive line may extend through the housing from the first end to the second end of the housing. The conductive line may define an input end proximate the first end of the housing and an output end proximate the second end of the housing for connecting the feedthrough device with the system to be protected. A filter may be disposed within the housing and coupled with the conductive line at a first location. A gas discharge tube may be disposed within the housing and coupled with the conductive line at a second location on the conductive line that is proximate the filter and between the input end of the conductive line and the first location.

A feedthrough device for protecting a system from an electrical transient may include a housing having a first end and a second end spaced apart from the first end in a longitudinal direction. A conductive line may extend through the housing from the first end to the second end of the housing. The conductive line may define an input end proximate the first end of the housing and an output end proximate the second end of the housing for connecting the feedthrough device with the system to be protected. A filter may be disposed within the housing and coupled with the conductive line at a first location. A gas discharge tube may be disposed within the housing and coupled with the conductive line at a second location on the conductive line that is proximate the filter and between the input end of the conductive line and the first location.

In one embodiment, a system includes a thermionic emitter and a heater at least partially surrounding the thermionic emitter. The heater is configured to heat the thermionic emitter. The heater includes a first end, a second end opposite the first end, and a plurality of hollow insulating tubes that each run from the first end to the second end. The heater also includes a heater wire that runs through each of the hollow insulating tubes. The heater wire is configured to be resistively heated by an electrical current passed through the heater wire.

In one embodiment, a system includes a thermionic emitter and a heater at least partially surrounding the thermionic emitter. The heater is configured to heat the thermionic emitter. The heater includes a first end, a second end opposite the first end, and a plurality of hollow insulating tubes that each run from the first end to the second end. The heater also includes a heater wire that runs through each of the hollow insulating tubes. The heater wire is configured to be resistively heated by an electrical current passed through the heater wire.

A feedthrough device for protecting a system from an electrical transient may include a housing having a first end and a second end spaced apart from the first end in a longitudinal direction. A conductive line may extend through the housing from the first end to the second end of the housing. The conductive line may define an input end proximate the first end of the housing and an output end proximate the second end of the housing for connecting the feedthrough device with the system to be protected. A filter may be disposed within the housing and coupled with the conductive line at a first location. A gas discharge tube may be disposed within the housing and coupled with the conductive line at a second location on the conductive line that is proximate the filter and between the input end of the conductive line and the first location.

A feedthrough device for protecting a system from an electrical transient may include a housing having a first end and a second end spaced apart from the first end in a longitudinal direction. A conductive line may extend through the housing from the first end to the second end of the housing. The conductive line may define an input end proximate the first end of the housing and an output end proximate the second end of the housing for connecting the feedthrough device with the system to be protected. A filter may be disposed within the housing and coupled with the conductive line at a first location. A gas discharge tube may be disposed within the housing and coupled with the conductive line at a second location on the conductive line that is proximate the filter and between the input end of the conductive line and the first location.