The New Method to Focus Multiple Sheet Electron Beam by Periodic Cusped Magnets With Multi-Zeros-Point Bias Magnetic Field

The lack of a compact magnetic focusing system hurdles fulfilling the prominent potential of traveling wave tubes (TWTs) launched with multiple sheet electron beams (SEBs). To overcome this dilemma, this letter proposed an intriguing general method to confine multiple SEBs, which adopts novel horizontally extended periodic cusped magnets (PCM) with a multi-zero-point bias magnetic field. A new configuration with bespoke iron notches for multiple SEBs (Open PCM-NMSB) is employed to produce this unique field profile. To verify this concept, a G-band multi-SEB electron optical system (EOS) is presented, depicting that multiple paralleled SEBs can all stably propagate through the narrow tunnel without interceptions. Further investigation demonstrates that this new method can apply to EOS launched with an arbitrary number of SEBs with any preset clearance. In addition, the fabrication and measurement of this compact focusing structure are presented, experimentally confirming that the proposed Open PCM-NMSB can indeed generate the desired magnetic field, which surely facilitates the development of multi-SEB TWT or other similar vacuum electron devices.