An x-ray tube having at least one focusing cup and an anode. The x-ray tube may have a first filament positioned in a first location between the focusing cup and the anode, the first filament having a first size, and a second filament positioned in a second location between the focusing cup and anode, the second filament having a second size that is substantially the same as the first size. The x-ray tube may also include a switching mechanism configured to engage the second filament upon failure of the first filament.