The ion trap comprises a multipole electrode assembly, a first confining electrode, and a second confining electrode. The multipole electrode assembly is configured to confine ions of the first polarity to an ion channel extending in an axial direction of the multipole electrode assembly. The first confining electrode is provided adjacent to the multipole electrode assembly and extends in the axial direction of the multipole electrode assembly. The second confining electrode is provided adjacent to the multipole electrode assembly and extends in the axial direction of the multipole electrode assembly aligned with the first confining electrode. The first and second confining electrodes are spaced apart in the axial direction in order to define an ion confining region of the ion channel between the first and second confining electrodes. The first and second confining electrodes are configured to receive a DC potential of the first polarity to further confine ions within the ion channel in the ion confining region.

Disclosed is an electron beam emission device comprising a housing which defines a space in which electron beams are accelerated, and has an opening at the other side thereof through which the electron beams are emitted; a cathode which is disposed at one side in the housing, and emits the electrons; an anode which is positioned in the housing so as to be spaced apart from the cathode toward the other side, and accelerates the electrons emitted from the cathode; and an insulation holder which insulates a portion between the cathode and the housing, and fixes the cathode, wherein the cathode has a surface which faces the anode and is formed concavely to have a gradient, and a rim of the surface of the cathode, which has the gradient, is formed to be rounded.

Disclosed is an electron beam emission device comprising a housing which defines a space in which electron beams are accelerated, and has an opening at the other side thereof through which the electron beams are emitted; a cathode which is disposed at one side in the housing, and emits the electrons; an anode which is positioned in the housing so as to be spaced apart from the cathode toward the other side, and accelerates the electrons emitted from the cathode; and an insulation holder which insulates a portion between the cathode and the housing, and fixes the cathode, wherein the cathode has a surface which faces the anode and is formed concavely to have a gradient, and a rim of the surface of the cathode, which has the gradient, is formed to be rounded.