Plasma source, and atomic clock employing plasma source

A plasma source comprising:

• a first magnet;
• a second magnet arranged so that a second magnetic pole different from a first magnetic pole faces the first magnetic pole of the first magnet;
• a third magnet having the second magnetic pole different from the first magnetic pole directed in the same direction as the first magnetic pole of the first magnet and arranged to surround the first magnet;
• a fourth magnet having the first magnetic pole different from the second magnetic pole facing the second magnetic pole of the third magnet and arranged to surround the second magnet;
• a first electrode provided on sides of the first magnetic pole of the first magnet and the second magnetic pole of the third magnet;
• a second electrode facing the first electrode and provided on sides of the second magnetic pole of the second magnet and the first magnetic pole of the fourth magnet;
• and
• a third electrode arranged between the first electrode and the second electrode so that a voltage having a higher potential than those of the first electrode and the second electrode is applied thereto,
• wherein a maximum magnetic field strength |By(max)| of a first direction from the second magnet to the first magnet in a first space between the first magnet and the second magnet and a second space between the third magnet and the fourth magnet and a minimum magnetic field strength |By(min)| of the first direction satisfy |By(min)|/|By(max)|≥0.1, and
• wherein a maximum magnetic field strength |Bx(max)| of a second direction orthogonal to the first direction in a third space sandwiched between the first space and the second space and a minimum magnetic field strength |Bx(min)| of the second direction satisfy |Bx(min)/|Bx(max)| ≤0.1.